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Sample records for superconducting properties pressure

  1. High-Pressure Structures of Disilane and Their Superconducting Properties

    Science.gov (United States)

    Flores-Livas, José A.; Amsler, Maximilian; Lenosky, Thomas J.; Lehtovaara, Lauri; Botti, Silvana; Marques, Miguel A. L.; Goedecker, Stefan

    2012-03-01

    A systematic ab initio search for low-enthalpy phases of disilane (Si2H6) at high pressures was performed based on the minima hopping method. We found a novel metallic phase of disilane with Cmcm symmetry, which is enthalpically more favorable than the recently proposed structures of disilane up to 280 GPa, but revealing compositional instability below 190 GPa. The Cmcm phase has a moderate electron-phonon coupling yielding a superconducting transition temperature Tc of around 20 K at 100 GPa, decreasing to 13 K at 220 GPa. These values are significantly smaller than previously predicted Tc’s for disilane at equivalent pressure. This shows that similar but different crystalline structures of a material can result in dramatically different Tc’s and stresses the need for a systematic search for a crystalline ground state.

  2. Superconducting Properties of MgB2 Prepared by High and Ambient Pressures

    Institute of Scientific and Technical Information of China (English)

    REN Zhi-An; CHE Guang-Can; ZHAO Zhong-Xian; CHEN Hong; DONG Cheng; NI Yong-Ming; JIA Shun-Lian; WEN Hai-Hu

    2001-01-01

    The new superconductor MgB2 has been prepared in two ways, by high pressure and ambient pressure synthesis.The superconducting properties were measured and compared. It is found that the sample prepared by highpressure is much denser than that prepared under ambient pressure. Accordingly the high pressure sample has avery narrow transition width and a much higher bulk critical current densityC

  3. Influence of hydrostatic pressure on superconducting properties of niobium thin film

    Energy Technology Data Exchange (ETDEWEB)

    Pristáš, Gabriel; Gabáni, Slavomír; Gažo, Emil [Centre of Low Temperature Physics, Institute of Experimental Physics, Slovak Academy of Sciences, Watsonova 47, 040 01 Košice (Slovakia); Komanický, Vladimír; Orendáč, Matúš [Centre of Low Temperature Physics, Faculty of Science, P. J. Šafárik University, Park Angelinum 9, SK-04154 Košice (Slovakia); You, Hoydoo [Materials Science Division, Argonne National Laboratory, Argonne, IL 60439 (United States)

    2014-04-01

    We have studied superconducting properties of niobium thin films under hydrostatic pressures up to 3 GPa. The films with thickness of 100 nm were prepared in the high vacuum DC magnetron sputtering system (with critical temperature TC = 8.95 K at ambient pressure). The produced high quality films have been characterized using electrical resistivity and magnetization measurements, X-ray diffraction, and atomic force microscope imaging. We have observed increase of TC with increasing value of applied pressure (dTC/dp = 73 mK/GPa) up to 3 GPa. This observation is different to pressure effect observed on bulk sample of Nb. In this paper we are discussing the origin of this discrepancy. - Highlights: • We have studied superconducting properties of niobium thin films under pressure. • The 100 nm thick films were prepared in DC magnetron sputtering system. • We have observed different behavior of T{sub C} for thin film and for bulk sample.

  4. Superconducting properties of La{sub 2-x}Ba{sub 2}CuO{sub 4} under pressure

    Energy Technology Data Exchange (ETDEWEB)

    Schottenhamel, Wolf; Wolter-Giraud, Anja; Buechner, Bernd [Leibniz Institute for Solid State and Materials Research Dresden, IFW Dresden (Germany); Huecker, Markus [Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY (United States)

    2016-07-01

    La{sub 2-x}Ba{sub 2}CuO{sub 4} displays an anomalous doping dependence associated with a deep suppression of superconductivity at the hole concentration x=1/8. The so-called 1/8-anomaly is accompanied by a structural transition in the average rotational symmetry of the CuO{sub 2} planes coinciding with the onset of a charge stripe order. It has been claimed that static stripe order destroys the superconducting phase coherence, while dynamic stripe correlations may promote superconductivity. In order to achieve more information about the relationship between superconductivity, stripe order and crystal structure we performed magnetization measurements under pressure up to 3 GPa on the single crystalline La{sub 2-x}Ba{sub 2}CuO{sub 4} with 0.095 ≤ x ≤ 0.125. Moreover, we relate the magnetization data to pressure dependent X-Ray diffraction studies. This way, we show that the specific superconducting properties as function of pressure are clearly correlated to structural changes.

  5. Superconducting and normal state properties of heavily hole-doped diamond synthesized at high pressure

    Directory of Open Access Journals (Sweden)

    V.A. Sidorov, E.A. Ekimov, A.V. Rakhmanina, S.M. Stishov, E.D. Bauer and J.D. Thompson

    2006-01-01

    Full Text Available Diamonds, synthesized at high pressures and high temperatures in the presence of boron, are heavily hole-doped by incorporation of boron into the diamond lattice. These diamonds become superconducting below Tc=2–9 K. Synthesis in the systems B-C and B4C-C at P=9 GPa and T=2500–2800 K result in formation of polycrystalline carbonado-like material, whereas synthesis from B-C-H gives small single crystals and intergrowth plates. Dense superconducting bodies can be prepared by compacting these single crystal particles at P=8 GPa and T=1800 K. Specific heat and resistivity measurements in magnetic fields prove the bulk nature of superconductivity in all pressure-synthesized samples and provide a consistent set of materials parameters that favor a conventional weak-coupling electron–phonon interpretation of the superconducting mechanism at high hole doping. Schottky barrier tunneling conductance spectra, obtained with contacts fabricated at the surface of these hole-doped diamonds, indicate the appearance of superconducting gap below Tc.

  6. Hydrostatic pressure effect on the superconducting properties of BaBi3 and SrBi3 single crystals

    Science.gov (United States)

    Jha, Rajveer; Avila, Marcos A.; Ribeiro, Raquel A.

    2017-02-01

    We demonstrate the superconducting properties of, and hydrostatic pressure effect on, BaBi3 and SrBi3 superconductors. We measure the dc magnetic susceptibility under hydrostatic pressure for both compounds, which shows a positive pressure coefficient of dT c/dP = 1.22 K GPa-1 for BaBi3 and a negative pressure coefficient of dT c/dP = -0.43 K GPa-1 for SrBi3. The normal state electrical resistivity shows that both compounds are highly metallic in nature. The upper critical fields H c2 evaluated by resistivity under magnetic fields ρ(T,H) are 22 kOe for BaBi3 and 2.9 kOe for SrBi3. A specific heat jump of ΔC e/γT c = 1.05 suggests weak coupling superconductivity in BaBi3, whereas ΔC e/γT c = 2.08 for SrBi3 is higher than the Bardeen-Cooper-Schrieffer theory value of 1.43, indicating a strong coupling superconductor.

  7. Magnetic and Superconducting Materials at High Pressures

    Energy Technology Data Exchange (ETDEWEB)

    Struzhkin, Viktor V. [Carnegie Inst. of Washington, Washington, DC (United States)

    2015-03-24

    The work concentrates on few important tasks in enabling techniques for search of superconducting compressed hydrogen compounds and pure hydrogen, investigation of mechanisms of high-Tc superconductivity, and exploring new superconducting materials. Along that route we performed several challenging tasks, including discovery of new forms of polyhydrides of alkali metal Na at very high pressures. These experiments help us to establish the experimental environment that will provide important information on the high-pressure properties of hydrogen-rich compounds. Our recent progress in RIXS measurements opens a whole field of strongly correlated 3d materials. We have developed a systematic approach to measure major electronic parameters, like Hubbard energy U, and charge transfer energy Δ, as function of pressure. This technique will enable also RIXS studies of magnetic excitations in iridates and other 5d materials at the L edge, which attract a lot of interest recently. We have developed new magnetic sensing technique based on optically detected magnetic resonance from NV centers in diamond. The technique can be applied to study superconductivity in high-TC materials, to search for magnetic transitions in strongly correlated and itinerant magnetic materials under pressure. Summary of Project Activities; development of high-pressure experimentation platform for exploration of new potential superconductors, metal polyhydrides (including newly discovered alkali metal polyhydrides), and already known superconductors at the limit of static high-pressure techniques; investigation of special classes of superconducting compounds (high-Tc superconductors, new superconducting materials), that may provide new fundamental knowledge and may prove important for application as high-temperature/high-critical parameter superconductors; investigation of the pressure dependence of superconductivity and magnetic/phase transformations in 3d transition metal compounds, including

  8. High-Pressure Study of the Ground- and Superconducting-State Properties of CeAu2Si2

    Science.gov (United States)

    Scheerer, Gernot W.; Giriat, Gaétan; Ren, Zhi; Lapertot, Gérard; Jaccard, Didier

    2017-06-01

    The pressure-temperature phase diagram of the new heavy-fermion superconductor CeAu2Si2 is markedly different from those studied previously. Indeed, superconductivity emerges not on the verge but deep inside the magnetic phase, and mysteriously Tc increases with the strengthening of magnetism. In this context, we have carried out ac calorimetry, resistivity, and thermoelectric power measurements on a CeAu2Si2 single crystal under high pressure. We uncover a strong link between the enhancement of superconductivity and quantum-critical-like features in the normal-state resistivity. Non-Fermi-liquid behavior is observed around the maximum of superconductivity and enhanced scattering rates are observed close to both the emergence and the maximum of superconductivity. Furthermore we observe signatures of pressure- and temperature-driven modifications of the magnetic structure inside the antiferromagnetic phase. A comparison of the features of CeAu2Si2 and its parent compounds CeCu2Si2 and CeCu2Ge2 plotted as function of the unit-cell volume leads us to propose that critical fluctuations of a valence crossover play a crucial role in the superconducting pairing mechanism. Our study illustrates the complex interplay between magnetism, valence fluctuations, and superconductivity.

  9. Effect of Pressure on Magneto-Transport Properties in the Superconducting and Normal Phases of the Metallic Double Chain Compound Pr2Ba4Cu7O15-δ

    Science.gov (United States)

    Kuwabara, Masayoshi; Matsukawa, Michiaki; Sugawara, Keisuke; Taniguchi, Haruka; Matsushita, Akiyuki; Hagiwara, Makoto; Sano, Kazuhiro; Ōno, Yoshiaki; Sasaki, Takahiko

    2016-12-01

    To examine the electronic phase diagram of superconducting CuO double chains, we report the effect of external pressure on the magneto-transport properties in superconducting and non-superconducting polycrystalline samples of Pr2Ba4Cu7O15-δ at low temperatures (1.8-40 K) under various magnetic fields (up to 14 T). In the as-sintered non-superconducting sample, the magneto-resistance (MR) follows a power law of H3/2 at low temperatures, which is in no agreement with the H2 dependence of MR in the PrBa2Cu4O8 system. The negative pressure dependence of the superconducting phase is qualitatively consistent with a theoretical prediction on the basis of the Tomonaga-Luttinger liquid theory. The 48-h-reduced superconducting sample at ambient pressure exhibits no clear increase in MR for T > Tc,on = 26.5 K. In contrast, with the application of pressure to the superconducting sample, the MR effects reappear and are also well fitted by H3/2. The model of slightly warped Fermi surfaces explains not only the MR effect of the non-superconducting sample, but is also related to the reasons for the pressure-induced MR phenomena of the superconducting sample.

  10. Superconductivity from insulating elements under high pressure

    Energy Technology Data Exchange (ETDEWEB)

    Shimizu, Katsuya

    2015-07-15

    Highlights: • Even insulating molecule can become metal and superconductor by pressure with relatively high T{sub c}. • The highest T{sub c} is observed in sulfur with 17 K at 160 GPa. • Hydrogen is the best candidate of the highest T{sub c} element. - Abstract: The insulating and superconducting states would seem to have very different characteristics. Can any insulator become a superconductor? One proven method, doping an insulating material with carriers, can create itinerant states inside the gap between the conduction and valence bands. Another method is to squeeze the structure by applying pressure. Pressure can expand the bandwidth and also narrow the energy band gap. So the first step to turn an insulator into a superconductor is to make it metallic. Here we review our experimental research and results on superconductivity induced by applying pressure to insulating molecular systems such as elemental molecules.

  11. Pressure-driven dome-shaped superconductivity and electronic structural evolution in tungsten ditelluride.

    Science.gov (United States)

    Pan, Xing-Chen; Chen, Xuliang; Liu, Huimei; Feng, Yanqing; Wei, Zhongxia; Zhou, Yonghui; Chi, Zhenhua; Pi, Li; Yen, Fei; Song, Fengqi; Wan, Xiangang; Yang, Zhaorong; Wang, Baigeng; Wang, Guanghou; Zhang, Yuheng

    2015-07-23

    Tungsten ditelluride has attracted intense research interest due to the recent discovery of its large unsaturated magnetoresistance up to 60 T. Motivated by the presence of a small, sensitive Fermi surface of 5d electronic orbitals, we boost the electronic properties by applying a high pressure, and introduce superconductivity successfully. Superconductivity sharply appears at a pressure of 2.5 GPa, rapidly reaching a maximum critical temperature (Tc) of 7 K at around 16.8 GPa, followed by a monotonic decrease in Tc with increasing pressure, thereby exhibiting the typical dome-shaped superconducting phase. From theoretical calculations, we interpret the low-pressure region of the superconducting dome to an enrichment of the density of states at the Fermi level and attribute the high-pressure decrease in Tc to possible structural instability. Thus, tungsten ditelluride may provide a new platform for our understanding of superconductivity phenomena in transition metal dichalcogenides.

  12. High-pressure behavior of superconducting boron-doped diamond

    Science.gov (United States)

    Abdel-Hafiez, Mahmoud; Kumar, Dinesh; Thiyagarajan, R.; Zhang, Q.; Howie, R. T.; Sethupathi, K.; Volkova, O.; Vasiliev, A.; Yang, W.; Mao, H. K.; Rao, M. S. Ramachandra

    2017-05-01

    This work investigates the high-pressure structure of freestanding superconducting (Tc=4.3 K) boron-doped diamond (BDD) and how it affects the electronic and vibrational properties using Raman spectroscopy and x-ray diffraction in the 0-30 GPa range. High-pressure Raman scattering experiments revealed an abrupt change in the linear pressure coefficients, and the grain boundary components undergo an irreversible phase change at 14 GPa. We show that the blueshift in the pressure-dependent vibrational modes correlates with the negative pressure coefficient of Tc in BDD. The analysis of x-ray diffraction data determines the equation of state of the BDD film, revealing a high bulk modulus of B0=510 ±28 GPa. The comparative analysis of high-pressure data clarified that the s p2 carbons in the grain boundaries transform into hexagonal diamond.

  13. Pressure-driven dome-shaped superconductivity and electronic structural evolution in tungsten ditelluride

    National Research Council Canada - National Science Library

    Pan, Xing-Chen; Chen, Xuliang; Liu, Huimei; Feng, Yanqing; Wei, Zhongxia; Zhou, Yonghui; Chi, Zhenhua; Pi, Li; Yen, Fei; Song, Fengqi; Wan, Xiangang; Yang, Zhaorong; Wang, Baigeng; Wang, Guanghou; Zhang, Yuheng

    2015-01-01

    ... T. Motivated by the presence of a small, sensitive Fermi surface of 5d electronic orbitals, we boost the electronic properties by applying a high pressure, and introduce superconductivity successfully...

  14. Superconductivity

    CERN Document Server

    Poole, Charles P; Farach, Horacio A

    1995-01-01

    Superconductivity covers the nature of the phenomenon of superconductivity. The book discusses the fundamental principles of superconductivity; the essential features of the superconducting state-the phenomena of zero resistance and perfect diamagnetism; and the properties of the various classes of superconductors, including the organics, the buckministerfullerenes, and the precursors to the cuprates. The text also describes superconductivity from the viewpoint of thermodynamics and provides expressions for the free energy; the Ginzburg-Landau and BCS theories; and the structures of the high

  15. High-pressure superconducting state in hydrogen

    Science.gov (United States)

    Duda, A. M.; Szczȩśniak, R.; Sowińska, M. A.; Kosiacka, A. H.

    2016-10-01

    The paper determines the thermodynamic parameters of the superconducting state in the metallic atomic hydrogen under the pressure at 1 TPa, 1.5 TPa, and 2.5 TPa. The calculations were conducted in the framework of the Eliashberg formalism. It has been shown that the critical temperature is very high (in the range from 301.2 K to 437.3 K), as well as high are the values of the electron effective mass (from 3.43me to 6.88me), where me denotes the electron band mass. The ratio of the low-temperature energy gap to the critical temperature explicitly violates the predictions of the BCS theory: 2 Δ (0) /kB TC ∈ . Additionally, the free energy difference between the superconducting and normal state, the thermodynamic critical field, and the specific heat of the superconducting state have been determined. Due to the significant strong-coupling and retardation effects those quantities cannot be correctly described in the framework of the BCS theory.

  16. Effects of drawing and high-pressure sintering on the superconducting properties of (Ba,K)Fe2As2 powder-in-tube wires

    Science.gov (United States)

    Pyon, Sunseng; Yamasaki, Yuji; Kajitani, Hideki; Koizumi, Norikiyo; Tsuchiya, Yuji; Awaji, Satoshi; Watanabe, Kazuo; Tamegai, Tsuyoshi

    2015-12-01

    The evolution of the superconducting properties of round wires of (Ba,K)Fe2As2 fabricated by the powder-in-tube (PIT) method is systematically studied. After establishing the method to obtain the largest transport critical current density (J c) in round wires using the hot isostatic press technique, we investigated how the transition temperature (T c), J c, and microstructures change at each step of the wire fabrication. Unexpectedly, we find that superconducting properties of the wire core are significantly damaged by the drawing process. Systematic measurements of J c and T c of the core superconductor after each drawing and sintering process clarified the evolution of degradation by the drawing process and recovery by heat treatment.

  17. Effect of shock pressure on the structure and superconducting properties of Y-Ba-Cu-O in explosively fabricated bulk metal-matrix composites

    Science.gov (United States)

    Murr, L. E.; Niou, C. S.; Pradhan-Advani, M.

    1991-01-01

    While it is now well established that copper-oxide-based power, or virtually any other ceramic superconductor powder, can be consolidated and encapsulated within a metal matrix by explosive consolidation, the erratic superconductivity following fabrication has posed a major problem for bulk applications. The nature of this behavior was found to arise from microstructural damage created in the shock wave front, and the residual degradation in superconductivity was demonstrated to be directly related to the peak shock pressure. The explosively fabricated or shock loaded YBa2Cu3Ox examples exhibit drastically altered rho (or R) - T curves. The deterioration in superconductivity is even more noticeable in the measurement of ac magnetic susceptibility and flux exclusion or shielding fraction which is also reduced in proportion to increasing peak shock pressure. The high frequency surface resistance (in the GHz range) is also correspondingly compromised in explosively fabricated, bulk metal-matrix composites based on YBa2Cu3O7. Transmission electron microscopy (including lattice imaging techniques) is being applied in an effort to elucidate the fundamental (microstructural) nature of the shock-induced degradation of superconductivity and normal state conductivity. One focus of TEM observations has assumed that oxygen displaced from b-chains rather than oxygen-vacancy disorder in the basal plane of oxygen deficient YBa2Cu3Ox may be a prime mechanism. Shock-wave displaced oxygen may also be locked into new positions or interstitial clusters or chemically bound to displaced metal (possibly copper) atoms to form precipitates, or such displacements may cause the equivalent of local lattice cell changes as a result of stoichiometric changes. While the shock-induced suppression of T(sub c) is not desirable in the explosive fabrication of bulk metal-matrix superconductors, it may be turned into an advantage if the atomic-scale distortion can be understood and controlled as local

  18. The crystal structure and superconducting properties of monatomic bromine.

    Science.gov (United States)

    Duan, Defang; Meng, Xing; Tian, Fubo; Chen, Changbo; Wang, Liancheng; Ma, Yanming; Cui, Tian; Liu, Bingbing; He, Zhi; Zou, Guangtian

    2010-01-13

    The crystal structure and superconducting properties of monatomic bromine under high pressure have been studied by first-principles calculations. We have found the following phase transition sequence with increasing pressure: from body-centered orthorhombic (bco, phase II) to body-centered tetragonal structure (bct, phase III) at 126 GPa, then to face-centered cubic structure (fcc, phase IV) at 157 GPa, which is stable at least up to 300 GPa. The calculated superconducting critical temperature T(c) = 1.46 K at 100 GPa is consistent with the experimental value of 1.5 K. In addition, our results of T(c) decrease with increasing pressure in all the monatomic phases of bromine, similar to monatomic iodine. Further calculations show that the decrease of λ with pressure in phase IV is mainly attributed to the weakening of the 'soft' vibrational mode caused by pressure.

  19. Pressure-induced superconductivity in CaLi(2).

    Science.gov (United States)

    Matsuoka, T; Debessai, M; Hamlin, J J; Gangopadhyay, A K; Schilling, J S; Shimizu, K

    2008-05-16

    A search for superconductivity has been carried out on the hexagonal polymorph of Laves-phase CaLi(2), a compound for which Feng, Ashcroft, and Hoffmann predict highly anomalous behavior under pressure. No superconductivity is observed above 1.10 K at ambient pressure. However, high-pressure ac susceptibility and electrical resistivity studies to 81 GPa reveal bulk superconductivity in CaLi(2) at temperatures as high as 13 K. The normal-state resistivity displays a dramatic increase with pressure.

  20. Superconductivity in topological insulator Sb2Te3 induced by pressure.

    Science.gov (United States)

    Zhu, J; Zhang, J L; Kong, P P; Zhang, S J; Yu, X H; Zhu, J L; Liu, Q Q; Li, X; Yu, R C; Ahuja, R; Yang, W G; Shen, G Y; Mao, H K; Weng, H M; Dai, X; Fang, Z; Zhao, Y S; Jin, C Q

    2013-01-01

    Topological superconductivity is one of most fascinating properties of topological quantum matters that was theoretically proposed and can support Majorana Fermions at the edge state. Superconductivity was previously realized in a Cu-intercalated Bi2Se3 topological compound or a Bi2Te3 topological compound at high pressure. Here we report the discovery of superconductivity in the topological compound Sb2Te3 when pressure was applied. The crystal structure analysis results reveal that superconductivity at a low-pressure range occurs at the ambient phase. The Hall coefficient measurements indicate the change of p-type carriers at a low-pressure range within the ambient phase, into n-type at higher pressures, showing intimate relation to superconducting transition temperature. The first principle calculations based on experimental measurements of the crystal lattice show that Sb2Te3 retains its Dirac surface states within the low-pressure ambient phase where superconductivity was observed, which indicates a strong relationship between superconductivity and topology nature.

  1. First-principles study of superconducting hydrogen sulfide at pressure up to 500 GPa.

    Science.gov (United States)

    Durajski, Artur P; Szczęśniak, Radosław

    2017-06-30

    We investigate the possibility of achieving the room-temperature superconductivity in hydrogen sulfide (H3S) through increasing external pressure, a path previously widely used to reach metallization and superconducting state in novel hydrogen-rich materials. The electronic properties and superconductivity of H3S in the pressure range of 250-500 GPa are determined by the first-principles calculations. The metallic character of a body-centered cubic Im[Formula: see text]m structure is found over the whole studied pressure. Moreover, the absence of imaginary frequency in phonon spectrum implies that this structure is dynamically stable. Furthermore, our calculations conducted within the framework of the Eliashberg formalism indicate that H3S in the range of the extremely high pressures is a conventional strong-coupling superconductor with a high superconducting critical temperature, however, the maximum critical temperature does not exceed the value of 203 K.

  2. Pressure-induced isostructural phase transition and correlation of FeAs coordination with the superconducting properties of 111-type Na(1-x)FeAs.

    Science.gov (United States)

    Liu, Qingqing; Yu, Xiaohui; Wang, Xiancheng; Deng, Zheng; Lv, Yuxi; Zhu, Jinlong; Zhang, Sijia; Liu, Haozhe; Yang, Wenge; Wang, Lin; Mao, Hokwang; Shen, Guoyin; Lu, Zhong-Yi; Ren, Yang; Chen, Zhiqiang; Lin, Zhijun; Zhao, Yusheng; Jin, Changqing

    2011-05-25

    The effect of pressure on the crystalline structure and superconducting transition temperature (T(c)) of the 111-type Na(1-x)FeAs system using in situ high-pressure synchrotron X-ray powder diffraction and diamond anvil cell techniques is studied. A pressure-induced tetragonal to tetragonal isostructural phase transition was found. The systematic evolution of the FeAs(4) tetrahedron as a function of pressure based on Rietveld refinements on the powder X-ray diffraction patterns was obtained. The nonmonotonic T(c)(P) behavior of Na(1-x)FeAs is found to correlate with the anomalies of the distance between the anion (As) and the iron layer as well as the bond angle of As-Fe-As for the two tetragonal phases. This behavior provides the key structural information in understanding the origin of the pressure dependence of T(c) for 111-type iron pnictide superconductors. A pressure-induced structural phase transition is also observed at 20 GPa.

  3. Pressure-induced superconductivity in the giant Rashba system BiTeI

    Science.gov (United States)

    VanGennep, D.; Linscheid, A.; Jackson, D. E.; Weir, S. T.; Vohra, Y. K.; Berger, H.; Stewart, G. R.; Hennig, R. G.; Hirschfeld, P. J.; Hamlin, J. J.

    2017-03-01

    At ambient pressure, BiTeI exhibits a giant Rashba splitting of the bulk electronic bands. At low pressures, BiTeI undergoes a transition from trivial insulator to topological insulator. At still higher pressures, two structural transitions are known to occur. We have carried out a series of electrical resistivity and AC magnetic susceptibility measurements on BiTeI at pressure up to  ∼40 GPa in an effort to characterize the properties of the high-pressure phases. A previous calculation found that the high-pressure orthorhombic P4/nmm structure BiTeI is a metal. We find that this structure is superconducting with T c values as high as 6 K. AC magnetic susceptibility measurements support the bulk nature of the superconductivity. Using electronic structure and phonon calculations, we compute T c and find that our data is consistent with phonon-mediated superconductivity.

  4. Superconductivity

    CERN Document Server

    Thomas, D B

    1974-01-01

    A short general review is presented of the progress made in applied superconductivity as a result of work performed in connection with the high-energy physics program in Europe. The phenomenon of superconductivity and properties of superconductors of Types I and II are outlined. The main body of the paper deals with the development of niobium-titanium superconducting magnets and of radio-frequency superconducting cavities and accelerating structures. Examples of applications in and for high-energy physics experiments are given, including the large superconducting magnet for the Big European Bubble Chamber, prototype synchrotron magnets for the Super Proton Synchrotron, superconducting d.c. beam line magnets, and superconducting RF cavities for use in various laboratories. (0 refs).

  5. Superconductivity in GeH{sub 4}(H{sub 2}){sub 2} above 220 GPa high-pressure

    Energy Technology Data Exchange (ETDEWEB)

    Zhong Guohua, E-mail: gh.zhong@siat.ac.cn [Center for Photovoltaics and Solar Energy, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences and Chinese University of Hong Kong, Shenzhen 518055 (China); Zhang Chao [Department of Physics, Yantai University, Yantai 264003 (China); Wu Guangfen; Song Jianjun; Liu Zhuang [Center for Photovoltaics and Solar Energy, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences and Chinese University of Hong Kong, Shenzhen 518055 (China); Yang Chunlei, E-mail: cl.yang@siat.ac.cn [Center for Photovoltaics and Solar Energy, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences and Chinese University of Hong Kong, Shenzhen 518055 (China)

    2013-02-01

    Hydrogen-rich materials have fascinating physical and chemical properties such as various structures and superconductivity under high-pressure. They are believed as an alternative approach to realize the hydrogen superconducting. In the previous report ([17] Zhong et al., J. Phys. Chem. C 116 (2012) 5225), we had presented structural phase-transitions and bonding interaction variations induced by pressure, and predicted a stable and superconductive phase above 220 GPa, P2{sub 1}/c. In this study, we focus on the change of superconducting transition temperature induced by pressure above 220 GPa for GeH{sub 4}(H{sub 2}){sub 2}. The variations of bond lengths, electronic structures, phonon spectra, and electron-phonon interaction with the increases of pressure are investigated. We find that the superconducting transition temperature monotonously decreases with the increase of pressure from 230 to 350 GPa. The origin is mainly the stiff of phonon frequency induced by pressurization.

  6. Pressure-induced superconductivity in CaC2

    Science.gov (United States)

    Li, Yan-Ling; Luo, Wei; Zeng, Zhi; Lin, Hai-Qing; Mao, Ho-kwang; Ahuja, Rajeev

    2013-01-01

    Carbon can exist as isolated dumbbell, 1D chain, 2D plane, and 3D network in carbon solids or carbon-based compounds, which attributes to its rich chemical binding way, including sp-, sp2-, and sp3-hybridized bonds. sp2-hybridizing carbon always captures special attention due to its unique physical and chemical property. Here, using an evolutionary algorithm in conjunction with ab initio method, we found that, under compression, dumbbell carbon in CaC2 can be polymerized first into 1D chain and then into ribbon and further into 2D graphite sheet at higher pressure. The C2/m structure transforms into an orthorhombic Cmcm phase at 0.5 GPa, followed by another orthorhombic Immm phase, which is stabilized in a wide pressure range of 15.2–105.8 GPa and then forced into MgB2-type phase with wide range stability up to at least 1 TPa. Strong electron–phonon coupling λ in compressed CaC2 is found, in particular for Immm phase, which has the highest λ value (0.562–0.564) among them, leading to its high superconducting critical temperature Tc (7.9∼9.8 K), which is comparable with the 11.5 K value of CaC6. Our results show that calcium not only can stabilize carbon sp2 hybridization at a larger range of pressure but also can contribute in superconducting behavior, which would further ignite experimental and theoretical interest in alkaline–earth metal carbides to uncover their peculiar physical properties under extreme conditions. PMID:23690580

  7. Pressure-induced superconductivity in Bi single crystals

    Science.gov (United States)

    Li, Yufeng; Wang, Enyu; Zhu, Xiyu; Wen, Hai-Hu

    2017-01-01

    Measurements on resistivity and magnetic susceptibility have been carried out for Bi single crystals under pressures up to 10.5 GPa. The temperature dependent resistivity shows a semimetallic behavior at ambient and low pressures (below about 1.6 GPa). This is followed by an upturn of resistivity in the low temperature region when the pressure is increased, which is explained as a semiconductor behavior. This feature gradually gets enhanced up to a pressure of about 2.52 GPa. Then a nonmonotonic temperature dependent resistivity appears upon further increasing pressure, which is accompanied by a strong suppression to the low temperature resistivity upturn. Simultaneously, a superconducting transition occurs at about 3.92 K under a pressure of about 2.63 GPa. With further increasing pressure, a second superconducting transition emerges at about 7 K under about 2.8 GPa. For these two superconducting states, the superconductivity induced magnetic screening volumes are quite large. As the pressure further increases to 8.1 GPa, we observe the third superconducting transition at about 8.2 K. The resistivity measurements under magnetic field allow us to determine the upper critical fields μ0Hc 2 of the superconducting phases. The upper critical field for the phase with Tc=3.92 K is extremely low. Based on the Werthamer-Helfand-Hohenberg (WHH) theory, the estimated value of μ0Hc 2 for this phase is about 0.103 T, while the upper critical field for the phase with Tc=7 K is very high with a value of about 4.56 T. Finally, we present a pressure dependent phase diagram of Bi single crystals. Our results reveal the interesting and rich physics in bismuth single crystals under high pressure.

  8. Enhanced MgB2 Superconductivity Under High Pressure

    Institute of Scientific and Technical Information of China (English)

    刘振兴; 靳常青; 游江洋; 李绍春; 朱嘉林; 禹日成; 李风英; 苏少奎

    2002-01-01

    We report on in situ high-pressure studies up to 1.0 GPa on the MgB2 superconductor which was high-pressure synthesized. The as-prepared sample is of high quality in terms of sharp superconducting transition (Tc) at 39K from the magnetic measurements. The in situ high-pressure measurements were carried out using a Be-Cu piston-cylinder-type instrument with mixed oil as the pressure transmitting medium which warrants a quasihydrostatic pressure environment at low temperature. The superconducting transitions were measured using the electrical conductance method. It is found that Tc increases by more than 1 K with pressure in the low-pressure range, before the Tc value decreases with the further increase of the pressure.

  9. Some unique superconductive Properties of Cuprates

    Science.gov (United States)

    Müller, K. A.

    2013-04-01

    Copper oxides are the only materials that show transition temperatures, Tc, above the boiling point of liquid nitrogen, with a maximum Tmc of 162 K under pressure. Their structure is layered, with one to several CuO2 planes, and upon hole doping, their transition temperature follows a dome-shaped curve with a maximum at Tmc. In the underdoped regime, i.e., below Tmc, a pseudogap T* is found, with T* always being larger than Tc, a property unique to the copper oxides [1]. In the superconducting state, Cooper pairs (two holes with antiparallel spins) are formed that exhibit coherence lengths on the order of a lattice distance in the CuO2 plane and one order of magnitude less perpendicular to it. Their macroscopic wave function is parallel to the CuO2 plane near 100% d at their surface, but only 75% d and 25 % s in the bulk, and near 100% s perpendicular to the plane in YBCO. There are two gaps with the same Tc [2]. As function of doping, the oxygen isotope effect is novel and can be quantitatively accounted for by a two-band vibronic theory [3] near Tmc, and underdoped below it till Tc = 0 with by a formula valid for (bi)polarons [4]. These cuprates are intrinsically heterogeneous in a dynamic way. In terms of quasiparticles, Jahn-Teller bipolarons are present at low doping, and aggregate upon cooling [1], so that probably ramified clusters and/or stripes are formed, leading over to a more Fermi-liquid-type behavior at large carrier concentrations above Tmc.

  10. Superconductivity in Electric Double Layer Capacitor under Pressure

    Science.gov (United States)

    McCann, Duncan; Misek, Martin; Kamenev, Konstantin; Huxley, Andrew

    2015-03-01

    Chemical doping generally provides the most common method for tuning into the superconducting state of a material yet can be difficult to control and also potentially introduces structural disorder complicating the underlying physics. Electric Double Layer devices however provide a means to electrostatically dope materials with high electric fields allowing continuous tuning of a 2D superconducting state thus avoiding such issues. One such device is the Electric Double Layer Capacitor which can detect the onset of superconductivity through AC magnetisation measurements. We make use of a similar device in an attempt to electrostatically dope and tune the superconductivity in the cuprate compound La1.93Sr0.07CuO4 as well as investigating whether application of pressure improves its efficiency.

  11. Coherence properties in superconducting flux qubits

    Energy Technology Data Exchange (ETDEWEB)

    Spilla, Samuele

    2015-02-16

    The research work discussed in this thesis deals with the study of superconducting Josephson qubits. Superconducting qubits are solid-state artificial atoms which are based on lithographically defined Josephson tunnel junctions properties. When sufficiently cooled, these superconducting devices exhibit quantized states of charge, flux or junction phase depending on their design parameters. This allows to observe coherent evolutions of their states. The results presented can be divided into two parts. In a first part we investigate operations of superconducting qubits based on the quantum coherence in superconducting quantum interference devices (SQUID). We explain experimental data which has been observed in a SQUID subjected to fast, large-amplitude modifications of its effective potential shape. The motivations for this work come from the fact that in the past few years there have been attempts to interpret the supposed quantum behavior of physical systems, such as Josephson devices, within a classical framework. Moreover, we analyze the possibility of generating GHZ states, namely maximally entangled states, in a quantum system made out of three Josephson qubits. In particular, we investigate the possible limitations of the GHZ state generation due to coupling to bosonic baths. In the second part of the thesis we address a particular cause of decoherence of flux qubits which has been disregarded until now: thermal gradients, which can arise due to accidental non equilibrium quasiparticle distributions. The reason for these detrimental effects is that heat currents flowing through Josephson tunnel junctions in response to a temperature gradient are periodic functions of the phase difference between the electrodes. The phase dependence of the heat current comes from Andreev reflection, namely an interplay between the quasiparticles which carry heat and the superconducting condensate which is sensitive to the superconducting phase difference. Generally speaking

  12. Effects of phosphorous doping on the superconducting properties of SmFeAs(O,F)

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Shiv Jee, E-mail: shivjees@gmail.com; Shimoyama, Jun-ichi; Yamamoto, Akiyasu; Ogino, Hiraku; Kishio, Kohji

    2014-09-15

    Highlights: • Doping effects of P on the superconducting properties of Sm1111 is studied. • P doping induces chemical pressure and strongly deteriorate the superconductivity. • These isovalent doping effects are compared with Mn and Ni doping in FeAs layers. • Electron type charge carrier dominates in the transport properties. • Doping without disrupting FeAs layer is a best way for high T{sub c} superconductivity. - Abstract: The systematic doping effect induced by the isovalent substitution of P for As on the superconducting properties of F-doped SmFeAsO{sub 0.88}F{sub 0.12} (Sm1111) has been studied by physical and magnetic measurements. The cell volume (V) decreases with P doping and the anisotropic chemical pressure might be induced. However, the superconducting transition temperature (T{sub c}) and the upper critical field (H{sub c2}) are suppressed. Thermoelectric power (S) indicates the majority of electron type charge carriers in support of Hall measurements and its magnitude does not change very much for different P concentrations. The present investigation depicts that isovalent substitutions in the FeAs layer strongly deteriorate the superconducting properties of Sm1111 as a result of increase in chemical pressure. These isovalent substitution effects are comparatively discussed with hole (Mn) and electron (Ni) type substitutions in the superconducting layer of Sm1111.

  13. High temperature superconductivity in sulfur and selenium hydrides at high pressure

    Science.gov (United States)

    Flores-Livas, José A.; Sanna, Antonio; Gross, E. K. U.

    2016-03-01

    Due to its low atomic mass, hydrogen is the most promising element to search for high-temperature phononic superconductors. However, metallic phases of hydrogen are only expected at extreme pressures (400 GPa or higher). The measurement of the record superconducting critical temperature of 203 K in a hydrogen-sulfur compound at 160 GPa of pressure [A.P. Drozdov, M.I. Eremets, I.A. Troyan, arXiv:1412.0460; [cond-mat.supr-con] (2014); A.P. Drozdov, M.I. Eremets, I.A. Troyan, V. Ksenofontov, S.I. Shylin, Nature 525, 73 (2015)], shows that metallization of hydrogen can be reached at significantly lower pressure by inserting it in the matrix of other elements. In this work we investigate the phase diagram and the superconducting properties of the H-S systems by means of minima hopping method for structure prediction and density functional theory for superconductors. We also show that Se-H has a similar phase diagram as its sulfur counterpart as well as high superconducting critical temperature. We predict H3Se to exceed 120 K superconductivity at 100 GPa. We show that both H3Se and H3S, due to the critical temperature and peculiar electronic structure, present rather unusual superconducting properties. Supplementary material in the form of one pdf file available from the Journal web page at: http://dx.doi.org/10.1140/epjb/e2016-70020-0

  14. Vortex properties of mesoscopic superconducting samples

    Energy Technology Data Exchange (ETDEWEB)

    Cabral, Leonardo R.E. [Laboratorio de Supercondutividade e Materiais Avancados, Departamento de Fisica, Universidade Federal de Pernambuco, Recife 50670-901 (Brazil); Barba-Ortega, J. [Grupo de Fi' sica de Nuevos Materiales, Departamento de Fisica, Universidad Nacional de Colombia, Bogota (Colombia); Souza Silva, C.C. de [Laboratorio de Supercondutividade e Materiais Avancados, Departamento de Fisica, Universidade Federal de Pernambuco, Recife 50670-901 (Brazil); Albino Aguiar, J., E-mail: albino@df.ufpe.b [Laboratorio de Supercondutividade e Materiais Avancados, Departamento de Fisica, Universidade Federal de Pernambuco, Recife 50670-901 (Brazil)

    2010-10-01

    In this work we investigated theoretically the vortex properties of mesoscopic samples of different geometries, submitted to an external magnetic field. We use both London and Ginzburg-Landau theories and also solve the non-linear Time Dependent Ginzburg-Landau equations to obtain vortex configurations, equilibrium states and the spatial distribution of the superconducting electron density in a mesoscopic superconducting triangle and long prisms with square cross-section. For a mesoscopic triangle with the magnetic field applied perpendicularly to sample plane the vortex configurations were obtained by using Langevin dynamics simulations. In most of the configurations the vortices sit close to the corners, presenting twofold or three-fold symmetry. A study of different meta-stable configurations with same number of vortices is also presented. Next, by taking into account de Gennes boundary conditions via the extrapolation length, b, we study the properties of a mesoscopic superconducting square surrounded by different metallic materials and in the presence of an external magnetic field applied perpendicularly to the square surface. It is determined the b-limit for the occurrence of a single vortex in a mesoscopic square of area d{sup 2}, for 4{xi}(0){<=}d{<=}10{xi}(0).

  15. Tuning the Superconducting Properties of Magnesium Diboride

    Energy Technology Data Exchange (ETDEWEB)

    Theoderich Wilke, Rudeger Heinrich [Iowa State Univ., Ames, IA (United States)

    2005-01-01

    This work is presented in the following order: A review of the relevant physics and discussion of theoretical predictions for a two gap superconducting compound is given in chapter 2. Chapter 3 provides a review of the basic properties of MgB2. Details of sample synthesis and characterization are given in chapter 4. Chapter 5 presents normal state and superconducting properties of Mg(B1-xCx)2 wires. Attempts to increase critical current densities in filaments via titanium additions are discussed in chapter 6. In chapters 7 and 8 alternative methods for synthesizing doped MgB2 powders are explored. In chapter 7 we synthesize Mg(B1-xCx)2 up to x=0.069 using a mixture of Mg, B, and the binary compound B4C. Chapter 8 explores an alternative method, plasma spray synthesis, to produce nanometer sized doped boron powders for powder-in-tube applications. The effects of neutron irradiation on pure MgB2 wires is discussed in chapter 9. This is followed by a study of the effects of neutron irradiation on Mg(B.962C.038)2 wires, presented in chapter 10. I will summarize the results of all of these studies in chapter 11 and discuss future directions for research in understanding the physics behind this novel material as well as its development for practical applications. In this thesis I have presented the results of investigations into the changes in the superconducting properties of MgB2 as a function of carbon doping and neutron irradiation. The goal has been to understand the physics underlying this unique two-gap superconductor as different types of perturbations are made to the system. Such knowledge not only contributes to our understanding of two-gap superconductivity, but could potentially lead to the development of superconducting MgB2 wires for the use in power applications near 20 K.

  16. Method for obtaining large levitation pressure in superconducting magnetic bearings

    Energy Technology Data Exchange (ETDEWEB)

    Hull, John R. (Hinsdale, IL)

    1996-01-01

    A method and apparatus for compressing magnetic flux to achieve high levitation pressures. Magnetic flux produced by a magnetic flux source travels through a gap between two high temperature superconducting material structures. The gap has a varying cross-sectional area to compress the magnetic flux, providing an increased magnetic field and correspondingly increased levitation force in the gap.

  17. Method for obtaining large levitation pressure in superconducting magnetic bearings

    Energy Technology Data Exchange (ETDEWEB)

    Hull, John R. (Hinsdale, IL)

    1997-01-01

    A method and apparatus for compressing magnetic flux to achieve high levitation pressures. Magnetic flux produced by a magnetic flux source travels through a gap between two high temperature superconducting material structures. The gap has a varying cross-sectional area to compress the magnetic flux, providing an increased magnetic field and correspondingly increased levitation force in the gap.

  18. Superconductivity in an Organic Solid at Zero Pressure

    DEFF Research Database (Denmark)

    Bechgaard, Klaus; da Costa Carneiro, Kim; Jacobsen, C.S.;

    1981-01-01

    Resistance measurements in the organic conductor (TMTSF)2C104 have given evidence of superconductivity in the absence of applied pressure. Transition temperatures were between 1.2 and 1.4 K for different crystals. A transverse magnetic field of 25 mT nearly restores normal resistance at 0.9 K...

  19. Pressure induced superconductivity on the border of magnetic order in MnP.

    Science.gov (United States)

    Cheng, J-G; Matsubayashi, K; Wu, W; Sun, J P; Lin, F K; Luo, J L; Uwatoko, Y

    2015-03-20

    We report the discovery of superconductivity on the border of long-range magnetic order in the itinerant-electron helimagnet MnP via the application of high pressure. Superconductivity with T(sc)≈1  K emerges and exists merely near the critical pressure P(c)≈8  GPa, where the long-range magnetic order just vanishes. The present finding makes MnP the first Mn-based superconductor. The close proximity of superconductivity to a magnetic instability suggests an unconventional pairing mechanism. Moreover, the detailed analysis of the normal-state transport properties evidenced non-Fermi-liquid behavior and the dramatic enhancement of the quasiparticle effective mass near P(c) associated with the magnetic quantum fluctuations.

  20. RF and Surface Properties of Superconducting Samples

    CERN Document Server

    Junginger, T; Weingarten, W; Welsch, C

    2011-01-01

    At CERN a compact Quadrupole Resonator has been developed for the RF characterization of superconducting samples at different frequencies. In this paper, results from measurements on bulk niobium and niobium filmon copper substrate samples are presented. We show how different contributions to the surface resistance depend on temperature, applied RF magnetic field and frequency. Furthermore, measurements of the maximum RF magnetic field as a function of temperature and frequency in pulsed and CW operation are presented. The study is accompanied by measurements of the surface properties of the samples by various techniques.

  1. Theoretical investigation of superconductivity in Ba(AlSn) under pressure

    Science.gov (United States)

    Parlak, Cihan

    2016-10-01

    The compound of Ba(AlSn) from ternary superconductors exhibits the superconductivity behaviour below the temperature 2.9 K. We report the results of an ab initio study based on electronic, and detailed lattice dynamical properties as a function of pressure of superconducting material. The phonon dispersion curves along the high-symmetry directions and phonon frequencies parameters at the Brillouin zone center are computed by using density functional perturbation theory while the elastic constants are calculated in metric-tensor formulation. The Vickers hardness belonging to the compound is also evaluated clearly. The band structure, partial densities of states and Fermi surface topology are also discussed in detail. At the same time we describe the relationship between the properties determined and superconducting characteristic.

  2. Effects of phosphorous doping on the superconducting properties of SmFeAs(O,F)

    Science.gov (United States)

    Singh, Shiv Jee; Shimoyama, Jun-ichi; Yamamoto, Akiyasu; Ogino, Hiraku; Kishio, Kohji

    2014-09-01

    The systematic doping effect induced by the isovalent substitution of P for As on the superconducting properties of F-doped SmFeAsO0.88F0.12 (Sm1111) has been studied by physical and magnetic measurements. The cell volume (V) decreases with P doping and the anisotropic chemical pressure might be induced. However, the superconducting transition temperature (Tc) and the upper critical field (Hc2) are suppressed. Thermoelectric power (S) indicates the majority of electron type charge carriers in support of Hall measurements and its magnitude does not change very much for different P concentrations. The present investigation depicts that isovalent substitutions in the FeAs layer strongly deteriorate the superconducting properties of Sm1111 as a result of increase in chemical pressure. These isovalent substitution effects are comparatively discussed with hole (Mn) and electron (Ni) type substitutions in the superconducting layer of Sm1111.

  3. Anisotropy of the superconducting transition temperature under uniaxial pressure

    Science.gov (United States)

    Chen, X. J.; Lin, H. Q.; Yin, W. G.; Gong, C. D.; Habermeier, H.-U.

    2001-12-01

    The superconducting transition temperature Tc is calculated as a function of uniaxial pressure along the a, b, c directions for optimally doped YBa2Cu3O7-δ on the basis of a hole dispersion of the anisotropic t-J model. There is a good qualitative agreement with experiments. We show that the uniaxial pressure effect on Tc in the ab plane is due to the anisotropies of the hole dispersion and the in-plane pairing interaction, whereas the reduction of Tc under uniaxial compression along the c axis mainly results from the pressure-induced increase of hole concentration of the CuO2 plane.

  4. High pressure investigation of pressure-induced superconductivity in CaFe{sub 2}As{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Reuvekamp, Patrick; Kremer, Reinhard [Max-Planck-Institut fuer Festkoerperforschung, Stuttgart (Germany); Gonnelli, Renato [Dipartimento di Fisica, CNISM, Politecnico di Torino (Italy); Karpinski, Janusz [ETH Zurich (Switzerland)

    2011-07-01

    Since the discovery of superconductivity in iron pnictides, many compounds in this family have been heavily studied due the easily induced superconductivity using chemical doping. In the case of CaFe{sub 2}As{sub 2}, high pressure can be used to establish and tune superconductivity instead. In this investigation, the phase diagram and the pressure induced onset/disappearance of superconductivity were studied using ac-resistive measurements in magnetic fields up to 11 T.

  5. Measurement of improved pressure dependence of superconducting transition temperature

    Science.gov (United States)

    Karmakar, S.

    2013-06-01

    We describe a technique for making electrical transport measurements in a diamond anvil cell at liquid helium temperature having in situ pressure measurement option, permitting accurate pressure determination at any low temperature during the resistance measurement scan. In general, for four-probe resistivity measurements on a polycrystalline sample, four fine gold wires are kept in contact with the sample with the help of the compression from the soft solid (usually alkali halides such as NaCl, KCl, etc.) acting as a pressure-transmitting medium. The actual pressure on the sample is underestimated if not measured from a ruby sphere placed adjacent to the sample and at that very low temperature. Here, we demonstrate the technique with a quasi-four-probe resistance measurement on an Fe-based superconductor in the temperature range 1.2-300 K and pressures up to 8 GPa to find an improved pressure dependence of the superconducting transition temperature.

  6. Superconductivity in HfTe5 across weak to strong topological insulator transition induced via pressures.

    Science.gov (United States)

    Liu, Y; Long, Y J; Zhao, L X; Nie, S M; Zhang, S J; Weng, Y X; Jin, M L; Li, W M; Liu, Q Q; Long, Y W; Yu, R C; Gu, C Z; Sun, F; Yang, W G; Mao, H K; Feng, X L; Li, Q; Zheng, W T; Weng, H M; Dai, X; Fang, Z; Chen, G F; Jin, C Q

    2017-03-16

    Recently, theoretical studies show that layered HfTe5 is at the boundary of weak &strong topological insulator (TI) and might crossover to a Dirac semimetal state by changing lattice parameters. The topological properties of 3D stacked HfTe5 are expected hence to be sensitive to pressures tuning. Here, we report pressure induced phase evolution in both electronic &crystal structures for HfTe5 with a culmination of pressure induced superconductivity. Our experiments indicated that the temperature for anomaly resistance peak (Tp) due to Lifshitz transition decreases first before climbs up to a maximum with pressure while the Tp minimum corresponds to the transition from a weak TI to strong TI. The HfTe5 crystal becomes superconductive above ~5.5 GPa where the Tp reaches maximum. The highest superconducting transition temperature (Tc) around 5 K was achieved at 20 GPa. Crystal structure studies indicate that HfTe5 transforms from a Cmcm phase across a monoclinic C2/m phase then to a P-1 phase with increasing pressure. Based on transport, structure studies a comprehensive phase diagram of HfTe5 is constructed as function of pressure. The work provides valuable experimental insights into the evolution on how to proceed from a weak TI precursor across a strong TI to superconductors.

  7. Absence of superconductivity in the high-pressure polymorph of MgB2

    Science.gov (United States)

    Ma, Yanming; Wang, Yanchao; Oganov, Artem R.

    2009-02-01

    We report a high-pressure orthorhombic KHg2 -type polymorph (space group Imma, 4 f.u./cell) of MgB2 stable above 190 GPa predicted through ab-initio evolutionary simulations. The formation of this new phase results from the strong out-of-plane distortions of the two-dimensional honeycomb boron sublattice of the low-pressure AlB2 -type structure creating a peculiar tetrahedrally bonded three-dimensional boron network. This high-pressure phase is a weak metal and not superconducting, re-highlighting the key role of the planar boron sublattice in forming the superconducting state and clear structure-property relations that can enable design of new superconductors.

  8. Superconductive "sodalite"-like clathrate calcium hydride at high pressures

    CERN Document Server

    Wang, Hui; Tanaka, Kaori; Iitaka, Toshiaki; Ma, Yanming

    2012-01-01

    Hydrogen-rich compounds hold promise as high-temperature superconductors under high pressures. Recent theoretical hydride structures on achieving high-pressure superconductivity are composed mainly of H2 fragments. Through a systematic investigation of Ca hydrides with different hydrogen contents using particle-swam optimization structural search, we show that in the stoichiometry CaH6 a body-centred cubic structure with hydrogen that forms unusual "sodalite" cages containing enclathrated Ca stabilizes above pressure 150 GPa. The stability of this structure is derived from the acceptance by two H2 of electrons donated by Ca forming a "H4" unit as the building block in the construction of the 3-dimensional sodalite cage. This unique structure has a partial occupation of the degenerated orbitals at the zone centre. The resultant dynamic Jahn-Teller effect helps to enhance electron-phonon coupling and leads to superconductivity of CaH6. A superconducting critical temperature (Tc) of 220-235 K at 150 GPa obtained...

  9. Superconductivity

    CERN Document Server

    Poole, Charles P; Creswick, Richard J; Prozorov, Ruslan

    2014-01-01

    Superconductivity, Third Edition is an encyclopedic treatment of all aspects of the subject, from classic materials to fullerenes. Emphasis is on balanced coverage, with a comprehensive reference list and significant graphics from all areas of the published literature. Widely used theoretical approaches are explained in detail. Topics of special interest include high temperature superconductors, spectroscopy, critical states, transport properties, and tunneling. This book covers the whole field of superconductivity from both the theoretical and the experimental point of view. This third edition features extensive revisions throughout, and new chapters on second critical field and iron based superconductors.

  10. 1D-transport properties of single superconducting lead nanowires

    DEFF Research Database (Denmark)

    Michotte, S.; Mátéfi-Tempfli, Stefan; Piraux, L.

    2003-01-01

    We report on the transport properties of single superconducting lead nanowires grown by an electrodeposition technique, embedded in a nanoporous track-etched polymer membrane. The nanowires are granular, have uniform diameter of ̃40 nm and a very large aspect ratio (̃500). The diameter of the nan......We report on the transport properties of single superconducting lead nanowires grown by an electrodeposition technique, embedded in a nanoporous track-etched polymer membrane. The nanowires are granular, have uniform diameter of ̃40 nm and a very large aspect ratio (̃500). The diameter...... of the nanowire is small enough to ensure a 1D superconducting regime in a wide temperature range below T. The non-zero resistance in the superconducting state and its variation caused by fluctuations of the superconducting order parameter were measured versus temperature, magnetic field, and applied DC current...

  11. Modification of superconducting and resistive properties of HoBa2Cu3O7-δ single crystals under application-removal of high hydrostatic pressure

    Science.gov (United States)

    Vovk, R. V.; Khadzhai, G. Ya.; Dobrovolskiy, O. V.; Kamchatna, S. N.; Chroneos, A.

    2016-06-01

    The influence of a high hydrostatic pressure on the basal-plane electrical resistance along the twin boundaries in underdoped HoBa2Cu3O7-δ single crystals is investigated. An enhancement of the phase segregation caused by the high-pressure-induced redistribution of the labile oxygen has been revealed. The temperature dependences of the electrical resistance above Tc can be approximated well within the framework of the model of s - d electron-phonon scattering.

  12. Superconductivity in Group III-V Semiconductor AlN Under High Pressure

    Directory of Open Access Journals (Sweden)

    G. Selva Dancy

    2015-09-01

    Full Text Available The electronic properties of cubic zinc blende type group III-V semiconductor AlN under pressure is studied using full potential linear muffin-tin orbital (FP-LMTO method. At normal pressure, AlN is an indirect bandgap semiconductor with band gap value 4.56 eV. When the pressure is increased, there is enhanced overlapping between the wave functions of the neighboring atoms. As a result the widths of the valence and empty conduction bands increase. These changes lead to the narrowing and indirect closing of the band gaps in AlN (metallization. On further increase of pressure, AlN becomes a superconductor and AlN comes under the class of electron-phonon-mediated high pressure superconductors. The superconducting transition temperatures (Tc of AlN are obtained as a function of pressure for the CsCl structure. It is also confirmed that the metallization, structural phase transition and onset of superconductivity do not occur simultaneously in this compound. DOI: http://dx.doi.org/10.17807/orbital.v7i3.628

  13. Superconductivity and magnetism: Materials properties and developments

    Energy Technology Data Exchange (ETDEWEB)

    Andersen, N.H.; Bay, N.; Grivel, J.C. (eds.) [and others

    2003-07-01

    The 24th Risoe International Symposium on Materials Science focuses on development of new materials, devices and applications, as well as experimental and theoretical studies of novel and unexplained phenomena in superconductivity and magnetism, e.g. within high.T{sub c} superconductivity, magnetic superconductors, MgB{sub 2}, CMR materials, nanomagnetism and spin-tronics. The aim is to stimulate exchange of ideas and establish new collaborations between leading Danish and international scientists. The topics are addressed by presentations from 24 invited speakers and by 41 contributed papers. (ln)

  14. Pressure-driven formation and stabilization of superconductive chromium hydrides

    Science.gov (United States)

    Yu, Shuyin; Jia, Xiaojing; Frapper, Gilles; Li, Duan; Oganov, Artem R.; Zeng, Qingfeng; Zhang, Litong

    2015-01-01

    Chromium hydride is a prototype stoichiometric transition metal hydride. The phase diagram of Cr-H system at high pressures remains largely unexplored due to the challenges in dealing with the high activation barriers and complications in handing hydrogen under pressure. We have performed an extensive structural study on Cr-H system at pressure range 0 ∼ 300 GPa using an unbiased structure prediction method based on evolutionary algorithm. Upon compression, a number of hydrides are predicted to become stable in the excess hydrogen environment and these have compositions of Cr2Hn (n = 2–4, 6, 8, 16). Cr2H3, CrH2 and Cr2H5 structures are versions of the perfect anti-NiAs-type CrH with ordered tetrahedral interstitial sites filled by H atoms. CrH3 and CrH4 exhibit host-guest structural characteristics. In CrH8, H2 units are also identified. Our study unravels that CrH is a superconductor at atmospheric pressure with an estimated transition temperature (T c) of 10.6 K, and superconductivity in CrH3 is enhanced by the metallic hydrogen sublattice with T c of 37.1 K at 81 GPa, very similar to the extensively studied MgB2. PMID:26626579

  15. Superconductivity and unexpected chemistry of germanium hydrides under pressure

    Science.gov (United States)

    Davari Esfahani, M. Mahdi; Oganov, Artem R.; Niu, Haiyang; Zhang, Jin

    2017-04-01

    Following the idea that hydrogen-rich compounds might be high-Tc superconductors at high pressures, and the very recent breakthrough in predicting and synthesizing hydrogen sulfide with record-high Tc=203 K , an ab initio evolutionary algorithm for crystal structure prediction was employed to find stable germanium hydrides. In addition to the earlier structure of germane with space group Ama2, we propose a C2/m structure, which is energetically more favorable at pressures above 278 GPa (with inclusion of zero-point energy). Our calculations indicate that the C2/m phase of germane is a superconductor with Tc=67 K at 280 GPa. Germane is found to become thermodynamically unstable to decomposition to hydrogen and the compound Ge3H11 at pressures above 300 GPa. Ge3H11 with space group I 4 ¯m 2 is found to become stable at above 285 GPa with Tc=43 K . We find that the pressure-induced phase stability of germanium hydrides is distinct from analogous isoelectronic systems, e.g., Si hydrides and Sn hydrides. Superconductivity stems from large electron-phonon coupling associated with the wagging, bending, and stretching intermediate-frequency modes derived mainly from hydrogen.

  16. Dense superconducting phases of copper-bismuth at high pressure

    Science.gov (United States)

    Amsler, Maximilian; Wolverton, Chris

    2017-08-01

    Although copper and bismuth do not form any compounds at ambient conditions, two intermetallics, CuBi and Cu11Bi7 , were recently synthesized at high pressures. Here we report on the discovery of additional copper-bismuth phases at elevated pressures with high densities from ab initio calculations. In particular, a Cu2Bi compound is found to be thermodynamically stable at pressures above 59 GPa, crystallizing in the cubic Laves structure. In strong contrast to Cu11Bi7 and CuBi, cubic Cu2Bi does not exhibit any voids or channels. Since the bismuth lone pairs in cubic Cu2Bi are stereochemically inactive, the constituent elements can be closely packed and a high density of 10.52 g/cm3 at 0 GPa is achieved. The moderate electron-phonon coupling of λ =0.68 leads to a superconducting temperature of 2 K, which exceeds the values observed both in Cu11Bi7 and CuBi, as well as in elemental Cu and Bi.

  17. Tunneling properties of electromagnetic wave in slab superconducting material

    Institute of Scientific and Technical Information of China (English)

    Khem B. Thapa; Sanjay Srivastava; Alka Vishwakarma; S. P. Ojha

    2011-01-01

    When the electromagnetic wave propagates through a slab superconducting material in microwave ranges, tunneling properties of the electromagnetic wave at critical temperature are investigated theoretically. The transmittance and the reflectance of the slab superconducting material vary with the thickness of material as well as the refractive index of substrates.The high transmittance is found for thin superconductor at low wavelength region.However, optical properties are strongly dependent upon temperature and incidence wavelength. The electromagnetic wave is totally transmitted without loss for incidence wavelength (λ = 5000 nm) due to the zero refractive index and infinite penetration depth of the superconductor at the critical temperature.

  18. Investigation of superconducting properties of nanowires prepared by template synthesis

    DEFF Research Database (Denmark)

    Michotte, S.; Mátéfi-Tempfli, Stefan; Piraux, L.

    2003-01-01

    We report on the transport properties of single superconducting lead nanowires grown by an electrodeposition technique, embedded in a nanoporous track-etched polymer membrane. The nanowires are granular, have a uniform diameter of ∼40 nm and a very large aspect ratio (∼500). The diameter of the n......We report on the transport properties of single superconducting lead nanowires grown by an electrodeposition technique, embedded in a nanoporous track-etched polymer membrane. The nanowires are granular, have a uniform diameter of ∼40 nm and a very large aspect ratio (∼500). The diameter...

  19. High pressure superconductivity in iron-based layered compounds studied using designer diamonds

    Energy Technology Data Exchange (ETDEWEB)

    Tsoi, Georgiy; Stemshorn, Andrew K; Vohra, Yogesh K [Department of Physics, University of Alabama at Birmingham (UAB), Birmingham, AL 35294 (United States); Wu, Phillip M [Department of Physics, Duke University, Durham, NC 27708 (United States); Hsu, F C; Huang, Y L; Wu, M K; Yeh, K W [Institute of Physics, Academia Sinica-Nankang, Taipei, Taiwan (China); Weir, Samuel T [Lawrence Livermore National Laboratory, Mail Stop L-041, Livermore, CA 94550 (United States)

    2009-06-10

    High pressure superconductivity in iron-based superconductor FeSe{sub 0.5}Te{sub 0.5} has been studied up to 15 GPa and 10 K using an eight probe designer diamond anvil in a diamond anvil cell device. Four probe electrical resistance measurements show the onset of superconductivity (T{sub c}) at 14 K at ambient pressure with T{sub c} increasing with increasing pressure to 19 K at a pressure of 3.6 GPa. At higher pressures beyond 3.6 GPa, T{sub c} decreases and extrapolation suggests non-superconducting behavior above 10 GPa. The loss of superconductivity coincides with the pressure induced disordering of the Fe(SeTe){sub 4} tetrahedra reported at 11 GPa in x-ray diffraction studies at ambient temperature. (fast track communication)

  20. Superconducting properties of long TiN wires

    Science.gov (United States)

    Mironov, A. Yu.; Postolova, S. V.; Nasimov, D. A.

    2016-12-01

    The low-temperature transport properties of titanium nitride wires with the width comparable with or much larger than the superconducting coherence length are studied experimentally. It is shown that the reduction of the width of wires does not affect the transport properties at the temperatures above the superconducting transition temperature and electron transport in this temperature range is determined by quantum contributions to the conductivity from weak localization and electron-electron interaction. It is established that the reduction of the width of wires does not change the superconducting transition temperature but completely suppresses the topological Berezinskii-Kosterlitz-Thouless transition. It is found that the threshold magnetic field increases with a decrease in the width of wires.

  1. Pressure controlled transition into a self-induced topological superconducting surface state

    KAUST Repository

    Zhu, Zhiyong

    2014-02-07

    Ab-initio calculations show a pressure induced trivial-nontrivial-trivial topological phase transition in the normal state of 1T-TiSe2. The pressure range in which the nontrivial phase emerges overlaps with that of the superconducting ground state. Thus, topological superconductivity can be induced in protected surface states by the proximity effect of superconducting bulk states. This kind of self-induced topological surface superconductivity is promising for a realization of Majorana fermions due to the absence of lattice and chemical potential mismatches. For appropriate electron doping, the formation of the topological superconducting surface state in 1T-TiSe 2 becomes accessible to experiments as it can be controlled by pressure.

  2. Superconductivity of lithium-doped hydrogen under high pressure.

    Science.gov (United States)

    Xie, Yu; Li, Quan; Oganov, Artem R; Wang, Hui

    2014-02-01

    The high-pressure lattice dynamics and superconductivity of newly proposed lithium hydrides (LiH2, LiH6 and LiH8) have been extensively studied using density functional theory. The application of the Allen-Dynes modified McMillan equation and electron-phonon coupling calculations show that LiH6 and LiH8 are superconductors with critical temperatures (T(c)) of 38 K at 150 GPa for LiH6 and 31 K at 100 GPa for LiH8, while LiH2 is not a superconductor. The T(c) of LiH6 increases rapidly with pressure and reaches 82 K at 300 GPa due to enhancement of the electron-phonon coupling and the increased density of states at the Fermi level, while the T(c) of LiH8 remains almost constant.

  3. Superconducting Accelerating Cavity Pressure Sensitivity Analysis and Stiffening

    Energy Technology Data Exchange (ETDEWEB)

    Rodnizki, J [Soreq NRC, Yavne, Israel; Ben Aliz, Y [Soreq NRC, Yavne, Israel; Grin, A [Soreq NRC, Yavne, Israel; Horvitz, Z [Soreq NRC, Yavne, Israel; Perry, A [Soreq NRC, Yavne, Israel; Weissman, L [Soreq NRC, Yavne, Israel; Davis, G Kirk [JLAB; Delayen, Jean R. [Old Dominion Universtiy

    2014-12-01

    The Soreq Applied Research Accelerator Facility (SARAF) design is based on a 40 MeV 5 mA light ions superconducting RF linac. Phase-I of SARAF delivers up to 2 mA CW proton beams in an energy range of 1.5 - 4.0 MeV. The maximum beam power that we have reached is 5.7 kW. Today, the main limiting factor to reach higher ion energy and beam power is related to the HWR sensitivity to the liquid helium coolant pressure fluctuations. The HWR sensitivity to helium pressure is about 60 Hz/mbar. The cavities had been designed, a decade ago, to be soft in order to enable tuning of their novel shape. However, the cavities turned out to be too soft. In this work we found that increasing the rigidity of the cavities in the vicinity of the external drift tubes may reduce the cavity sensitivity by a factor of three. A preliminary design to increase the cavity rigidity is presented.

  4. Pressure-induced electronic phase separation of magnetism and superconductivity in CrAs.

    Science.gov (United States)

    Khasanov, Rustem; Guguchia, Zurab; Eremin, Ilya; Luetkens, Hubertus; Amato, Alex; Biswas, Pabitra K; Rüegg, Christian; Susner, Michael A; Sefat, Athena S; Zhigadlo, Nikolai D; Morenzoni, Elvezio

    2015-09-08

    The recent discovery of pressure (p) induced superconductivity in the binary helimagnet CrAs has raised questions on how superconductivity emerges from the magnetic state and on the mechanism of the superconducting pairing. In the present work the suppression of magnetism and the occurrence of superconductivity in CrAs were studied by means of muon spin rotation. The magnetism remains bulk up to p ≃ 3.5 kbar while its volume fraction gradually decreases with increasing pressure until it vanishes at p ≃ 7 kbar. At 3.5 kbar superconductivity abruptly appears with its maximum Tc ≃ 1.2 K which decreases upon increasing the pressure. In the intermediate pressure region (3.5 superconducting and the magnetic volume fractions are spatially phase separated and compete for phase volume. Our results indicate that the less conductive magnetic phase provides additional carriers (doping) to the superconducting parts of the CrAs sample thus leading to an increase of the transition temperature (Tc) and of the superfluid density (ρs). A scaling of ρs with Tc(3.2) as well as the phase separation between magnetism and superconductivity point to a conventional mechanism of the Cooper-pairing in CrAs.

  5. Effect of the Ni site substitution on superconducting properties of YNi 2B 2C

    Science.gov (United States)

    Bud'ko, S. L.; Elmassalami, M.; Fontes, M. B.; Mondragon, J.; Vanoni, W.; Giordanengo, B.; Baggio-Saitovitch, E. M.

    1995-02-01

    Structural and superconducting properties of Y(Ni 1- xM x) 2B 2C compounds with MCo, Fe and Ru have been studied. A fast decrease of Tc with the concentration of the dopants was found. This effect can be attributed to the shift of the Fermi level induced by the dopant concentration with the additional contributions from the chemical-pressure effects and from the decrease of the electronic mean free path.

  6. Structural, electronic, superconducting and mechanical properties of ReC and TcC

    Energy Technology Data Exchange (ETDEWEB)

    Kavitha, M.; Priyanga, G. Sudha; Rajeswarapalanichamy, R., E-mail: rajeswarapalanichamy@gmail.com; Santhosh, M. [Department of Physics, N.M.S.S.V.N College, Madurai, Tamilnadu-625019 (India)

    2015-06-24

    The structural, electronic, superconducting and mechanical properties of ReC and TcC are investigated using density functional theory calculations. The lattice constants, bulk modulus, and the density of states are obtained. The calculated lattice parameters are in good agreement with the available results. The density of states reveals that ReC and TcC exhibit metallic behavior at ambient condition. A pressure-induced structural phase transition is observed in both materials.

  7. Structural, electronic, superconducting and mechanical properties of ReC and TcC

    Science.gov (United States)

    Kavitha, M.; Priyanga, G. Sudha; Rajeswarapalanichamy, R.; Santhosh, M.

    2015-06-01

    The structural, electronic, superconducting and mechanical properties of ReC and TcC are investigated using density functional theory calculations. The lattice constants, bulk modulus, and the density of states are obtained. The calculated lattice parameters are in good agreement with the available results. The density of states reveals that ReC and TcC exhibit metallic behavior at ambient condition. A pressure-induced structural phase transition is observed in both materials.

  8. Superconducting properties of Tl-Ba-Ca-Cu-O films on silver substrates

    Energy Technology Data Exchange (ETDEWEB)

    Dye, R.C.; Arendt, P.N.; Martin, J.A.; Hubbard, K.M.; Elliott, N.; Reeves, G. (Los Alamos National Lab., NM (United States))

    1991-03-01

    Films of Ba-Ca-Cu-O have been rf magnetron sputtered onto Consil 995 substrates. A post deposition anneal in an over pressure of Tl produces the superconducting 1212 and 2212 phases. Varying the annealing procedures changes the electrical properties of the final films dramatically. Dynamic impedance, an approach to the electrical characterization of these films on a conductive substrate is discussed and compared in this paper, with SEM, XRD and RBS measurements as a function of differing annealing protocols.

  9. Superconducting properties of Tl-Ba-Ca-Cu-O films on silver substrates

    Energy Technology Data Exchange (ETDEWEB)

    Dye, R.C.; Arendt, P.N.; Martin, J.A.; Hubbard, K.M.; Elliott, N.; Reeves, G.

    1990-01-01

    Films of Ba-Ca-Cu-O have been rf magnetron sputtered onto Consil 995 substrates. A post deposition anneal in an over pressure of Tl produces the superconducting 1212 and 2212 phases. Varying the annealing procedures changes the electrical properties of the final films dramatically. Dynamic impedance, a novel approach to the electrical characterization of these films on a conductive substrate is discussed and compared with SEM, XRD and RBS measurements as a function of differing annealing protocols. 3 refs., 9 figs.

  10. Superconducting properties of MgB2 from first principles.

    Science.gov (United States)

    Floris, A; Profeta, G; Lathiotakis, N N; Lüders, M; Marques, M A L; Franchini, C; Gross, E K U; Continenza, A; Massidda, S

    2005-01-28

    Solid MgB(2) has rather interesting and technologically important properties, such as a very high superconducting transition temperature. Focusing on this compound, we report the first nontrivial application of a novel density-functional-type theory for superconductors, recently proposed by the authors. Without invoking any adjustable parameters, we obtain the transition temperature, the gaps, and the specific heat of MgB(2) in very good agreement with experiment. Moreover, our calculations show how the Coulomb interaction acts differently on sigma and pi states, thereby stabilizing the observed superconducting phase.

  11. Proximity Induced Superconducting Properties in One and Two Dimensional Semiconductors

    DEFF Research Database (Denmark)

    Kjærgaard, Morten

    that a superconducting 1D nanowire can harbor Majorana bound states in the absence of spin–orbit coupling. We fabricate and measure micrometer–sized mesoscopic devices demonstrating the inheritance of superconducting properties in the 2D electron gas. By placing a quantum point contact proximal to the interface between...... the 2D electron gas and the aluminum, we are able to demonstrate quantization of conductance in units of 4e2/h indicative of perfect Andreev reflection at the interface. We show that the quantum point contact can be operated as a tunnel probe to locally measure the density of states in the electron gas...... with a superconducting pairing potential, Majorana bound states can exist in the absence of spin–orbit coupling. Our proposal dispenses with spin–orbit coupling at the expense of a locally varying magnetic field. The presence of the topological state is demonstrated analytically by mapping our model onto...

  12. Topological quantum phase transition and superconductivity induced by pressure in the bismuth tellurohalide BiTeI

    OpenAIRE

    Qi, Yanpeng; Shi, Wujun; Naumov, Pavel G.; Kumar, Nitesh; Sankar, Raman; Schnelle, Walter; Shekhar, Chandra; Chou, F. C.; Felser, Claudia; Yan, Binghai; Medvedev, Sergey A.

    2016-01-01

    A pressure-induced topological quantum phase transition has been theoretically predicted for the semiconductor BiTeI with giant Rashba spin splitting. In this work, the evolution of the electrical transport properties in BiTeI and BiTeBr is investigated under high pressure. The pressure-dependent resistivity in a wide temperature range passes through a minimum at around 3 GPa, indicating the predicted transition in BiTeI. Superconductivity is observed in both BiTeI and BiTeBr while the resist...

  13. Superconductivity

    Science.gov (United States)

    1989-07-01

    SUPERCONDUCTIVITY HIGH-POWER APPLICATIONS Electric power generation/transmission Energy storage Acoustic projectors Weapon launchers Catapult Ship propulsion • • • Stabilized...temperature superconductive shields could be substantially enhanced by use of high-Tc materials. 27 28 NRAC SUPERCONDUCTIVITY SHIP PROPULSION APPLICATIONS...motor shown in the photograph. As a next step in the evolution of electric-drive ship propulsion technology, DTRC has proposed to scale up the design

  14. Superconductivity in the doped topological insulator CuxBi2Se3 under high pressure

    NARCIS (Netherlands)

    Bay, T.V.; Naka, T.; Huang, Y.K.; Luigjes, H.; Golden, M.S.; de Visser, A.

    2012-01-01

    We report a high-pressure single crystal study of the topological superconductor CuxBi2Se3. Resistivity measurements under pressure show superconductivity is depressed smoothly. At the same time the metallic behavior is gradually lost. The upper-critical field data Bc2(T) under pressure collapse ont

  15. Superconductivity in hydrogen-rich materials at high pressures

    Energy Technology Data Exchange (ETDEWEB)

    Drozdov, Alexander

    2016-07-01

    A room temperature superconductor is probably one of the most desired systems in solid state physics. The highest critical temperature (T{sub c}) that has been achieved so far is in the copper oxide system: 133 kelvin (K) at ambient pressure ([82]Schilling et al. 1993) and 160 K under pressure ([42]Gao et al. 1994). The nature of superconductivity in the cuprates and in the recently discovered iron-based superconductor family (T{sub c}=57 K) is still not fully understood. In contrast, there is a class of superconductors which is well-described by the Bardeen, Cooper, Schrieffer (BCS) theory - conventional superconductors. Great efforts were spent in searching for high-temperature (T{sub c} > 77 K) conventional superconductor but only T{sub c} = 39 K has been reached in MgB2 ([68]Nagamatsu et al. 2001). BCS theory puts no bounds for T{sub c} as follows from Eliashberg's formulation of BCS theory. T{sub c} can be high, if there is a favorable combination of high-frequency phonons, strong electron-phonon coupling, and a high density of states. It does not predict however in which materials all three parameters are large. At least it gives a clear indication that materials with light elements are favorable as light elements provide high frequencies in the phonon spectrum. The lightest element is hydrogen, and Ashcroft made a first prediction that metallic hydrogen will be a high-temperature superconductor ([6]Ashcroft 1968). As pressure of hydrogen metallization was too high (about 400-500 GPa) for experimental techniques then he proposed that compounds dominated by hydrogen (hydrides) also might be good high temperature superconductors ([6]Ashcroft 1968; [7]Ashcroft 2004). A lot of the followed calculations supported this idea. T{sub c} in the range of 50-235 kelvin was predicted for many hydrides. Unfortunately, only a moderate T{sub c} of 17 kelvin has been observed experimentally ([27]Eremets et al. 2008) so far. A goal of the present work is to find a

  16. Levitation pressure and friction losses in superconducting bearings

    Energy Technology Data Exchange (ETDEWEB)

    Hull, John R. (Downers Grove, IL)

    2001-01-01

    A superconducting bearing having at least one permanent magnet magnetized with a vertical polarization. The lower or stator portion of the bearing includes an array of high-temperature superconducting elements which are comprised of a plurality of annular rings. An annular ring is located below each permanent magnet and an annular ring is offset horizontally from at least one of the permanent magnets. The rings are composed of individual high-temperature superconducting elements located circumferentially along the ring. By constructing the horizontally-offset high-temperature superconducting ring so that the c-axis is oriented in a radial direction, a higher levitation force can be achieved. Such an orientation will also provide substantially lower rotational drag losses in the bearing.

  17. Levitation pressure and friction losses in superconducting bearings

    Science.gov (United States)

    Hull, John R.

    2001-01-01

    A superconducting bearing having at least one permanent magnet magnetized with a vertical polarization. The lower or stator portion of the bearing includes an array of high-temperature superconducting elements which are comprised of a plurality of annular rings. An annular ring is located below each permanent magnet and an annular ring is offset horizontally from at least one of the permanent magnets. The rings are composed of individual high-temperature superconducting elements located circumferentially along the ring. By constructing the horizontally-offset high-temperature superconducting ring so that the c-axis is oriented in a radial direction, a higher levitation force can be achieved. Such an orientation will also provide substantially lower rotational drag losses in the bearing.

  18. Proximity Induced Superconducting Properties in One and Two Dimensional Semiconductors

    DEFF Research Database (Denmark)

    Kjærgaard, Morten

    a voltage is passed through the Josephson junction, we observe multiple Andreev reflections and preliminary results point to a highly transmissive interface between the 2D electron gas and the superconductor. In the theoretical section we demonstrate analytically and numerically, that in a 1D nanowire......This report is concerned with the properties of one and two dimensional semiconducting materials when brought into contact with a superconductor. Experimentally we study the 2D electron gas in an InGaAs/InAs heterostructure with aluminum grown in situ on the surface, and theoretically we show...... that a superconducting 1D nanowire can harbor Majorana bound states in the absence of spin–orbit coupling. We fabricate and measure micrometer–sized mesoscopic devices demonstrating the inheritance of superconducting properties in the 2D electron gas. By placing a quantum point contact proximal to the interface between...

  19. Effect of pelletization pressure on structural properties and critical current hysteresis of ceramic superconducting Bi sub 1 sub . sub 7 Pb sub 0 sub . sub 3 Sr sub 2 Ca sub 2 Cu sub 3 O sub y

    CERN Document Server

    Tepe, M; Abukay, D

    2003-01-01

    The effect of pelletization pressures on structural properties and critical current hysteresis of Bi sub 1 sub . sub 7 Pb sub 0 sub . sub 3 Sr sub 2 Ca sub 2 Cu sub 3 O sub y samples was investigated. The samples used in this study were prepared by classical solid-state reaction at the pressures from 100 up to 500 MPa. The obtained samples were characterized by resistance vs. temperature, (R-T), critical current density vs. applied magnetic field, (J sub c -H), material density vs. pressure, (rho-P), XRD, SEM, and EDAX. The results of this study showed that the quality of electrical and structural properties of Bi-2223 bulk superconductors strongly depends on the pelletization pressure. Pressing of bulk samples at 400 MPa produces textured grain alignment and associates microstructural modifications in order to enhance flux pinning and thus increases current carrying capacities. (Abstract Copyright [2003], Wiley Periodicals, Inc.)

  20. Topological Quantum Phase Transition and Superconductivity Induced by Pressure in the Bismuth Tellurohalide BiTeI.

    Science.gov (United States)

    Qi, Yanpeng; Shi, Wujun; Naumov, Pavel G; Kumar, Nitesh; Sankar, Raman; Schnelle, Walter; Shekhar, Chandra; Chou, Fang-Cheng; Felser, Claudia; Yan, Binghai; Medvedev, Sergey A

    2017-03-06

    A pressure-induced topological quantum phase transition has been theoretically predicted for the semiconductor bismuth tellurohalide BiTeI with giant Rashba spin splitting. In this work, evolution of the electrical transport properties in BiTeI and BiTeBr is investigated under high pressure. The pressure-dependent resistivity in a wide temperature range passes through a minimum at around 3 GPa, indicating the predicted topological quantum phase transition in BiTeI. Superconductivity is observed in both BiTeI and BiTeBr, while resistivity at higher temperatures still exhibits semiconducting behavior. Theoretical calculations suggest that superconductivity may develop from the multivalley semiconductor phase. The superconducting transition temperature, Tc , increases with applied pressure and reaches a maximum value of 5.2 K at 23.5 GPa for BiTeI (4.8 K at 31.7 GPa for BiTeBr), followed by a slow decrease. The results demonstrate that BiTeX (X = I, Br) compounds with nontrivial topology of electronic states display new ground states upon compression.

  1. Introduction to Superconducting RF Structures and the Effect of High Pressure Rinsing

    Energy Technology Data Exchange (ETDEWEB)

    Tajima, Tsuyoshi [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-06-30

    This presentation begins by describing RF superconductivity and SRF accelerating structures. Then the use of superconducting RF structures in a number of accelerators around the world is reviewed; for example, the International Linear Collider (ILC) will use ~16,000 SRF cavities with ~2,000 cryomodules to get 500 GeV e⁺/e⁻ colliding energy. Field emission control was (and still is) a very important practical issue for SRF cavity development. It has been found that high-pressure ultrapure water rinsing as a final cleaning step after chemical surface treatment resulted in consistent performance of single- and multicell superconducting cavities.

  2. Annealing condition dependence of the superconducting property and the pseudo-gap in the protect-annealed electron-doped cuprates

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Woo Been; Cho, Su Hyun; Kim, Chang Young [Center for Correlated Electron Systems, Institute for Basic Science, Seoul (Korea, Republic of); Song, Dong Joon [National Institute of Advanced Industrial Science and Technology, Tsukuba (Japan); Park, Seung Ryong [Dept. of Physics, Research Institute of Basic Sciences, Incheon National University, Incheon (Korea, Republic of)

    2016-06-15

    Annealing as-grown electron-doped cuprates under a low oxygen-partial-pressure condition is a necessary step to achieve superconductivity. It has been recently found that the so-called protect annealing results in much better superconducting properties in terms of the superconducting transition temperature and volume fraction. In this article, we report on angle-resolved photoemission spectroscopy studies of a protect-annealed electron-doped cuprate Pr0.9La1.0Ce0.1CuO4 on annealing condition dependent superconducting and pseudo-gap properties. Remarkably, we found that the one showing a better superconducting property possesses almost no pseudo-gap while others have strong pseudo-gap feature due to an anti-ferromagnetic order.

  3. Superconductivity

    CERN Document Server

    Ketterson, John B

    2008-01-01

    Conceived as the definitive reference in a classic and important field of modern physics, this extensive and comprehensive handbook systematically reviews the basic physics, theory and recent advances in the field of superconductivity. Leading researchers, including Nobel laureates, describe the state-of-the-art in conventional and unconventional superconductors at a particularly opportune time, as new experimental techniques and field-theoretical methods have emerged. In addition to full-coverage of novel materials and underlying mechanisms, the handbook reflects continued intense research into electron-phone based superconductivity. Considerable attention is devoted to high-Tc superconductivity, novel superconductivity, including triplet pairing in the ruthenates, novel superconductors, such as heavy-Fermion metals and organic materials, and also granular superconductors. What’s more, several contributions address superconductors with impurities and nanostructured superconductors. Important new results on...

  4. The Properties of Normal Conducting Cathodes in FZD Superconducting Gun

    CERN Document Server

    Xiang, R; Buettig, H; Janssen, D; Justus, M; Lehnert, U; Michel, P; Murcek, P; Schamlott, A; Schneider, Ch; Schurig, R; Staufenbiel, F; Teichert, J

    2009-01-01

    The superconducting radio frequency photoinjector (SRF photoinjector) is one of the latest applications of SC technology in the accelerator field. Since superconducting cathodes with high QE are not available up to now, normal conducting cathode material is the main choice for the SRF photoinjectors. However, the compatibility between the cathode and the cavity is one of the challenges for this concept. The SRF gun with Cs2Te cathode has been successfully operated under the collaboration of BESSY, DESY, FZD, and MBI. In this paper, some experience gained in the gun commissioning will be concluded. The results of the properties of Cs2Te photocathode in the cavity will be presented, such as the Q.E., the life time, the dark current and the thermal emittance.

  5. Effects of pressure and magnetic field on superconductivity in ZrTe3: local pair-induced superconductivity

    Science.gov (United States)

    Tsuchiya, S.; Matsubayashi, K.; Yamaya, K.; Takayanagi, S.; Tanda, S.; Uwatoko, Y.

    2017-06-01

    In this work, the origin of the highly anisotropic superconducting transition in ZrTe3, where the resistance along the a axis, R a , is reduced at 4 K but those along the b axis, R b , and {c}\\prime axis, R c‧, are reduced at 2 K, was explored with the application of a magnetic field and pressure by the electrical resistance measurements. We found that the behavior of the upper critical field and its anisotropy as well as the pressure dependence determined by the R a measurements are quite similar to those of R b . Moreover, the excess conductivity for R b indicates anomalous behavior. These results support an unconventional origin for the anisotropic transition rather than conventional superconducting fluctuation. The reduction in R a is due to filamentary superconductivity (SC) induced by locally bound electron pairs (local pairs), which correspond to bi-polarons, and the transition of R b corresponds to the emergence of bulk SC originating from the Cooper pairs triggered by the transfer of the local pairs.

  6. High pressure synthesis and superconducting properties for the multi-layered Ba{sub 2}Ca {sub n-1}Cu {sub n}O{sub 2n}(O,F){sub 2} (n = 4 and 5)

    Energy Technology Data Exchange (ETDEWEB)

    Kito, Hijiri [National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 2, 1-1-1, Umezono, Tsukuba, Ibaraki, 305-8568 (Japan)]. E-mail: h.kito@aist.go.jp; Iyo, Akira [National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 2, 1-1-1, Umezono, Tsukuba, Ibaraki, 305-8568 (Japan)

    2006-10-01

    We prepared multi-layered oxyfluoride superconductors, Ba{sub 2}Ca {sub n-1}Cu {sub n}O{sub 2n}(O,F){sub 2} (n = 4 and 5) using high-pressure apparatus. These phase are the n = 4 and 5 members of a homologous series, M{sub 2}Ca {sub n-1}Cu {sub n}O{sub 2n}(O,F){sub 2} [0{sup M}2(n - 1)n-F] reported previously. X-ray studies indicated that they have tetragonal structures with a = 3.863 A, c = 33.75 A for n = 4 and a = 3.862 A, c = 40.18 A for n = 5. Superconducting transition temperature were 86.6 K for n = 4 and 75.7 K for n = 5, respectively. The critical current density (J {sub c}) and irreversibility field (H {sub irr}) were determined from M-H curves using the Bean's model. J {sub c} and H {sub irr} of 0{sup Ba}2(n - 1)n-F (n = 4 and 5) decreased rapidly with increasing temperature. J {sub c} (5 K, 1 T) shows 1.70 x 10{sup 6} A/cm{sup 2} for n = 4 and 1.93 x 10{sup 5} A/cm{sup 2} for n = 5. The estimated values of H {sub irr} (5 K) are about 70 T for n = 4 and 17 T for n = 5.

  7. Robust antiferromagnetism preventing superconductivity in pressurized (Ba 0.61 K 0.39)Mn2Bi2.

    Science.gov (United States)

    Gu, Dachun; Dai, Xia; Le, Congcong; Sun, Liling; Wu, Qi; Saparov, Bayrammurad; Guo, Jing; Gao, Peiwen; Zhang, Shan; Zhou, Yazhou; Zhang, Chao; Jin, Shifeng; Xiong, Lun; Li, Rui; Li, Yanchun; Li, Xiaodong; Liu, Jing; Sefat, Athena S; Hu, Jiangping; Zhao, Zhongxian

    2014-12-05

    BaMn2Bi2 possesses an iso-structure of iron pnictide superconductors and similar antiferromagnetic (AFM) ground state to that of cuprates, therefore, it receives much more attention on its properties and is expected to be the parent compound of a new family of superconductors. When doped with potassium (K), BaMn2Bi2 undergoes a transition from an AFM insulator to an AFM metal. Consequently, it is of great interest to suppress the AFM order in the K-doped BaMn2Bi2 with the aim of exploring the potential superconductivity. Here, we report that external pressure up to 35.6 GPa cannot suppress the AFM order in the K-doped BaMn2Bi2 to develop superconductivity in the temperature range of 300 K-1.5 K, but induces a tetragonal (T) to an orthorhombic (OR) phase transition at ~20 GPa. Theoretical calculations for the T and OR phases, on basis of our high-pressure XRD data, indicate that the AFM order is robust in the pressurized Ba0.61K0.39Mn2Bi2. Both of our experimental and theoretical results suggest that the robust AFM order essentially prevents the emergence of superconductivity.

  8. Spiral magnetic order and pressure-induced superconductivity in transition metal compounds

    Science.gov (United States)

    Wang, Yishu; Feng, Yejun; Cheng, J.-G.; Wu, W.; Luo, J. L.; Rosenbaum, T. F.

    2016-10-01

    Magnetic and superconducting ground states can compete, cooperate and coexist. MnP provides a compelling and potentially generalizable example of a material where superconductivity and magnetism may be intertwined. Using a synchrotron-based non-resonant X-ray magnetic diffraction technique, we reveal a spiral spin order in MnP and trace its pressure evolution towards superconducting order via measurements in a diamond anvil cell. Judging from the magnetostriction, ordered moments vanish at the quantum phase transition as pressure increases the electron kinetic energy. Spins remain local in the disordered phase, and the promotion of superconductivity is likely to emerge from an enhanced coupling to residual spiral spin fluctuations and their concomitant suppression of phonon-mediated superconductivity. As the pitch of the spiral order varies across the 3d transition metal compounds in the MnP family, the magnetic ground state switches between antiferromagnet and ferromagnet, providing an additional tuning parameter in probing spin-fluctuation-induced superconductivity.

  9. Spiral magnetic order and pressure-induced superconductivity in transition metal compounds

    Science.gov (United States)

    Wang, Yishu; Feng, Yejun; Cheng, J.-G.; Wu, W.; Luo, J. L.; Rosenbaum, T. F.

    2016-01-01

    Magnetic and superconducting ground states can compete, cooperate and coexist. MnP provides a compelling and potentially generalizable example of a material where superconductivity and magnetism may be intertwined. Using a synchrotron-based non-resonant X-ray magnetic diffraction technique, we reveal a spiral spin order in MnP and trace its pressure evolution towards superconducting order via measurements in a diamond anvil cell. Judging from the magnetostriction, ordered moments vanish at the quantum phase transition as pressure increases the electron kinetic energy. Spins remain local in the disordered phase, and the promotion of superconductivity is likely to emerge from an enhanced coupling to residual spiral spin fluctuations and their concomitant suppression of phonon-mediated superconductivity. As the pitch of the spiral order varies across the 3d transition metal compounds in the MnP family, the magnetic ground state switches between antiferromagnet and ferromagnet, providing an additional tuning parameter in probing spin-fluctuation-induced superconductivity. PMID:27708255

  10. Properties of superconducting Bi-Sr-Ca-Cu-O system remelted under higher gravity conditions

    Science.gov (United States)

    Volkov, M. P.; Melekh, B. T.; Parfeniev, R. V.; Kartenko, N. F.; Regel, L. L.; Turchaninov, A. M.

    1992-04-01

    The structure and magnetic properties of high Tc superconductor Bi-Sr-Ca-Cu-O samples remelted under 1 g0, 8 g0 and 12 g0 gravity levels have been investigated. Superconducting properties make a change along the ingots. The dependence of structural and superconducting properties on the gravity level and their time degradation have been observed.

  11. A Simple System to Measure Superconducting Transition Temperature at High Pressure

    Institute of Scientific and Technical Information of China (English)

    YU Yong; ZHAI Guang-Jie; JIN Chang-Qing

    2009-01-01

    A simple hydride system is fabricated to measure the superconducting transition temperature Tc under high pressure using a diamond anvil cell (DAC). The system is designed with centrosymetric coils around the diamond that makes it easy to keep balance between the pick-up coil and the inductance coil, while the superconducting states can be modulated with a low-frequency small external magnetic field. Using the device we successfully obtain the Tc evolution as a function of applied pressure up to 10 GPa for YBa2 Cu3O6+δ superconductor single crystal.

  12. Dynamic studies on the influence of strain on superconducting properties using piezoelectric substrates

    Energy Technology Data Exchange (ETDEWEB)

    Trommler, Sascha; Huehne, Ruben; Iida, Kazumasa; Haindl, Silvia; Haenisch, Jens; Pahlke, Patrick; Thersleff, Thomas; Schultz, Ludwig; Holzapfel, Bernhard [IFW Dresden (Germany)

    2011-07-01

    The interplay between structural parameters and superconducting properties attracts high interest in particular regarding the iron based superconductors. In contrast to the cuprate family, superconductivity of the latter can be induced using either pressure or chemical substitution. Nevertheless little is known about this relationship when biaxial strain is applied. The generation of biaxial strain by the preparation of thin films on substrates with different lattice mismatch is well established for cuprates. However, high quality films are necessary to correlate structural changes with electronic properties. In this work an alternative approach is used. Single crystalline piezoelectric substrates offer the unique opportunity to tune the lattice parameters continuously using the inverse piezoelectric effect. We prepared thin epitaxial La{sub 1-x}Sr{sub x}CuO{sub 4} and BaFe{sub 2-x}Co{sub x}As{sub 2} films on piezoelectric (001) Pb(Mg{sub 1/3}Nb{sub 2/3}){sub 0.72}Ti{sub 0.28}O{sub 3} (PMN-PT) substrates. A reversible shift of the superconducting transition has been achieved with a value of 0.44 K for La{sub 1.85}Sr{sub 0.15}CuO{sub 4} and 0.2 K for BaFe{sub 1.8}Co{sub 0.2}As{sub 2} for a biaxial strain of 0.022% and 0.017%, respectively.

  13. Properties of superconductivity on a density wave background with small ungapped Fermi surface parts

    Science.gov (United States)

    Grigoriev, P. D.

    2008-06-01

    We investigate the properties and the microscopic structure of superconductivity (SC) coexisting and sharing the common conducting band with density wave (DW). Such coexistence may take place when the nesting of the Fermi surface (FS) is not perfect, and in the DW state some quasiparticle states remain on the Fermi level and lead to the Cooper instability. The dispersion of such quasiparticle states strongly differs from that without DW, and so do the properties of SC on the DW background. The upper critical field Hc2 in such a SC state increases as the system approaches the critical pressure, where the ungapped quasiparticles and superconductivity just appear, and it may considerably exceed the usual Hc2 value without DW. The spin-density wave (SDW) background strongly suppresses the singlet SC pairing, while it does not affect so much the triplet SC transition temperature. The results obtained explain the experimental observations in layered organic metals (TMTSF)2PF6 and α-(BEDT-TTF)2KHg(SCN)4 , where SC appears in the DW states under pressure and shows many unusual properties.

  14. High-pressure study of the new Y-Ba-Cu-O superconducting compound system

    Science.gov (United States)

    Hor, P. H.; Gao, L.; Meng, R. L.; Huang, Z. J.; Wang, Y. Q.

    1987-01-01

    Hydrostatic effects on the superconducting transition temperature of the Y-Ba-Cu-O compound system, resistively, up to 19 kbar are investigated. It is found that pressure has little effect on the superconducting state of Y-Ba-Cu-O, in marked contrast to the behavior of the K2NiF4-phase La-Ba-Cu-O and La-Sr-Cu-O systems. It is suggested that this effect may be due to chemical pressure associated with the smaller Y atoms already present in Y-Ba-Cu-O. X-ray powder-diffraction studies show that the high-temperature superconductivity in Y-Ba-Cu-O can only be attributed to one or more phases with structures different from the cubic perovskite or tetragonal layered ones.

  15. Dome-shaped magnetic order competing with high-temperature superconductivity at high pressures in FeSe.

    Science.gov (United States)

    Sun, J P; Matsuura, K; Ye, G Z; Mizukami, Y; Shimozawa, M; Matsubayashi, K; Yamashita, M; Watashige, T; Kasahara, S; Matsuda, Y; Yan, J-Q; Sales, B C; Uwatoko, Y; Cheng, J-G; Shibauchi, T

    2016-07-19

    The coexistence and competition between superconductivity and electronic orders, such as spin or charge density waves, have been a central issue in high transition-temperature (Tc) superconductors. Unlike other iron-based superconductors, FeSe exhibits nematic ordering without magnetism whose relationship with its superconductivity remains unclear. Moreover, a pressure-induced fourfold increase of Tc has been reported, which poses a profound mystery. Here we report high-pressure magnetotransport measurements in FeSe up to ∼15 GPa, which uncover the dome shape of magnetic phase superseding the nematic order. Above ∼6 GPa the sudden enhancement of superconductivity (Tc≤38.3 K) accompanies a suppression of magnetic order, demonstrating their competing nature with very similar energy scales. Above the magnetic dome, we find anomalous transport properties suggesting a possible pseudogap formation, whereas linear-in-temperature resistivity is observed in the normal states of the high-Tc phase above 6 GPa. The obtained phase diagram highlights unique features of FeSe among iron-based superconductors, but bears some resemblance to that of high-Tc cuprates.

  16. Evaluating Superconducting YBCO Film Properties Using X-Ray Photoelectron Spectroscopy (Postprint)

    Science.gov (United States)

    2012-02-01

    AFRL-RZ-WP-TP-2012-0093 EVALUATING SUPERCONDUCTING YBCO FILM PROPERTIES USING X-RAY PHOTOELECTRON SPECTROSCOPY (POSTPRINT) Paul N. Barnes...2012 Conference Paper Postprint 01 January 2002 – 01 January 2004 4. TITLE AND SUBTITLE EVALUATING SUPERCONDUCTING YBCO FILM PROPERTIES USING X-RAY

  17. Superconducting properties of lithium-decorated bilayer graphene

    Science.gov (United States)

    Szczȩśniak, Dominik

    2015-07-01

    The present study provides a comprehensive theoretical analysis of the superconducting phase in selected lithium-decorated bilayer graphene nanostructures. The numerical calculations, conducted within the Eliashberg formalism, give quantitative estimations of the most important thermodynamic properties such as the critical temperature, specific heat, critical field and others. It is shown that discussed lithium-graphene systems present enhancement of their thermodynamic properties comparing to the monolayer case, e.g., the critical temperature can be raised to ∼15 \\text{K} . Furthermore, estimated characteristic thermodynamic ratios exceed predictions of the Bardeen-Cooper-Schrieffer theory suggesting that the considered lithium-graphene systems can be properly analyzed only within the strong-coupling regime.

  18. Synthesis and superconducting properties of the iron oxyarsenide TbFeAsO0.85

    OpenAIRE

    Shi, Y G; Yu, S.; Belik, A. A.; Matsushita, Y; Tanaka, M.; Katsuya, Y.; KOBAYASHI, K.; Yamaura, K.; Takayama-Muromachi, E.

    2008-01-01

    The iron oxyarsenide TbFeAsO0.85 was synthesized by a high-pressure method. A high-quality polycrystalline sample was obtained and characterized by measurements of magnetic susceptibility and electrical resistivity. Bulk superconductivity with Tc of 42 K was clearly established without an F doping usually conducted to tune on superconductivity in the iron oxypnictide.

  19. Superconductivity of Cu/CuOx interface formed by shock-wave pressure

    Science.gov (United States)

    Shakhray, D. V.; Avdonin, V. V.; Palnichenko, A. V.

    2016-11-01

    A mixture of powdered Cu and CuO has been subjected to shock-wave pressure of 350 kbar with following quenching of the vacuum-encapsulated product to 77 K. The ac magnetic susceptibility measurements of the samples have revealed metastable superconductivity with Tc ≈ 19 K, characterized by glassy dynamics of the shielding currents below Tc . Comparison of the ac susceptibility and the DC magnetization measurements infers that the superconductivity arises within the granular interfacial layer formed between metallic Cu and its oxides due to the shock-wave treatment.

  20. Universal limiting pressure for a three-flavor color superconducting PNJL model phase diagram

    CERN Document Server

    Ayriyan, A; Blaschke, D; Lastowiecki, R

    2016-01-01

    The phase diagram of a three-flavor Polyakov-loop Nambu-Jona-Lasinio model is analyzed for the case of isospin symmetric matter with color superconducting phases. The coexistence of chiral symmetry breaking and two-flavor color superconductivity (2SC phase) and a thermodynamic instability due to the implementation of a color neutrality constraint is observed. It is suggested to use a universal hadronization pressure to estimate the phase border between hadronic and quark-gluon plasma phases. Trajectories of constant entropy per baryon are analyzed for conditions appropriate for heavy-ion collisions in the NICA-FAIR energy range.

  1. Pressure-enhanced superconductivity in Eu3Bi2S4F4

    Science.gov (United States)

    Luo, Yongkang; Zhai, Hui-Fei; Zhang, Pan; Xu, Zhu-An; Cao, Guang-Han; Thompson, J. D.

    2014-12-01

    The pressure effect on the newly discovered charge-transferred BiS2-based superconductor, Eu3Bi2S4F4 , with a Tc of 1.5 K at ambient pressure, is investigated by transport and magnetic measurements. Accompanied with the enhancement of metallicity under pressures, the onset superconducting transition temperature increases abruptly around 1.0 GPa, reaching ˜10.0 K at 2.26 GPa. Alternating current magnetic susceptibility measurements indicate that a new superconducting phase with a higher Tc emerges and dominates at high pressures. In the broad pressure window of 0.68 GPa≤p ≤2.00 GPa, the high-Tc phase coexists with the low-Tc phase. Hall effect measurements reveal a significant difference in electronic structures between the two superconducting phases. Our work devotes the effort to establish the commonality of pressure effect on the BiS2-based superconductors, and also uncovers the importance of electron carrier density in the high-Tc phase.

  2. Nitrogen oxides under pressure: stability, ionization, polymerization, and superconductivity.

    Science.gov (United States)

    Li, Dongxu; Oganov, Artem R; Dong, Xiao; Zhou, Xiang-Feng; Zhu, Qiang; Qian, Guangrui; Dong, Huafeng

    2015-11-17

    Nitrogen oxides are textbook class of molecular compounds, with extensive industrial applications. Nitrogen and oxygen are also among the most abundant elements in the universe. We explore the N-O system at 0 K and up to 500 GPa though ab initio evolutionary simulations. Results show that two phase transformations of stable molecular NO2 occur at 7 and 64 GPa, and followed by decomposition of NO2 at 91 GPa. All of the NO(+)NO3(-) structures are found to be metastable at T = 0 K, so experimentally reported ionic NO(+)NO3(-) is either metastable or stabilized by temperature. N2O5 becomes stable at 9 GPa, and transforms from P-1 to C2/c structure at 51 GPa. NO becomes thermodynamically stable at 198 GPa. This polymeric phase is superconducting (Tc = 2.0 K) and contains a -N-N- backbone.

  3. Direct observation of a helical magnetic order near the superconducting state of MnP under pressure

    Science.gov (United States)

    Wang, Yishu; Feng, Yejun; Cheng, J.-G.; Rosenbaum, T. F.

    A recent high-pressure electrical transport study of the 3d transition metal compound MnP manifested a complex pressure-temperature phase diagram of different types of magnetism and superconductivity. However, the nature of the high-pressure magnetic phase proximate to the superconducting state was not determined. We use non-resonant X-ray magnetic diffraction to probe the magnetic order in MnP under pressure. We discover incommensurate helical order in a confined region under high pressure, and ascertain the phase boundary through the pressure evolution of the lattice. Although the antiferromagnetic and superconducting phases are separated, there is no signature of a strong first-order phase transition between them. We discuss how our direct observation of a helimagnetic order in MnP helps to better understand aspects of magnetically-mediated superconductivity.

  4. Superconducting and normal-state properties of novel materials

    Energy Technology Data Exchange (ETDEWEB)

    Crespi, Vincent Henry [Univ. of California, Berkeley, CA (United States)

    1994-09-01

    Interest in solid state physics naturally gravitates towards novel systems such as the copper oxide superconductors or the alkali-doped fullerenes. This paper tackles high temperature superconductivity by extension of the BCS theory for ordinary superconductors, in particular, incorporation of anharmonicity in phonon dynamics and anisotropy in electron-phonon coupling. These refinements can account for many anomalous properties of the cuprates. Phonon anharmonicity is consistent with a small isotope effect at optimal doping and a larger isotope effect in suboptimal systems. Anisotropy in the interaction, a plausible consequence of certain anharmonic models, can circumvent objections to electron-phonon coupling based on transport measurements. Such anisotropy is consistent with gap anisotropy and strong temperature dependence of Hall coefficient. In contrast to cuprates, the doped fullerenes appear understandable within the standard model of single electron band theory and BCS theory. Microscopic parameters derivable from transport and critical field measurements yield a self-consistent picture of a disordered Type-2 BCS superconductor. Isotope effects imply that superconductivity is mediated by carbon phonons opposed to alkali atom vibrations. The novel properties of the fullerenes are generally traceable to their microscopic heterogeneity, being a collection of tightly bound but weakly overlapping molecules. Separation of electronic regimes into weak intermolecular overlap and strong carbon-carbon on-ball bonds yields a superconductor with both a large density of states and a high phonon frequency, properties consistent with a relatively high {Tc}. Disordered nature of intermolecular overlap produces a large residual resistivity and a universal dependence to the Hall coefficient. This disorder is also consistent with the anomalously large carbon isotope effect for heterogeneous isotopic substitution.

  5. Superconductivity of k-(BEDT-TTF) sub 2 Cu[N(CN) sub 2]I under pressure

    CERN Document Server

    Kushch, N D; Yagubskii, E B; Ishiguro, T

    2001-01-01

    The insulating state of k-(BEDT-TTF) sub 2 Cu[N(CN) sub 2]I salt appearing at ambient pressure at low temperatures is suppressed by hydrostatic pressure. The resistive measurement showed that in high-quality crystals the emerging metallic state reveals superconductivity. The superconducting state with the transition temperature of about 8 K is stable at pressures higher than 0.1 GPa

  6. Pressure Induced Enhancement of Superconductivity in LaRu2P2

    Science.gov (United States)

    Li, Baoxuan; Lu, Pengchao; Liu, Jianzhong; Sun, Jian; Li, Sheng; Zhu, Xiyu; Wen, Hai-Hu

    2016-04-01

    To explore new superconductors beyond the copper-based and iron-based systems is very important. The Ru element locates just below the Fe in the periodic table and behaves like the Fe in many ways. One of the common thread to induce high temperature superconductivity is to introduce moderate correlation into the system. In this paper, we report the significant enhancement of superconducting transition temperature from 3.8 K to 5.8 K by using a pressure only of 1.74 ± 0.05 GPa in LaRu2P2 which has an iso-structure of the iron-based 122 superconductors. The ab-initio calculation shows that the superconductivity in LaRu2P2 at ambient pressure can be explained by the McMillan’s theory with strong electron-phonon coupling. However, it is difficult to interpret the enhancement of Tc versus pressure within this picture. Detailed analysis of the pressure induced evolution of resistivity and upper critical field Hc2(T) reveals that the increase of Tc with pressure may be accompanied by the involvement of extra electron-boson interaction. This suggests that the Ru-based system has some commonality as the Fe-based superconductors.

  7. Mechanical, electronic, optical, thermodynamic properties and superconductivity of ScGa3

    Science.gov (United States)

    Parvin, F.; Hossain, M. A.; Ali, M. S.; Islam, A. K. M. A.

    2015-01-01

    The rare occurrence of type-I superconductivity in binary system ScGa3 has experimentally been shown recently. In the present paper we study the electronic, optical, thermodynamic properties and some aspects of superconductivity of this compound using first-principles calculations. The mechanical properties like elastic constants, bulk modulus, shear modulus, Pugh's ductility index, Young's modulus, Poisson's ratio, elastic anisotropy factor, Peierls stress are calculated for the first time. The material is anisotropic and brittle. Electronic band structure, density of states, Fermi surfaces and bonding nature have also been studied. The optical functions are estimated and discussed for the first time. The high reflectivity is found in the ultraviolet regions up to ~13 eV and thus ScGa3 can serve as a possible shielding material for ultraviolet radiation. Thermal effects on some macroscopic properties of ScGa3 are predicted using the quasi-harmonic Debye model and phonon approximation in the temperature and hydrostatic pressure in the ranges of 0-1000 K and 0-40 GPa, respectively. The calculated electron-phonon coupling constant λ=0.52 yields Tc=2.6 K, which is in very good agreement with the experimentally observed value. The value of the coupling constant and the Ginzburg-Landau parameter (κ=0.09) indicate that the compound is a weak-coupled type-I rare binary BCS superconductor.

  8. Mechanical, electronic, optical, thermodynamic properties and superconductivity of ScGa{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Parvin, F. [Department of Physics, Rajshahi University, Rajshahi (Bangladesh); Hossain, M.A. [Department of Physics, Mawlana Bhashani Science and Technology University, Santosh, Tangail 1902 (Bangladesh); Ali, M.S. [Department of Physics, Rajshahi University, Rajshahi (Bangladesh); Islam, A.K.M.A., E-mail: azi46@ru.ac.bd [International Islamic University Chittagong, 154/A College Road, Chittagong 4203 (Bangladesh)

    2015-01-15

    The rare occurrence of type-I superconductivity in binary system ScGa{sub 3} has experimentally been shown recently. In the present paper we study the electronic, optical, thermodynamic properties and some aspects of superconductivity of this compound using first-principles calculations. The mechanical properties like elastic constants, bulk modulus, shear modulus, Pugh's ductility index, Young's modulus, Poisson's ratio, elastic anisotropy factor, Peierls stress are calculated for the first time. The material is anisotropic and brittle. Electronic band structure, density of states, Fermi surfaces and bonding nature have also been studied. The optical functions are estimated and discussed for the first time. The high reflectivity is found in the ultraviolet regions up to ∼13 eV and thus ScGa{sub 3} can serve as a possible shielding material for ultraviolet radiation. Thermal effects on some macroscopic properties of ScGa{sub 3} are predicted using the quasi-harmonic Debye model and phonon approximation in the temperature and hydrostatic pressure in the ranges of 0–1000 K and 0–40 GPa, respectively. The calculated electron–phonon coupling constant λ=0.52 yields T{sub c}=2.6 K, which is in very good agreement with the experimentally observed value. The value of the coupling constant and the Ginzburg–Landau parameter (κ=0.09) indicate that the compound is a weak-coupled type-I rare binary BCS superconductor.

  9. Tuning the electronic and the crystalline structure of LaBi by pressure: From extreme magnetoresistance to superconductivity

    Energy Technology Data Exchange (ETDEWEB)

    Tafti, F. F.; Torikachvili, M. S.; Stillwell, R. L.; Baer, B.; Stavrou, E.; Weir, S. T.; Vohra, Y. K.; Yang, H. -Y.; McDonnell, E. F.; Kushwaha, S. K.; Gibson, Q. D.; Cava, R. J.; Jeffries, J. R.

    2017-01-01

    Extreme magnetoresistance (XMR) in topological semimetals is a recent discovery which attracts attention due to its robust appearance in a growing number of materials. To search for a relation between XMR and superconductivity, we study the effect of pressure on LaBi. By increasing pressure, we observe the disappearance of XMR followed by the appearance of superconductivity at P ≈ 3.5 GPa. We find a region of coexistence between superconductivity and XMR in LaBi in contrast to other superconducting XMR materials. The suppression of XMR is correlated with increasing zero-field resistance instead of decreasing in-field resistance. At higher pressures, P ≈ 11 GPa, we find a structural transition from the face-centered cubic lattice to a primitive tetragonal lattice, in agreement with theoretical predictions. The relationship between extreme magnetoresistance, superconductivity, and structural transition in LaBi is discussed.

  10. Conventional superconductivity at 203 kelvin at high pressures in the sulfur hydride system.

    Science.gov (United States)

    Drozdov, A P; Eremets, M I; Troyan, I A; Ksenofontov, V; Shylin, S I

    2015-09-03

    A superconductor is a material that can conduct electricity without resistance below a superconducting transition temperature, Tc. The highest Tc that has been achieved to date is in the copper oxide system: 133 kelvin at ambient pressure and 164 kelvin at high pressures. As the nature of superconductivity in these materials is still not fully understood (they are not conventional superconductors), the prospects for achieving still higher transition temperatures by this route are not clear. In contrast, the Bardeen-Cooper-Schrieffer theory of conventional superconductivity gives a guide for achieving high Tc with no theoretical upper bound--all that is needed is a favourable combination of high-frequency phonons, strong electron-phonon coupling, and a high density of states. These conditions can in principle be fulfilled for metallic hydrogen and covalent compounds dominated by hydrogen, as hydrogen atoms provide the necessary high-frequency phonon modes as well as the strong electron-phonon coupling. Numerous calculations support this idea and have predicted transition temperatures in the range 50-235 kelvin for many hydrides, but only a moderate Tc of 17 kelvin has been observed experimentally. Here we investigate sulfur hydride, where a Tc of 80 kelvin has been predicted. We find that this system transforms to a metal at a pressure of approximately 90 gigapascals. On cooling, we see signatures of superconductivity: a sharp drop of the resistivity to zero and a decrease of the transition temperature with magnetic field, with magnetic susceptibility measurements confirming a Tc of 203 kelvin. Moreover, a pronounced isotope shift of Tc in sulfur deuteride is suggestive of an electron-phonon mechanism of superconductivity that is consistent with the Bardeen-Cooper-Schrieffer scenario. We argue that the phase responsible for high-Tc superconductivity in this system is likely to be H3S, formed from H2S by decomposition under pressure. These findings raise hope for the

  11. Pressure-enhanced superconductivity in A15-type Nb3 Ge via increased Fermi surface nesting

    Science.gov (United States)

    Stillwell, Ryan; Jeffries, Jason; McCall, Scott; Jenei, Zsolt; Weir, Sam; Vohra, Yogesh

    The A15-type superconductors are the most widely used superconductors in industrial applications yet the physics behind maximizing the superconducting transition temperature is still not completely understood. The highest transition temperatures found to date have recently been reported for high-pressure hydride materials and it is believed that they too are BCS-type phonon-mediated superconductors, just like the A15-type superconductors. Understanding the electron-phonon coupling has therefore been brought front stage in the search to understand the mechanisms for optimizing high-temperature superconductors. Using a multi-faceted suite of high-pressure techniques we found that Nb3Ge has an isostructural phase transition at high pressure that correlates directly with a bandstructure change seen in high-pressure magnetotransport measurements. Our results suggest that A15-type superconductivity is not only phonon-mediated but that the degree of Fermi surface nesting is a controlling parameter for maximizing the superconducting transition temperature. Lawrence Livermore National Laboratory is operated by Lawrence Livermore National Security, LLC, for the U.S. Department of Energy, National Nuclear Security Administration under Contract DE-AC52-07NA27344.

  12. Properties of superconducting Bi-Sr-Ca-Cu-O system remelted under higher gravity conditions

    Energy Technology Data Exchange (ETDEWEB)

    Volkov, M.P.; Melekh, B.T.; Parfeniev, R.V.; Kartenko, N.F. (A.F. Ioffe Physical Technical Inst., Academy of Sciences, Moscow (Russia)); Regel, L.L.; Turchaninov, A.M. (Space Research Inst., Academy of Sciences, Moscow (Russia))

    1992-04-01

    The structure and magnetic properties of high Tc superconductor Bi-Sr-Ca-Cu-O samples remelted under 1g{sub 0}, 8g{sub 0} and 12g{sub 0} gravity levels have been investigated. Superconducting properties make a change along the ingots. The dependence of structural and superconducting properties on the gravity level and their time degradation have been observed. (orig.).

  13. Intercalated Nanocomposites Based on High-Temperature Superconducting Ceramics and Their Properties

    Directory of Open Access Journals (Sweden)

    Sevan Davtyan

    2009-12-01

    Full Text Available High temperature superconducting (SC nanocomposites based on SC ceramics and various polymeric binders were prepared. Regardless of the size of the ceramics’ grains, the increase of their amount leads to an increase of resistance to rupture and modulus and a decrease in limiting deformation, whereas an increase in the average ceramic grain size worsens resistance properties. The SC, thermo-chemical, mechanical and dynamic-mechanical properties of the samples were investigated. Superconducting properties of the polymer ceramic nanocomposites are explained by intercalation of macromolecule fragments into the interstitial layer of the ceramics’ grains. This phenomenon leads to a change in the morphological structure of the superconducting nanocomposites.

  14. Phase transition and superconductivity of SrFe2As2 under high pressure

    Energy Technology Data Exchange (ETDEWEB)

    Uhoya, Walter [University of Alabama, Birmingham; Montgomery, Jeffrey M [University of Alabama, Birmingham; Tsoi, Georgiy [University of Alabama, Birmingham; Vohra, Yogesh [University of Alabama, Birmingham; McGuire, Michael A [ORNL; Sefat, A. S. [Oak Ridge National Laboratory (ORNL); Sales, Brian C [ORNL; Weir, S. T. [Lawrence Livermore National Laboratory (LLNL)

    2011-01-01

    High pressure x-ray diffraction and electrical resistance measurements have been carried out on SrFe{sub 2}As{sub 2} to a pressure of 23 GPa and temperature of 10 K using a synchrotron source and designer diamond anvils. At ambient temperature, a phase transition from the tetragonal phase to a collapsed tetragonal (CT) phase is observed at 10 GPa under non-hydrostatic conditions. The experimental relation that T-CT transition pressure for 122 Fe-based superconductors is dependent on ambient pressure volume is affirmed. The superconducting transition temperature is observed at 32 K at 1.3 GPa and decreases rapidly with a further increase of pressure in the region where the T-CT transition occurs. Our results suggest that T{sub C} falls below 10 K in the pressure range of 10-18 GPa where the CT phase is expected to be stable.

  15. Superconducting phase prepared from Ta{sub 3}Si under high pressure

    Energy Technology Data Exchange (ETDEWEB)

    Murao, R; Kusaba, K; Fukuoka, K; Sugiyama, K; Syono, Y [IMR, Tohoku University 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); Kikuchi, M [Kansei Fukushi Research Center, Tohoku Fukushi University1-8-1 Kunimi, Aoba-ku, Sendai, Miyagi 981-8522 (Japan); Atou, T [SMC, Materials and Structures Lab. Tokyo Tech. 4259 Nagatsuta-cho Midori-ku, Yokohama, Kanagawa 226-8503 (Japan); Kikegawa, T, E-mail: r_murao@imr.tohoku.ac.j [IMSS, KEK, Oho 1-1, Tsukuba, Ibaraki 305-0801 (Japan)

    2010-03-01

    High-pressure behaviour of Ta{sub 3}Si intermetallic compound was investigated by shock compression and static compression methods. Superconducting phase with T{sub C} = 9.3 K was found in the sample shocked to 50-61 GPa, however most of the shock recovered sample indicated the starting stable phase with the Ti{sub 3}P-type structure. The new superconducting phase was not obtained from static compression up to 15 GPa and 800 {sup 0}C. Bulk modulus of Ta{sub 3}Si with the Ti{sub 3}P-type structure was determined to be K{sub 0} = 246(4) GPa. The present results suggest that a rapid phase transformation occurred during shock compression, but most of the high-pressure phase was reverted to the stable phase in the decompression process.

  16. Heat transfer through Rutherford superconducting cable with novel pattern of polyimide electrical insulation in pressurized superfluid helium environment

    Science.gov (United States)

    Chorowski, Maciej; Polinski, Jaroslaw; Strychalski, Michal

    2012-06-01

    Future LHC accelerator luminosity upgrade will increase a beam losses heat deposition in the superconducting magnet coils. Main barrier of the heat evacuation from the coils made of Rutherford type cables is a cable electrical insulation. The insulation is made of polyimide tapes wrapped around the cable in a special configuration. Presently used insulation wrapping schemes constitute very good electrical insulation with relatively low heat transport ability. Therefore a new insulation wrapping schemes with enhanced helium permeability and adequate dielectric properties have been developed at CERN. An experimental comparative study of heat transfer perpendicular to the Rutherford type cable, for an old and new insulation wrapping schemes have been accomplished at Wroclaw University of Technology. The tests have been performed in pressurized superfluid helium conditions, and at 60 MPa of the sample applied external pressure simulating the Lorentz forces. This paper presents the measurements methodology and gives experimental results.

  17. Enhanced superconductivity of SmFeAsO co-doped by Scandium and Fluorine to increase chemical inner pressure

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Haijie; Zheng, Ming; Fang, Aihua; Yang, Jianhua [CAS Key Laboratory of Materials for Energy Conversion, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Huang, Fuqiang, E-mail: huangfq@mail.sic.ac.cn [CAS Key Laboratory of Materials for Energy Conversion, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Xie, Xiaoming; Jiang, Mianheng [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China)

    2012-10-15

    Sm{sub 1-x/3}Sc{sub x/3}FeAsO{sub 1-x}F{sub x} (x=0.09-0.27) were synthesized by the mechanical alloying and subsequent low temperature rapid sintering (2 h at 950 Degree-Sign C). The superconducting transition temperature (T{sub c}) increased with the doping level of x. The optimal doping achieved a T{sub c} up to 53.5 K in Sm{sub 0.93}Sc{sub 0.07}FeAsO{sub 0.79}F{sub 0.21}. The higher T{sub c} value was attributed to the increased chemical inner pressure from local lattice distortion induced by smaller-size dopants, which was further confirmed by Sm{sub 1-x}Sc{sub x}FeAsO{sub 0.88}F{sub 0.12} (x=0.04, 0.08, 0.12). Accordingly, larger lattice distortion can enhance the superconductivity below the doping limit. Similar phenomenon was also observed in the La{sub 1-x}Y{sub x}FeAsO{sub 0.8}F{sub 0.2} (x=0.4, 0.5, 0.6). - Graphical abstract: The introduction of Sc{sup 3+} and F{sup -} in SmFeAsO leads to higher chemical inner pressure generated by larger lattice distortion, which is the reason of the improved T{sub c}. Highlights: Black-Right-Pointing-Pointer The superconducting properties of Sm{sub 1-x/3}Sc{sub x/3}FeAsO{sub 1-x}F{sub x} are investigated. Black-Right-Pointing-Pointer The co-doping of Sc{sup 3+} and F{sup -} in SmFeAsO leads to higher chemical inner pressure. Black-Right-Pointing-Pointer Higher chemical inner pressure is beneficial to the superconductivity. Black-Right-Pointing-Pointer The co-doped samples of La{sub 1-x}Y{sub x}FeAsO{sub 0.8}F{sub 0.2} further demonstrate the assumption.

  18. Pressure dependence of structural phase transition and superconducting transition in CsI

    CERN Document Server

    Nirmala-Louis, C

    2003-01-01

    The self-consistent band structure calculation for CsI performed both in CsCl and HCP structures using the TB-LMTO method is reported. The equilibrium lattice constant, bulk modulus and the phase-transition pressure at which the compound undergoes structural phase transition from CsCl to HCP are predicted from the total-energy calculations. The band structure, density of states (DOS), electronic charge distributions, metallization and superconducting transition temperature (T sub c) of CsI are obtained as a function of pressure for both the CsCl and HCP structures. It is found that the charge transfer from s and p states to d state causes metallization and superconductivity in CsI. The highest T sub c estimated is 2.11 K and the corresponding pressure is 1.8 Mbar. This value is in agreement with the recent experimental observation. The experimental trend - ''metallization and superconductivity is rather insensitive to the crystal structure of CsI'' - is also confirmed in our work. (Abstract Copyright [2003], ...

  19. Electromechanical properties of superconducting MgB{sub 2} wire

    Energy Technology Data Exchange (ETDEWEB)

    Salama, K; Zhou, Y X; Hanna, M; Alessandrini, M; Putman, P T; Fang, H [Mechanical Engineering Department and Texas Center for Superconductivity, University of Houston, Houston, TX (United States)

    2005-12-15

    The current-carrying capability of superconducting wires is degraded by stress. Therefore electromechanical properties are one of the key feedback parameters needed for progress in conductor applications. In this work, uniaxial tensile stresses and bending stresses were applied to Fe /MgB{sub 2} wires at room temperature, followed by measurement of critical current using a transport method at 4.2 K. Basic mechanical properties were calculated from the measured stress-strain characteristics. The irreversible tensile strain at which the critical current density of MgB{sub 2} wire starts to degrade was found to be 0.5%. In addition, the degradation of I{sub c} with decreasing bending diameters was found to be very rapid for wires that were deformed after the heat treatment that forms the MgB{sub 2} compound, while not much degradation of I{sub c} was found for wires that were bent before being annealed. SEM observations confirmed that cracks could be healed by post-annealing.

  20. Response of superconductivity and crystal structure of LiFeAs to hydrostatic pressure.

    Science.gov (United States)

    Mito, Masaki; Pitcher, Michael J; Crichton, Wilson; Garbarino, Gaston; Baker, Peter J; Blundell, Stephen J; Adamson, Paul; Parker, Dinah R; Clarke, Simon J

    2009-03-04

    On the application of hydrostatic pressures of up to 1.3 GPa, the superconducting transition temperatures (T(c)) of samples of LiFeAs are lowered approximately monotonically at approximately -2 K GPa(-1). Measurements of the X-ray powder diffraction pattern at hydrostatic pressures of up to 17 GPa applied by a He gas pressure medium in a diamond anvil cell reveal a bulk modulus for LiFeAs of 57.3(6) GPa which is much smaller than that of other layered arsenide and oxyarsenide superconductors. LiFeAs also exhibits much more isotropic compression than other layered iron arsenide superconductors. The higher and more isotropic compressibility is presumably a consequence of the small size of the lithium ion. At ambient pressure the FeAs(4) tetrahedra are the most compressed in the basal plane of those in any of the superconducting iron arsenides. On increasing the pressure the Fe-Fe distance contracts more rapidly than the Fe-As distance so that the FeAs(4) tetrahedra become even more distorted from the ideal tetrahedral shape. The decrease in T(c) with applied pressure is therefore consistent with the observations that in the iron arsenides and related materials investigated thus far, T(c) is maximized for a particular electron count when the FeAs(4) tetrahedra are close to regular.

  1. NQR study of pressure induced superconductivity in CeCu{sub 2}Si{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Fujiwara, K.; Okazaki, Y.; Hata, Y.; Miyoshi, K.; Takeuchi, J. [Department of Materials Science, Shimane University, Matsue 690-8504 (Japan); Kobayashi, T.C. [Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530 (Japan); Geibel, C.; Steglich, F. [Max Planck Institute for Chemical Physics of Solids, Nothnitzer Strase 40, 01187 Dresden (Germany)

    2010-03-15

    We have measured nuclear quadrupole resonance (NQR) for {sup 63}Cu nuclei under high pressure up to 4.8 GPa. A linear increase in NQR frequency {sup 63} {nu}{sub Q} of {sup 63}Cu nuclei was observed below 3 GPa. However, {sup 63} {nu}{sub Q} deviates gradually from the linear relation above 3.5 GPa. The downward deviation is associated with a change of valence and consistent with the results of band calculations with the structural parameters under pressure. Antiferromagnetic (AFM) spin fluctuations are drastically suppressed with increasing pressure, whereas T{sub c} increases from 0.7 K at ambient pressure to 1.64 K at 4.2 GPa. We have found that bulk superconductivity suddenly disappears at 4.8 GPa accompanied with a rapid decrease in the density of states at the Fermi level. These are indenter pressure cells for NQR measurements. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  2. Rheological behavior and cryogenic properties of cyanate ester/epoxy insulation material for fusion superconducting magnet

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Z. X.; Huang, C. J. [Key Laboratory of Cryogenics, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, PR (China); Li, L. F. [Key Laboratory of Cryogenics, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, PR China and State Key Laboratory of Technologies in Space Cryogenic Propellants, Technical Institute of Physics and Chemistry, C (China); Li, J. W. [Key Laboratory of Cryogenics, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, PR China and University of Chinese Academy of Sciences, Beijing 100049, PR (China); Tan, R.; Tu, Y. P. [North China Electric Power University, Beijing 102206, PR (China)

    2014-01-27

    In a Tokamak fusion reactor device like ITER, insulation materials for superconducting magnets are usually fabricated by a vacuum pressure impregnation (VPI) process. Thus these insulation materials must exhibit low viscosity, long working life as well as good radiation resistance. Previous studies have indicated that cyanate ester (CE) blended with epoxy has an excellent resistance against neutron irradiation which is expected to be a candidate insulation material for a fusion magnet. In this work, the rheological behavior of a CE/epoxy (CE/EP) blend containing 40% CE was investigated with non-isothermal and isothermal viscosity experiments. Furthermore, the cryogenic mechanical and electrical properties of the composite were evaluated in terms of interlaminar shear strength and electrical breakdown strength. The results showed that CE/epoxy blend had a very low viscosity and an exceptionally long processing life of about 4 days at 60 °C.

  3. Prediction of superconducting iron-bismuth intermetallic compounds at high pressure

    CERN Document Server

    Amsler, Maximilian; Wolverton, Chris

    2016-01-01

    The synthesis of materials in high-pressure experiments has recently attracted increasing attention, especially since the discovery of record breaking superconducting temperatures in the sulfur-hydrogen and other hydrogen-rich systems. Commonly, the initial precursor in a high pressure experiment contains constituent elements that are known to form compounds at ambient conditions, however the discovery of high-pressure phases in systems immiscible under ambient conditions poses an additional materials design challenge. We performed an extensive multi component $ab\\,initio$ structural search in the immiscible Fe--Bi system at high pressure and report on the surprising discovery of two stable compounds at pressures above $\\approx36$ GPa, FeBi$_2$ and FeBi$_3$. According to our predictions, FeBi$_2$ is a metal at the border of magnetism with a conventional electron-phonon mediated superconducting transition temperature of $T_{\\rm c}=1.3$ K at 40 GPa. In analogy to other iron-based materials, FeBi$_2$ is possibly...

  4. Low temperature amorphization and superconductivity in FeSe single crystals at high pressures

    Energy Technology Data Exchange (ETDEWEB)

    Stemshorn, Andrew K.; Tsoi, Georgiy; Vohra, Yogesh K.; Sinogeiken, Stanislav; Wu, Phillip M.; Huang, Yilin; Rao, Sistla M.; Wu, Maw-Kuen; Yeh, Kuo W.; Weir, Samuel T. (IP-Taiwan); (UAB); (Duke); (LLNL)

    2010-08-04

    In this study, we report low temperature x-ray diffraction studies combined with electrical resistance measurements on single crystals of iron-based layered superconductor FeSe to a temperature of 10 K and a pressure of 44 GPa. The low temperature high pressure x-ray diffraction studies were performed using a synchrotron source and superconductivity at high pressure was studied using designer diamond anvils. At ambient temperature, the FeSe sample shows a phase transformation from a PbO-type tetragonal phase to a NiAs-type hexagonal phase at 10 {+-} 2 GPa. On cooling, a structural distortion from a PbO-type tetragonal phase to an orthorhombic Cmma phase is observed below 100 K. At a low temperature of 10 K, compression of the orthorhombic Cmma phase results in a gradual transformation to an amorphous phase above 15 GPa. The transformation to the amorphous phase is completed by 40 GPa at 10 K. A loss of superconductivity is observed in the amorphous phase and a dramatic change in the temperature behavior of electrical resistance indicates formation of a semiconducting state at high pressures and low temperatures. The formation of the amorphous phase is attributed to a kinetic hindrance to the growth of a hexagonal NiAs phase under high pressures and low temperatures.

  5. Decomposition Products of Phosphine Under Pressure: PH2 Stable and Superconducting?

    Science.gov (United States)

    Shamp, Andrew; Terpstra, Tyson; Bi, Tiange; Falls, Zackary; Avery, Patrick; Zurek, Eva

    2016-02-17

    Evolutionary algorithms (EAs) coupled with density functional theory (DFT) calculations have been used to predict the most stable hydrides of phosphorus (PHn, n = 1-6) at 100, 150, and 200 GPa. At these pressures phosphine is unstable with respect to decomposition into the elemental phases, as well as PH2 and H2. Three metallic PH2 phases were found to be dynamically stable and superconducting between 100 and 200 GPa. One of these contains five formula units in the primitive cell and has C2/m symmetry (5FU-C2/m). It comprises 1D periodic PH3-PH-PH2-PH-PH3 oligomers. Two structurally related phases consisting of phosphorus atoms that are octahedrally coordinated by four phosphorus atoms in the equatorial positions and two hydrogen atoms in the axial positions (I4/mmm and 2FU-C2/m) were the most stable phases between ∼160-200 GPa. Their superconducting critical temperatures (Tc) were computed as 70 and 76 K, respectively, via the Allen-Dynes modified McMillan formula and using a value of 0.1 for the Coulomb pseudopotential, μ*. Our results suggest that the superconductivity recently observed by Drozdov, Eremets, and Troyan when phosphine was subject to pressures of 207 GPa in a diamond anvil cell may result from these, and other, decomposition products of phosphine.

  6. Superconducting properties in tantalum decorated three-dimensional graphene and carbon structures

    Energy Technology Data Exchange (ETDEWEB)

    Cobaleda, Cayetano S. F., E-mail: ccobaleda@usal.es, E-mail: wpan@sandia.gov [Sandia National Laboratories, P.O. Box 5800, MS 1086, Albuquerque, New Mexico 87185 (United States); Laboratorio de Bajas Temperaturas, Universidad de Salamanca, E-37008 Salamanca (Spain); Xiao, Xiaoyin; Burckel, D. Bruce; Polsky, Ronen; Pan, W., E-mail: ccobaleda@usal.es, E-mail: wpan@sandia.gov [Sandia National Laboratories, P.O. Box 5800, MS 1086, Albuquerque, New Mexico 87185 (United States); Huang, Duanni [Sandia National Laboratories, P.O. Box 5800, MS 1086, Albuquerque, New Mexico 87185 (United States); Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106 (United States); Diez, Enrique [Laboratorio de Bajas Temperaturas, Universidad de Salamanca, E-37008 Salamanca (Spain)

    2014-08-04

    We present here the results on superconducting properties in tantalum thin films (100 nm thick) deposited on three-dimensional graphene (3DG) and carbon structures. A superconducting transition is observed in both composite thin films with a superconducting transition temperature of 1.2 K and 1.0 K, respectively. We have further measured the magnetoresistance at various temperatures and differential resistance dV/dI at different magnetic fields in these two composite thin films. In both samples, a much large critical magnetic field (∼2 T) is observed and this critical magnetic field shows linear temperature dependence. Finally, an anomalously large cooling effect was observed in the differential resistance measurements in our 3DG-tantalum device when the sample turns superconducting. Our results may have important implications in flexible superconducting electronic device applications.

  7. Search for high-Tc conventional superconductivity at megabar pressures in the lithium-sulfur system

    Science.gov (United States)

    Kokail, Christian; Heil, Christoph; Boeri, Lilia

    2016-08-01

    Motivated by the recent report of superconductivity above 200 K in ultra-dense hydrogen sulfide, we search for high-TC conventional superconductivity in the phase diagram of the binary Li-S system, using ab initio methods for crystal structure prediction and linear response calculations for the electron-phonon coupling. We find that at pressures higher than 20 GPa, several new compositions, besides the known Li2S , are stabilized; many exhibit electride-like interstitial charge localization observed in other alkali-metal compounds. Of all predicted phases, only an fcc phase of Li3S , metastable before 640 GPa, exhibits a sizable TC, in contrast to what is observed in sulfur and phosphorus hydrides, where several stoichiometries lead to high TC. We attribute this difference to 2 s -2 p hybridization and avoided core overlap, and predict similar behavior for other alkali-metal compounds.

  8. Pressure-induced superconductivity in a ferromagnet, UGe sub 2 : resistivity measurements in a magnetic field

    CERN Document Server

    Kobayashi, T C; Tateiwa, N; Amaya, K; Haga, Y; Settai, R; Onuki, Y

    2002-01-01

    Electrical resistivity measurements in a magnetic field are carried out on UGe sub 2 which exhibits pressure-induced superconductivity. The superconductivity is observed from 1.06 to 1.44 GPa. In the temperature and field dependences of the resistivity at P > P sub C where the ferromagnetic ordering disappears, it is observed that the application of an external field along the a-axis increases the coefficient A of the Fermi-liquid behaviour (propor to AT sup 2) abruptly - corresponding to the metamagnetic transition. The characteristic enhancement of H sub C sub 2 is reconfirmed for H || a-axis. The upper critical field of H sub C sub 2 is anisotropic: H sub C sub 2 (T) exhibits positive curvature for H || b-axis and H || c-axis.

  9. High pressure effects on the superconductivity in rare-earth-doped CaFe2As2

    Science.gov (United States)

    Uhoya, Walter; Cargill, Daniel; Gofryk, Krzysztof; Tsoi, Georgiy M.; Vohra, Yogesh K.; Sefat, Athena S.; Weir, S. T.

    2014-01-01

    High pressure superconductivity in a rare-earth-doped Ca0.86Pr0.14Fe2As2 single-crystalline sample has been studied up to 12 GPa and temperatures down to 11 K using the designer diamond anvil cell under a quasi-hydrostatic pressure medium. The electrical resistance measurements were complemented by high pressure and low-temperature X-ray diffraction studies at a synchrotron source. The electrical resistance measurements show an intriguing observation of superconductivity under pressure, with Tc as high as ∼51 K at 1.9 GPa, presenting the highest Tc reported in the intermetallic class of 122 iron-based superconductors. The resistive transition observed suggests a possible existence of two superconducting phases at low pressures of 0.5 GPa: one phase starting at Tc1 ∼ 48 K and the other starts at Tc2 ∼ 16 K. The two superconducting transitions show distinct variations with increasing pressure. High pressure and low-temperature structural studies indicate that the superconducting phase is a collapsed tetragonal ThCr2Si2-type (122) crystal structure.

  10. Superconductivity and physical properties of CaPd2Ge2 single crystals.

    Science.gov (United States)

    Anand, V K; Kim, H; Tanatar, M A; Prozorov, R; Johnston, D C

    2014-10-08

    We present the superconducting and normal state properties of CaPd(2)Ge(2) single crystals investigated by magnetic susceptibility χ, isothermal magnetization M, heat capacity Cp, in-plane electrical resistivity ρ and London penetration depth λ versus temperature T and magnetic field H measurements. Bulk superconductivity is inferred from the ρ(T) and Cp(T) data. The ρ(T) data exhibit metallic behavior and a superconducting transition with T(c onset) = 1.98 K and zero resistivity at T(c 0) = 1.67 K. The χ(T) reveals the onset of superconductivity at 2.0 K. For T > 2.0 K, the χ(T) and M(H) are weakly anisotropic paramagnetic with χ(ab) > χ(c). The Cp(T) data confirm the bulk superconductivity below T(c) = 1.69(3) K. The superconducting state electronic heat capacity is analyzed within the framework of a single-band α-model of BCS superconductivity and various normal and superconducting state parameters are estimated. Within the α-model, the Cp(T) data and the ab plane λ(T) data consistently indicate a moderately anisotropic s-wave gap with Δ(0)/k(B)T(c) ≈ 1.6, somewhat smaller than the BCS value of 1.764. The relationship of the heat capacity jump at Tc and the penetration depth measurement to the anisotropy in the s-wave gap is discussed.

  11. Anomalous pressure dependence of the superconducting transition temperature of beta-pyrochlore AOs2O6 oxides.

    Science.gov (United States)

    Muramatsu, T; Takeshita, N; Terakura, C; Takagi, H; Tokura, Y; Yonezawa, S; Muraoka, Y; Hiroi, Z

    2005-10-14

    High-pressure effects on the superconducting transitions of beta-pyrochlore oxide superconductors AOs(2)O(6) (A = Cs,Rb,K) are studied by measuring resistivity under high pressures up to 10 GPa. The superconducting transition temperature T(c) first increases with increasing pressure in every compound and then exhibits a broad maximum at 7.6 K (6 GPa), 8.2 K (2 GPa), and 10 K (0.6 GPa) for A = Cs, Rb, and K, respectively. Finally, the superconductivity is suppressed completely at a critical pressure near 7 GPa and 6 GPa for A = Rb and K and probably above 10 GPa for A = Cs. Characteristic changes in the coefficient A of the T(2) term in resistivity and residual resistivity are observed, both of which are synchronized with the corresponding change in T(c).

  12. Non-BCS superconducting state in yttrium hydride at a record low value of the external pressure

    Science.gov (United States)

    Jarosik, Marcin W.; Szczȩśniak, Radosław; Wrona, Izabela A.; Kostrzewa, Małgorzata

    2017-01-01

    The ab initio calculations suggest that YH3 compound is a superconductor with the maximum value of the critical temperature (TC) for the record low external pressure equal to 17.7 GPa. Due to the high value of the electron-phonon coupling constant, the thermodynamic properties of the superconducting state in YH3 have been determined in the framework of the Eliashberg formalism. It has been shown that TC changes in the range from 45.91K to 27.29 K, for the value of the Coulomb pseudopotential μ⋆ ∈ . The parameters of the superconducting phase differ significantly from the values predicted by the BCS theory due to the significant strong-coupling and retardation effects: kBTC /ωln ∈ , where ωln denotes the logarithmic phonon frequency. In particular, the dimensionless ratios: RΔ = 2 Δ (0) /kBTC , RC = Δ C (TC) /CN (TC) and RH =TCCN (TC) /HC2(0) take the following values: RΔ ∈ , RC ∈ and RH ∈ . The symbol Δ represents the order parameter, Δ C is the specific heat jump, CN is the specific heat of the normal state, and HC is the thermodynamic critical field.

  13. High-pressure crystal structures and superconductivity of Stannane (SnH4).

    Science.gov (United States)

    Gao, Guoying; Oganov, Artem R; Li, Peifang; Li, Zhenwei; Wang, Hui; Cui, Tian; Ma, Yanming; Bergara, Aitor; Lyakhov, Andriy O; Iitaka, Toshiaki; Zou, Guangtian

    2010-01-26

    There is great interest in the exploration of hydrogen-rich compounds upon strong compression where they can become superconductors. Stannane (SnH(4)) has been proposed to be a potential high-temperature superconductor under pressure, but its high-pressure crystal structures, fundamental for the understanding of superconductivity, remain unsolved. Using an ab initio evolutionary algorithm for crystal structure prediction, we propose the existence of two unique high-pressure metallic phases having space groups Ama2 and P6(3)/mmc, which both contain hexagonal layers of Sn atoms and semimolecular (perhydride) H(2) units. Enthalpy calculations reveal that the Ama2 and P6(3)/mmc structures are stable at 96-180 GPa and above 180 GPa, respectively, while below 96 GPa SnH(4) is unstable with respect to elemental decomposition. The application of the Allen-Dynes modified McMillan equation reveals high superconducting temperatures of 15-22 K for the Ama2 phase at 120 GPa and 52-62 K for the P6(3)/mmc phase at 200 GPa.

  14. High-pressure and high-temperature synthesis of MgB2 and its superconductivity

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The single-phase sample of MgB2 was prepared successfully at the temperature of 900℃ and under the pressure of 3 GPa. The structure of the sample was investigated using powder X-ray diffraction and Rietveld analysis.The results show that the structure of the sample belongs to the hexagonal structure with space group of P6/mmm,a=3.0861(5) A, c=3.5222(8) A. The magnetic and resistance measurements indicate that the superconducting transition temperature Tc is 39 K.

  15. Investigation of Properties of Motion of Superconductive Electrons in Superconductors by Nonlinear Quantum Mechanical Theory

    Institute of Scientific and Technical Information of China (English)

    Xiao-Feng Pang

    2008-01-01

    The properties and rules of motion of superconductive electrons in steady and time-dependent non-equilibrium states of superconductors are studied by using the Ginzberg-Landau (GL) equations and nonlinear quantum theory. In the absence of external fields, the superconductive electrons move in the solitons with certain energy and velocity in a uniform system, The superconductive electron is still a soliton under action of an electromagnetic field, but its amplitude, phase and shape are changed. Thus we conclude that super- conductivity is a result of motion of soliton of superconductive electrons. Since soliton has the feature of motion for retaining its energy and form, thus a permanent current occurs in superconductor. From these solutions of GL equations under action of an electromagnetic field, we gain the structure of vortex lines-magnetic flux lines observed experimentally in type-II superconductors. In the time-dependent non- equilibrium states of superconductor, the motions of superconductive electrons exhibit still the soliton features, but the shape and amplitude have changed. In an invariant electric-field, it moves in a constant acceleration. In the medium with dissipation, the superconductive electron behaves still like a soliton, although its form, amplitude, and velocity are altered. Thus we have to convince that the superconductive electron is essentially a soliton in both non-equilibrium and equilibrium superconductors.

  16. Superconductivity and Properties of FeTeOx Films

    Energy Technology Data Exchange (ETDEWEB)

    D Telesca; j Budnick; B Sinkovic; R Ramprasad; B Wells

    2011-12-31

    Films of the parent compound FeTe can be made superconducting via the addition of interstitial oxygen. The process is reversible. We have characterized the new superconductors with a variety of experiments. X-ray diffraction shows that the superconductor has the same overall structure but a small lattice constant change compared to pure FeTe. X-ray absorption shows that superconducting FeTeO{sub x} has a nominal valence of 3+. DFT calculations show the most likely position for interstitial oxygen and confirm that such oxygen incorporation does not produce a large change in structure.

  17. Randomly distributed spin induced suppression of superconducting properties in Gd-123

    Science.gov (United States)

    Biswas, B.; Haldar, S.; Mukherjee, I.; Kumar Ghosh, Ajay

    2017-02-01

    Suppression of superconducting property in presence of inhomogeneous spin distribution in GdBa2Cu3-xCoxO6.9 has been studied. A superconducting sample without Co exhibits superconducting transition at 56.1 K. The current-voltage (I-V) characteristics exhibit nonlinear to linear transformation above a certain temperature. Two other samples (i) with Co and (ii) without Cu are found to be nonsuperconducting with very high resistive in nature at lower temperature. Localization length decreases with the increase in Co substitution. Suppression of the superconducting transition has been attributed to the change in the magnetic fluctuations induced by the randomness in spin substitution. An exponent has been extracted to understand the current-voltage behaviour. Kosterlitz-Thouless (KT) transition may be affected strongly by the shifting of magnetic fluctuations.

  18. Pressure-induced unconventional superconductivity near a quantum critical point in CaFe{sub 2}As{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Kawasaki, S; Tabuchi, T; Zheng Guoqing [Department of Physics, Okayama University, Okayama 700-8530 (Japan); Wang, X F; Chen, X H [Hefei National Laboratory for Physical Sciences at Microscale and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China)

    2010-05-15

    {sup 75}As-zero-field nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) measurements are performed on CaFe{sub 2}As{sub 2} under pressure. At P = 4.7 and 10.8 kbar, the temperature dependencies of nuclear-spin-lattice relaxation rate (1/T{sub 1}) measured in the tetragonal phase show no coherence peak just below T{sub c}(P) and decrease with decreasing temperature. The superconductivity is gapless at P = 4.7 kbar but evolves to that with multiple gaps at P = 10.8 kbar. We find that the superconductivity appears near a quantum critical point under pressures in the range 4.7 kbar {<=} P {<=} 10.8 kbar. Both electron correlation and superconductivity disappear in the collapsed tetragonal phase. A systematic study under pressure indicates that electron correlations play a vital role in forming Cooper pairs in this compound.

  19. Structural properties of superconducting Bi-2223/Ag tapes

    Energy Technology Data Exchange (ETDEWEB)

    Gottschalck Andersen, L.

    2001-05-01

    The structural properties of silver clad high-T{sub c} superconducting ceramic tapes of (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub x} (Bi-2223) have been investigated by means of synchrotron X-ray diffraction (including the 3DXRD microscope setup), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDS). By synchrotron X-ray diffraction in situ studies of the phase development during the transformation of (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 1}Cu{sub 2}O{sub x} (Bi-2212) into Bi-2223, the stoichiometry changes and the texture have been performed during annealing in 8% O{sub 2} and in air. Furthermore, an annealing with two high temperature cycles has been performed to study the equilibrium phenomena. During heating (Ca,Sr){sub 2}PbO{sub 4} decomposes at temperatures between 700 deg. C and 840 deg.C. Simultaneously, the Bi-2212 lattice contracts, indicating an incorporation of Pb. Moreover, the grain mis-alignment decreases significantly. In air we have observed that Bi-2212 partly dissociates into (Ca,Sr){sub 2}CuO{sub 3} and a liquid at temperatures above 812 deg. C. At the annealing temperature Bi-2212 and (Ca,Sr){sub 2}CuO{sub 3} react with the liquid to form Bi-2223. The transformation mechanism is discussed. During cooling below {approx}750 deg.C (Ca,Sr){sub 2}CuO{sub 3} and the liquid mainly transform into Bi-2201. Below {approx}780 deg. C Bi-2223 decomposes to 3221. In addition, a two-step cooling experiment and a decomposition study have been performed in 8% O{sub 2}. By TEM the grain and colony size in the c-axis direction, the angles of c-axis tilt grain boundaries and the intergrowth content are investigated. A fully processed tape has on average 50% thicker grains than a tape after the 1st annealing. The angles of c-axis tilt grain boundaries are on average 14 deg. and 26 deg. for the fully processed tape and the tape after the 1st annealing, respectively. The intergrowth content (15%) and

  20. Superconducting MgB2 flowers: growth mechanism and their superconducting properties

    Science.gov (United States)

    Seong, Won Kyung; Ranot, Mahipal; Lee, Ji Yeong; Yang, Cheol-Woong; Lee, Jae Hak; Oh, Young Hoon; Ahn, Jae-Pyoung; Kang, Won Nam

    2016-04-01

    We report for the first time the growth and the systematic study of the growth mechanism for flower-like MgB2 structures fabricated on the substrates for solid-state electronics by the hybrid physical-chemical vapor deposition (HPCVD) technique. The MgB2 flower has a width of 30 μm and a height of 10 μm. The superconductivity of MgB2 flowers was confirmed by a magnetization measurement, and the transition temperature is 39 K, which is comparable with high-quality bulk samples. The excellent current-carrying capability was demonstrated by MgB2 flowers. To understand the nucleation and growth mechanism of MgB2 flowers a very systematic study was performed by a high-resolution transmission electron microscope (HRTEM) and atom probe (AP) microscopy. The HRTEM revealed that the seed grain of a MgB2 flower has a [101¯0] direction, and the flower is composed of micro-columnar MgB2 grains having pyramidal tips and which are grown along the (0001) plane. A clear understanding of the growth mechanism for MgB2 flowers could lead to the growth of other low-dimensional MgB2 structures for superconducting electronic devices.

  1. Superconductivity in dense Mg1–MB2 (M = Zr, Nb, Mo; = 0.05) materials sintered under pressure

    Indian Academy of Sciences (India)

    S Kalavathi; C Divakar

    2005-06-01

    Dense compacts of superconducting MgB2 material have been produced by sintering under 3 GPa pressure and 900°C using a cubic anvil apparatus. The starting material was produced by the powder in tube (PIT) method at low pressure and in argon atmosphere. The effect of substitution of Mg sites with nonmagnetic 4-transition metals (Zr, Nb, Mo) on the superconducting transition temperature (c) has been studied by resistivity and susceptibility measurements. The results indicate that there is a small gradual reduction in the transition temperature as we move from Zr to Mo.

  2. Superconducting properties of combustion synthesized MgB{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Takano, Yoshihiko; Oguro, Nobutaka; Kaieda, Yoshinari; Togano, Kazumasa

    2004-10-01

    We have successfully prepared the MgB{sub 2} superconducting bulk and powdered materials by the method of combustion synthesis. The starting materials used in this study were powders of Mg and B. X-ray powder diffraction pattern was well assigned to the P6/mmm MgB{sub 2} phase. The temperature dependence of magnetization shows sharp superconducting transition around 38 K. The critical current density can be estimated from the hysteresis of the magnetization curvature using the Bean's model. The powdered sample shows a high critical current density of 2 x 10{sup 6} A/cm{sup 2} at 5 K under the magnetic field of 1 T.

  3. Nonequilibrium interpretation of DC properties of NbN superconducting hot electron bolometers

    CERN Document Server

    Shcherbatenko, M; Lobanov, Yu; Maslennikov, S N; Kaurova, N; Finkel, M; Voronov, B; Goltsman, G; Klapwijk, T M

    2016-01-01

    We present a physically consistent interpretation of the dc electrical properties of niobiumnitride (NbN)-based superconducting hot-electron bolometer (HEB-) mixers, using concepts of nonequilibrium superconductivity. Through this we clarify what physical information can be extracted from the resistive transition and the dc current-voltage characteristics, measured at suitably chosen temperatures, and relevant for device characterization and optimization. We point out that the intrinsic spatial variation of the electronic properties of disordered superconductors, such as NbN, leads to a variation from device to device.

  4. Nonequilibrium Properties of Variable-Thickness Superconducting Micro-bridges.

    Science.gov (United States)

    1978-01-01

    shor t is always lef t near the leads to prevent acci- dental burnout. This short is only removed once the leads are soldered (with an unplugged and...interest here, by overlaying a superconduct- ing film with a normal metal,14 by optical, phonon or quasi— 15 16particle injection, by ion implantation or...which might not be justified in the regimes of interest. Experimentall y, further work is requir ed in order to understand the low voltage I—V

  5. Pressure Dependence of the Ginzburg-Landau Parameter in Superconducting YB6

    Science.gov (United States)

    Gabáni, S.; Orendáč, Mat.; Kušnír, J.; Gažo, E.; Pristáš, G.; Mori, T.; Flachbart, K.

    2016-12-01

    We present measurements of the superconducting critical temperature T_c , the upper critical field H_{c2} and the third critical field H_{c3} as a function of pressure in BCS type-II superconductor YB6 (T_c = 7.5 K, H_{c2}(0) = 270 mT and H_{c3}(0) = 450 mT at ambient pressure) up to 3 GPa. Magnetic susceptibility measurements down to 2 K have shown a negative pressure effect on T_c as well as on H_{c2} with slopes dT_c/dp = -0.531 K/GPa (d ln T_c/{dp} = -7.1 %/GPa) and dH_{c2}(0)/dp = -37 mT/GPa (d ln H_{c2}/{dp} = -14 %/GPa) , respectively. Parallel magnetoresistance measurements evidenced nearly the same slopes of d ln T_c/{dp} = -5.9 %/GPa (d ln H_{c3}/{dp} = -11 %/GPa) in the equal pressure range. From these results, the estimated pressure effect on the coherence length dξ (0)/{dp} = 2.05 nm/GPa together with the supposed zero pressure effect on the magnetic penetration depth (dλ (0)/{dp} ≈ 0 ) implies that the Ginzburg-Landau parameter κ (0) = {λ }(0)/{ξ }(0) decreases with pressure as dκ (0)/d{p} = -0.31/GPa. According to this decrease, a transition from type-II to type-I superconductor should be observed in YB6 at a critical pressure p_c ≈ 10 GPa.

  6. Anisotropic superconducting property studies of single crystal PbTaSe2

    Science.gov (United States)

    Sankar, Raman; Narsinga Rao, G.; Panneer Muthuselvam, I.; Chang, Tay-Rong; Jeng, H. T.; Senthil Murugan, G.; Lee, Wei-Li; Chou, F. C.

    2017-03-01

    The anisotropic superconducting properties of PbTaSe2 single crystal is reported. Superconductivity with T c  =  3.83  ±  0.02 K has been characterized fully with electrical resistivity ρ(T), magnetic susceptibility χ(T), and specific heat C p (T) measurements using single crystal samples. The superconductivity is type-II with lower critical field H c1 and upper critical field H c2 of 65 and 450 Oe (H⊥  to the ab-plane), 140 and 1500 Oe (H|| to the ab-plane), respectively. These results indicate that the superconductivity of PbTaSe2 is anisotropic. The superconducting anisotropy, electron-phonon coupling λ ep, superconducting energy gap Δ0, and the specific heat jump ΔC/γT c at T c confirms that PbTaSe2 can be categorized as a bulk superconductor.

  7. Anisotropic superconducting property studies of single crystal PbTaSe2.

    Science.gov (United States)

    Sankar, Raman; Rao, G Narsinga; Muthuselvam, I Panneer; Chang, Tay-Rong; Jeng, H T; Murugan, G Senthil; Lee, Wei-Li; Chou, F C

    2017-03-08

    The anisotropic superconducting properties of PbTaSe2 single crystal is reported. Superconductivity with T c  =  3.83  ±  0.02 K has been characterized fully with electrical resistivity ρ(T), magnetic susceptibility χ(T), and specific heat C p (T) measurements using single crystal samples. The superconductivity is type-II with lower critical field H c1 and upper critical field H c2 of 65 and 450 Oe (H⊥  to the ab-plane), 140 and 1500 Oe (H|| to the ab-plane), respectively. These results indicate that the superconductivity of PbTaSe2 is anisotropic. The superconducting anisotropy, electron-phonon coupling λ ep, superconducting energy gap Δ0, and the specific heat jump ΔC/γT c at T c confirms that PbTaSe2 can be categorized as a bulk superconductor.

  8. Single crystals of superconducting SmFeAsO Hx : Structure and properties

    Science.gov (United States)

    Pisoni, A.; Katrych, S.; Arakcheeva, A.; Verebélyi, T.; Bokor, M.; Huang, P.; Gaál, R.; Matus, P.; Karpinski, J.; Forró, L.

    2016-07-01

    We report the synthesis, structure, and superconducting properties of single crystals of SmFeAsO Hx . The crystals were grown at high pressure and high temperature using a cubic anvil technique. 1H-NMR studies confirm the presence of H atoms in the samples. Single crystal x-ray diffraction analyses demonstrate a remarkable disorder in the S m2O2 layers induced by hydrogen incorporation and reveal that the H positions are compatible with a H2O -like geometry inside the crystals. We have measured the magnetotransport properties of SmFeAsO Hx single crystals with x =0.07 , 0.11, and 0.16 in magnetic field up to 16 T, oriented along the two main crystallographic directions. The results show an increase of the critical temperature with hydrogen content. The zero-temperature upper critical fields and the magnetic anisotropy are calculated as a function of the hydrogen content. SmFeAsO Hx crystals present significantly higher upper critical fields and magnetic anisotropies compared to SmFeAs O1 -xFx compounds.

  9. Thermal properties of a large-bore cryocooled 10 T superconducting magnet for a hybrid magnet

    Energy Technology Data Exchange (ETDEWEB)

    Ishizuka, M., E-mail: Mas_Ishizuka@shi.co.j [Graduate School of Engineering, Tohoku University, 6-6 Aramaki Aza Aoba, Aoba-ku, Sendai 980-8579 (Japan); Research and Development Center, Sumitomo Heavy Industries, Ltd., 19 Natsushima-chou, Yokosuka, Kanagawa 237-8555 (Japan); Hamajima, T. [Graduate School of Engineering, Tohoku University, 6-6 Aramaki Aza Aoba, Aoba-ku, Sendai 980-8579 (Japan); Itou, T. [Ehime Works, Sumitomo Heavy Industries, Ltd., 5-2 Soubiraki-cho, Niihama, Ehime 792-8588 (Japan); Sakuraba, J. [Research and Development Center, Sumitomo Heavy Industries, Ltd., 19 Natsushima-chou, Yokosuka, Kanagawa 237-8555 (Japan); Nishijima, G.; Awaji, S.; Watanabe, K. [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan)

    2010-11-01

    A cryocooled 10 T superconducting magnet with a 360 mm room temperature bore has been developed for a hybrid magnet. The superconducting magnet cooled by four Gifford-McMahon cryocoolers has been designed to generate a magnetic field of 10 T. Since superconducting wires composed of coils were subjected to large hoop stress over 150 MPa and Nb{sub 3}Sn superconducting wires particularly showed a low mechanical strength due to those brittle property, Nb{sub 3}Sn wires strengthened by NbTi-filaments were developed for the cryocooled superconducting magnet. We have already reported that the hybrid magnet could generate the resultant magnetic field of 27.5 T by adding 8.5 T from the superconducting magnet and 19 T from a water-cooled Bitter resistive magnet, after the water-cooled resistive magnet was inserted into the 360 mm room temperature bore of the cryocooled superconducting magnet. When the hybrid magnet generated the field of 27.5 T, it achieved the high magnetic-force field (B x {partial_derivative}Bz/{partial_derivative}z) of 4500 T{sup 2}/m, which was useful for magneto-science in high fields such as materials levitation research. In this paper, we particularly focus on the cause that the cryocooled superconducting magnet was limited to generate the designed magnetic field of 10 T in the hybrid magnet operation. As a result, it was found that there existed mainly two causes as the limitation of the magnetic field generation. One was a decrease of thermal conductive passes due to exfoliation from the coil bobbin of the cooling flange. The other was large AC loss due to both a thick Nb{sub 3}Sn layer and its large diameter formed on Nb-barrier component in Nb{sub 3}Sn wires.

  10. Effects of oxide precursors on superconducting properties of polycrystalline SmFeAsO1-xFx

    Science.gov (United States)

    Yuan, F. F.; Ding, Y.; Sun, Y.; Zhuang, J. C.; Zhou, W.; Li, G. Z.; Sumption, M.; Li, X. W.; Shi, Z. X.

    2013-12-01

    A series of polycrystalline SmFeAsO1-xFx samples were synthesized by one-step and two-step method at ambient pressure using different oxide precursors, namely As2O3, Fe2O3 and nano-Fe2O3 powder, as the source of element O. Results of X-ray diffraction and magnetic measurements manifest that starting oxides affected the phase formation and superconducting properties of SmFeAsO1-xFx. As2O3 as oxide precursor contributes to the fast formation of superconducting phase for a short period of sintering time. And samples prepared using As2O3 show higher superconducting transition temperature Tc and more stable fluorine doping level. Compared with Fe2O3, nano-Fe2O3 promotes fluorine doping into the O site. While using Fe2O3 leads to higher level of Fe and SmOF impurities. The critical current density Jcm were derived from magnetic hysteresis loops. Sample prepared using As2O3 shows higher Jcm in low temperature and high magnetic fields.

  11. Miniature ceramic-anvil high-pressure cell for magnetic measurements in a commercial superconducting quantum interference device magnetometer.

    Science.gov (United States)

    Tateiwa, Naoyuki; Haga, Yoshinori; Fisk, Zachary; Ōnuki, Yoshichika

    2011-05-01

    A miniature opposed-anvil high-pressure cell has been developed for magnetic measurement in a commercial superconducting quantum interference device magnetometer. Non-magnetic anvils made of composite ceramic material were used to generate high-pressure with a Cu-Be gasket. We have examined anvils with different culet sizes (1.8, 1.6, 1.4, 1.2, 1.0, 0.8, and 0.6 mm). The pressure generated at low temperature was determined by the pressure dependence of the superconducting transition of lead (Pb). The maximum pressure P(max) depends on the culet size of the anvil: the values of P(max) are 2.4 and 7.6 GPa for 1.8 and 0.6 mm culet anvils, respectively. We revealed that the composite ceramic anvil has potential to generate high-pressure above 5 GPa. The background magnetization of the Cu-Be gasket is generally two orders of magnitude smaller than the Ni-Cr-Al gasket for the indenter cell. The present cell can be used not only with ferromagnetic and superconducting materials with large magnetization but also with antiferromagnetic compounds with smaller magnetization. The production cost of the present pressure cell is about one tenth of that of a diamond anvil cell. The anvil alignment mechanism is not necessary in the present pressure cell because of the strong fracture toughness (6.5 MPa m(1∕2)) of the composite ceramic anvil. The simplified pressure cell is easy-to-use for researchers who are not familiar with high-pressure technology. Representative results on the magnetization of superconducting MgB(2) and antiferromagnet CePd(5)Al(2) are reported.

  12. Characterization of superconducting properties of BSCCO powder prepared by attrition milling

    Energy Technology Data Exchange (ETDEWEB)

    Patel, R H [Brockhouse Institute for Materials Research, McMaster University, 1280 Main Street West, Hamilton, ON, L8S 4M1 (Canada); Nabialek, A [Brockhouse Institute for Materials Research, McMaster University, 1280 Main Street West, Hamilton, ON, L8S 4M1 (Canada); Niewczas, M [Brockhouse Institute for Materials Research, McMaster University, 1280 Main Street West, Hamilton, ON, L8S 4M1 (Canada)

    2005-03-01

    The nonconventional technique of attrition milling has been used to produce superconducting BSCCO powder from the starting powders of oxides and carbonates of Bi, Sr, Ca and Cu. This process shows a drastic reduction in processing time by 80% from the conventional solid-state reaction. The completion of the reaction was determined by x-ray diffraction of the milled powder. The superconducting property characterization was done for the critical transition temperature and the critical current density of the processed powder by magnetic methods. The attrition milled powder shows a T{sub c} of about 87 K after two high temperature treatments for 60 h and J{sub c} of the order of 10{sup 6} A cm{sup -2} at 4 K. The superconducting properties of the processed powder are discussed in the framework of the Bean model.

  13. Search for pressure-induced superconductivity in CeFeAsO and CeFePO iron pnictides

    Energy Technology Data Exchange (ETDEWEB)

    Zocco, D. A. [University of California, San Diego; Baumbach, R. E. [University of California, San Diego; Hamlin, J. J. [University of California, San Diego; Janoschek, M. [University of California, San Diego; Lum, I. K. [University of California, San Diego; McGuire, Michael A [ORNL; Safa-Sefat, Athena [ORNL; Sales, Brian C [ORNL; Jin, Rongying [ORNL; Mandrus, David [ORNL; Jeffries, J. R. [Lawrence Livermore National Laboratory (LLNL); Weir, S. T. [Lawrence Livermore National Laboratory (LLNL); Vohra, Y. K. [University of Alabama, Birmingham; Maple, M. B. [University of California, San Diego

    2011-01-01

    The CeFeAsO and CeFePO iron pnictide compounds were studied via electrical transport measurements under high pressure. In CeFeAsO polycrystals, the magnetic phases involving the Fe and Ce ions coexist for hydrostatically applied pressures up to 15 GPa, and with no signs of pressure-induced superconductivity up to 50 GPa for the less hydrostatic pressure techniques. For the CeFePO single crystals, pressure further stabilizes the Kondo screening of the Ce 4f-electron magnetic moments.

  14. Pressure-induced superconductivity in the giant Rashba system BiTeI

    OpenAIRE

    VanGennep, D.; Linscheid, A.; Jackson, D E; Weir, S. T.; Vohra, Y. K.; Berger, H.; Stewart, G. R.; Hennig, R. G.; Hirschfeld, P. J.; Hamlin, J. J.

    2016-01-01

    At ambient pressure, BiTeI is the first material found to exhibit a giant Rashba splitting of the bulk electronic bands. At low pressures, BiTeI undergoes a transition from trivial insulator to topological insulator. At still higher pressures, two structural transitions are known to occur. We have carried out a series of electrical resistivity and AC magnetic susceptibility measurements on BiTeI at pressure up to ~40 GPa in an effort to characterize the properties of the high-pressure phases....

  15. Stoichiometry and thickness dependence of superconducting properties of niobium nitride thin films

    Energy Technology Data Exchange (ETDEWEB)

    Beebe, Melissa R., E-mail: mrbeebe@email.wm.edu; Beringer, Douglas B.; Burton, Matthew C.; Yang, Kaida; Lukaszew, R. Alejandra [Department of Physics, The College of William & Mary, Small Hall, 300 Ukrop Way, Williamsburg, Virginia 23185 (United States)

    2016-03-15

    The current technology used in linear particle accelerators is based on superconducting radio frequency (SRF) cavities fabricated from bulk niobium (Nb), which have smaller surface resistance and therefore dissipate less energy than traditional nonsuperconducting copper cavities. Using bulk Nb for the cavities has several advantages, which are discussed elsewhere; however, such SRF cavities have a material-dependent accelerating gradient limit. In order to overcome this fundamental limit, a multilayered coating has been proposed using layers of insulating and superconducting material applied to the interior surface of the cavity. The key to this multilayered model is to use superconducting thin films to exploit the potential field enhancement when these films are thinner than their London penetration depth. Such field enhancement has been demonstrated in MgB{sub 2} thin films; here, the authors consider films of another type-II superconductor, niobium nitride (NbN). The authors present their work correlating stoichiometry and superconducting properties in NbN thin films and discuss the thickness dependence of their superconducting properties, which is important for their potential use in the proposed multilayer structure. While there are some previous studies on the relationship between stoichiometry and critical temperature T{sub C}, the authors are the first to report on the correlation between stoichiometry and the lower critical field H{sub C1}.

  16. Structural, electronic, elastic and superconducting properties of noble metal nitrides MN{sub 2} (M = Ru, Rh, Pd)

    Energy Technology Data Exchange (ETDEWEB)

    Puvaneswari, S. [Department of Physics, E.M.G. Yadava Women' s College, Madurai, Tamilnadu 625 014 (India); Rajeswarapalanichamy, R., E-mail: rrpcaspd2003@gmail.com [Department of Physics, N.M.S.S. Vellaichamy Nadar College, Madurai, Tamilnadu 625019 (India); Sudha Priyanga, G. [Department of Physics, N.M.S.S. Vellaichamy Nadar College, Madurai, Tamilnadu 625019 (India)

    2015-02-01

    The structural stability, electronic structure, elastic and superconducting properties of noble metal nitrides MN{sub 2} (M = Ru, Rh, Pd) are investigated in tetragonal (P4/mbm), fluorite (Fm3m), orthorhombic (Pnnm), pyrite (Pa-3) and hexagonal (P6/mmm) phases using first principles calculations. The calculated lattice parameters are in good agreement with other theoretical results. Among the considered structures, RhN{sub 2} and PdN{sub 2} are found to be most stable in tetragonal structure, whereas RuN{sub 2} is stable in fluorite structure. A sequence of structural phase transition is predicted under high pressure in these metal nitrides. The electronic structure reveals that these nitrides are metallic. These metal nitrides are found to be covalent, ionic and metallic in the stable phase. The observations show that these metal nitrides are mechanically stable at ambient condition. The superconducting transition temperatures for RuN{sub 2}, RhN{sub 2} and PdN{sub 2} are found to be 1.65 K, 5.01 K and 8.7 K respectively. - Highlights: • Electronic, structural and elastic properties of RuN{sub 2}, RhN{sub 2} and PdN{sub 2} are studied. • A pressure induced structural phase transition is predicted. • Electronic structure reveals that these materials exhibit metallic behavior. • High bulk modulus indicates that RuN{sub 2}, RhN{sub 2} and PdN{sub 2} are superhard materials. • Superconducting temperature values are reported.

  17. Pressure effect of superconducting oxypnictide LaFeAO{sub 1-x}F{sub x} and related materials

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, H; Okada, H [College of Humanities and Siences, Nihon University and JST TRIP, Tokyo 156-8550 (Japan); Kamihara, Y [JST, TRIP, Tokyo Institute of Technology, Yokohama 226-8503 (Japan); Matsuishi, S; Hirano, M; Hosono, H [Frontier Research Center, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503 (Japan); Matsubayashi, K; Uwatoko, Y, E-mail: hiroki@chs.nihon-u.ac.j [Institute for Solid State Physics, University of Tokyo, Kashiwanoha, Kashiwa, Chiba 277-8581 (Japan)

    2010-03-01

    Pressure dependence on superconducting transition temperature (T{sub c}) has been investigated for iron-based superconductor LaFeAsO{sub 1-x}F{sub x}, SmFeAsO{sub 1-x}F{sub x} and Ca(Fe{sub 1-x}Co{sub x})AsF. The T{sub c} increases largely for LaFeAsO{sub 1-x}F{sub x} with a small increase of pressure, and decreases with further compression. In SmFeAsO{sub 1-x}F{sub x} the T{sub c} decreases with increasing pressure. The increase of T{sub c} in LaFeAsO{sub 1-x}F{sub x} seems to be related to the suppression of magnetic ordering phase. Pressure-induced superconductivity was observed for these materials. The common features on 1111 type superconductors are discussed.

  18. International round robin test for mechanical properties of REBCO superconductive tapes at room temperature

    NARCIS (Netherlands)

    Osamura, K.; Shin, H.S.; Weiss, K.; Nyilas, A.; Nijhuis, A.; Yamamoto, K.; Machiya, S.; Nishijima, G.

    2014-01-01

    An international round robin test was promoted to establish a test method for room temperature mechanical properties of commercial REBCO superconductive tapes. Seven laboratories practiced a tensile test under the direction of guideline REBCO13 for four different kinds of REBCO tape. From the stress

  19. International round robin test for mechanical properties of REBCO superconductive tapes at room temperature

    NARCIS (Netherlands)

    Osamura, K.; Shin, H.S.; Weiss, K.; Nyilas, A.; Nijhuis, Arend; Yamamoto, K.; Machiya, S.; Nishijima, G.

    2014-01-01

    An international round robin test was promoted to establish a test method for room temperature mechanical properties of commercial REBCO superconductive tapes. Seven laboratories practiced a tensile test under the direction of guideline REBCO13 for four different kinds of REBCO tape. From the stress

  20. Enhanced superconductivity in the high pressure phase of SnAs studied from first principles

    Science.gov (United States)

    Sreenivasa Reddy, P. V.; Kanchana, V.; Millichamp, T. E.; Vaitheeswaran, G.; Dugdale, S. B.

    2017-01-01

    First principles calculations are performed using density functional theory and density functional perturbation theory for SnAs. Total energy calculations show the first order phase transition from an NaCl structure to a CsCl one at around 37 GPa, which is also confirmed from enthalpy calculations and agrees well with experimental work. Calculations of the phonon structure and hence the electron-phonon coupling, λep, and superconducting transition temperature, Tc, across the phase diagram are performed. These calculations give an ambient pressure Tc, in the NaCl structure, of 3.08 K, in good agreement with experiment whilst at the transition pressure, in the CsCl structure, a drastically increased value of Tc = 12.2 K is found. Calculations also show a dramatic increase in the electronic density of states at this pressure. The lowest energy acoustic phonon branch in each structure also demonstrates some softening effects. Electronic structure calculations of the Fermi surface in both phases are presented for the first time as well as further calculations of the generalised susceptibility with the inclusion of matrix elements. These calculations indicate that the softening is not derived from Fermi surface nesting and it is concluded to be due to a wavevector-dependent enhancement of the electron-phonon coupling.

  1. Anomalous compressibility effects and superconductivity of EuFe2As2 under high pressures

    Energy Technology Data Exchange (ETDEWEB)

    Uhoya, Walter [University of Alabama, Birmingham; Tsoi, Georgiy [University of Alabama, Birmingham; Vohra, Y. K. [University of Alabama, Birmingham; McGuire, Michael A [ORNL; Sefat, A. S. [Oak Ridge National Laboratory (ORNL); Sales, Brian C [ORNL; Mandrus, David [ORNL; Weir, S. T. [Lawrence Livermore National Laboratory (LLNL)

    2010-01-01

    The crystal structure and electrical resistance of structurally layered EuFe{sub 2}As{sub 2} have been studied up to 70 GPa and down to a temperature of 10 K, using a synchrotron x-ray source and designer diamond anvils. The room temperature compression of the tetragonal phase of EuFe{sub 2}As{sub 2} (I4/mmm) results in an increase in the a-axis length and a rapid decrease in the c-axis length with increasing pressure. This anomalous compression reaches a maximum at 8 GPa and the tetragonal lattice behaves normally above 10 GPa, with a nearly constant c/a axial ratio. The rapid rise in the superconducting transition temperature (T{sub c}) to 41 K with increasing pressure is correlated with this anomalous compression, and a decrease in T{sub c} is observed above 10 GPa. We present P-V data or the equation of state for EuFe{sub 2}As{sub 2} both in the ambient tetragonal phase and in the high pressure collapsed tetragonal phase up to 70 GPa.

  2. Can electron multipacting explain the pressure rise in a cold bore superconducting undulator?

    Directory of Open Access Journals (Sweden)

    S. Casalbuoni

    2010-07-01

    Full Text Available Preliminary studies performed with the cold bore superconducting undulator installed in the ANKA (Angstrom source Karlsruhe storage ring suggest that the beam heat load is mainly due to the electron wall bombardment. Electron bombardment can both heat the cold vacuum chamber and induce an increase in the pressure because of gas desorption. In this contribution we compare the measurements of the pressure in a cold bore performed in the electron storage ring ANKA with the predictions obtained using the equations of gas dynamic balance in a cold vacuum chamber exposed to synchrotron radiation and electron bombardment. The balance results from two competing effects: the photon and electron stimulated desorption of the gas contained in the surface layer of the chamber wall and of the gas cryosorbed, and the cryopumping by the cold surface. We show that photodesorption alone cannot explain the experimental results and that electron multipacting is needed to reproduce the observed pressure rise. Electron bombardment can at the same time explain the observed beam heat load.

  3. Magnetic response and critical current properties of mesoscopic-size YBCO superconducting samples

    Energy Technology Data Exchange (ETDEWEB)

    Lisboa-Filho, P N [UNESP - Universidade Estadual Paulista, Grupo de Materiais Avancados, Departamento de Fisica, Bauru (Brazil); Deimling, C V; Ortiz, W A, E-mail: plisboa@fc.unesp.b [Grupo de Supercondutividade e Magnetismo, Departamento de Fisica, Universidade Federal de Sao Carlos, Sao Carlos (Brazil)

    2010-01-15

    In this contribution superconducting specimens of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} were synthesized by a modified polymeric precursor method, yielding a ceramic powder with particles of mesoscopic-size. Samples of this powder were then pressed into pellets and sintered under different conditions. The critical current density was analyzed by isothermal AC-susceptibility measurements as a function of the excitation field, as well as with isothermal DC-magnetization runs at different values of the applied field. Relevant features of the magnetic response could be associated to the microstructure of the specimens and, in particular, to the superconducting intra- and intergranular critical current properties.

  4. Laser patterning: A new approach to measure local magneto-transport properties in multifilamentary superconducting tapes

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez Valdes, C.F. [Superconductivity Laboratory, Magnetism Laboratory, IMRE-Physics Faculty, University of Havana, 10400 Havana (Cuba); Perez-Penichet, C. [Superconductivity Laboratory, Magnetism Laboratory, IMRE-Physics Faculty, University of Havana, 10400 Havana (Cuba); Noda, C. [Superconductivity Laboratory, Magnetism Laboratory, IMRE-Physics Faculty, University of Havana, 10400 Havana (Cuba); Arronte, M. [Laser Technology Laboratory, CICATA-IPN, ALTAMIRA, Altamira 89600, TAMPS (Mexico); Batista-Leyva, A.J. [Department of General Physics and Mathematics, InSTEC, 10400 Havana (Cuba); Haugen, O. [Department of Physics, University of Oslo, Blindern, N-0316 Oslo (Norway); Johansen, T.H. [Department of Physics, University of Oslo, Blindern, N-0316 Oslo (Norway); Han, Z. [Applied Superconductivity Research Center, Department of Physics, Tsinghua University, Beijing 100084 (China); Altshuler, E. [Superconductivity Laboratory, Magnetism Laboratory, IMRE-Physics Faculty, University of Havana, 10400 Havana (Cuba)]. E-mail: ea@infomed.sld.cu

    2007-09-15

    The determination of inter- and intra-filament characteristics in superconducting composites such as BSCCO-Ag tapes is of great importance for material evaluation towards applications. Most attempts to separate the two contributions have relied on indirect methods based on magnetic measurements such as SQUID or magneto-optic imaging techniques. Here we show that laser patterning of superconducting BSCCO-Ag tapes constitutes a simple approach to measure local transport properties in a direct way, even able to separate inter- and intra-filament contributions to the overall transport behavior of the sample.

  5. Homogeneous lattice disorder and superconducting properties of YBa2Cu3O6.9 films.

    Science.gov (United States)

    Pavuna, Davor; Gauzzi, Andrea

    We discuss the striking changes of the superconducting properties of YBa2Cu3O6.9 films to the homogeneous lattice disorder, induced by varying growth temperatures: Tc decreases with increasing disorder, while the width of the resistive transition and the normal state resistivity increase. We estimate the length scale of such dis- order from the broadening DJ of the lt; 005 > X-ray diffraction rocking curves. The suppression of superconductivity and normal conductivity scales as DJ and appears for in-plane lattice coherence lengths rc ≫ 1/DJ smaller than about 10 nm.

  6. SRF test facility for the superconducting LINAC ``RAON'' — RRR property and e-beam welding

    Science.gov (United States)

    Jung, Yoochul; Hyun, Myungook; Joo, Jongdae; Joung, Mijoung

    2015-02-01

    Equipment, such as a vacuum furnace, high pressure rinse (HPR), eddy current test (ECT) and buffered chemical polishing (BCP), are installed in the superconducting radio frequency (SRF) test facility. Three different sizes of cryostats (diameters of 600 mm for a quarter wave resonator (QWR), 900 mm for a half wave resonator (HWR), and 1200 mm for single spoke resonator 1&2 (SSR 1&2)) for vertical RF tests are installed for testing cavities. We confirmed that as-received niobium sheets (ASTM B393, RRR300) good electrical properties because they showed average residual resistance ratio (RRR) values higher than 300. However, serious RRR degradation occurred after joining two pieces of Nb by e-beam welding because the average RRR values of the samples were ˜179, which was only ˜60% of as-received RRR value. From various e-beam welding experiments in which the welding current and a speed at a fixed welding voltage were changed, we confirmed that good welding results were obtained at a 53 mA welding current and a 20-mm/s welding speed at a fixed welding voltage of 150 kV.

  7. Robust superconductivity and transport properties in (Li1- x Fe x )OHFeSe single crystals

    Science.gov (United States)

    Lin, Hai; Xing, Jie; Zhu, XiYu; Yang, Huan; Wen, Hai-Hu

    2016-05-01

    The recently discovered (Li1- x Fe x )OHFeSe superconductor with T c about 40 K provides a good platform for investigating the magnetization and electrical transport properties of FeSe-based superconductors. By using a hydrothermal ion-exchange method, we have successfully grown crystals of (Li1- x Fe x )OHFeSe. X-ray diffraction on the sample shows the single crystalline PbO-type structure with the c-axis preferential orientation. Magnetic susceptibility and resistive measurements show an onset superconducting transition at around T c =38.3 K. Using the magnetization hysteresis loops and Bean critical state model, a large critical current J s is observed in low temperature region. The critical current density is suppressed exponentially with increasing magnetic field. Temperature dependencies of resistivity under various currents and fields are measured, revealing a robust superconducting current density and bulk superconductivity.

  8. Vortex Properties of Nanosized Superconducting Strips with One Central Weak Link Under an Applied Current Drive

    Science.gov (United States)

    Peng, Lin; Cai, Chuanbing

    2016-06-01

    The static and dynamic properties of vortices in a nanosized superconducting strip with one central weak link (weakly superconducting region or normal metal) are investigated in the presence of external magnetic and electric fields. The time-dependent Ginzburg-Landau equations are used to describe the electronic transport and have been solved numerically by a finite element analysis. Anisotropy is included through the spatially dependent anisotropy coefficient ζ in different layers of the sample. Our results show that the energy barrier for vortices to enter a weak link is smaller than that for vortices to enter the superconducting layers. The magnetization shows periodic oscillations. With the introduction of the weak link, the period of oscillations decreases.

  9. The focusing properties of both normal and superconducting low energy CW proton Linacs

    CERN Document Server

    Zhihui, Li

    2016-01-01

    The continue wave (CW) high current proton linac has wide applications as the front end of the high power proton machines. The low energy part is the most difficult one and there is no widely accepted solution yet. Both normal conducting and superconducting acceleration structures are thought to be the possible solutions. Although the characteristics of normal conducting structures and superconducting ones are quite different, such as acceleration voltage, maximum electric field and so on, we found the focusing properties of the lattice composed by these two acceleration structures are quite similar for different reasons. The advantages and disadvantages of lattices composed of both the normal conducting and superconducting structures are analysed from the beam dynamics point of view, and their constraints on beam main parameters are discussed.

  10. Upper critical field of KFe2As2 under pressure: A test for the change in the superconducting gap structure

    Energy Technology Data Exchange (ETDEWEB)

    Taufour, Valentin [Ames Laboratory; Foroozani, Neda [Washington University; Tanatar, Makariy A. [Ames Laboratory; Lim, Jinhyuk [Washington University; Kaluarachchi, Udhara [Iowa State University; Kim, Stella K. [Ames Laboratory; Liu, Yong [Ames Laboratory; Lograsso, Thomas A. [Ames Laboratory; Kogan, Vladimir G. [Ames Laboratory; Prozorov, Ruslan [Ames Laboratory; Bud' ko, Sergey L. [Ames Laboratory; Schilling, James S. [Washington University; Canfield, Paul C. [Ames Laboratory

    2014-06-01

    We report measurements of electrical resistivity under pressure to 5.8 GPa, magnetization to 6.7 GPa, and ac susceptibility to 7.1 GPa in KFe2As2. The previously reported change of slope in the pressure dependence of the superconducting transition temperature Tc(p) at a pressure p*~1.8 GPa is confirmed, and Tc(p) is found to be nearly constant above p* up to 7.1 GPa. The T-p phase diagram is very sensitive to the pressure conditions as a consequence of the anisotropic uniaxial pressure dependence of Tc. Across p*, a change in the behavior of the upper critical field is revealed through a scaling analysis of the slope of Hc2 with the effective mass as determined from the A coefficient of the T2 term of the temperature-dependent resistivity. We show that this scaling provides a quantitative test for the changes of the superconducting gap structure and suggests the development of a kz modulation of the superconducting gap above p* as a most likely explanation.

  11. Simultaneous suppression of superconductivity and structural phase transition under pressure in Ca10(Ir4As8)(Fe2 -xIrxAs2)5

    Science.gov (United States)

    Kitagawa, Shunsaku; Araki, Shingo; Kobayashi, Tatsuo C.; Ishii, Hiroyuki; Fujimura, Kazunori; Mitsuoka, Daisuke; Kudo, Kazutaka; Nohara, Minoru

    2014-12-01

    We measured the pressure dependence of in-plane resistivity ρa b in the recently discovered iron-based superconductor Ca10(Ir4As8) (Fe2-xIrxAs2) 5 , which shows a unique structural phase transition in the absence of magnetic ordering, with a superconducting transition temperature Tc=16 K and a structural phase transition temperature Ts≃100 K at ambient pressure. Tc and Ts are suppressed on applying pressure and disappear at approximately 0.5 GPa, suggesting a relationship between superconductivity and structure. Ca10(Ir4As8) (Fe2-xIrxAs2) 5 is a rather rare example in which the superconductivity appears only in a low-temperature ordered phase. The fact that the change in the crystal structure is directly linked with superconductivity suggests that the crystal structure as well as magnetism are important factors governing superconductivity in iron pnictides.

  12. Effect of layer thickness on the superconducting properties in ultrathin Pb films

    Science.gov (United States)

    Durajski, A. P.

    2015-09-01

    Recently, superconductivity was found in one atomic layer of Pb film, promising a new field of research where superconductors can be studied on the atomic level. In the presented paper, we report a theoretical study of the superconductivity in ultrathin Pb films consisting of five to ten monolayers. Using the strong coupling Eliashberg formalism we reproduced the experimental values of critical temperature (TC) and we estimated the superconducting energy gap (Δ (0)), thermodynamic critical field (HC) and the specific heat jump at critical temperature (Δ C≤ft({T}{{C}}\\right)\\equiv {C}{{S}}≤ft({T}{{C}}\\right)-{C}{{N}}≤ft({T}{{C}}\\right)) for a wide range of film thicknesses. In these systems, we found an oscillatory behaviour of the above thermodynamic properties modulated by quantum size effects. Moreover, the large values of 2Δ (0){/k}{{B}}{T}{{C}} and Δ C≤ft({T}{{C}}\\right)/{C}{{N}}≤ft({T}{{C}}\\right), and the small values of {T}{{C}}{C}{{N}}≤ft({T}{{C}}\\right)/{H}{{C}}2(0) prove that the thermodynamic properties of Pb films cannot be correctly described using the Bardeen-Cooper-Schrieffer (BCS) theory of superconductivity due to the strong coupling and retardation effects.

  13. Point contact tunneling spectroscopy apparatus for large scale mapping of surface superconducting properties

    Energy Technology Data Exchange (ETDEWEB)

    Groll, Nickolas; Pellin, Michael J. [Materials Science Division, Argonne National Laboratory, Lemont, Illinois 60439 (United States); Zasadzinksi, John F. [Illinois Institute of Technology, Chicago, Illinois 60616 (United States); Proslier, Thomas, E-mail: prolier@anl.gov [Materials Science Division, Argonne National Laboratory, Lemont, Illinois 60439 (United States); High Energy Physics Division, Argonne National Laboratory, Lemont, Illinois 60439 (United States)

    2015-09-15

    We describe the design and testing of a point contact tunneling spectroscopy device that can measure material surface superconducting properties (i.e., the superconducting gap Δ and the critical temperature T{sub C}) and density of states over large surface areas with size up to mm{sup 2}. The tip lateral (X,Y) motion, mounted on a (X,Y,Z) piezo-stage, was calibrated on a patterned substrate consisting of Nb lines sputtered on a gold film using both normal (Al) and superconducting (PbSn) tips at 1.5 K. The tip vertical (Z) motion control enables some adjustment of the tip-sample junction resistance that can be measured over 7 orders of magnitudes from a quasi-ohmic regime (few hundred Ω) to the tunnel regime (from tens of kΩ up to few GΩ). The low noise electronic and LabVIEW program interface are also presented. The point contact regime and the large-scale motion capabilities are of particular interest for mapping and testing the superconducting properties of macroscopic scale superconductor-based devices.

  14. Physical properties of the superconducting spin-valve Fe/Cu/Fe/In heterostructure

    Science.gov (United States)

    Leksin, P. V.; Garif'yanov, N. N.; Garifullin, I. A.; Schumann, J.; Kataev, V.; Schmidt, O. G.; Büchner, B.

    2012-01-01

    We report on structural, magnetic, and superconducting properties of the spin-valve multilayer system CoOx/Fe1/Cu/Fe2/In. For most of the thicknesses of the second iron layer dFe2 up to 2 nm, we have observed a full spin-valve effect for the superconducting current, i.e., a complete transition from the normal to the superconducting state by changing the mutual orientation of the magnetizations of the Fe1 and Fe2 layers. For dFe2<1 nm, the superconducting transition temperature TcP for the parallel orientation of magnetizations of the Fe1 and Fe2 layers is smaller than that for the antiparallel orientation TcAP, which corresponds to the direct spin-valve effect. For dFe2⩾1 nm, we have found the inverse spin-valve effect with ΔTc=TcAP-TcP<0. Further, in samples with a fixed thickness of the In layer, we have observed an oscillating dependence of its superconducting transition temperature Tc on dFe2. The analysis of the Tc(dFe2) dependence using the theory of the superconducting-ferromagnetic proximity effect has enabled determination of all microscopic parameters of the studied system. With these parameters, a satisfactory description of the sign-changing oscillating behavior of the spin-valve effect ΔTc(dFe2) has been obtained using a recent theory by Fominov [Ya. V. Fominov , Pis'ma Zh. Eksp. Teor. Fiz. 91, 329 (2010) [JETP Lett.JTPLA20021-364010.1134/S002136401006010X 91, 308 (2010)

  15. Pressure-induced superconductivity in the iron-based ladder material BaFe2S3.

    Science.gov (United States)

    Takahashi, Hiroki; Sugimoto, Akira; Nambu, Yusuke; Yamauchi, Touru; Hirata, Yasuyuki; Kawakami, Takateru; Avdeev, Maxim; Matsubayashi, Kazuyuki; Du, Fei; Kawashima, Chizuru; Soeda, Hideto; Nakano, Satoshi; Uwatoko, Yoshiya; Ueda, Yutaka; Sato, Taku J; Ohgushi, Kenya

    2015-10-01

    All the iron-based superconductors identified so far share a square lattice composed of Fe atoms as a common feature, despite having different crystal structures. In copper-based materials, the superconducting phase emerges not only in square-lattice structures but also in ladder structures. Yet iron-based superconductors without a square-lattice motif have not been found, despite being actively sought out. Here, we report the discovery of pressure-induced superconductivity in the iron-based spin-ladder material BaFe2S3, a Mott insulator with striped-type magnetic ordering below ∼120 K. On the application of pressure this compound exhibits a metal-insulator transition at about 11 GPa, followed by the appearance of superconductivity below Tc = 14 K, right after the onset of the metallic phase. Our findings indicate that iron-based ladder compounds represent promising material platforms, in particular for studying the fundamentals of iron-based superconductivity.

  16. Stability of superconducting La Sr cuprate in hydrothermal NaF solutions at elevated temperatures and pressures

    Energy Technology Data Exchange (ETDEWEB)

    Korytkova, E.N.; Nesterchuk, N.I.; Pivovarova, L.N. [and others

    1992-04-20

    The successful application of hydrothermal treatment for raising the stability of the superconducting (SC) oxide of the composition La{sub 1.8}Sr{sub 0.2}CuO{sub 4-{delta}} (LSCO), demonstrated earlier, stimulates further development of studies in this field. Selection of chemical reagents the action of which on the crystal structure of the oxide strengthens it is most significant. The literature contains information on the stabilizing action of fluoride ions on the structure of HTSC compounds inserted in oxygen positions of crystal lattices during annealing of Sc cuprates in gaseous NF{sub 3}, NH{sub 4}F, NH{sub 5}F{sub 2}. The possibility of replacing oxygen ions by fluoride ions exists owing to the same electron configuration of their external layers and almost the same ionic radii. Since their electronegativities and degrees of oxidation are different, it may be inferred that even partial replacement of oxygen by fluorine would have a significant influence on the state of the structure of the SC oxide and possibly on the SC properties. In the light of this, hydrothermal treatment of SC oxide with solutions of fluorides, and in particular with NaF solution at an elevated temperature and especially at a high pressure, i.e., under conditions favorable for insertion of fluoride ions into the crystal structure of the cuprate, seemed to be appropriate. 7 refs., 5 figs.

  17. Anisotropy of superconducting critical fields of {alpha}-(BEDT-TTF){sub 2}KHg(SCN){sub 4} under pressure

    Energy Technology Data Exchange (ETDEWEB)

    Jakob, S.; Neumaier, K.; Biberacher, W.; Kartsovnik, M. [Walther-Meissner-Inst., Garching (Germany)

    2007-07-01

    Our previous studies of the ''magnetic field - pressure - temperature'' phase diagram of the layered organic conductor {alpha}-(BEDT-TTF){sub 2}KHg(SCN){sub 4} have revealed an interesting interplay between a charge density wave (CDW) and a superconducting (SC) state. At a critical pressure of 2.5 kbar the CDW state is completely suppressed and a sharp transition into a SC state is observed below 100 mK. For pressures below 2.5 kbar there is a coexistence of the superconducting and CDW state, but this is likely a spatially inhomogenous state. The neighbouring of a CDW and SC state is an interesting situation and rises questions about the nature of the superconductivity. We have therefore investigated the anisotropy of the critical fields at a pressure slightly above the critical one. The experiments were performed in a dilution refrigerator down to 25 mK. Two-axes rotation of the magnetic field allowed the exact determination of the anisotropy parallel and perpendicular to the layers, but also the inplane anisotropy. (orig.)

  18. Gossamer high-temperature bulk superconductivity in FeSe

    Science.gov (United States)

    Sinchenko, A. A.; Grigoriev, P. D.; Orlov, A. P.; Frolov, A. V.; Shakin, A.; Chareev, D. A.; Volkova, O. S.; Vasiliev, A. N.

    2017-04-01

    Using the anisotropic electron transport and susceptibility measurements we demonstrate the appearance of inhomogeneous gossamer superconductivity in FeSe single crystals at ambient pressure and at temperature five times higher than its zero resistance Tc. We also find and quantitatively describe a general property: If inhomogeneous superconductivity in a anisotropic conductor first appears in the form of isolated superconducting islands, it reduces electric resistivity anisotropically with maximal effect along the least conducting axis. This gives a simple tool to study inhomogeneous superconductivity in various anisotropic compounds, which helps to investigate the onset of high-temperature superconductivity.

  19. Collapsed tetragonal phase and superconductivity of BaFe[subscript 2]As[subscript 2] under high pressure

    Energy Technology Data Exchange (ETDEWEB)

    Uhoya, Walter; Stemshorn, Andrew; Tsoi, Georgiy; Vohra, Yogesh K.; Sefat, Athena S.; Sales, Brian C.; Hope, Kevin M.; Weir, Samuel T. (UAB); (ORNL); (LLNL); (Montevallo)

    2010-11-12

    High pressure x-ray diffraction and electrical resistance measurements have been carried out on BaFe{sub 2}As{sub 2} to a pressure of 35 GPa and temperature of 10 K using a synchrotron source and designer diamond anvils. At ambient temperature, a phase transition from the tetragonal phase to a collapsed tetragonal (CT) phase is observed at 17 GPa under nonhydrostatic conditions as compared to 22 GPa under hydrostatic conditions. The superconducting transition temperature increases rapidly with pressure up to 34 K at 1 GPa and decreases gradually with a further increase in pressure. Our results suggest that T{sub C} falls below 10 K in the pressure range of 16-30 GPa, where CT phase is expected to be stable under high-pressure and low-temperature conditions.

  20. Tensile properties and probability of filament fracture in Bi-2223 superconducting tapes

    Energy Technology Data Exchange (ETDEWEB)

    Rabara, Michal [School of Engineering, The University of Tokyo, Tokai-mura, Naka-gun, Ibaraki 319-1106 (Japan). E-mail: rabara at tokai.t.u-tokyo.ac.jp; Sekimura, Naoto [School of Engineering, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 117-0033 (Japan); Kitaguchi, Hidetoshi [National Research Institute for Metals, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Kovac, Pavol [Institute of Electrical Engineering, Slovak Academy of Sciences, Dubravskacesta 9, 842 39 Bratislava (Slovakia); Demachi, Kazuyuki; Miya, Kenzo [School of Engineering, The University of Tokyo, Tokai-mura, Naka-gun, Ibaraki 319-1106 (Japan)

    1999-07-01

    Investigation of the mechanical properties of Bi-2223 superconducting tapes was performed by tensile tests. The results show rapid degradation of the critical current after exceeding 0.4% strain. The shape of the I{sub c}=f({epsilon}) curves and the so-called irreversible strain remain identical for various magnetic fields (0-8 T) and temperatures (4.2, 20, 77 K), demonstrating independence of the mechanical properties from these parameters. The superconducting tapes were treated as a composite consisting of a plastic matrix with brittle ceramic fibres. Under uniform tensile load, the probability of the filament fracture follows a Weibull distribution. Its inverse function, the probability of the number of unbroken filaments, is compared with the relative degradation of the critical current obtained from experiment. (author)

  1. Superconducting Properties of the K$_{{x}}$WO$_{3}$ Tetragonal Tungsten Bronze and the Superconducting Phase Diagram of the Tungsten Bronze Family

    OpenAIRE

    Haldolaarachchige, Neel; Gibson, Quinn; Krizan, Jason; Cava, R. J.

    2014-01-01

    We report the superconducting properties of the K$_{x}$WO$_{3}$ tetragonal tungsten bronze. The highest superconducting transition temperature ($T_{c}=2.1$K) was obtained for K$_{0.38}$WO$_{3}$. $T_{c}$ decreases linearly with increasing K content. Using the measured values for the upper critical field $H_{c2}$, and the specific heat $C$, we estimate the orbital critical field $H_{c2}$(0), coherence length $\\xi$(0), Debye temperature $\\Theta _{D}$ and coupling constant $\\lambda _{ep}$. The ma...

  2. Titania doping effect on superconducting properties of MgB2 bulk samples

    Science.gov (United States)

    Serrano, G.; Bridoux, G.; Serquis, A.

    2009-05-01

    In this work we study the microstructural and superconducting properties of doped and undoped bulk MgB2 samples prepared by solid-state reaction, with 0 and 2.5 %at. nominal TiO2 nanotubes contents, annealed at different temperatures in the 750-900°C range. We discuss the Tc, Jc and Hc2 performance and their correlation with the different synthesis parameters.

  3. Titania doping effect on superconducting properties of MgB{sub 2} bulk samples

    Energy Technology Data Exchange (ETDEWEB)

    Serrano, G; Serquis, A [Institute Balseiro - Centra Atomico Bariloche and CONICET, (8400) S. C. de Bariloche, Rio Negro (Argentina); Bridoux, G, E-mail: serranog@ib.cnea.gov.a [Institute Balseiro - Centra Atomico Bariloche, (8400) S. C. de Bariloche, Rio Negro (Argentina)

    2009-05-01

    In this work we study the microstructural and superconducting properties of doped and undoped bulk MgB{sub 2} samples prepared by solid-state reaction, with 0 and 2.5 %at. nominal TiO{sub 2} nanotubes contents, annealed at different temperatures in the 750-900 deg. C range. We discuss the T{sub c}, J{sub c} and H{sub c2} performance and their correlation with the different synthesis parameters.

  4. Superconducting properties of the KxWO3 tetragonal tungsten bronze and the superconducting phase diagram of the tungsten bronze family

    Science.gov (United States)

    Haldolaarachchige, Neel; Gibson, Quinn; Krizan, Jason; Cava, R. J.

    2014-03-01

    We report on the superconducting properties of the KxWO3 tetragonal tungsten bronze. The highest superconducting transition temperature (Tc=2.1 K) was obtained for K0.38WO3. Tc decreases linearly with increasing K content. Using the measured values for the upper critical field Hc2 and the specific heat C, we estimate the orbital critical field Hc2(0), coherence length ξ(0), Debye temperature ΘD, and coupling constant λe-p. The magnitude of the specific-heat jump at Tc suggests that the KxWO3 tetragonal tungsten bronze is a weakly coupled superconductor. The superconducting phase diagram of the doped tungsten bronze family is presented.

  5. Study on effect of annealing conditions on structural, magnetic and superconducting properties of MgB{sub 2} bulk samples

    Energy Technology Data Exchange (ETDEWEB)

    Phaneendra, Konduru, E-mail: phaneendra-50@yahoo.com; Asokan, K., E-mail: phaneendra-50@yahoo.com; Kanjilal, D. [Inter University Accelerator Centre, Aruna Asaf Ali Marg, Vasanth Kung, New Delhi-110067 (India); Awana, V. P. S. [Quantum Phenomena and Applications, National Physical Laboratory, K S Krishnan Marg, New Delhi-110012 (India); Sastry, S. Sreehari [Dept. of Physics, Acharya Nagarjuna University, Guntur-522510 (India)

    2014-04-24

    Effect of annealing conditions on structural, magnetic and superconducting properties of Magnesium Diboride (MgB{sub 2}) bulk superconductor samples prepared by solid state route method are compared. The samples are made by taking Magnesium and Boron powders in stoichiometric ratio, grounded well and pelletized at pressure of about 10Tonnes. These pellets are annealed in both Argon and vacuum environment separately up to 800°c for two hours. Both the samples show clear superconducting transition at Tc ∼ 38 k. This is further conformed by AC/DC magnetization (M-T), Resistivity [ρ (T, H)] measurements under magnetic field up to 14 Tesla as well. Rietveld refinement of X-ray diffraction of both samples conformed the MgB{sub 2} phase formation with P6/mmm space group symmetry. Scanning Electron Microscopy images of the surface revile more agglomeration of grains in case of Argon annealed samples. This result in more critical current density (J{sub c}) of Argon annealed samples than vacuum annealed one calculated from Bean's critical state model. This high Jc is explained in terms of more inter grain connectivity for Argon annealed sample than vacuum annealed sample.

  6. Study on effect of annealing conditions on structural, magnetic and superconducting properties of MgB2 bulk samples

    Science.gov (United States)

    Phaneendra, Konduru; Asokan, K.; Awana, V. P. S.; Sastry, S. Sreehari; Kanjilal, D.

    2014-04-01

    Effect of annealing conditions on structural, magnetic and superconducting properties of Magnesium Diboride (MgB2) bulk superconductor samples prepared by solid state route method are compared. The samples are made by taking Magnesium and Boron powders in stoichiometric ratio, grounded well and pelletized at pressure of about 10Tonnes. These pellets are annealed in both Argon and vacuum environment separately up to 800°c for two hours. Both the samples show clear superconducting transition at Tc ˜ 38 k. This is further conformed by AC/DC magnetization (M-T), Resistivity [ρ (T, H)] measurements under magnetic field up to 14 Tesla as well. Rietveld refinement of X-ray diffraction of both samples conformed the MgB2 phase formation with P6/mmm space group symmetry. Scanning Electron Microscopy images of the surface revile more agglomeration of grains in case of Argon annealed samples. This result in more critical current density (Jc) of Argon annealed samples than vacuum annealed one calculated from Bean's critical state model. This high Jc is explained in terms of more inter grain connectivity for Argon annealed sample than vacuum annealed sample.

  7. Superconducting and normal-state properties of the noncentrosymmetric superconductor Re6Zr

    Science.gov (United States)

    Mayoh, D. A.; Barker, J. A. T.; Singh, R. P.; Balakrishnan, G.; Paul, D. McK.; Lees, M. R.

    2017-08-01

    We systematically investigate the normal and superconducting properties of noncentrosymmetric Re6Zr using magnetization, heat capacity, and electrical resistivity measurements. Resistivity measurements indicate Re6Zr has poor metallic behavior and is dominated by disorder. Re6Zr undergoes a superconducting transition at Tc=(" close=")10.3 ±0.1 )">6.75 ±0.05 K. Magnetization measurements give a lower critical field, μ0Hc 1=(11.2 ±0.2 )T , which is close to the Pauli limiting field of 12.35 T and which could indicate singlet-triplet mixing. However, low-temperature specific-heat data suggest that Re6Zr is an isotropic, fully gapped s -wave superconductor with enhanced electron-phonon coupling. Unusual flux pinning resulting in a peak effect is observed in the magnetization data, indicating an unconventional vortex state.

  8. Calculated Changes in the Elastic Properties of MgCNi3 at the Superconducting Transition

    Directory of Open Access Journals (Sweden)

    R. Abd-Shukor

    2013-01-01

    Full Text Available We calculated the elastic properties of MgCNi3 at the superconducting transition ( using various thermodynamic and acoustic data. From the calculations, a step discontinuity of 8 ppm in the bulk modulus, 7 ppm in the Young’s modulus, and 3 ppm in the longitudinal sound velocity ( is expected at . The step discontinuities at the transition temperature indicated the importance of lattice changes to the superconducting mechanism of MgCNi3. The Debye temperature was calculated to be 460 K. The electron-phonon coupling constants calculated in the weak and strong coupling limits of the BCS theory and the van Hove scenario showed that MgCNi3 is a moderately strong coupled superconductor.

  9. Modifications of Superconducting Properties of Niobium Caused by Nitrogen Doping Recipes for High Q Cavities

    Energy Technology Data Exchange (ETDEWEB)

    Vostrikov, Alexander [Fermilab; Checchin, Mattia [Fermilab; Grassellino, Anna [Fermilab; Kim, Young-Kee [U. Chicago (main); Romanenko, Alexander [Fermilab

    2015-06-01

    A study is presented on the superconducting properties of niobium used for the fabrication of the SRF cavities after treating by recently discovered nitrogen doping methods. Cylindrical niobium samples have been subjected to the standard surface treatments applied to the cavities (electro-polishing, l 20°C bake) and compared with samples treated by additional nitrogen doping recipes routinely used to reach ultra-high quality factor values (>3· 1010 at 2 K, 16 MV/m). The DC magnetization curves and the complex magnetic AC susceptibility have been measured. Evidence for the lowered field of first flux penetration after nitrogen doping is found suggesting a correlation with the lowered quench fields. Superconducting critical temperatures Tc = 9.25 K are found to be in agreement with previous measurements, and no strong effect on the critical surface field (Bd) from nitrogen doping was found.

  10. Thermomechanical properties of the coil of the superconducting magnets for the Large Hadron Collider

    CERN Document Server

    Couturier, K; Scandale, Walter; Todesco, Ezio; Tommasini, D

    2002-01-01

    The correct definition and measurement of the thermomechanical properties of the superconducting cable used in high-field magnets is crucial to study and model the behavior of the magnet coil from assembly to the operational conditions. In this paper, the authors analyze the superconducting coil of the main dipoles for the Large Hadron Collider. They describe an experimental setup for measuring the elastic modulus at room and at liquid nitrogen temperature and for evaluating the thermal contraction coefficient. The coils exhibit strong nonlinear stress-strain behavior characterized by hysteresis phenomena, which decreases from warm to cold temperature, and a thermal contraction coefficient, which depends on the stress applied to the cable during cooldown. (35 refs).

  11. Higher Order Mode Properties of Superconducting Two-Spoke Cavities

    Energy Technology Data Exchange (ETDEWEB)

    Hopper, C. S.; Delayen, J. R.; Olave, R. G.

    2011-07-01

    Multi-Spoke cavities lack the cylindrical symmetry that many other cavity types have, which leads to a more complex Higher Order Mode (HOM) spectrum. In addition, spoke cavities offer a large velocity acceptance which means we must perform a detailed analysis of the particle velocity dependence for each mode's R/Q. We present here a study of the HOM properties of two-spoke cavities designed for high-velocity applications. Frequencies, R/Q and field profiles of HOMs have been calculated and are reported.

  12. Pressure effect on the superconductivity and the metal-insulator transition in Cu sub 1 sub sub - sub x Zn sub x Ir sub 2 S sub 4

    CERN Document Server

    Cao, G; Kitazawa, H; Isobe, M; Matsumoto, T

    2002-01-01

    The variations of the superconducting transition temperature T sub c and the metal-insulator (MI) transition temperature T sub M sub I were investigated as a function of pressure in the superconducting Cu sub 1 sub sub - sub x Zn sub x Ir sub 2 S sub 4 (0.3 <= x <= 0.5) system. The experiment was performed by measuring the temperature dependence of resistance under the pressures up to 1.5 GPa. It is shown that the external pressure destroys the superconductivity, and gives rise to the MI transitions. The result is discussed in terms of the stabilization of the insulating phase at high pressures and the phase separation associated with the charge segregation. It is proposed that the BCS Cooper pairs compete with the proposed bipolarons under certain pressures.

  13. Recent advances in fullerene superconductivity

    CERN Document Server

    Margadonna, S

    2002-01-01

    Superconducting transition temperatures in bulk chemically intercalated fulleride salts reach 33 K at ambient pressure and in hole-doped C sub 6 sub 0 derivatives in field-effect-transistor (FET) configurations, they reach 117 K. These advances pose important challenges for our understanding of high-temperature superconductivity in these highly correlated organic metals. Here we review the structures and properties of intercalated fullerides, paying particular attention to the correlation between superconductivity and interfullerene separation, orientational order/disorder, valence state, orbital degeneracy, low-symmetry distortions, and metal-C sub 6 sub 0 interactions. The metal-insulator transition at large interfullerene separations is discussed in detail. An overview is also given of the exploding field of gate-induced superconductivity of fullerenes in FET electronic devices.

  14. Superconductivity and superconductive electronics

    Science.gov (United States)

    Beasley, M. R.

    1990-12-01

    The Stanford Center for Research on Superconductivity and Superconductive Electronics is currently focused on developing techniques for producing increasingly improved films and multilayers of the high-temperature superconductors, studying their physical properties and using these films and multilayers in device physics studies. In general the thin film synthesis work leads the way. Once a given film or multilayer structure can be made reasonably routinely, the emphasis shifts to studying the physical properties and device physics of these structures and on to the next level of film quality or multilayer complexity. The most advanced thin films synthesis work in the past year has involved developing techniques to deposit a-axis and c-axis YBCO/PBCO superlattices and related structures. The in-situ feature is desirable because no solid state reactions with accompanying changes in volume, morphology, etc., that degrade the quality of the film involved.

  15. Theoretical predictions of novel superconducting phases of BaGe3 stable at atmospheric and high pressures.

    Science.gov (United States)

    Zurek, Eva; Yao, Yansun

    2015-03-16

    A series of new superconducting binary silicides and germanides have recently been synthesized under high-pressure high-temperature conditions. A representative member of this group, BaGe3, was theoretically investigated using evolutionary structure searches coupled with structural analogies in the pressure range from 1 atm to 250 GPa, where three new phases were discovered. At 1 atm, in addition to the synthesized P63/mmc phase, we predicted two new phases, I4/mmm and Amm2, to be dynamically stable. The Amm2 structure comprises Ge clusters and triangular prisms intercalated with Ba and Ge atoms, a unique structural motif unknown to this group. The I4/mmm structure has been previously synthesized in binary silicides and is calculated to be thermodynamically stable in BaGe3 between 15.6 and 35.4 GPa. Above 35.4 GPa, two new phases of P6̅m2 and R3̅m symmetry become the global minima and remain so up to the highest pressure considered. These two phases have very similar enthalpies, and both feature layers of double Kagome nets of Ge intercalated with Ba-Ge layers. The predicted phases are suggested to be metallic with itinerant electrons and to be potentially superconducting from the considerable electron-phonon coupling strength. Density functional perturbation calculations combined with the Allen-Dynes-modified McMillan formula were used to estimate the superconducting critical temperatures (Tc) for these new phases, which, with slight pressure variations, are comparable to the experimental Tc measured for the P63/mmc phase.

  16. Magnetic measurements at pressures above 10 GPa in a miniature ceramic anvil cell for a superconducting quantum interference device magnetometer.

    Science.gov (United States)

    Tateiwa, Naoyuki; Haga, Yoshinori; Matsuda, Tatsuma D; Fisk, Zachary

    2012-05-01

    A miniature ceramic anvil high pressure cell (mCAC) was earlier designed by us for magnetic measurements at pressures up to 7.6 GPa in a commercial superconducting quantum interference magnetometer [N. Tateiwa et al., Rev. Sci. Instrum. 82, 053906 (2011)]. Here, we describe methods to generate pressures above 10 GPa in the mCAC. The efficiency of the pressure generation is sharply improved when the Cu-Be gasket is sufficiently preindented. The maximum pressure for the 0.6 mm culet anvils is 12.6 GPa when the Cu-Be gasket is preindented from the initial thickness of 300-60 μm. The 0.5 mm culet anvils were also tested with a rhenium gasket. The maximum pressure attainable in the mCAC is about 13 GPa. The present cell was used to study YbCu(2)Si(2) which shows a pressure induced transition from the non-magnetic to magnetic phases at 8 GPa. We confirm a ferromagnetic transition from the dc magnetization measurement at high pressure. The mCAC can detect the ferromagnetic ordered state whose spontaneous magnetic moment is smaller than 1 μ(B) per unit cell. The high sensitivity for magnetic measurements in the mCAC may result from the simplicity of cell structure. The present study shows the availability of the mCAC for precise magnetic measurements at pressures above 10 GPa.

  17. Microstructural and Superconducting Properties of V-Doped MgB2 Bulk and Wires

    Science.gov (United States)

    Castillo, O. E.; Sastry, P. V. P. S. S.; Trociewitz, B.; Trociewitz, U. P.; Schwartz, J.

    2004-06-01

    Studies of the effects of doping MgB2 bulk and Fe-clad wires with V are presented. Samples of composition Mg1-xVxB2 (x = 0.0, 0.05, 0.10, 0.15) have been investigated to understand the role of V doping on the phase formation, microstructure and superconducting properties. Fe-clad wires were fabricated by groove rolling and cold drawing. The superconducting transition temperature remained constant at about 39 K for all the compositions studied. Energy dispersive x-ray (EDX) analysis confirmed the presence of V in the superconducting phase. Enhancement of magnetization hysteresis loop widths indicates an improvement in flux pinning for V-doped samples. Studies on the variation of maximum reaction temperatures suggest that the optimum reaction temperature varies with V content. The optimum reaction temperature also depended on the wire diameter with the larger wires requiring higher reaction temperature. The transport critical current densities measured for groove-rolled wires were in the range of 1.0 - 1.4 × 105 A/cm2.

  18. Atomically flat superconducting nanofilms: multiband properties and mean-field theory

    Science.gov (United States)

    Shanenko, A. A.; Aguiar, J. Albino; Vagov, A.; Croitoru, M. D.; Milošević, M. V.

    2015-05-01

    Recent progress in materials synthesis enabled fabrication of superconducting atomically flat single-crystalline metallic nanofilms with thicknesses down to a few monolayers. Interest in such nano-thin systems is attracted by the dimensional 3D-2D crossover in their coherent properties which occurs with decreasing the film thickness. The first fundamental aspect of this crossover is dictated by the Mermin-Wagner-Hohenberg theorem and concerns frustration of the long-range order due to superconductive fluctuations and the possibility to track its impact with an unprecedented level of control. The second important aspect is related to the Fabri-Pérot modes of the electronic motion strongly bound in the direction perpendicular to the nanofilm. The formation of such modes results in a pronounced multiband structure that changes with the nanofilm thickness and affects both the mean-field behavior and superconductive fluctuations. Though the subject is very rich in physics, it is scarcely investigated to date. The main obstacle is that there are no manageable models to study a complex magnetic response in this case. Full microscopic consideration is rather time consuming, if practicable at all, while the standard Ginzburg-Landau theory is not applicable. In the present work we review the main achievements in the subject to date, and construct and justify an efficient multiband mean-field formalism which allows for numerical and even analytical treatment of nano-thin superconductors in applied magnetic fields.

  19. Anisotropy of normal state and superconducting properties of oxypnictides

    Energy Technology Data Exchange (ETDEWEB)

    Haindl, Silvia; Kidszun, Martin; Kauffmann, Alexander; Kozlova, Nadja; Iida, Kazumasa; Vakaliuk, Oleksii; Panarina, Nadezda; Hess, Christian; Buechner, Bernd [IFW Dresden (Germany); Thersleff, Thomas [IFW Dresden (Germany); The Angstroem Laboratory, Department of Engineering Sciences, Division of Applied Materials Science, Uppsala University (Sweden); Kawaguchi, Takahiko; Ikuta, Hiroshi [Department of Crystalline Materials Science, Nagoya University (Japan); Kampert, Erik; Wosnitza, Joachim [Hochfeld-Magnetlabor Dresden (HLD), Helmholtz-Zentrum Dresden-Rossendorf, Dresden (Germany)

    2013-07-01

    The very large upper critical fields of the oxypnictides complicate the experimental determination of their anisotropy, γ{sub Hc2}, especially at low temperatures. We have applied the anisotropic Ginzburg-Landau scaling on angular-dependent critical-current densities measured for an epitaxially grown La(O{sub 1-x}F{sub x})FeAs thin film. The obtained scaling parameter matches γ{sub H{sub c{sub 2}}} as can be demonstrated by recent magnetotransport measurements in pulsed magnetic fields up to 70 T and down to 2 K. Using the method of critical current scaling H{sub c2}{sup ab} for Nd(O{sub 1-x}F{sub x})FeAs is extrapolated. In addition we discuss normal state electrical transport properties of La(O{sub 1-x}F{sub x})FeAs and Nd(O{sub 1-x}F{sub x})FeAs thin films.

  20. Thermodynamic and transport properties of superconducting Mg10B2.

    Science.gov (United States)

    Finnemore, D K; Ostenson, J E; Bud'ko, S L; Lapertot, G; Canfield, P C

    2001-03-12

    Transport and thermodynamic properties of a sintered pellet of the newly discovered MgB2 superconductor have been measured to determine the characteristic critical magnetic fields and critical current densities. Both resistive transition and magnetization data give similar values of the upper critical field, Hc2, with magnetization data giving dHc2/dT = 0.44 T/K at the transition temperature of Tc = 40.2 K. Close to the transition temperature, magnetization curves are thermodynamically reversible, but at low temperatures the trapped flux can be on the order of 1 T. The value of dHc/dT at Tc is estimated to be about 12 mT/K, a value similar to classical superconductors like Sn. Hence, the Ginzburg-Landau parameter kappa approximately 26. Estimates of the critical supercurrent density, Jc, using hysteresis loops and the Bean model, give critical current densities on the order of 10(5) A/cm2. Hence the supercurrent coupling through the grain boundaries is comparable to intermetallics like Nb3Sn.

  1. Pressure tuning of structure, superconductivity, and novel magnetic order in the Ce-underdoped electron-doped cuprate T '-Pr1.3 -xLa0.7CexCuO4 (x =0.1 )

    Science.gov (United States)

    Guguchia, Z.; Adachi, T.; Shermadini, Z.; Ohgi, T.; Chang, J.; Bozin, E. S.; von Rohr, F.; dos Santos, A. M.; Molaison, J. J.; Boehler, R.; Koike, Y.; Wieteska, A. R.; Frandsen, B. A.; Morenzoni, E.; Amato, A.; Billinge, S. J. L.; Uemura, Y. J.; Khasanov, R.

    2017-09-01

    High-pressure neutron powder diffraction, muon-spin rotation, and magnetization studies of the structural, magnetic, and the superconducting properties of the Ce-underdoped superconducting (SC) electron-doped cuprate system with the Nd2CuO4 (the so-called T')structure T '-Pr1.3 -xLa0.7CexCuO4 with x =0.1 are reported. A strong reduction of the in-plane and out-of-plane lattice constants is observed under pressure. However, no indication of any pressure-induced phase transition from T'to the K2NiF4 (the so-called T) structure is observed up to the maximum applied pressure of p = 11 GPa. Large and nonlinear increase of the short-range magnetic order temperature Tso in T '-Pr1.3 -xLa0.7CexCuO4 (x =0.1 ) was observed under pressure. Simultaneous pressure causes a nonlinear decrease of the SC transition temperature Tc. All these experiments establish the short-range magnetic order as an intrinsic and competing phase in SC T '-Pr1.3 -xLa0.7CexCuO4 (x =0.1 ). The observed pressure effects may be interpreted in terms of the improved nesting conditions through the reduction of the in-plane and out-of-plane lattice constants upon hydrostatic pressure.

  2. Size effects of nano-scale pinning centers on the superconducting properties of YBCO single grains

    Science.gov (United States)

    Moutalbi, Nahed; Noudem, Jacques G.; M'chirgui, Ali

    2014-08-01

    High pinning superconductors are the most promising materials for power engineering. Their superconducting properties are governed by the microstructure quality and the vortex pinning behavior. We report on a study of the vortex pinning in YBa2Cu3O7-x (YBCO) single grain with defects induced through the addition of insulating nano-particles. In order to improve the critical current density, YBCO textured bulk superconductors were elaborated using the Top Seeded Melt Texture and Growth process with different addition amounts of Al2O3 nano-particles. Serving as strong pinning centers, 0.05% excess of Al2O3 causes a significant enhancement of the critical current density Jc under self field and in magnetic fields at 77 K. The enhanced flux pinning achieved with the low level of alumina nano-particles endorses the effectiveness of insulating nano-inclusions to induce effectives pinning sites within the superconducting matrix. On the other side, we focused on the effect of the size of pinning centers on the critical current density. This work was carried out using two batches of alumina nano-particles characterized by two different particle size distributions with mean diameters PSD1 = 20 nm and PSD2 = 2.27 μm. The matching effects of the observed pinning force density have been compared. The obtained results have shown that the flux pinning is closely dependent on the size of the artificial pinning centers. Our results suggest that the optimization of the size of the artificial pinning centers is crucial to a much better understanding of the pinning mechanisms and therefore to insure high superconducting performance for the practical application of superconducting materials.

  3. Single crystals of superconducting SmFeAsO{sub 1-x}F{sub y} grown at high pressure

    Energy Technology Data Exchange (ETDEWEB)

    Zhigadlo, N D; Katrych, S; Bukowski, Z; Karpinski, J [Laboratory for Solid State Physics, ETH, 8093 Zuerich (Switzerland); Weyeneth, S [Physik-Institut der Universitaet Zuerich, Winterthurerstrasse 190, 8057 Zuerich (Switzerland); Puzniak, R [Institute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, 02-668 Warsaw (Poland)], E-mail: zhigadlo@phys.ethz.ch, E-mail: karpinski@phys.ethz.ch

    2008-08-27

    Single crystals of SmFeAsO{sub 1-x}F{sub y} of a size up to 120 x 100 {mu}m{sup 2} have been grown from NaCl/KCl flux at a pressure of 30 kbar and temperature of 1350-1450 deg. C using the cubic anvil high-pressure technique. The superconducting transition temperature of the obtained single crystals varies between 45 and 53 K. Obtained crystals are characterized by a full diamagnetic response in low magnetic fields and by a high critical current density in high magnetic fields. Structural refinement has been performed on the single crystal. Differential thermal analysis investigations at 1 bar Ar pressure show decomposition of SmFeAsO{sub 1-x}F{sub y} at 1302 deg. C. (fast track communication)

  4. Electrical and structural properties of the YBCO superconducting-semiconducting interface

    Energy Technology Data Exchange (ETDEWEB)

    Sobolewski, R. (Dept. of Electrical Engineering and Lab. for Laser Energetics, Univ. of Rochester, NY (United States) Inst. of Physics, Polish Academy of Sciences, Warszawa (Poland)); Xiong, W. (Dept. of Electrical Engineering and Lab. for Laser Energetics, Univ. of Rochester, NY (United States)); Kula, W. (Dept. of Electrical Engineering and Lab. for Laser Energetics, Univ. of Rochester, NY (United States) Inst. of Physics, Polish Academy of Sciences, Warszawa (Poland)); McIntyre, B. (Inst. of Optics, Univ. of Rochester, NY (United States))

    1994-02-01

    We report our studies on electrical and structural properties of an interface between the oxygen-poor (semiconducting) and oxygen-rich (superconducting, T[sub c] = 89.5 K) YBa[sub 2]Cu[sub 3]O[sub y]. Our thin-film test structures were fully monolithic and prepared by a laser-writing patterning technique. Scanning electron and optical microscopy measurements revealed that the interface was very sharp (<1 [mu]m wide) and did not smear over the period of several months. Electrical measurements of the interface showed completely linear current-voltage characteristics in the tested temperature range between 77 and 300 K. (orig.)

  5. Analysis of HOM Properties of Superconducting Parallel-Bar Deflecting/Crabbing Cavities

    Energy Technology Data Exchange (ETDEWEB)

    S.U. De Silva, J.R. Delayen

    2011-07-01

    The superconducting parallel-bar cavity is currently being considered for a number of deflecting and crabbing applications due to improved properties and compact design geometries. The 499 MHz deflecting cavity proposed for the Jefferson Lab 12 GeV upgrade and the 400 MHz crab cavity for the proposed LHC luminosity upgrade are two of the major applications. For high current applications the higher order modes must be damped to acceptable levels to eliminate any beam instabilities. The frequencies and R/Q of the HOMs and mode separation are evaluated and compared for different parallel-bar cavity designs.

  6. Silicon clathrates and carbon analogs: high pressure synthesis, structure, and superconductivity.

    Science.gov (United States)

    Yamanaka, Shoji

    2010-02-28

    Compounds with cage-like structures of elemental silicon and carbon are comparatively reviewed. Barium containing silicon clathrate compounds isomorphous with type I gas hydrates were prepared using high pressure and high temperature (HPHT) conditions, and found to become superconductors. The application of HPHT conditions to Zintl binary silicides have produced a number of silicon-rich cage-like structures including new clathrate structures; most of them are superconductors. Carbon analogs of silicon clathrates can be prepared by 3D polymerization of C(60) under HPHT conditions, which are new allotropes of carbon with expanded framework structures. The crystal chemistry and characteristic properties of some related compounds are also reviewed.

  7. Highly responsive ground state of PbTaSe2: Structural phase transition and evolution of superconductivity under pressure

    Science.gov (United States)

    Kaluarachchi, Udhara S.; Deng, Yuhang; Besser, Matthew F.; Sun, Kewei; Zhou, Lin; Nguyen, Manh Cuong; Yuan, Zhujun; Zhang, Chenglong; Schilling, James S.; Kramer, Matthew J.; Jia, Shuang; Wang, Cai-Zhuang; Ho, Kai-Ming; Canfield, Paul C.; Bud'ko, Sergey L.

    2017-06-01

    Transport and magnetic studies of PbTaSe2 under pressure suggest the existence of two superconducting phases with the low temperature phase boundary at ˜0.25 GPa that is defined by a very sharp, first order, phase transition. The first order phase transition line can be followed via pressure dependent resistivity measurements, and is found to be near 0.12 GPa near room temperature. Transmission electron microscopy and x-ray diffraction at elevated temperatures confirm that this first order phase transition is structural and occurs at ambient pressure near ˜425 K. The new, high temperature/high pressure phase has a similar crystal structure and slightly lower unit cell volume relative to the ambient pressure, room temperature structure. Based on first-principles calculations this structure is suggested to be obtained by shifting the Pb atoms from the 1 a to 1 e Wyckoff position without changing the positions of Ta and Se atoms. PbTaSe2 has an exceptionally pressure sensitive, structural phase transition with Δ Ts/Δ P ≈-1400 K/GPa near room temperature, and ≈-1700 K/GPa near 4 K. This first order transition causes a ˜1 K (˜25 % ) steplike decrease in Tc as pressure is increased through 0.25 GPa.

  8. High-pressure structural properties of tetramethylsilane

    Science.gov (United States)

    Zhen-Xing, Qin; Xiao-Jia, Chen

    2016-02-01

    High-pressure structural properties of tetramethylsilane are investigated by synchrotron powder x-ray diffraction at pressures up to 31.1 GPa and room temperature. A phase with the space group of Pnma is found to appear at 4.2 GPa. Upon compression, the compound transforms to two following phases: the phase with space groups of P21/c at 9.9 GPa and the phase with P2/m at 18.2 GPa successively via a transitional phase. The unique structural character of P21/c supports the phase stability of tetramethylsilane without possible decomposition upon heavy compression. The appearance of the P2/m phase suggests the possible realization of metallization for this material at higher pressure. Project supported by the Cultivation Fund of the Key Scientific and Technical Innovation Project from Ministry of Education of China (Grant No. 708070), the Fundamental Research Funds for the Central Universities, South China University of Technology (Grant No. 2014ZZ0069), the National Natural Science Foundation of China (Grant No. 51502189), and the Doctoral Project of Taiyuan University of Science and Technology, China (Grant No. 20132010).

  9. Statistical correlations for thermophysical properties of Supercritical Argon (SCAR) used in cooling of futuristic High Temperature Superconducting (HTS) cables

    Science.gov (United States)

    Kalsia, Mohit; Dondapati, Raja Sekhar; Usurumarti, Preeti Rao

    2017-05-01

    High Temperature Superconducting (HTS) cables are emerging as an alternative to conventional cables in efficient power transmission. However, these HTS cables require cooling below the critical temperature of superconductors used to transmit larger currents. With the invention of high temperature superconductors whose critical temperatures are up to 134 K (Hg based), it is a great challenge to identify a suitable coolant which can carry away the heating load on the superconductors. In order to accomplish such challenge, an attempt has been made in the present work to propose supercritical Argon (SCAR) as the alternative to cool the HTS cables. Further, a statistical correlation has been developed for the thermophysical properties such as density, viscosity, specific heat and thermal conductivity of SCAR. In addition, the accuracy of developed correlations is established with the help of few statistical parameters and validated with standard database available in the literature. These temperature dependent accurate correlations are useful in predicting the pressure drop and heat transfer behaviour in HTS cables using numerical or computational techniques. In recent times, with the sophistication of computer technology, solving of various complex transport equations along with the turbulence models became popular and hence the developed correlations would benefit the technological community. It is observed that, a decrease in pressure, density and viscosity are found to be decreasing whereas the thermal conductivity and specific heat increase significantly. It can be concluded that higher heat transfer rate and lower pumping power can be achieved with SCAR as coolant in the HTS cables.

  10. Thermo-mechanical properties of epoxy GFRPs used in superconducting magnet winding

    Science.gov (United States)

    Usami, S.; Suzuki, T.; Ejima, H.; Asano, K.

    A tightly constructed rigid structure of a conductor winding and GFRP spacers in a coil case is an essential element for a superconducting magnet, that is to operate at a cryogenic temperature and sustain large magnetic forces. However, the contact pressures on the conductor, the spacers and the coil case, which are imposed in fabrication process, may be greatly reduced by relaxation at room temperature and by thermal contraction in the GFRP spacers during cool-down process. We therefore studied 61 kinds of commercial and test GFRPs and established a basis for suitable GFRP spacer material to be used in superconducting magnet windings. Glass transition temperature, Tg, of the impregnating resin plays an important role in transverse creep deformation of GFRPs. GFRP spacers with Tg above 423 K can maintain 80% of the initial pressure in a winding for two years at room temperature. This result was obtained by utilizing the transverse creep moduli of GFRPs at different temperatures and the time-temperature superposition principle. Transverse thermal contraction from 293 to 4 K decreases uniformly in all GFRPs as the resin weight content, Rc, decreases. Also, contraction is smaller than that of the 304 stainless steel used for the coil case when Rc is less than 15%. As a result, pressure decrease in the winding can be prevented during cool-down. The elastic modulus in the transverse direction of a GFRP is calculated by dividing the elastic modulus of the impregnating resin by Rc. Fractures of the GFRPs at low temperatures are primarily in shear mode under four-point bending, in-plane compression, transverse compression, or interlaminar shear loading. Moreover, the transverse-compressive fatigue limit of plain-woven GFRP at low temperature depends on the maximum compressive stress of the cyclic loading under high mean-compressive stress and the stress range under low mean-compressive stress.

  11. Influence of preparation conditions on superconducting properties of Bi-2223 thin films

    Indian Academy of Sciences (India)

    N T Mua; A Sundaresan; N K Man; D D Dung

    2014-02-01

    We report electrical transport properties of Bi2Sr2Ca2Cu3O10+ (Bi-2223) superconducting thin films fabricated by pulsed-laser deposition on SrTiO3 substrate. The aim of the study was to investigate the influence of preparation conditions such as deposition temperature (S), annealing time (A) and deposition rate (). A critical temperature (c) as high as 110 K and critical current density (c) of 6.2 × 106 A/cm2 at 20 K were obtained for S = 760° C, A = 4h and = 1.5 Å/s. We also investigated the effect of Li doping on Bi-2223 thin films. Li intercalation results in high resistive onset transition temperature and the resistivity shows broadening in magnetic field that increases with field. The large broadening of resistivity curve in magnetic field suggests that this phenomenon is directly related to the intrinsic superconducting properties of the copper oxide superconductors. The sudden drop in c at relatively low magnetic field ( < 0.5 tesla) is due to the effect of Josephson weak-links at the grain boundaries.

  12. Heat treatment effects on the superconducting properties of Ag-doped SrKFeAs compounds

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The superconducting properties of polycrystalline Sr0.6K0.4Fe2As2 were strongly influenced by Ag doping(Supercond.Sci.Technol.23(2010) 025027).Ag addition is mainly dominated by silver diffusing,so the annealing process is one of the essential factors to achieve high quality Ag doped Sr0.6K0.4Fe2As2.In this paper,the optimal annealing conditions were studied for Ag doped Sr0.6K0.4Fe2As2 bulks prepared by a one-step solid reaction method.It is found that the annealing temperature has a strong influence on the superconducting properties,especially on the critical current density Jc.As a result,higher heat treatment temperature(~900℃) is helpful in diffusing Ag and reducing the impurity phase gathered together to improve the grain connectivity.In contrast,low-temperature sintering is counterproductive for Ag doped samples.These results clearly suggest that annealing at ~900℃ is necessary for obtaining high Jc Ag-doped samples.

  13. Elastic properties of superconducting bulk metallic glasses; Elastische Eigenschaften von supraleitenden massiven metallischen Glaesern

    Energy Technology Data Exchange (ETDEWEB)

    Hempel, Marius

    2015-07-01

    Within the framework of this thesis the elastic properties of a superconducting bulk metallic glass between 10 mK and 300 K were first investigated. In order to measure the entire temperature range, in particular the low temperature part, new experimental techniques were developed. Using an inductive readout scheme for a double paddle oscillator it was possible to determine the internal friction and the relative change of sound velocity of bulk metallic glasses with high precision. This allowed for a detailed comparison of the data with different models. The analysis focuses on the low temperature regime where the properties of glassy materials are governed by atomic tunneling systems as described by the tunneling model. The influence of conduction electrons in the normal conducting state and quasiparticles in the superconducting state of the glass were accounted for in the theoretical description, resulting in a good agreement over a large temperature range between measured data and prediction of the tunneling model. This allowed for a direct determination of the coupling constant between electrons and tunneling systems. In the vicinity of the transition temperature Tc the data can only be described if a modified distribution function of the tunneling parameters is applied.

  14. The effects of disorder on the normal state and superconducting properties of Nb3Sn

    Science.gov (United States)

    Mentink, M. G. T.; Dhalle, M. M. J.; Dietderich, D. R.; Godeke, A.; Hellman, F.; ten Kate, H. H. J.

    2017-02-01

    The effect of disorder on the normal state resistivity and the superconducting properties of Nb{}3Sn is explored in a combination of ab initio calculations and microscopic theory. The crystal symmetry is calculated to be preferentially tetragonal at a normal state resistivity below 27.0 ± 1.4 μ {{Ω }}{cm}, and preferentially cubic above this value, which is shown to be consistent with the experimentally observed transition point. The phonon density of states, the Eliashberg spectrum {α }2(ω )F(ω ), the electron-phonon coupling constant, the characteristic frequency, the critical temperature T c, and the upper critical magnetic field at 0 K {H}{{c}2}(0) are calculated over a large normal state resistivity range and shown to be consistent with experimental observations. The high degree of consistency between the calculation results and experimental observations is a strong indication that the calculation approach utilized here, a combination of ab initio calculations and microscopic theory, is a useful tool for understanding the superconducting and normal state properties of Nb{}3Sn.

  15. A visualization instrument to investigate the mechanical-electro properties of high temperature superconducting tapes under multi-fields

    Science.gov (United States)

    Liu, Wei; Zhang, Xingyi; Liu, Cong; Zhang, Wentao; Zhou, Jun; Zhou, YouHe

    2016-07-01

    We construct a visible instrument to study the mechanical-electro behaviors of high temperature superconducting tape as a function of magnetic field, strain, and temperature. This apparatus is directly cooled by a commercial Gifford-McMahon cryocooler. The minimum temperature of sample can be 8.75 K. A proportion integration differentiation temperature control is used, which is capable of producing continuous variation of specimen temperature from 8.75 K to 300 K with an optional temperature sweep rate. We use an external loading device to stretch the superconducting tape quasi-statically with the maximum tension strain of 20%. A superconducting magnet manufactured by the NbTi strand is applied to provide magnetic field up to 5 T with a homogeneous range of 110 mm. The maximum fluctuation of the magnetic field is less than 1%. We design a kind of superconducting lead composed of YBa2Cu3O7-x coated conductor and beryllium copper alloy (BeCu) to transfer DC to the superconducting sample with the maximum value of 600 A. Most notably, this apparatus allows in situ observation of the electromagnetic property of superconducting tape using the classical magnetic-optical imaging.

  16. Upper critical field, pressure-dependent superconductivity and electronic anisotropy of Sm4Fe2As2Te(1-x)O(4-y)F(y).

    Science.gov (United States)

    Pisoni, A; Katrych, S; Szirmai, P; Náfrádi, B; Gaál, R; Karpinski, J; Forró, L

    2016-03-23

    We present a detailed study of the electrical transport properties of a recently discovered iron-based superconductor: Sm4Fe2As2Te0.72O2.8F1.2. We followed the temperature dependence of the upper critical field by resistivity measurement of single crystals in magnetic fields up to 16 T, oriented along the two main crystallographic directions. This material exhibits a zero-temperature upper critical field of 90 T and 65 T parallel and perpendicular to the Fe2As2 planes, respectively. An unprecedented superconducting magnetic anisotropy γH=H(c2)(ab)/H(c2)(c) ~ 14 is observed near Tc, and it decreases at lower temperatures as expected in multiband superconductors. Direct measurement of the electronic anisotropy was performed on microfabricated samples, showing a value of ρ(c)/ρ(ab)(300K) ~ 5 that rises up to 19 near Tc . Finally, we have studied the pressure and temperature dependence of the in-plane resistivity. The critical temperature decreases linearly upon application of hydrostatic pressure (up to 2 GPa) similarly to overdoped cuprate superconductors. The resistivity shows saturation at high temperatures, suggesting that the material approaches the Mott-Ioffe-Regel limit for metallic conduction. Indeed, we have successfully modelled the resistivity in the normal state with a parallel resistor model that is widely accepted for this state. All the measured quantities suggest strong pressure dependence of the density of states.

  17. Optical investigation of BaFe2(As0.77P0.23)2 : Spin-fluctuation-mediated superconductivity under pressure

    Science.gov (United States)

    Uykur, E.; Kobayashi, T.; Hirata, W.; Miyasaka, S.; Tajima, S.; Kuntscher, C. A.

    2017-06-01

    Temperature-dependent reflectivity measurements in the frequency range 75-8000 cm-1 were performed on BaFe2(As0.77P0.23)2 single crystals under pressure up to ˜5 GPa . The obtained optical conductivity spectra have been analyzed to extract the electron-boson spectral density α2F (Ω ) . A sharp resonance peak was observed in α2F (Ω ) upon the superconducting transition, persisting throughout the applied pressure range. The energy and temperature dependences of this peak are consistent with the superconducting gap opening. Furthermore, several similarities with other experimental probes such as inelastic neutron scattering (INS) [D. S. Inosov et al., Nat. Lett. 6, 178 (2010), 10.1038/nphys1483] give evidence for the coupling to a bosonic mode, possibly due to spin fluctuations. Moreover, electronic correlations have been calculated via spectral weight analysis, which revealed that the system stays in the strongly correlated regime throughout the applied pressure range. However, a comparison to the parent compound showed that the electronic correlations are slightly decreased with P doping. The investigation of the phase diagram obtained by our optical study under pressure also revealed the coexistence of the spin-density wave and the superconducting regions, where the coexistence region shifts to the lower pressure range with increasing P content. Moreover, the optimum pressure range, where the highest superconducting transition temperature has been obtained, shows a nonlinear decrease with increasing P content.

  18. Superconducting properties of “111” type LiFeAs iron arsenide single crystals

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    LiFeAs single crystal has been grown with superconducting transition temperature Tc comparable to that of polycrystals.A magnetic transition is found at about 160 K,which suggests the correlation of superconductivity with spin wave density.

  19. Enhancement of superconductivity under pressure and the magnetic phase diagram of tantalum disulfide single crystals

    Science.gov (United States)

    Abdel-Hafiez, M.; Zhao, X.-M.; Kordyuk, A. A.; Fang, Y.-W.; Pan, B.; He, Z.; Duan, C.-G.; Zhao, J.; Chen, X.-J.

    2016-08-01

    In low-dimensional electron systems, charge density waves (CDW) and superconductivity are two of the most fundamental collective quantum phenomena. For all known quasi-two-dimensional superconductors, the origin and exact boundary of the electronic orderings and superconductivity are still attractive problems. Through transport and thermodynamic measurements, we report on the field-temperature phase diagram in 2H-TaS2 single crystals. We show that the superconducting transition temperature (Tc) increases by one order of magnitude from temperatures at 0.98 K up to 9.15 K at 8.7 GPa when the Tc becomes very sharp. Additionally, the effects of 8.7 GPa illustrate a suppression of the CDW ground state, with critically small Fermi surfaces. Below the Tc the lattice of magnetic flux lines melts from a solid-like state to a broad vortex liquid phase region. Our measurements indicate an unconventional s-wave-like picture with two energy gaps evidencing its multi-band nature.

  20. Pressure effect on superconductivity in Cd{sub 2}Re{sub 2}O{sub 7}

    Energy Technology Data Exchange (ETDEWEB)

    Fujiwara, K; Morimoto, K; Maeda, E [Department of Materials Science, Shimane University, Matsue 690-8504 (Japan); Nishigori, S, E-mail: fujiwara@riko.shimane-u.ac.j [Department of Matrials Analysis, CIRS, Shimane University, Matsue 690-8504 (Japan)

    2010-01-15

    {sup 188/187}Re nuclear quadrupole resonance (NQR) and ac susceptibility measurements in Cd{sub 2}Re{sub 2}O{sub 7} have been performed to study correlation between superconductivity and structural transition (T{sub s1} = 200 K and T{sub s2} = 120 K at ambient pressure) under high pressure, using a hybrid piston cylinder-type high-pressure cell. T{sub c} is almost pressure independent below 1 GPa, while, above 1 GPa, T{sub c} increases monotonously and reaches up to 2.3 K at 2.5 GPa. The {sup 188/187}Re-NQR spectrum for {+-}3/2 {r_reversible} {+-}5/2 transition broadens and shifts to lower frequency with applying pressure. Furthermore, Re NQR spectrum broadens suddenly around 2GPa, suggesting that electric field gradient at Re sites distributes extendedly, which may be related to the disorder state with suppressing T{sub s2} down to {approx} 0 K.

  1. Correlation of normal and superconducting properties and unified approach to the description of high Tc oxides

    Science.gov (United States)

    Kresin, V. Z.; Wolf, S. A.

    1991-01-01

    We present a unified approach based on the Fermi liquid picture which allows us to describe the normal as well as the superconducting properties of the doped cuprates. The theory that is presented is for the doped compounds which are metallic. One can distinguish two interrelated, but nevertheless, different directions in the physics of high T(sub c): one involving the problem of carrier doping and the transition to the metallic state, and the second being the description of the metallic state. It is important that this metallic phase undergoes the transition into the superconducting state; as a result, our analysis is directly related to the origin of high T(sub c). We are using a quasi-2D Fermi liquid model to estimate the fundamental parameters of these very interesting materials. We find that this description is able to describe these materials and also that phonons and plasmons play a major role in the mechanism of high T(sub c).

  2. Improving superconducting properties of YBCO high temperature superconductor by Graphene Oxide doping

    Energy Technology Data Exchange (ETDEWEB)

    Dadras, S., E-mail: dadras@alzahra.ac.ir; Dehghani, S.; Davoudiniya, M.; Falahati, S.

    2017-06-01

    In this research, we report the synthesis and characterization of YBa{sub 2}Cu{sub 3}O{sub 7-δ} (YBCO) high temperature superconductor prepared by sol-gel method and doped with Graphene Oxide (GO) in different weight percentages, 0, 0.1, 0.7 and 1 % wt. The x-ray diffraction (XRD) analysis confirms the formation of orthorhombic phase of superconductivity for all the prepared samples. We found that GO doping reduces the crystalline size of the samples. We evaluated the effects of GO doping on the normal state resistivity (ρ), superconducting transition temperature (T{sub c}) and critical current density (J{sub c}). The results show that the GO doping has a positive effect on these properties. Also, the highest J{sub c} is obtained for the 0.7 %wt GO doped YBCO compound that its critical current density is about 15 times more than the J{sub c} of pure one in 0.4 T magnetic field. The scanning electron microscope (SEM) analysis shows that there are better connections between the grains of GO doped samples. - Highlights: • Graphene Oxide doping increased the YBCO critical current density. • Graphene Oxide creates a better connection between the YBCO grains. • The normal resistivity of samples were decreased by GO doping to YBCO compounds. • Graphene Oxide doping has a positive effect on the critical transition temperature.

  3. Analysis of the local superconducting properties in YBCO coated conductors with striations

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Mu Yong; Park, Sang Kook; Park, Hee Yeon; Ri, Hyeong Cheol [Dept. of Physics, Kyungpook National University, Daegu (Korea, Republic of)

    2015-06-15

    In order to realize economical applications, it is important to reduce the ac loss of 2G high-temperature superconductor coated conductors. It seems to be reasonable that a multi-filamentary wire can decrease the magnetization loss. In this study, we prepared two samples of YBCO coated conductors with striations. We measured local superconducting properties of both samples by using Low Temperature Scanning Laser and Hall Probe Microscopy (LTSLHPM). The distribution of the local critical temperature of samples was analyzed from experimental results of Low Temperature Scanning Laser Microscopy (LTSLM) near the superconducting transition temperature. According to LTSLM results, spatial distributions of the local critical temperature of both samples are homogeneous. The local current density and the local magnetization in samples were explored from measuring stray fields by using Scanning Hall Probe Microscopy (SHPM). From SHPM results, the remanent field pattern of the one bridge sample in an external magnetic field confirms the Bean's critical state model and the three bridge sample has similar remanent field pattern of the one bridge sample. The local magnetization curve in the three bridge sample was measured from external fields from -500 Oe to 500 Oe. We visualized that the distribution of local hysteresis loss are related in the distribution of the remanent field of the three bridge sample. Although the field dependence of the critical current density must be taken into account, the relation of the local hysteresis loss and the remanent field from Bean's model was useful.

  4. High Pressure Laminates with Antimicrobial Properties

    Directory of Open Access Journals (Sweden)

    Sandra Magina

    2016-02-01

    Full Text Available High-pressure laminates (HPLs are durable, resistant to environmental effects and good cost-benefit decorative surface composite materials with special properties tailored to meet market demand. In the present work, polyhexamethylene biguanide (PHMB was incorporated for the first time into melamine-formaldehyde resin (MF matrix on the outer layer of HPLs to provide them antimicrobial properties. Chemical binding of PHMB to resin matrix was detected on the surface of produced HPLs by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR. Antimicrobial evaluation tests were carried out on the ensuing HPLs doped with PHMB against gram-positive Listeria innocua and gram-negative Escherichia coli bacteria. The results revealed that laminates prepared with 1.0 wt % PHMB in MF resin were bacteriostatic (i.e., inhibited the growth of microorganisms, whereas those prepared with 2.4 wt % PHMB in MF resin exhibited bactericidal activity (i.e., inactivated the inoculated microorganisms. The results herein reported disclose a promising strategy for the production of HPLs with antimicrobial activity without affecting basic intrinsic quality parameters of composite material.

  5. Direct evidence for a pressure-induced nodal superconducting gap in the Ba0.65Rb0.35Fe2As2 superconductor

    Science.gov (United States)

    Guguchia, Z.; Amato, A.; Kang, J.; Luetkens, H.; Biswas, P. K.; Prando, G.; von Rohr, F.; Bukowski, Z.; Shengelaya, A.; Keller, H.; Morenzoni, E.; Fernandes, Rafael M.; Khasanov, R.

    2015-01-01

    The superconducting gap structure in iron-based high-temperature superconductors (Fe-HTSs) is non-universal. In contrast to other unconventional superconductors, in the Fe-HTSs both d-wave and extended s-wave pairing symmetries are close in energy. Probing the proximity between these very different superconducting states and identifying experimental parameters that can tune them is of central interest. Here we report high-pressure muon spin rotation experiments on the temperature-dependent magnetic penetration depth in the optimally doped nodeless s-wave Fe-HTS Ba0.65Rb0.35Fe2As2. Upon pressure, a strong decrease of the penetration depth in the zero-temperature limit is observed, while the superconducting transition temperature remains nearly constant. More importantly, the low-temperature behaviour of the inverse-squared magnetic penetration depth, which is a direct measure of the superfluid density, changes qualitatively from an exponential saturation at zero pressure to a linear-in-temperature behaviour at higher pressures, indicating that hydrostatic pressure promotes the appearance of nodes in the superconducting gap. PMID:26548650

  6. Effects of oxide precursors on superconducting properties of polycrystalline SmFeAsO{sub 1−x}F{sub x}

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, F.F.; Ding, Y.; Sun, Y.; Zhuang, J.C.; Zhou, W. [Department of Physics and Key Laboratory of MEMS of the Ministry of Education, Southeast University, Nanjing 211189 (China); Li, G.Z.; Sumption, M. [Center for Superconducting and Magnetic Materials (CSMM), Department of Materials Science and Engineering, The Ohio State University, Columbus, OH 43210 (United States); Li, X.W. [School of Physics and Electronic Electrical Engineering, Huaiyin Normal University, Huaian 223300 (China); State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Science, Shanghai 200050 (China); Shi, Z.X., E-mail: zxshi@seu.edu.cn [Department of Physics and Key Laboratory of MEMS of the Ministry of Education, Southeast University, Nanjing 211189 (China)

    2013-12-15

    Highlights: •Polycrystalline SmFeAsO{sub 1−x}F{sub x} samples were prepared by different oxide precursors. •Phase formation and superconductivity of these samples were comparatively studied. •Results show that nano-Fe{sub 2}O{sub 3} and As{sub 2}O{sub 3} promote fluorine doping. -- Abstract: A series of polycrystalline SmFeAsO{sub 1−x}F{sub x} samples were synthesized by one-step and two-step method at ambient pressure using different oxide precursors, namely As{sub 2}O{sub 3}, Fe{sub 2}O{sub 3} and nano-Fe{sub 2}O{sub 3} powder, as the source of element O. Results of X-ray diffraction and magnetic measurements manifest that starting oxides affected the phase formation and superconducting properties of SmFeAsO{sub 1−x}F{sub x}. As{sub 2}O{sub 3} as oxide precursor contributes to the fast formation of superconducting phase for a short period of sintering time. And samples prepared using As{sub 2}O{sub 3} show higher superconducting transition temperature T{sub c} and more stable fluorine doping level. Compared with Fe{sub 2}O{sub 3}, nano-Fe{sub 2}O{sub 3} promotes fluorine doping into the O site. While using Fe{sub 2}O{sub 3} leads to higher level of Fe and SmOF impurities. The critical current density J{sub cm} were derived from magnetic hysteresis loops. Sample prepared using As{sub 2}O{sub 3} shows higher J{sub cm} in low temperature and high magnetic fields.

  7. Physical Properties of Niobium and Specifications for Fabrication of Superconducting Cavities

    Energy Technology Data Exchange (ETDEWEB)

    Antoine, C.; Foley, M.; Dhanaraj, N.; /Fermilab

    2011-07-01

    It is important to distinguish among the properties of niobium, the ones that are related to the cavity's SRF performances, the formability of the material, and the mechanical behavior of the formed cavity. In general, the properties that dictate each of the above mentioned characteristics have a detrimental effect on one another and in order to preserve the superconducting properties without subduing the mechanical behavior, a balance has to be established. Depending on the applications, some parameters become less important and an understanding of the physical origin of the requirements might help in this optimization. SRF applications require high purity niobium (high RRR), but pure niobium is very soft from fabrication viewpoint. Moreover conventional fabrication techniques tend to override the effects of any metallurgical process meant to strengthen it. As those treatments dramatically affect the forming of the material they should be avoided. These unfavorable mechanical properties have to be accounted for in the design of the cavities rather than in the material specification. The aim of this paper is to review the significance of the important mechanical properties used to characterize niobium and to present the optimal range of values. Most of the following information deals with the specification of sheets for cell forming unless otherwise noted.

  8. Microstructural and transport properties of superconducting FeTe0.65Se0.35 crystals

    Science.gov (United States)

    Sivakov, A. G.; Bondarenko, S. I.; Prokhvatilov, A. I.; Timofeev, V. P.; Pokhila, A. S.; Koverya, V. P.; Dudar, I. S.; Link, S. I.; Legchenkova, I. V.; Bludov, A. N.; Monarkha, V. Yu; Gawryluk, D. J.; Pietosa, J.; Berkowski, M.; Diduszko, R.; Puzniak, R.; Wisniewski, A.

    2017-01-01

    The issue concerning the nature and the role of microstructural inhomogeneities in iron chalcogenide superconducting crystals of FeTe0.65Se0.35 and their correlation with transport properties of this system was addressed. The presented data demonstrate that chemical disorder originating from the kinetics of the crystal growth process significantly influences the superconducting properties of an Fe-Te-Se system. Transport measurements of the transition temperature and critical current density performed for microscopic bridges allow us to deduce the local properties of a superconductor with microstructural inhomogeneities, and significant differences were noted. The variances observed in the local properties were explained as a consequence of weak superconducting links existing in the studied crystals. The results confirm that the inhomogeneous spatial distribution of ions and small hexagonal symmetry nanoscale regions with nanoscale phase separation also seem to enhance the superconductivity in this system with respect to the values of the critical current density. Magnetic measurements performed in order to determine, in an alternative way, the values of the critical current density, as well as to find the relaxation rate and to check the scaling of the pinning force, confirm the conclusions drawn from the transport measurements.

  9. Enhanced superconductivity of SmFeAsO co-doped by Scandium and Fluorine to increase chemical inner pressure

    Science.gov (United States)

    Chen, Haijie; Zheng, Ming; Fang, Aihua; Yang, Jianhua; Huang, Fuqiang; Xie, Xiaoming; Jiang, Mianheng

    2012-10-01

    Sm1-x/3Scx/3FeAsO1-xFx (x=0.09-0.27) were synthesized by the mechanical alloying and subsequent low temperature rapid sintering (2 h at 950 °C). The superconducting transition temperature (Tc) increased with the doping level of x. The optimal doping achieved a Tc up to 53.5 K in Sm0.93Sc0.07FeAsO0.79F0.21. The higher Tc value was attributed to the increased chemical inner pressure from local lattice distortion induced by smaller-size dopants, which was further confirmed by Sm1-xScxFeAsO0.88F0.12 (x=0.04, 0.08, 0.12). Accordingly, larger lattice distortion can enhance the superconductivity below the doping limit. Similar phenomenon was also observed in the La1-xYxFeAsO0.8F0.2 (x=0.4, 0.5, 0.6).

  10. Neutron irradiation damage effect on superconducting and normal state properties of the YBa 2Cu 3O 7 system

    Science.gov (United States)

    Przysłupski, P.; Wiśniewski, A.; Koleśnik, S.; Dobrowolski, W.; Pajączkowska, A.; Pytel, K.; Pytel, B.

    1988-06-01

    Effect of irradiation by fast neutrons on superconducting and normal state properties of the YBa 2Cu 3O 7 samples is presented. Transport measurements showed a degradation of all superconducting parameters, especially the transport critical current density. Critical current densities obtained from magnetization data exhibited a substantial increase / about 15 times at 77 K and H = 10 kOe/ after the irradiation with the fluence in the range 2.4·10 17 ÷ 8.7 · 10 17 n/cm 2. Such an anomalous bahavior is explained in terms of neutron created defects at intergrain regions and improved intragrain pinning.

  11. Electronic structure, magnetic and superconducting properties of co-doped iron-arsenide superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Rosner, Helge; Schnelle, Walter; Nicklas, Michael; Leithe-Jasper, Andreas [MPI CPfS Dresden (Germany); Weikert, Franziska [Los Alamos National Laboratory, New Mexico (United States); HLD Dresden Rossendorf (Germany); Wosnitza, Joachim [HLD Dresden Rossendorf (Germany)

    2013-07-01

    We present a joint experimental and theoretical study of co-doped iron-arsenide superconductors of the 122 family A{sub 1-x}K{sub x}Fe{sub 2-y}T{sub y}As{sub 2} (A = Ba,Sr,Eu; T = Co,Ru,Rh). In these systems, the co-doping enables the separation of different parameters - like electron count, disorder or the specific geometry of the FeAs layer - with respect to the position of the respective compounds in the general 122 phase diagram. For a series of compounds, we investigate the relevance of the different parameters for the magnetic, thermodynamic and superconducting properties. Our experimental investigations are supported by density functional electronic structure calculations applying different approximations for doping and disorder.

  12. An AFM study of the morphology and local mechanical properties of superconducting YBCO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Soifer, Ya.M.; Verdyan, A.; Azoulay, J.; Kazakevich, M.; Rabkin, E

    2004-02-01

    The morphology of thin superconducting YBCO films deposited on sapphire and on SrTiO{sub 3} was studied with the help of atomic force and scanning electron microscopies. The intrinsic mechanical properties in the flat, particles-free and chemically homogeneous regions of the films were determined with the aid of nanoindenting atomic force microscope. Also the microscopy studies revealed the difference in topography of the films, the nanohardness and Young's modulus of two films were very close to each other. For the indents shallower than 0.2 of the film thickness the Young's modulus and hardness of the films on two different substrates converged to the values of 210 and 8.5 GPa, respectively. The possible deformation mechanisms determining the localized deformation of intrinsically brittle ceramic films are discussed.

  13. An AFM study of the morphology and local mechanical properties of superconducting YBCO thin films

    Science.gov (United States)

    Soifer, Ya. M.; Verdyan, A.; Azoulay, J.; Kazakevich, M.; Rabkin, E.

    2004-02-01

    The morphology of thin superconducting YBCO films deposited on sapphire and on SrTiO 3 was studied with the help of atomic force and scanning electron microscopies. The intrinsic mechanical properties in the flat, particles-free and chemically homogeneous regions of the films were determined with the aid of nanoindenting atomic force microscope. Also the microscopy studies revealed the difference in topography of the films, the nanohardness and Young’s modulus of two films were very close to each other. For the indents shallower than 0.2 of the film thickness the Young’s modulus and hardness of the films on two different substrates converged to the values of 210 and 8.5 GPa, respectively. The possible deformation mechanisms determining the localized deformation of intrinsically brittle ceramic films are discussed.

  14. Structural properties of strained YBa2Cu3O6+x superconducting films grown by pulsed laser deposition

    Science.gov (United States)

    Ariosa, Daniel; Abrecht, M.; Pavuna, Davor; Onellion, Marshall

    2000-09-01

    In YBa2Cu3O6+x compound the tetragonal to orthorhombic transition occurs around x equals 0.3, followed by a continuum variation of lattice parameters. Hence both, the structural and superconducting properties, depend upon the oxygen content in CuO chains. Conversely, the epitaxial stress, exerted by the substrate on YBCO films, modified the lattice parameters influencing the oxygen stability in the chains. The understanding of this mechanism is essential when growing epitaxial films for in- situ photoemission studies as well as for tunneling experiments, since the oxygen stability up to the top surface unit-cell is a central issue. We have studied this effect on c-axis oriented YBCO films grown by laser ablation on (001) STO single crystals. Accurate x-ray diffraction analysis of thick films (t GRT 500 angstrom) indicates the presence of two distinct layers, one strained and the other relaxed. Detailed analysis shows that the relaxed layer is as well oxidized as bulk samples, while the strained one is oxygen deficient. Furthermore, despite an oxygen content of about x equals 0.65, the strained layer is in the tetragonal phase (in bulk, the tetragonal phase exists for x < 0.3). We discuss these results in terms of competition between the chemical pressure induced by oxygen inclusion in the chains, and the uniaxial stress within the film.

  15. Effect of Er doping on the superconducting properties of porous MgB2

    Indian Academy of Sciences (India)

    O Erdem; E Yanmaz

    2015-02-01

    MgB2 bulk sample with porous structure was produced by using the in-situ solid-state reaction method under argon (Ar) atmosphere of 10 bar. Elemental Er in powder form was doped into MgB2 with different compositions (Mg1−Er)B2, where = 0.00, 0.03 and 0.05, in order to investigate the effect of rare-earth (RE) element Er on the structural and electromagnetic properties of porous MgB2. The Er-doped samples result in small grain size structure compared to the undoped one. The lattice constants and of the doped samples, determined from X-ray diffraction (XRD) analysis, increase with the increasing Er content, and consequently the superconducting transition temperature ($T^{\\text{onset}}_{c}$) of MgB2, determined from resistivity measurements, is slightly suppressed. Also, the upper critical field ($B_{c2}$), the irreversibility field ($B_{\\text{irr}}$) and the critical current density ($J_{c}$) values are significantly enhanced in the doped samples. For the best sample ( = 0.03), at 15 K under a magnetic field of 4 T, the $J_{c}$ value reaches 2.4×104 A cm-2, which is higher than that of the porous sample by an order of 103, and the $B_{\\text{irr}}$ value at 20 K reaches 9.7 T. These results imply that the RE element Er fills the pores, enhances the density and the grain connectivity. Hence, the superconducting properties of the porous MgB2 sample improve by Er doping.

  16. Normal and superconducting properties in the Ca 1-xCd xLaBaCu 3O y system

    Science.gov (United States)

    Zhang, X.-J.; Wang, J.-S.; Xu, Z.-A.; Jiao, Z.-K.; Zhang, Q. R.

    1994-11-01

    The superconducting behavior of the superconductor CaLaBaCu 3O y (CLBCO) has been studied as a function of substitution of Cd for Ca. Electrical resistivity measurements show that the superconducting critical temperature ( Tc) decreases monotonously with increasing substituent Cd concentration x. Within the composition range O⩽ x⩽1, the samples remain in single phase. Thermogravimetry (TG) studies of the samples show that the oxygen content greatly influences the normal and superconducting properties of the Ca 1- xCd xLaBaCu 3O y system. The substitution of Cd for Ca leads to deficiencies of oxygen in Cu-O chain. As the substituent Cd concentration x increases, the oxygen content decreases monotonously. It is concluded that the reason why Cd leads to the suppression of Tc is the reduction of oxygen content caused by substitution of Cd for Ca.

  17. Synthesis of fullerene nanowhiskers using the liquid-liquid interfacial precipitation method and their mechanical, electrical and superconducting properties

    Science.gov (United States)

    Miyazawa, Kun'ichi

    2015-02-01

    Fullerene nanowhiskers (FNWs) are thin crystalline fibers composed of fullerene molecules, including C60, C70, endohedral, or functionalized fullerenes. FNWs display n-type semiconducting behavior and are used in a diverse range of applications, including field-effect transistors, solar cells, chemical sensors, and photocatalysts. Alkali metal-doped C60 (fullerene) nanowhiskers (C60NWs) exhibit superconducting behavior. Potassium-doped C60NWs have realized the highest superconducting volume fraction of the alkali metal-doped C60 crystals and display a high critical current density (Jc) under a high magnetic field of 50 kOe. The growth control of FNWs is important for their success in practical applications. This paper reviews recent FNWs research focusing on their mechanical, electrical and superconducting properties and growth mechanisms in the liquid-liquid interfacial precipitation method.

  18. Development of density-functional theory for a plasmon-assisted superconducting state: application to lithium under high pressures.

    Science.gov (United States)

    Akashi, Ryosuke; Arita, Ryotaro

    2013-08-02

    We extend the density-functional theory for superconductors (SCDFT) to take account of the dynamical structure of the screened Coulomb interaction. We construct an exchange-correlation kernel in the SCDFT gap equation on the basis of the random-phase approximation, where electronic collective excitations such as plasmons are properly treated. Through an application to fcc lithium under high pressures, we demonstrate that our new kernel gives higher transition temperatures (T(c)) when the plasmon and phonon cooperatively mediate pairing and it improves the agreement between the calculated and experimentally observed T(c). The present formalism opens the door to nonempirical studies on unconventional electron mechanisms of superconductivity based on density-functional theory.

  19. Controlled creation of structural defects in the heavy fermion superconductor UPt{sub 3} and its influence on the superconducting properties

    Energy Technology Data Exchange (ETDEWEB)

    Suderow, H. [CEA, Grenoble (France). Dept. de Recherche Fondamentale sur la Mateiere Condensee]|[CNRS, Grenoble (France). Centre des Recherches sur les Tres Basses Temperatures]|[Univ. Autonoma de Madrid (Spain). Lab. de Bajas Temperaturas; Kambe, S.; Huxley, A.; Flouquet, J. [CEA, Grenoble (France). Dept. de Recherche Fondamentale sur la Mateiere Condensee; Brison, J.P. [CNRS, Grenoble (France). Centre des Recherches sur les Tres Basses Temperatures; Rullier-Albenque, F. [Ecole Polytechnique, Palaiseau (France). Lab. des Solides Irradies

    1999-09-01

    The superconducting properties of the heavy fermion UPt{sub 3} have been changed by irradiation with high energy electrons which creates point defects in a reproducible and controlled way. Measurements of the residual resistivity, critical temperature, upper critical field and thermal conductivity have been realized on these irradiated samples. The strong suppression of superconductivity with increasing defect concentration is in agreement with the theory of unconventional superconductivity. However, the thermal conductivity data contradicts the simple predictions derived from the most popular models (E{sub 1g} and E{sub 2u}) of the superconducting order parameter in UPt{sub 3}.

  20. Large-scale modulation in the superconducting properties of thin films due to domains in the SrTi O3 substrate

    Science.gov (United States)

    Wissberg, Shai; Kalisky, Beena

    2017-04-01

    Scanning superconducting quantum interference device measurements reveal large-scale modulations of the superfluid density and the critical temperature in superconducting Nb, NbN, and underdoped YB a2C u3O7 -δ films deposited on SrTi O3 (STO). We show that these modulations are a result of the STO domains and domain walls, forming below the 105 K structural phase transition of STO. We found that the flow of normal current, measured above the superconducting transition, is also modulated over the same domain structure, suggesting a modified carrier density. In clean STO, domain walls remain mobile down to low temperatures. Modulated superconductivity over mobile channels offers the opportunity to locally control superconducting properties and better understand the relations between superconductivity and the local structure.

  1. A BEAMLINE FOR HIGH PRESSURE STUDIES AT THE ADVANCED LIGHT SOURCE WITH A SUPERCONDUCTING BENDING MAGNET AS THE SOURCE

    Energy Technology Data Exchange (ETDEWEB)

    Kunz, M; MacDowell, A A; Caldwell, W A; Cambie, D; Celestre, R S; Domning, E E; Duarte, R M; Gleason, A; Glossinger, J; Kelez, N; Plate, D W; Yu, T; Zaug, J M; Padmore, H A; Jeanloz, R; Alivisatos, A P; Clark, S M

    2005-04-19

    A new facility for high-pressure diffraction and spectroscopy using diamond anvil high-pressure cells has been built at the Advanced Light Source on Beamline 12.2.2. This beamline benefits from the hard X-radiation generated by a 6 Tesla superconducting bending magnet (superbend). Useful x-ray flux is available between 5 keV and 35 keV. The radiation is transferred from the superbend to the experimental enclosure by the brightness preserving optics of the beamline. These optics are comprised of: a plane parabola collimating mirror (M1), followed by a Kohzu monochromator vessel with a Si(111) crystals (E/{Delta}E {approx} 7000) and a W/B{sub 4}C multilayer (E/{Delta}E {approx} 100), and then a toroidal focusing mirror (M2) with variable focusing distance. The experimental enclosure contains an automated beam positioning system, a set of slits, ion chambers, the sample positioning goniometry and area detectors (CCD or image-plate detector). Future developments aim at the installation of a second end station dedicated for in situ laser-heating on one hand and a dedicated high-pressure single-crystal station, applying both monochromatic as well as polychromatic techniques.

  2. A Beamline for High-Pressure Studies at the Advanced Light Sourcewith a Superconducting Bending Magnet as the Source

    Energy Technology Data Exchange (ETDEWEB)

    Kunz, Martin; MacDowell, Alastair A.; Caldwell, Wendel A.; Cambie, Daniella; Celestre, Richard S.; Domning, Edward E.; Duarte,Robert M.; Gleason, Arianna E.; Glossinger, James M.; Kelez, Nicholas; Plate, David W.; Yu, Tony; Zaug, Joeseph M.; Padmore, Howard A.; Jeanloz,Raymond; Alivisatos, A. Paul; Clark, Simon M.

    2005-06-30

    A new facility for high-pressure diffraction and spectroscopy using diamond anvil high-pressure cells has been built at the Advanced Light Source on Beamline 12.2.2. This beamline benefits from the hard X-radiation generated by a 6 Tesla superconducting bending magnet (superbend). Useful x-ray flux is available between 5 keV and 35 keV. The radiation is transferred from the superbend to the experimental enclosure by the brightness preserving optics of the beamline. These optics are comprised of: a plane parabola collimating mirror (M1), followed by a Kohzu monochromator vessel with a Si(111) crystals (E/DE {approx}7000) and a W/B4C multilayers (E/DE {approx} 100), and then a toroidal focusing mirror (M2) with variable focusing distance. The experimental enclosure contains an automated beam positioning system, a set of slits, ion chambers, the sample positioning goniometry and area detectors (CCD or image-plate detector). Future developments aim at the installation of a second end station dedicated for in situ laser-heating on one hand and a dedicated high-pressure single-crystal station, applying both monochromatic as well as polychromatic techniques.

  3. Theoretical study of the ground-state structures and properties of niobium hydrides under pressure

    Science.gov (United States)

    Gao, Guoying; Hoffmann, Roald; Ashcroft, N. W.; Liu, Hanyu; Bergara, Aitor; Ma, Yanming

    2013-11-01

    As part of a search for enhanced superconductivity, we explore theoretically the ground-state structures and properties of some hydrides of niobium over a range of pressures and particularly those with significant hydrogen content. A primary motivation originates with the observation that under normal conditions niobium is the element with the highest superconducting transition temperature (Tc), and moreover some of its compounds are metals again with very high Tc's. Accordingly, combinations of niobium with hydrogen, with its high dynamic energy scale, are also of considerable interest. This is reinforced further by the suggestion that close to its insulator-metal transition, hydrogen may be induced to enter the metallic state somewhat prematurely by the addition of a relatively small concentration of a suitable transition metal. Here, the methods used correctly reproduce some ground-state structures of niobium hydrides at even higher concentrations of niobium. Interestingly, the particular stoichiometries represented by NbH4 and NbH6 are stabilized at fairly low pressures when proton zero-point energies are included. While no paired H2 units are found in any of the hydrides we have studied up to 400 GPa, we do find complex and interesting networks of hydrogens around the niobiums in high-pressure NbH6. The Nb-Nb separations in NbHn are consistently larger than those found in Nb metal at the respective pressures. The structures found in the ground states of the high hydrides, many of them metallic, suggest that the coordination number of hydrogens around each niobium atom grows approximately as 4n in NbHn (n = 1-4), and is as high as 20 in NbH6. NbH4 is found to be a plausible candidate to become a superconductor at high pressure, with an estimated Tc ˜ 38 K at 300 GPa.

  4. Statistical correlations for thermophysical properties of Supercritical Argon (SCAR) used in cooling of futuristic High Temperature Superconducting (HTS) cables

    Energy Technology Data Exchange (ETDEWEB)

    Kalsia, Mohit [School of Mechanical Engineering, Lovely Professional University, Phagwara, 144 401 (India); Dondapati, Raja Sekhar, E-mail: drsekhar@ieee.org [School of Mechanical Engineering, Lovely Professional University, Phagwara, 144 401 (India); Usurumarti, Preeti Rao [Department of Mechanical Engineering, PVK Institute of Technology, Anantpur, 515 001 (India)

    2017-05-15

    Highlights: • The developed correlations can be integrated into thermohydraulic analysis of HTS cables. • This work also explains the phenomenon of flow with less pumping power and maximum heat transfer in HTS cables. • Pumping power required to circulate the SCAR for cooling of HTS cables would be significantly lower. • For Hg-based high temperature superconductors (T{sub c} > 134 K), SCAR found to be a suitable coolant. - Abstract: High Temperature Superconducting (HTS) cables are emerging as an alternative to conventional cables in efficient power transmission. However, these HTS cables require cooling below the critical temperature of superconductors used to transmit larger currents. With the invention of high temperature superconductors whose critical temperatures are up to 134 K (Hg based), it is a great challenge to identify a suitable coolant which can carry away the heating load on the superconductors. In order to accomplish such challenge, an attempt has been made in the present work to propose supercritical Argon (SCAR) as the alternative to cool the HTS cables. Further, a statistical correlation has been developed for the thermophysical properties such as density, viscosity, specific heat and thermal conductivity of SCAR. In addition, the accuracy of developed correlations is established with the help of few statistical parameters and validated with standard database available in the literature. These temperature dependent accurate correlations are useful in predicting the pressure drop and heat transfer behaviour in HTS cables using numerical or computational techniques. In recent times, with the sophistication of computer technology, solving of various complex transport equations along with the turbulence models became popular and hence the developed correlations would benefit the technological community. It is observed that, a decrease in pressure, density and viscosity are found to be decreasing whereas the thermal conductivity and specific

  5. Superconducting properties of the s ±-wave state: Fe-based superconductors

    Science.gov (United States)

    Bang, Yunkyu; Stewart, G. R.

    2017-03-01

    Although the pairing mechanism of Fe-based superconductors (FeSCs) has not yet been settled with consensus with regard to the pairing symmetry and the superconducting (SC) gap function, the vast majority of experiments support the existence of spin-singlet sign-changing s-wave SC gaps on multi-bands ({{s}+/- } -wave state). This multi-band {{s}+/- } -wave state is a very unique gap state per se and displays numerous unexpected novel SC properties, such as a strong reduction of the coherence peak, non-trivial impurity effects, nodal-gap-like nuclear magnetic resonance signals, various Volovik effects in the specific heat (SH) and thermal conductivity, and anomalous scaling behaviors with a SH jump and condensation energy versus T c, etc. In particular, many of these non-trivial SC properties can easily be mistaken as evidence for a nodal-gap state such as a d-wave gap. In this review, we provide detailed explanations of the theoretical principles for the various non-trivial SC properties of the {{s}+/- } -wave pairing state, and then critically compare the theoretical predictions with experiments on FeSCs. This will provide a pedagogical overview of to what extent we can coherently understand the wide range of different experiments on FeSCs within the {{s}+/- } -wave gap model.

  6. Structural and superconducting properties of ion beam sputtered Nb thin films and Nb/Cu bilayers

    Science.gov (United States)

    Nath, S. K.; Dhawan, R.; Rai, S.; Lodha, G. S.; Sokhey, K. J. S.

    2012-01-01

    We present the results of a study of structural and superconducting properties of polycrystalline Nb thin films (200 Å, 300 Å, 400 Å, 700 Å and 1000 Å) and Nb/Cu bilayers (300 Å/300 Å and 400 Å/300 Å) prepared on Si substrates by ion beam sputtering at room temperature. The thicknesses, roughnesses at the surfaces and interfaces were determined by X-ray reflectivity whereas the grain sizes were determined from grazing incidence X-ray diffraction and transmission electron microscopic studies. The superconducting transition temperature ( T C) of Nb thin films are smaller than T C of bulk Nb. The Nb-200 Å sample does not show T C down to 2.3 K. The average size of the grains varies from 42 Å for Nb-200 Å sample to 69 Å for Nb-1000 Å sample. Our results show that the T C in these polycrystalline films is not only limited by its thickness but also by the size of the grains. The Nb films deposited in situ on the Cu layer (Nb/Cu) show a marginal increase in average sizes of the grains as compare to their respective values in Nb films of same thicknesses. As a result a marginal increase in T C of these films is also observed. The maximum decrease in T C due to oxygen intake during deposition should be about 0.5 K from its bulk value (9.28 K). We have attributed the large decrease in T C in our case on the basis of decrease in the Debye temperature and density of states at the Fermi level for Nb thin films as compared to their respective values for bulk Nb.

  7. Improvement of superconducting properties of (Bi, Pb)-2223phase by TlF{sub 3} doping

    Energy Technology Data Exchange (ETDEWEB)

    Saoudel, A., E-mail: dca.saoudel@yahoo.fr [LEND, Faculty of Science and Technology, Med Seddik Benyahia University, 18000 Jijel (Algeria); Amira, A.; Mahamdioua, N.; Boudjadja, Y. [LEND, Faculty of Science and Technology, Med Seddik Benyahia University, 18000 Jijel (Algeria); Varilci, A.; Altintas, S.P.; Terzioglu, C. [Department of Physics, Faculty of Arts and Sciences, Abant Izzet Baysal University, 14280 Bolu (Turkey)

    2016-11-15

    In this work, the superconducting properties of thallium fluoride (TlF{sub 3})doped Bi{sub 1.8−x}Tl{sub x}Pb{sub 0.35}Sr{sub 2}Ca{sub 2Cu3}O{sub y}F{sub 3x}(x=0–0.15)compounds are presented. The X-ray diffraction analysis shows that the proportion of (Bi, Pb)-2223phase is higher than the secondary (Bi, Pb)-2212one in all samples and its highest value is about 82.74%for x=0.05. From the resistivity curves, the highest values of the onset critical transition temperature (T{sub c.on}), the offset critical transition temperature (T{sub c.off}) are seen for x=0.10. The calculation of activation energy (U{sub 0}) in the TAFF (thermally activation flux flow) region proves the positive effect of TlF{sub 3} doping on the dissipative behavior of energy near T{sub c.off}. Flux pinning strength is enhanced by increasing TlF{sub 3}content up to x=0.10, and decreased by the application of a magnetic field. The other superconducting parameters like T(H{sub c2}), T(H{sub irr}), ξ(0) and μ{sub 0}H{sub c2}(0) are also improved significantly by doping. The obtained results of Ac susceptibility measurements show that the onset temperature of diamagnetism is improved by TlF{sub 3} doping, in accordance with the resistivity results.

  8. Compressibility anomaly in the superconducting material Nb{sub 3}Al under high pressure

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Z.H., E-mail: zhenhaiuy@gmail.com [Department of Physics, Harbin Institute of Technology, Harbin 150080 (China); XSD, Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439 (United States); Li, C.Y. [Department of Physics, Harbin Institute of Technology, Harbin 150080 (China); Photon Sciences Directorate, Brookhaven National Laboratory, Upton, NY 11973 (United States); Liu, H.Z. [Natural Science Research Center, Harbin Institute of Technology, Harbin 150080 (China)

    2012-09-01

    Nb{sub 3}Al, which is widely used in high field magnets, was studied under a range of pressures up to 39.5 GPa using diamond anvil cell. The Nb{sub 3}Al superconductor is structurally stable up to the highest pressure of the present investigation from previous reports. However, an anomaly of the compressibility beyond 19.2 GPa was detected in the pressure versus volume plot. The curve of volume versus pressure shows the existence of a plateau around 18.0 GPa as seen in several other highly correlated electrons systems, The observed pressure-induced isostructural phase transition was accomplished with a volume inclination without any symmetrical change (space group, Wyckoff position). The physical mechanism behind this isostructural phase transition is the interesting issue for further studies.

  9. Local structure, stripe pinning, and superconductivity in La1.875Ba0.125CuO4 at high pressure

    Science.gov (United States)

    Fabbris, G.; Hücker, M.; Gu, G. D.; Tranquada, J. M.; Haskel, D.

    2013-08-01

    The interplay between stripe correlations, local structure, and superconductivity in La1.875Ba0.125CuO4 is studied with concomitant polarized x-ray absorption fine structure (XAFS) and x-ray diffraction measurements at high pressure. Long-range order of the CuO6 octahedral tilt pattern that pins charge-stripe order vanishes at a pressure-induced structural transition (P=1.8 GPa at T=5 K). Diffraction shows that static charge stripe and associated octahedral tilt correlations which survive in the high-pressure phase are effectively suppressed above 3.5 GPa. In contrast, XAFS analysis shows that instantaneous local correlations of the characteristic octahedral tilt pattern remain robust to at least 5 GPa. The decreasing local tilt angle is well correlated with a gradual increase in the superconducting transition temperature, suggesting that orientational pinning of charge correlations can survive the loss of static stripe order.

  10. Effects of post-annealing and cobalt co-doping on superconducting properties of (Ca,Pr)Fe2As2 single crystals

    Science.gov (United States)

    Okada, T.; Ogino, H.; Yakita, H.; Yamamoto, A.; Kishio, K.; Shimoyama, J.

    2014-10-01

    In order to clarify the origin of anomalous superconductivity in (Ca,RE)Fe2As2 system, Pr doped and Pr,Co co-doped CaFe2As2 single crystals were grown by the FeAs flux method. These samples showed two-step superconducting transition with Tc1 = 25-42 K, and Tc2 < 16 K, suggesting that (Ca,RE)Fe2As2 system has two superconducting components. Post-annealing performed for these crystals in evacuated quartz ampoules at various temperatures revealed that post-annealing at ∼400 °C increased the c-axis length for all samples. This indicates that as-grown crystals have a certain level of strain, which is released by post-annealing at ∼400 °C. Superconducting properties also changed dramatically by post-annealing. After annealing at 400 °C, some of the co-doped samples showed large superconducting volume fraction corresponding to the perfect diamagnetism below Tc2 and high Jc values of 104-105 A cm-2 at 2 K in low field, indicating the bulk superconductivity of (Ca,RE)Fe2As2 phase occurred below Tc2. On the contrary, the superconducting volume fraction above Tc2 was always very small, suggesting that 40 K-class superconductivity observed in this system is originating in the local superconductivity in the crystal.

  11. The role of various boron precursor on superconducting properties of MgB2/Fe

    Science.gov (United States)

    Safran, S.; Kılıçarslan, E.; Kılıç, A.; Gencer, A.

    2014-09-01

    The superconducting properties of Fe sheathed MgB2 wire has been studied as a function of precursor B powder particle size. The in situ processed MgB2 samples were prepared by means of conventional solid state reaction method with magnesium powder (99.8%, 325 mesh) and three different types of amorphous boron powders (purity; 98.8%, >95% and 91.9%) from two sources, Pavezyum (Turkish supplier) and Sigma Aldrich. The particle sizes of Turkish boron precursor powder were selected between 300 and 800 nm. The structural and magnetic properties of the prepared samples were investigated by means of the X-ray powder diffraction (XRD) and ac susceptibility measurements. The XRD patterns showed that the diffraction peaks for our samples belong to the main phase of the MgB2 diffraction patterns. The highest critical temperature, Tc = 38.4 K was measured for the MgB2 sample which was fabricated by using the 98.8% B. The critical current density of this sample was extracted from the magnetization measurements and Jc = 5.4 × 105 A cm-2 at 5 K and B = 2 T. We found that the sample made by using the 98.8% boron showed almost 2 times higher Jc than that of obtained from 91.9% B powder.

  12. Electronic properties and superconductivity of rapidly quenched Al-Si alloys

    Energy Technology Data Exchange (ETDEWEB)

    Chevrier, J.; Pavuna, D.; Cyrot-Lackmann, F.

    1987-12-15

    We present detailed studies of electronic properties of Al-Si alloys prepared in a nonequilibrium state by means of rapid solidification. The quenched alloys exhibit an enhanced superconducting transition temperature up to 6.2 K in an Al--Si 30 at. % alloy as well as an increased thermal slope of resistivity. Using differential scanning calorimetry, a large enthalpy variation (..delta..H = 4.1 kJ/mole for Al--Si 30 at. %) has been measured during the irreversible transition from the non- equilibrium state to the equilibrium one. This is mainly attributed to the energy difference between the metallic state of silicon atoms trapped in fcc aluminum matrix during quenching and the usual covalent state of silicon precipitates in an equilibrium state. This large energy difference is presented as the origin of a lattice instability which softens the phonon spectrum and gives rise to a stronger electron-phonon coupling. This appears to be a characteristic property of nonequilibrium Al-Si solid solutions, which is associated with the metallic state of silicon atoms. An interpretation of the T/sub c/ enhancement is proposed for both Al-Si and Al-Ge alloys based on the phonon softening in these nonequilibrium crystalline alloys.

  13. Anharmonic enhancement of superconductivity in metallic molecular Cmca  -  4 hydrogen at high pressure: a first-principles study.

    Science.gov (United States)

    Borinaga, Miguel; Riego, P; Leonardo, A; Calandra, Matteo; Mauri, Francesco; Bergara, Aitor; Errea, Ion

    2016-12-14

    First-principles calculations based on density-functional theory including anharmonicity within the variational stochastic self-consistent harmonic approximation are applied to understand how the quantum character of the proton affects the candidate metallic molecular Cmca  -  4 structure of hydrogen in the 400-450 GPa pressure range, where metallization of hydrogen is expected to occur. Anharmonic effects, which become crucial due to the zero-point motion, have a large impact on the hydrogen molecules by increasing the intramolecular distance by approximately a 6%. This induces two new electron pockets at the Fermi surface opening new scattering channels for the electron-phonon interaction. Consequently, the electron-phonon coupling constant and the superconducting critical temperature are approximately doubled by anharmonicity and Cmca  -  4 hydrogen becomes a superconductor above 200 K in all the studied pressure range. Contrary to many superconducting hydrides, where anharmoncity tends to lower the superconducting critical temperature, our results show that it can enhance superconductivity in molecular hydrogen.

  14. Superconductivity in layered binary silicides: A density functional theory study

    Science.gov (United States)

    Flores-Livas, José A.; Debord, Régis; Botti, Silvana; San Miguel, Alfonso; Pailhès, Stéphane; Marques, Miguel A. L.

    2011-11-01

    A class of metal disilicides (of the form XSi2, where X is a divalent metal) crystallizes in the EuGe2 structure, formed by hexagonal corrugated silicon planes intercalated with metal atoms. These compounds are superconducting like other layered superconductors, such as MgB2. Moreover, their properties can be easily tuned either by external pressure or by negative chemical pressure (i.e., by changing the metal), which makes disilicides an ideal testbed to study superconductivity in layered systems. In view of this, we present an extensive density functional theory study of the electronic and phonon band structures as well as the electron-phonon interaction of metal disilicides. Our results explain the variation of the superconducting transition temperature with pressure and the species of the intercalating atom, and allow us to predict superconductivity for compounds not yet synthesized belonging to this family.

  15. Simultaneous measurement of pressure evolution of crystal structure and superconductivity in FeSe[subscript 0.92] using designer diamonds

    Energy Technology Data Exchange (ETDEWEB)

    Uhoya, Walter; Tsoi, Georgiy; Vohra, Yogesh; Wolanyk, Nathaniel; Rao, Sistla Muralidhara; Wu, Maw-Kuen; Weir, Samuel (LLNL); (UAB); (IP-Taiwan); (IWU)

    2017-04-19

    Simultaneous high-pressure X-ray diffraction and electrical resistance measurements have been carried out on a PbO-type {alpha}-FeSe{sub 0.92} compound to a pressure of 44 GPa and temperatures down to 4 K using designer diamond anvils at synchrotron source. A ambient temperature, a structural phase transition from a tetragonal (P4/nmm) phase to an orthorhombic (Pbnm) phase is observed at 11 GPa and the Pbnm phase persists up to 74 GPa. The superconducting transition temperature (T{sub c}) increases rapidly with pressure reaching a maximum of {approx}28 K at {approx}6 GPa and decreases at higher pressures, disappearing completely at 14.6 GPa. Simultaneous pressure-dependent X-ray diffraction and resistance measurements at low temperatures show superconductivity only in a low-pressure orthorhombic (Cmma) phase of the {alpha}-FeSe{sub 0.92}. Upon increasing pressure at 10 K near T{sub c}, crystalline phases change from a mixture of orthorhombic (Cmma) and hexagonal (P63/mmc) phases to a high-pressure orthorhombic (Pbnm) phase near 6.4 GPa where T{sub c} is maximum.

  16. Superconductivity in transition metals.

    Science.gov (United States)

    Slocombe, Daniel R; Kuznetsov, Vladimir L; Grochala, Wojciech; Williams, Robert J P; Edwards, Peter P

    2015-03-13

    A qualitative account of the occurrence and magnitude of superconductivity in the transition metals is presented, with a primary emphasis on elements of the first row. Correlations of the important parameters of the Bardeen-Cooper-Schrieffer theory of superconductivity are highlighted with respect to the number of d-shell electrons per atom of the transition elements. The relation between the systematics of superconductivity in the transition metals and the periodic table high-lights the importance of short-range or chemical bonding on the remarkable natural phenomenon of superconductivity in the chemical elements. A relationship between superconductivity and lattice instability appears naturally as a balance and competition between localized covalent bonding and so-called broken covalency, which favours d-electron delocalization and superconductivity. In this manner, the systematics of superconductivity and various other physical properties of the transition elements are related and unified.

  17. Electronic and magnetic phase diagram of beta-Fe(1.01)Se with superconductivity at 36.7 K under pressure.

    Science.gov (United States)

    Medvedev, S; McQueen, T M; Troyan, I A; Palasyuk, T; Eremets, M I; Cava, R J; Naghavi, S; Casper, F; Ksenofontov, V; Wortmann, G; Felser, C

    2009-08-01

    The discovery of new high-temperature superconductors based on FeAs has led to a new 'gold rush' in high-T(C) superconductivity. All of the new superconductors share the same common structural motif of FeAs layers and reach T(C) values up to 55 K (ref. 2). Recently, superconductivity has been reported in FeSe (ref. 3), which has the same iron pnictide layer structure, but without separating layers. Here, we report the magnetic and electronic phase diagram of beta-Fe(1.01)Se as a function of temperature and pressure. The superconducting transition temperature increases from 8.5 to 36.7 K under an applied pressure of 8.9 GPa. It then decreases at higher pressures. A marked change in volume is observed at the same time as T(C) rises, owing to a collapse of the separation between the Fe(2)Se(2) layers. No static magnetic ordering is observed for the whole p-T phase diagram. We also report that at higher pressures (starting around 7 GPa and completed at 38 GPa), Fe(1.01)Se transforms to a hexagonal NiAs-type structure and exhibits non-magnetic behaviour.

  18. Distinct superconducting states in the pressure-induced metallic structures of the nominal semimetal Bi[subscript 4]Te[subscript 3

    Energy Technology Data Exchange (ETDEWEB)

    Jeffries, J.R.; Sharma, A.L. Lima; Sharma, P.A.; Spataru, C.D.; McCall, S.K.; Sugar, J.D.; Weir, S.T.; Vohra, Y.K. (Sandia); (LLNL); (UAB)

    2011-11-07

    The end members, Bi and Bi{sub 2}Te{sub 3}, of the infinitely adaptive (Bi{sub 2})m(Bi{sub 2}Te{sub 3}){sub n} series of compounds have not only been revealed to be topological insulators under the appropriate conditions, but have also been shown to be superconductors under pressure, suggesting the potential for bulk superconductor-topological-insulator interfaces and associated quantum computing applications. Herein, we report the pressure-dependent evolution of the structure and electrical transport of the nominal semimetal Bi4Te{sub 3}, a member of the (Bi{sub 2})m(Bi{sub 2}Te{sub 3}){sub n} series. Under pressure, Bi4Te{sub 3} undergoes several structural phase transformations, ultimately yielding a metallic body-centered-cubic structure exhibiting superconductivity with a maximum T{sub c} = 8.4 K at 16.2 GPa. The occurrence of structure-dependent superconductivity in Bi{sub 4}Te{sub 3} is remarkably similar to the end members of the (Bi{sub 2})m(Bi{sub 2}Te{sub 3}){sub n} series, intimating a convergence to high-pressure universal behavior that may expose the subtle variations that lead to the topological insulating and superconducting states in these systems.

  19. Electronic and magnetic phase diagram of [Beta]Fe[subscript1.01]Se with superconductivity at 36.7 K under pressure

    Energy Technology Data Exchange (ETDEWEB)

    Medvedev, S.; McQueen, T.M.; Troyan, I.A.; Palasyuk, T.; Eremets, M.I.; Cava, R.J.; Naghavi, S.; Casper, F.; Ksenofontov, V.; Wortmann, G.; Felser, C.; (Paderborn); (MXPL-M); (Mainz); (Princeton)

    2010-09-17

    The discovery of new high-temperature superconductors based on FeAs has led to a new 'gold rush' in high-T{sub C} superconductivity. All of the new superconductors share the same common structural motif of FeAs layers and reach T{sub C} values up to 55 K. Recently, superconductivity has been reported in FeSe, which has the same iron pnictide layer structure, but without separating layers. Here, we report the magnetic and electronic phase diagram of {beta}-Fe{sub 1.01}Se as a function of temperature and pressure. The superconducting transition temperature increases from 8.5 to 36.7 K under an applied pressure of 8.9 GPa. It then decreases at higher pressures. A marked change in volume is observed at the same time as T{sub C} rises, owing to a collapse of the separation between the Fe{sub 2}Se{sub 2} layers. No static magnetic ordering is observed for the whole p-T phase diagram. We also report that at higher pressures (starting around 7 GPa and completed at 38 GPa), Fe{sub 1.01}Se transforms to a hexagonal NiAs-type structure and exhibits non-magnetic behavior.

  20. Electronic and magnetic phase diagram of β-Fe1.01Se with superconductivity at 36.7K under pressure

    Science.gov (United States)

    Medvedev, S.; McQueen, T. M.; Troyan, I. A.; Palasyuk, T.; Eremets, M. I.; Cava, R. J.; Naghavi, S.; Casper, F.; Ksenofontov, V.; Wortmann, G.; Felser, C.

    2009-08-01

    The discovery of new high-temperature superconductors based on FeAs has led to a new `gold rush' in high-TC superconductivity. All of the new superconductors share the same common structural motif of FeAs layers and reach TC values up to 55K (ref. 2). Recently, superconductivity has been reported in FeSe (ref. 3), which has the same iron pnictide layer structure, but without separating layers. Here, we report the magnetic and electronic phase diagram of β-Fe1.01Se as a function of temperature and pressure. The superconducting transition temperature increases from 8.5 to 36.7K under an applied pressure of 8.9GPa. It then decreases at higher pressures. A marked change in volume is observed at the same time as TC rises, owing to a collapse of the separation between the Fe2Se2 layers. No static magnetic ordering is observed for the whole p-T phase diagram. We also report that at higher pressures (starting around 7GPa and completed at 38GPa), Fe1.01Se transforms to a hexagonal NiAs-type structure and exhibits non-magnetic behaviour.

  1. Elastic properties of solids at high pressure

    Science.gov (United States)

    Vekilov, Yu Kh; Krasilnikov, O. M.; Lugovskoy, A. V.

    2015-11-01

    This review examines the elastic response of solids under load. The definitions of isothermal and adiabatic elastic constants of ( n≥2) for a loaded crystal are given. For the case of hydrostatic pressure, two techniques are proposed for calculating the second-, third-, and fourth-order elastic constants from the energy-strain and stress-strain relations. As an example, using the proposed approach within the framework of the density functional theory, the second- to fourth-order elastic constants of bcc tungsten are calculated for the pressure range of 0-600 GPa.

  2. Effect of rapid heating, quenching and transformation conditions on the superconducting properties and microstructure of Jelly-Roll processed Nb3Al superconductors

    Science.gov (United States)

    Fukuzaki, T.; Takeuchi, T.; Banno, N.; Tagawa, K.; Tatsumi, N.; Ogiwara, H.; Wada, H.

    2002-10-01

    A Jelly-Roll processed Nb3Al superconductor with excellent superconducting properties has been fabricated by the process of rapid heating, quenching and transformation (RHQT). In order to fabricate a long length of wire with homogeneous superconducting properties, the optimization of the RHQT conditions is particularly important because RHQT conditions determine the final microstructure and superconducting properties. In this paper, we have studied the variation of microstructure and superconducting properties with RHQ and transformation annealing conditions, to determine the optimum processing condition. In the study of the RHQ treatment, we found that the RHQ conditions are divided into four regions according to the joule heating current (IRHQ). In the optimum region, the wire is quenched from the temperature in which a bcc solid solution extends to more than 25 at%Al, and the scatter of critical current density (Jc) after transformation annealing is almost negligible. In the study of the deformation and transformation heat treatment, we have found that the deformation of the supersaturated solid solution improves the resultant superconducting properties, and prevents degradation of superconducting properties that occurs when the temperature ramp-up rate is slow.

  3. Effect of the BSCCO superconducting properties by tiny Y2O3 addition

    Science.gov (United States)

    Dong, Yan; Sun, Aimin; Xu, Bin; Zhang, Hongtao; Zhang, Meng

    2016-09-01

    In this paper, the effect of tiny Y2O3 addition in (Bi,Pb)-2223 superconductor prepared by solid state reaction technique was studied. The properties of samples have been investigated via X-ray diffraction (XRD), resistance-temperature (R-T) curve, scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). XRD data indicated that all samples are multiphase and the major phases are high-temperature phases and low-temperature phases. The volume fraction of (Bi,Pb)-2223 is not great change with tiny Y2O3 addition. All samples exhibit superconducting phase with the critical transition temperature and one-step transition, however, the transition width was decreased with the Y2O3 addition up to 0.04 wt.% and sharp increased with the excessive oxide addition. SEM pictures show that the Y2O3 appeared on the flake-type grains surface obviously, but the number and size of the hole between grains are decreased in the 0.04 wt.% addition.

  4. EPW: Electron-phonon coupling, transport and superconducting properties using maximally localized Wannier functions

    Science.gov (United States)

    Poncé, S.; Margine, E. R.; Verdi, C.; Giustino, F.

    2016-12-01

    The EPW (Electron-Phonon coupling using Wannier functions) software is a Fortran90 code that uses density-functional perturbation theory and maximally localized Wannier functions for computing electron-phonon couplings and related properties in solids accurately and efficiently. The EPW v4 program can be used to compute electron and phonon self-energies, linewidths, electron-phonon scattering rates, electron-phonon coupling strengths, transport spectral functions, electronic velocities, resistivity, anisotropic superconducting gaps and spectral functions within the Migdal-Eliashberg theory. The code now supports spin-orbit coupling, time-reversal symmetry in non-centrosymmetric crystals, polar materials, and k and q-point parallelization. Considerable effort was dedicated to optimization and parallelization, achieving almost a ten times speedup with respect to previous releases. A computer test farm was implemented to ensure stability and portability of the code on the most popular compilers and architectures. Since April 2016, version 4 of the EPW code is fully integrated in and distributed with the Quantum ESPRESSO package, and can be downloaded through QE-forge at http://qe-forge.org/gf/project/q-e.

  5. International round robin test for mechanical properties of REBCO superconductive tapes at room temperature

    Science.gov (United States)

    Osamura, K.; Shin, H.-S.; Weiss, K.-P.; Nyilas, A.; Nijhuis, A.; Yamamoto, K.; Machiya, S.; Nishijima, G.

    2014-08-01

    An international round robin test was promoted to establish a test method for room temperature mechanical properties of commercial REBCO superconductive tapes. Seven laboratories practiced a tensile test under the direction of guideline REBCO13 for four different kinds of REBCO tape. From the stress versus strain curve, the modulus of elasticity and the 0.2% proof strength were measured. The scatter of measured values was analyzed by evaluating the RSU (relative standard uncertainty). To judge the major contribution to scattering, an F test was applied. The major source of RSUs was estimated to be the influence of inter-laboratory scattering. In order to reduce the overall scattering, it is suggested that the REBCO13 guideline should be modified with respect to the following three experimental factors. The window determining acceptable data should be narrowed, and the initial strain rate should be suppressed to less than 1 × 10-4 (s-1). Repeated thickness measurement is recommended to reduce the standard uncertainty.

  6. Weak antiferromagnetic order and superconductivity in UPt 3 studied by neutron scattering

    Science.gov (United States)

    van Dijk, N. H.; Rodière, P.; Fåk, B.; Huxley, A.; Flouquet, J.

    2002-07-01

    The heavy-fermion superconductor UPt 3 is one of the best-studied examples of systems that show unconventional superconductivity. Below a transition temperature of Tc=0.55 K a complex phase diagram with three different superconducting phases is observed as a function of temperature, magnetic field, and pressure. The weak antiferromagnetic order ( TN=6 K) with an ordered moment of only 0.02 μB/U atom is believed to play a crucial role in the existence of multiple superconducting phases, as it can act as a symmetry-breaking field for the vector order parameter of the unconventional superconductivity. We review recent progress in neutron scattering measurements on the weak antiferromagnetic order as a function of magnetic field, pressure, and Pd doping and on the superconducting flux-line lattice. The relation between the magnetic and superconducting properties is discussed.

  7. Electronic and elastic properties of PbS under pressure

    Energy Technology Data Exchange (ETDEWEB)

    Li Wei, E-mail: towangteng@263.ne [Laboratory of Quantum Information Technology, School of Physics and Telecommunication Engineering, South China Normal University, 5100006, Guangzhou (China); Chen Junfang [Laboratory of Quantum Information Technology, School of Physics and Telecommunication Engineering, South China Normal University, 5100006, Guangzhou (China); Wang Teng [School of Computer, South China Normal University, 510631, Guangzhou (China)

    2010-03-01

    The electronic structures and elastic properties of lead sulfide are studied usingfirst-principles calculations. The energy band structure and density of state (DOS) of PbS at 0 GPa are calculated. The band gap energy of PbS versus the pressure 0-40 GPa is obtained. We find that the band gap energy decreases as the pressure increases. The geometry optimized structural parameters for PbS under different pressures are listed. The lattice parameter a, and enthalpy E both decrease with increasing pressure. However, parameter B, S and Y increase with pressure. The normalized lattice constants and the elastic modulus as two functions of pressure from 0-40 GPa are obtained. The calculated elastic constants C11 and C12 increase but with different rates under increasing pressure. However, C44 decrease under increasing pressure.

  8. High-pressure synthesis and superconductivity of the Laves phase compound Ca(Al,Si)2 composed of truncated tetrahedral cages Ca@(Al,Si))12.

    Science.gov (United States)

    Tanaka, Masashi; Zhang, Shuai; Inumaru, Kei; Yamanaka, Shoji

    2013-05-20

    The Zintl compound CaAl2Si2 peritectically decomposes to a new ternary cubic Laves phase Ca(Al,Si)2 and an Al-Si eutectic at temperatures above 750 °C under a pressure of 13 GPa. The ternary Laves phase compound can also be prepared as solid solutions Ca(Al(1-x)Si(x))2 (0.35 ≤ x ≤ 0.75) directly from the ternary mixtures under high-pressure and high-temperature conditions. The cubic Laves phase structure can be regarded as a type of clathrate compound composed of face-sharing truncated tetrahedral cages with Ca atoms at the center, Ca@(Al,Si)12. The compound with a stoichiometric composition CaAlSi exhibits superconductivity with a transition temperature of 2.6 K. This is the first superconducting Laves phase compound composed solely of commonly found elements.

  9. Quench Property of Twisted-Pair MgB$_2$ Superconducting Cables in Helium Gas

    CERN Document Server

    Spurrell, J; Falorio, I; Pelegrin, J; Ballarino, A; Yang, Y

    2015-01-01

    CERN's twisted-pair superconducting cable is a novel design which offers filament transposition, low cable inductance and is particularly suited for tape conductors such as 2G YBCO coated conductors, Ag-sheathed Bi2223 tapes and Ni/Monel-sheathed MgB2 tapes. A typical design of such twistedpair cables consists of multiple superconducting tapes intercalated with thin copper tapes as additional stabilizers. The copper tapes are typically not soldered to the superconducting tapes so that sufficient flexibility is retained for the twisting of the tape assembly. The electrical and thermal contacts between the copper and superconducting tapes are an important parameter for current sharing, cryogenic stability and quench propagation. Using an MgB2 twisted-pair cable assembly manufactured at CERN, we have carried out minimum quench energy (MQE) and propagation velocity (vp) measurements with point-like heat deposition localized within a tape. Furthermore, different contacts between the copper and superconductor aroun...

  10. Accelerator physics and radiometric properties of superconducting wavelength shifters; Beschleunigerphysik und radiometrische Eigenschaften supraleitender Wellenlaengenschieber

    Energy Technology Data Exchange (ETDEWEB)

    Scheer, Michael

    2008-11-17

    Subject of this thesis is the operation of wave-length shifters at electron storage rings and their use in radiometry. The basic aspects of the radiometry, the technical requirements, the influence of wave-length shifters on the storage ring, and results of first measurements are presented for a device installed at BESSY. Most of the calculations are carried out by the program WAVE, which has been developed within this thesis. WAVE allows to calculate the synchrotron radiation spectra of wavelength shifters within an relative uncertainty of 1/100000. The properties of wave-length shifters in terms of accelerator physics as well as a generating function for symplectic tracking calculations can also be calculated by WAVE. The later was implemented in the tracking code BETA to investigate the influence of insertion devices on the dynamic aperture and emittance of the storage ring. These studies led to the concept of alternating low- and high-beta-sections at BESSY-II, which allow to operate superconducting insertion devices without a significant distortion of the magnetic optics. To investigate the experimental aspects of the radiometry at wave-length shifters, a program based on the Monte-Carlo-code GEANT4 has been developed. It allows to simulate the radiometrical measurements and the absorption properties of detectors. With the developed codes first radiometrical measurements by the PTB have been analysed. A comparison of measurements and calculations show a reasonable agreement with deviations of about five percent in the spectral range of 40-60 keV behind a 1-mm-Cu filter. A better agreement was found between 20 keV and 80 keV without Cu filter. In this case the measured data agreed within a systematic uncertainty of two percent with the results of the calculations. (orig.)

  11. Microstructure and superconducting properties of MgB{sub 2} films prepared by solid state reaction of multilayer precursors of the elements

    Energy Technology Data Exchange (ETDEWEB)

    Kugler, B. [Max Planck Institute for Intelligent Systems, Heisenbergstr, 3, D-70569 Stuttgart (Germany); Aalen University, Beethovenstr, 1, D-73430 Aalen (Germany); Stahl, C.; Treiber, S. [Max Planck Institute for Intelligent Systems, Heisenbergstr, 3, D-70569 Stuttgart (Germany); Soltan, S. [Max Planck Institute for Solid State Research, Heisenbergstr, 1, D-70569 Stuttgart (Germany); Physics Department, Faculty of Science, Helwan University,11792-Cairo (Egypt); Haug, S.; Schuetz, G. [Max Planck Institute for Intelligent Systems, Heisenbergstr, 3, D-70569 Stuttgart (Germany); Albrecht, J., E-mail: ja@mf.mpg.de [Aalen University, Beethovenstr, 1, D-73430 Aalen (Germany)

    2012-09-30

    Surface morphology and superconducting properties of MgB{sub 2} superconducting thin films prepared by ex-situ annealing of multilayer Mg/B precursors in Mg vapor are studied. Depending on the precursor structure different physical and microstructural properties of the superconductor evolve. Structure and composition of the films are analyzed by scanning electron microscopy and wavelength dispersive x-ray spectroscopy. It is found that certain precursor structures can lead to high quality superconducting films, however, in specific precursor structures mechanical stress leads to the formation of wrinkles strongly affecting the superconducting homogeneity of the films. A correlation between microstructure and superconducting properties, such as pinning or critical current density, can be provided via magneto-optical Faraday microscopy. - Highlights: Black-Right-Pointing-Pointer Correlation of microstructure and properties of MgB2 films Black-Right-Pointing-Pointer Electron and ion based analysis of microstructure Black-Right-Pointing-Pointer Superconducting properties by magneto-optical imaging Black-Right-Pointing-Pointer Enhanced magnetic field stability by a particular microstructure.

  12. Pressing Speed, Specific Pressure and Mechanical Properties of Aluminium Cast

    Directory of Open Access Journals (Sweden)

    Gaspar S.

    2016-06-01

    Full Text Available Recent research in the process of aluminum alloy die castings production, which is nowadays deeply implemented into the rapidly growing automobile, shipping and aircraft industries, is aimed at increasing the useful qualitative properties of the die casting in order to obtain its high mechanical properties at acceptable economic cost. Problem of technological factors of high pressure die casting has been a subject of worldwide research (EU, US, Japan, etc.. The final performance properties of die castings are subjected to a large number of technological factors. The main technological factors of high pressure die casting are as follows: plunger pressing speed, specific (increase pressure, mold temperature as well as alloy temperature. The contribution discusses the impact of the plunger pressing speed and specific (increase pressure on the mechanical properties of the casting aluminum alloy.

  13. Dependence of Glass Mechanical Properties on Thermal and Pressure History

    DEFF Research Database (Denmark)

    Smedskjær, Morten Mattrup; Bauchy, Mathieu

    -equilibrium material, the structure and properties of glass depend not only on its composition, but also on its thermal and pressure histories. Here we review our recent findings regarding the thermal and pressure history dependence of indentation-derived mechanical properties of oxide glasses.......Predicting the properties of new glasses prior to manufacturing is a topic attracting great industrial and scientific interest. Mechanical properties are currently of particular interest given the increasing demand for stronger, thinner, and more flexible glasses in recent years. However, as a non...

  14. Phase formation of superconducting MgB2 at ambient pressure

    Indian Academy of Sciences (India)

    A Talapatra; S K Bandyopadhyay; Pintu Sen; A Sarkar; P Barat

    2004-10-01

    MgB2 superconductor has been synthesized using a simple technique at ambient pressure. The synthesis was carried out in helium atmosphere over a wide range of temperatures. Magnesium was employed in excess to the stoichiometry to prevent the decomposition of MgB2. Samples of MgB2 thus prepared have been almost free from MgO as compared to other methods. Resistivities of the samples are quite low with residual resistivity ratio (RRR) of around 3. c ( = 0) is 38.2–38.5 K with c of 0.6–1.0 K. Comparative studies of various methods of low pressure synthesis have been presented.

  15. Magnetotransport Properties in High-Quality Ultrathin Two-Dimensional Superconducting Mo2C Crystals.

    Science.gov (United States)

    Wang, Libin; Xu, Chuan; Liu, Zhibo; Chen, Long; Ma, Xiuliang; Cheng, Hui-Ming; Ren, Wencai; Kang, Ning

    2016-04-26

    Ultrathin transition metal carbides are a class of developing two-dimensional (2D) materials with superconductivity and show great potentials for electrical energy storage and other applications. Here, we report low-temperature magnetotransport measurements on high-quality ultrathin 2D superconducting α-Mo2C crystals synthesized by a chemical vapor deposition method. The magnetoresistance curves exhibit reproducible oscillations at low magnetic fields for temperature far below the superconducting transition temperature of the crystals. We interpret the oscillatory magnetoresistance as a consequence of screening currents circling around the boundary of triangle-shaped terraces found on the surface of ultrathin Mo2C crystals. As the sample thickness decreases, the Mo2C crystals exhibit negative magnetoresistance deep in the superconducting transition regime, which reveals strong phase fluctuations of the superconducting order parameters associated with the superconductor-insulator transition. Our results demonstrate that the ultrathin superconducting Mo2C crystals provide an interesting system for studying rich transport phenomena in a 2D crystalline superconductor with enhanced quantum fluctuations.

  16. Structural and superconducting properties of YBa2Cu3-xMxOy (M=Ag, Al

    Directory of Open Access Journals (Sweden)

    S Falahati

    2009-08-01

    Full Text Available   Samples of YBa2Cu3-xAgxOy with x=0, 0.1, 0.15, 0.2, 0.3 and samples of YBa2Cu3-xAlxOy with x=0, 0.01, 0.02, 0.03 and 0.045 are prepared by the sol-gel method. Structural and superconducting properties of samples are studied by electrical resistivity (R-T, X-ray diffraction (XRD and scanning electron microscopy (SEM. All the samples show transition to superconducting state and the transition temperatures of the samples increased with increasing Ag doping up to x=0.15. R-T measurements show a small decrease of TC (zero with increasing Al doping up to x=0.02, and followed by a faster decrease with increasing doping concentration. YBCO grains are better linked with increasing Ag doping. So, Ag has positive effects in superconducting properties of YBCO. The crystal structure of samples was refined by MAUD. These results show tha, Ag is substituted for Cu(1 in YBCO. According to these analysis, we introduce x=0.15 as the optimum value for doping concentration .

  17. Color superconductivity

    Energy Technology Data Exchange (ETDEWEB)

    Wilczek, F. [Institute for Advanced Study, Princeton, NJ (United States)

    1997-09-22

    The asymptotic freedom of QCD suggests that at high density - where one forms a Fermi surface at very high momenta - weak coupling methods apply. These methods suggest that chiral symmetry is restored and that an instability toward color triplet condensation (color superconductivity) sets in. Here I attempt, using variational methods, to estimate these effects more precisely. Highlights include demonstration of a negative pressure in the uniform density chiral broken phase for any non-zero condensation, which we take as evidence for the philosophy of the MIT bag model; and demonstration that the color gap is substantial - several tens of MeV - even at modest densities. Since the superconductivity is in a pseudoscalar channel, parity is spontaneously broken.

  18. Elimination of bubbles and improvement of the superconducting properties in MgB2 films annealed using electron beam

    Science.gov (United States)

    Xu, Zhuang; Kong, Xiangdong; Han, Li; Pang, Hua; Wu, Yue; Gao, Zhaoshun; Li, Xiaona

    2017-03-01

    MgB2 superconducting films can be readily obtained using the electron-beam annealing method. However, many bubbles existing in the film severely damage the surface morphology, which is known as the deleterious current-limiting mechanism. Based on morphology images and energy-dispersive spectroscopy spectra, we found that, during the annealing process, solid Mg-rich layers evaporate to form Mg vapour in the precursor film, resulting in bubbles in the film. By reducing the cycle thickness of the precursor film, we obtained MgB2 films with better properties. The root-mean-square surface roughness was 2.7 nm over a 10 × 10 μm area for a 100 nm-thick film, and the critical current density at 20 K was increased to 3.8 × 106 A cm‑2. These MgB2 films are suitable for fabricating MgB2 superconducting devices.

  19. High-Temperature Superconductivity

    Science.gov (United States)

    Tanaka, Shoji

    2006-12-01

    A general review on high-temperature superconductivity was made. After prehistoric view and the process of discovery were stated, the special features of high-temperature superconductors were explained from the materials side and the physical properties side. The present status on applications of high-temperature superconductors were explained on superconducting tapes, electric power cables, magnets for maglev trains, electric motors, superconducting quantum interference device (SQUID) and single flux quantum (SFQ) devices and circuits.

  20. Effect of pressurization on antibacterial properties of Lactobacillus strains

    Science.gov (United States)

    Jankowska, Agnieszka; Grześkiewicz, Aleksandra; Wiśniewska, Krystyna; Reps, Arnold

    2010-03-01

    The objective of the study was to determine the effect of high pressures on antibacterial properties of selected strains of the Lactobacillus species. Cultures of 22 strains were subjected to high-pressure treatment at 30, 60, 90, and 300 MPa/1 min/18 °C. The susceptibility of the bacteria pressurized at 30-90 MPa was diversified and depended on the strain and not on its species affiliation. When compared with pressures of 30-90 MPa, the pressure treatment at 300 MPa caused the inhibition of the acidifying activity of the strains analyzed. In turn, the pressures applied had no impact on the quantity of hydrogen peroxide synthesized. An increase in pressure was accompanied by a diminishing antibacterial activity of the investigated Lactobacillus strains.

  1. The Preparation and Properties of Niobium Superconducting Structures Prepared by Electron Beam Evaporation in Uhv

    Science.gov (United States)

    Goodchild, Martin S.

    Available from UMI in association with The British Library. This work has achieved the development of a fabrication method for the realisation of superconductor-insulator -superconductor (SIS) junctions based on niobium thin films with an artificial barrier layer. Such devices are likely to have advantages over lead alloy devices because of the enhanced mechanical and chemical stability. A principal objective was to attempt to exploit the offset mask technology developed by Dolan that has been successfully employed by Davies et.al. in the realisation of lead alloy SIS junction heterodyne mixers. In order to transfer this technology to niobium based devices it is essential that an evaporation method is used to allow shadow formation beneath the offset mask. As a result of the chemical reactivity and the low vapour pressure of niobium, a UHV system has been developed which incorporates an electrostatically focussed electron beam evaporation source. This is capable of providing deposition rates of close to 10A/sec. with a source to substrate distance of 120mm. During deposition the system pressure is below 5 times 10 ^{-9} mbar. These process parameters have been recorded, for a number of depositions, on a specially built data acquisition system controlled by a BBC microcomputer. Such recording allows detailed comparison of conditions which helps in the understanding of differences between the superconducting behaviour of various films. A further extremely important aspect of these real time measurements is that it helps to ensure optimum settings of the focus conditions of the electron beam source. The results of the depositions are extremely encouraging with critical temperatures of between 9.1 and 9.3K being achieved. These results compare well with expected values for bulk niobium. An all-metal offset mask technology has been developed to replace the photo-resist technique pioneered by Dolan. This new method is needed because the photo-resist is not compatible

  2. Structures and potential superconductivity in at high pressure: en route to "metallic hydrogen".

    Science.gov (United States)

    Feng, Ji; Grochala, Wojciech; Jaroń, Tomasz; Hoffmann, Roald; Bergara, Aitor; Ashcroft, N W

    2006-01-13

    A way to circumvent the high pressures needed to metallize hydrogen is to "precompress" it in hydrogen-rich molecules, a strategy probed theoretically for silane. We show that phases with tetrahedral SiH4 molecules should undergo phase transitions with sixfold- and eightfold-coordinate Si appearing above 25 GPa. The most stable structure found can be metallized at under a megabar and at a compression close to the prediction of Goldhammer-Herzfeld criterion. According to a BCS-like estimate, metallic silane should be a high-temperature superconductor.

  3. Effects of post-annealing and cobalt co-doping on superconducting properties of (Ca,Pr)Fe{sub 2}As{sub 2} single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Okada, T., E-mail: 8781303601@mail.ecc.u-tokyo.ac.jp; Ogino, H.; Yakita, H.; Yamamoto, A.; Kishio, K.; Shimoyama, J.

    2014-10-15

    Highlights: • Post-annealing at 400 °C killed superconductivity for Co-free sample. • Pr,Co co-doped samples maintained superconductivity even after annealing. • Two-step superconducting transition was observed via magnetization measurement. • Bulk superconductivity of low-T{sub c} component was confirmed. • Superconducting volume fraction of high-T{sub c} component was always small. - Abstract: In order to clarify the origin of anomalous superconductivity in (Ca,RE)Fe{sub 2}As{sub 2} system, Pr doped and Pr,Co co-doped CaFe{sub 2}As{sub 2} single crystals were grown by the FeAs flux method. These samples showed two-step superconducting transition with T{sub c1} = 25–42 K, and T{sub c2} < 16 K, suggesting that (Ca,RE)Fe{sub 2}As{sub 2} system has two superconducting components. Post-annealing performed for these crystals in evacuated quartz ampoules at various temperatures revealed that post-annealing at ∼400 °C increased the c-axis length for all samples. This indicates that as-grown crystals have a certain level of strain, which is released by post-annealing at ∼400 °C. Superconducting properties also changed dramatically by post-annealing. After annealing at 400 °C, some of the co-doped samples showed large superconducting volume fraction corresponding to the perfect diamagnetism below T{sub c2} and high J{sub c} values of 10{sup 4}–10{sup 5} A cm{sup −2} at 2 K in low field, indicating the bulk superconductivity of (Ca,RE)Fe{sub 2}As{sub 2} phase occurred below T{sub c2}. On the contrary, the superconducting volume fraction above T{sub c2} was always very small, suggesting that 40 K-class superconductivity observed in this system is originating in the local superconductivity in the crystal.

  4. Study of superconducting properties of ferrocene-added MgB{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Sudesh; Varma, G.D. [Department of Physics, Indian Institute of Technology Roorkee (India); Das, S.; Bernhard, C. [Department of Physics, Fribourg Centre for Nanomaterials-FriMat, University of Fribourg (Switzerland); Shripathi, T. [UGC-DAE CSR, University Campus, Indore (India)

    2014-07-15

    In the present study, we have shown the effects of ferrocene (FeC{sub 10}H{sub 10}) addition on the superconducting properties of polycrystalline MgB{sub 2} superconductor using transport and magnetic measurements. The addition of FeC{sub 10}H{sub 10} up to 2 wt% in the MgB{sub 2} sample has shown enhanced critical current density, J{sub C} in the entire magnetic field region without affecting much the transition temperature. At 10 K, with respect to a pristine MgB{sub 2} sample, J{sub C} has improved by a factor of 6.55 at 6 T applied field for 1 wt% FeC{sub 10}H{sub 10}. An improvement in the upper critical field, H{sub C{sub 2}} and irreversibility field, H{sub irr} has also been observed up to 2 wt% addition of FeC{sub 10}H{sub 10}. The value of H{sub C{sub 2}} (0) as obtained using the Ginzburg-Landau (GL)-theory fit of the experimental data increases by almost 2 T for 2 wt% FeC{sub 10}H{sub 10}-added MgB{sub 2} as compared to the pristine samples. From X-ray photoemission spectroscopy (XPS), we observed that the Fe is present in sample in the form of ferromagnetic oxides, Fe{sub 3}O{sub 4} and γ-Fe{sub 2}O{sub 3}. These ferromagnetic inclusions provide efficient pinning centers to improve J{sub C}(H) behavior. The flux pinning mechanisms present in the FeC{sub 10}H{sub 10}-added samples are described and discussed in this paper. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  5. Structural, transport, magnetic and superconducting properties of the pseudo-quaternary intermetallic system (Y 1-xGd x)Ni 2B 2C

    Science.gov (United States)

    Massalami, M. El; Bud'ko, S. L.; Giordanengo, B.; Fontes, M. B.; Mondragon, J. C.; Baggio-Saitovitch, E. M.

    1994-12-01

    The superconducting and the magnetic phase diagram (in x-T plane) of the pseudo-quaternary (Y 1-xGd x)Ni 2B 2C series is obtained. Superconductivity is observed to be montonically degraded with Gd-concentration for x < 0.25. For higher x, two magnetic transitions are observed. The nature of these transitions and their influence on the measured physical properties will be discussed.

  6. Structural and electronic properties of carbon nanotubes under hydrostatic pressures

    Institute of Scientific and Technical Information of China (English)

    Zhang Ying; Cao Jue-Xian; Yang Wei

    2008-01-01

    We studied the structural and electronic properties of carbon nanotubes under hydrostatic pressures based on molecular dynamics simulations and first principles band structure calculations.It is found that carbon nanotubes experience a hard-to-soft transition as external pressure increases.The bulk modulus of soft phase is two orders of magnitude smaller than that of hard phase.The band structure calculations show that band gap of (10,0) nanotube increases with the increase of pressure at low pressures. Above a critical pressure (5.70GPa),band gap of (10,0) nanotube drops rapidly and becomes zero at 6.62GPa. Moreover,the calculated charge density shows that a large pressure can induce an sp2-to-sp3 bonding transition,which is confirmed by recent experiments on deformed carbon nanotubes.

  7. Superconducting NbTiN Thin Films with Highly Uniform Properties over a 100 mm diameter Wafer

    CERN Document Server

    Thoen, D J; Haalebos, E A F; Klapwijk, T M; Baselmans, J J A; Endo, A

    2016-01-01

    Uniformity in thickness and electronic properties of superconducting niobium titanium nitride (NbTiN) thin films is a critical issue for upscaling superconducting electronics, such as microwave kinetic inductance detectors for submillimeter wave astronomy. In this article we make an experimental comparison between the uniformity of NbTiN thin films produced by two DC magnetron sputtering systems with vastly different target sizes: the Nordiko 2000 equipped with a circular 100mm diameter target, and the Evatec LLS801 with a rectangular target of 127 mm x 444.5 mm. In addition to the films deposited staticly in both systems, we have also deposited films in the LLS801 while shuttling the substrate in front of the target, with the aim of further enhancing the uniformity. Among these three setups, the LLS801 system with substrate shuttling has yielded the highest uniformity in film thickness (+/-2%), effective resistivity (decreasing by 5% from center to edge), and superconducting critical temperature (T_c = 15.0 ...

  8. Superconducting properties of very high quality NbN thin films grown by high temperature chemical vapor deposition

    Science.gov (United States)

    Hazra, D.; Tsavdaris, N.; Jebari, S.; Grimm, A.; Blanchet, F.; Mercier, F.; Blanquet, E.; Chapelier, C.; Hofheinz, M.

    2016-10-01

    Niobium nitride (NbN) is widely used in high-frequency superconducting electronics circuits because it has one of the highest superconducting transition temperatures ({T}{{c}}˜ 16.5 {{K}}) and largest gap among conventional superconductors. In its thin-film form, the T c of NbN is very sensitive to growth conditions and it still remains a challenge to grow NbN thin films (below 50 nm) with high T c. Here, we report on the superconducting properties of NbN thin films grown by high-temperature chemical vapor deposition (HTCVD). Transport measurements reveal significantly lower disorder than previously reported, characterized by a Ioffe-Regel parameter ({k}{{F}}{\\ell }) ˜ 12. Accordingly we observe {T}{{c}}˜ 17.06 {{K}} (point of 50% of normal state resistance), the highest value reported so far for films of thickness 50 nm or less, indicating that HTCVD could be particularly useful for growing high quality NbN thin films.

  9. Applied superconductivity

    CERN Document Server

    Newhouse, Vernon L

    1975-01-01

    Applied Superconductivity, Volume II, is part of a two-volume series on applied superconductivity. The first volume dealt with electronic applications and radiation detection, and contains a chapter on liquid helium refrigeration. The present volume discusses magnets, electromechanical applications, accelerators, and microwave and rf devices. The book opens with a chapter on high-field superconducting magnets, covering applications and magnet design. Subsequent chapters discuss superconductive machinery such as superconductive bearings and motors; rf superconducting devices; and future prospec

  10. Graphene: Carbon's superconducting footprint

    Science.gov (United States)

    Vafek, Oskar

    2012-02-01

    Graphene exhibits many extraordinary properties, but superconductivity isn't one of them. Two theoretical studies suggest that by decorating the surface of graphene with the right species of dopant atoms, or by using ionic liquid gating, superconductivity could yet be induced.

  11. Tissue electrical properties monitoring for the prevention of pressure sore.

    Science.gov (United States)

    Ching, Congo Tak-Shing; Chou, Mei-Yun; Jiang, Siou-Jhen; Huang, Su-Hua; Sun, Tai-Ping; Liu, Wei-Hao; Liu, Chia-Ming

    2011-12-01

    Pressure sores are a significant problem in the healthcare sector. Although they may cause considerable morbidity, they are preventable. The objectives of this study are to (1) investigate the electrical properties of a tissue close to and away from the pressure sore site, and (2) establish a new approach for objective, reliable, low-cost and noninvasive screening or detection of pressure sore in its early stage. Randomised controlled trial. Fifteen patients participated in this study. They all had stage I or stage II sacral pressure sores. Tiny surface electrodes in four-electrode configuration were used for all tissue electrical properties measurements recorded over the frequency range of 30-10 MHz. Intraclass correlation coefficient (ICC) showed that all measurements (ICC > 0.90 for all measurements) had good reliability and validity. The real part of impedance (R) and the imaginary part of impedance (X) of a tissue measured close to the pressure sore site was found to be significantly smaller (p pressure sore site at a specific frequency range (R: 30.00-38.55 Hz; X: 43.95-606.40 Hz). It was also found that the extracellular resistance (R(e)) and the ratio of extracellular resistance to intracellular resistance (R(e)/R(i)) of a tissue measured close to the pressure sore site were significantly smaller (p pressure sore site. Since the electrical properties (R, X, R(e), R(e)/R(i) ) of a tissue close to, and away from, the pressure sore site can be significantly distinguished, a potentially promising method for the screening of pressure sores at an early stage has been proposed.

  12. Magnetic field effects on the charge-density-wave and superconducting states in pressurized {alpha}-(BEDT-TTF){sub 2}KHg(SCN){sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Kartsovnik, M.V., E-mail: mark.kartsovnik@wmi.badw.de [Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching (Germany); Biberacher, W.; Andres, D.; Jakob, S.; Kunz, M.; Neumaier, K. [Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching (Germany); Mueller, H. [European Synchrotron Radiation Facility, 38043 Grenoble (France); Kushch, N.D. [Institute of Problems of Chemical Physics, 142432 Chernogolovka (Russian Federation)

    2012-06-01

    Coupling of a magnetic field to the orbital and spin degrees of freedom of charge carriers is well known to cause suppression of superconductivity. While the orbital pair-breaking generally dominates in conventional superconductors, the Pauli paramagnetic effect may become important in some heavy fermion compounds or strongly anisotropic materials such as high-T{sub c} or organic superconductors. The same two mechanisms are predicted to be operative also in the case of charge-density-wave (CDW) ordering. However, now they lead to opposite effects: the paramagnetic coupling weakens the CDW interaction whereas the orbital coupling enhances it in a system with an imperfectly nested Fermi surface. Here we report on the experimental evidence of both kinds of magnetic field effects on the CDW and superconducting instabilities in the layered organic metal {alpha}-(BEDT-TTF){sub 2}KHg(SCN){sub 4} under quasihydrostatic pressure.

  13. Magnetic field effects on the charge-density-wave and superconducting states in pressurized α-(BEDT-TTF)2KHg(SCN)4

    Science.gov (United States)

    Kartsovnik, M. V.; Biberacher, W.; Andres, D.; Jakob, S.; Kunz, M.; Neumaier, K.; Müller, H.; Kushch, N. D.

    2012-06-01

    Coupling of a magnetic field to the orbital and spin degrees of freedom of charge carriers is well known to cause suppression of superconductivity. While the orbital pair-breaking generally dominates in conventional superconductors, the Pauli paramagnetic effect may become important in some heavy fermion compounds or strongly anisotropic materials such as high-Tc or organic superconductors. The same two mechanisms are predicted to be operative also in the case of charge-density-wave (CDW) ordering. However, now they lead to opposite effects: the paramagnetic coupling weakens the CDW interaction whereas the orbital coupling enhances it in a system with an imperfectly nested Fermi surface. Here we report on the experimental evidence of both kinds of magnetic field effects on the CDW and superconducting instabilities in the layered organic metal α-(BEDT-TTF)2KHg(SCN)4 under quasihydrostatic pressure.

  14. Structural and superconducting properties of LaFeAs1-xSbxO1-yFy

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    We report the antimony(Sb) doping effect in a prototype system of iron-based superconductors LaFeAsO1-yFy(y=0,0.1,0.15).X-ray powder diffraction indicates that the lattice parameters increase with Sb content within the doping limit.Rietveld structural refinements show that,with the partial substitution of Sb for As,the thickness of the Fe2As2 layers increases significantly,whereas that of the La2O2 layers shrinks simultaneously.So a negative chemical pressure is indeed "applied" to the superconducting-active Fe2As2 layers,in contrast to the effect of positive chemical pressure by the phosphorus doping.Electrical resistance and magnetic susceptibility measurements indicate that,while the Sb doping hardly influences the SDW anomaly in LaFeAsO,it recovers SDW order for the optimally-doped sample of y=0.1.In the meantime,the superconducting transition temperature can be raised up to 30 K in LaFeAs1-xSbxO1-yFy with x=0.1 and y=0.15.The Sb doping effects are discussed in term of both J1-J2 model and Fermi Surface(FS) nesting scenario.

  15. Properties of Superconducting Mo, Mo2n and Trilayer Mo2n-Mo-Mo2n Thin Films

    Science.gov (United States)

    Barrentine, E. M.; Stevenson, T. R.; Brown, A. D.; Lowitz, A. E.; Noroozian, O.; U-Yen, K.; Eshan, N.; Hsieh, W. T.; Moseley, S. H.; Wollack, E. J.

    2014-01-01

    We present measurements of the properties of thin film superconducting Mo, Mo2N and Mo2N/Mo/Mo2N trilayers of interest for microwave kinetic inductance detector (MKID) applications. Using microwave resonator devices, we investigate the transition temperature, energy gaps, kinetic inductance, and internal quality factors of these materials. We present an Usadel-based interpretation of the trilayer transition temperature as a function of trilayer thicknesses, and a 2-gap interpretation to understand the change in kinetic inductance and internal resonance quality factor (Q) as a function of temperature.

  16. Improvement in Superconducting Properties of MgB2 Superconductors by Nanoscale Carbon-Based Compound Doping

    Institute of Scientific and Technical Information of China (English)

    Si-Hai Zhou

    2008-01-01

    MgB2 is a relatively new superconductor; it has attracted great interest from superconductor researchers all over the world. Thorough investigations have been carried out to study the material fabrication, as well as to study the material and superconducting properties from a fundamental physics point of view. The University of Wollongong has played a very active role in this research and a leading role in the research on high critical current density and high critical magnetic fields. Our recent research on the improve- ment of critical current density and the upper critical magnetic field by carbon-based compound doping is reviewed in this paper.

  17. Effects of lattice disorder on the superconducting properties of YBa 2Cu 3O 6.9 films

    Science.gov (United States)

    Gauzzi, Andrea; Pavuna, Davor

    1994-12-01

    We report on striking sensitivity of the superconducting properties of ion-beam sputtered YBa 2Cu 3O 6.9 films to the lattice disorder (induced by varying growth temperatures). Tc decreases with increasing disorder, while the width of the resistive transition and the normal state resistivity increase. We give a quantitative significance to this trend by expressing the degree of the disorder in terms of the lattice coherence length rc is extracted from the width of X-ray diffraction rocking curves. We find that Tc saturates to the maximum of ∼ 92 K for rc > 10 nm.

  18. Te vacancy-driven superconductivity in orthorhombic molybdenum ditelluride

    Science.gov (United States)

    Cho, Suyeon; Kang, Se Hwang; Yu, Ho Sung; Kim, Hyo Won; Ko, Wonhee; Hwang, Sung Woo; Han, Woo Hyun; Choe, Duk-Hyun; Jung, Young Hwa; Chang, Kee Joo; Lee, Young Hee; Yang, Heejun; Wng Kim, Sung

    2017-06-01

    Two-dimensional (2D) transition metal dichalcogenides (TMDs) have received great attentions because of diverse quantum electronic states such as topological insulating (TI), Weyl semimetallic (WSM) and superconducting states. Recently, the superconducting states emerged in pressurized semimetallic TMDs such as MoTe2 and WTe2 have become one of the central issues due to their predicted WSM states. However, the difficulty in synthetic control of chalcogen vacancies and the ambiguous magneto transport properties have hindered the rigorous study on superconducting and WSM states. Here, we report the emergence of superconductivity at 2.1 K in Te-deficient orthorhombic T d-MoTe2-x with an intrinsic electron-doping, while stoichiometric monoclinic 1T‧-MoTe2 shows no superconducting state down to 10 mK, but exhibits a large magnetoresistance of 32 000% at 2 K in a magnetic field of 14 T originating from nearly perfect compensation of electron and hole carriers. Scanning tunnelling spectroscopy and synchrotron x-ray diffraction combined with theoretical calculations clarify that Te vacancies trigger superconductivity via intrinsic electron doping and the evolution of the T d phase from the 1T‧ phase below 200 K. Unlike the pressure-induced superconducting state of monoclinic MoTe2, this Te vacancy-induced superconductivity is emerged in orthorhombic MoTe2, which is predicted as Weyl semimetal, via electron-doping. This chalcogen vacancy induced-superconductivity provides a new route for cultivating superconducting state together with WSM state in 2D van der Waals materials.

  19. Effect of hydrostatic pressure on elastic properties of ZDTP tribofilms

    CERN Document Server

    Demmou, Karim; Loubet, Jean-Luc

    2007-01-01

    Previous studies have shown that the elastic properties of Zinc Dialkyl-dithiophosphate (ZDTP) tribofilms measured by nanoindentation increase versus applied pressure (Anvil effect) [1, 2]. The aim of this paper is to demonstrate that, up to 8 GPa, this increase is a reversible phenomenon. A ZDTP tribofilm has been produced on "AISI 52100" steel substrate using a Cameron-Plint tribometer. After its formation, a hydrostatic pressure of about 8 GPa was applied during one minute on the tribofilm using a large radius steel ball ("Brinell-like" test). Nanoindentation tests were performed with a Berkovich tip on pads in order to measure and compare the mechanical properties of the tribofilm inside and outside the macroscopic plastically deformed area. Careful AFM observations have been carried out on each indent in order to take into account actual contact area. No difference in elastic properties was observed between the two areas: tribofilm modulus and pressure sensitivity are the same inside and outside the resi...

  20. Synthesis and properties of a new superconducting compound (ZrCuxSe2)

    Science.gov (United States)

    Generoso, Ana Carolina; Baptista, Naiara; Renosto, Sergio; Jefferson Machado, Antonio

    2012-02-01

    Since the discovery of superconductivity in chalcogenides in Fe-Se system and in iron pnictides much attention have been give for synthesis of new materials which can exhibit superconductivity. Within this context in this work we show results which suggest the existence of a new selenite intercalate with copper atoms in the ZrCuxSe2 nominal composition, where x is 0.1 <= x <= 0.4 interval. A superconductor behavior begins in the ZrCu0.3Se2 with superconducting critical temperature close to 9.0 K. ZrSe2 is a compound which crystallize in the hexagonal symmetry with CdI2 prototype structure belongs to the space group P-32/m1. Indeed, copper is intercalating between Se-Se which have van der Walls interaction in the ZrSe2 compound. This intercalation with copper atoms, produce superconductivity in the matrix compound (ZrSe2) which is not superconductor. The copper intercalation in the matrix compound crystallizes in a LiCrS2 prototype structure.

  1. Role of kinetic inductance in transport properties of shunted superconducting nanowires.

    Science.gov (United States)

    Lin, Shi-Zeng; Roy, Dibyendu

    2013-08-14

    Recently, transport measurements have been carried out in resistively shunted long superconducting nanowires (Brenner et al 2012 Phys. Rev. B 85 224507). The measured voltage-current (V-I) characteristics were explained by the appearance of the phase slip centers in the shunted wire, and the whole wire was modeled as a single Josephson junction. The kinetic inductance of the long nanowires used in experiments is generally large. Here we argue that the shunted superconducting nanowire acts as a Josephson junction in series with an inductor. The inductance depends on the length and the cross section of the wire. The inclusion of inductance in our analysis modifies the V-I curves, and increases the rate of switching from the superconducting state to the resistive state. The quantitative differences can be quite large in some practical parameter sets, and might be important to properly understand the experimental results. Our proposed model can be verified experimentally by studying the shunted superconducting nanowires of different lengths and cross sections.

  2. Doping effects of transition metals on superconducting properties of (Ca,RE)FeAs2

    Science.gov (United States)

    Yakita, Hiroyuki; Ogino, Hiraku; Okada, Tomoyuki; Yamamoto, Akiyasu; Kishio, Kohji; Shimoyama, Jun-Ichi; Iyo, Akira; Eisaki, Hiroshi; Sala, Alberto

    2015-03-01

    At the previous March Meeting, we reported new iron based superconductors (Ca,RE)FeAs2 (Ca112) (RE = La-Nd, Sm-Gd)[ 1 , 2 ]. Superconducting transition was observed in all samples except for Ce-doped sample, and Tc of La-doped sample exceeded 30 K. In this study, we have synthesized transition metals (TM=Mn, Co, Ni) co-doped Ca112 samples. Mn co-doping suppressed superconductivity. On the contrary, enhancement of Tc with sharp superconducting transitions was observed in most of the Co or Ni co-doped samples. Tc of Co co-doped samples decreased with a decrease in ionic radii of RE3+ from 38 K for RE = La to 29 K for RE = Gd, though Eu doped sample showed exceptionally low Tc = 21 K. Jc value of La and Co co-doped sample estimated from magnetization measurement is approximately 2.0 x 104 Acm-2at 2 K suggesting bulk superconductivity.

  3. Microwave properties of YBa2Cu3O(7-delta) high-transition-temperature superconducting thin films measured by the power transmission method

    Science.gov (United States)

    Miranda, F. A.; Gordon, W. L.; Bhasin, K. B.; Heinen, V. O.; Warner, J. D.

    1991-01-01

    The microwave response of YBa2Cu3O(7-delta) superconducting thin films deposited on LaAlO3, MgO, YSZ, and LaGaO3 substrates are studied. It is found that the microwave transmission properties are very weakly dependent on temperature in the normal state but change drastically upon transition to the superconducting state. In particular, the transmission decreases and there is a negative phase shift with respect to the phase at room temperature when the sample is cooled through its transition temperature. The magnetic penetration depth for all the films was determined from the surface reactance of the films. The microwave complex conductivity is determined in both the normal and the superconducting state. It is observed that both sigma1 and sigma2 increase in transition to the superconducting state. The surface resistivity is calculated for all the films.

  4. The decay properties of the trapped magnetic field in HTS bulk superconducting actuator by AC controlled magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Kim, S.B. [Department of Electrical and Electronic Engineering, Okayama University, 3-1-1, Tsushima Naka, Okayama 700-8530 (Japan); Uwani, Y., E-mail: gen422310@s.okayama-u.ac.jp [Department of Electrical and Electronic Engineering, Okayama University, 3-1-1, Tsushima Naka, Okayama 700-8530 (Japan); Joo, J.H.; Kawamoto, R. [Department of Electrical and Electronic Engineering, Okayama University, 3-1-1, Tsushima Naka, Okayama 700-8530 (Japan); Jo, Y.S. [Center for Applied Superconductivity Technology, Korea Electrotechnology Research Institute, Seongju-dong, Changwon 641-120 (Korea, Republic of)

    2011-11-15

    The electric device applications of a high temperature superconducting (HTS) bulk magnet, having stable levitation and suspension properties according to their strong flux pinning force, have been proposed and developed. We have been investigating a three-dimensional (3-D) superconducting actuator using HTS bulks to develop a non-contract transportation device which moves freely in space. It is certain for our proposed 3-D superconducting actuator to be useful as a transporter used in a clean room where silicon wafers, which do not like mechanical contact and dust, are manufactured. The proposed actuator consists of the trapped HTS bulk as a mover and two-dimensionally arranged electromagnets as a stator. Up to now, the electromagnets consisted with iron core and copper coil were used as a stator, and each electromagnet was individually controlled using DC power supplies. In our previous work, the unstable movement characteristics of HTS bulk were observed under the DC operation, and the AC electromagnets driven with AC controlled current was proposed to solve these problems. In general, the trapped magnetic field in HTS bulk was decayed by a time-varying external magnetic field. Thus, it needs to optimize the shapes of AC electromagnets and operating patterns, the decay properties of the trapped magnetic field in the HTS bulk mover by the AC magnetic field should be cleared. In this paper, the influences of the frequency, the overall operating time, the strength of magnetization field and drive current against the decay of trapped magnetic field were experimentally studied using the fabricated AC electromagnets.

  5. Superconducting optical modulator

    Science.gov (United States)

    Bunt, Patricia S.; Ference, Thomas G.; Puzey, Kenneth A.; Tanner, David B.; Tache, Nacira; Varhue, Walter J.

    2000-12-01

    An optical modulator based on the physical properties of high temperature superconductors has been fabricated and tested. The modulator was constructed form a film of Yttrium Barium Copper Oxide (YBCO) grown on undoped silicon with a buffer layer of Yttria Stabilized Zirconia. Standard lithographic procedures were used to pattern the superconducting film into a micro bridge. Optical modulation was achieved by passing IR light through the composite structure normal to the micro bridge and switching the superconducting film in the bridge region between the superconducting and non-superconducting states. In the superconducting state, IR light reflects from the superconducting film surface. When a critical current is passed through the micro bridge, it causes the film in this region to switch to the non-superconducting state allowing IR light to pass through it. Superconducting materials have the potential to switch between these two states at speeds up to 1 picosecond using electrical current. Presently, fiber optic transmission capacity is limited by the rate at which optical data can be modulated. The superconducting modulator, when combined with other components, may have the potential to increase the transmission capacity of fiber optic lines.

  6. Hybridization and suppression of the superconductivity in CeFeAsO1-y. Pressure and temperature dependences of the electronic structure

    Energy Technology Data Exchange (ETDEWEB)

    Yamaoka, Hitoshi [Inst. of Physical and Chemical Research (RIKEN), Wako (Japan); Jarrige, Ignace [Japan Atomic Energy Agency (JAEA), Hyogo (Japan); Ikeda-Ohno, Atsushi [Japan Atomic Energy Agency (JAEA), Hyogo (Japan); Tsutsui, Satoshi [Japan Synchrotron Radiation Research Inst., Hyogo (Japan); Lin, Jung-Fu [Univ. of Texas, Austin, TX (United States); Takeshita, Nao [National Inst. of Advanced Industrial Science adn Technology (AIST), Ibaraki (Japan); Transformative Research-Project on Iron Pnictides (TRIP), Tokyo (Japan); Miyazawa, Kiichi [National Inst. of Advanced Industrial Science adn Technology (AIST), Ibaraki (Japan); Transformative Research-Project on Iron Pnictides (TRIP), Tokyo (Japan); Tokyo Univ. of Science, Chiba (Japan); Iyo, Akira [National Inst. of Advanced Industrial Science adn Technology (AIST), Ibaraki (Japan); Transformative Research-Project on Iron Pnictides (TRIP), Tokyo (Japan); Tokyo Univ. of Science, Chiba (Japan); Kito, Hijiri [National Inst. of Advanced Industrial Science adn Technology (AIST), Ibaraki (Japan); Transformative Research-Project on Iron Pnictides (TRIP), Tokyo (Japan); Eisaki, Hiroshi [National Inst. of Advanced Industrial Science adn Technology (AIST), Ibaraki (Japan); Transformative Research-Project on Iron Pnictides (TRIP), Tokyo (Japan); Hiraoka, Nozomu [National Synchrotron Radiation Research Center, Hsinchu (Taiwan); Ishii, Hirofumi [National Synchrotron Radiation Research Center, Hsinchu (Taiwan); Tsuei, Ku-Ding [National Synchrotron Radiation Research Center, Hsinchu (Taiwan)

    2010-09-23

    Pressure and temperature dependence of the electronic structure of superconducting (SC) CeFeAsO1-y and non-SC CeFeAsO1-y have been investigated using two complementary hard x-ray spectroscopic probes at the Ce L3 edge, partial fluorescence yield x-ray absorption spectroscopy and resonant x-ray emission spectroscopy. With increasing pressure, the ratio between the intensity of the peak related to the f0 (Ce4+ ) state and that of the f1 (Ce3+ ) state, I(f0)/I(f1 ), is found to increase continuously for both compounds, indicating a continuous increase in the Ce valence. The valence of non-SC CeFeAsO1-y is found to be slightly higher than that of SC CeFeAsO1-y in the entire pressure and temperature ranges of this study. The valence of CeFeAsO1-y around 6 GPa, where the superconductivity breaks down, is estimated to be ~3.0 , but no change in the valence is observed upon cooling. The dependence of the interatomic distances on the concentration of oxygen vacancies is studied via extended absorption fine structure spectroscopy.

  7. Phase Diagram Of UGe2: The Magnetic Transition within the Ferromagnetic Phase and the Superconducting Transition; the Effect of Magnetic Field on the Ambient-Pressure Ferromagnetic Phase

    Science.gov (United States)

    Phillips, N. E.; Bouquet, F.; Fisher, R. A.; Hardy, F.; Oeschler, N.; Lashley, J. C.; Flouquet, J.; Huxley, A.

    2007-03-01

    Superconductivity in UGe2 occurs near 1.2 GPa at the 0-K termination of the phase boundary (Tx, Px) of a magnetic transition that occurs within the ferromagnetic phase. Ambient-pressure specific-heat measurements show a hysteretic transition at Tx(0) ˜ 22 K, reminiscent of the CDW/SDW transition in α-U, and consistent with the suggestion that the transition in UGe2 is also a CDW/SDW transition. The magnetic field dependence of the specific heat, at ambient pressure, demonstrates the presence of structure in the electron density of states and an unusual nature of the ferromagnetic ordering at the Curie temperature. Specific-heat measurements to 1.8 GPa give an estimate of the latent heat of the transition and determine the phase boundary for 1 <= T <= 11 K. Contrary to expectations, the onset temperature of the superconducting transition is independent of pressure in the region in which it was observed, 1.08 <= P <= 1.35 GPa.

  8. Magnetic and superconducting nanowires

    DEFF Research Database (Denmark)

    Piraux, L.; Encinas, A.; Vila, L.

    2005-01-01

    magnetic and superconducting nanowires. Using different approaches entailing measurements on both single wires and arrays, numerous interesting physical properties have been identified in relation to the nanoscopic dimensions of these materials. Finally, various novel applications of the nanowires are also...

  9. Pressure Dependent Electronic Properties of Organic Semiconductors from First Principles

    Science.gov (United States)

    Knuth, Franz; Carbogno, Christian; Blum, Volker; Scheffler, Matthias

    2015-03-01

    The electronic properties of organic semiconductors typically exhibit a significant dependence on the strain, stress, and pressure. In this contribution, we present the theoretical background, assessment of approximations, and results of electronic and transport properties in the framework of density-functional theory. Our implementation considers the analytical strain derivatives (stress tensor) including the contributions that stem from (a) van-der-Waals interactions and (b) the Fock-exchange in hybrid functionals. We validate our approach by investigating the geometric and electronic changes that occur in polyacetylene and anthracene under hydrostatic pressure. We show that the fraction of exact exchange included in the calculations is critical - and non-trivial to choose - for a correct description of these systems. Furthermore, we point out trends for the electrical conductivity under pressure and identify the dominant charge carriers and transport directions.

  10. Vibrational properties of cagelike diamondoid nitrogen at high pressure

    Institute of Scientific and Technical Information of China (English)

    Wang Hui

    2013-01-01

    Under high pressure,a cagelike diamondoid nitrogen structure was lately discovered by first-principles structure researches.This newly proposed structure is very unique and has not been observed in any other element.Using densityfunctional calculations,we study the pressure effect on its vibrational properties.The Born effective charges are calculated,and the resulting LO-TO splittings of certain infrared active modes are beyond 20 cm-1.We depict the Γ-point vibrational modes and find the breathing mode,rotational mode,and shearing mode.Frequencies of all the optical modes increase with pressure increasing.Moreover,the relation between the breathing mode frequency and the nitrogen cage diameter is discussed in detail.Our calculation results give a deeper insight into the vibrational properties of the cagelike diamondoid nitrogen.

  11. Polyunsaturation in lipid membranes: dynamic properties and lateral pressure profiles.

    Science.gov (United States)

    Ollila, Samuli; Hyvönen, Marja T; Vattulainen, Ilpo

    2007-03-29

    We elucidate the influence of unsaturation on single-component membrane properties, focusing on their dynamical aspects and lateral pressure profiles across the membrane. To this end, we employ atomistic molecular dynamics simulations to study five different membrane systems with varying degrees of unsaturation, starting from saturated membranes and systematically increasing the level of unsaturation, ending up with a bilayer of phospholipids containing the docosahexaenoic acid. For an increasing level of unsaturation, we find considerable effects on dynamical properties, such as accelerated dynamics of the phosphocholine head groups and glycerol backbones and speeded up rotational dynamics of the lipid molecules. The lateral pressure profile is found to be altered by the degree of unsaturation. For an increasing number of double bonds, the peak in the middle of the bilayer decreases. This is compensated for by changes in the membrane-water interface region in terms of increasing peak heights of the lateral pressure profile. Implications of the findings are briefly discussed.

  12. Superconducting correlations and thermodynamic properties in 2D square and triangular t-J model

    Science.gov (United States)

    Ogata, Masao

    2006-03-01

    Equal-time superconducting correlation functions of the two-dimensional t-J model on the square lattice are studied using high-temperature expansion method.[1] The sum of the pairing correlation, its spatial dependence and correlation length are obtained down to T ˜0.2t. By comparison of single-particle contributions in the correlation functions, we find effective attractive interactions between quasi-particles in dx^2-y^2-wave channel. It is shown that d-wave correlation grows rapidly at low temperatures for the doping 0.1 0 with hole doping, a rapid growth of effective d-wave paring interaction is found that indicates the resonating-valence-bond superconductivity. In contrast, when tJ. Phys. Soc. Japan 74, 1390 (2005). [2] T. Koretsune and M. Ogata, Phys. Rev. Lett. 89, 116401 (2002), and Phys. Rev. B72, 134513 (2005).

  13. Transport properties of a superconducting single-electron transistor coupled to a nanomechanical oscillator

    Science.gov (United States)

    Koerting, V.; Schmidt, T. L.; Doiron, C. B.; Trauzettel, B.; Bruder, C.

    2009-04-01

    We investigate a superconducting single-electron transistor capacitively coupled to a nanomechanical oscillator and focus on the double Josephson quasiparticle resonance. The existence of two coherent Cooper-pair tunneling events is shown to lead to pronounced back action effects. Measuring the current and the shot noise provides a direct way of gaining information on the state of the oscillator. In addition to an analytical discussion of the linear-response regime, we discuss and compare results of higher-order approximation schemes and a fully numerical solution. We find that cooling of the mechanical resonator is possible and that there are driven and bistable oscillator states at low couplings. Finally, we also discuss the frequency dependence of the charge noise and the current noise of the superconducting single electron transistor.

  14. Simple One-Step Synthesis and Superconducting Properties of SmFeAsO1-x Fx

    Institute of Scientific and Technical Information of China (English)

    MA Yan-Wei; GAO Zhao-Shun; WANG Lei; QI Yan-Peng; WANG Dong-Liang; ZHANG Xian-Ping

    2009-01-01

    The recent discovery of superconductivity in REFeAsO (RE,rare-earth metal) has generated enormous interest because these materials are the first non-copper oxide superconductors with critical temperatures Tc exceeding 50 K as well as upper critical fields well above 100 T.However,for these new superconductors,very complicated synthesis routes,such as the complex two-step synthesis or high-pressure sintering,are required.Furthermore,there is the toxicity and volatility of arsenic to consider,sometimes a sealed quartz tube of arsenic exploded during annealing.We present a new method for producing high-temperature SmFeAsO1-xFx superconductors by using a one-step sintering process.Superconducting transition with the onset temperature of 54.6 K and high critical fields Hc2 (0) ≥ 200 T were confirmed in SmFeAsO0.7F0.3.At 5 K and at self field,critical current densities Jc estimated from the magnetization hysteresis using the whole sample size and the average particle size have reached 8.5×103 and 1.2×106 A/cm2,respectively.Moreover,Jc exhibited a very weak dependence on magnetic field. This simple and safe one-step synthesis technique should be effective in other rare earth derivatives of iron-based superconductors.

  15. Effects of strain on the superconducting properties of niobium-tin conductors

    Energy Technology Data Exchange (ETDEWEB)

    Hoard, R.W.

    1980-11-01

    Investigations were performed to ascertain additional information on the connection between the cubic to tetragonal martensitic phase transformation and the phenomenon of superconductivity in Nb/sub 3/Sn. Of particular interest is the degradation of the critical parameters, such as T/sub c/, H/sub c2/, and J/sub c/, with mechanical straining of the superconductor. These studies yielded information that assisted in the derivation of the critical current-strain scaling laws mentioned above.

  16. Recommended reference materials for realization of physicochemical properties pressure-volume-temperature relationships

    CERN Document Server

    Herington, E F G

    1977-01-01

    Recommended Reference Materials for Realization of Physicochemical Properties presents recommendations of reference materials for use in measurements involving physicochemical properties, namely, vapor pressure; liquid-vapor critical temperature and critical pressure; orthobaric volumes of liquid and vapor; pressure-volume-temperature properties of the unsaturated vapor or gas; and pressure-volume-temperature properties of the compressed liquid. This monograph focuses on reference materials for vapor pressures at temperatures up to 770 K, as well as critical temperatures and critical pressures

  17. Electrical Resistivity and Thermodynamic Properties of Iron Under High Pressure

    Science.gov (United States)

    Hieu, Ho Khac; Hai, Tran Thi; Hong, Nguyen Thi; Sang, Ngo Dinh; Tuyen, Nguyen Viet

    2017-03-01

    In this work, the electrical resistivity and thermodynamic properties of iron under high pressure have been investigated by using the semi-empirical approach. The recently well-established Grüneisen parameter expressions have been applied to derive the Debye frequency and temperature under compression. Using these results combined with the Bloch-Grüneisen law, the resistivity of iron has also been determined up to Earth's core pressures. We show that the electrical resistivity diminished gradually with pressure and saturates at high pressure. Our model gives low electrical resistivity values which are in agreement with the recent experimental measurements. The low resistivity may be attributed to the well-known resistivity saturation effect at high temperature, which was not considered in earlier models of core conductivity.

  18. Effect of pressure on the phonon properties of europium chalcogenides

    Indian Academy of Sciences (India)

    U K Sakalle; P K Jha; S P Sanyal

    2000-06-01

    Lattice vibrational properties of europium chalcogenides have been investigated at high pressure by using a simple lattice dynamical model theory viz. the three-body force rigid ion model (TRIM) which includes long range three-body interaction arising due to charge transfer effects. The dispersion curves for the four Eu-chalcogenides agree reasonably well with the available experimental data. Variation of LO, TO, LA and TA phonons with pressure have also been studied at the symmetry points of the brillouin zone (BZ) for Euchalcogenides for the first time by using a lattice dynamical model theory. We have also calculated the one phonon density of states and compared them with the first order Raman scattering results. The calculation of one phonon density of states for Eu-chalcogenides has also been extended up to the phase transition pressure. We observed a pronounced shift in phonon spectrum as pressure is increased.

  19. Structure, texture, and properties of superconductive electrolytic niobium coatings on glassy carbon

    Science.gov (United States)

    Kolosov, V. N.; Shevyrev, A. A.

    2016-01-01

    Superconductive electrolytic niobium coatings 0.1-100 μm thick are prepared via electrochemical deposition onto SU-2000 glassy carbon substrates in (LiF + NaF + KF)eut-K2NbF7 molten salt. Their structure, texture, and residual stresses are investigated by X-ray diffraction methods. It is shown that, when depositing the coatings, the diffusion superconductive layer of niobium carbide is formed at the substrate-coating interface. The sequence of changes in the axis of the texture of niobium coating from through to a textureless state with an increase in their thickness is established. It is found that, in the interval 0.5-5 μm, the sign of the stress changes (compressive stresses change into tensile stresses) and it reaches its maximum value. With an increase in the coating thickness from 5 to 100 μm, tensile stresses decrease from 345 to 80 MPa. It is shown that the coatings formed can be used as the material for creating a working layer of a superconducting cryogenic gyroscope rotor.

  20. Effect of high pressure on physicochemical properties of meat.

    Science.gov (United States)

    Buckow, Roman; Sikes, Anita; Tume, Ron

    2013-01-01

    The application of high pressure offers some interesting opportunities in the processing of muscle-based food products. It is well known that high-pressure processing can prolong the shelf life of meat products in addition to chilling but the pressure-labile nature of protein systems limits the commercial range of applications. High pressure can affect the texture and gel-forming properties of myofibrillar proteins and, hence, has been suggested as a physical and additive-free alternative to tenderize and soften or restructure meat and fish products. However, the rate and magnitude at which pressure and temperature effects take place in muscles are variable and depend on a number of circumstances and conditions that are still not precisely known. This review provides an overview of the current knowledge of the effects of high pressure on muscle tissue over a range of temperatures as it relates to meat texture, microstructure, color, enzymes, lipid oxidation, and pressure-induced gelation of myofibrillar proteins.

  1. Fabrication and properties of single domain GdBCO superconducting rings by a buffer aided Gd+011 TSIG method

    Science.gov (United States)

    Yang, P. T.; Yang, W. M.; Chen, J. L.

    2017-08-01

    Single domain REBCO bulk superconductors can be fabricated by both the top-seeded melt texture growth process and the top-seeded infiltration and growth (TSIG) process. The buffer pellet technique used in these two methods has been demonstrated to act as an efficient seed and to aid the growth of the REBCO bulk superconductors. In this paper, we combined the Gd+011 TSIG method and buffer pellet technique together to fabricate single domain REBCO superconducting rings without any machining and obvious shrinkage of the final ring, which shows a satisfactory trapped field and very good magnetic shielding at the same time. It is found that (1) a single domain GdBCO ring, with inner diameter of 10 mm and outer diameter of 32 mm, has been fabricated by this method successfully. (2) The trapped field (0.32 T, 77 K) and maximum levitation force (80.1 N, 77 K) of the single domain GdBCO ring are nearly the same as the trapped field (0.33 T, 77 K) and maximum levitation force (80.2 N, 77 K) of the single domain GdBCO bulk with the same diameter and thickness, but the uniformity of trapped field is much better for the single domain GdBCO ring. (3) The single domain GdBCO ring shows very good magnetic shielding property, the magnetic flux density shielded by the superconducting ring is up to 0.40 T at 77 K, which is much higher than that of reported samples. The results indicate that the buffer aided Gd+011 TSIG method can provide an important way to fabricate high quality single domain REBCO superconducting rings directly.

  2. Nonlinear elastic properties of superconducting antiperovskites MNNi 3 (M =Zn, Cd, Mg, Al, Ga, and In) from first principles

    KAUST Repository

    Liu, Lili

    2014-05-22

    We present theoretical studies for the third-order elastic constants (TOECs) of superconducting antiperovskites MNNi 3 (M = Zn, Cd, Mg, Al, Ga, and In) using the density functional theory (DFT) and homogeneous deformation method. From the nonlinear least-square fitting, the elastic constants are extracted from a polynomial fit to the calculated strain-energy data. Calculated second-order elastic constants (SOECs) are compared with the previous theoretical calculations, and a very good agreement was found. The nonlinear effects often play an important role when the finite strains are larger than approximately 2.5 %. Besides, we have computed the pressure derivatives of SOECs and provided rough estimations for the Grüneisen constants of long-wavelength acoustic modes by using the calculated TOECs. © 2014 Springer Science+Business Media New York.

  3. Thermodynamic properties of liquid sodium under high pressure

    Science.gov (United States)

    Li, Huaming; Zhang, Xiaoxiao; Sun, Yongli; Li, Mo

    2017-04-01

    Acquiring reliable thermodynamic properties in liquid metals at high pressure and temperature is still a challenge in both experiment and theory. Equation of state (EoS) offers an alternative approach free of many of the difficulties. Here using the EoS of a power law form we obtained the thermodynamic properties of liquid sodium under pressure along the isothermal lines, including isothermal buck modulus, thermal expansion coefficient, Grüneisen parameter, and Anderson-Grüneisen parameter. The results are in excellent agreement with available experimental data measured by a piezometer at high temperature and high pressure and sound velocity measurement with pulse-echo technique. We found that the pressure derivative of the isothermal bulk modulus at zero pressure is a monotonic function of temperature and has a value around 4. In addition, unexpected crossing points were found in the isobaric thermal expansion coefficient and Grüneisen parameter; and a minimum in the isobaric heat under isothermal compression was also observed. While some of these detailed predictions are yet to be confirmed by further experiment, our results suggest that the power law form may be a more suitable choice for the EoS of liquids metals.

  4. Synthesis of novel strontium-based cuprate superconducting thin films, and the relationship between their crystal structures and electrical properties

    Science.gov (United States)

    Chang, Kuo-Wei

    2000-12-01

    Novel Sr-based cuprate thin films were investigated to explore their potential as next generation superconducting materials. Thin films of infinite-layer compound (Sr,Ca)CuO2 (no blocking layer), cuprate oxycarbonate Sr2CuO2(CO3) (carbonate blocking layer), and Tl(Sr,Ba)2Can-1CunOy (n = 2 and 3) (thin blocking layer) were synthesized using metal-organic chemical vapor deposition. The structure and defect chemistry of the blocking layers of these cuprate compounds were found to have profound effects on the transport properties both in the normal state and the superconducting state. Phase pure, epitaxial infinite-layer compound (Sr1-xCa x)CuO2 thin films were deposited on SrTiO3(100) substrates. However, these films were always semiconducting with resistivities of the order of 1 ohm- cm and with carrier concentrations of 1017~10 19cm-3, which is two to four orders of magnitude lower than the typical superconducting cuprates. The low carrier concentration was attributed to the absence of blocking layers containing a sufficient concentration of charged defects. Transport was via variable range hopping conduction. By annealing in air, the infinite-layer compound SrCuO2 thin films reacted with the CO2 in air to generate Sr 2CuO2(CO3) thin films. Upon formation of carbonate blocking layers, charger carriers were introduced into the Sr2CuO 2(CO3) thin films through the partial substitution of carbon by copper or boron in the SrCO3 blocking layers. After oxygen annealing or upon boron substitution, the carrier concentration increased up to 10 21 cm-3. A superconducting onset temperature of 34K and a zero resistivity temperature of 20K have been observed for Sr 2CuO2(C1-xBx)O3 thin films. A critical carrier density of 0.10~0.12 holes/Cu was required to render superconductivity. The effect of crystal structure on the critical current density was investigated by measuring the vortex pinning energies of Tl2Ba2CaCu 2Oy (Tl-2212) and Tl(Sr,Ba)2Ca Cu2O y (Tl- (Sr,Ba)1212) thin

  5. Superconductivity in carbon nanomaterials

    Science.gov (United States)

    Dlugon, Katarzyna

    The purpose of this thesis is to explain the phenomenon of superconductivity in carbon nanomaterials such as graphene, fullerenes and carbon nanotubes. In the introductory chapter, there is a description of superconductivity and how it occurs at critical temperature (Tc) that is characteristic and different to every superconducting material. The discovery of superconductivity in mercury in 1911 by Dutch physicist Heike Kamerlingh Onnes is also mentioned. Different types of superconductors, type I and type II, low and high temperatures superconductors, as well as the BCS theory that was developed in 1957 by Bardeen, Cooper, and Schrieffer, are also described in detail. The BCS theory explains how Cooper's pairs are formed and how they are responsible for the superconducting properties of many materials. The following chapters explain superconductivity in doped fullerenes, graphene and carbon nanotubes, respectively. There is a thorough explanation followed by many examples of different types of carbon nanomaterials in which small changes in chemical structure cause significant changes in superconducting properties. The goal of this research was not only to take into consideration well known carbon based superconductors but also to search for the newest available materials such as the fullerene nanowhiskers discovered quite recently. There is also a presentation of fairly new ideas about inducing superconductivity in a monolayer of graphene which is more challenging than inducing superconductivity in graphite by simply intercalating metal atoms between its graphene sheets. An effort has been taken to look for any available information about carbon nanomaterials that have the potential to superconduct at room temperature, mainly because discovery of such materials would be a real revolution in the modern world, although no such materials have been discovered yet.

  6. Fabrication and superconducting properties of internal Mg diffusion processed MgB2 wires using MgB4 precursors

    Science.gov (United States)

    Xu, Da; Wang, Dongliang; Yao, Chao; Zhang, Xianping; Ma, Yanwei; Oguro, Hidetoshi; Awaji, Satoshi; Watanabe, Kazuo

    2016-10-01

    Monofilament MgB2/Nb/Monel wires were fabricated using three different MgB4 precursors by an internal Mg diffusion (IMD) process. The wire geometry and heat-treatment conditions were optimized in order to improve the critical current density (J c) of the MgB2 wire. The influences of the quality of MgB4 powders, such as the particle size and MgO impurity, on the microstructure and superconducting properties of the wires were discussed. Although there were small amounts of voids, unreacted MgB4 particles and MgO impurity existed in the superconducting layers, and the transport layer J c of the wire with the MgB4 precursor reached 3.0 × 104 A cm-2 at 4.2 K and 10 T, which was comparable to that of IMD-processed wires fabricated using boron precursors. Both the non-barrier J c and engineering J c of MgB2 wire made using a MgB4 precursor were enhanced due to the improved grain connectivity and the enlarged fill factor.

  7. Addition effects of nanoscale NiO on microstructure and superconducting properties of MgB{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Ranot, Mahipal; Jang, S. H.; Oh, Y. S.; Shinde, K. P.; Kang, S. H.; Chung, K. C. [Korea Institute of Materials Science, Changwon (Korea, Republic of)

    2016-03-15

    We have investigated the addition effect of NiO magnetic nanoparticles on crystal structure, microstructure as well as superconducting properties of MgB{sub 2}. NiO-added MgB{sub 2} samples were prepared by the solid-state reaction method. The superconducting transition temperature (Tc) of 37.91 K was obtained for pure MgB{sub 2}, and Tc was found to decrease systematically on increasing the addition level of NiO. X-ray diffraction (XRD) analysis revealed that no substitution of Ni for Mg in the lattice of MgB{sub 2} was occurred. The microstructural analysis shows that the pure MgB{sub 2} sample consists of plate shape MgB{sub 2} grains, and the grains get refined to smaller size with the addition of NiO nanoparticles. At 5 K, high values of critical current density (Jc) were obtained for small amount NiO-added MgB{sub 2} samples as compared to pure sample. The enhancement in Jc could be attributed to the refinement of MgB{sub 2} grains which leads to high density of grain boundaries in NiO-added MgB{sub 2} samples.

  8. Structural, Magnetic, and Superconducting Properties of Caged Compounds ROs2Zn20 (R = La, Ce, Pr, and Nd)

    Science.gov (United States)

    Wakiya, Kazuhei; Onimaru, Takahiro; Matsumoto, Keisuke T.; Yamane, Yu; Nagasawa, Naohiro; Umeo, Kazunori; Kittaka, Shunichiro; Sakakibara, Toshiro; Matsushita, Yoshitaka; Takabatake, Toshiro

    2017-03-01

    The electrical resistivity, magnetization, and specific heat of the caged compounds ROs2Zn20 (R = La, Ce, Pr, and Nd) have been measured to study their structural, magnetic, and superconducting properties. These measurements indicate that the compounds undergo structural transitions at Ts = 151, 109, 87, and 62 K, respectively. The decrease in Ts along with the lanthanoid contraction suggests that the high-temperature phase is more stable for a smaller lattice volume. Analysis of the lattice specific heat of LaOs2Zn20 reveals that the Zn atom at the 16c site encapsulated in the R2Zn12 cage vibrates at a low energy of 3 meV. For CeOs2Zn20, the small magnetic susceptibility with a broad maximum indicates the valence-fluctuating state of the Ce ions. In PrOs2Zn20, the crystalline electric field ground state of the 4f2 state of the Pr3+ ion remains in a non-Kramers doublet at T > Ts, which is lifted by symmetry lowering of the Pr site at T < Ts. Thereby, the quadrupolar degrees of freedom are quenched, avoiding the long-range quadrupole order. PrOs2Zn20 and LaOs2Zn20 exhibit superconducting transitions at 0.06 and 0.07 K, respectively.

  9. Multiple superconducting states induced by pressure in Mo3Sb7

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Yejun; Wang, Yishu; Palmer, A.; Li, Ling; Silevitch, D. M.; Calder, S.; Rosenbaum, T. F.

    2017-03-01

    Tuning competing ordering mechanisms with hydrostatic pressure in the 4 d intermetallic compound Mo 3 Sb 7 reveals an intricate interplay of structure, magnetism, and superconductivity. Synchrotron x-ray diffraction and magnetic susceptibility measurements, both employing diamond anvil cell technologies, link a first-order structural phase transition to a doubling of the superconducting transition temperature. In contrast to the spin-dimer picture for Mo 3 Sb 7 , we deduce from x-ray absorption near-edge structure and dc magnetization measurements at ambient pressure that Mo 3 Sb 7 should possess only very small, itinerant magnetic moments. The pressure evolution of the superconducting transition temperature strongly suggests its enhancement is due to a difference in the phonon density-of-states with changed crystal symmetry.

  10. Structural phase transitions and superconductivity in Fe(1+delta)Se0.57Te0.43 at ambient and elevated pressures.

    Science.gov (United States)

    Gresty, Nathalie C; Takabayashi, Yasuhiro; Ganin, Alexey Y; McDonald, Martin T; Claridge, John B; Giap, Duong; Mizuguchi, Yoshikazu; Takano, Yoshihiko; Kagayama, Tomoko; Ohishi, Yasuo; Takata, Masaki; Rosseinsky, Matthew J; Margadonna, Serena; Prassides, Kosmas

    2009-11-25

    The ternary iron chalcogenide, Fe(1.03)Se(0.57)Te(0.43) is a member of the recently discovered family of Fe-based superconductors with an ambient pressure T(c) of 13.9 K and a simple structure comprising layers of edge-sharing distorted Fe(Se/Te)(4) tetrahedra separated by a van der Waals gap. Here we study the relationship between its structural and electronic responses to the application of pressure. T(c) depends sensitively on applied pressure attaining a broad maximum of 23.3 K at approximately 3 GPa. Further compression to 12 GPa leads to a metallic but nonsuperconducting ground state. High-resolution synchrotron X-ray diffraction shows that the superconducting phase is metrically orthorhombic at ambient pressure but pressurization to approximately 3 GPa leads to a structural transformation to a more distorted structure with monoclinic symmetry. The exact coincidence of the crystal symmetry crossover pressure with that at which T(c) is maximum reveals an intimate link between crystal and electronic structures of the iron chalcogenide superconductors.

  11. Superconducting Properties and Microstructure in MgB2 Bulks, Wires and Tapes

    Institute of Scientific and Technical Information of China (English)

    冯勇; 阎果; 赵勇; 吴晓京; 周廉; 张平祥

    2003-01-01

    We prepared a series of MgB2 bulk samples under different temperatures, holding time and increasing rates in temperature by the solid state reaction. The thermodynamic behavior and phase formation in the Mg-B system were studied by using DTA,XRD and SEM. The results indicate that the formation of the MgB2 phase is very fast and the high increasing rate in temperature is necessary to obtain high quality MgB2. In addition, the effects of the Zr-doping in Mg1-xZrxB2 bulk samples fabricated by the solid state reaction at ambient pressure on phase compositions, microstructure and flux pinning behavior were investigated by using XRD, SQUID magnetometer, SEM and TEM. Critical current density Jc can be significantly enhanced by the Zr-doping and the best data are achieved in Mg0.9Zr0.1B2. For this sample, Jc values are remarkably improved to 1.83×106 A/cm2 in self-field and 5.51×105 A/cm2 in 1 T at 20 K. Also, high quality MgB2/Ta/Cu wires and tapes with and without Ti-doping, MgB2/Fe wires and 18 filament MgB2/NbZr/Cu tapes were fabricated by the powder-in-tube (PIT) method at ambient pressure. The phase compositions, microstructure features and flux pinning properties were studied. The results suggest that Fe is thebest metal for these sheaths. MgB2/Fe wires exhibit very high Jc at high temperatures and high fields. Jc values reach as high as 1.43×105 A/cm2 (4.2 K, 4 T) and 3.72×104 A/cm2 (15 K, 4 T).

  12. Co-existence of superconductivity and ferromagnetism in f-electron metals.

    Science.gov (United States)

    Huxley, Andrew

    2002-03-01

    In itinerant ferromagnets a strong spin polarisation might be expected to suppress any possibility of spin-singlet superconductivity. However spin triplet superconductivity may still occur if there is an appropriate pairing interaction and the material is sufficiently clean. The experimental evidence that a bulk superconducting state is indeed realised in two different f-electron ferromagnets will be reviewed, along with the special factors that might favour such a state. For UGe_2, samples that satisfy the clean limit condition are easily prepared. The superconducting transition temperature is however closely correlated with the proximity to a critical point for a magnetic transition within the ferromagnetic state, which is achieved only at high pressure. The same factors, perhaps related to Fermi surface nesting, which give rise to this complex magnetic behaviour, therefore appear to be implicated in the superconducting pairing. Superconductivity in ferromagnetic URhGe occurs at zero pressure, which has facilitated extensive magnetisation and heat-capacity studies. These confirm both the bulk nature of the two transitions and the co-existence of the two orders (ferromagnetism and superconductivity). Further, as expected for non s-wave pairing, it is found that only samples with a sufficiently low residual resistivity show superconductivity. In contrast to UGe_2, the magnetic state in URhGe behaves in accordance with the simplest version of the Moriya-Lonzarich theory. This, as well as the recent report that that the cubic itinerant ferromagnet ZrZn2 shows a low temperature transition, interpreted as an incomplete transition to superconductivity, suggest that superconductivity could occur more commonly in clean ferromagnets. The observed superconducting properties of UGe2 and URhGe appear to be consistent with a particular symmetry of the order parameter in these lower symmetry materials. Their lower symmetries also lead to several advantages relating to the

  13. Over Current Properties of HTC Superconducting Wire Cooled by Liquid Hydrogen

    Science.gov (United States)

    Shirai, Yasuyuki; Kobayashi, Hiroto; Takegami, Taiki; Hikawa, Kyosuke; Shiotsu, Masahiro; Tatsumoto, Hideki; Naruo, Yoshihiro; Kobayashi, Hiroaki; Inatani, Yoshifumi; Kinoshita, Katsuhiko

    An experimental setup which can energize superconducting wires immersed in LH2 was designed and made. Over current tests were carried out using MgB2 wire. Critical current and resistivity of a test MgB2 wire submerged in liquid hydrogen were measured for exponentially increasing heat input, while the transport current exceeded the critical current. The resistivity of the conductor was obtained as a function of current and the temperature of the conductor by using the transient heating method. The distribution ratio of the current through the superconductor and the sheath, and the resistivity of the MgB2 conductor itself were estimated.

  14. First-principles study of the pressure and crystal-structure dependences of the superconducting transition temperature in compressed sulfur hydrides

    Science.gov (United States)

    Akashi, Ryosuke; Kawamura, Mitsuaki; Tsuneyuki, Shinji; Nomura, Yusuke; Arita, Ryotaro

    2015-06-01

    We calculate the superconducting transition temperatures (Tc) in sulfur hydrides H2S and H3S from first principles using the density functional theory for superconductors. At pressures of ≲150 GPa, the high values of Tc (≥130 K) observed in a recent experiment (A. P. Drozdov, M. I. Eremets, and I. A. Troyan, arXiv:1412.0460) are accurately reproduced by assuming that H2S decomposes into R 3 m H3S and S. For higher pressures, the calculated Tc's for I m 3 ¯m H3S are systematically higher than those for R 3 m H3S and the experimentally observed maximum value (190 K), which suggests the possibility of another higher-Tc phase. We also quantify the isotope effect from first principles and demonstrate that the isotope effect coefficient can be larger than the conventional value (0.5) when multiple structural phases energetically compete.

  15. Structural properties of BeO at high pressure

    Indian Academy of Sciences (India)

    Umesh Kumar Sakalle; Anita Singh; Ekta Sharma

    2014-10-01

    In the present paper, we have investigated the phase transition and elastic properties of BeO at high pressure using three-body potential model (TBPM). The present interaction potential consists of longrange coulomb and three-body interactions and short-range overlap repulsion effective up to second neighbour ions. We have studied the phase transition from wurtzite (4) to rock salt (1) for BeO. The phase transition pressure (t) obtained from this approach shows a respectably good agreement with experimental and other theoretical data. We have also computed the collapse of relative volume changes ( (t)/(0)). Three-body potential model has also been used to derive the correct expressions for third-order elastic constants and pressure derivatives of second-order elastic constants for BeO.

  16. Volumetric properties of sunflower methyl ester oil at high pressure.

    Science.gov (United States)

    Aparicio, Cristina; Guignon, Bérengère; Rodríguez-Antón, Luis M; Sanz, Pedro D

    2007-09-01

    Biodiesel is an alternative to diesel oil (DO), because it is a fuel obtained from renewable resources that has lower emissions than DO. Biomass production should promote agricultural activity to obtain fuels for the transport sector. The study of the behavior of biodiesel at varying pressure and temperature is very interesting because diesel engines are mechanical systems that work with fuels submitted to high pressure. The specific volume, isothermal compressibility, and cubic expansion coefficients of refined sunflower methyl ester oil (SMEO) and unrefined sunflower methyl ester oil (URSMEO) were obtained and compared with those of DO from 0.1 to 350 MPa and 288.15 to 328.15 K. This work shows that oil refinement did not significantly modify any of the properties studied of the final biodiesel. Compared with DO, both SMEOs were about 6% denser, whereas isothermal compressibility and cubic expansion coefficients were bigger or smaller for DO depending on pressure and temperature.

  17. High pressure elasticity and thermal properties of depleted uranium

    Science.gov (United States)

    Jacobsen, M. K.; Velisavljevic, N.

    2016-04-01

    Studies of the phase diagram of uranium have revealed a wealth of high pressure and temperature phases. Under ambient conditions the crystal structure is well defined up to 100 gigapascals (GPa), but very little information on thermal conduction or elasticity is available over this same range. This work has applied ultrasonic interferometry to determine the elasticity, mechanical, and thermal properties of depleted uranium to 4.5 GPa. Results show general strengthening with applied load, including an overall increase in acoustic thermal conductivity. Further implications are discussed within. This work presents the first high pressure studies of the elasticity and thermal properties of depleted uranium metal and the first real-world application of a previously developed containment system for making such measurements.

  18. Structural and superconducting properties of La2−xNdxCuO4+y (0≤x≤0.5) prepared by room temperature chemical oxidation

    DEFF Research Database (Denmark)

    Rial, C.; Morán, E.; Alario-Franco, M.A.;

    1997-01-01

    The systematic characterization of the structural and superconducting properties of room temperature chemically oxidized T/O La2-xNdxCuO4+y (0 less than or equal to x less than or equal to 0.5) has been performed by neutron powder diffraction and magnetic susceptibility measurements. Similarities...

  19. Modeling thermophysical properties of food under high pressure.

    Science.gov (United States)

    Otero, L; Guignon, B; Aparicio, C; Sanz, P D

    2010-04-01

    A set of well-known generic models to predict the thermophysical properties of food from its composition at atmospheric conditions was adapted to work at any pressure. The suitability of the models was assessed using data from the literature for four different food products, namely tomato paste, potato, pork, and cod. When the composition of the product considered was not known, an alternative was proposed if some thermal data at atmospheric conditions were available. Since knowledge on the initial freezing point and ice content of food are essential for the correct prediction of its thermal properties, models for obtaining these properties under pressure were also included. Our results showed that good predictions under pressure, accurate enough for most engineering calculations can be made, either from composition data or using known thermal data of the food considered at atmospheric conditions. All the equations and coefficients needed to construct the models are given throughout the text, thus readers can compose their own routines. However, these routines can also be downloaded free at http://www.if.csic.es/programas/ifiform.htm as executable programs running in Windows.

  20. Superconducting properties of Zn and Al double-doped Mg1-x(Zn0.5Al0.5)xB2

    DEFF Research Database (Denmark)

    Xu, G.J.; Grivel, Jean-Claude; Abrahamsen, A.B.

    2004-01-01

    A series of polycrystalline samples of Mg1-x(Zn0.5Al0.5)(x)B-2 (0less than or equal toxless than or equal to0.8) were prepared by solid state reaction method and their structure, superconducting transition temperature (T-c) and transport properties were investigated by means of X-ray diffraction...... (XRD), ac susceptibility, magnetization and resistivity. The double doping leads to decreases in both the lattice parameters a and c, and the T-c decreases with increasing dopant content. A systematical comparison with Al doped- and Li, Al double doped MgB2 of structure, superconducting transition...

  1. Effect of low temperature annealing on doping level and superconducting properties for IBAD/PLD-YBCO coated conductor

    Energy Technology Data Exchange (ETDEWEB)

    Kato, J.Y. [Superconductivity Research Laboratory, ISTEC, 1-10-13 Shinonome, Koto-ku, Tokyo 135-0062 (Japan)]. E-mail: yoshioka@istec.or.jp; Chikumoto, N. [Superconductivity Research Laboratory, ISTEC, 1-10-13 Shinonome, Koto-ku, Tokyo 135-0062 (Japan); Sakai, N. [Superconductivity Research Laboratory, ISTEC, 1-10-13 Shinonome, Koto-ku, Tokyo 135-0062 (Japan); Iijima, Y. [Fujikura Ltd., 1-5-1 Kiba, Koto-ku, Tokyo 135-8512 (Japan); Kakimoto, K. [Fujikura Ltd., 1-5-1 Kiba, Koto-ku, Tokyo 135-8512 (Japan); Saitoh, T. [Fujikura Ltd., 1-5-1 Kiba, Koto-ku, Tokyo 135-8512 (Japan); Watanabe, T. [Superconductivity Research Laboratory, ISTEC, 2-4-1 Mutsuno, Atsuta-ku, Nagoya, Aichi 456-8587 (Japan); Yamada, Y. [Superconductivity Research Laboratory, ISTEC, 2-4-1 Mutsuno, Atsuta-ku, Nagoya, Aichi 456-8587 (Japan); Tajima, S. [Superconductivity Research Laboratory, ISTEC, 1-10-13 Shinonome, Koto-ku, Tokyo 135-0062 (Japan)

    2005-10-01

    The effect of low temperature annealing on the superconducting properties of PLD-YBCO tape has been investigated with varying atmosphere. The T {sub c} of the as-prepared sample is 88.5 K, for the sample post-annealed at 200 deg. C in Ar atmosphere showed 91.5 K, indicating T {sub c} is sensitive to low temperature annealing. In spite of the higher T {sub c} the J {sub c} and {mu} {sub 0} H {sub irr} for the Ar-annealed sample were lower than those for the as-prepared sample. This indicates that the as-prepared PLD-YBCO tape is in the carrier overdoped state. It was found that re-annealing in which the sample was slowly cooled from 450 deg. C in pure oxygen atmosphere could restore the J {sub c}-degradation, demonstrating that oxygen absorption-release occurred reversely.

  2. Effect of nanowires SiO2 on superconducting properties of YBa2Cu3O7-d bulks

    Science.gov (United States)

    Salem, M. K. Ben; Hannachi, E.; Slimani, Y.; Hamrita, A.; Bessais, L.; Azzouz, F. Ben; Salem, M. Ben

    2013-12-01

    The effects of SiO2 nanowires on the superconducting properties of YBa2Cu3O7-d (YBCO) compound were studied. Samples were synthesized in air using a standard solid state reaction technique by adding nanowires SiO2 up to 1wt.%. Phase analysis by X-ray diffraction (XRD), microstructure investigation by scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDXS), critical current density dependence on applied magnetic field Jc(H) and electrical resistivity as a function of temperature ρ(T) were carried out to evaluate the relative performance of samples. We find that Tco does not change much (90.8-90.2 K) with the low concentration of SiO2 (≤ 0.1 wt.%) and Jc(H) is enhanced.

  3. Sintering time dependence of iron diffusion in MgB2 and its effect on superconducting properties

    Science.gov (United States)

    Ulgen, Asaf Tolga; Belenli, Ibrahim

    2017-02-01

    We have investigated the effects of the iron diffusion on the crystal structure and superconducting properties of pelletised magnesium diboride (MgB2) bulk samples employing X-ray diffraction (XRD), critical transition temperature, and room temperature resistivity measurements. The Fe diffusion into MgB2 bulk pellets upon sintering at 900°C has been studied for sintering time durations of 15 minutes, 30 minutes, 1 hour, 2 hours, and 4 hours. We have carried out XRD and room temperature resistivity determinations along the depth starting from iron coated surface by successive removal of thin layers from the surface mechanically. Sintering time dependence of the Fe diffusion coefficients has been calculated from depth profiles of lattice parameter c and room temperature resistivity values. It has been found that the Fe diffusion coefficient decreases with increasing sintering time.

  4. Effects of α-particle beam irradiation on superconducting properties of thin film MgB2 superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sang Bum; Duong, Pham van; Ha, Dong Hyup; Oh, Young Hoon; Kang, Won Nam; Chai, Jong Seo [Sungkunkwan Univeversity, Suwon (Korea, Republic of); Hong, Seung Pyo; Kim, Ran Young [Kore Institute of Radiological and Medical Science, Seoul (Korea, Republic of)

    2016-06-15

    Superconducting properties of thin film MgB2 superconductors irradiated with 45 MeV α-particle beam were studied. After the irradiation, enhancement of the critical current density and pinning force was observed, scaling close to strong pinning formula. Double logarithmic plots of the maximum pinning force density with irreversible magnetic field show a power law behavior close to carbon-doped MgB2 film or polycrystals. Variation of normalized pinning force density in the reduced magnetic field suggests scaling formulas for strong pinning mechanism like planar defects. We also observed a rapid decay of critical current density as the vortex lattice constant decreases, due to the strong interaction between vortices and increasing magnetic field.

  5. Effect of pressure on the physical properties of magnetorheological fluids

    Directory of Open Access Journals (Sweden)

    A. Spaggiari

    2013-01-01

    Full Text Available To date, several applications of magnetorheological (MR fluids are present in the industrial world, nonetheless system requirements often needs better material properties. In technical literature a previous work shows that MR fluids exhibit a pressure dependency called squeeze strengthen effect. Since a lot of MR fluid based devices are rotary devices, this paper investigates the behaviour of MR fluids under pressure when a rotation is applied to shear the fluid. The system is designed in order to apply both the magnetic field and the pressure and follows a Design of Experiment approach. The experimental apparatus comprises a cylinder in which a piston is used both to apply the pressure and to shear the fluid. The magnetic circuit is designed to provide a nearly constant induction field in the MR fluid. The experimental apparatus measures the torque as a function of the variables considered and the yield shear stress is computed. The analysis of the results shows that there is a positive interaction between magnetic field and pressure, which enhances the MR fluid performances more than twice.

  6. Superconducting transistor

    Science.gov (United States)

    Gray, Kenneth E.

    1979-01-01

    A superconducting transistor is formed by disposing three thin films of superconducting material in a planar parallel arrangement and insulating the films from each other by layers of insulating oxides to form two tunnel junctions. One junction is biased above twice the superconducting energy gap and the other is biased at less than twice the superconducting energy gap. Injection of quasiparticles into the center film by one junction provides a current gain in the second junction.

  7. Superconductivity in highly disordered dense carbon disulfide.

    Science.gov (United States)

    Dias, Ranga P; Yoo, Choong-Shik; Struzhkin, Viktor V; Kim, Minseob; Muramatsu, Takaki; Matsuoka, Takahiro; Ohishi, Yasuo; Sinogeikin, Stanislav

    2013-07-16

    High pressure plays an increasingly important role in both understanding superconductivity and the development of new superconducting materials. New superconductors were found in metallic and metal oxide systems at high pressure. However, because of the filled close-shell configuration, the superconductivity in molecular systems has been limited to charge-transferred salts and metal-doped carbon species with relatively low superconducting transition temperatures. Here, we report the low-temperature superconducting phase observed in diamagnetic carbon disulfide under high pressure. The superconductivity arises from a highly disordered extended state (CS4 phase or phase III[CS4]) at ~6.2 K over a broad pressure range from 50 to 172 GPa. Based on the X-ray scattering data, we suggest that the local structural change from a tetrahedral to an octahedral configuration is responsible for the observed superconductivity.

  8. Anelastic characterization and superconducting properties of RuSr2GdCu2O8+δ

    Directory of Open Access Journals (Sweden)

    Jurelo, A. R.

    2008-08-01

    Full Text Available Since the discovery of the high Tc superconductors, many researches have been carried out on the different properties of these materials, especially on the transition temperature into the superconducting state. The rutheno-cuprates belong to a new class of composites, which were synthesized for the first time by Bauernfeind in 1995. Bernhard and collaborators discovered, in 1999, the coexistence of the ferromagnetism and the superconductivity in this phase, which is known as antagonistic phenomenon in the electromagnetism due to spin-charge interactions established in these states. However, the physical nature of the superconducting and magnetic states is still very obscure. The non-stoichiometric (interstitial oxygen is considered as a possible cause for the non-uniformity of the sample properties. In this paper, results of mechanical spectroscopy in Ru-1212 samples are presented showing complex anelastic spectra, which were attributed to the mobility of the interstitial oxygen atoms in the Ru-1212 lattice.Desde el descubrimiento de los superconductores de alta Tc, muchas investigaciones han sido realizadas sobre las diferentes propiedades de estos materiales, especialmente sobre la temperatura de transición dentro del estado superconductor. Los cupratos de rutenio pertenecen a una nueva clase de compositos, los cuales fueron sintetizados por primera vez por Bauernfeind en 1995. Bernhard y colaboradores descubrieron, en 1999, la coexistencia del ferromagnetismo y la superconductividad en esta fase, lo cual es conocido como un fenómeno antagonistico en el electromagnetismo debido a las interacciones spin-carga establecidas en estos estados. Sin embargo, la naturaleza física de los estados superconductores y magnéticos aun no son muy claros. El oxigeno no-estequiométrico (intersticial es considerado como una causa de la no-uniformidad de las propiedades de la muestra. En este articulo, los resultados de espectroscopia mecánica en muestras

  9. High-pressure synthesis and properties of the Eu-substituted Ba{sub 8−x}Eu{sub x}Si{sub 46} clathrates

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Lihua; Song, Bensheng [Department of Physics, University of Science and Technology Beijing, Beijing 100083 (China); Sun, Bing; Ma, Hongan [National Key Lab of Superhard Materials, Jilin University, Changchun 130012 (China); Ma, Xingqiao [Department of Physics, University of Science and Technology Beijing, Beijing 100083 (China); Li, Yang, E-mail: ylibp@hotmail.com [Department of Engineering Science and Materials, University of Puerto Rico at Mayaguez, Mayaguez, PR 00681-9044 (United States)

    2016-03-15

    There has been considerable interest in rare-earth doped silicon clathrate compounds in order to understand the relation between the 4f electron moment and superconductivity. The Eu-doped silicon clathrates Ba{sub 8−x}Eu{sub x}Si{sub 46} (x=0, 0.5 and 1) were synthesized by using high-temperature and high-pressure. Structure characterization and magnetic measurement show Eu atoms enter clathrate lattice to occupy Ba positions. X-ray powder diffraction data indicate that the cubic lattice parameter a decreases with Eu doping. The magnetic measurements for all samples were studied. The incorporation of magnetic Eu{sup 2+} into the lattice suppresses the superconductivity completely and induces the Curie-paramagnetic behavior at high temperature. The influences of Eu{sup 2+} magnetic moment on the properties of samples were discussed.

  10. Superconductivity in aromatic hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Kubozono, Yoshihiro, E-mail: kubozono@cc.okayama-u.ac.jp [Research Laboratory for Surface Science, Okayama University, Okayama 700-8530 (Japan); Research Center of New Functional Materials for Energy Production, Storage and Transport, Okayama University, Okayama 700-8530 (Japan); Japan Science and Technology Agency, ACT-C, Kawaguchi 332-0012 (Japan); Goto, Hidenori; Jabuchi, Taihei [Research Laboratory for Surface Science, Okayama University, Okayama 700-8530 (Japan); Yokoya, Takayoshi [Research Laboratory for Surface Science, Okayama University, Okayama 700-8530 (Japan); Research Center of New Functional Materials for Energy Production, Storage and Transport, Okayama University, Okayama 700-8530 (Japan); Kambe, Takashi [Department of Physics, Okayama University, Okayama 700-8530 (Japan); Sakai, Yusuke; Izumi, Masanari; Zheng, Lu; Hamao, Shino; Nguyen, Huyen L.T. [Research Laboratory for Surface Science, Okayama University, Okayama 700-8530 (Japan); Sakata, Masafumi; Kagayama, Tomoko; Shimizu, Katsuya [Center of Science and Technology under Extreme Conditions, Osaka University, Osaka 560-8531 (Japan)

    2015-07-15

    Highlights: • Aromatic superconductor is one of core research subjects in superconductivity. Superconductivity is observed in certain metal-doped aromatic hydrocarbons. Some serious problems to be solved exist for future advancement of the research. This article shows the present status of aromatic superconductors. - Abstract: ‘Aromatic hydrocarbon’ implies an organic molecule that satisfies the (4n + 2) π-electron rule and consists of benzene rings. Doping solid aromatic hydrocarbons with metals provides the superconductivity. The first discovery of such superconductivity was made for K-doped picene (K{sub x}picene, five benzene rings). Its superconducting transition temperatures (T{sub c}’s) were 7 and 18 K. Recently, we found a new superconducting K{sub x}picene phase with a T{sub c} as high as 14 K, so we now know that K{sub x}picene possesses multiple superconducting phases. Besides K{sub x}picene, we discovered new superconductors such as Rb{sub x}picene and Ca{sub x}picene. A most serious problem is that the shielding fraction is ⩽15% for K{sub x}picene and Rb{sub x}picene, and it is often ∼1% for other superconductors. Such low shielding fractions have made it difficult to determine the crystal structures of superconducting phases. Nevertheless, many research groups have expended a great deal of effort to make high quality hydrocarbon superconductors in the five years since the discovery of hydrocarbon superconductivity. At the present stage, superconductivity is observed in certain metal-doped aromatic hydrocarbons (picene, phenanthrene and dibenzopentacene), but the shielding fraction remains stubbornly low. The highest priority research area is to prepare aromatic superconductors with a high superconducting volume-fraction. Despite these difficulties, aromatic superconductivity is still a core research target and presents interesting and potentially breakthrough challenges, such as the positive pressure dependence of T{sub c} that is clearly

  11. Superconductivity in CVD diamond films.

    Science.gov (United States)

    Takano, Yoshihiko

    2009-06-24

    A beautiful jewel of diamond is insulator. However, boron doping can induce semiconductive, metallic and superconducting properties in diamond. When the boron concentration is tuned over 3 × 10(20) cm(-3), diamonds enter the metallic region and show superconductivity at low temperatures. The metal-insulator transition and superconductivity are analyzed using ARPES, XAS, NMR, IXS, transport and magnetic measurements and so on. This review elucidates the physical properties and mechanism of diamond superconductor as a special superconductivity that occurs in semiconductors.

  12. Optical properties of c-axis oriented superconducting MgB2 films.

    Science.gov (United States)

    Tu, J J; Carr, G L; Perebeinos, V; Homes, C C; Strongin, M; Allen, P B; Kang, W N; Choi, E M; Kim, H J; Lee, S I

    2001-12-31

    Temperature dependent optical conductivities and dc resistivity of c-axis oriented superconducting (T(c) = 39.6 K) MgB2 films (approximately 450 nm) have been measured. The normal state ab-plane optical conductivities can be described by the Drude model with a temperature independent Drude plasma frequency of omega(p,D) = 13 600+/-100 cm(-1) or 1.68+/-0.01 eV. The normal state resistivity is fitted by the Bloch-Grüneisen formula with an electron-phonon coupling constant lambda(tr) = 0.13+/-0.02. The optical conductivity spectra below T(c) of these films suggest that MgB2 is a multigap superconductor.

  13. Influence of filament diameter on superconducting properties of MgB2 multi-core wires

    Science.gov (United States)

    Reissner, M.; Bulla, L.; Husek, I.; Melišek, T.; Kováč, P.

    2013-06-01

    Magnetic behaviour of a series of MgB2 wires, in each case with 19 filaments of superconductor, surrounded by Ti as barrier and reinforced by stainless steel, prepared in the same way but mechanically deformed to different filament diameters ϕ between 58.5 and 17.7 µm, was investigated. Whereas no influence of ϕ on superconducting transition temperature is found, the width of the transition increases with ϕ. Critical current density, irreversibility line and mean effective activation energy U decrease systematically with decreasing ϕ. From a comparison of the field dependence of the pinning force and the temperature dependence of U, it is concluded, that pinning is dominated at low fields by grain boundary pinning and at higher fields by point defect pinning, with a rather broad distribution of pinning energies.

  14. Properties of pseudospin polarization on a graphene-based spin singlet superconducting junction

    Institute of Scientific and Technical Information of China (English)

    Jia Shuan-Wen; Wang Jun-Tao; Yang Yan-Ling; Bai Chun-Xu

    2013-01-01

    We investigate theoretically transport characteristics in a graphene-based pseudospinmagnet/superconductor junction,including the s-wave and the d-wave pairing symmetry potential in the superconducting region.It is found that the pseudospin polarization,in sharp contrast to spin polarization in the graphene-based ferromagnet/superconductor junction,holds no influence on the specular Andreev reflection for a negligible Fermi energy.Furthermore,the Fano factor is crucially affected by the zero bias state.Therefore,we suggest here that the findings could shed light on the realization of graphene-based pseudospintronics devices and provide a new way to detect the specular Andreev reflection and the zero bias state in the actual experiments.

  15. Structure of haloform intercalated C60 and its influence on superconductive properties.

    Science.gov (United States)

    Dinnebier, Robert E; Gunnarsson, Olle; Brumm, Holger; Koch, Erik; Stephens, Peter W; Huq, Ashfia; Jansen, Martin

    2002-04-05

    CHCl3 and CHBr3 intercalated C60 have attracted particular interest after a superconductivity transition temperature (Tc) of up to 117 K was discovered. We have determined the structure using synchrotron x-ray powder-diffraction and found that the expansion of the lattice mainly takes place in one dimension (triclinic b axis), leaving planes of C60 molecules on an approximately hexagonal, slightly expanded lattice. We have performed tight-binding band structure calculations for the surface layer. In spite of the slight expansion of the layers, for the range of dopings where a large Tc has been observed, the density of states at the Fermi energy is smaller for C60.2CHCl3 and C60.2CHBr3 than for C60. This suggests that the lattice expansion alone cannot explain the increase of Tc.

  16. Nb3Sn superconducting radiofrequency cavities: fabrication, results, properties, and prospects

    Science.gov (United States)

    Posen, S.; Hall, D. L.

    2017-03-01

    A microns-thick film of Nb3Sn on the inner surface of a superconducting radiofrequency (SRF) cavity has been demonstrated to substantially improve cryogenic efficiency compared to the standard niobium material, and its predicted superheating field is approximately twice as high. We review in detail the advantages of Nb3Sn coatings for SRF cavities. We describe the vapor diffusion process used to fabricate this material in the most successful experiments, and we compare the differences in the process used at different labs. We overview results of Nb3Sn SRF coatings, including CW and pulsed measurements of cavities as well as microscopic measurements. We discuss special considerations that must be practised when using Nb3Sn cavities in applications. Finally, we conclude by summarizing the state-of-the-art and describing the outlook for this alternative SRF material.

  17. Electrical transport properties of manganite powders under pressure

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez, M.G. [Laboratorio de Bajas Temperaturas, Departamento de Fisica, FCEyN, UBA, and IFIBA (CONICET), Ciudad Universitaria, (C1428EHA) Buenos Aires (Argentina); Leyva, A.G. [Gerencia de Investigacion y Aplicaciones, CAC, Comision Nacional de Energia Atomica, Gral Paz 1499, 1650 San Martin, Buenos Aires (Argentina); Acha, C., E-mail: acha@df.uba.ar [Laboratorio de Bajas Temperaturas, Departamento de Fisica, FCEyN, UBA, and IFIBA (CONICET), Ciudad Universitaria, (C1428EHA) Buenos Aires (Argentina)

    2012-08-15

    We have measured the electrical resistance of micrometric to nanometric powders of the La{sub 5/8-y}Pr{sub y}Ca{sub 3/8}MnO{sub 3} (LPCMO with y=0.3) manganite for hydrostatic pressures up to 4 kbar. By applying different final thermal treatments to samples synthesized by a microwave assisted denitration process, we obtained two particular grain characteristic dimensions (40 nm and 1000 nm) which allowed us to analyze the grain size sensitivity of the electrical conduction properties of both the metal electrode interface with manganite (Pt/LPCMO) and the intrinsic intergranular interfaces formed by the LPCMO powder, conglomerate under the only effect of external pressure. We also analyzed the effects of pressure on the phase diagram of these powders. Our results indicate that different magnetic phases coexist at low temperatures and that the electrical transport properties are related to the intrinsic interfaces, as we observe evidences of a granular behavior and an electronic transport dominated by the Space Charge limited Current mechanism.

  18. High Temperature Superconductivity at High Pressures for H3 Six P(1 - x) , H3 Px S(1 - x) and H3 Clx S(1 - x)

    Science.gov (United States)

    Papaconstantopoulos, Dimitrios; Fan, Fudong; Mehl, Michael

    Recent experimental and computational works have established the occurrence of superconducting temperatures,Tc, around 200K at corresponding 200GPa pressures in hydrogen-based sulfur compounds. In this work we have investigated the effects of phosphorus and chlorine substitutions of sulfur on Tc, as well as the effect of hydrogen vacancies. In addition, we have explored the superconductivity-relevant parameters in the H3SixP(1-x) system. In executing this work we have used the virtual-crystal-approximation and performed a systematic set of LAPW calculations for many different concentrations of the sulfur component. From the densities of states and the scattering phase-shifts at the Fermi level, we calculated electron-ion matrix elements and estimated the electron-phonon coupling constants for different concentrations as well as Tc. We find that the high values of Tc correlate with the position of the Fermi level with respect to peaks(van Hove singularities) in the density of electronic states of these materials. US Department of Energy.

  19. Experimental Investigation of Magnetic, Superconducting, and other Phase Transitions in novel F-Electron Materials at Ultra-high Pressures - Final Progress Report

    Energy Technology Data Exchange (ETDEWEB)

    Maple, Brian; Jeffires, Jason

    2006-07-28

    This grant, entitled “Experimental investigation of magnetic, superconducting and other phase transitions in novel f-electron materials at ultrahigh pressures,” spanned the funding period from May 1st, 2003 until April 30th, 2006. The major goal of this grant was to develop and utilize an ultrahigh pressure facility—capable of achieving very low temperatures, high magnetic fields, and extreme pressures as well as providing electrical resistivity, ac susceptibility, and magnetization measurement capabilities under pressure—for the exploration of magnetic, electronic, and structural phases and any corresponding interactions between these states in novel f-electron materials. Realizing this goal required the acquisition, development, fabrication, and implementation of essential equipment, apparatuses, and techniques. The following sections of this report detail the establishment of an ultrahigh pressure facility (Section 1) and measurements performed during the funding period (Section 2), as well as summarize the research project (Section 3), project participants and their levels of support (Section 4), and publications and presentations (Section 5).

  20. Electronic structure and superconductivity of FeSe-related superconductors.

    Science.gov (United States)

    Liu, Xu; Zhao, Lin; He, Shaolong; He, Junfeng; Liu, Defa; Mou, Daixiang; Shen, Bing; Hu, Yong; Huang, Jianwei; Zhou, X J

    2015-05-13

    FeSe superconductors and their related systems have attracted much attention in the study of iron-based superconductors owing to their simple crystal structure and peculiar electronic and physical properties. The bulk FeSe superconductor has a superconducting transition temperature (Tc) of ~8 K and it can be dramatically enhanced to 37 K at high pressure. On the other hand, its cousin system, FeTe, possesses a unique antiferromagnetic ground state but is non-superconducting. Substitution of Se with Te in the FeSe superconductor results in an enhancement of Tc up to 14.5 K and superconductivity can persist over a large composition range in the Fe(Se,Te) system. Intercalation of the FeSe superconductor leads to the discovery of the AxFe2-ySe2 (A = K, Cs and Tl) system that exhibits a Tc higher than 30 K and a unique electronic structure of the superconducting phase. A recent report of possible high temperature superconductivity in single-layer FeSe/SrTiO3 films with a Tc above 65 K has generated much excitement in the community. This pioneering work opens a door for interface superconductivity to explore for high Tc superconductors. The distinct electronic structure and superconducting gap, layer-dependent behavior and insulator-superconductor transition of the FeSe/SrTiO3 films provide critical information in understanding the superconductivity mechanism of iron-based superconductors. In this paper, we present a brief review of the investigation of the electronic structure and superconductivity of the FeSe superconductor and related systems, with a particular focus on the FeSe films.

  1. Superconductivity in graphite intercalation compounds

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Robert P. [Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge CB3 0HE (United Kingdom); Weller, Thomas E.; Howard, Christopher A. [Department of Physics & Astronomy, University College of London, Gower Street, London WCIE 6BT (United Kingdom); Dean, Mark P.M. [Department of Condensed Matter Physics and Materials Science, Brookhaven National Laboratory, Upton, NY 11973 (United States); Rahnejat, Kaveh C. [Department of Physics & Astronomy, University College of London, Gower Street, London WCIE 6BT (United Kingdom); Saxena, Siddharth S. [Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge CB3 0HE (United Kingdom); Ellerby, Mark, E-mail: mark.ellerby@ucl.ac.uk [Department of Physics & Astronomy, University College of London, Gower Street, London WCIE 6BT (United Kingdom)

    2015-07-15

    Highlights: • Historical background of graphite intercalates. • Superconductivity in graphite intercalates and its place in the field of superconductivity. • Recent developments. • Relevant modeling of superconductivity in graphite intercalates. • Interpretations that pertain and questions that remain. - Abstract: The field of superconductivity in the class of materials known as graphite intercalation compounds has a history dating back to the 1960s (Dresselhaus and Dresselhaus, 1981; Enoki et al., 2003). This paper recontextualizes the field in light of the discovery of superconductivity in CaC{sub 6} and YbC{sub 6} in 2005. In what follows, we outline the crystal structure and electronic structure of these and related compounds. We go on to experiments addressing the superconducting energy gap, lattice dynamics, pressure dependence, and how these relate to theoretical studies. The bulk of the evidence strongly supports a BCS superconducting state. However, important questions remain regarding which electronic states and phonon modes are most important for superconductivity, and whether current theoretical techniques can fully describe the dependence of the superconducting transition temperature on pressure and chemical composition.

  2. Pressure-induced superconductivity and structural transitions in Ba(Fe0.9Ru0.1)2As2

    Science.gov (United States)

    Uhoya, Walter O.; Tsoi, Georgiy M.; Vohra, Yogesh K.; Sefat, Athena S.; Weir, Samuel T.

    2014-03-01

    Electrical transport and structural characterizations of isoelectronically substituted Ba(Fe0.9Ru0.1)2As2 have been performed as a function of pressure up to ~30 GPa and temperature down to ~10 K using designer diamond anvil cell. Similar to undoped members of the AFe2As2 (A = Ca, Sr, Ba) family, Ba(Fe0.9Ru0.1)2As2 shows anomalous a-lattice parameter expansion with increasing pressure and a concurrent ThCr2Si2 type isostructural (I4/mmm) phase transition from tetragonal (T) phase to a collapsed tetragonal (cT) phase occurring between 12 and 17 GPa where the a is maximum. Above 17 GPa, the material remains in the cT phase up to 30 GPa at 200 K. The resistance measurements show evidence of pressure-induced zero resistance that may be indicative of high-temperature superconductivity for pressures above 3.9 GPa. The onset of the resistive transition temperature decreases gradually with increasing pressure before completely disappearing for pressures above ~10.6 GPa near the T-cT transition. We have determined the crystal structure of the high-Tc phase of Ru-doped BaFe2As2 to remain as tetragonal (I4/mmm) by analyzing the X-ray diffraction pattern obtained at 10 K and 9.7 ± 0.7 GPa, as opposed to inferring the structural transition from electrical resistance measurement, as in a previous report [S.K. Kim, M.S. Torikachvili, E. Colombier, A. Thaler, S.L. Bud'ko, P.C. Canfield, Phys. Rev. B 84, 134525 (2011)].

  3. Superconducting wind turbine generators

    DEFF Research Database (Denmark)

    Abrahamsen, Asger Bech; Mijatovic, Nenad; Seiler, Eugen

    2010-01-01

    , the main challenge of the superconducting direct drive technology is to prove that the reliability is superior to the alternative drive trains based on gearboxes or permanent magnets. A strategy of successive testing of superconducting direct drive trains in real wind turbines of 10 kW, 100 kW, 1 MW and 10...... offshore turbines of 8 and 10 MW have been determined from an up-scaling of an existing 5 MW turbine and the necessary properties of the superconducting drive train are discussed. We have found that the absence of the gear box is the main benefit and the reduced weight and size is secondary. However...... MW generator and it is concluded that the present production capacity of coated conductors must be increased by a factor of 36 by 2020, resulting in a ten times lower price of the tape in order to reach a realistic price level for the superconducting drive train....

  4. Effect of nonmagnetic defects on superconducting and transport properties of Ba(Fe{sub 1–x}Co{sub x}As){sub 2} high-T{sub c} superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Blokhin, I. S.; Gavrilkin, S. Yu. [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation); Gorshunov, B. P. [Russian Academy of Sciences, Prokhorov General Physics Institute (Russian Federation); Dravin, V. A. [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation); Zhukova, E. S. [Russian Academy of Sciences, Prokhorov General Physics Institute (Russian Federation); Ivanenko, O. M. [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation); Aida, K. [Leibniz Institute for Solid State and Materials Research (Germany); Krasnosvobodtsev, S. I. [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation); Kurt, F. [Leibniz Institute for Solid State and Materials Research (Germany); Mitsen, K. V., E-mail: mitsen@sci.lebedev.ru; Tsvetkov, A. Yu. [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation)

    2015-11-15

    The effect of nonmagnetic defects on superconducting and transport properties of Ba(Fe{sub 0.94}Co{sub 0.06}As){sub 2} films is studied for obtaining information on the symmetry type of the order parameter for superconducting pnictides. Such defects are generated in the film by irradiation by He{sup +} ions with an energy of 200 keV. It is found that a decrease in superconducting transition temperature T{sub c} upon an increase in the concentration of nonmagnetic defects in this compound occurs much more slowly than predicted in the model assuming s{sup ±}-wave symmetry of the order parameter. Joint analysis of the influence of nonmagnetic defects on the superconducting and magnetotransport properties of such films leads to the conclusion that superconductivity is completely suppressed in them after critical disorder is attained, which assumes the s{sup ++}-wave symmetry.

  5. Transport properties and anisotropy of superconducting (Li1-x Fe x )OHFeSe single crystals

    Science.gov (United States)

    Wang, Chunlei; Yi, Xiaolei; Qiu, Yang; Tang, Qingbin; Zhang, Xinwei; Luo, Yongsong; Yu, Benhai

    2016-05-01

    Large size single crystals of (Li1-x Fe x )OHFeSe have been synthesized via a hydrothermal ion-exchange technique using K0.8Fe2Se2 single crystals as the main raw material. The onset superconducting transition temperature is up to 40.3 K. The critical current density is as large as 1.9 × 105 A cm-2 at 5 K and self field. The upper critical fields have been determined by analyzing the relationship between resistivity and temperature under different applied fields along c-axis and ab-plane, respectively. An anisotropic factor about 11 is obtained, which is further confirmed by fitting the data obtained from the angle-dependent resistivity according to the anisotropic Ginzburg-Landau theory. The flux pinning potential (U 0/k B) is as large as 6429 and 3115 K at 0.1 T in H//ab and H//c orientation, respectively. However, the flux pinning potentials are very sensitive to the applied magnetic field and will fast decrease with increase of the magnetic field in both directions, which are obviously different from the Ba1-x K x Fe2As2 superconductor indicating a different flux pinning mechanism in the two kinds of superconductors.

  6. Phase Diagram and Electronic Properties of High-Tc Superconducting Oxides

    Science.gov (United States)

    Pavuna, Davor

    We firstly briefly summarize some of the most relevant recent results and open questions across rather complex electronic phase diagram of cuprates. We continue with a discussion of results on thin superconducting oxide films grown by laser ablation. Systematic studies show that BSCCO-phases and LSCO-214 exhibit conductor-like Fermi edge, whereas materials containing "chains" (like YBCO-123) are prone to very rapid surface degradation, most likely related to critical oxygen loss at the outermost layers. Recently, direct ARPES dispersion measurements on in-situ grown, strained 10UC thin LSCO-214 films (Tc = 44 K) have shown the band crossing of Fermi level well before the Brillouin zone boundary. This is in contrast to the flat band observed in unstrained single crystals — and to the band flattening predicted by band calculations for in-plane compressive strain. In spite of density of states reduction near the Fermi level, the critical temperature increases in strained films with respect to unstrained crystals; this poses further challenge to HTSC theory.

  7. Thermodynamic Properties of Fast Ramped Superconducting Accelerator Magnets for the Fair Project

    Science.gov (United States)

    Fischer, E.; Mierau, A.; Schnizer, P.; Bleile, A.; Gärtner, W.; Guymenuk, O.; Khodzhibagiyan, H.; Schroeder, C.; Sikler, G.; Stafiniak, A.

    2010-04-01

    The 100 Tm synchrotron SIS 100 is the core component of the international Facility of Antiproton and Ion Research (FAIR) to be built at GSI Darmstadt. The 108 bending magnets are 3 m long 2 T superferric dipoles providing a nominal ramp rate of 4 T/s within a usable aperture of 115 mmṡ60 mm. An intensive R&D period was conducted to minimise the AC losses to lower operation costs and to guarantee a safe thermal stability for long term continuous cycling with a maximum repetition frequency of 1 Hz. The latter requirement is strictly limited by the overall heat flow originated by eddy currents and hysteresis losses in iron yoke and coil as well as by its hydraulic resistance respective to the forced two phase helium cooling flow within the hollow superconducting cable. Recently three full size dipoles—and one quadrupole magnets were built and intensive tests have been started in the end of 2008 at the GSI cryogenic test facility. We present the measured thermodynamic parameters of the first tested dipole: AC losses depending on Bmax and dB/dt for various characteristic ramping modes and conclude for necessary optimisations toward the final design of the series magnets.

  8. Detailed magnetization study of superconducting properties of YBa2Cu3O7-x ceramic spheres

    Science.gov (United States)

    Landau, I. L.; Willems, J. B.; Hulliger, J.

    2008-03-01

    We present a magnetization study of low density YBa2Cu3O7-x ceramics carried out in magnetic fields H such that 0.5 Oe85 K, using low field magnetization measurements, we were able to evaluate the temperature dependence of λ, which turned out to be very close to predictions from conventional Ginzburg-Landau theory. Although the present samples consisted of randomly oriented grains, specifics of magnetization measurements allowed for evaluation of λab(T). Good agreement between our estimation of the grain size and the real sample structure provides evidence for the validity of this analysis of magnetization data. Measurements of the equilibrium magnetization in high magnetic fields were used for evaluation of Hc2(T). At temperatures close to Tc, the Hc2(T) dependence turned out to be linear, in agreement with Ginzburg-Landau theory. The value of the temperature at which Hc2 vanishes coincides with the superconducting critical temperature evaluated from low field measurements, which is important evidence of the validity of both approaches to the analysis of magnetization data.

  9. Applications of Superconductivity

    Science.gov (United States)

    Goodkind, John M.

    1971-01-01

    Presents a general review of current practical applications of the properties of superconducters. The devices are classified into groups according to the property that is of primary importance. The article is inteded as a first introduction for students and professionals. (Author/DS)

  10. Enhancement of superconductivity near the pressure-induced semiconductor-metal transition in the BiS₂-based superconductors LnO₀.₅F₀.₅BiS₂ (Ln = La, Ce, Pr, Nd).

    Science.gov (United States)

    Wolowiec, C T; White, B D; Jeon, I; Yazici, D; Huang, K; Maple, M B

    2013-10-23

    Measurements of electrical resistivity were performed between 3 and 300 K at various pressures up to 2.8 GPa on the BiS2-based superconductors LnO0.5F0.5BiS2 (Ln=Pr, Nd). At lower pressures, PrO0.5F0.5BiS2 and NdO0.5F0.5BiS2 exhibit superconductivity with critical temperatures Tc of 3.5 and 3.9 K, respectively. As pressure is increased, both compounds undergo a transition at a pressure Pt from a low Tc superconducting phase to a high Tc superconducting phase in which Tc reaches maximum values of 7.6 and 6.4 K for PrO0.5F0.5BiS2 and NdO0.5F0.5BiS2, respectively. The pressure-induced transition is characterized by a rapid increase in Tc within a small range in pressure of ∼0.3 GPa for both compounds. In the normal state of PrO0.5F0.5BiS2, the transition pressure Pt correlates with the pressure where the suppression of semiconducting behaviour saturates. In the normal state of NdO0.5F0.5BiS2, Pt is coincident with a semiconductor-metal transition. This behaviour is similar to the results recently reported for the LnO0.5F0.5BiS2 (Ln=La, Ce) compounds. We observe that Pt and the size of the jump in Tc between the two superconducting phases both scale with the lanthanide element in LnO0.5F0.5BiS2 (Ln=La, Ce, Pr, Nd).

  11. Magnetic and mechanical properties of a finite-thickness superconducting strip with a cavity in oblique magnetic fields

    Science.gov (United States)

    Huang, Chen-Guang; Liu, Jun

    2017-01-01

    This paper presents an investigation of the mechanical response of a finite-thickness superconducting strip containing an elliptical cavity in oblique magnetic fields. After the Bean critical state model and the minimum magnetic energy variation procedure are employed, the dependency of the magnetic and mechanical properties on the aspect ratio of the strip and the tilt angles of the applied field and elliptical cavity is discussed. The results show that for a strip in an oblique magnetic field, the current front penetrates non-monotonically from the surface inwards in the initial stage. The magnetization of the strip and the applied field are not collinear, and the angle between them becomes smaller with increasing field. Simultaneously, the strip suffers from a torque produced by the electromagnetic force and then has a tendency to rotate. Compared with the defect-free case, the appearance of the elliptical cavity affects the magnetic property of the strip and further causes significant stress concentration. If the tilt angle of the elliptical cavity is small, a position of stable mechanical equilibrium will exist for the strip. It is interesting that due to the elliptical cavity effect, an oblique magnetization and a non-zero torque are generated even if the applied field is perpendicular or parallel to the strip.

  12. Studies of selected properties of high-temperature superconducting tape 2G HTS SF series - the example: tape SF12050

    Directory of Open Access Journals (Sweden)

    J. Jędryka

    2013-12-01

    Full Text Available Purpose: In presented paper were characterized selected properties of high-temperature superconducting tape 2G HTS SF series - the example of the tape SF12050. Design/methodology/approach: As part of the study smples of tape SF12050 were made. At first made to measure of chemical compsition and compared with manufacturer’s information about that kind of tape. Second step of researcher were research about adhesion of the individual layers of SF12050. After then research was made about tensile strengtht what is the justification utility, as these tapes are subjected to tension at the time of their formation and winding on the transformer core. Findings: As a result of research obtained information on the chemical composition, scratch resistance, adhesion of coating on the tape and about tensile strength. On the last step studies were conducted about critical currents - Ic. Research limitations/implications: These results allow to identify the suitability of these tapes for use on a wide scale - in particular, the winding of the transformer cores. Originality/value: On the basis of studies have demonstrated applications for which the tape may be used SF12050. Given its properties – scratch resistance and tensile strenght reistance, and information about critical current, was indicated best use of that tape for trnasformers production.

  13. Magnetic response of superconducting mesoscopic-size YBCO powder

    Energy Technology Data Exchange (ETDEWEB)

    Deimling, C.V. [Grupo de Supercondutividade e Magnetismo, Departamento de Fisica, Universidade Federal de Sao Carlos, Sao Carlos, SP (Brazil)], E-mail: cesard@df.ufscar.br; Motta, M.; Lisboa-Filho, P.N. [Laboratorio de Materiais Supercondutores, Departamento de Fisica, Universidade Estadual Paulista, Bauru, SP Brazil (Brazil); Ortiz, W.A. [Grupo de Supercondutividade e Magnetismo, Departamento de Fisica, Universidade Federal de Sao Carlos, Sao Carlos, SP (Brazil)

    2008-07-15

    In this work it is reported the magnetic behavior of submicron and mesoscopic-size superconducting YBCO powders, prepared by a modified polymeric precursors method. The grain size and microstructure were analyzed using scanning electron microscopy (SEM). Measurements of magnetization and AC-susceptibility as a function of temperature were performed with a quantum design SQUID magnetometer. Our results indicated significant differences on the magnetic propreties, in connection with the calcination temperature and the pressure used to pelletize the samples. This contribution is part of an effort to study vortex dynamics and magnetic properties of submicron and mesoscopic-size superconducting samples.

  14. Pressure-induced phase transitions and correlation between structure and superconductivity in iron-based superconductor Ce(O(0.84)F(0.16))FeAs.

    Science.gov (United States)

    Zhao, Jinggeng; Liu, Haozhe; Ehm, Lars; Dong, Dawei; Chen, Zhiqiang; Liu, Qingqing; Hu, Wanzheng; Wang, Nanlin; Jin, Changqing

    2013-07-15

    High-pressure angle-dispersive X-ray diffraction experiments on iron-based superconductor Ce(O(0.84)F(0.16))FeAs were performed up to 54.9 GPa at room temperature. A tetragonal to tetragonal isostructural phase transition starts at about 13.9 GPa, and a new high-pressure phase has been found above 33.8 GPa. At pressures above 19.9 GPa, Ce(O(0.84)F(0.16))FeAs completely transforms to a high-pressure tetragonal phase, which remains in the same tetragonal structure with a larger a-axis and smaller c-axis than those of the low-pressure tetragonal phase. The structure analysis shows a discontinuity in the pressure dependences of the Fe-As and Ce-(O, F) bond distances, as well as the As-Fe-As and Ce-(O, F)-Ce bond angles in the transition region, which correlates with the change in T(c) of this compound upon compression. The isostructural phase transition in Ce(O(0.84)F(0.16))FeAs leads to a drastic drop in the superconducting transition temperature T(c) and restricts the superconductivity at low temperature. For the 1111-type iron-based superconductors, the structure evolution and following superconductivity changes under compression are related to the radius of lanthanide cations in the charge reservoir layer.

  15. 28 September 2011 - Canadian Intellectual Property Office Policy, International and Research Office Director K. Georgaras visiting the LHC superconducting magnet test hall with Engineer M. Bajko and Senior Scientists P. Jenni and R. Voss.

    CERN Multimedia

    2011-01-01

    28 September 2011 - Canadian Intellectual Property Office Policy, International and Research Office Director K. Georgaras visiting the LHC superconducting magnet test hall with Engineer M. Bajko and Senior Scientists P. Jenni and R. Voss.

  16. Synthesis, crystal structure, and electronic properties of high-pressure PdF2-type oxides MO2 (M = Ru, Rh, Os, Ir, Pt).

    Science.gov (United States)

    Shirako, Yuichi; Wang, Xia; Tsujimoto, Yoshihiro; Tanaka, Kie; Guo, Yanfeng; Matsushita, Yoshitaka; Nemoto, Yoshihiro; Katsuya, Yoshio; Shi, Youguo; Mori, Daisuke; Kojitani, Hiroshi; Yamaura, Kazunari; Inaguma, Yoshiyuki; Akaogi, Masaki

    2014-11-03

    The polycrystalline MO2's (HP-PdF2-type MO2, M = Rh, Os, Pt) with high-pressure PdF2 compounds were successfully synthesized under high-pressure conditions for the first time, to the best of our knowledge. The crystal structures and electromagnetic properties were studied. Previously unreported electronic properties of the polycrystalline HP-PdF2-type RuO2 and IrO2 were also studied. The refined structures clearly indicated that all compounds crystallized into the HP-PdF2-type structure, M(4+)O(2-)2, rather than the pyrite-type structure, M(n+)(O2)(n-) (n superconductivity nor a magnetic transition was detected down to a temperature of 2 K, unlike the case of 3d transition metal chalcogenide pyrites.

  17. Superconductivity at 52.5 K in the lanthanum-barium-copper-oxide system

    Science.gov (United States)

    Chu, C. W.; Hor, P. H.; Meng, R. L.; Gao, L.; Huang, Z. J.

    1987-01-01

    The electrical properties of the (La/0/9/Ba/0.1/)CuO/4-y/ system are examined under ambient and hydrostatic pressures. The resistance, ac magnetic susceptibility, and superconductivity onset, midpoint, and intercept temperatures are measured. It is observed that at ambient pressure the resistance decreases with temperature decreases, and the ac susceptibility shows diamagnetic shifts starting at about 32 K. Under hydrostatic pressure a superconducting transition with an onset temperature of 52.5 K is observed, and the resistance increases at lower temperatures. The data reveal that the electrical properties of the La-Ba-Cu-O system are dependent on samples and preparation conditions. Various causes for the high temperature superconductivity of the system are proposed.

  18. Dependences on RE of superconducting properties of transition metal co-doped (Ca, RE)FeAs2 with RE = La-Gd

    Science.gov (United States)

    Yakita, H.; Ogino, H.; Sala, A.; Okada, T.; Yamamoto, A.; Kishio, K.; Iyo, A.; Eisaki, H.; Shimoyama, J.

    2015-11-01

    Dependence of superconducting properties of (Ca, RE)(Fe, TM)As2 [(Ca, RE)112, TM: Co, Ni)] on RE elements (RE = La-Gd) was systematically investigated. Improvement of superconducting properties by Co or Ni co-doping was observed for all (Ca, RE)112, which is similar to Co-co-doped (Ca, La)112 or (Ca, Pr)112. Tc of Co-co-doped samples decreased from 38 K for RE = La to 29 K for RE = Gd with decreasing ionic radii of RE3+. However, Co-co-doped (Ca, Eu)112 showed exceptionally low Tc = 21 K probably due to the co-existence of Eu3+ and Eu2+ suggested by longer interlayer distance dFe-Fe of (Ca, Eu)112 than other (Ca, RE)112.

  19. Enhanced flux pinning properties in superconducting YBa{sub 2}Cu{sub 3}O{sub 7−z} films by a novel chemical doping approach

    Energy Technology Data Exchange (ETDEWEB)

    Wang, W.T., E-mail: wtwang@swjtu.edu.cn [Key Laboratory of Magnetic Levitation and Maglev Trains (Ministry of Education of China), Superconductivity R and D Center (SRDC), Southwest Jiaotong University, Mail Stop 165, Chengdu, Sichuan 610031 (China); Pu, M.H.; Lei, M.; Zhang, H.; Wang, Z. [Key Laboratory of Magnetic Levitation and Maglev Trains (Ministry of Education of China), Superconductivity R and D Center (SRDC), Southwest Jiaotong University, Mail Stop 165, Chengdu, Sichuan 610031 (China); Zhang, H. [Department of Physics, Peking University, Beijing 100871 (China); Cheng, C.H. [Key Laboratory of Magnetic Levitation and Maglev Trains (Ministry of Education of China), Superconductivity R and D Center (SRDC), Southwest Jiaotong University, Mail Stop 165, Chengdu, Sichuan 610031 (China); Superconductivity Research Group, School of Materials Science and Engineering, University of New South Wale, Sydney, 2052 NSW (Australia); Zhao, Y., E-mail: yzhao@swjtu.edu.cn [Key Laboratory of Magnetic Levitation and Maglev Trains (Ministry of Education of China), Superconductivity R and D Center (SRDC), Southwest Jiaotong University, Mail Stop 165, Chengdu, Sichuan 610031 (China); Superconductivity Research Group, School of Materials Science and Engineering, University of New South Wale, Sydney, 2052 NSW (Australia)

    2013-10-15

    Highlights: • Pure and Co-doped YBCO films were prepared by newly-developed chemical method. • The doped films have much denser and smoother surface microstructures. • Significantly enhanced fux-pinning properties have been obtained for dilute Co-doped flm. -- Abstract: Pure and cobalt-doped superconducting YBa{sub 2}Cu{sub 3}O{sub 7−z} (YBCO) films were prepared on (0 0 l) LaAlO{sub 3} substrate by a newly developed polymer-assisted metal organic deposition method. The cobalt-doped YBCO films display much denser and smoother surface microstructures and the superconducting transition temperature T{sub c} spans a small range of 1.7 K with the doping levels. Significantly enhanced flux-pinning properties have been obtained for dilute cobalt-doped film. This may be attributed to the good grain connections and the effective flux pinning centers introduced by cobalt doping.

  20. Nanoscale coherent intergrowthlike defects in a crystal of La1.9Ca1.1Cu2O6 +δ made superconducting by high-pressure oxygen annealing

    Science.gov (United States)

    Hu, Hefei; Zhu, Yimei; Shi, Xiaoya; Li, Qiang; Zhong, Ruidan; Schneeloch, John A.; Gu, Genda; Tranquada, John M.; Billinge, Simon J. L.

    2014-10-01

    Superconductivity with Tc=53.5 K has been induced in a large La1.9Ca1.1Cu2O6 (La-2126) single crystal by annealing in a high partial pressure of oxygen at 1200 °C. Using transmission electron microscopy techniques, we show that a secondary Ca-doped La2CuO4 (La-214) phase, not present in the as-grown crystal, appears as a coherent intergrowthlike defect as a consequence of the annealing. A corresponding secondary superconducting transition near 13 K is evident in the magnetization measurement. Electron energy-loss spectroscopy reveals a pre-edge peak at the O-K edge in the superconducting La-2126 phase, which is absent in the as-grown crystal, confirming the hole doping by interstitial oxygen.

  1. Superconductivity and structural characteristics of ceramic Pr{sub 2}Ba{sub 4}Cu{sub 7}O{sub 15-{delta}} prepared by ambient pressure synthesis using citrate pyrolysis method

    Energy Technology Data Exchange (ETDEWEB)

    Hagiwara, M. [Department of Comprehensive Sciences, Kyoto Institute of Technology, Sakyo-ku, Kyoto 606-8585 (Japan)], E-mail: hag@kit.ac.jp; Shima, T.; Tanaka, S.; Nishio, K.; Isshiki, T. [Department of Comprehensive Sciences, Kyoto Institute of Technology, Sakyo-ku, Kyoto 606-8585 (Japan); Saito, T.; Koyama, K. [University of Tokushima, Tokushima 770-8502 (Japan)

    2007-10-01

    Sintered material of Pr{sub 2}Ba{sub 4}Cu{sub 7}O{sub 15-{delta}} (Pr247) was synthesized at ambient pressure condition by using citrate pyrolysis precursor method, and the superconductivity caused by oxygen reduction treatment has been confirmingly observed and examined. By resistivity and magnetization experiments, it has been found that the critical temperature T{sub c} of the reduced samples could reach about 10 K higher than previously reported data for pure Pr247. Besides, from TEM observations, the present material was found to be heterogeneous system containing Pr247, Pr124 and novel stacking structure phases rich in CuO single chains. These results have suggested that oxygen-reduction at such region rich in the CuO single chains may affect the superconductivity of the adjacent crystal region containing CuO double chains, and might enhance the superconductive critical temperature.

  2. High temperature interfacial superconductivity

    Science.gov (United States)

    Bozovic, Ivan [Mount Sinai, NY; Logvenov, Gennady [Port Jefferson Station, NY; Gozar, Adrian Mihai [Port Jefferson, NY

    2012-06-19

    High-temperature superconductivity confined to nanometer-scale interfaces has been a long standing goal because of potential applications in electronic devices. The spontaneous formation of a superconducting interface in bilayers consisting of an insulator (La.sub.2CuO.sub.4) and a metal (La.sub.1-xSr.sub.xCuO.sub.4), neither of which is superconducting per se, is described. Depending upon the layering sequence of the bilayers, T.sub.c may be either .about.15 K or .about.30 K. This highly robust phenomenon is confined to within 2-3 nm around the interface. After exposing the bilayer to ozone, T.sub.c exceeds 50 K and this enhanced superconductivity is also shown to originate from a 1 to 2 unit cell thick interfacial layer. The results demonstrate that engineering artificial heterostructures provides a novel, unconventional way to fabricate stable, quasi two-dimensional high T.sub.c phases and to significantly enhance superconducting properties in other superconductors. The superconducting interface may be implemented, for example, in SIS tunnel junctions or a SuFET.

  3. Mechanical and physical properties of Bi-2223 and Nb3Sn superconducting materials between 300 K and 7 K

    Science.gov (United States)

    Nyilas, Arman; Osamura, Kozo; Sugano, Michinaka

    2003-09-01

    Within the framework of IEC/TC90-WG5 and VAMAS/TWA16, superconducting (SC) materials are investigated with respect to their mechanical properties between 300 K and 7 K. Besides the mechanical tests, physical and electrical properties are also determined for high Tc SC-tapes. The mechanical tests comprised the characterization of tensile properties at ambient temperature as well as at 7 K of Nb3Sn-reacted strands, Bi2223 tapes, pure silver tapes, silver bars, silver alloy tapes and bare filaments extracted from Bi-2223 tapes. All these investigations are carried out using a variable temperature helium gas flow cryostat equipped with a servo hydraulic tensile machine (MTS, model 810). For the load measurements specially developed, highly sensitive cryogenic proof in situ working load cells are used. For the strain determination of the wires, a high resolution ultra-light double extensometer system with a specially developed low noise signal conditioner is used. The engineering parameters such as yield strength and elastic modulus are evaluated using the obtained data with newly developed software. For the tiny and brittle filaments load versus displacement data are obtained. A determined master line (Young's modulus versus machine compliance) established by thin 0.125 mm Ø wires of different pure metals is used for the Young's modulus estimation of filaments. For the 4 K electrical voltage-current measurements under magnetic fields of up to 13 T, an existing test facility is used for the high Tc tapes. No dependency between applied strain up to 0.3% and the critical current under magnetic field could be observed for the selected specific Bi-2223 tapes. In addition, thermal expansion curves of Bi-2223 tapes along with pure silver and silver alloy (AgMg) are determined between 290 K and 7 K using in situ working extensometers. The coefficient of thermal expansion is evaluated by the determined thermal expansion versus temperature curve.

  4. Special structures and properties of hydrogen nanowire confined in a single walled carbon nanotube at extreme high pressure

    Directory of Open Access Journals (Sweden)

    Yueyuan Xia

    2012-06-01

    Full Text Available Extensive ab initio molecular dynamics simulations indicate that hydrogen can be confined in single walled carbon nanotubes to form high density and high pressure H2 molecular lattice, which has peculiar shell and axial structures depending on the density or pressure. The band gap of the confined H2 lattice is sensitive to the pressure. Heating the system at 2000K, the H2 lattice is firstly melted to form H2 molecular liquid, and then some of the H2 molecules dissociate accompanied by drastic molecular and atomic reactions, which have essential effect on the electronic structure of the hydrogen system. The liquid hydrogen system at 2000K is found to be a particular mixed liquid, which consists of H2 molecules, H atoms, and H-H-H trimers. The dissociated H atoms and the trimers in the liquid contribute resonance electron states at the Fermi energy to change the material properties substantially. Rapidly cooling the system from 2000K to 0.01 K, the mixed liquid is frozen to form a mixed solid melt with a clear trend of band gap closure. It indicates that this solid melt may become a superconducting nanowire when it is further compressed.

  5. Superconducting and normal state properties of the systems La1 -xMxPt4Ge12 (M = Ce ,Th )

    Science.gov (United States)

    Huang, K.; Yazici, D.; White, B. D.; Jeon, I.; Breindel, A. J.; Pouse, N.; Maple, M. B.

    2016-09-01

    Electrical resistivity, magnetization, and specific heat measurements were performed on polycrystalline samples of the filled-skutterudite systems La1 -xMxPt4Ge12(M =Ce and Th ) . Superconductivity in LaPt4Ge12 was quickly suppressed with Ce substitution and no evidence for superconductivity was found down to 1.1 K for x >0.2 . Temperature-dependent specific heat data at low temperatures for La1 -xCexPt4Ge12 show a change from power-law to exponential behavior, which may be an indication for multiband superconductivity in LaPt4Ge12 . A similar crossover was observed in the Pr1 -xCexPt4Ge12 system. However, the suppression rates of the superconducting transition temperatures Tc(x ) in the two systems are quite disparate, indicating a difference in the nature of superconductivity, which is conventional in LaPt4Ge12 and unconventional in PrPt4Ge12 . In comparison, a nearly linear and smooth evolution of Tc with increasing Th was observed in the La1 -xThxPt4Ge12 system, with no change of the superconducting energy gap in the temperature dependence of the specific heat, suggesting similar types of superconductivity in both the LaPt4Ge12 and ThPt4Ge12 compounds.

  6. Discovery of Superconductivity in Hard Hexagonal ε-NbN.

    Science.gov (United States)

    Zou, Yongtao; Qi, Xintong; Zhang, Cheng; Ma, Shuailing; Zhang, Wei; Li, Ying; Chen, Ting; Wang, Xuebing; Chen, Zhiqiang; Welch, David; Zhu, Pinwen; Liu, Bingbing; Li, Qiang; Cui, Tian; Li, Baosheng

    2016-02-29

    Since the discovery of superconductivity in boron-doped diamond with a critical temperature (TC) near 4 K, great interest has been attracted in hard superconductors such as transition-metal nitrides and carbides. Here we report the new discovery of superconductivity in polycrystalline hexagonal ε-NbN synthesized at high pressure and high temperature. Direct magnetization and electrical resistivity measurements demonstrate that the superconductivity in bulk polycrystalline hexagonal ε-NbN is below ∼11.6 K, which is significantly higher than that for boron-doped diamond. The nature of superconductivity in hexagonal ε-NbN and the physical mechanism for the relatively lower TC have been addressed by the weaker bonding in the Nb-N network, the co-planarity of Nb-N layer as well as its relatively weaker electron-phonon coupling, as compared with the cubic δ-NbN counterpart. Moreover, the newly discovered ε-NbN superconductor remains stable at pressures up to ∼20 GPa and is significantly harder than cubic δ-NbN; it is as hard as sapphire, ultra-incompressible and has a high shear rigidity of 201 GPa to rival hard/superhard material γ-B (∼227 GPa). This exploration opens a new class of highly desirable materials combining the outstanding mechanical/elastic properties with superconductivity, which may be particularly attractive for its technological and engineering applications in extreme environments.

  7. Influence of the introduction and formation of artificial pinning centers on the transport properties of nanostructured Nb{sub 3}Sn superconducting wires

    Energy Technology Data Exchange (ETDEWEB)

    Da Silva, L B S; Rodrigues, C A; Bormio-Nunes, C; Oliveira, N F Jr; Rodrigues, D Jr, E-mail: lucas_sarno@ppgem.eel.usp.b, E-mail: durval@demar.eel.usp.b [Superconductivity Group, Department of Materials Engineering (DEMAR) Escola de Engenharia de Lorena (EEL), Universidade de Sao Paulo - USP Polo Urbo-Industrial, Gleba AI-6 - PO Box 116 - Lorena, SP (Brazil)

    2009-05-01

    The formation of nanostructures projected to act as pinning centers is presented as a highly promising technique for the transport properties optimization of superconductors. However, due to the necessity of nanometric dimensions of these pinning centers, the heat treatment (HT) profiles must be carefully analyzed. The present work describes a methodology to optimize the HT profiles in respect to diffusion, reaction and formation of the superconducting phases. After the HT, samples were removed for micro structural characterization. Measurements of transport properties were performed to analyze the influence of the introduction of artificial pinning centers (APC) on the superconducting phase and to find the flux pinning mechanism acting in these wires. Fitting the volumetric pinning force vs. applied magnetic field (F{sub p} vs. mu{sub o}H) curves of transport properties, we could determine the type and influence of flux pinning mechanism acting in the global behavior of the samples. It was concluded that the maximum current densities were obtained when normal phases (due to the introduction of the APCs) are the most efficient pinning centers in the global behavior of the samples. The use of HT with profile 220{sup 0}C/100h+575{sup 0}C/50h+650{sup 0}C/100h was found as the best treatment for these nanostructured superconducting wires.

  8. Magnetic properties and pairing tendencies of the iron-based superconducting ladder BaFe2S3 : Combined ab initio and density matrix renormalization group study

    Science.gov (United States)

    Patel, Niravkumar D.; Nocera, Alberto; Alvarez, Gonzalo; Arita, Ryotaro; Moreo, Adriana; Dagotto, Elbio

    2016-08-01

    The recent discovery of superconductivity under high pressure in the two-leg ladder compound BaFe2S3 [H. Takahashi et al., Nat. Mater. 14, 1008 (2015), 10.1038/nmat4351] opens a broad avenue of research, because it represents the first report of pairing tendencies in a quasi-one-dimensional iron-based high-critical-temperature superconductor. Similarly, as in the case of the cuprates, ladders and chains can be far more accurately studied using many-body techniques and model Hamiltonians than their layered counterparts, particularly if several orbitals are active. In this publication, we derive a two-orbital Hubbard model from first principles that describes individual ladders of BaFe2S3 . The model is studied with the density matrix renormalization group. These first reported results are exciting for two reasons: (i) at half-filling, ferromagnetic order emerges as the dominant magnetic pattern along the rungs of the ladder, and antiferromagnetic order along the legs, in excellent agreement with neutron experiments; and (ii) with hole doping, pairs form in the strong coupling regime, as found by studying the binding energy of two holes doped on the half-filled system. In addition, orbital selective Mott phase characteristics develop with doping, with only one Wannier orbital receiving the hole carriers while the other remains half-filled. These results suggest that the analysis of models for iron-based two-leg ladders could clarify the origin of pairing tendencies and other exotic properties of iron-based high-critical-temperature superconductors in general.

  9. Experimental study on the ac loss properties of two-strand parallel conductors composed of superconducting multifilamentary strands

    CERN Document Server

    Iwakuma, M; Funaki, K

    2002-01-01

    The ac loss properties of two-strand superconducting parallel conductors were experimentally investigated by using NbTi multifilamentary strands with a rectangular cross section. We prepared the simple situation that was supposed in the previous theoretical study (M Iwakuma et al 2002 Supercond. Sci. Technol. 15 1525-36). The two insulated strands were sparsely co-wound into one-layer solenoidal coils. They were transposed only once and soldered at both ends. The ac losses in the sample coils were measured by a pick-up-coil method by applying uniform ac magnetic field parallel to the coil axis and comparing it with the theoretical results. The validity of the theoretical expressions derived in the previous paper was verified by the quantitative agreement with experiment in all the aspects, i.e. the dependencies on frequency, field amplitude and the deviation length in transposition in both the non-saturation and saturation cases and also the threshold condition between them. The results obtained support the t...

  10. Characterization of Mechanical Properties of MgB$_2$ Conductor for the Superconducting Link Project at CERN

    CERN Document Server

    Sugano, M; Bartova, B; Bjoerstad, R; Scheuerlein, C; Grasso, G

    2015-01-01

    In the framework of high luminosity upgrade of Large Hadron Collider at CERN, superconducting links are being developed. MgB2 wire is a candidate conductor for use in high-current cables. Mechanical properties of this material are of key importance for the definition of the cable design and operating conditions. In this study, we evaluated the Young's modulus of MgB2 filaments extracted from ex situ processed composite wires. The wires were produced in unit lengths of about 1 km and used in high-current cables. Single fiber tensile test was carried out on filaments composed of MgB2, Nb barrier, and Nb-Ni reaction layer. From the unloading modulus of filament specimens measured with different gauge lengths, the Young's modulus of composite filaments extracted from two different strands was determined to be 114 and 122 GPa at room temperature, respectively. By using the rule-of-mixture, the Young's modulus of MgB2 was estimated to be lower than that reported for highly dense MgB2 bulks. The reason for such diff...

  11. Characterization of the critical current and physical properties of superconducting epitaxial NbTiN sub-micron structures

    Energy Technology Data Exchange (ETDEWEB)

    Klimov, A., E-mail: aklimov@ite.waw.pl [Institute of Electron Technology, Al. Lotników 32/46, 02-668 Warsaw (Poland); Słysz, W.; Guziewicz, M. [Institute of Electron Technology, Al. Lotników 32/46, 02-668 Warsaw (Poland); Kolkovsky, V.; Zaytseva, I.; Malinowski, A. [Institute of Physics Polish Academy of Science, Al. Lotników 32/46, 02-668 Warsaw (Poland)

    2017-05-15

    Highlights: • This manuscript presents investigation of the critical current dependence of Nb(Ti)N nanostructured superconducting single photon detectors (SNSPD) in function of temperature and applied magnetic field. • Presented results are complimentary and compared with the same data received for submicron-wide single bridge Nb(Ti)N structures. • Our data demonstrate significant influence of local constrictions on physical properties of our SNSPD detectors. - Abstract: Measurements of critical current in NbTiN as a function of applied magnetic field and temperature are reported for two samples: 700-nm-wide bridge and 100-nm-wide meander. In 700-nm-wide NbTiN bridge we pinpointed the limiting factors for the critical current density to be current-driven vortex de-pinning at low temperatures and thermally activated flux flow closer to the transition temperature. In 100-nm-wide NbTiN meander we found phase slips activation, accompanied by hotspots formation at all measured temperatures. These two types of structures demonstrate different dependence of the critical current on the applied magnetic field. Although our NbTiN meander structures has high de-pairing critical current densities ∼10{sup 7} A/cm{sup 2} at low temperatures, the real critical currents are smaller due to the presence of the local constrictions.

  12. Physical properties of hexagonal WN2 under pressure

    Institute of Scientific and Technical Information of China (English)

    Li Xiao-Feng; Zhai Hong-Cun; Fu Hong-Zhi; Liu Zhong-Li; Ji Guang-Fu

    2011-01-01

    A first-principles study on the mechanical stability,elastic and thermodynamic properties of WN2 with P63/mmc and P-6m2 phases are reported using the pseudo potential plane wave method within the generalized gradient approximation. The calculated equilibrium parameters are in good agreement with the available theoretical data. A complete elastic tensor and crystal anisotropies of the ultra incompressible WN2 are determined in the wide pressure range. By the elastic stability criteria,it is predicted that P63/mmc and P-6m2 phases in WN2 are not stable above 175.1 Gpa and 170.1 Gpa,respectively. Finally,by using the quasiharmonic Debye model,the isothermal and adiabatic bulk modulus,and the heat capacity of WN2 are also successfully obtained.

  13. Superconducting electronics

    NARCIS (Netherlands)

    Rogalla, Horst

    1994-01-01

    During the last decades superconducting electronics has been the most prominent area of research for small scale applications of superconductivity. It has experienced quite a stormy development, from individual low frequency devices to devices with high integration density and pico second switching

  14. Control of the superconducting properties of Sr{sub 2−x}Ca{sub x}VO{sub 3}FeAs through isovalent substitution

    Energy Technology Data Exchange (ETDEWEB)

    Corkett, Alex J.; Free, David G. [Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford, OX1 3QR (United Kingdom); Cassidy, Simon J. [Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford, OX1 3QR (United Kingdom); Diamond Light Source Limited, Harwell Science and Innovation Campus, Didcot, OX11 0DE (United Kingdom); Ramos, Silvia [Diamond Light Source Limited, Harwell Science and Innovation Campus, Didcot, OX11 0DE (United Kingdom); Clarke, Simon J., E-mail: simon.clarke@chem.ox.ac.uk [Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford, OX1 3QR (United Kingdom)

    2014-08-15

    The effect of the isovalent substitution of Sr{sup 2+} by Ca{sup 2+} on the structure and superconducting properties of Sr{sub 2−x}Ca{sub x}VO{sub 3}FeAs is described in the compositional range 0≤x≤0.5. SQUID magnetometry measurements reveal that after an initial increase in T{sub c}, which is maximised at 29.5 K in Sr{sub 1.95}Ca{sub 0.05}VO{sub 3}FeAs, a rapid suppression of superconductivity is observed with increasing x. XANES spectra of Sr{sub 2−x}Ca{sub x}VO{sub 3}FeAs collected on the Fe and V absorption K-edges show that the position of both edges are invariant with composition within the experimental uncertainty. A combination of synchrotron X-ray powder diffraction and neutron powder diffraction techniques is used to rationalise the observed changes in T{sub c} with x, in terms of changes to the structure of the FeAs layer upon partial Ca substitution. These findings demonstrate that superconductivity in the Fe-based superconductors is extremely sensitive to the crystal structure with T{sub c} maximised in samples with regular FeAs{sub 4}-tetrahedra. - Graphical abstract: Superconducting transition temperature is controlled by structural parameters in Sr{sub 2−x}Ca{sub x}VO{sub 3}FeAs. - Highlights: • Substitution of Sr by Ca in the superconductor Sr{sub 2}VO{sub 3}FeAs is isovalent. • Relationship between superconducting T{sub c} and structural parameters is demonstrated. • Linear dependence of T{sub c} on structural parameters rather than composition.

  15. Effect of treatment pressure on treatment quality and bending properties of red pine lumber

    Science.gov (United States)

    Patricia K. Lebow; Stan T. Lebow; William J. Nelson

    2010-01-01

    Although higher treatment pressures have the potential to improve preservative penetration, higher pressures may possibly result in greater reduction in mechanical properties. The present study evaluated the effect of treatment pressure on the treatment quality and mechanical properties of red pine (Pinus resinosa Ait.) lumber. End-matched sections of red pine lumber...

  16. Superconducting properties of 3D low-density TI-bipolaron gas

    OpenAIRE

    Lakhno, V.D.

    2015-01-01

    Consideration is given to thermodynamical properties of a three-dimensional Bose-condensate of translation-invariant bipolarons (TI-bipolarons). The critical temperature of transition, energy, heat capacity and the transition heat of TI-bipolaron gas are calculated. The results obtained are used to explain experiments on high-temperature superconductors.

  17. Complex superconductivity in the noncentrosymmetric compound Re6Zr

    Science.gov (United States)

    Khan, Mojammel A.; Karki, A. B.; Samanta, T.; Browne, D.; Stadler, S.; Vekhter, I.; Pandey, Abhishek; Adams, P. W.; Young, D. P.; Teknowijoyo, S.; Cho, K.; Prozorov, R.; Graf, D. E.

    2016-10-01

    We report the electronic structure, synthesis, and measurements of the magnetic, transport, and thermal properties of the polycrystalline noncentrosymmetric compound Re6Zr . We observed a bulk superconducting transition at temperature Tc˜6.7 K, and measured the resistivity, heat capacity, thermal conductivity, and the London penetration depth below the transition, as well as performed doping and pressure studies. From these measurements we extracted the critical field and the superconducting parameters of Re6Zr . Our measurements indicate a relatively weak to moderate contribution from a triplet component to the order parameter, and favor a full superconducting gap, although we cannot exclude the existence of point nodes based on our data.

  18. Effect of substitution of Ce on superconducting properties of Bi1.7Pb0.3Sr2Ca2-CeCu3O10+ system

    Indian Academy of Sciences (India)

    R R Kothawale; B N Dole; S S Shah

    2002-05-01

    We have investigated the superconducting properties of the Bi1.7Pb0.3Sr2Ca2-CeCu3O10+ system with = 0.00, 0.02, 0.04, 0.08 and 0.1 by X-ray diffraction and magnetic susceptibility. The substitution of Ce for Ca has been found to drastically change the superconducting properties of the system. X-ray diffraction studies on these compounds indicate decrease in the -parameter with increased substitution of Ce at Ca site and volume fraction of high c(2 : 2 : 2 : 3) phase decreases and low c phase increases. The magnetic susceptibility of this compound shows that the diamagnetic on set superconducting transition temperature (onset) varies from 109 K to 51 K for =0.00, 0.02, 0.04, 0.08 and 0.1. These results suggest the possible existence of Ce in a tetravalent state rather than a trivalent state in this system; that is, Ca2+ → Ce4+ replacement changes the hole carrier concentration. Hole filling is the cause of lowering c of the system.

  19. Thermodynamic Properties of κ-(BEDT-TTF2X Salts: Electron Correlations and Superconductivity

    Directory of Open Access Journals (Sweden)

    Yasuhiro Nakazawa

    2012-06-01

    Full Text Available Heat capacity measurements of κ-(BEDT-TTF2X (BEDT-TTF: Bis(ethylendithio tetrathiafulvalene, X: counteranions which are classified as two-dimensional (2D dimer-Mott system are reported. At first, we explain structural and electronic features originated from rigid dimerization in donor arrangement in 2D layers. The antiferromagnetic Mott insulating phase located at low-pressure region in the phase diagram shows vanishing γ electronic heat capacity coefficient in the heat capacity, which claims opening of a charge-gap in this insulating state. Then, a systematic change of the γ around the Mott boundary region is reported in relation to the glass freezing of ethylene dynamics. The thermodynamic parameters determined by ∆Cp/γTc of 10 K class superconductors, κ-(BEDT-TTF2Cu(NCS2 and κ-(BEDT-TTF2Cu[N(CN2]Br demonstrate that a rather large gap with a strong coupling character appears around the Fermi-surface. On the other hand, the low temperature heat capacity clearly shows a picture of nodal-gap structure due to an anisotropic pairing. The comparison with lower Tc compounds in the κ-type structure is also performed so as to discuss overall features of the κ-type superconductors. The heat capacity measurements of hole-doped systems containing mercury in the counteranions show an anomalous enhancement of γ, which is consistent with the T1−1 of NMR experiments etc. The results of heat capacity measurements under high pressures are also reported.

  20. Evaluation of the thermophysical properties of tylose gel under pressure in the phase change domain

    OpenAIRE

    Otero, Laura; Ousegui, A.; Guignon, Bérengère; Le Bail, A.; Sanz Martínez, Pedro D.

    2006-01-01

    The accurate knowledge of the thermophysical properties of foods under pressure is essential to optimize high-pressure processes in the food industry. In this paper, two generic models are proposed based on the food composition: the additive model under pressure and the `shifting approach¿. The first one employs thermophysical properties of ice and water under pressure calculated as accurately as possible using sophisticated routines. The shifting approach offers a less accurate, but consider...

  1. Microstructure and properties of vacuum counter-pressure cast aluminum alloy

    OpenAIRE

    YAN Qing-song; Yu, Huan; WEI Bo-kang

    2006-01-01

    The microstructure and properties of vacuum counter-pressure cast aluminum alloy were studied. Results indicated that under the condition of vacuum counter-pressure, liquid melts fill mould cavity under the vacuum and crystallize under high pressure which have very good effect on nucleation and solidification feeding. Compared with gravity casting, the microstructure of vacuum counter-pressure cast aluminum alloy is much finer and more uniformly distributed. Mechanical properties of vacuum co...

  2. Nonlinearities in Microwave Superconductivity

    OpenAIRE

    Ledenyov, Dimitri O.; Ledenyov, Viktor O.

    2012-01-01

    The research is focused on the modeling of nonlinear properties of High Temperature Superconducting (HTS) thin films, using Bardeen, Cooper, Schrieffer and Lumped Element Circuit theories, with purpose to enhance microwave power handling capabilities of microwave filters and optimize design of microwave circuits in micro- and nano- electronics.

  3. Relationships between oxygen content, modulation period and superconducting property of Bi-based superconducting oxides. Bi kei sankabtsu chodendotai ni okeru sanso ganryo, hencho kozo oyobi chodendo tokusei no sokan

    Energy Technology Data Exchange (ETDEWEB)

    Deshimaru, Y.; Shimizu, Y.; Miura, N.; Yamazoe, N. (Kyushu Univ., Fukuoka (Japan). Graduate School of Engineering Sciences); Hiroi, Z.; Bando, Y. (Kyoto Univ., Kyoto (Japan). Inst. for Chemical Research)

    1992-09-10

    Two (2223 and 2212) of three superconducting phases in the Pb-doped Bi-Sr-Ca-Cu-O (BSCCO) oxide superconductor were examined for their changes of crystal structures and superconducting properties with changing oxygen content. Their oxygen sorption behavior examined by the temperature-programmed-desorption method showed that both samples desorb trace amounts of oxygen in a temperature range of 350-600 centigrade and the behavior examined by the temperature-programmed oxidation method showed that they absorb (absorb) reversibly oxygen desorbed above in a range of 100-350 centigrade. The critical temperature to bear diamagnetism (Tc) of the 2223 sample fell from 111 K to 96 K as oxygen was desorbed up to 600 centigrade. However, Tc recovers reversibly to the initial value when oxygen was re-absorbed. Contrary to the 2223, the 2212 sample showed the opposite Tc change. Both samples increased in their c-axes lengths and their modulation periods and the changes were reversible respectively. It was pointed out that the Tc behaviors of both sample systems were dependent on the concentration of holes on the CuO2 surfaces. 33 refs., 9 figs.

  4. High field transport properties of MBE processed Fe-based superconducting thin films

    Energy Technology Data Exchange (ETDEWEB)

    Iida, Kazumasa [Nagoya University (Japan); IFW Dresden (Germany)

    2015-07-01

    It has been reported that Fe-based superconductors show high upper critical fields with low anisotropies at low temperatures. Hence these materials may offer a unique possibility for high field magnet applications. However, only a few reports on high-field transport properties of Co-doped Ba-122 and Fe(Se,Te) have been published and the only one for SmFeAs(O,F) thin films to date. In order to use this material class for applications, the knowledge of in-field and its orientation dependence of transport properties in a wide range of external fields need to be clarified. In this talk, I will report on high-field (up to dc 45 T) transport properties of P-doped Ba-122, SmFeAs(O,F) and NdFeAs(O,F) thin films prepared by MBE. Although P-doped Ba-122 has the lowest T{sub c}, self-field J{sub c} of over 6 MA/cm{sup 2} at 4.2 K is recorded, which is the highest value ever reported in Fe-based superconductors. Additionally, in-field performance of P-doped Ba-122 shows comparable to those of NdFeAs(O,F) and SmFeAs(O,F) for Hc. On the other hand, both NdFeAs(O,F) and SmFeAs(O,F) exhibited higher J{sub c} for H parallel ab due to the intrinsic pinning. These results indicate that P-doped Ba-122 is the most promising candidates for high-field magnet applications.

  5. Electric and magnetic properties measurement and analysis of a conventional and a superconducting power transformer

    Science.gov (United States)

    Figueira, P.; Pronto, A. G.; Vilhena, N.; Pina, J. M.

    2014-05-01

    Power transformers based on High Temperature Superconductors (HTS) technology have revealed potential for several practical applications, offering economic, environmental and operational benefits. In this work, two 650 VA single-phase transformers prototypes were developed, tested and characterized: a conventional one, using copper windings, and another with the same primary copper winding, but with a secondary winding made of HTS BSCCO tape. The two prototypes were compared regarding magnetic properties, losses, electric parameters and efficiency, and the results are presented and interpreted. Also, several measures to determine AC critical current of the HTS tape were made. The results are compared with DC critical current for the same tape.

  6. Mechanical properties as an indicator of interstitials in niobium for superconducting accelerator cavities

    Energy Technology Data Exchange (ETDEWEB)

    Ricker, R. E., E-mail: richard.ricker@nist.gov; Pitchure, D. J., E-mail: david.pitchure@nist.gov [Materials Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, US (United States); Myneni, G. R., E-mail: rao@jlab.org [Thomas Jefferson National Accelerator Facility, Newport News, VA 23606, US (United States)

    2015-12-04

    A preliminary investigation was conducted into the feasibility of using simple mechanical properties experiments to evaluate interstitial impurity uptake from processing environments. Two types of tests were examined: tensile tests and complex modulus measurements using a dynamic mechanical analyzer (DMA). For the tensile tests, samples were cut from a single crystal of niobium, with the same orientation, and then prepared following different procedures. Significant differences were observed during tensile tests, with yielding strength and strain-to-failure clearly related to interstitial uptake. When the strain rate was reduced by an order of magnitude, the strain-to-failure was reduced by 18 % indicating that interstitial hydrogen is responsible for this behavior. For the complex modulus measurement, polycrystalline samples from different locations of two different ingots were examined at a frequency of 1.0 Hz while the temperature was increased at the rate of 1.0 °C per minute. Anaelastic peaks were found for C, N, and O in all samples, but the lower limit of the system did not allow for detection of a peak for H. It is concluded that mechanical properties could be developed as a measurement tool to guide the development of processing methods for producing reduced interstitial content material, but additional research, and uncertainty analysis, is required for these tools to be reliable in this application.

  7. Superconductivity in Weyl semimetal candidate MoTe2.

    Science.gov (United States)

    Qi, Yanpeng; Naumov, Pavel G; Ali, Mazhar N; Rajamathi, Catherine R; Schnelle, Walter; Barkalov, Oleg; Hanfland, Michael; Wu, Shu-Chun; Shekhar, Chandra; Sun, Yan; Süß, Vicky; Schmidt, Marcus; Schwarz, Ulrich; Pippel, Eckhard; Werner, Peter; Hillebrand, Reinald; Förster, Tobias; Kampert, Erik; Parkin, Stuart; Cava, R J; Felser, Claudia; Yan, Binghai; Medvedev, Sergey A

    2016-03-14

    Transition metal dichalcogenides have attracted research interest over the last few decades due to their interesting structural chemistry, unusual electronic properties, rich intercalation chemistry and wide spectrum of potential applications. Despite the fact that the majority of related research focuses on semiconducting transition-metal dichalcogenides (for example, MoS2), recently discovered unexpected properties of WTe2 are provoking strong interest in semimetallic transition metal dichalcogenides featuring large magnetoresistance, pressure-driven superconductivity and Weyl semimetal states. We investigate the sister compound of WTe2, MoTe2, predicted to be a Weyl semimetal and a quantum spin Hall insulator in bulk and monolayer form, respectively. We find that bulk MoTe2 exhibits superconductivity with a transition temperature of 0.10 K. Application of external pressure dramatically enhances the transition temperature up to maximum value of 8.2 K at 11.7 GPa. The observed dome-shaped superconductivity phase diagram provides insights into the interplay between superconductivity and topological physics.

  8. Experimental studies on the thermal properties of fast pulsed superconducting accelerator magnets; Experimentelle Untersuchungen thermischer Eigenschaften schnell gepulster supraleitender Beschleunigermagnete

    Energy Technology Data Exchange (ETDEWEB)

    Bleile, Alexander

    2016-01-06

    The new Facility for Antiproton and Ion Research FAIR is being constructed at the GSI research center in Darmstadt (Germany). This wordwide unique accelerator facility will provide beams of ions and antiprotons at high intensities and high energies for the fundamental research in nuclear, atomic and plasma physics as well as for applied science. The superconducting synchrotron SIS100 with a magnetic rigidity of 100 T/m, the core component of the FAIR facility will provide primary ion beams of all types from hydrogen up to uranium. One of the key technical systems of a new synchrotron are fast ramped electromagnets for the generation of fast ramped magnetic fields for deflecting and focusing of the ion beams. To reduce the energy consumption and to keep the operating costs of the synchrotron as low as possible superconducting magnet technology is applied in the SIS100. Superconducting magnets have been developed at GSI within the scope of the FAIR project. Although the superconducting magnet technology promises high cost saving, the power consumption of the fast ramped superconducting magnets can't be completely neglected. The pulsed operation generates dynamic losses in the iron yokes as well as in the superconducting coils of the magnets. A forced two-phase helium flow provides effective cooling for supercounducting magnets exposed to a continous relative high heat flow. The subject of this PhD thesis is experimental investigations and analysis of the dynamic power losses in fast ramped superconducting magnets and their dependencies on the operation cycles of the synchrotron. This research was conducted on the the first series SIS100 dipole magnet. Based on the experimentally defined dynamic heat loads and helium mass flow rates in the dipole magnet the heat loads and helium consumption for all other types of superconducting magnet modules of the SIS100 have been estimated. These results are essential for the development of the cooling system for the the

  9. Development of Superconducting Strang and Cable with Improved Properties for Use in SSC Magnets

    Energy Technology Data Exchange (ETDEWEB)

    Scanlan, R.M.

    1989-02-01

    The critical current requirement for the NbTi superconductor strand was set at 2750 A/mm{sup 2} (5 T, 4.2 K) in the SSC Conceptual Design, compared with a value of 1800 A/mm{sup 2} which was specified for the strand used in the Tevatron dipoles. In addition, a filament diameter of 5 {micro}m, instead of the 9 {micro}m diameter used in the Tevatron. was chosen to reduce field distonion at injection. In order to meet the requirements for field homogeneity, the dimensional requirements for both strand and cable were also tightened. The technical solutions employed to achieve these improved properties and the resulting specifications will be discussed.

  10. The elastic constants and anisotropy of superconducting MgCNi3 and CdCNi3 under different pressure

    KAUST Repository

    Feng, Huifang

    2013-11-23

    The second-order elastic constants (SOECs) and third-order elastic constants (TOECs) of MgCNi3 and CdCNi3 are presented by using first-principles methods combined with homogeneous deformation theory. The Voigt-Reuss-Hill (VRH) approximation are used to calculate the bulk modulus B, shear modulus G, averaged Young\\'s modulus E and Poisson\\'s ratio ν for polycrystals and these effective modulus are consistent with the experiments. The SOECs under different pressure of MgCNi3 and CdCNi3 are also obtained based on the TOECs. Furthermore, the Zener anisotropy factor, Chung-Buessem anisotropy index, and the universal anisotropy index are used to describe the anisotropy of MgCNi3 and CdCNi3. The anisotropy of Young\\'s modulus of single-crystal under different pressure is also presented. © 2013 Springer Science+Business Media New York.

  11. Transport properties of liquid metal hydrogen under high pressures

    Science.gov (United States)

    Brown, R. C.; March, N. H.

    1972-01-01

    A theory is developed for the compressibility and transport properties of liquid metallic hydrogen, near to its melting point and under high pressure. The interionic force law is assumed to be of the screened Coulomb type, because hydrogen has no core electrons. The random phase approximation is used to obtain the structure factor S(k) of the system in terms of the Fourier transform of this force law. The long wavelenth limit of the structure factor S(o) is related to the compressibility, which is much lower than that of alkali metals at their melting points. The diffusion constant at the melting point is obtained in terms of the Debye frequency, using a frequency spectrum analogous with the phonon spectrum of a solid. A similar argument is used to obtain the combined shear and bulk viscosities, but these depend also on S(o). The transport coefficients are found to be about the same size as those of alkali metals at their melting points.

  12. Superconductivity in a chiral nanotube

    Science.gov (United States)

    Qin, F.; Shi, W.; Ideue, T.; Yoshida, M.; Zak, A.; Tenne, R.; Kikitsu, T.; Inoue, D.; Hashizume, D.; Iwasa, Y.

    2017-02-01

    Chirality of materials are known to affect optical, magnetic and electric properties, causing a variety of nontrivial phenomena such as circular dichiroism for chiral molecules, magnetic Skyrmions in chiral magnets and nonreciprocal carrier transport in chiral conductors. On the other hand, effect of chirality on superconducting transport has not been known. Here we report the nonreciprocity of superconductivity--unambiguous evidence of superconductivity reflecting chiral structure in which the forward and backward supercurrent flows are not equivalent because of inversion symmetry breaking. Such superconductivity is realized via ionic gating in individual chiral nanotubes of tungsten disulfide. The nonreciprocal signal is significantly enhanced in the superconducting state, being associated with unprecedented quantum Little-Parks oscillations originating from the interference of supercurrent along the circumference of the nanotube. The present results indicate that the nonreciprocity is a viable approach toward the superconductors with chiral or noncentrosymmetric structures.

  13. Strain dependence of critical superconducting properties of Nb3Sn with different intrinsic strains based on a semi-phenomenological approach

    Science.gov (United States)

    Zhang, Rui; Gao, Peifeng; Wang, Xingzhe

    2017-09-01

    A semi-phenomenological approach, which combined the microscopic properties calculated by first-principles and macroscopic critical characteristics determined from empirical relations, is suggested to investigate the superconducting critical properties of the low temperature superconductor Nb3Sn with different intrinsic strain modes like uniaxial tension, shear and torsion deformations. Firstly, the microscopic properties of the electronic structure and density of state for Nb3Sn are numerically obtained by first-principles calculations using density-functional theory in the generalized gradient approximation. These are further incorporate with the macroscopic empirical relation of the unified scaling law for predicting critical parameters of the strained Nb3Sn superconductor. The superconducting critical profiles of critical temperature, magnetic field and current, in such a way, are achieved for Nb3Sn under different strains. The predictions on the critical parameters of the superconductor bulk in uniaxial tension/compression state exhibit obvious degradations and bell-shaped curves with maximum critical values at zero strain and a slight asymmetry between the tensile and compressive strains, which show quite good agreements with the experimental data. As for Nb3Sn under shear and torsion deformations, the similar degradations on critical parameters also are presented which are monotonously decreased with the applied strains. The first-principles calculations and results in this work are based on an assumption which the superconducting critical properties from the strain-induced variations in the electronic density of states. Furthermore, the modified critical surfaces of Nb3Sn, determined by the critical temperature, current and magnetic field dependence upon the applied different strains are depicted. The present study will be helpful to identify the scaling relation for the critical parameters and understanding the origin of strain sensitivity in Nb3Sn

  14. Structural studies of type N superconductive compounds: R{sub 2-x}Ce{sub x}CuO{sub 4{+-}{delta}} (R = Gd, Eu, Sm, Nd, Pr); influences of chemical treatments on physical properties; Etudes structurales des composes supraconducteurs de type N: R{sub 2-x}Ce{sub x}CuO{sub 4{+-}{delta}} (R = Gd, Eu, Sm, Nd, Pr); influences des traitements chimiques sur les proprietes physiques

    Energy Technology Data Exchange (ETDEWEB)

    Vigoureux, P.

    1995-06-01

    Different chemical treatments of R{sub 2-x}Ce{sub x}CuO{sub 4{+-}{delta}} compounds monocrystals (gadolinium, europium, samarium, neodymium and praseodymium cuprates) modify their physical properties especially their superconductive properties. The presented chemical treatments are: the substitution of the trivalent rare earth element R by an other trivalent lanthanide, its substitution by tetravalent cerium, and heat treatment under low oxygen pressure. After these chemical treatments, structural modifications are observed by neutrons and X-rays diffraction, and allow to precise their actions: size effect of the rare earth element on the deformation of the CuO{sub 2} planes, links between deformation and superconductivity and magnetic properties. (A.B.). 394 refs/.

  15. Hierarchic Models of Turbulence, Superfluidity and Superconductivity

    CERN Document Server

    Kaivarainen, A

    2000-01-01

    New models of Turbulence, Superfluidity and Superconductivity, based on new Hierarchic theory, general for liquids and solids (physics/0102086), have been proposed. CONTENTS: 1 Turbulence. General description; 2 Mesoscopic mechanism of turbulence; 3 Superfluidity. General description; 4 Mesoscopic scenario of fluidity; 5 Superfluidity as a hierarchic self-organization process; 6 Superfluidity in 3He; 7 Superconductivity: General properties of metals and semiconductors; Plasma oscillations; Cyclotron resonance; Electroconductivity; 8. Microscopic theory of superconductivity (BCS); 9. Mesoscopic scenario of superconductivity: Interpretation of experimental data in the framework of mesoscopic model of superconductivity.

  16. Peak effect and superconducting properties of SmFeAsO{sub 0.8}F{sub 0.2} wires

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Y L; Cui, Y J; Yang, Y; Zhang, Y; Wang, L; Zhao, Y [Key Laboratory of Magnetic Levitation Technologies and Maglev Trains, Ministry of Education of China, and Superconductivity R and D Center (SRDC), Southwest Jiaotong University, Chengdu, Sichuan 610031 (China); Cheng, C H; Sorrell, C [School of Materials Science and Engineering, University of New South Wales, Sydney, NSW 2052 (Australia)], E-mail: yzhao@swjtu.edu.cn

    2008-11-15

    Ta-sheathed SmFeAsO{sub 0.8}F{sub 0.2} superconducting wires with T{sub c} = 52.5 K have been fabricated using the powder-in-tube (PIT) method and the superconducting properties of the wires have been investigated. The wires exhibit a very large intragrain critical current density at a temperature below 30 K. A peak effect with maximal J{sub c} = 0.6 MA cm{sup -2} at 10 K under 6 T field was observed. The peak field H{sub pear} is strongly temperature-dependent. A severe weak-link effect depresses the development of global supercurrent owing to a very short coherence length. The wires also show a power law temperature dependence for the irreversibility line with H{sub irr}{approx_equal}(1-T/T{sub c}){sup 1.5}. The H-T phase diagram was found to be similar to that of other superconducting cuprates.

  17. Microstructure and superconducting properties of nanocarbon-doped internal Mg diffusion-processed MgB2 wires fabricated using different boron powders

    Science.gov (United States)

    Xu, Da; Wang, Dongliang; Li, Chen; Yuan, Pusheng; Zhang, Xianping; Yao, Chao; Dong, Chiheng; Huang, He; Ma, Yanwei; Oguro, Hidetoshi; Awaji, Satoshi; Watanabe, Kazuo

    2016-04-01

    MgB2/Nb/Monel monofilament wires were fabricated using four different boron powders by an internal Mg diffusion (IMD) process. The microstructure, morphology and the critical current density (J c) of the used boron powders and the formative MgB2 layers were analyzed and compared. It was found that the purity and particle size of the boron powder influence the superconducting properties of MgB2 wires; further that the optimized heat-treatment condition also depends on the quality of the boron powder. The highest J c was obtained in the MgB2 layer made using amorphous boron (AB) powder, although a certain amount of voids existed in the superconducting layer. The IMD-processed MgB2 layer fabricated using high-purity boron (HB) powder had also a high J c compared with the powder-in-tube (PIT) process and a few unreacted boron particles remained in it. MgB2 wire fabricated using low-purity boron (LB) powder had a high cost-performance ratio compared with the others, which is expected to allow the fabrication of large-scale and low-cost superconducting wires for practical application. However, the enhancement of the J c was not found in the MgB2 layer manufactured using the ball-milled LB (MLB) powder as expected due to the increased percentage of impurity.

  18. Structure and properties of loaded silica contacts during pressure solution: impedance spectroscopy measurements under hydrothermal conditions

    NARCIS (Netherlands)

    Noort, R. van; Spiers, C.J.; Peach, C.J.

    2011-01-01

    In order to investigate directly the structure and properties of grain boundaries in silicatematerials undergoing pressure solution, in situmeasurements of these properties are required. We report electrical impedance spectroscopy measurements, performed, under hydrothermal conditions,

  19. Fabrication and superconducting properties of nano-SiC doped MgB2 tapes

    Institute of Scientific and Technical Information of China (English)

    ZHANG XianPing; MA YanWei; GAO ZhaoShun; YU ZhengGuang; WANG DongLiang; WATANABE K; GUO JianDong

    2007-01-01

    Nano-SiC doped MgB2 tapes were prepared by the in situ powder-in-tube method. Heat treatment was performed at 650℃ for 1 h. XRD data indicate that SiC particles had reacted with the MgB2 during sintering process. MgB2 core seemed to be denser after SiC doping, and the critical temperature was slightly depressed. The critical current density Jc of the SiC doped tapes was significantly enhanced in magnetic fields up to 14 T compared to the undoped ones. For the 5% SiC doped samples, Jc was increased by a factor of 32 at 4.2 K, 10 T. The enhancement of Jc-B properties in SiC doped MgB2 tapes is considered to be due to the enhancement of grain linkages and the introduction of effective flux pining centers. The substitution of B by C in MgB2 grains is thought to be the main reason for the improvement of the flux pinning ability in SiC doped MgB2 tapes.

  20. Coherent transport properties of a three-terminal hybrid superconducting interferometer

    Science.gov (United States)

    Vischi, F.; Carrega, M.; Strambini, E.; D'Ambrosio, S.; Bergeret, F. S.; Nazarov, Yu. V.; Giazotto, F.

    2017-02-01

    We present an exhaustive theoretical analysis of a double-loop Josephson proximity interferometer, such as the one recently realized by Strambini et al. for control of the Andreev spectrum via an external magnetic field. This system, called ω -SQUIPT, consists of a T-shaped diffusive normal metal (N ) attached to three superconductors (S ) forming a double-loop configuration. By using the quasiclassical Green-function formalism, we calculate the local normalized density of states, the Josephson currents through the device, and the dependence of the former on the length of the junction arms, the applied magnetic field, and the S /N interface transparencies. We show that by tuning the fluxes through the double loop, the system undergoes transitions from a gapped to a gapless state. We also evaluate the Josephson currents flowing in the different arms as a function of magnetic fluxes, and we explore the quasiparticle transport by considering a metallic probe tunnel-coupled to the Josephson junction and calculating its I -V characteristics. Finally, we study the performances of the ω -SQUIPT and its potential applications by investigating its electrical and magnetometric properties.

  1. Electrical dissipation and material properties of in-plane anisotropic superconducting YBCO films

    CERN Document Server

    Czerwinka, P S

    2001-01-01

    vortex liquid-to-glass phase transition model (VG). In all cases, the data can be successfully collapsed when scaled under the VG algorithm forming the expected master curves for temperatures above and below the vortex-glass 'transition' temperature T sub V sub G (B). However, between film systems we observe wide variations of the critical exponent z(theta,B) and T sub V sub G (B) as a function of field strength (B) and field orientation (theta). This lack of 'universality' does not allow interpretation of the scaling as evidence for a vortex liquid-to-glass phase transition. We find quantitative evidence in support of alternative scaling models which are based upon conventional flux-flow/creep theories and distributions of vortex-pinning strength. We investigate the growth, material and electrical properties of a wide variety of YBa sub 2 Cu sub 3 O sub 7 sub - subdelta films (40-480nm). The films range from c-axis normal to c-axis parallel to the film plane and were grown upon SrTiO sub 3 (STO) and LaSrGaO ...

  2. Growth and superconducting properties of Cd-doped La(O,F)BiS2 single crystals

    Science.gov (United States)

    Nagao, Masanori; Tanaka, Masashi; Watauchi, Satoshi; Takano, Yoshihiko; Tanaka, Isao

    2017-08-01

    Cd-doped La(O,F)BiS2 single crystals were grown using a CsCl/KCl flux. The grown crystals have a plate-like shape with 1-2 mm square size in a well-developed ab-plane. The Cd doping in the crystals was successfully characterized by single crystal X-ray diffraction and electron probe microanalysis techniques. The superconductivity of La(O,F)BiS2 was gradually suppressed with Cd doping. The superconducting transition temperature with zero resistivity of La(O0.54F0.46)(Bi0.92Cd0.08)S2 was 2.3 K. The Cd doping does not change the superconducting anisotropy so much, albeit the considerable suppression of Tc.

  3. Competing effects of surface phonon softening and quantum size effects on the superconducting properties of nanostructured Pb

    Energy Technology Data Exchange (ETDEWEB)

    Bose, Sangita; Galande, Charudatta; Chockalingam, S P; Raychaudhuri, Pratap; Ayyub, Pushan [Department of Condensed Matter Physics and Material Science, Tata Institute of Fundamental Research, Mumbai 400005 (India); Banerjee, Rajarshi [Department of Materials Science and Engineering, University of North Texas, Denton, TX 76203-5310 (United States)], E-mail: Sangita.Bose@fkf.mpg.de, E-mail: pratap@tifr.res.in, E-mail: pushan@tifr.res.in

    2009-05-20

    The superconducting transition temperature (T{sub C}) in nanostructured Pb decreases from 7.24 to 6.4 K as the particle size is reduced from 65 to 7 nm, below which superconductivity is lost rather abruptly. In contrast, there is a large enhancement in the upper critical field (H{sub C2}) in the same size regime. We explore the origin of the unusual robustness of T{sub C} over such a large particle size range in nanostructured Pb by measuring the temperature dependence of the superconducting energy gap in planar tunnel junctions of Al/Al{sub 2}O{sub 3}/nano-Pb. We show that below 22 nm, the electron-phonon coupling strength increases monotonically with decreasing particle size, and almost exactly compensates for the quantum size effect, which is expected to suppress T{sub C}.

  4. The Effect of Pressure on Magnetic Properties of KMnCr(CN6.

    Directory of Open Access Journals (Sweden)

    Csach K.

    2013-01-01

    Full Text Available In the contribution we present the effect of pressure on magnetic properties of molecule based magnet KMnCr(CN6. Applied pressure affects magnetization curves only marginally. The saturation is reached at higher magnetic fields under pressure, but the effect of the pressure on the values of saturated magnetization µs, remnant magnetization µr and coercive field HC are almost negligible. Observed pronounced increase of the Curie temperature TC with increasing pressure can be attributed to strengthening of antiferromagnetic superexchange interaction. Additionally we observed double magnetic transition induced by hydrostatic pressure. All pressure changes were fully reversible.

  5. Effect of CuO2 planes on the structural and superconducting transport properties of [CuTl - 12(n - 1)n;n = 2,3,4] superconductor family

    Science.gov (United States)

    Muzaffar, M. Usman; Khan, Nawazish A.

    2016-06-01

    Cu0.5Tl0.5Ba2Can-1CunO2n+4-δ (n = 2, 3, 4) superconducting bulk samples have been synthesized by using two-step solid state reaction method. We investigated the effects of CuO2 planes on the structural and superconducting transport properties of [CuTl - 12(n - 1)n; n = 2, 3, 4] superconducting family. These samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) absorption spectroscopy and DC-resistivity (ρ) measurements. These samples are c-axis length oriented and have shown orthorhombic crystal structure. All the samples have shown metallic variations of resistivity from room temperature down to onset of superconductivity. The zero resistivity critical temperature Tc(R = 0) increases with the increase in superconducting planes and normal state resistivity systematically decreases, which show the density of inadvertent defects decreases in the final compound. The apical oxygen phonon modes are hardened as observed in the FTIR absorption measurements. The intrinsic microscopic superconducting parameters, such as the cross-over temperatures, coherence length along c-axis (ξc(0)) at 0 K, inter-layer coupling (J), inter-grain coupling (α) and fermi velocity (VF), were extracted from the fluctuation-induced conductivity (FIC) analysis. FIC analysis also showed the improvement in superconductivity with the increase in CuO2 planes.

  6. Superconducting and ferromagnetic properties of NbN/NiCu and NbTiN/NiCu bilayer nanostructures for photon detection

    Science.gov (United States)

    Klimov, A.; Puźniak, R.; Aichner, B.; Lang, W.; Joon, E.; Stern, R.; Słysz, W.; Guziewicz, M.; Juchniewicz, M.; Borysiewicz, M. A.; Kruszka, R.; Wegrzecki, M.; Łaszcz, A.; Czerwinski, A.; Sobolewski, Roman

    2015-05-01

    Performance of superconducting single-photon detectors based on resistive hotspot formation in nanostripes upon optical photon absorption depends strongly on the critical current density JC of the fabricated nanostructure. Utilization of an ultrathin, weak-ferromagnet cap layer on the top of a superconducting film enhances of the structure's JC due to an extra flux pinning. We have fabricated a number of both NbN/NiCu and NbTiN/NiCu superconductor/ferromagnet (S/F) ultrathin bilayers and microbridges. NbN and NbTiN underlayers with thicknesses varying from 4 to 7 nm were grown using dc-magnetron sputtering on chemically cleaned sapphire single-crystal substrates. After rapid thermal annealing at high temperatures, the S films were coated with Ni0.54Cu0.46 overlayers with thicknesses of about 6 nm, using cosputtering. Compositions of the deposited films were confirmed by EDX spectroscopy analysis, while TEM studies demonstrated excellent epitaxial quality of our S layers with ~2-nm-thick F/S transition layer and atomically-sharp S/substrate interface. Magnetic properties of bilayers were studied using both the SQUID and Vibrating Sample Magnetometer techniques in low and high magnetic fields. Low-temperature tests confirmed that in all cases NiCu films were ferromagnetic with the Curie temperature of above 30 K. Below the bilayer critical temperature of approx. 12-13 K, the structures were fully proximitized with the strong superconducting signal. For superconducting transport properties characterization, we used bilayers patterned into 40-μm-long microbridges with the width varying from 0.4 μm to 2 μm. The same S/F nanostructures were also used to study their superconducting fluctuations. The temperature dependence of magnetoresistance demonstrated highly 2-dimensional character with an unusual negative region that extended almost to room temperature. In the S/F sample, the fluctuations were observed to be substantially below theoretical expectations.

  7. Effect of hydrostatic pressure on the superconducting transition temperature and superfluid density of SmFeAsO0.85 and PrFe0.925Co0.075AsO superconductors

    Science.gov (United States)

    Dong, X. L.; Lu, W.; Yang, J.; Yi, W.; Li, Z. C.; Zhang, C.; Ren, Z. A.; Che, G. C.; Sun, L. L.; Zhou, F.; Zhou, X. J.; Zhao, Z. X.

    2010-12-01

    We have measured magnetic susceptibility of iron pnictide superconductors SmFeAsO0.85 and PrFe0.925Co0.075AsO under hydrostatic pressure up to 1.15 GPa. The superconducting transition temperature (TC) deceases linearly and the Meissner signal size also decreases with increasing pressure for SmFeAsO0.85 . In contrast, the TC of PrFe0.925Co0.075AsO initially increases with pressure then saturates above ˜0.8GPa . Meanwhile its Meissner signal exhibits the similar pressure dependence. Our results indicate that the pressure dependences of TC and superfluid density in both systems are positively correlated which suggests that these quaternary iron-based superconductors are not conventional BCS ones.

  8. Prediction of Superconductivity for Oxides Based on Structural Parameters and Artificial Neural Network Method

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Superconductive properties for oxides were predicted by artificial neural network (ANN) method with structural and chemical parameters as inputs. The predicted properties include superconductivity for oxides, distributed ranges of the superconductive transition temperature (Tc) for complex oxides, and Tc values for cuprate superconductors. The calculated results indicated that the adjusted ANN can be used to predict superconductive properties for unknown oxides.

  9. Study on Wood Drying Properties under Vacuum-floating Pressure

    Institute of Scientific and Technical Information of China (English)

    ZHANGBiguang; YISonghn; CHANGJianmin; LIXianjun

    2004-01-01

    Using Masson pine as specimens, when drying mediums are overheated steam and hot-air respectively, preheating characteristics of wood under vacuum-floating pressure drying are discussed by measurement of internal temperature field and variation of moisture content during period of preheating. The relationship between drying medium conditions and drying rate of wood reveals that, firstly, compared with process of air-drying, time needed to be preheated under vacuum-floating decreased dramatically, meanwhile,the magnitude of condensation on the surface is relatively larger. Secondly, drying rate of wood under vacuum-floating pressure increases coupled with temperature of medium, reduction of absolute pressure,and raise of fluctuation rate of pressure. The sequence of factors contribution to drying rate is listed as following: temperature of medium (t) > fluctuation rate of pressure (f)> absolute pressure (p).

  10. MgB2 superconducting wires basics and applications

    CERN Document Server

    2016-01-01

    The compendium gives a complete overview of the properties of MgB2 (Magnesium Diboride), a superconducting compound with a transition temperature of Tc = 39K, from the fundamental properties to the fabrication of multifilamentary wires and to the presentation of various applications. Written by eminent researchers in the field, this indispensable volume not only discusses superconducting properties of MgB2 compounds, but also describes known preparation methods of thin films and of bulk samples obtained under high pressure methods. A unique selling point of the book is the detailed coverage of various applications based on MgB2, starting with MRI magnets and high current cables, cooled by Helium (He) vapor. High current cables cooled by liquid hydrogen are also highlighted as an interesting alternative due to the shrinking He reserves on earth. Other pertinent subjects comprise permanent magnets, ultrafine wires for space applications and wind generator projects.

  11. Definitions of the physical properties of pressure ulcers and characterisation of their regional variance.

    Science.gov (United States)

    Mizokami, Fumihiro; Furuta, Katsunori; Utani, Atsushi; Isogai, Zenzo

    2013-10-01

    A pressure ulcer is a localised injury of the skin and underlying tissue that usually develops over a bony prominence. A decrease in the pressure over the bony prominence effectively prevents pressure ulcers; however, no studies have systematically assessed the physical properties of existing pressure ulcers. To characterise pressure ulcers, we established new terminology that clarifies the physical properties of pressure ulcers: wound mobility was defined as movement using the bony prominence as a predefined specific marker, and wound deformity was defined as a change in the three-dimensional shape of the wound. Observational studies using this terminology showed that the distinct physical properties of pressure ulcers depend on the site of development and the wound depth according to the National Pressure Ulcer Advisory Panel criteria. Most grade IV sacrum pressure ulcers exhibited mobility and deformity. Superficial sacrum pressure ulcers below grade II showed only mobility. In contrast, foot pressure ulcers did not exhibit mobility or deformity. We propose a new concept, 'wound physical property', for understanding the unique pathogenesis of pressure ulcers. © 2012 The Authors. International Wound Journal © 2012 John Wiley & Sons Ltd and Medicalhelplines.com Inc.

  12. 40 CFR 1065.120 - Fuel properties and fuel temperature and pressure.

    Science.gov (United States)

    2010-07-01

    ... and pressure. 1065.120 Section 1065.120 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... properties and fuel temperature and pressure. (a) Use fuels as specified in the standard-setting part, or as... engine manufacturer specifies fuel temperature and pressure tolerances and the location where they are to...

  13. Advanced surface cleaning methods: three years of experience with high pressure ultrapure water rinsing of superconducting cavaties

    Energy Technology Data Exchange (ETDEWEB)

    Kneisel, P.; Lewis, B.

    1995-01-01

    In the last three years we have carried out a large number of tests ofn single cell and multi-cell niobium and Nb{sub 3}Sn cavities at L- band frequencies, which as a final surface cleaning step had been rinsed with high pressure jets of ultrapure water. This treatment resulted in an unprecedented quality and reproducibility of cavity performance. Field emission free surfaces up to peak surface electric fields of E{sup peak} {ge} 45 MV/m were achieved nearly routinely after buffered chemical polishing of niobium surfaces. In addition, residual surface resistances below R{sub res} {le} 10 n{Omega} and as low as R{sub res} = 2 n{Omega} were not uncommon. In 5-cell production cavities of the Cornell/CEBAF shape gradients as high as E{sub acc} =21.5 MV/m corresponding to peak surface fields of E{sub peak} {approx} 55 MV/m have been measured after post purification with Ti without the need for rf-processing. Several Nb{sub 3}Sn - cavities exhibited no field emission loading after high pressure ultrapure water rinsing up to the maximum achievable surface fields of E{sup peak} {approx} 33 MV/m; the field limits were given by the available rf-power. The unprecedented reproducibility of the cavities permitted serial testing of various parameters affecting cavity performance such as the influence of residual gas inside the cavities prior to cooldown, the removal of the surface damage layer or the impact of peripheral parts such as rf-windows. The major portion of this paper summarizes several of the results obtained from investigations carried out during the last three years. The second part discusses possibilities for further improvements in cavity cleaning.

  14. STRUCTURAL AND SUPERCONDUCTING PROPERTIES OF LA2-XSRXCUO4+Y (0-LESS-THAN-X-LESS-THAN-0.15) PREPARED BY ROOM-TEMPERATURE CHEMICAL OXIDATION

    DEFF Research Database (Denmark)

    Rial, C.; Morán, E.; Alario-Franco, M.A.;

    1995-01-01

    The presence of interstitial oxygen in room temperature chemically oxidized La2-xSrxCuO4+y, (0.15superconducting properties of these cuprates. The existence of a structural limit for the insertion of oxygen under the current oxidation...... conditions, related to the relieving of the internal strain of these materials, is proposed. Besides, oxidized materials show an almost constant T-c close to that corresponding to the optimum hole doping concentration. The coincidence of both features is remarked upon and discussed....

  15. On the structural properties and superconductivity of room-temperature chemically oxidized La2-xBaxCuO4+y (0<=x<=0.15)

    DEFF Research Database (Denmark)

    Rial, C.; Moran, E.; Alario-Franco, M.A.;

    1996-01-01

    The insertion of oxygen within the structure of La2-xBaxCuO4+y (x less than or equal to 0.15), by means of room-temperature chemical oxidation, modifies both the physical and the structural features of these materials, Concerning the superconducting properties, the extra oxygen gives rise...... and differences concerning the modifications induced by this oxidation process in the present series of La2-xBaxCuO4+y compounds and in equivalent La2-xSrxCuO4+y materials are discussed....

  16. Theoretical Study on Electronic, Optical Properties and Hardness of Technetium Phosphides under High Pressure

    Directory of Open Access Journals (Sweden)

    Shiquan Feng

    2017-06-01

    Full Text Available In this paper, the structural properties of technetium phosphides Tc3P and TcP4 are investigated by first principles at zero pressure and compared with the experimental values. In addition, the electronic properties of these two crystals in the pressure range of 0–40 GPa are investigated. Further, we discuss the change in the optical properties of technetium phosphides at high pressures. At the end of our study, we focus on the research of the hardness of TcP4 at different pressures by employing a semiempirical method, and the effect of pressure on the hardness is studied. Results show that the hardness of TcP4 increases with the increasing pressure, and the influence mechanism of pressure effect on the hardness of TcP4 is also discussed.

  17. Superconducting doped topological materials

    Energy Technology Data Exchange (ETDEWEB)

    Sasaki, Satoshi, E-mail: sasaki@sanken.osaka-u.ac.jp [Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka 567-0047 (Japan); Mizushima, Takeshi, E-mail: mizushima@mp.es.osaka-u.ac.jp [Department of Materials Engineering Science, Osaka University, Toyonaka, Osaka 560-8531 (Japan); Department of Physics, Okayama University, Okayama 700-8530 (Japan)

    2015-07-15

    Highlights: • Studies on both normal- and SC-state properties of doped topological materials. • Odd-parity pairing systems with the time-reversal-invariance. • Robust superconductivity in the presence of nonmagnetic impurity scattering. • We propose experiments to identify the existence of Majorana fermions in these SCs. - Abstract: Recently, the search for Majorana fermions (MFs) has become one of the most important and exciting issues in condensed matter physics since such an exotic quasiparticle is expected to potentially give rise to unprecedented quantum phenomena whose functional properties will be used to develop future quantum technology. Theoretically, the MFs may reside in various types of topological superconductor materials that is characterized by the topologically protected gapless surface state which are essentially an Andreev bound state. Superconducting doped topological insulators and topological crystalline insulators are promising candidates to harbor the MFs. In this review, we discuss recent progress and understanding on the research of MFs based on time-reversal-invariant superconducting topological materials to deepen our understanding and have a better outlook on both the search for and realization of MFs in these systems. We also discuss some advantages of these bulk systems to realize MFs including remarkable superconducting robustness against nonmagnetic impurities.

  18. High temperature interface superconductivity

    Energy Technology Data Exchange (ETDEWEB)

    Gozar, A., E-mail: adrian.gozar@yale.edu [Yale University, New Haven, CT 06511 (United States); Bozovic, I. [Yale University, New Haven, CT 06511 (United States); Brookhaven National Laboratory, Upton, NY 11973 (United States)

    2016-02-15

    Highlight: • This review article covers the topic of high temperature interface superconductivity. • New materials and techniques used for achieving interface superconductivity are discussed. • We emphasize the role played by the differences in structure and electronic properties at the interface with respect to the bulk of the constituents. - Abstract: High-T{sub c} superconductivity at interfaces has a history of more than a couple of decades. In this review we focus our attention on copper-oxide based heterostructures and multi-layers. We first discuss the technique, atomic layer-by-layer molecular beam epitaxy (ALL-MBE) engineering, that enabled High-T{sub c} Interface Superconductivity (HT-IS), and the challenges associated with the realization of high quality interfaces. Then we turn our attention to the experiments which shed light on the structure and properties of interfacial layers, allowing comparison to those of single-phase films and bulk crystals. Both ‘passive’ hetero-structures as well as surface-induced effects by external gating are discussed. We conclude by comparing HT-IS in cuprates and in other classes of materials, especially Fe-based superconductors, and by examining the grand challenges currently laying ahead for the field.

  19. Study of the superconducting properties of the new intermetallic compound {{Zr}}_{1-x}{{Nb}}_{x}{B}_{2}

    Science.gov (United States)

    Marques, M. D. R.; Portela, F. S.; Corredor, L. T.; Zhang, G.; Vanacken, J.; Moshchalkov, V. V.; Correa, L. E.; Renosto, S. T.; Cigarroa, O.; Machado, A. J. S.; Aguiar, J. Albino

    2016-09-01

    In this paper we report on the synthesis and the structural, electrical, magnetic and thermal analysis for the new material {{{Zr}}}1-x{{{Nb}}}x{{{B}}}2 (0.01 ≤slant x ≤slant 0.05). A superconducting transition was observed for all x values studied, despite the non-superconducting matrix ZrB2, which indicates that the superconducting state is induced by the presence of Nb. The results show that the critical temperature increases with Nb content, reaching its maximum (T c = 8.1 K) for x = 0.04. From the specific heat data we find a Sommerfeld constant of γ = 1.6 mJ molK-2 and a Debye temperature of {θ }D = 615.5 K. Unconventional behaviors are observed in specific heat dependence with temperature and in {H}{{c}1}(T) diagram. These behaviors are investigated in {C}{{e}}/T versus T curve, where an upturn appears for T\\lt 2.3 K, and in {ln}({C}{{e}}/γ {T}{{c}}) versus {T}{{c}}/T dependence, which shows a clear deviation from BCS theory for low temperatures. Also, contrary to the conventional theories we found a positive curvature for temperatures near T c in the lower critical field, besides an upturn around 2.3 K. We suggest that these behaviors possibly arise from multiband superconductivity in {{Zr}}0.96{{Nb}}0.04{{{B}}}2.

  20. Properties of cryocooler-cooled superconductive pulse coil (1); Chokureishiki chodendo parusu koiru no tokusei hyoka (1)

    Energy Technology Data Exchange (ETDEWEB)

    Hae, T.; Kajikawa, K.; Iwakuma, M.; Funaki, K. [Kyushu Univ., Fukuoka (Japan); Hayashi, H.; Tsutsumi, K. [Kyushu Electric Power Co., Inc., Fukuoka (Japan); Tomioka, A.; Konno, M.; Nose, S. [Fuji Electric Corp., Tokyo (Japan)

    1999-11-10

    We manufactured the pulse coil of refrigerating machine direct cooling system using oxide superconducting wire rod, and they succeeded in triangular wave continuous running of 1T and 1Hz. It aimed at future further scale-up using this pulse coil this time, and the relationship between heat quantity and coil temperature rise in the operation was evaluated. (NEDO)

  1. High pressure studies on nanometer sized clusters: Structural, optical, and cooperative properties

    Energy Technology Data Exchange (ETDEWEB)

    Tolbert, S.H.

    1995-05-01

    High-pressure Se EXAFS is used to study pressure-induced structural transformations in CdSe nanocrystals. The transformation is wurtzite to rock salt, at a pressure much higher than in bulk. High-pressure XRD is used to confirm the EXAFS results. Diffraction peak widths indicate that nanocrystals do not fragment upon transformation. Optical absorption correlates with structural transformations and is used to measure transition pressures; transformation pressure increases smoothly as nanocrystal size decreases. Thermodynamics of transformation is modeled using an elevated surface energy in the high-pressure phase. High-pressure study of Si nanocrystals show large increases in transformation pressure in crystallites to 500{angstrom} diameter, and an overall change in crystallite shape upon transformation is seen from XRD line widths. C{sub 60} single crystals were studied using Raman scattering; results provide information about the clusters` rotational state. Optical properties of high-pressure phase CdSe clusters were studied.

  2. Investigation of the superconducting and normal state properties of the filled-skutterudite system PrPt4Ge12 via chemical substitution

    Science.gov (United States)

    Jeon, Inho; Huang, Kevin; Yazici, Duygu; Kanchanavatee, Noravee; White, Benjamin D.; Jang, Sooyoung; Pouse, Naveen; Maple, M. Brian; Ho, Pei-Chun

    We report a systematic chemical substitution study on the unconventional superconductor system PrPt4Ge12, which Sb ions are substituted for Ge. Polycrystalline samples of PrPt4Ge12-x Sbx up to x = 5 were synthesized and investigated by means of x-ray diffraction, electrical resistivity, magnetic susceptibility, and specific heat measurements. We observed a suppression of superconductivity with increasing Sb substitutions and evidence for a weak ``rattling'' mode associated with the Pr ions, characterized by a value of ΘE ~ 60 K. As part of a systematic study of the effect of various elemental substitutions on the properties of PrPt4Ge12, measurements of the superconducting and normal state properties of the Pr1-xEuxPt4Ge12 system are currently being performed. This work was supported by the U. S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Grant No. DE-FG02-04-ER46105 (characterization and physical properties measurements), and the National Science Foundation under Grant No. DMR 1206553 (low-temperature measurements).

  3. Pressure-dependent dielectric properties in a polyurethane elastomer

    Science.gov (United States)

    Hwang, Seung Won; Shin, Jae Sup; Shin, Min Jae; Kim, Chy Hyung

    2017-04-01

    The dielectric responses of polyurethane films were investigated in the pressure range from atmospheric to 20 kpsi and in the frequency range from 0.05 Hz to 4 KHz at -50, 0, 29, 50, and 80 ° C, where T g is close to -15 ° C (α-relaxation) and where the glass temperature of the chain extender is about 80 ° C (I-relaxation). When a higher pressure was applied to the material, a lower dielectric constant (k' ) was obtained owing to the suppression of polarization motions by the external pressure. However, k' increased with rising pressure at temperatures above 50 ° C and at high frequencies due to the predominant thermal effect expanding the film outwards, where a dispersive α-relaxation occurred. Both α- and I-relaxations followed the pressure-frequency superposition principle with a different shifting factor, a( p), where the α-relaxation showed a faster migration of the relaxation time with changing pressure and a( p) values larger than those of I-relaxation. The two relaxations observed at 29 ° C demonstrated linear relations between 1/k' and pressure and between ln a( p) and pressure, regardless of the film thickness.

  4. Pressure-stabilized hafnium nitrides and their properties

    Science.gov (United States)

    Zhang, Jin; Oganov, Artem R.; Li, Xinfeng; Niu, Haiyang

    2017-01-01

    We report hafnium nitrides under pressure using first-principles evolutionary calculations. Metallic P 63/m m c -HfN (calculated Vickers hardness 23.8 GPa) is found to be more energetically favorable than NaCl-type HfN at zero and high pressure. Moreover, NaCl-type HfN actually undergoes a phase transition to P 63/m m c -HfN below 670 K at ambient pressure. HfN10, which simultaneously has infinite armchairlike polymeric N chains and N2 molecules in its crystal structure, is discovered to be stable at moderate pressure above 23 GPa and can be preserved as a metastable phase at ambient pressure. At ambient conditions (298 K, 0 GPa), the gravimetric energy densities and the volumetric energy densities of HfN10 are 2.8 kJ/g and 14.1 kJ/cm3, respectively.

  5. Superconducting interfaces between insulating oxides.

    Science.gov (United States)

    Reyren, N; Thiel, S; Caviglia, A D; Kourkoutis, L Fitting; Hammerl, G; Richter, C; Schneider, C W; Kopp, T; Rüetschi, A-S; Jaccard, D; Gabay, M; Muller, D A; Triscone, J-M; Mannhart, J

    2007-08-31

    At interfaces between complex oxides, electronic systems with unusual electronic properties can be generated. We report on superconductivity in the electron gas formed at the interface between two insulating dielectric perovskite oxides, LaAlO3 and SrTiO3. The behavior of the electron gas is that of a two-dimensional superconductor, confined to a thin sheet at the interface. The superconducting transition temperature of congruent with 200 millikelvin provides a strict upper limit to the thickness of the superconducting layer of congruent with 10 nanometers.

  6. Some specifics of influence of pore pressure on physical properties of deformable rocks

    Science.gov (United States)

    Sobolev, G. A.; Stakhovskaya, Z. I.; Mikayelyan, A. O.

    1984-07-01

    A study was made of a range of problems related to the physical and mechanical properties of limestones from the region of the Ingura hydroelectric powerplant under hydrostatic pore pressure with additional axial pressure. The purpose was to estimate the significance and effect of pore pressure on physical properties in rocks as a function of the stressed state under conditions of hydrostatic pressure and hydrostatic pressure with additional axial loading. The P wave velocity, resistivity and longitudinal deformation were measured under pressure with specimens which had been carefully dried and saturated under vacuum conditions with a 2 n solution of NaCl. Cyclical variations of pore pressure were found to cause compaction of the rock. Cyclical variations of pore pressure under complex stress conditions facilitate fracture and strength loss of the rock.

  7. Extreme pressure properties investigation of palm olein using four ball tribotester

    Science.gov (United States)

    Khairuldean, A. K.; Ing, T. Chiong; Che Kob, Mohd Salman; Budianto, Aries; Bambang, S.; Baharin, T. Kamarul; Ariyono, S.; Syahrullail, S.

    2012-06-01

    This experiment conducted using Four Ball Tribotester as a tool to obtained data for extreme pressure properties of Refined, Bleached, and Deodorized (RBD) Palm Olein. In this paper, test method ASTM D2783 - 03 (Reapproved 2009) been adapted to monitor the pressure effect in wear and frictional torque of RBD Palm Olein. This test method provides reliable information because it resemble to the eventual mechanisms for lubricating stress of the fluids under pressure similar in gear transmission operation. Wherein, pressure applied between surface to surface contacts and sliding between surface in gear and wet clutch mechanism. From this research, the results provide an understanding of RBD Palm Olein performance against extreme pressure condition. It was found that RBD Palm Olein oil has good mild extreme pressure properties, but film breakdown occurs at higher pressure load. The frictional torque results also indicated with pressure increment, the friction force occurs between moving bodies also increase.

  8. Suppression of magnetism and development of superconductivity within the collapsed tetragonal phase of Ca[subscript 0.67]Sr[subscript 0.33]Fe[subscript 2]As[subscript 2] under pressure

    Energy Technology Data Exchange (ETDEWEB)

    Jeffries, J.R.; Butch, N.P.; Kirshenbaum, K.; Saha, S.R.; Samudrala, G.; Weir, S.T.; Vohra, Y.K.; Paglione, J. (LLNL); (UAB); (Maryland)

    2012-10-24

    Structural and electronic characterizations of (Ca{sub 0.67}Sr{sub 0.33})Fe{sub 2}As{sub 2} have been performed as a function of pressure up to 12 GPa using conventional and designer diamond anvil cells. The compound (Ca{sub 0.67}Sr{sub 0.33})Fe{sub 2}As{sub 2} behaves intermediately between its end members, displaying a suppression of magnetism and the onset of superconductivity. Like other members of the AFe{sub 2}As{sub 2} family, (Ca{sub 0.67}Sr{sub 0.33})Fe{sub 2}As{sub 2} undergoes a pressure-induced isostructural volume collapse, which we associate with the development of As-As bonding across the mirror plane of the structure. This collapsed tetragonal phase abruptly cuts off the magnetic state and supports superconductivity with a maximum T{sub c} = 22.2 K. The maximum T{sub c} of the superconducting phase is not strongly correlated with any structural parameter, but its proximity to the abrupt suppression of magnetism as well as the volume-collapse transition suggests that magnetic interactions and structural inhomogeneity may play a role in its development.

  9. Effect of the laser sputtering parameters on the orientation of a cerium oxide buffer layer on sapphire and the properties of a YBa2Cu3Ox superconducting film

    DEFF Research Database (Denmark)

    Mozhaev, P. B.; Ovsyannikov, G. A.; Skov, Johannes

    1999-01-01

    The effect of the laser sputtering parameters on the crystal properties of CeO2 buffer layers grown on a (1 (1) under bar 02) sapphire substrate and on the properties of superconducting YBa2Cu3Ox thin films are investigated. It is shown that (100) and (111) CeO2 growth is observed, depending...

  10. A study on the superconducting properties of YBa{sub 2}Cu{sub 9-x}Nb{sub x}O{sup y} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Srinivas, S.; Bhatnagar, A.K. [Univ. of Hyderabad (India); Pinto, R. [Solid State Electronics Group, Bombay (India)] [and others

    1994-12-31

    Effect of niobium substitution at the copper site in YBa{sub 2}Cu{sub 9}O{sub 7-x} was studied in thin film form. The films were deposited by laser ablation technique using the targets of the YBa{sub 2}Cu{sub 3-x}Nb{sub x}O{sub y} where x = 0.0, 0.025, 0.05, 0.1, 0.2, 0.4, 0.8 and 1.0 under identical deposition conditions on SrTiO{sub 9} <100> substrates. Films were characterized by XRD, resistivity, I-V and J{sub c} measurements. Films made from x = 0.025 and 0.05 concentrations of Nb substituted targets showed relatively improved superconducting properties compared to that of undoped films. The best 7 realized for x = 0.025 Nb concentration was 1.8 x 10{sup {sigma}} A/cm{sup 2} and for 0.05 Nb concentration it was 3.2x10{sup {sigma}} A/cm{sup 2} at 77K. However, degradation of the superconducting properties, with the increase of x {ge} 0.1 Nb concentration and drastic suppression and complete loss of superconductivity was noticed for x {ge} 0.4. The growth of impurity phase YBa{sub 2}NbO{sub 6} for x = 0.1 and above of Nb concentration was noticed from XRD patterns. However, the site occupancy of Nb could not be confirmed from these studies.

  11. Some Properties of topological pressure on cellular automata

    Directory of Open Access Journals (Sweden)

    Chih-Hung Chang

    2014-09-01

    Full Text Available This paper investigates the ergodicity and the power rule of the topological pressure of a cellular automaton. If a cellular automaton is either leftmost or rightmost premutive (due to the terminology given by Hedlund [Math.~Syst.~Theor.~3, 320-375, 1969], then it is ergodic with respect to the uniform Bernoulli measure. More than that, the relation of topological pressure between the original cellular automaton and its power rule is expressed in a closed form. As an application, the topological pressure of a linear cellular automaton can be computed explicitly.

  12. Y-Ba Superconducting Ceramics

    Science.gov (United States)

    Shunbao, Tian; Xiaofei, Li; Tinglian, Wen; Zuxiang, Lin; Shichun, Li; Huijun, Yu

    Polycrystalline Y-Ba-Cu-O superconducting materials have been studied. It was found that chemical composition and processing condition may play an important role in the final structure and superconducting properties. The density has been determined and compared with the calculated value according to the structure model reported by Bell Labs. The grain size and the morphology of the materials were observed by SEM.

  13. Controlling dielectric and pyroelectric properties of compositionally graded ferroelectric rods by an applied pressure

    Science.gov (United States)

    Zheng, Yue; Woo, C. H.; Wang, Biao

    2007-06-01

    The polarization, charge offset, dielectric, and pyroelectric properties of a compositionally graded ferroelectric rod inside a high-pressure polyethylene tube are studied using a thermodynamic model based on the Landau-Ginzburg-Devonshire formulation. The calculated distribution of the polarization in the rod is nonuniform, and the corresponding charge offset, dielectric, and pyroelectric properties vary according to the applied pressure. This behavior may be used as a convenient means to control these properties for design optimization.

  14. Synthesis and study of the magnetic properties of thallium-based over-doped superconducting compounds; Synthese et etude des proprietes magnetiques des composes supraconducteurs surdopes a base de thallium

    Energy Technology Data Exchange (ETDEWEB)

    Opagiste, C.

    1994-07-01

    The synthesis, structure and magnetic properties of the normal and superconducting states of over-doped Tl{sub 2} Ba{sub 2} Cu O{sub 6{+-}x} and Tl{sub 2} Ba{sub 2} Ca Cu{sub 2} O{sub 8{+-}x} superconducting compounds, are presented. Synthesis under high pressure using Tl{sub 2} Ba{sub 2} O{sub 5} as a precursor avoids thallium losses and Ba Cu O{sub 2} formation. The entire over-doped region has been investigated (Tc ranging from 0 to 92 K) and the different stability zones for the two crystallographic structures have been explored. The orthorhombic structure is shown to be stoichiometric in cations, while the tetragonal one could present thallium deficiency. Clear correlations have been established between Tc and the lattice parameters for the two phases. It has been observed that the Meissner fraction increased with Tc and that the reversibility domain was more extended for samples having a Tc near the maximal value, which must be linked to the decrease of the anisotropy with over-doping. In the reversible regime, the mixed state is affected by thermal fluctuations around Tc. Evolution of the penetration depth with Tc is examined; it shows that the optimum doped compound (maximal Tc) behaves as a BCS type superconductor. The over-doping results in a penetration depth behaviour which strongly deviates from the standard model (BCS, two fluids). The zero temperature, obtained by extrapolation, seems to be independent of the over-doping. 54 figs., 3 tabs., 168 refs.

  15. Substitution effects on superconducting and normal state properties in (Mo1-xTx)3Sb7, where T = Ru and Fe

    Science.gov (United States)

    Tran, V. H.

    2016-12-01

    The effects of Ru- and Fe-doping on the physical properties of Mo3Sb7 were studied by measuring ac-susceptibility, dc-magnetization, electrical resistivity and specific heat. It is found that single-phased (Mo{}1-xRu x )3Sb7 and (Mo{}1-xFe x )3Sb7 samples are obtained for the concentrations x ≤slant 0.1. In this concentration range, the lattice parameter shrinks with increasing dopant content. The substitution effects on the superconducting and normal state properties are completely different between two investigated systems. In the Ru-based solid solution alloys, the substitution enhances the superconducting parameters T c and H c2 and also benefits the spin-gap opening at {T}* ˜ 50 K. In contrast, in the Fe-substituted samples, there is a depression of both T c and H c2, accompanied by vanishing spin-gap and low-dimensional magnetic correlation. The substitution of the Mo atoms by Ru and Fe atoms suppresses the cubic-tetragonal distortion, but presumably favours the magnetic field to induce a magnetic order below T *.

  16. Magnetic and superconducting properties of a heavy-fermion CeCoIn5 epitaxial film probed by nuclear quadrupole resonance

    Science.gov (United States)

    Yamanaka, Takayoshi; Shimozawa, Masaaki; Shishido, Hiroaki; Kitagawa, Shunsaku; Ikeda, Hiroaki; Shibauchi, Takasada; Terashima, Takahito; Matsuda, Yuji; Ishida, Kenji

    2017-08-01

    Since the progress in the fabrication techniques of thin films of exotic materials such as strongly correlated heavy-fermion compounds, microscopic studies of the magnetic and electronic properties inside the films have been needed. Herein, we report the observation of 115In nuclear quadrupole resonance (NQR) in an epitaxial film of the heavy-fermion superconductor CeCoIn5, for which the microscopic field gradient within the unit cell as well as magnetic and superconducting properties at zero field are evaluated. We find that the nuclear spin-lattice relaxation rate in the film is in excellent agreement with that of bulk crystals, whereas the NQR spectra show noticeable shifts and significant broadening indicating a change in the electric-field distribution inside the film. The analysis implies a displacement of In layers in the film, which, however, does not affect the magnetic fluctuations and superconducting pairing. This implies that inhomogeneity of the electronic field gradient in the film sample causes no pair-breaking effect.

  17. Transport and infrared properties of SmFeAs(O{sub 1-x}F{sub x}): from SDW to superconducting ordering

    Energy Technology Data Exchange (ETDEWEB)

    Tropeano, M; Fanciulli, C; Ferdeghini, C; Marre, D; Siri, A S; Putti, M [CNR-INFM-LAMIA and Dipartimento di Fisica, Via Dodecaneso 33, I-16146 Genova (Italy); Martinelli, A; Ferretti, M; Palenzona, A [CNR-INFM-LAMIA and Dipartimento di Chimica e Chimica Industriale, Via Dodecaneso 31, I-16146 Genova (Italy); Cimberle, M R [CNR-IMEM, Dipartimento di Fisica, Via Dodecaneso 33, I-16146 Genova (Italy); Mirri, C; Lupi, S; Sopracase, R; Calvani, P [CNR-INFM ' Coherentia' and Dipartimento di Fisica, Universita di Roma ' La Sapienza' , Piazzale Aldo Moro 2, I-00185 Rome (Italy); Perucchi, A [Sincrotrone Trieste S.C.p.A., S.S. 14 km 163.5, Area Science Park, I-34012 Basovizza, Trieste (Italy)

    2009-03-15

    We report measurements of resistivity, magnetoresistivity, Hall effect, Seebeck coefficient and infrared reflectivity of undoped SmFeAsO and lightly doped SmFeAs(O{sub 0.93}F{sub 0.07}) oxypnictides. All the properties measured on SmFeAsO are characterized by clear signatures of the magnetic instability. A self-consistent picture emerges in which carrier condensation occurs below the magnetic transition, due to the opening of a spin density wave (SDW) gap. This is accompanied by the mobility increase of not-gapped carriers due to the suppression of electron-electron scattering. SmFeAs(O{sub 0.93}F{sub 0.07}) exhibits an increase of the metallic character on cooling consistent with electron doping, even though at room temperature values of all the properties nearly overlap with those of SmFeAsO. However, with a decrease in temperature all anomalies related to the SDW instability are missing and the superconducting transition occurs. This suggests that doping abruptly breaks the symmetries of the Fermi surface, inhibiting the SDW formation in favor of the superconducting transition, with no substantial changes in the density of states or in the effective mass.

  18. Electronic, thermal, and superconducting properties of metal nitrides (MN) and metal carbides (MC) (M=V, Nb, Ta) compounds by first principles studies

    Energy Technology Data Exchange (ETDEWEB)

    Subhashree, G.; Sankar, S.; Krithiga, R. [Anna Univ., Chennai, Tamil Nadu (India). Condensed Matter Lab.

    2015-07-01

    Structural, electronic, and superconducting properties of carbides and nitrides of vanadium (V), niobium (Nb), and tantalum (Ta) (group V transition elements) have been studied by computing their electronic band structure characteristics. The electronic band structure calculations have been carried out based on the density functional theory (DFT) within the local density approximation (LDA) by using the tight binding linear muffin tin orbital method. The NaCl-type cubic structures of MN and MC (M=V, Nb, Ta) compounds have been confirmed from the electronic total energy minimum of these compounds. The ground state properties, such as equilibrium lattice constant (a{sub 0}), bulk modulus (B), and Wigner-Seitz radius (S{sub 0}) are determined and compared with available data. The electronic density of states reveals the metallic nature of the chosen materials. The electronic specific heat coefficient, Debye temperature, and superconducting transition temperature obtained from the band structure results are found to agree well with the earlier reported literature.

  19. Dependency of hydromechanical properties of monzonitic granite on confining pressure and fluid pressure under compression

    Science.gov (United States)

    Wang, Huanling; Xu, Weiya; Lui, Zaobao; Chao, Zhiming; Meng, Qingxiang

    2016-05-01

    Monzonitic granite is a low-permeability rock. Monzonitic granite formations are ideal for underground storage of oil due to their low permeability and high mechanical strength. In this study, a series of coupled hydromechanical triaxial tests are carried out using monzonitic granite specimens. The influence of confining and fluid pressures on stress, strain, and permeability is investigated. Failure characteristics under different confining and fluid pressures are discussed based on the analysis of macro fracture planes and micro scanning electron microscopy (SEM). The test results show that the change of permeability with stress and strain reflects the deformation stages of compaction, compression, crack propagation, coalesce, and failure of cracks. Due to the low porosity, the change of permeability is small in the initial phases of compaction and compression, whereas there is a significant increase in permeability when new cracks start to develop and coalesce. Confining pressures have a significant impact on the strength and permeability, particularly the crack damage stress of the rock. Compared with confining pressure, the effect of fluid pressure on rock strength and crack damage stress is small. For the monzonitic granite specimens tested, changing the confining pressure results in different failure modes, whereas the fluid pressure has a relatively small effect on the failure modes.

  20. Superconductivity in doped Dirac semimetals

    Science.gov (United States)

    Hashimoto, Tatsuki; Kobayashi, Shingo; Tanaka, Yukio; Sato, Masatoshi

    2016-07-01

    We theoretically study intrinsic superconductivity in doped Dirac semimetals. Dirac semimetals host bulk Dirac points, which are formed by doubly degenerate bands, so the Hamiltonian is described by a 4 ×4 matrix and six types of k -independent pair potentials are allowed by the Fermi-Dirac statistics. We show that the unique spin-orbit coupling leads to characteristic superconducting gap structures and d vectors on the Fermi surface and the electron-electron interaction between intra and interorbitals gives a novel phase diagram of superconductivity. It is found that when the interorbital attraction is dominant, an unconventional superconducting state with point nodes appears. To verify the experimental signature of possible superconducting states, we calculate the temperature dependence of bulk physical properties such as electronic specific heat and spin susceptibility and surface state. In the unconventional superconducting phase, either dispersive or flat Andreev bound states appear between point nodes, which leads to double peaks or a single peak in the surface density of states, respectively. As a result, possible superconducting states can be distinguished by combining bulk and surface measurements.

  1. Superconducting Microelectronics.

    Science.gov (United States)

    Henry, Richard W.

    1984-01-01

    Discusses superconducting microelectronics based on the Josephson effect and its advantages over conventional integrated circuits in speed and sensitivity. Considers present uses in standards laboratories (voltage) and in measuring weak magnetic fields. Also considers future applications in superfast computer circuitry using Superconducting…

  2. Formation of Nanofoam carbon and re-emergence of Superconductivity in compressed CaC6.

    Science.gov (United States)

    Li, Yan-Ling; Luo, Wei; Chen, Xiao-Jia; Zeng, Zhi; Lin, Hai-Qing; Ahuja, Rajeev

    2013-11-26

    Pressure can tune material's electronic properties and control its quantum state, making some systems present disconnected superconducting region as observed in iron chalcogenides and heavy fermion CeCu2Si2. For CaC6 superconductor (Tc of 11.5 K), applying pressure first Tc increases and then suppresses and the superconductivity of this compound is eventually disappeared at about 18 GPa. Here, we report a theoretical finding of the re-emergence of superconductivity in heavily compressed CaC6. The predicted phase III (space group Pmmn) with formation of carbon nanofoam is found to be stable at wide pressure range with a Tc up to 14.7 K at 78 GPa. Diamond-like carbon structure is adhered to the phase IV (Cmcm) for compressed CaC6 after 126 GPa, which has bad metallic behavior, indicating again departure from superconductivity. Re-emerged superconductivity in compressed CaC6 paves a new way to design new-type superconductor by inserting metal into nanoporous host lattice.

  3. Comparison of structural transformations and superconductivity in compressed sulfur and selenium

    Energy Technology Data Exchange (ETDEWEB)

    Rudin, Sven P.; Liu, Amy Y.; Freericks, J. K.; Quandt, Alexander

    2001-06-01

    Density-functional calculations are presented for high-pressure structural phases of S and Se. The structural phase diagrams, phonon spectra, electron-phonon coupling, and superconducting properties of the isovalent elements are compared. We find that with increasing pressure, Se adopts a sequence of ever more closely packed structures ({beta}-Po, bcc, fcc), while S favors more open structures ({beta}-Po, simple cubic, bcc). These differences are shown to be attributable to differences in the S and Se core states. All the compressed phases of S and Se considered are calculated to have weak to moderate electron-phonon coupling strengths consistent with superconducting transition temperatures in the range of 1 to 20 K. Our results compare well with experimental data on the {beta}-Po{r_arrow}bcc transition pressure in Se and on the superconducting transition temperature in {beta}-PoS. Further experiments are suggested to search for the other structural phases predicted at higher pressures and to test theoretical results on the electron-phonon interaction and superconducting properties.

  4. Impact of pressure on physicochemical properties of starch dispersions

    KAUST Repository

    Yang, Zhi

    2016-09-02

    High hydrostatic pressure (HHP) can be employed as a non-thermal sterilization technique in the food industry while inducing structure and physicochemical changes of the food macromolecules like starch. The effect of HHP on starch depends on various factors including starch type and concentration, pressurization temperature, time, and suspending media. In this review, we summarize the influence of HHP on the structure, gelatinization, retrogradation, and modification of starches from different botanical origins. Suggestions for future research are provided to better understand the mechanism of HHP on starch, and on how HHP can be used in the starch industry. © 2016 Elsevier Ltd.

  5. Superconductivity and mechanical properties of SmBa2Cu3O7-δ added with nano-crystalline ZnFe2O4

    Science.gov (United States)

    Abdeen, W.; El Tahan, A.; Awad, R.; Abou Aly, A. I.; El-Maghraby, E. M.; Khalaf, A.

    2016-06-01

    The effect of nanosized ZnFe2O4 addition on the physical properties of polycrystalline SmBa2Cu3O7-δ superconductor was studied. Superconducting samples of the type (ZnFe2O4) x SmBa2Cu3O7-δ, x = 0.00, 0.01, 0.02, 0.04, 0.06, 0.08, 0.10, 0.15 and 0.20 wt% were prepared by the solid-state reaction method. The characterization and superconductivity investigation were carried out using X-ray powder diffraction, XRD, scanning electron microscope, SEM, energy-dispersive X-ray, EDX, dc electrical resistivity and transport critical current density at 77 K. Improvements in the volume fraction, superconducting transition temperature, Tc, and transport critical current density, Jc, were observed as x increased from 0.00 up to 0.08 wt% and then they decreased with further increase in nanosized ZnFe2O4 addition. The Vickers microhardness number, H v, and elastic parameters have been measured at room temperature. The ultrasonic pulse-echo technique at 4 MHz was used to determine the elastic parameters. H v and the elastic parameters were observed to increase with increasing x. The enhancement of the elastic parameters may be due to the hindrance of dislocation motion with nanosized ZnFe2O4 addition. Moreover, Debye temperatures ( θ D) were calculated and it was found that their values increased with increasing nanosized ZnFe2O4 addition. The elastic parameters of the samples were computed and corrected to zero porosity using different models. Finally, the relationship between Young's modulus and H v was estimated for different models.

  6. Induced spin-triplet pairing in the coexistence state of antiferromagnetism and singlet superconductivity: Collective modes and microscopic properties

    Science.gov (United States)

    Almeida, D. E.; Fernandes, R. M.; Miranda, E.

    2017-07-01

    The close interplay between superconductivity and antiferromagnetism in several quantum materials can lead to the appearance of an unusual thermodynamic state in which both orders coexist microscopically, despite their competing nature. A hallmark of this coexistence state is the emergence of a spin-triplet superconducting gap component, called a π triplet, which is spatially modulated by the antiferromagnetic wave vector, reminiscent of a pair density wave. In this paper, we investigate the impact of these π -triplet degrees of freedom on the phase diagram of a system with competing antiferromagnetic and superconducting orders. Although we focus on a microscopic two-band model that has been widely employed in studies of iron pnictides, most of our results follow from a Ginzburg-Landau analysis, and as such should be applicable to other systems of interest, such as cuprates and heavy fermion materials. The Ginzburg-Landau functional reveals not only that the π -triplet gap amplitude couples trilinearly with the singlet gap amplitude and the staggered magnetization magnitude but also that the π -triplet d -vector couples linearly with the magnetization direction. While in the mean-field level this coupling forces the d -vector to align parallel or antiparallel to the magnetization, in the fluctuation regime it promotes two additional collective modes—a Goldstone mode related to the precession of the d -vector around the magnetization and a massive mode, related to the relative angle between the two vectors, which is nearly degenerate with a Leggett-like mode associated with the phase difference between the singlet and triplet gaps. We also investigate the impact of magnetic fluctuations on the superconducting-antiferromagnetic phase diagram, showing that due to their coupling with the π -triplet order parameter the coexistence region is enhanced. This effect stems from the fact that the π -triplet degrees of freedom promote an effective attraction between

  7. Superconducting Radio Frequency Technology: An Overview

    Energy Technology Data Exchange (ETDEWEB)

    Peter Kneisel

    2003-06-01

    Superconducting RF cavities are becoming more often the choice for larger scale particle accelerator projects such as linear colliders, energy recovery linacs, free electron lasers or storage rings. Among the many advantages compared to normal conducting copper structures, the superconducting devices dissipate less rf power, permit higher accelerating gradients in CW operation and provide better quality particle beams. In most cases these accelerating cavities are fabricated from high purity bulk niobium, which has superior superconducting properties such as critical temperature and critical magnetic field when compared to other superconducting materials. Research during the last decade has shown, that the metallurgical properties--purity, grain structure, mechanical properties and oxidation behavior--have significant influence on the performance of these accelerating devices. This contribution attempts to give a short overview of the superconducting RF technology with emphasis on the importance of the material properties of the high purity niobium.

  8. High-pressure acoustic properties of glycerol studied by Brillouin spectroscopy

    Science.gov (United States)

    Jeong, Min-Seok; Ko, Jae-Hyeon; Ko, Young Ho; Kim, Kwang Joo

    2015-12-01

    Acoustic properties of glycerol was investigated in a wide pressure range from ambient pressure to 30.9 GPa by using a multi-pass Fabry-Perot interferometer and a diamond anvil cell. Pressure dependences of the sound velocity and the Brillouin linewidth showed substantial changes at low pressures below ~4 GPa. This was attributed to the coupling between the main structural relaxation process and the longitudinal acoustic waves. The pressure dependence of the refractive index and the density of glycerol could be obtained by using two scattering geometries and the Lorentz-Lorenz relation.

  9. High-pressure acoustic properties of glycerol studied by Brillouin spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, Min-Seok [Department of Physics, Hallym University, Chuncheon, Gangwondo 200-702 (Korea, Republic of); Ko, Jae-Hyeon, E-mail: hwangko@hallym.ac.kr [Department of Physics, Hallym University, Chuncheon, Gangwondo 200-702 (Korea, Republic of); Ko, Young Ho; Kim, Kwang Joo [Agency for Defense Development, 4-2-2, P.O. Box 35, Yuseong, Daejeon 305-600 (Korea, Republic of)

    2015-12-01

    Acoustic properties of glycerol was investigated in a wide pressure range from ambient pressure to 30.9 GPa by using a multi-pass Fabry–Perot interferometer and a diamond anvil cell. Pressure dependences of the sound velocity and the Brillouin linewidth showed substantial changes at low pressures below ~4 GPa. This was attributed to the coupling between the main structural relaxation process and the longitudinal acoustic waves. The pressure dependence of the refractive index and the density of glycerol could be obtained by using two scattering geometries and the Lorentz–Lorenz relation.

  10. Superconductivity in all its states

    CERN Multimedia

    Globe Info

    2011-01-01

    Temporary exhibition at the Saint-Genis-Pouilly Tourist Office. For the 100th anniversary of its discovery, take a plunge into the amazing world of superconductivity. Some materials, when cooled down to extreme temperatures, acquire a remarkable property -  they become superconducting. Superconductivity is a rare example of a quantum effect that can be witnessed on the macroscopic scale and is today at the heart of much research. In laboratories, researchers try to gain a better understanding of its origins, study new superconducting materials, explore the phenomenon at the nanometric scale and pursue their indefatigable search for new applications. Monday to Friday: 09:00 a.m. to 12:00 and 2:30 p.m. to 6:30 p.m. Saturday: 10:00 a.m. to 12:00 noon » Open to all – Admission free For further information: +33 (0)4 50 42 29 37

  11. Superconductivity in Layered Organic Metals

    Directory of Open Access Journals (Sweden)

    Jochen Wosnitza

    2012-04-01

    Full Text Available In this short review, I will give an overview on the current understanding of the superconductivity in quasi-two-dimensional organic metals. Thereby, I will focus on charge-transfer salts based on bis(ethylenedithiotetrathiafulvalene (BEDT-TTF or ET for short. In these materials, strong electronic correlations are clearly evident, resulting in unique phase diagrams. The layered crystallographic structure leads to highly anisotropic electronic as well as superconducting properties. The corresponding very high orbital critical field for in-plane magnetic-field alignment allows for the occurrence of the Fulde–Ferrell– Larkin–Ovchinnikov state as evidenced by thermodynamic measurements. The experimental picture on the nature of the superconducting state is still controversial with evidence both for unconventional as well as for BCS-like superconductivity.

  12. Crystal structure, superconductivity and magnetic properties of the superconducting ferromagnets Gd{sub 1.4-x}Dy{sub x}Ce{sub 0.6}Sr{sub 2}RuCu{sub 2}O{sub 10} (x=0-0.6)

    Energy Technology Data Exchange (ETDEWEB)

    Kalavathi, S.; Janaki, J.; Reddy, G.V.R.; Rao, G.V.N.; Sankara Sastry, V.; Hariharan, Y

    2003-07-15

    The structural, electrical and magnetic properties of the superconducting ferromagnets, Gd{sub 1.4-x}Dy{sub x}Ce{sub 0.6}Sr{sub 2}RuCu{sub 2}O{sub 10} (x=0-0.6) are systematically investigated as a function of Dy doping and temperature. These compounds are characterized by high temperature superconductivity (T{sub c} ranging from 20 to 40 K depending upon the Dy content) co-existing with weak ferromagnetism with two magnetic transitions (T{sub M2} ranging from 95 to 106 K and T{sub M1} around 120 K). Doping with Dy gives no significant structural changes except for a minor change in the c/a ratio. However the superconducting transition temperature is significantly suppressed and magnetic ordering temperature enhanced on Dy doping. These effects are described and discussed.

  13. Influence of substitutional disorder on the electrical transport and the superconducting properties of Fe{sub 1+z}Te{sub 1−x−y}Se{sub x}S{sub y}

    Energy Technology Data Exchange (ETDEWEB)

    Rodríguez, M.G. [Laboratorio de Bajas Temperaturas, Departamento de Física, FCEyNUBA and IFIBA-CONICET, Buenos Aires (Argentina); Polla, G.; Ramos, C.P. [Gerencia de Investigación y Aplicaciones, CAC-CNEA, San Martín (Argentina); Acha, C., E-mail: acha@df.uba.ar [Laboratorio de Bajas Temperaturas, Departamento de Física, FCEyNUBA and IFIBA-CONICET, Buenos Aires (Argentina)

    2015-11-15

    We have carried out an investigation of the structural, magnetic, transport and superconducting properties of Fe{sub 1+z}Te{sub 1−x−y}Se{sub x}S{sub y} ceramic compounds, for z = 0 and some specific Se (0 ≤ x ≤ 0.5) and S (0 ≤ y ≤ 0.12) contents. The incorporation of Se and S to the FeTe structure produces a progressive reduction of the crystallographic parameters as well as different degrees of structural disorder associated with the differences of the ionic radius of the substituting cations. In the present study, we measure transport properties of this family of compounds and we show the direct influence of disorder in the normal and superconductor states. We notice that the structural disorder correlates with a variable range hopping conducting regime observed at temperatures T > 200 K. At lower temperatures, all the samples except the one with the highest degree of disorder show a crossover to a metallic-like regime, probably related to the transport of resilient-quasi-particles associated with the proximity of a Fermi liquid state at temperatures below the superconducting transition. Moreover, the superconducting properties are depressed only for that particular sample, in accordance to the condition that superconductivity is affected by disorder when the electronic localization length ξ{sub L} becomes smaller than the coherence length ξ{sub SC}. - Highlights: • New Fe(1 + z)Te(1−x−y)Se(x)S(y) ceramic samples were synthesized. • Structural, magnetic, transport and superconducting properties are presented. • Nonmagnetic disorder determines a VRH conduction regime near room temperature. • Superconductivity is affected by disorder.

  14. High pressure phase determination and electronic properties of lithiumamidoborane

    Science.gov (United States)

    Ramzan, M.; Hussain, T.; Ahuja, R.

    2012-09-01

    In this study we report on the high pressure phase of the promising hydrogen storage material lithiumamidoborane (LiNH2BH3), on the basis of density functional theory calculations with generalized gradient approximation. We take the five possible candidate structures, Pbca, Pbcn, Pcca, Pnma, and Pnnm for the high pressure study of LiNH2BH3. The corresponding structures are relaxed with respect to fractional atomic coordinates and cell parameters, with the use of fully self-consistent ab initio electronic structure calculations to get the equilibrium parameters and total energies. Then we compare the energies of these phases and find that Pbcn is the most favorable phase at ≈100 GPa. Then we calculate the structural parameters of this phase. Finally, we calculate the density of states, Bader charge analysis, and corresponding electron density of this phase.

  15. Anisotropic superconducting and normal state magnetic properties of single crystals of RNi*2*B*2*C compounds (R = Y, Gd, Dy, Ho, Er, and Tm)

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Beongki [Iowa State Univ., Ames, IA (United States)

    1995-09-26

    The interaction of superconductivity with magnetism has been one of the most interesting and important phenomena in solid state physics since the 1950`s when small amounts of magnetic impurities were incorporated in superconductors. The discovery of the magnetic superconductors RNi2B2C (R = rare earth, Y) offers a new system to study this interaction. The wide ranges of superconducting transition (Tc) and antiferromagnetic (AF) ordering temperatures (TN) (0 K ≤ Tc ≤ 16 K, 0 K ≤ TN ≤ 20 K) give a good opportunity to observe a variety of interesting phenomena. Single crystals of high quality with appropriate size and mass are crucial in examining the anisotropic intrinsic properties. Single crystals have been grown successfully by an unusual high temperature flux method and characterized thoroughly by X-ray, electrical transport, magnetization, neutron scattering, scanning electron microscopy, and other measurements.

  16. Structural, elastic and electronic properties of superconducting anti-perovskites MgCNi 3, ZnCNi 3 and CdCNi 3 from first principles

    Science.gov (United States)

    Shein, I. R.; Bannikov, V. V.; Ivanovskii, A. L.

    2008-01-01

    First principle total energy calculations using the full potential linearized augmented plane wave (FP-LAPW) method with the generalized gradient approximation (GGA) for the exchange-correlation potential were performed to investigate the systematic trends for structural, elastic and electronic properties of the family of superconducting anti-perovskites MCNi 3 depending from the type of M cations (M are Mg, Zn and Cd). In result the optimized lattice parameters, independent elastic constants ( C11, C12 and C44), bulk modulus B, compressibility β, shear modulus G and tetragonal shear modulus G‧ are evaluated. Further, for the first time the numerical estimates of a set of elastic parameters (bulk and shear modulus, Young’s modulus Y, Poisson’s ratio ( ν), Lamé’s coefficients ( μ, λ)) of the polycrystalline superconducting MCNi 3 ceramics (in framework of the Voigt-Reuss-Hill approximation) were performed. Besides, the band structures, densities of states (DOS), total and site-projected l-decomposed DOS at the Fermi level, the shapes of the Fermi surfaces, the Sommerfeld’s coefficients and the molar Pauli paramagnetic susceptibility for these anti-perovskites were obtained and analyzed in comparison with the available theoretical and experimental data.

  17. Indium Substitution Effect on the Topological Crystalline Insulator Family (Pb1−xSnx1−yInyTe: Topological and Superconducting Properties

    Directory of Open Access Journals (Sweden)

    Ruidan Zhong

    2017-02-01

    Full Text Available Topological crystalline insulators (TCIs have been of great interest in the area of condensed matter physics. We investigated the effect of indium substitution on the crystal structure and transport properties in the TCI system (Pb1−xSnx1−yInyTe. For samples with a tin concentration x ≤ 50 % , the low-temperature resisitivities show a dramatic variation as a function of indium concentration: with up to ∼2% indium doping, the samples show weak-metallic behavior similar to their parent compounds; with ∼6% indium doping, samples have true bulk-insulating resistivity and present evidence for nontrivial topological surface states; with higher indium doping levels, superconductivity was observed, with a transition temperature, T c , positively correlated to the indium concentration and reaching as high as 4.7 K. We address this issue from the view of bulk electronic structure modified by the indium-induced impurity level that pins the Fermi level. The current work summarizes the indium substitution effect on (Pb,SnTe, and discusses the topological and superconducting aspects, which can be provide guidance for future studies on this and related systems.

  18. ASC 84: applied superconductivity conference. Final program and abstracts

    Energy Technology Data Exchange (ETDEWEB)

    1984-01-01

    Abstracts are given of presentations covering: superconducting device fabrication; applications of rf superconductivity; conductor stability and losses; detectors and signal processing; fusion magnets; A15 and Nb-Ti conductors; stability, losses, and various conductors; SQUID applications; new applications of superconductivity; advanced conductor materials; high energy physics applications of superconductivity; electronic materials and characterization; general superconducting electronics; ac machinery and new applications; digital devices; fusion and other large scale applications; in-situ and powder process conductors; ac applications; synthesis, properties, and characterization of conductors; superconducting microelectronics. (LEW)

  19. Research on Properties of Woven Fabrics Treated by High Pressure Water Jet

    Institute of Scientific and Technical Information of China (English)

    黄故

    2001-01-01

    The paper introduces a new technique for the treatment of the woven fabrics. Sprayed by high pressure water jet, the appearance, handle and stiffness of the fabric are improved. Other properties of the high pressure water treated fabrics like drape coefficient, air permeability, tenacity are also presented.

  20. Influence of additions and radiation damage on the superconducting properties of sintered YBa 2Cu 3O 7 - gd

    Science.gov (United States)

    Koblischka, M. R.; Schuster, Th.; Kronmüller, H.

    1993-06-01

    Using the high-resolution Faraday (HRF) technique, domain patterns of sintered YBa 2Cu 3O 7 - δ samples containing additions of Ag 2O and Y 2BaCuO 5 are obtained. Similar observations are carried out on sintered YBa 2Cu 3O 7- δ samples with reduced oxygen content and on electron-irradiated samples. The penetration of flux into sintered high- Tc superconductors is found to be totally different from single crystalline materials (single crystals and epitaxial thin films) as the Abrikosov vortices penetrate the sample not as a whole thus forming a so-called flux front. Only a flux penetration into single superconducting grains is observed. From the measured flux density profiles, the intragrain critical current densities are determined locally. It is found that the chemical impurity phases do not affect the intragranular flux density distribution and the intragranular critical current density, but the decomposition of the Ag 2O leads to an improved oxygen stoichiometry in these samples. Electron irradiation is found to enhance the intragrain critical current densities, whereas the oxygen reduction leads to reduced intragrain currents. To determine the influence of the additions also on the intergrain critical current densities, standard four-point transport current measurements are carried out on the same samples. It is found that a maximum enhancement of the critical current density is obtained by the addition of 10 wt% silver oxide; however, this critical current density is drastically reduced by applying small external magnetic fields. The lower critical field of the matrix and the corresponding Josephson penetration depth are determined from transport current measurements. The Ag 2O additions and the green phase particles are found to separate the superconducting YBa 2Cu 3O 7- δ grains. The resulting larger widths of the barriers between the superconducting grains are found to cause a stronger influence of external magnetic fields on the intergrain critical

  1. SUPERCONDUCTING PHOTOCATHODES.

    Energy Technology Data Exchange (ETDEWEB)

    SMEDLEY, J.; RAO, T.; WARREN, J.; SEKUTOWICZ, LANGNER, J.; STRZYZEWSKI, P.; LEFFERS, R.; LIPSKI, A.

    2005-10-09

    We present the results of our investigation of lead and niobium as suitable photocathode materials for superconducting RF injectors. Quantum efficiencies (QE) have been measured for a range of incident photon energies and a variety of cathode preparation methods, including various lead plating techniques on a niobium substrate. The effects of operating at ambient and cryogenic temperatures and different vacuum levels on the cathode QE have also been studied.

  2. Electronic and elastic properties of Li{sub 3}N under different pressure

    Energy Technology Data Exchange (ETDEWEB)

    Li Wei, E-mail: tolwwt@163.co [Laboratory of Quantum Information Technology, School of Physics and Telecommunication Engineering, South China Normal University, 510006 Guangzhou (China); Chen Junfang [Laboratory of Quantum Information Technology, School of Physics and Telecommunication Engineering, South China Normal University, 510006 Guangzhou (China); Wang Teng [School of Computer, South China Normal University, 510631 Guangzhou (China)

    2010-01-01

    The electronic structures and elastic properties of lithium nitride are studied using first-principles calculations. The energy band structure and density of state (DOS) of Li{sub 3}N at 0 GPa are calculated. The band gap energy of Li{sub 3}N versus the pressure 0-38.8 GPa is obtained. We find that the band gap energy decreases as the pressure increases. The geometry optimized structural parameters for lithium nitride under different pressures are listed. The parameters a, c, and E all decrease with increasing pressure. However, parameter B, S and Y increase with pressure. The normalized lattice constants and the elastic modulus as two functions of pressure from 0 to 38.8 GPa are obtained. All the calculated elastic constants C{sub ij} increase by different rates with increasing pressure.

  3. Superconductivity an introduction

    CERN Document Server

    Kleiner, Reinhold

    2016-01-01

    The third edition of this proven text has been developed further in both scope and scale to reflect the potential for superconductivity in power engineering to increase efficiency in electricity transmission or engines. The landmark reference remains a comprehensive introduction to the field, covering every aspect from fundamentals to applications, and presenting the latest developments in organic superconductors, superconducting interfaces, quantum coherence, and applications in medicine and industry. Due to its precise language and numerous explanatory illustrations, it is suitable as an introductory textbook, with the level rising smoothly from chapter to chapter, such that readers can build on their newly acquired knowledge. The authors cover basic properties of superconductors and discuss stability and different material groups with reference to the latest and most promising applications, devoting the last third of the book to applications in power engineering, medicine, and low temperature physics. An e...

  4. Superconducting Accelerator Magnets

    CERN Document Server

    Mess, K H; Wolff, S

    1996-01-01

    The main topic of the book are the superconducting dipole and quadrupole magnets needed in high-energy accelerators and storage rings for protons, antiprotons or heavy ions. The basic principles of low-temperature superconductivity are outlined with special emphasis on the effects which are relevant for accelerator magnets. Properties and fabrication methods of practical superconductors are described. Analytical methods for field calculation and multipole expansion are presented for coils without and with iron yoke. The effect of yoke saturation and geometric distortions on field quality is studied. Persistent magnetization currents in the superconductor and eddy currents the copper part of the cable are analyzed in detail and their influence on field quality and magnet performance is investigated. Superconductor stability, quench origins and propagation and magnet protection are addressed. Some important concepts of accelerator physics are introduced which are needed to appreciate the demanding requirements ...

  5. Design Study of Superconducting Coil of 230 MeV Superconducting Cyclotron

    Institute of Scientific and Technical Information of China (English)

    WANG; Chuan; YIN; Meng; ZHANG; Su-ping; LI; Ming; CUI; Tao; LIN; Jun; LV; Yin-long; GE; Tao; YIN; Zhi-guo; ZHANG; Tian-jue

    2015-01-01

    The superconducting coil system of CYCIAE-230superconducting proton cyclotron consists of two coil windings,cryostat,GM coolers,and the liquid helium condenser(Fig.1),along with multiple thermometers,pressure gauges,liquid level gauges,load cells,a vacuum pump,a

  6. Superconductivity in nanowires

    CERN Document Server

    Bezryadin, Alexey

    2012-01-01

    The importance and actuality of nanotechnology is unabated and will be for years to come. A main challenge is to understand the various properties of certain nanostructures, and how to generate structures with specific properties for use in actual applications in Electrical Engineering and Medicine.One of the most important structures are nanowires, in particular superconducting ones. They are highly promising for future electronics, transporting current without resistance and at scales of a few nanometers. To fabricate wires to certain defined standards however, is a major challenge, and so i

  7. Technique for reduction of mechanical losses in AC superconducting coils due to thermal expansion properties of various FRP bobbins

    Science.gov (United States)

    Sekine, N.; Tada, S.; Higuchi, T.; Furumura, Y.; Takao, T.; Yamanaka, A.

    2005-10-01

    We reported about reduction of mechanical losses in AC superconducting coils. The method is the use of FRP bobbins fabricated with special fibers. Since their FRPs have negative thermal expansion coefficient to the fiber direction, the FRP bobbins expand to the circumferential direction during cooling down. In case of the superconducting coils with such FRP bobbins, the winding tensions do not decrease during cooling down. Therefore, the mechanical losses are reduced by the suppression of wire's vibration. Their special FRPs are a Dyneema® fiber reinforced plastic (DFRP), a Dyneema and glass fiber reinforced plastic (DGFRP), and a Zylon® fiber reinforced plastic (ZFRP). These materials have negative thermal expansion coefficient to the fiber direction, however, the amplitudes of thermal expansion are various by the quantity or quality of the fiber. In this paper, the values of thermal expansion were actually measured, and it was discussed about the influence on the mechanical losses. At the experimental results, the mechanical loss was small, so that the thermal strain to the circumferential direction on the coil was large. Moreover, in case of the coils with sufficiently strong winding tensions at coil-operating temperature, the mechanical losses vanished.

  8. Technique for reduction of mechanical losses in AC superconducting coils due to thermal expansion properties of various FRP bobbins

    Energy Technology Data Exchange (ETDEWEB)

    Sekine, N. [Tsukamoto Laboratory, Faculty of Engineering, Yokohama National University, 79-5, Tokiwadai, Hodogaya-ku, Yokohama 240-8501 (Japan)]. E-mail: n-sekine@tsukalab.dnj.ynu.ac.jp; Tada, S. [Sophia University, 7-1, Kioicho, Chiyoda-ku, Tokyo 102-8554 (Japan); Higuchi, T. [Sophia University, 7-1, Kioicho, Chiyoda-ku, Tokyo 102-8554 (Japan); Furumura, Y. [Sophia University, 7-1, Kioicho, Chiyoda-ku, Tokyo 102-8554 (Japan); Takao, T. [Sophia University, 7-1, Kioicho, Chiyoda-ku, Tokyo 102-8554 (Japan); Yamanaka, A. [Research Center, Toyobo, Co., Ltd, 2-1-1, Katata, Otsu, Shiga 520-0292 (Japan)

    2005-10-01

    We reported about reduction of mechanical losses in AC superconducting coils. The method is the use of FRP bobbins fabricated with special fibers. Since their FRPs have negative thermal expansion coefficient to the fiber direction, the FRP bobbins expand to the circumferential direction during cooling down. In case of the superconducting coils with such FRP bobbins, the winding tensions do not decrease during cooling down. Therefore, the mechanical losses are reduced by the suppression of wire's vibration. Their special FRPs are a Dyneema[reg] fiber reinforced plastic (DFRP), a Dyneema and glass fiber reinforced plastic (DGFRP), and a Zylon[reg] fiber reinforced plastic (ZFRP). These materials have negative thermal expansion coefficient to the fiber direction, however, the amplitudes of thermal expansion are various by the quantity or quality of the fiber. In this paper, the values of thermal expansion were actually measured, and it was discussed about the influence on the mechanical losses. At the experimental results, the mechanical loss was small, so that the thermal strain to the circumferential direction on the coil was large. Moreover, in case of the coils with sufficiently strong winding tensions at coil-operating temperature, the mechanical losses vanished.

  9. High temperature and pressure effects on the elastic properties of B2 intermetallics AgRE

    Science.gov (United States)

    Liu, Lili; Wu, Xiaozhi; Li, Weiguo; Wang, Rui; Liu, Qing

    2015-02-01

    The high temperature and pressure effects on the elastic properties of the AgRE (RE=Sc, Tm, Er, Dy, Tb) intermetallic compounds with B2 structure have been performed from first principle calculations. For the temperature range 0-1000 K, the second order elastic constants for all the AgRE intermetallic compounds follow a normal behavior: they decrease with increasing temperature. The pressure dependence of the second order elastic constants has been investigated on the basis of the third order elastic constants. Temperature and pressure dependent elastic anisotropic parameters A have been calculated based on the temperature and pressure dependent elastic constants.

  10. A first principle study of the pressure dependent elastic properties of monazite LaPO4

    Science.gov (United States)

    Ali, Kawsar; Arya, A.; Ghosh, P. S.; Dey, G. K.

    2016-05-01

    DFT based ab-initio simulations have been performed to study the effect of pressure on the elastic properties of monazite LaPO4 which is a promising host material for immobilization of high level nuclear waste. The phase is found to be stable up to 30 GPa. The calculated polycrystalline bulk, shear and Young moduli show an increasing trend as a function of pressure. The ductility and anisotropy in shear modulus of the material have been found to increase with pressure; whilethe bulk modulus anisotropy decreases with pressure.

  11. First-principles investigation of the electronic, elastic and thermodynamic properties of VC under high pressure

    Institute of Scientific and Technical Information of China (English)

    Hao Ai-Min; Zhou Tie-Jun; Zhu Yan; Zhang Xin-Yu; Liu Ri-Ping

    2011-01-01

    An investigation of the electronic, elastic and thermodynamic properties of VC under high pressure has been conducted using first-principles calculations based on density functional theory (DFT)with the plane-wave basis set,as implemented in the CASTEP code. At elevated pressures, VC is predicted to undergo a structural transition from a relatively open NaCl-type structure to a more dense CsCl-type one. The predicted transition pressure is 520 GPa.The elastic constant, Debye temperature and heat capacity each as a function of pressure and/or temperature of VC are presented for the first time.

  12. Superconducting and mechanical properties of the bulk Bi(pb)SCCO system prepared via solid state and ammonium nitrate precipitation methods

    Science.gov (United States)

    Safran, S.; Kılıçarslan, E.; Ozturk, H.; Alp, M.; Akdogan, M.; Asikuzun, E.; Ozturk, O.; Kılıç, A.

    2015-09-01

    We have investigated the effect of preparation method on superconducting and mechanical properties of Bi(Pb)-2223 bulk samples using Bi1.85Pb0.35Sr2Ca2Cu3O10±y stoichiometry. Solid-state reaction and ammonium nitrate precipitation methods have been used for fabrication of the bulk samples. In addition, the effect of annealing time on BSCCO samples have been studied. Structural, electrical, magnetic and microhardness analyses of samples are performed by the X-ray powder diffraction (XRD), the Scanning Electron Microscopy (SEM), DC resistivity, AC susceptibility and Vickers microhardness test. The critical transition temperature, phase purity, surface morphology and crystallinity of the prepared bulk samples are compared with each other. Elasticity (E), brittleness (Bi), fracture toughness (KIC) and yield strength (Y) values are also determined according to annealing time, applied load and production parameters of materials.

  13. Structural phase transition and elastic properties of thorium pnictides at high pressure

    Indian Academy of Sciences (India)

    Kuldeep Kholiya; B R K Gupta

    2007-04-01

    In the present paper we have pointed out the weaknesses of the approach by Aynyas et al [1] to study the structural phase transition and elastic properties of thorium pnictides. The calculated values of phase transition pressure and other elastic properties using the realistic and actual approach are also given and compared with the experimental and previous theoretical work.

  14. Superconductivity in La1-x Sm x O0.5F0.5BiS2 (x  =  0.2, 0.8) under hydrostatic pressure

    Science.gov (United States)

    Kalai Selvan, G.; Thakur, Gohil S.; Manikandan, K.; Banerjee, A.; Haque, Zeba; Gupta, L. C.; Ganguli, Ashok K.; Arumugam, S.

    2016-07-01

    We have investigated the pressure effect on the newly discovered samarium-doped La1-x Sm x O0.5F0.5BiS2 superconductors. More than a threefold increase in T c (10.3 K) is observed with external pressure (at ~1.74 GPa at a rate of 4.08 K GPa-1) for x  =  0.2 composition. There is a concomitant large improvement in the quality of the superconducting transition. Beyond this pressure T c decreases monotonously at the rate of  -2.09 K GPa-1. In the x  =  0.8 sample, we do not observe any enhancement in T c with the application of pressure (up to 1.76 GPa). The semiconducting behavior observed in the normal-state resistivity of both samples is significantly subdued with the application of pressure which, if interpreted by invoking the thermal activation process, implies that the activation energy gap of the carriers is significantly reduced with pressure. We believe these observations should generate further interest in La1-x Sm x O0.5F0.5BiS2 superconductors.

  15. Magnetism and Pressure-Induced Superconductivity of Checkerboard-Type Charge-Ordered Molecular Conductor β-(meso-DMBEDT-TTF2X (X = PF6 and AsF6

    Directory of Open Access Journals (Sweden)

    Yutaka Nishio

    2012-11-01

    Full Text Available The metallic state of the molecular conductor β-(meso-DMBEDT-TTF2X (DMBEDT-TTF = 2-(5,6-dihydro-1,3-dithiolo[4,5-b][1,4]dithiin-2-ylidene-5,6-dihydro-5,6-dimethyl-1,3-dithiolo[4,5-b][1,4]dithiin, X = PF6, AsF6 is transformed into the checkerboard-type charge-ordered state at around 75–80 K with accompanying metal-insulator (MI transition on the anisotropic triangular lattice. With lowering temperatures, the magnetic susceptibility decreases gradually and reveals a sudden drop at the MI transition. By applying pressure, the charge-ordered state is suppressed and superconductivity appears in β-(meso-DMBEDT-TTF2AsF6 as well as in the reported β-(meso-DMBEDT-TTF2PF6. The charge-ordered spin-gapped state and the pressure-induced superconducting state are discussed through the paired-electron crystal (PEC model, where the spin-bonded electron pairs stay and become mobile in the crystal, namely the valence-bond solid (VBS and the resonant valence bonded (RVB state in the quarter-filled band structure.

  16. Two types of superconducting domes in unconventional superconductors

    Science.gov (United States)

    Das, Tanmoy; Panagopoulos, Christos

    2016-10-01

    Uncovering the origin of unconventional superconductivity is often plagued by the overwhelming material diversity with varying normal and superconducting (SC) properties. In this article, we deliver a comprehensive study of the SC properties and phase diagrams using multiple tunings (such as disorder, pressure or magnetic field in addition to doping and vice versa) across several families of unconventional superconductors, including the copper-oxides, heavy-fermions, organics and the recently discovered iron-pnictides, iron-chalcogenides, and oxybismuthides. We discover that all these families often possess two types of SC domes, with lower and higher SC transition temperatures T c, both unconventional but with distinct SC and normal states properties. The lower T c dome arises with or without a quantum critical point (QCP), and not always associated with a non-Fermi liquid (NFL) background. On the contrary, the higher-T c dome clearly stems from a NFL or strange metal phase, without an apparent intervening phase transition or a QCP. The two domes appear either fully separated in the phase diagram, or merged into one, or arise independently owing to their respective normal state characteristics. Our findings suggest that a QCP-related mechanism is an unlikely scenario for the NFL phase in these materials, and thereby narrows the possibility towards short-range fluctuations of various degrees of freedom in the momentum and frequency space. We also find that NFL physics may be a generic route to higher-T c superconductivity.

  17. Oxygen Adsorption-Desorption Behavior and Superconducting Properties of High-Tc Bi(Pb)-Sr-Ca-Cu-O

    Science.gov (United States)

    Miura, Norio; Suzuta, Hiroki; Deshimaru, Yuichi; Shimizu, Youichi; Sakashita, Hirofumi; Yamazoe, Noboru

    1989-07-01

    Temperature-programmed desorption (TPD) chromatograms revealed that a small amount of oxygen was desorbed from high-Tc Bi(Pb)-Sr-Ca-Cu-O (BPSCCO) in the temperature range from ca. 350 to ca. 650°C prior to a steep increase of oxygen desorption in the higher temperature range. The Tc of BPSCCO was significantly lowered with the progress of oxygen desorption especially in the former temperature range, and was restored to the original level when the desorbed oxygen was recovered. With no corresponding changes in X-ray powder diffraction pattern being detected, the oxygen desorbed below ca. 650°C was concluded to have strong relevance to the superconductivity of BPSCCO.

  18. Effect of starting materials on the superconducting properties of SmFeAsO1-xFx tapes

    Science.gov (United States)

    Wang, Chunlei; Yao, Chao; Zhang, Xianping; Gao, Zhaoshun; Wang, Dongliang; Wang, Chengduo; Lin, He; Ma, Yanwei; Awaji, Satoshi; Watanabe, Kazuo

    2012-03-01

    SmFeAsO1-xFx tapes were prepared using three kinds of starting materials. This showed that the starting materials have an obvious effect on the impurity phases in the final superconducting tapes. Compared with the other samples, the samples fabricated with SmAs, FeO, Fe2As, and SmF3 have the smallest arsenide impurity phases and voids. As a result, these samples possess much denser structures and better grain connectivities. Moreover, among the three kinds of sample fabricated in this work, this kind of sample has the highest zero resistivity temperature, ˜40 K, and the largest critical current density, ˜4600 A cm-2, in self-field at 4.2 K. This is the highest Jc value reported so far for SmFeAsO1-xFx wires and tapes.

  19. Superconductivity and magnetic properties in SmFe1-xCoxAsO (x=0 to 1)

    Science.gov (United States)

    Qi, Yanpeng; Wang, Lei; Gao, Zhaoshun; Wang, Dongliang; Zhang, Xianping; Yao, Chao; Wang, Chunlei; Wang, Chengduo; Ma, Yanwei

    2011-10-01

    In this paper the effects of replacing Fe with Co in SmFe1-xCoxAsO (x=0 to 1) are reported. X-ray diffraction patterns indicate that all the samples have formed the ZrCuSiAs-type structure with a space group P4/nmm and a full solid solution forms between SmFeAsO and SmCoAsO. It is found that the antiferromagnetic spin-density-wave (SDW) order in the parent compounds is rapidly suppressed by Co-doping, and superconductivity emerges as 0.05 SmFeAsO-SmCoAsO system. The systemic study in the SmFe1-xCoxAsO system would add more ingredients to the underlying physics of this material.

  20. Information quantifiers, entropy squeezing and entanglement properties of superconducting qubit-deformed bosonic field system under dephasing effect

    Science.gov (United States)

    Berrada, K.; Al-Rajhi, M. A.

    2017-10-01

    In this paper, we present a detailed study on the evolution of some measures of nonclassicality and entanglement in the framework of the interaction between a superconducting qubit and deformed bosonic fields under decoherence effect. We compare the dynamical behavior of the different quantum quantifiers by exploiting a large set of nonlinear bosonic fields that are characterized by the deformation parameter. Additionally, we demonstrate how the connection between the appearance of the nonlinearity in the deformed field and the quantum information quantifiers. The time correlation between entropy squeezing, purity, and entanglement is examined in terms of the physical parameters involved in the whole system. Lastly, we explore the exact ranges of the physical parameters in order to combat the decoherence effect and maintain high amount of entanglement during the time evolution.