Superconducting state mechanisms and properties

CERN Document Server

Kresin, Vladimir Z; Wolf, Stuart A

2014-01-01

'Superconducting State' provides a very detailed theoretical treatment of the key mechanisms of superconductivity, including the current state of the art (phonons, magnons, and plasmons). A very complete description is given of the electron-phonon mechanism responsible for superconductivity in the majority of superconducting systems, and the history of its development, as well as a detailed description of the key experimental techniques used to study the superconducting state and determine the mechanisms. In addition, there are chapters describing the discovery and properties of the key superconducting compounds that are of the most interest for science, and applications including a special chapter on the cuprate superconductors. It provides detailed treatments of some very novel aspects of superconductivity, including multiple bands (gaps), the "pseudogap" state, novel isotope effects beyond BCS, and induced superconductivity.

Possible superconductivity in the Bismuth IV solid phase under pressure.

Science.gov (United States)

Valladares, Ariel A; Rodríguez, Isaías; Hinojosa-Romero, David; Valladares, Alexander; Valladares, Renela M

2018-04-13

The first successful theory of superconductivity was the one proposed by Bardeen, Cooper and Schrieffer in 1957. This breakthrough fostered a remarkable growth of the field that propitiated progress and questionings, generating alternative theories to explain specific phenomena. For example, it has been argued that Bismuth, being a semimetal with a low number of carriers, does not comply with the basic hypotheses underlying BCS and therefore a different approach should be considered. Nevertheless, in 2016 based on BCS we put forth a prediction that Bi at ambient pressure becomes a superconductor at 1.3 mK. A year later an experimental group corroborated that in fact Bi is a superconductor with a transition temperature of 0.53 mK, a result that eluded previous work. So, since Bi is superconductive in almost all the different structures and phases, the question is why Bi-IV has been elusive and has not been found yet to superconduct? Here we present a study of the electronic and vibrational properties of Bi-IV and infer its possible superconductivity using a BCS approach. We predict that if the Bi-IV phase structure were cooled down to liquid helium temperatures it would also superconduct at a T c of 4.25 K.

Structural stability, electronic, mechanical and superconducting properties of CrC and MoC

Energy Technology Data Exchange (ETDEWEB)

Kavitha, M.; Sudha Priyanga, G. [Department of Physics, N.M.S.S.V.N College, Madurai 625019, Tamilnadu (India); Rajeswarapalanichamy, R., E-mail: rrpalanichamy@gmail.com [Department of Physics, N.M.S.S.V.N College, Madurai 625019, Tamilnadu (India); Iyakutti, K. [Department of Physics and Nanotechnology, SRM University, Chennai 603203, Tamilnadu (India)

2016-02-01

The structural, electronic, mechanical and superconducting properties of chromium carbide (CrC) and molybdenum carbide (MoC) are investigated using first principles calculations based on density functional theory (DFT). The computed ground state properties like equilibrium lattice constants and cell volume are in good agreement with available theoretical and experimental data. A pressure induced structural phase transition from tungsten carbide phase (WC) to zinc blende phase (ZB) and then zinc blende phase (ZB) to nickel arsenide phase (NiAs) are observed in both chromium and molybdenum carbides. Electronic structure reveals that these carbides are metallic at ambient condition. All the calculated elastic constants obey the Born–Huang stability criteria, suggesting that they are mechanically stable at normal and high pressure. The super conducting transition temperatures for CrC and MoC in WC phase are found to be 31.12 K and 17.14 K respectively at normal pressure. - Highlights: • Electronic and mechanical properties of CrC and MoC are investigated. • Pressure induced structural phase transition is predicted at high pressure. • Electronic structure reveals that these materials exhibit metallic behaviour. • Debye temperature values are computed for CrC and MoC. • Superconducting transition temperature values are computed.

Anomalous anisotropic compression behavior of superconducting CrAs under high pressure

Science.gov (United States)

Yu, Zhenhai; Wu, Wei; Hu, Qingyang; Zhao, Jinggeng; Li, Chunyu; Yang, Ke; Cheng, Jinguang; Luo, Jianlin; Wang, Lin; Mao, Ho-kwang

2015-01-01

CrAs was observed to possess the bulk superconductivity under high-pressure conditions. To understand the superconducting mechanism and explore the correlation between the structure and superconductivity, the high-pressure structural evolution of CrAs was investigated using the angle-dispersive X-ray diffraction (XRD) method. The structure of CrAs remains stable up to 1.8 GPa, whereas the lattice parameters exhibit anomalous compression behaviors. With increasing pressure, the lattice parameters a and c both demonstrate a nonmonotonic change, and the lattice parameter b undergoes a rapid contraction at ∼0.18−0.35 GPa, which suggests that a pressure-induced isostructural phase transition occurs in CrAs. Above the phase transition pressure, the axial compressibilities of CrAs present remarkable anisotropy. A schematic band model was used to address the anomalous compression behavior of CrAs. The present results shed light on the structural and related electronic responses to high pressure, which play a key role toward understanding the superconductivity of CrAs. PMID:26627230

Pressure effect on the electrical conductivity and superconductivity of beta-(BDA-TTP)2I3.

Science.gov (United States)

Yamada, Jun-Ichi; Fujimoto, Kazuya; Akutsu, Hiroki; Nakatsuji, Shin'ichi; Miyazaki, Akira; Aimatsu, Masashi; Kudo, Satoshi; Enoki, Toshiaki; Kikuchi, Koichi

2006-03-28

The pressure-induced electrical conductivity properties of beta-(BDA-TTP)2I3 have been investigated; the salt exhibits a dramatic change in the conductivity behaviour above ca. 10 kbar and undergoes a superconducting transition with an onset near 10 K.

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 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.

Superconducting critical temperature under pressure

Science.gov (United States)

González-Pedreros, G. I.; Baquero, R.

2018-05-01

The present record on the critical temperature of a superconductor is held by sulfur hydride (approx. 200 K) under very high pressure (approx. 56 GPa.). As a consequence, the dependence of the superconducting critical temperature on pressure became a subject of great interest and a high number of papers on of different aspects of this subject have been published in the scientific literature since. In this paper, we calculate the superconducting critical temperature as a function of pressure, Tc(P), by a simple method. Our method is based on the functional derivative of the critical temperature with the Eliashberg function, δTc(P)/δα2F(ω). We obtain the needed coulomb electron-electron repulsion parameter, μ*(P) at each pressure in a consistent way by fitting it to the corresponding Tc using the linearized Migdal-Eliashberg equation. This method requires as input the knowledge of Tc at the starting pressure only. It applies to superconductors for which the Migdal-Eliashberg equations hold. We study Al and β - Sn two weak-coupling low-Tc superconductors and Nb, the strong coupling element with the highest critical temperature. For Al, our results for Tc(P) show an excellent agreement with the calculations of Profeta et al. which are known to agree well with experiment. For β - Sn and Nb, we found a good agreement with the experimental measurements reported in several works. This method has also been applied successfully to PdH elsewhere. Our method is simple, computationally light and gives very accurate results.

Superconductivity in lanthanum chalcogenides under pressure

International Nuclear Information System (INIS)

Eiling, A.

1981-01-01

In this thesis the pressure dependence of the superconducting transition temperature of La 3 S 4 , La 3 Se 4 , La 3 Te 4 , La 2 Se 2 S 2 , and La 2 Sesub(3,6) Tesub(0,4) is investigated up to 4,5 GPa. A pressure cell is reported which allows also the measurement of the magnetic susceptibility under pressure. The calculated density of states describe the increase of the critical temperature very well in the frame of Mc Millans equation. (TWO)

Concurrence of superconductivity and structure transition in Weyl semimetal TaP under pressure

Energy Technology Data Exchange (ETDEWEB)

Li, Yufeng; Zhou, Yonghui; Guo, Zhaopeng; Han, Fei; Chen, Xuliang; Lu, Pengchao; Wang, Xuefei; An, Chao; Zhou, Ying; Xing, Jie; Du, Guan; Zhu, Xiyu; Yang, Huan; Sun, Jian; Yang, Zhaorong; Yang, Wenge; Mao, Ho-Kwang; Zhang, Yuheng; Wen, Hai-Hu

2017-12-01

Weyl semimetal defines a material with three-dimensional Dirac cones, which appear in pair due to the breaking of spatial inversion or time reversal symmetry. Superconductivity is the state of quantum condensation of paired electrons. Turning a Weyl semimetal into superconducting state is very important in having some unprecedented discoveries. In this work, by doing resistive measurements on a recently recognized Weyl semimetal TaP under pressures up to about 100 GPa, we show the concurrence of superconductivity and a structure transition at about 70 GPa. It is found that the superconductivity becomes more pronounced when decreasing pressure and retains when the pressure is completely released. High-pressure x-ray diffraction measurements also confirm the structure phase transition from I41md to P-6m2 at about 70 GPa. More importantly, ab-initial calculations reveal that the P-6m2 phase is a new Weyl semimetal phase and has only one set of Weyl points at the same energy level. Our discovery of superconductivity in TaP by high pressure will stimulate investigations on superconductivity and Majorana fermions in Weyl semimetals.

Pressure effect on the superconducting and the normal state of β -B i2Pd

Science.gov (United States)

Pristáš, G.; Orendáč, Mat.; Gabáni, S.; Kačmarčík, J.; Gažo, E.; Pribulová, Z.; Correa-Orellana, A.; Herrera, E.; Suderow, H.; Samuely, P.

2018-04-01

The pressure effect up to 24.0 kbar on superconducting and normal-state properties of β -B i2Pd single crystal (Tc≈4.98 K at ambient pressure) has been investigated by measurements of the electrical resistivity. In addition, we have performed the heat capacity measurements in the temperature range 0.7-300 K at ambient pressure. The recent calculations of electronic density of states, electron-phonon interaction spectral function, and phonon density of states of β -B i2Pd [Zheng and Margine, Phys. Rev. B 95, 014512 (2017), 10.1103/PhysRevB.95.014512], are used to fit the resistivity and the heat capacity data. In the superconducting state we have focused on the influence of pressure on the superconducting transition temperature Tc and upper critical field Hc 2 and a negative effect with d Tc/d p =-0.025 K /kbar and d Hc 2/d p =-8 mT /kbar is found. A simplified Bloch-Grüneisen model was used to analyze the pressure effect on the temperature dependence of the normal-state resistivity. The obtained results point to a decrease of the electron-phonon coupling parameter λ and to a shift of phonon frequencies to higher values with pressure. Moreover, the temperature dependence of the normal-state resistivity follows a T2 dependence above Tc up to about 25 K. Together with the enhanced value of Sommerfeld coefficient γ =13.23 mJ mo l-1K-2 these results point to a certain role of the electron-electron interaction in the superconducting pairing mechanism in β -B i2Pd .

Superconductivity in CeRh2Si2 Under Pressure

International Nuclear Information System (INIS)

Araki, S.; Nakashima, M.; Settai, R.; Kobayashi, T.C.; Onuki, Y.

2003-01-01

We have studied the pressure-induced superconductivity in an antiferromagnet CeRh 2 Si 2 by measuring the electrical resistivity for a high-quality single crystal. The superconducting resistivity drop was observed around P c ∼eq 1.06 GPa, at which the Neel temperature becomes zero, namely in a pressure region from 0.97 to 1.20 GPa. The zero resistivity appears below 0.4 K between 1.03 to 1.08 GPa. The resistivity at low temperatures follows the Fermi liquid AT 2 relation in the whole pressure region, even at P c . The A value becomes a maximum around P c . (author)

Superconductivity at high pressure in NbSe3

International Nuclear Information System (INIS)

Nunez Regueiro, M.; Castello, D.; Mignot, J.M.

1992-01-01

We have measured the electrical resistivity of NbSe 3 between 2 K and room temperature up to a pressure of 7.2 GPa. At P 1 = 3.5 GPa we observe the extinction of the high-temperature charge density wave (T 1 -CDW) and the enhancement of the superconducting critical temperature T c to ≅ 5 K. The logarithmic pressure slopes of T 1 (P 1 ) and T c (P > P 1 ) are found to be practically equal. A similar behaviour had been reported previously at lower pressures for T 2 (P 2 ) and T c (P 2 1 ) in the distorted state. We discuss these results in terms of an anisotropic superconducting state in NbSe 3 , with different gaps associated with different types of chains. 10 refs., 2 figs

Pressure induced superconductivity in the antiferromagnetic Dirac material BaMnBi2.

Science.gov (United States)

Chen, Huimin; Li, Lin; Zhu, Qinqing; Yang, Jinhu; Chen, Bin; Mao, Qianhui; Du, Jianhua; Wang, Hangdong; Fang, Minghu

2017-05-09

The so-called Dirac materials such as graphene and topological insulators are a new class of matter different from conventional metals and (doped) semiconductors. Superconductivity induced by doing or applying pressure in these systems may be unconventional, or host mysterious Majorana fermions. Here, we report a successfully observation of pressure-induced superconductivity in an antiferromagnetic Dirac material BaMnBi 2 with T c of ~4 K at 2.6 GPa. Both the higher upper critical field, μ 0 H c2 (0) ~ 7 Tesla, and the measured current independent of T c precludes that superconductivity is ascribed to the Bi impurity. The similarity in ρ ab (B) linear behavior at high magnetic fields measured at 2 K both at ambient pressure (non-superconductivity) and 2.6 GPa (superconductivity, but at the normal state), as well as the smooth and similar change of resistivity with pressure measured at 7 K and 300 K in zero field, suggests that there may be no structure transition occurred below 2.6 GPa, and superconductivity observed here may emerge in the same phase with Dirac fermions. Our findings imply that BaMnBi 2 may provide another platform for studying SC mechanism in the system with Dirac fermions.

Superconducting property measuring system by magnetization method

International Nuclear Information System (INIS)

Ikisawa, K.; Mori, T.; Takasu, N.

1988-01-01

Superconducting property measuring system (CMS-370B) for high temperature oxide superconductor has been developed. This system adopts magnetization measurement. The superconducting properties are able to be measured automatically and continuously changing the temperature and external magnetic field. The critical current density as a function of temperature and magnetic field of high temperature superconductor YBa 2 Cu 3 O 7-y (YBCO) has been measured. This paper reports how it was confirmed that this system having the high performance and the accuracy gave the significant contribution to the superconducting material development

Pressure effect on magnetism and superconductivity in CePt{sub 3}Si

Energy Technology Data Exchange (ETDEWEB)

Takeuchi, T. [Low Temperature Center, Osaka University, Toyonaka, Osaka 560-0043 (Japan) and KYOKUGEN, Osaka University, Toyonaka, Osaka 560-8513 (Japan)]. E-mail: takeuchi@rcem.osaka-u.ac.jp; Shiimoto, M. [Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan); Kohara, H. [Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan); Yasuda, T. [Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan); Hashimoto, S. [Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan); Settai, R. [Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan); Onuki, Y. [Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan); Advanced Science Research Center, JAERI, Tokai, Ibaraki 319-1195 (Japan)

2006-05-01

Magnetism and superconductivity in the heavy-fermion superconductor CePt{sub 3}Si have been studied under pressure. The antiferromagnetic and superconducting transition temperatures, T{sub N} and T{sub sc}, respectively, decrease by applying pressure. T{sub N} becomes zero around 0.6-0.7GPa, while the pressure dependence of T{sub sc} exhibits a shoulder-like feature around 0.7GPa, and superconductivity is found to persist in the pressure range up to about 1.5GPa. A broad peak around 5K in the temperature derivative of thermal expansion {alpha}(T) and electrical resistivity d{rho}(T)/dT at ambient pressure begins to shift to higher temperatures above 0.7GPa. These results suggest that a critical pressure exists around 0.6-0.7GPa in CePt{sub 3}Si.

Superconductivity in the unconventional high pressure phase bismuth-III

Energy Technology Data Exchange (ETDEWEB)

Semeniuk, Konstantin; Brown, Philip; Vasiljkovic, Aleksandar; Grosche, Malte [University of Cambridge (United Kingdom)

2015-07-01

One of the most surprising developments in high pressure research was the realisation that many elements assume very unexpected high pressure structures, described in terms of extremely large or even infinite unit cells. Elemental bismuth, which has been known to undergo a series of pressure induced structural transitions between 25 kbar and 80 kbar, is an interesting example: the intermediate pressure Bi-III phase has a complex 'host-guest' structure consisting of two incommensurate sublattices. Since the unit cell is infinitely large, the description of electronic and lattice excitations is problematic. Apart from its metallic character and the observation of superconductivity at low temperature, little is known about the electronic structure in this phase. We investigate the electrical resistivity within the metallic Bi-III phase under high hydrostatic pressure and in applied magnetic field using a piston cylinder cell. Superconductivity is observed below 7.1 K, and we extract the temperature dependence of the upper critical field, which exceeds 2 T at low temperature. The normal state resistivity exhibits an approximately linear temperature dependence. This could be attributed to strong scattering from low-lying excitations, as caused by an unusually soft phonon spectrum. The results suggest that strong coupling superconductivity arises within the host-guest structure of Bi-III out of an unusual electronic state.

Colloquium: High pressure and road to room temperature superconductivity

Science.gov (United States)

Gor'kov, Lev P.; Kresin, Vladimir Z.

2018-01-01

This Colloquium is concerned with the superconducting state of new high-Tc compounds containing hydrogen ions (hydrides). Recently superconductivity with the record-setting transition temperature of Tc=203 K was reported for sulfur hydrides under high pressure. In general, high pressure serves as a path finding tool toward novel structures, including those with very high Tc . The field has a rich and interesting history. Currently, it is broadly recognized that superconductivity in sulfur hydrides owes its origin to the phonon mechanism. However, the picture differs from the conventional one in important ways. The phonon spectrum in sulfur hydride is both broad and has a complex structure. Superconductivity arises mainly due to strong coupling to the high-frequency optical modes, although the acoustic phonons also make a noticeable contribution. A new approach is described, which generalizes the standard treatment of the phonon mechanism and makes it possible to obtain an analytical expression for Tc in this phase. It turns out that, unlike in the conventional case, the value of the isotope coefficient (for the deuterium-hydrogen substitution) varies with the pressure and reflects the impact of the optical modes. The phase diagram, that is the pressure dependence of Tc , is rather peculiar. A crucial feature is that increasing pressure results in a series of structural transitions, including the one which yields the superconducting phase with the record Tc of 203 K. In a narrow region near P ≈150 GPa the critical temperature rises sharply from Tc≈120 to ≈200 K . It seems that the sharp structural transition, which produces the high-Tc phase, is a first-order phase transition caused by interaction between the order parameter and lattice deformations. A remarkable feature of the electronic spectrum in the high-Tc phase is the appearance of small pockets at the Fermi level. Their presence leads to a two-gap spectrum, which can, in principle, be observed with the

The pressure effect on the superconducting transition temperature of black phosphorus

CERN Document Server

Karuzawa, M; Endo, S

2002-01-01

We have measured the pressure effect on the superconducting transition temperature T sub c of black phosphorus up to 160 GPa using a superconducting quantum interference device vibrating coil magnetometer. It was found that T sub c had a maximum value of about 9.5 K at about 32 GPa, began decreasing with pressure and reached about 4.3 K at about 100 GPa.

Thermodynamic properties of pressurized PH3 superconductor

Science.gov (United States)

Koka, S.; Rao, G. Venugopal

2018-05-01

The paper presents the superconducting thermodynamic functions determined for pressurized phosphorus trihydride (PH3). In particular, free energy difference ΔF, thermodynamic critical field Hc, specific heat etc. have been calculated using analytical expressions. The calculations were performed in the frame work of the strong-coupling formalism. The obtained dimensionless parameters: RΔ ≡ 2Δ(0)/kBTc, RC ≡ ΔC(Tc)/CN(Tc) and RH≡TcCN(Tc)/Hc2(0) are 4.05, 1.96 and 0.156 respectively, which significantly differ from the values arising from the BCS theory of superconductivity. The thermodynamic properties strongly depend on the depairing electron correlations and retardation effects.

Exploring high-pressure FeB{sub 2}: Structural and electronic properties predictions

Energy Technology Data Exchange (ETDEWEB)

Harran, Ismail [School of Physical Science and Technology, Key Laboratory of Advanced Technologies of Materials, Ministry of Education of China, Southwest Jiaotong University, Chengdu, 610031 (China); Al Fashir University (Sudan); Wang, Hongyan [School of Physical Science and Technology, Key Laboratory of Advanced Technologies of Materials, Ministry of Education of China, Southwest Jiaotong University, Chengdu, 610031 (China); Chen, Yuanzheng, E-mail: cyz@calypso.org.cn [School of Physical Science and Technology, Key Laboratory of Advanced Technologies of Materials, Ministry of Education of China, Southwest Jiaotong University, Chengdu, 610031 (China); Jia, Mingzhen [School of Physical Science and Technology, Key Laboratory of Advanced Technologies of Materials, Ministry of Education of China, Southwest Jiaotong University, Chengdu, 610031 (China); Wu, Nannan [School of Mathematics, Physics and Biological Engineering, Inner Mongolia University of Science & Technology, Baotou, 014010 (China)

2016-09-05

The high pressure (HP) structural phase of FeB{sub 2} compound is investigated by using first-principles crystal structure prediction based on the CALYPSO technique. A thermodynamically stable phase of FeB{sub 2} with space group Imma is predicted at pressure above 225 GPa, which is characterized by a layered orthorhombic structure containing puckered graphite-like boron layers. Its electronic and mechanical properties are identified and analyzed. The feature of band structures favors the occurrence of superconductivity, whereas, the calculated Pugh's ratio reveals that the HP Imma structure exhibits ductile mechanical property. - Highlights: • The high pressure structural phase of FeB{sub 2} compound is firstly investigated by the CALYPSO technique. • A thermodynamically stable Imma phase of FeB{sub 2} is predicted at pressure above 225 GPa. • The Imma structure is characterized by a 2D boron network containing puckered graphite-like boron layers. • The band feature of Imma structure favors the occurrence of superconductivity. • The calculated Pugh's ratio suggests that the Imma structure exhibits ductile mechanical property.

High-pressure phases of S, Se, and P hydrides and their superconducting properties. Predictions from ab-initio theory

Energy Technology Data Exchange (ETDEWEB)

Gross, E.K.U. [Max Planck Institute of Microstructure Physics, Halle (Saale) (Germany)

2016-07-01

The quest for novel high-temperature superconductors in the family of hydrogen-rich compounds has recently been crowned with the experimental discovery of a record critical temperature of 190 K in a hydrogen-sulfur compound at 200 GPa. In the present contribution, we investigate the phase diagram of the H-S system, comparing the stability of H{sub n}S (n = 1,2,3,4) by means of the minima hopping method for structure prediction. Our extensive crystal structure search confirms the H{sub 3}S stoichiometry as the most stable configuration at high pressure. Superconducting properties are calculated using the fully ab-initio parameter-free approach of density functional theory for superconductors. We find a T{sub c} of 180 K at 200 GPa, in excellent agreement with experiment. We also show that Se-H has a phase diagram similar to its sulfur counterpart. We predict H{sub 3}Se to be superconducting at temperatures higher than 120 K at 100 GPa. We furthermore investigate the phase diagram of PH{sub n} (n = 1,2,3,4,5,6). The results of our crystal-structure search do not support the existence of thermodynamically stable PH{sub n} compounds, which exhibit a tendency for elemental decomposition at high pressure. Although the lowest energy phases of PH{sub n=1,2,3} display T{sub c} values comparable to experiment, it remains uncertain if the measured values of T{sub c} can be fully attributed to a phase-pure compound of PH{sub n}.

Pressure effect on the transport properties of superconducting Li0.9MobO17bronze

International Nuclear Information System (INIS)

Filippini, C.E.; Boujida, M.; Marcus, J.; Schlenker, C.; Beille, J.

1989-01-01

The electrical resistivity of Li 0.9 Mo 6 O 17 single crystal has been studied between 1.5 K and 300 K under hydrostatic pressures up to 20 k bar. A large increase of the superconducting transition temperature, from 1.7 K to 2.5 K, is associated to a sharp decease of the temperature T m of the electronic, probably CDW instability

Superconductivity and photoacoustic properties of sintered La/sub 1.8/Sr/sub 0.2/CuO/sub 4/

International Nuclear Information System (INIS)

Sawan, Y.; Abu-Zeid, M.; Yousef, Y.A.

1987-01-01

In this paper the superconductivity transition properties of La/sub 1.8/Sr/sub 0.2/CuO/sub 4/ are investigated by resistivity and photo-acoustic measurements on samples prepared at different thermal prehistories. Samples with onset transition temperature of 40K and zero resistance at 35 K is detected at ambient pressure. The recent discovery of high T/sub c/ superconductivity up to 35 K in the La-Ba-Cu-O system was followed by rapid enthusiasm and intensive investigations in this field. The effect of thermal prehistory on the superconducting properties of La/sub 1.8/Sr/sub 0.2/CuO/sub 4/ and the photoacoustic characteristics of both the prepared superconducting materials as well as that of the initial starting oxides are presented

Superconductivity of ternary metal compounds prepared at high pressures

CERN Document Server

Shirotani, I

2003-01-01

Various ternary metal phosphides, arsenides, antimonides, silicides and germanides have been prepared at high temperatures and high pressures. These ternary metal compounds can be classified into four groups: [1] metal-rich compounds MM' sub 4 X sub 2 and [2] MM'X, [3] non-metal-rich compounds MXX' and [4] MM' sub 4 X sub 1 sub 2 (M and M' = metal element; X and X' = non-metal element). We have studied the electrical and magnetic properties of these materials at low temperatures, and found many new superconductors with the superconducting transition temperature (T sub c) of above 10 K. The metal-rich compound ZrRu sub 4 P sub 2 with a tetragonal structure showed the superconducting transition at around 11 K, and had an upper critical field (H sub c sub 2) of 12.2 tesla (T) at 0 K. Ternary equiatomic compounds ZrRuP and ZrRuSi crystallize in two modifications, a hexagonal Fe sub 2 P-type structure [h-ZrRuP(Si)] and an orthorhombic Co sub 2 P-type structure [o-ZrRuP(Si)]. Both h-ZrRuP and h-ZrRuSi have rather h...

Superconducting and normal properties of metallic amorphous systems

International Nuclear Information System (INIS)

Esquinazi, P.D.

1983-02-01

The superconducting and transport properties (superconducing critical temperature, superconducting critical currents, electric resistivity and thermal conductivity) of the amorphous alloys La 70 Cu 30 and Zr 70 Cu 30 prepared by melt spinning have been investigated. The modification of these properties when, the initial amorphous metals relax to other metastable state under thermal treatment at below crystallization temperatures, have also been studied. (M.E.L.) [es

Improved superconducting properties of La{sub 3}Co{sub 4}Sn{sub 13} with indium substitution

Energy Technology Data Exchange (ETDEWEB)

Neha, P.; Srivastava, P. [School of Physical Sciences, Jawaharlal Nehru University, New Delhi 110067 (India); Jha, R. [School of Physical Sciences, Jawaharlal Nehru University, New Delhi 110067 (India); National Physical Laboratory, New Delhi 110012 (India); Shruti [School of Physical Sciences, Jawaharlal Nehru University, New Delhi 110067 (India); Awana, V.P.S. [National Physical Laboratory, New Delhi 110012 (India); Patnaik, S., E-mail: spatnaik@mail.jnu.ac.in [School of Physical Sciences, Jawaharlal Nehru University, New Delhi 110067 (India)

2016-04-25

We report two fold increase in superconducting transition temperature of La{sub 3}Co{sub 4}Sn{sub 13} by substituting indium at the tin site. The transition temperature of this skutterudite related compound is observed to increase from 2.5 K to 5.1 K for 10% indium substituted sample. The band structure and density of states calculations also indicate such a possibility. The compounds exhibit type-II superconductivity and the values of lower critical field (H{sub c1}), upper critical field (H{sub c2}), Ginzburg–Landau coherence length (ξ), penetration depth (λ) and GL parameter (κ) are estimated to be 0.0028 T, 0.68 T, 21.6 nm, 33.2 nm and 1.53 respectively for La{sub 3}Co{sub 4}Sn{sub 11.7}In{sub 1.3}. Hydrostatic external pressure leads to decrease in transition temperature and the calculated pressure coefficient is −0.311 K/GPa. Flux pinning and vortex activation energies also improved with indium addition. Only positive frequencies are observed in phonon dispersion curve that relate to the absence of charge density wave or structural instability in the normal state. - Highlights: • Superconducting transition temperature of La{sub 3}Co{sub 4}Sn{sub 13} increases two fold by indium substitution. • Band structure and all basic superconducting parameters (e.g,. H{sub c1}, H{sub c2}, ξ,λ and κ are ascertained. • Dependence of superconducting properties under external pressure is studied.

Conventional superconductivity at 203 K at high pressures

Energy Technology Data Exchange (ETDEWEB)

Drozdov, Alexander; Eremets, Mikhail; Troyan, Ivan [Max-Planck-Institut fuer Chemie, Hahn-Meitner-Weg 1, 55128 Mainz (Germany); Ksenofontov, Vadim; Shylin, Sergii [Institut fuer Anorganische Chemie und Analytische Chemie, Johannes Gutenberg-Universitet Mainz, Staudingerweg 9, 55099 Mainz (Germany)

2016-07-01

A search for high, room temperature conventional superconductivity is promising as the Bardeen-Cooper-Schrieffer (BCS) theory in the Eliashberg formulation puts no apparent limits on T{sub c}. Materials with light elements are especially favorable as they provide high frequencies in the phonon spectrum. However only a moderately high T{sub c} = 39 K has been found in this search in MgB{sub 2}. We systematically studied metallic hydrogen and covalent hydrogen dominant compounds and found the record T{sub c} of 203 K at pressure 140 GPa in sulfur hydride. We proved occurrence of superconductivity by the sharp drop of the resistivity to zero; the decrease of T{sub c} with magnetic field; the pronounce isotope shift of T{sub c} in D{sub 2}S which evidences of a major role of phonons in the superconductivity; and the magnetic susceptibility measurements. The X-ray diffraction data confirmed that the superconductive phase has the predicted bcc structure. This phase can be considered as an atomic hydrogen superconductor stabilized by sulfur.

Pressure induced superconductivity in the antiferromagnetic Dirac material BaMnBi2

OpenAIRE

Huimin Chen; Lin Li; Qinqing Zhu; Jinhu Yang; Bin Chen; Qianhui Mao; Jianhua Du; Hangdong Wang; Minghu Fang

2017-01-01

The so-called Dirac materials such as graphene and topological insulators are a new class of matter different from conventional metals and (doped) semiconductors. Superconductivity induced by doing or applying pressure in these systems may be unconventional, or host mysterious Majorana fermions. Here, we report a successfully observation of pressure-induced superconductivity in an antiferromagnetic Dirac material BaMnBi2 with T c of ~4?K at 2.6?GPa. Both the higher upper critical field, ? 0 H...

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.

Research of mechanical and void properties of composite insulation for superconducting busbar

Energy Technology Data Exchange (ETDEWEB)

Huang, Xiongyi, E-mail: huangxy@ipp.ac.cn [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Li, Guoliang [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Clayton, Nicholas [ITER IO, Superconductor Systems & Auxiliaries Section, 13067 St Paul Lez Durance Cedex (France); Lu, Kun; Wang, Chunyu; Wang, Chao; Dai, Zhiheng [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Gung, Chen-yu; Devred, Arnaud [ITER IO, Superconductor Systems & Auxiliaries Section, 13067 St Paul Lez Durance Cedex (France); Song, Yuntao; Fang, Linlin [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China)

2017-01-15

Highlights: • Two curing methods for the pre-preg on the superconducting busbar are researched. • Vaccum bag and silicone rubber is used for pre-preg curing as complement of VPI in fusion filed. • The results of mechanical properties and void content is described and discussed. - Abstract: Pre-preg material has been widely-used in the industry of the aerospace, the wind power, which has many advantages on manufacture process, and can be chosen as an effective complementary insulation method for the Wet-winding and Vacuum Pressure Impregnation technology in the field of superconducting fusion magnets. ASIPP undertaken many engineering tasks on the superconducting coil and busbar design and manufacture for the large fusion device, the pre-preg material and the relevant curing technology were researched as a new method for the high voltage potential components in ITER Feeders, such as the busbars and current leads. Two types of Chinese industrial glass fiber pre-preg insulation composite material were studied and pre-qualified using vacuum bag and silicone rubber assistance technique in ASIPP. The mechanical properties including the ILSS and UTS at 77 K, and void content of this composites were measured and discussed in this paper in detail.

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

Nanolayers with advanced properties for superconducting nanoelectronics

International Nuclear Information System (INIS)

Prepelita, A.; Zdravkov, V.; Morari, R.; Socrovisciuc, A.; Antropov, E.; Sidorenko, A.

2011-01-01

Full text: Elaborated advanced technology for superconducting spintronics - technological process, based on magnetron sputtering of the metallic films with non-metallic protective layers, yields significant improvement in superconducting properties of thin Nb films and Nb/CuNi nanostructures in comparison with common methods of films deposition. The developed advanced technological process is patented (Patent RM number 175 from 31.03.2010). First experimental observation of the double re-entrant superconductivity in superconductor/ ferromagnetic nanostructures (Nb/Cu 41 Ni 59 bilayers) in dependence on the thickness of the ferromagnetic layer (Published in : A.S. Sidorenko, V.I. Zdravkov, J. Kehrle, R.Morari, E.Antropov, G. Obermeier, S. Gsell, M. Schreck, C. Muller, V.V. Ryazanov, S. Horn, R. Tidecks, L.R. Tagirov. Extinction and recovery of superconductivity by interference in superconductor/ferromagnet bilayers. In: Nanoscale Phenomena . Fundamentals and Applications,Ed. by H.Hahn, A.Sidorenko, I.Tiginyanu, Springer, 2009 p.1-10. Perspectives of applications: design of a new generation of superconducting spintronic devices - high frequency operating superconducting spin-switch for telecommunication and computers. (author)

High-pressure effects on isotropic superconductivity in the iron-free layered pnictide superconductor BaPd2As2

Science.gov (United States)

Abdel-Hafiez, M.; Zhao, Y.; Huang, Z.; Cho, C.-w.; Wong, C. H.; Hassen, A.; Ohkuma, M.; Fang, Y.-W.; Pan, B.-J.; Ren, Z.-A.; Sadakov, A.; Usoltsev, A.; Pudalov, V.; Mito, M.; Lortz, R.; Krellner, C.; Yang, W.

2018-04-01

While the layered 122 iron arsenide superconductors are highly anisotropic, unconventional, and exhibit several forms of electronic orders that coexist or compete with superconductivity in different regions of their phase diagrams, we find in the absence of iron in the structure that the superconducting characteristics of the end member BaPd2As2 are surprisingly conventional. Here we report on complementary measurements of specific heat, magnetic susceptibility, resistivity measurements, Andreev spectroscopy, and synchrotron high pressure x-ray diffraction measurements supplemented with theoretical calculations for BaPd2As2 . Its superconducting properties are completely isotropic as demonstrated by the critical fields, which do not depend on the direction of the applied field. Under the application of high pressure, Tc is linearly suppressed, which is the typical behavior of classical phonon-mediated superconductors with some additional effect of a pressure-induced decrease in the electronic density of states and the electron-phonon coupling parameters. Structural changes in the layered BaPd2As2 have been studied by means of angle-dispersive diffraction in a diamond-anvil cell. At 12 GPa and 24.2 GPa we observed pressure induced lattice distortions manifesting as the discontinuity and, hence discontinuity in the Birch-Murnaghan equation of state. The bulk modulus is B0=40 (6 ) GPa below 12 GPa and B0=142 (3 ) GPa below 27.2 GPa.

Superconducting Properties of Lead-Bismuth Films Controlled by Ferromagnetic Nanowire Arrays

Science.gov (United States)

Ye, Zuxin; Lyuksyutov, Igor F.; Wu, Wenhao; Naugle, Donald G.

2011-03-01

Superconducting properties of lead-bismuth (82% Pb and 18% Bi) alloy films deposited on ferromagnetic nanowire arrays have been investigated. Ferromagnetic Co or Ni nanowires are first electroplated into the columnar pores of anodic aluminum oxide (AAO) membranes. Superconducting Pb 82 Bi 18 films are then quench-condensed onto the polished surface of the AAO membranes filled with magnetic nanowires. A strong dependence of the Pb 82 Bi 18 superconducting properties on the ratio of the superconducting film thickness to the magnetic nanowire diameter and the material variety was observed.

The effect of pressure on the charge-density wave and superconductivity in ZrTe sub 3

CERN Document Server

Yamaya, K; Yasuzuka, S; Okajima, Y; Tanda, S

2002-01-01

The charge-density-wave (CDW) transition temperature, T sub C sub D sub W , of ZrTe sub 3 is found to increase for pressures up to 0.6 GPa, while the superconducting transition temperature, T sub c , decreases with increasing pressure. According to a band calculation, it is found that the pressure-induced enhancement of the CDW and suppression of the superconductivity are not simply explained by the effect of nesting of the Fermi surface, suggesting the possibility of a new relation for the competition between the CDW and superconductivity.

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. Th...

Surface ferromagnetism and superconducting properties of nanocrystalline niobium nitride

International Nuclear Information System (INIS)

Shipra, R.; Kumar, Nitesh; Sundaresan, A.

2013-01-01

Nanocrystalline δ-NbN x samples have been synthesized by reacting NbCl 5 and urea at three different temperatures. A comparison of their structural, magnetic, transport and thermal properties is reported in the present study. The size of the particles and their agglomeration extent increase with increasing reaction temperature. The sample prepared at 900 °C showed the highest superconducting transition temperature (T c ) of 16.2 K with a transition width, ∼1.8 K, as obtained from the resistivity measurement on cold-pressed bars. Above T c , magnetization measurements revealed the presence of surface ferromagnetism which coexists with superconductivity below T c . Heat capacity measurements confirm superconductivity with strong electron–phonon coupling constant. The sample prepared at 800 °C shows a lower T c (10 K) while that prepared at 700 °C exhibit no superconductivity down to the lowest temperature (3 K) measured. - Highlights: ► Synthesis of δ-NbN nanoparticles by urea nitridation of NbCl 5 . ► Superconducting transition temperature (T c ) is 16.2 K. ► Superconductivity and surface ferromagnetism coexist in the nanoparticles. ► Effect of size and agglomeration on the physical properties of nanoparticles

RF properties of superconducting Pb electroplated onto Cu

International Nuclear Information System (INIS)

Delayen, J.R.

1988-01-01

The properties of Pb as a superconducting material for high power rf applications are reviewed. The most common method of producing Pb superconducting resonators, which is by electrodeposition of a thin layer on a Cu substrate, is described, and some suggestions for further development are presented. 56 references, 11 figures, 1 table

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).

Crystal Structure and Superconductivity of PH ₃ at High Pressures

Energy Technology Data Exchange (ETDEWEB)

Liu, Hanyu [Geophysical; Department; Li, Yinwei [School; Gao, Guoying [State; Tse, John S. [Department; State; Naumov, Ivan I. [Geophysical

2016-02-04

We have performed a systematic structure search on solid PH3 at high pressures using the particle swarm optimization method. At 100–200 GPa, the search led to two structures which along with others have P–P bonds. These structures are structurally and chemically distinct from those predicted for the high-pressure superconducting H2S phase, which has a different topology (i.e., does not contain S–S bonds). Phonon and electron–phonon coupling calculations indicate that both structures are dynamically stable and superconducting. The pressure dependence and critical temperature for the monoclinic (C2/m) phase of 83 K at 200 GPa are in excellent agreement with a recent experimental report.

1D-transport properties of single superconducting lead nanowires

DEFF Research Database (Denmark)

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

2003-01-01

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......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...

High-pressure effects on the superconductivity of β-pyrochlore oxides AOs2O6

International Nuclear Information System (INIS)

Muramatsu, Takaki; Takeshita, Nao; Terakura, Chikeko; Takagi, Hidenori; Tokura, Yoshinori; Yonezawa, Shigeki; Muraoka, Yuji; Hiroi, Zenji

2006-01-01

High-pressure effects on the superconducting transitions of β-pyrochlore oxide superconductors AOs 2 O 6 (A=Cs, Rb, K) are studied by measuring resistivity under high pressures up to 16 GPa. The superconducting transition temperature T c first increases with increasing pressure in all the compounds 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 and 6 GPa for A=Rb and K and probably above 10 GPa for A=Cs. Characteristic changes in the temperature dependence of resistivity of RbOs 2 O 6 under high pressure. The residual resistivity largely increases with pressure above 4 GPa and, as a result, resistivity indicates small temperature dependence down to 4.2 K at 7 GPa and application of further pressure up to 10 GPa indicates that temperature dependence of resistivity decrease below 100 K. This characteristic behavior in the β-pyrochlore oxides may originate from the nesting of nearly octahedron shape of Fermi surface

Superconducting joint of Bi-2223/Ag superconducting tapes by diffusion bonding

International Nuclear Information System (INIS)

Guo Wei; Zou Guisheng; Wu Aiping; Wang Yanjun; Bai Hailin; Ren Jialie

2009-01-01

61-Filaments Bi-2223/Ag superconducting tapes have been joined by diffusion bonding. The critical currents (I C s) of the joints are obtained by using standard four probe method under no magnetic field in the liquid nitrogen. The microstructures of the joints are evaluated by the electron microscope in electron backscatter diffraction mode and the phase compositions of the superconducting cores of the joint and the original tape are determined by X-ray diffraction (XRD). The results show diffusion bonding is effective bonding technique for HTS tapes, and the bonding time is reduced greatly from hundreds of hours to a few hours, and the bonding pressure also changes from 140-4000 MPa to 3 MPa. Furthermore, the diffusion bonding joints sustain superconducting properties, and the critical current ratios (CCR O ) of the joints are in the range of 35%-80%. Microstructures of the typical joint display a good bonding and some defects existed in traditional method are avoided. XRD results show that the phase compositions of the superconducting cores have no obvious changes before and after diffusion bonding, which offers physical and material bases for high superconducting property of the joints.

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.

Uniaxial strain orientation dependence of superconducting transition temperature (Tc) and critical superconducting pressure (Pc) in β-(BDA-TTP)2I3.

Science.gov (United States)

Kikuchi, Koichi; Isono, Takayuki; Kojima, Masayuki; Yoshimoto, Haruo; Kodama, Takeshi; Fujita, Wataru; Yokogawa, Keiichi; Yoshino, Harukazu; Murata, Keizo; Kaihatsu, Takayuki; Akutsu, Hiroki; Yamada, Jun-ichi

2011-12-14

Dependence of the superconducting transition temperature (T(c)) and critial superconducting pressure (P(c)) of the pressure-induced superconductor β-(BDA-TTP)(2)I(3) [BDA-TTP = 2,5-bis(1,3-dithian-2-ylidene)-1,3,4,6-tetrathiapentalene] on the orientation of uniaxial strain has been investigated. On the basis of the overlap between the upper and lower bands in the energy dispersion curve, the pressure orientation is thought to change the half-filled band to the quarter-filled one. The observed variations in T(c) and P(c) are explained by considering the degree of application of the pressure and the degree of contribution of the effective electronic correlation at uniaxial strains with different orientations parallel to the conducting donor layer. © 2011 American Chemical Society

Effect of disorder on the superconducting properties of materials

International Nuclear Information System (INIS)

Brouers, F.; Derenne, M.

1982-01-01

The effect of the variation of the density states at the Fermi level on the critical superconductivity temperature TC of transition metal compounds is studied. This paper suggests using the technique of calculating the 5-fold degenerate d-band density of states from a continued fraction extension of a tight-binding Green function to study the relative importance of one dimensionality chain coupling, three dimensional interactions and the effect of disorder on the electronic and superconducting properties of complex phase and in particular A15 phases. The first results obtained for A15 phases density of states indicate that an extension of the suggested method can be of great interest to analyze the effect of disorder on superconductivity properties of complex phases

Robust zero resistance in a superconducting high-entropy alloy at pressures up to 190 GPa

Science.gov (United States)

Guo, Jing; Wang, Honghong; von Rohr, Fabian; Wang, Zhe; Cai, Shu; Zhou, Yazhou; Yang, Ke; Li, Aiguo; Jiang, Sheng; Wu, Qi; Cava, Robert J.; Sun, Liling

2017-12-01

We report the observation of extraordinarily robust zero-resistance superconductivity in the pressurized (TaNb)0.67(HfZrTi)0.33 high-entropy alloy--a material with a body-centered-cubic crystal structure made from five randomly distributed transition-metal elements. The transition to superconductivity (TC) increases from an initial temperature of 7.7 K at ambient pressure to 10 K at ˜60 GPa, and then slowly decreases to 9 K by 190.6 GPa, a pressure that falls within that of the outer core of the earth. We infer that the continuous existence of the zero-resistance superconductivity from 1 atm up to such a high pressure requires a special combination of electronic and mechanical characteristics. This high-entropy alloy superconductor thus may have a bright future for applications under extreme conditions, and also poses a challenge for understanding the underlying quantum physics.

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.

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

International Nuclear Information System (INIS)

Tajima, Tsuyoshi

2016-01-01

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.

Levitation properties of superconducting magnetic bearings using superconducting coils and bulk superconductors

Energy Technology Data Exchange (ETDEWEB)

Arai, Yuuki; Seino, Hiroshi; Nagashima, Ken [Railway Technical Research Institute, 2-8-38 Hikari-cho, Kokubunji-shi, Tokyo 185-8540 (Japan)

2010-11-15

We have been developing a flywheel energy storage system (FESS) with 36 MJ energy capacity for a railway system with superconducting magnetic bearings (SMBs). We prepared two kinds of models using superconducting coils and bulk superconductors (SCs). One model demonstrated SMB load capacity of 20 kN and the other model proved non-contact stable levitation and non-contact rotation with SMBs. Combining these results, the feasibility of a 36 MJ energy capacity FESS with SMBs completely inside a cryostat has been confirmed. In this paper, we report the levitation properties of SMBs in these models.

Levitation properties of superconducting magnetic bearings using superconducting coils and bulk superconductors

International Nuclear Information System (INIS)

Arai, Yuuki; Seino, Hiroshi; Nagashima, Ken

2010-01-01

We have been developing a flywheel energy storage system (FESS) with 36 MJ energy capacity for a railway system with superconducting magnetic bearings (SMBs). We prepared two kinds of models using superconducting coils and bulk superconductors (SCs). One model demonstrated SMB load capacity of 20 kN and the other model proved non-contact stable levitation and non-contact rotation with SMBs. Combining these results, the feasibility of a 36 MJ energy capacity FESS with SMBs completely inside a cryostat has been confirmed. In this paper, we report the levitation properties of SMBs in these models.

Investigation of superconducting properties of nanowires prepared by template synthesis

DEFF Research Database (Denmark)

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

2003-01-01

of the nanowires is small enough to ensure a one-dimensional 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......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...

High pressure driven superconducting critical temperature tuning in Sb{sub 2}Se{sub 3} topological insulator

Energy Technology Data Exchange (ETDEWEB)

Anversa, Jonas [Departamento de Física, Universidade Federal de Santa Maria, 97105-900, Santa Maria, RS (Brazil); Escola de Engenharia Civil, Faculdade Meridional, 99070-220, Passo Fundo, RS (Brazil); Chakraborty, Sudip, E-mail: sudiphys@gmail.com [Condensed Matter Theory Group, Department of Physics and Astronomy, Box 516, Uppsala University, S-75120 Uppsala (Sweden); Piquini, Paulo [Departamento de Física, Universidade Federal de Santa Maria, 97105-900, Santa Maria, RS (Brazil); Ahuja, Rajeev [Condensed Matter Theory Group, Department of Physics and Astronomy, Box 516, Uppsala University, S-75120 Uppsala (Sweden); Applied Materials Physics, Department of Materials and Engineering, Royal Institute of Technology (KTH), S-100 44 Stockholm (Sweden)

2016-05-23

In this letter, we are reporting the change of superconducting critical temperature in Sb{sub 2}Se{sub 3} topological insulator under the influence of an external hydrostatic pressure based on first principles electronic structure calculations coupled with Migdal–Eliashberg model. Experimentally, it was shown previously that Sb{sub 2}Se{sub 3} was undergoing through a transition to a superconducting phase when subjected to a compressive pressure. Our results show that the critical temperature increases up to 6.15 K under the pressure unto 40 GPa and, subsequently, drops down until 70 GPa. Throughout this pressure range, the system is preserving the initial Pnma symmetry without any structural transformation. Our results suggest that the possible relevant mechanism behind the superconductivity in Sb{sub 2}Se{sub 3} is primarily the electron–phonon coupling.

Superconducting properties of Pb82Bi18 films controlled by ferromagnetic nanowire arrays

International Nuclear Information System (INIS)

Ye Zuxin; Lyuksyutov, Igor F; Wu Wenhao; Naugle, Donald G

2011-01-01

The superconducting properties of Pb 82 Bi 18 alloy films deposited on ferromagnetic nanowire arrays have been investigated. Ferromagnetic Co or Ni nanowires are first electroplated into the columnar pores of anodic aluminum oxide (AAO) membranes. Superconducting Pb 82 Bi 18 films are then quench condensed onto the polished surface of the AAO membranes filled with magnetic nanowires. A strong dependence of the Pb 82 Bi 18 superconducting properties on the ratio of the superconducting film thickness to the magnetic nanowire diameter and material variety was observed.

Superconducting properties of Pb82Bi18 films controlled by ferromagnetic nanowire arrays

Science.gov (United States)

Ye, Zuxin; Lyuksyutov, Igor F.; Wu, Wenhao; Naugle, Donald G.

2011-02-01

The superconducting properties of Pb82Bi18 alloy films deposited on ferromagnetic nanowire arrays have been investigated. Ferromagnetic Co or Ni nanowires are first electroplated into the columnar pores of anodic aluminum oxide (AAO) membranes. Superconducting Pb82Bi18 films are then quench condensed onto the polished surface of the AAO membranes filled with magnetic nanowires. A strong dependence of the Pb82Bi18 superconducting properties on the ratio of the superconducting film thickness to the magnetic nanowire diameter and material variety was observed.

Pressure-induced unconventional superconductivity near a quantum critical point in CaFe2As2

International Nuclear Information System (INIS)

Kawasaki, S; Tabuchi, T; Zheng Guoqing; Wang, X F; Chen, X H

2010-01-01

75 As-zero-field nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) measurements are performed on CaFe 2 As 2 under pressure. At P = 4.7 and 10.8 kbar, the temperature dependencies of nuclear-spin-lattice relaxation rate (1/T 1 ) measured in the tetragonal phase show no coherence peak just below T 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.

Effect of pressure on spin fluctuations and superconductivity in heavy-fermion UPt3

International Nuclear Information System (INIS)

Willis, J.O.; Thompson, J.D.; Fisk, Z.; de Visser, A.; Franse, J.J.M.; Menovsky, A.

1985-01-01

We have determined the effect of hydrostatic pressure on the susceptibility, on the T 2 temperature dependence of the spin-fluctuation resistivity, and on superconductivity in UPt 3 . The spin-fluctuation temperature T/sub s/, derived from the slope of resistivity versus T 2 , is used within a Fermi-liquid picture to calculate the susceptibility chi at T = 0 K. The depression of this calculated chi with pressure agrees with the directly measured value partial lnchi/partialP = -24 Mbar -1 . Both the superconducting transition temperature T/sub c/ and the initial slope of the upper critical field also decrease under pressure. We find that partial lnT/sub c//partialP = -25 Mbar -1 and speculate upon correlations between chi and T/sub c/

Structural and superconducting properties of epitaxial Fe{sub 1+y}Se{sub 1-x}Te{sub x} thin films

Energy Technology Data Exchange (ETDEWEB)

Richter, Stefan; Yuan, Feifei; Grinenko, Vadim; Huehne, Ruben [Institute for Metallic Materials, IFW Dresden (Germany); Sala, Alberto; Putti, Marina [Dipartimento di Fisica, Universita di Genova (Italy)

2015-07-01

The iron based superconductor Fe(Se,Te) is in the center of much ongoing research. The reason for this is on the one hand its simple crystal structure, that consists only of stacked Fe(Se,Te) layers so that structural and superconducting properties can be connected more easily, on the other hand FeSe itself shows a high sensibility for strain and changes in stoichiometry and can have potentially very high critical temperatures under hydrostatic pressure or in monolayers. We investigate epitaxial thin films of Fe{sub 1+y}Se{sub 1-x}Te{sub x} grown by pulsed laser deposition on different single crystalline substrates. A high crystalline quality and a superconducting transition of up to about 20 K can be achieved using optimized deposition parameters. The influence of growth conditions, Te-doping, film thickness and post growth oxygen treatment on the structural and superconducting properties on these films will be presented in detail.

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(B_1-xC_x)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(B_1-xC_x)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.

Physical and chemical studies of superconduction properties of the intercalation compounds

International Nuclear Information System (INIS)

Eder, F.X.; Lerf, A.

1980-01-01

The superconducting properties of the intercalation compounds of layered dichalcogenides were studied. Our studies were concerned mainly to the alkali metal intercalation derivatives of TaS 2 and NbS 2 , and later on extended to the molecule intercalation compounds. The main difficulties with this class of superconductors result from varying material properties; these are therefore the subject of broad intensity in our investigations. The results received on the physical and chemical properties of the intercalation compounds is utilized for a phenomenological description of the factors mainly determining there superconducting properties. (orig.) [de

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.

Pressure-induced superconductivity of Ce{sub 2}Ni{sub 3}Ge{sub 5}

Energy Technology Data Exchange (ETDEWEB)

Nakashima, M. [Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan) and Research Center for Materials Science at Extreme Conditions, Osaka University, Toyonaka, Osaka 560-8531 (Japan)]. E-mail: mnaka@crystal.phys.sci.osaka-u.ac.jp; Kohara, H. [Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan); Thamizhavel, A. [Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan); Matsuda, T.D. [Advanced Science and Industrial Research Center, Japan Atomic Energy Research Institute, Tokai, Ibaraki, 319-1195 (Japan); Haga, Y. [Advanced Science and Industrial Research Center, Japan Atomic Energy Research Institute, Tokai, Ibaraki, 319-1195 (Japan); Hedo, M. [Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581 (Japan); Uwatoko, Y. [Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581 (Japan); Settai, R. [Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan); Onuki, Y. [Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan)

2006-05-01

The Neel temperature of Ce{sub 2}Ni{sub 3}Ge{sub 5} decreases with increasing pressure P and becomes zero at a critical pressure P{sub c}{approx}4GPa. The heavy fermion state was found to be formed around P{sub c}, in which pressure region superconductivity was found below 0.26K.

Similarity in the superconducting properties of chalcogenides, cuprate oxides and fullerides

International Nuclear Information System (INIS)

Tsendin, K.D.; Popov, B.P.; Denisov, D.V.

2004-01-01

The idea of Anderson pairs has been put forward for explanation of many extraordinary properties of chalcogenides glassy semiconductors. Recent decades made obvious that these pairs localized on the centers with negative effective correlation energy (negative-U centers) really exist in chalcogenides. If the concentration of negative-U centers is enough to create the pair band states, this can lead to superconductivity because Anderson pairs are Bose particles. In the present paper we show that several puzzling superconductivity properties of chalcogenides, high-temperature cuprate superconductors and fullerides are similar for these three groups of materials and can be naturally explained in the frame of negative-U centers model of superconductivity

Inhomogeneities and superconductivity in poly-phase Fe-Se-Te systems

Science.gov (United States)

Hartwig, S.; Schäfer, N.; Schulze, M.; Landsgesell, S.; Abou-Ras, D.; Blum, Ch. G. F.; Wurmehl, S.; Sokolowski, A.; Büchner, B.; Prokeš, K.

2018-02-01

The impact of synthesis conditions, post-preparation heating procedure, aging and influence of pressure on the superconducting properties of FeSe0.4Te0.6 crystals is reported. Two FeSe0.4Te0.6 single crystals were used in the study, prepared from stoichiometric melt but cooled down with very different cooling rates, and investigated using magnetic bulk and electrical-resistivity methods. The fast-cooled crystal contains large inclusions of Fe3Se2.1Te1.8 and exhibits bulk superconductivity in its as-prepared state, while the other is homogeneous and shows only traces of superconductivity. AC susceptibility measurements under hydrostatic pressure show that the superconducting transition temperature of the inhomogeneous crystal increases from 12.3 K at ambient pressure to Tsc = 17.9 K at 9 kbar. On the other hand, neither pressure nor mechanically-induced stress is sufficient to induce superconductivity in the homogeneous crystal. However, an additional heat treatment at 673 K followed by fast cooling down and/or long-term aging at ambient conditions leads to the appearance of bulk superconductivity also in the latter sample. This sample remains homogeneous on a scale down to few μm but shows an additional magnetic phase transition around 130 K suggesting that it must be inhomogeneous. For comparison also Fe3Se2.1Te1.8 polycrystals have been prepared and their magnetic properties have been studied. It appears that this phase is not superconducting by itself. It is concluded that nano-scale inhomogeneities that appear in the FeSexTe1-x system due to a spinodal decomposition in the solid state are necessary for bulk superconductivity, possibly due to minor changes in the crystal structure and microstructure. Macroscopic inclusions quenched by fast cooling from high temperatures lead obviously to strain and hence variations in the lattice constants, an effect that is further supported by application of pressure/stress.

Analysis of thermodynamic properties for high-temperature superconducting oxides

International Nuclear Information System (INIS)

Kushwah, S.S.; Shanker, J.

1993-01-01

Analysis of thermodynamic properties such as specific heat, Debye temperature, Einstein temperature, thermal expansion coefficient, bulk modulus, and Grueneisen parameter is performed for rare-earth-based, Tl-based, and Bi-based superconducting copper oxides. Values of thermodynamic parameters are calculated and reported. The relationship between the Debye temperature and the superconducting transition temperature is used to estimate the values of T c using the interaction parameters from Ginzburg. (orig.)

Theory of normal and superconducting properties of fullerene-based solids

International Nuclear Information System (INIS)

Cohen, M.L.

1992-10-01

Recent experiments on the normal-state and superconducting properties of fullerene-based solids are used to constrain the proposal theories of the electronic nature of these materials. In general, models of superconductivity based on electron pairing induced by phonons are consistent with electronic band theory. The latter experiments also yield estimates of the parameters characterizing these type H superconductors. It is argued that, at this point, a ''standard model'' of phonons interacting with itinerant electrons may be a good first approximation for explaining the properties of the metallic fullerenes

Giant Overlap between the Magnetic and Superconducting Phases of CeAu_{2}Si_{2} under Pressure

Directory of Open Access Journals (Sweden)

Z. Ren

2014-09-01

Full Text Available High pressure provides a powerful means for exploring unconventional superconductivity which appears mostly on the border of magnetism. Here, we report the discovery of pressure-induced heavy-fermion superconductivity up to 2.5 K in the antiferromanget CeAu_{2}Si_{2} (T_{N}≈10  K. Remarkably, the magnetic and superconducting phases are found to overlap across an unprecedentedly wide pressure interval from 11.8 to 22.3 GPa. Moreover, both the bulk T_{c} and T_{M} are strongly enhanced when increasing the pressure from 16.7 to 20.2 GPa. T_{c} reaches a maximum at a pressure slightly below p_{c}≈22.5  GPa, at which magnetic order disappears. Furthermore, the scaling behavior of the resistivity provides evidence for a continuous delocalization of the Ce 4f electrons associated with a critical end point lying just above p_{c}. We show that the maximum T_{c} of CeAu_{2}Si_{2} actually occurs at almost the same unit-cell volume as that of CeCu_{2}Si_{2} and CeCu_{2}Ge_{2}, and when the Kondo and crystal-field splitting energies become comparable. Dynamical mean-filed theory calculations suggest that the peculiar behavior in pressurized CeAu_{2}Si_{2} might be related to its Ce-4f orbital occupancy. Our results not only provide a unique example of the interplay between superconductivity and magnetism, but also underline the role of orbital physics in understanding Ce-based heavy-fermion systems.

Effect of pressure on the bandstructure and superconductivity in lutetium

International Nuclear Information System (INIS)

Asokamani, R.; Natarajan, S.; Rajagopalan, M.; Sundararajan, V.; Suvasini, M.B.; Iyakutti, K.

1984-08-01

The detailed bandstructure and superconducting behaviour of lutetium at 230 kbar pressure is reported here. The electronic contribution eta to the electron-phonon mass enhancement lambda is studied within the rigid muffin-tin (RMT) approximation. The pd and df matrix elements are expressed in terms of 'd' bandwidth, Fermi energy and muffin-tin zero. The variations of Grueneisen parameter and Debye temperature with pressure are studied and applied in the calculation of Tsub(c). The calculated Tsub(c) value agrees fairly well with the experimental value. The changes in the conduction bandwidth and the electronic specific heat coefficient with pressure are found to be in agreement with theoretical prediction. (author)

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

International Nuclear Information System (INIS)

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

2015-01-01

The evolution of the superconducting properties of round wires of (Ba,K)Fe 2 As 2 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. (paper)

Method for obtaining large levitation pressure in superconducting magnetic bearings

Science.gov (United States)

Hull, John R.

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.

Thermal history dependence of superconducting properties in La2CuO4+δ

International Nuclear Information System (INIS)

Hirayama, T.; Nakagawa, M.; Sumiyama, A.; Oda, Y.

1998-01-01

We studied the thermal history dependence of the superconducting properties below/above room temperature (RT) in the ceramic La 2 CuO 4-δ with excess oxygen. The phase separation (O-rich phase: superconducting and O-poor phase: antiferromagnetic) was concluded to occur above 373 K, in contrast with the usual report of the phase separation around 320 K. As for the superconducting phases, the well-known T c onset of 32 or 36 K, dependent on thermal history around 200 K, in the samples annealed in high-pressure oxygen gas, was not changed by thermal history between RT and 373 K. The samples electrochemically oxidized at RT included the phase with the high T c of 45 K, which was not changed by thermal history below RT, and the phase with the low T c of 32 or 36 K. The 45 K phase was changed into the low-T c phase by annealing at 373 K. The samples electrochemically oxidized at 333 K, which was accompanied with the diffusion of excess oxygen, showed gradual change of superconducting behavior: the single low-T c (32 or 36 K) phase (oxidation time = 24 h), coexistence of the low-T c phase and the high-T c (45 K) phase (36 h), and the single high T c phase (48 and 72 h). Thus, the single superconducting phase with the high T c of 45 K has been obtained, which showed a metallic behavior in normal resistivity and apparent changes of lattice constant in comparison with that of stoichiometric La 2 CuO 4 . (orig.)

Transition metal borides. Synthesis, characterization and superconducting properties

International Nuclear Information System (INIS)

Kayhan, Mehmet

2013-01-01

A systematic study was done on the synthesis and superconducting properties of metal rich transition metal borides. Five different binary systems were investigated including the boride systems of niobium, tantalum, molybdenum, tungsten and rhenium. High temperature solid state methods were used in order to synthesize samples of different transition metal borides of the composition M 2 B, MB, M 3 B 2 , MB 2 , and M 2 B 4 . The reactions were carried out in three different furnaces with different sample containers: the electric arc (copper crucible), the high frequency induction furnace (boron nitride, tantalum or glassy carbon crucibles), and the conventional tube furnace (sealed evacuated quartz ampoules). The products obtained were characterized with X-ray powder diffractometry, scanning electron microscopy and energy-dispersive X-ray spectroscopy. Phase analyses and crystal structure refinements using the Rietveld method and based on structure models known from literature were performed. A neutron diffraction measurement was done for W 2 B 4 to allow for a complete crystal structure determination, because of the presence of a heavy element like tungsten and a light element like boron that made it difficult to determine the accurate determination of the boron atom positions and occupancies from X-ray data. A new structure model for W 2 B 4 was proposed. Magnetic measurements in a SQUID magnetometer down to temperatures as low as 1.8 K were performed to several of the products in order to see if the transition metal borides become superconducting at low temperatures, and the results were compared with data from literature. Superconducting properties were found for the following compounds: NbB 2 (T C = 3.5 K), β-MoB (T C = 2.4 K), β-WB (T C = 2.0 K), α-WB (T C = 4.3 K), W 2 B 4 (T C = 5.4 K), Re 7 B 3 (T C = 2.4 K). A relationship between the superconducting properties and the compositional and structural features was discussed for metal diborides. Also it was

Optimization of the superconducting phase of hydrogen sulfide

Science.gov (United States)

Degtyarenko, N. N.; Masur, E. A.

2015-12-01

The electron and phonon spectra, as well as the densities of electron and phonon states of the SH3 phase and the stable orthorhombic structure of hydrogen sulfide SH2, are calculated for the pressure interval 100-225 GPa. It is found that the I4/ mmm phase can be responsible for the superconducting properties of metallic hydrogen sulfide along with the SH3 phase. Sequential stages for obtaining and conservation of the SH2 phase are proposed. The properties of two (SH2 and SH3) superconducting phases of hydrogen sulfide are compared.

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

Pressure dependence of the superconducting transition temperature of Rb3C60 up to 20 kbar

International Nuclear Information System (INIS)

Bud'ko, S.L.; Meng, R.L.; Chu, C.W.; Hor, P.H.

1991-01-01

AC susceptibility measurements of Rb 3 C 60 under hydrostatic pressure up to 20 kbar are reported. The superconducting transition temperature (T c ) decreases linearly under pressure with the pressure derivative dT c /dP = -0.78 K degrees/kbar

Electrophysical properties of crystals with superconducting inclusions of small sizes

International Nuclear Information System (INIS)

Sugakov, V.I.; Shevtsova, O.N.

2001-01-01

The effect of superconducting inclusions, incorporated in a semiconducting or dielectric matrix, on the electrophysical properties of the dielectric is studied. The critical magnetic field of a spherical isolated inclusion is determined in the assumption that the inclusion radius is less than or of the order of coherence length. The dependence of conductivity on temperature and magnetic field is calculated for a crystal with superconducting inclusions. In the calculations an assumption is made that the inclusion concentration is inadequate for the superconductivity to appear in a whole sample (i.e. below the thresh-old of percolation). It is shown that the presence of superconducting inclusions leads to a sharp increase of the sample conductivity at low temperatures, and to a strong dependence of conductivity on magnetic field (magnetoresistance). The magnetoresistance is caused by suppression of superconductivity in the inclusions with increasing magnetic field. The influence of variations in inclusion size on the temperature and magnetic field dependences of conductivity is studied

Superconductivity

International Nuclear Information System (INIS)

Taylor, A.W.B.; Noakes, G.R.

1981-01-01

This book is an elementray introduction into superconductivity. The topics are the superconducting state, the magnetic properties of superconductors, type I superconductors, type II superconductors and a chapter on the superconductivity theory. (WL)

Superconducting and normal state properties of carbon doped and neutron irradiated MgB2

International Nuclear Information System (INIS)

Wilke, R.H.T.; Samuely, P.; Szabo, P.; Holanova, Z.; Bud'ko, S.L.; Canfield, P.C.; Finnemore, D.K.

2007-01-01

Current research in MgB 2 focuses on the effects various types of perturbations have on the superconducting properties of this novel two-gap superconductor. In this article we summarize the effects of carbon doping and neutron irradiation in bulk MgB 2 . Low levels of carbon doping and light neutron irradiation result in significant enhancements in H c2 . At high fluences, where superconductivity is nearly fully suppressed, superconductivity can be restored through post exposure annealing. However, this results in a change in the interdependencies of the normal state and superconducting properties (ρ 0 , T c , H c2 ), with little or no enhancement in H c2

Properties of selected superconductive materials, 1978 supplement. Technical note

International Nuclear Information System (INIS)

Roberts, B.W.

1978-10-01

This report includes data on additional superconductive materials extracted from the world literature up to fall 1977 and is an addendum to the data set published in J. Phys. Chem. Ref. Data 5, no. 3, 581-821 (1976) (Reprint no. 84). The data presented are new values and have not been selected or compared to values (except for selected values of the elements) previously assembled by the Superconductive Materials Data Center. The properties included are composition, critical temperature, critical magnetic field, crystal structure and the results of negative experiments. Special tabulations of high magnetic field materials with Type II behavior and materials with organic components are included. All entries are keyed to the literature. A list of recent reviews centered on superconductive materials is included

Influence of pulse electric current on structure and superconducting properties of high temperature superconductor

International Nuclear Information System (INIS)

Rajchenko, A.I.; Flis, A.A.; Chernenko, L.I.; Kryuchkova, N.I.

1998-01-01

The influence of high-density pulse current treatment at room temperature on structure and superconducting properties of HTSC Y Ba 2 Cu 3 O x ceramics is studied. The structures of the samples are found to undergo appreciable changes as the density of pulse current is gradually increased from its minimum value; as a certain threshold value is attained, there occurs a melting-off of coarse grains with a partial destroying of intergrain contact areas followed by superconductivity loss. A further increase in the treatment current density results in a restoration of the superconducting properties probably due to the occurrence of aligned-with-current superconducting bridges between the melted-off grains. The superconducting transition temperature in the samples does not charge but subsequent thermal treatment causes this temperature to increase

A study on the development of high Tc superconducting materials

International Nuclear Information System (INIS)

Won, D. Y.; Hong, G. Y.; Lee, H. G.; Lee, H. J.; Kim, C. J.; Kwon, S. C.; Kim, K. B.; Kang, Y. H.; Chang, I. S.; Choi, M. J.

1992-01-01

The major work of this project aims to develop the frictionless superconducting bearing with a high speed. The high magnetization YBaCuO bulk superconductor was prepared by Quasi-melt process. The frictionless superconducting magnetic bearing standed a rotating bar with a speed of 75,000 rpm, which were operated by an electric controller. The low temperature chemical vapor deposition technique was developed. YBaCuO superconducting film showing a superconductivity above 77K was successfully prepared at 650 deg C. Effect of oxygen partial pressure, substrate, deposition temperature on the film properties were also investigated. (Author)

Transition metal borides. Synthesis, characterization and superconducting properties

Energy Technology Data Exchange (ETDEWEB)

Kayhan, Mehmet

2013-07-12

A systematic study was done on the synthesis and superconducting properties of metal rich transition metal borides. Five different binary systems were investigated including the boride systems of niobium, tantalum, molybdenum, tungsten and rhenium. High temperature solid state methods were used in order to synthesize samples of different transition metal borides of the composition M{sub 2}B, MB, M{sub 3}B{sub 2}, MB{sub 2}, and M{sub 2}B{sub 4}. The reactions were carried out in three different furnaces with different sample containers: the electric arc (copper crucible), the high frequency induction furnace (boron nitride, tantalum or glassy carbon crucibles), and the conventional tube furnace (sealed evacuated quartz ampoules). The products obtained were characterized with X-ray powder diffractometry, scanning electron microscopy and energy-dispersive X-ray spectroscopy. Phase analyses and crystal structure refinements using the Rietveld method and based on structure models known from literature were performed. A neutron diffraction measurement was done for W{sub 2}B{sub 4} to allow for a complete crystal structure determination, because of the presence of a heavy element like tungsten and a light element like boron that made it difficult to determine the accurate determination of the boron atom positions and occupancies from X-ray data. A new structure model for W{sub 2}B{sub 4} was proposed. Magnetic measurements in a SQUID magnetometer down to temperatures as low as 1.8 K were performed to several of the products in order to see if the transition metal borides become superconducting at low temperatures, and the results were compared with data from literature. Superconducting properties were found for the following compounds: NbB{sub 2} (T{sub C} = 3.5 K), β-MoB (T{sub C} = 2.4 K), β-WB (T{sub C} = 2.0 K), α-WB (T{sub C} = 4.3 K), W{sub 2}B{sub 4} (T{sub C} = 5.4 K), Re{sub 7}B{sub 3} (T{sub C} = 2.4 K). A relationship between the superconducting properties

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

Theoretical and experimental determination of mechanical properties of superconducting composite wire

International Nuclear Information System (INIS)

Gray, W.H.; Sun, C.T.

1976-07-01

The mechanical properties of a composite superconducting (NbTi/Cu) wire are characterized in terms of the mechanical properties of each constituent material. For a particular composite superconducting wire, five elastic material constants were experimentally determined and theoretically calculated. Since the Poisson's ratios for the fiber and the matrix material were very close, there was essentially no (less than 1 percent) difference among all the theoretical predictions for any individual mechanical constant. Because of the expense and difficulty of producing elastic constant data of 0.1 percent accuracy, and therefore conclusively determining which theory is best, no further experiments were performed

Superconducting and Structural Transitions in the β-Pyrochlore Oxide KOs2O6 under High Pressure

Science.gov (United States)

Ogusu, Hiroki; Takeshita, Nao; Izawa, Koichi; Yamaura, Jun-ichi; Ohishi, Yasuo; Tsutsui, Satoshi; Okamoto, Yoshihiko; Hiroi, Zenji

2010-11-01

Rattling-induced superconductivity in the β-pyrochlore oxide KOs2O6 is investigated under high pressure up to 5 GPa. Resistivity measurements in a high-quality single crystal reveal a gradual decrease in the superconducting transition temperature Tc from 9.7 K at 1.0 GPa to 6.5 K at 3.5 GPa, followed by a sudden drop to 3.3 K at 3.6 GPa. Powder X-ray diffraction experiments show a structural transition from cubic to monoclinic or triclinic at a similar pressure. The sudden drop in Tc is ascribed to this structural transition, by which an enhancement in Tc due to a strong electron-rattler interaction present in the low-pressure cubic phase is abrogated as the rattling of the K ion is completely suppressed or weakened in the high-pressure phase of reduced symmetry. In addition, we find two anomalies in the temperature dependence of resistivity in the low-pressure phase, which may be due to subtle changes in rattling vibration.

Elastic properties of superconducting bulk metallic glasses

International Nuclear Information System (INIS)

Hempel, Marius

2015-01-01

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.

Structural studies of type N superconductive compounds: R2-xCexCuO4±δ (R = Gd, Eu, Sm, Nd, Pr); influences of chemical treatments on physical properties

International Nuclear Information System (INIS)

Vigoureux, P.

1995-06-01

Different chemical treatments of R 2-x Ce x CuO 4±δ 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 2 planes, links between deformation and superconductivity and magnetic properties. (A.B.)

The Influence of Grain Boundaries on the Properties of Superconducting Radio Frequency Cavity Niobium

Science.gov (United States)

Sung, Zu Hawn

Grain boundaries (GBs) in niobium are multiply connected defects that may be responsible for significant performance degradation in superconducting radio frequency (RF) cavities. Magneto optical (MO) studies show that early flux penetration often occurs at GBs. One possible mechanism is that a locally reduced superconducting gap (Delta) at the GB reduces the depairing current density (Jb) and thus leads to a local reduction of the critical field. Alternatively vortices may penetrate the GB preferentially because of field enhancement at a GB groove, or for other reasons. In all these cases, the effect of high RF fields is to produce additional power dissipation, which in turn produces a reduction in quality factor (Q 0) and leads to a premature quench of the cavity. To further our understanding of the superconducting properties of SRF-quality Nb, we made extensive superconducting characterizations by magneto-optical imaging, which allowed assessment of the uniformity of properties on scales down to about 5 microm and by direct transport voltage-current methods in single and bi-crystals treated by standard cavity optimization treatments of BCP (buffered chemical treatment) and EP (electropolishing). We correlated these superconducting characterizations to microstructural properties using scanning laser and scanning electron microscopy and then thinned some samples to examine them at the nanometer scale using analytical transmission electron microscopy (TEM). We also developed special metallographic sample preparation techniques that allowed us to apply these experimental approaches to very soft superconducting RF niobium in the polished conditions characteristics of a real inner cavity surface. Using MO imaging, we found that GBs can preferentially admit flux penetration when the plane of a GB is aligned parallel to the vector of the external magnetic field. In DC transport in the superconducting state, we found preferential flux flow at the GB and could detect the

A study on the effect of tantalum-impurity content on the superconducting properties of niobium materials used for making superconducting radio frequency cavities

Science.gov (United States)

Roy, S. B.; Sharath Chandra, L. S.; Chattopadhyay, M. K.; Tiwari, M. K.; Lodha, G. S.; Myneni, G. R.

2012-11-01

Niobium materials in highly pure form are used in the fabrication of superconducting radio frequency cavities. We present here a study of the superconducting properties of such niobium materials that have been used in the fabrication of high accelerating gradient superconducting radio frequency cavities after determining their tantalum-impurity contents using a synchrotron-based x-ray fluorescence spectroscopy technique. Our results show that there is a small change in superconducting parameters such as TC,HC1 and HC2 when the tantalum-impurity content varies from ≈150 to ≈1300 ppm. In contrast, a buffered chemical polishing of the same niobium samples changes all these superconducting parameters more significantly. The implications of these results on the performance of niobium superconducting radio frequency cavities are discussed.

Superconducting Open-Framework Allotrope of Silicon at Ambient Pressure

Science.gov (United States)

Sung, Ha-Jun; Han, W. H.; Lee, In-Ho; Chang, K. J.

2018-04-01

Diamond Si is a semiconductor with an indirect band gap that is the basis of modern semiconductor technology. Although many metastable forms of Si were observed using diamond anvil cells for compression and chemical precursors for synthesis, no metallic phase at ambient conditions has been reported thus far. Here we report the prediction of pure metallic Si allotropes with open channels at ambient pressure, unlike a cubic diamond structure in covalent bonding networks. The metallic phase termed P 6 /m -Si6 can be obtained by removing Na after pressure release from a novel Na-Si clathrate called P 6 /m -NaSi6 , which is predicted through first-principles study at high pressure. We identify that both P 6 /m -NaSi6 and P 6 /m -Si6 are stable and superconducting with the critical temperatures of about 13 and 12 K at ambient pressure, respectively. The prediction of new Na-Si and Si clathrate structures presents the possibility of exploring new exotic allotropes useful for Si-based devices.

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

Dependence of the superconducting transition temperature of the filled skutterudite compound PrPt{sub 4}Ge{sub 12} on hydrostatic pressure

Energy Technology Data Exchange (ETDEWEB)

Foroozani, N. [Department of Physics, Washington University, St. Louis, MO 63130 (United States); Hamlin, J.J. [Department of Physics, University of California, San Diego, La Jolla, CA 92093 (United States); Schilling, J.S., E-mail: jss@wuphys.wustl.edu [Department of Physics, Washington University, St. Louis, MO 63130 (United States); Baumbach, R.E.; Lum, I.K.; Shu, L.; Huang, K.; Maple, M.B. [Department of Physics, University of California, San Diego, La Jolla, CA 92093 (United States)

2013-02-14

Highlights: ► Superconductivity in the filled skutterudite PrPt{sub 4}Ge{sub 12}. ► Dependence of T{sub c} on purely hydrostatic pressure to 0.6 GPa. ► Comparison of lattice pressure to external pressure effects on superconductivity. ► Evidence for magnetic pair-breaking effects. -- Abstract: The temperature-dependent ac susceptibility of the filled skutterudite superconductor PrPt{sub 4}Ge{sub 12} has been measured under hydrostatic He-gas pressure to 0.58 GPa. The superconducting transition temperature T{sub c} decreases linearly with pressure P from 7.91 K at ambient pressure to 7.83 K at 0.58 GPa, giving the rate dT{sub c}/dP = −0.19 ± 0.03 K/GPa. Evidence is presented that suggests that the value of T{sub c} in this compound is slightly reduced due to magnetic pair-breaking effects from the Pr{sup 3+} cations.

High-temperature superconducting phase of HBr under pressure predicted by first-principles calculations

Science.gov (United States)

Gu, Qinyan; Lu, Pengchao; Xia, Kang; Sun, Jian; Xing, Dingyu

2017-08-01

The high pressure phases of HBr are explored with an ab initio crystal structure search. By taking into account the contribution of zero-point energy (ZPE), we find that the P 4 /n m m phase of HBr is thermodynamically stable in the pressure range from 150 to 200 GPa. The superconducting critical temperature (Tc) of P 4 /n m m HBr is evaluated to be around 73 K at 170 GPa, which is the highest record so far among binary halogen hydrides. Its Tc can be further raised to around 95K under 170 GPa if half of the bromine atoms in the P 4 /n m m HBr are substituted by the lighter chlorine atoms. Our study shows that, in addition to lower mass, higher coordination number, shorter bonds, and more highly symmetric environment for the hydrogen atoms are important factors to enhance the superconductivity in hydrides.

Superconducting selenides intercalated with organic molecules: synthesis, crystal structure, electric and magnetic properties, superconducting properties, and phase separation in iron based-chalcogenides and hybrid organic-inorganic superconductors

Science.gov (United States)

Krzton-Maziopa, Anna; Pesko, Edyta; Puzniak, Roman

2018-06-01

Layered iron-based superconducting chalcogenides intercalated with molecular species are the subject of intensive studies, especially in the field of solid state chemistry and condensed matter physics, because of their intriguing chemistry and tunable electric and magnetic properties. Considerable progress in the research, revealing superconducting inorganic–organic hybrid materials with transition temperatures to superconducting state, T c, up to 46 K, has been brought in recent years. These novel materials are synthesized by low-temperature intercalation of molecular species, such as solvates of alkali metals and nitrogen-containing donor compounds, into layered FeSe-type structure. Both the chemical nature as well as orientation of organic molecules between the layers of inorganic host, play an important role in structural modifications and may be used for fine tuning of superconducting properties. Furthermore, a variety of donor species compatible with alkali metals, as well as the possibility of doping also in the host structure (either on Fe or Se sites), makes this system quite flexible and gives a vast array of new materials with tunable electric and magnetic properties. In this review, the main aspects of intercalation chemistry are discussed with a particular attention paid to the influence of the unique nature of intercalating species on the crystal structure and physical properties of the hybrid inorganic–organic materials. To get a full picture of these materials, a comprehensive description of the most effective chemical and electrochemical methods, utilized for synthesis of intercalated species, with critical evaluation of their strong and weak points, related to feasibility of synthesis, phase purity, crystal size and morphology of final products, is included as well.

Study on the origin of pressure-induced superconductivity of Cs3C60

International Nuclear Information System (INIS)

Fujiki, S.; Kubozono, Y.; Takabayashi, Y.; Kashino, S.; Kobayashi, M.; Ishii, K.; Suematsu, H.

2001-01-01

Physical properties of bco phase of Cs 3+α C 60 (α=0.0-1.0) and A15 phase of Cs 3 C 60 are studied by X-ray diffraction, ESR, AC susceptibility, resistivity and Raman. The ESR of Cs 300(6) C 60 showed a broad peak of ∼380 G due to conduction electron, while no broad peak was observed in the ESR of bco Cs 3+α C 60 (α≠0.0) and A15 phase. This shows that only bco phase of Cs 3 C 60 is metallic. The AC susceptibility of bco phase of Cs 3.2(3) C 60 and Cs 3.5(1) C 60 showed no superconducting transition above 1.3 K even under high pressure, and the resistivity was 0.52 Ω cm for both samples

A study on the effect of tantalum-impurity content on the superconducting properties of niobium materials used for making superconducting radio frequency cavities

International Nuclear Information System (INIS)

Roy, S B; Sharath Chandra, L S; Chattopadhyay, M K; Tiwari, M K; Lodha, G S; Myneni, G R

2012-01-01

Niobium materials in highly pure form are used in the fabrication of superconducting radio frequency cavities. We present here a study of the superconducting properties of such niobium materials that have been used in the fabrication of high accelerating gradient superconducting radio frequency cavities after determining their tantalum-impurity contents using a synchrotron-based x-ray fluorescence spectroscopy technique. Our results show that there is a small change in superconducting parameters such as T C ,H C1 and H C2 when the tantalum-impurity content varies from ≈150 to ≈1300 ppm. In contrast, a buffered chemical polishing of the same niobium samples changes all these superconducting parameters more significantly. The implications of these results on the performance of niobium superconducting radio frequency cavities are discussed. (paper)

Mechanical properties of partially meltable superconducting YBa/sub 2/Cu/sub 3/O/sub 7-x/

International Nuclear Information System (INIS)

Selvamanickam, V.; Salama, K.

1988-01-01

Partial melting has been suggested as a method for the processing of the high temperatures superconducting YBa/sub 2/Cu/sub 3/O/sub 7-x/ to improve the current carrying capacity in this material. The authors have investigated the possibility of using this method for the improvement of bulk mechanical properties in addition to those related to superconductivity. Four parameters, namely, oxygen annealing temperature, melting temperature, melting time and cooling rate are identified and studied. Each parameter is varied individually and its effects on microstructure and mechanical and superconducting properties are examined. The results indicate that the properties of superconducting YBa/sub 2/Cu/sub 3/O/sub 7-x/ can be improved significantly using the proper melting temperature, melting time, cooling rate and oxygen annealing temperature

Deposition of superconducting (Cu, C)-Ba-O films by pulsed laser deposition at moderate temperature

International Nuclear Information System (INIS)

Yamamoto, Tetsuro; Kikunaga, Kazuya; Obara, Kozo; Terada, Norio; Kikuchi, Naoto; Tanaka, Yasumoto; Tokiwa, Kazuyasu; Watanabe, Tsuneo; Sundaresan, Athinarayanan; Shipra

2007-01-01

Superconducting (Cu, C)-Ba-O thin films have been epitaxially grown on (100) SrTiO 3 at a low growth temperature of 500-600 deg. C by pulsed laser deposition. The dependences of their crystallinity and transport properties on preparation conditions have been investigated in order to clarify the dominant parameters for carbon incorporation and the emergence of superconductivity. It has been revealed that the CO 3 content in the films increases with increasing both the parameters of partial pressure of CO 2 during film growth and those of growth rate and enhancement of superconducting properties. The present study has also revealed that the structural and superconducting properties of the (Cu, C)-Ba-O films are seriously deteriorated by the irradiation of energetic particles during deposition. Suppression of the radiation damage is another key for a high and uniform superconducting transition. By these optimizations, a superconducting onset temperature above 50 K and a zero-resistance temperature above 40 K have been realized

Understanding and application of superconducting materials

International Nuclear Information System (INIS)

Moon, Byeong Mu; Lee, Chun Heung

1997-02-01

This book deals with superconducting materials, which contains from basic theory to application of superconducting materials. The contents of this book are mystery of superconducting materials, properties of superconducting materials, thermodynamics of superconducting materials, theoretical background of superconducting materials, tunnelling and quantum interference, classification and properties of superconducting materials, high temperature superconducting materials, production and analysis of superconducting materials and application of superconducting materials.

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).

Coexistence of antiferromagnetism and superconductivity in CePt2In7

Energy Technology Data Exchange (ETDEWEB)

Bauer, Eric D [Los Alamos National Laboratory; Sidorov, Vladimir A [Los Alamos National Laboratory; Lee, Han O [Los Alamos National Laboratory; Kurita, Nobuyuki [Los Alamos National Laboratory; Ronning, F [Los Alamos National Laboratory; Movshovich, R [Los Alamos National Laboratory; Thompson, J D [Los Alamos National Laboratory

2009-01-01

The physical properties of CePt{sub 2}In{sub 7} are presented at pressures up to 3.12 GPa. Antiferromagnetic order occurs at T{sub N} = 5.5 K at ambient pressure and first increases with pressure up to P {approx} 1.5 GPa, then decreases with further applied pressure up to 3.12 GPa. Another feature, attributed to superconductivity, is observed at 1 K at 1 GPa in the specific heat that grows in magnitude and increases to 2.1 K when the magnetism is weak at 3.12 GPa. Therefore, CePt{sub 2}In{sub 7} displays an evolution with pressure and a coexistence of magnetism and superconductivity that is remarkably similar to that of the heavy fermion superconductor CeRhIn{sub 5}.

Superconducting properties of a copper-ternary alloy

International Nuclear Information System (INIS)

Sharma, R.G.; Aleksivskii, N.E.

1975-01-01

The superconducting properties of a copper-ternary alloy of the type Cu 93 Nb 5 Sn 2 , subjected to a variety of mechanical and heat treatments, are discussed. The as-cast alloy does not turn superconducting down to 4.5K; but the cold-work and subsequent prescribed heat treatments are found to raise the transition temperature Tsub(c) to values as high as 18.1K and the critical current density Jsub(c) (of the Nb 3 Sn formed during annealing) to a value of 3.6x10 5 Acm -2 (at 4.2K and 30kOe). Various possibilities to improve Jsub(c) of this alloy to still higher values are discussed. The as-cast alloy is ductile, easy to draw, and economical from a technical point of view, and the annealed wires and strips are flexible enough for winding. (author)

Experimental Investigation of Magnetic Superconducting and other Phase Transitions in Novel f-Electron Materials at Ultra-high Pressures using Designer Diamond Anvils

International Nuclear Information System (INIS)

Maple, M. Brian; Jeffries, Jason R.; Ho, Pei-Chun; Butch, Nicholas P.

2004-01-01

Pressure is often used as a controlled parameter for the investigation of condensed matter systems. In particular, pressure experiments can provide valuable information into the nature of superconductivity, magnetism, and the coexistence of these two phenomena. Some f-electron, heavy-fermion materials display interesting and novel behavior at moderately low pressures achievable with conventional experimental techniques; however, a growing number of condensed matter systems require ultrahigh pressure techniques, techniques that generate significantly higher pressures than conventional methods, to sufficiently explore their important properties. To that end, we have been funded to develop an ultrahigh pressure diamond anvil cell facility at the University of California, San Diego (UCSD) in order to investigate superconductivity, magnetism, non-Fermi liquid behavior, and other phenomena. Our goals for the first year of this grant were as follows: (a) set up and test a suitable refrigerator; (b) set up a laser and spectrometer fluorescence system to determine the pressure within the diamond anvil cell; (c) perform initial resistivity measurements at moderate pressures from room temperature to liquid helium temperatures (∼1K); (d) investigate f-electron materials within our current pressure capabilities to find candidate materials for high-pressure studies. During the past year, we have ordered almost all the components required to set up a diamond anvil cell facility at UCSD, we have received and implemented many of the components that have been ordered, we have performed low pressure research on several materials, and we have engaged in a collaborative effort with Sam Weir at Lawrence Livermore National Lab (LLNL) to investigate Au4V under ultrahigh pressure in a designer diamond anvil cell (dDAC). This report serves to highlight the progress we have made towards developing an ultrahigh pressure research facility at UCSD, the research performed in the past year, as

Evolution of superconducting properties with disorder in epitaxial NbN films

International Nuclear Information System (INIS)

Chockalingam, S P; Chand, Madhavi; Jesudasan, John; Raychaudhuri, Pratap; Tripathi, Vikram

2009-01-01

NbN is a conventional BCS superconductor in which disorder can be tuned from moderately clean limit to dirty limit without affecting its epitaxial nature. We studied the superconducting properties of epitaxial NbN films of different disorder characterized by k F l ranging from 8.77 to 2.56 through the transport measurements. Using reactive magnetron sputtering NbN films of different disorder are deposited by varying the sputtering power and amount of N 2 in Ar:N 2 mixture of sputtering gas. The disorder parameter k F l is obtained from the carrier density (n) and the resistivity (ρ) of the films. NbN films with higher disorder have lower transition temperature (T c ) and larger resistivity which decreases with decreasing disorder. The carrier density determined from Hall measurements show that highly disordered films have lower carrier density and vice versa. Our studies show that NbN is a good system to investigate the effects of disorder on superconductivity where the superconducting properties evolve with the disorder in thin films.

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.

Influence of annealing atmosphere on structural and superconducting properties of MgB{sub 2} thin films

Energy Technology Data Exchange (ETDEWEB)

Gregor, M., E-mail: gregor@fmph.uniba.sk; Plecenik, T.; Sobota, R.; Brndiarova, J.; Roch, T.; Satrapinskyy, L.; Kus, P.; Plecenik, A.

2014-09-01

Highlights: • Superconducting MgB{sub 2} thin film were deposited by co-deposition using the thermal and e-beam evaporation. • Ex situ annealing process was done using various atmospheres. • Influence of annealing atmosphere and temperature on superconducting and structural properties were studied. • Possible mechanisms of the formation and crystallization of MgB{sub 2} thin film are discussed. - Abstract: Influence of an ex situ annealing temperature and atmosphere on chemical composition and structural and superconducting properties of MgB{sub 2} thin films deposited by vacuum evaporation has been investigated. The annealing has been done in Ar, N{sub 2} and Ar + 5%H{sub 2} atmospheres at pressure of 700 Pa and temperature varying from 700 to 800 °C. It has been shown that annealing in Ar and N{sub 2} atmosphere at 700–800 °C produces relatively thick MgO layer on the surface of the films, while creation of such layer is highly reduced if the annealing is done in reducing Ar + 5%H{sub 2} atmosphere. The XPS and XRD results suggest that the MgO layer prevents out-diffusion of Mg from the film during the annealing, what assures better stoichiometry of the films as well as creation of larger MgB{sub 2} grains. The films with the highest amount of MgO on the surface, annealed in nitrogen atmosphere, thus paradoxically exhibited the highest critical temperature of T{sub c0} = 34.8 K with very sharp transition width of 0.1 K.

Impact of radiation exposure on mechanical and superconducting properties of Bi-2212 superconductor ceramics

International Nuclear Information System (INIS)

Azlan Abdul Rahman; Nasri Abdul Hamid; Abdul Aziz Mohamed; Mohd Shahrul Nizam Abdullah; Samsul Isman; Hidayah Zainal

2013-01-01

Full-text: For practical applications of high-temperature superconductor ceramics, the compounds must be able to sustain extreme mechanical stress and external magnetic field. Bi-2212 superconductor is one of the existing superconductors that are commonly used in various applications. Improvement in the microstructure enhanced the connectivity of the adjacent grains within the superconducting grains, and as such improved the mechanical strength of the ceramics. The ability of the superconductor ceramics to sustain superconducting properties in external magnetic field is also required. The compounds must be able to maintain high transport critical current density (Jc) in magnetic field. Another potential application of superconductors is at the nuclear facilities. Thus, study on the impact of radiation exposure on the mechanical and superconducting properties is very important to gauge the viability of superconductor ceramics in such environment. In this study, the mechanical and superconducting properties between exposure and non-irradiated samples are compared. Characterization will be done by the temperature dependence on electrical resistance measurements, X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and measurements of transport critical current (Jc) dependence on temperature in magnetic field. (author)

Hydrostatic Pressure Study on 3-K Phase Superconductivity in Sr2RuO4-Ru Eutectic Crystals by AC Magnetic Susceptibility Measurements

International Nuclear Information System (INIS)

Yaguchi, Hiroshi; Watanabe, Hiromichi; Sakaue, Akira

2012-01-01

We have investigated the effect of hydrostatic pressure on 3-K phase superconductivity in Sr 2 RuO 4 -Ru eutectic crystals by means of AC magnetic susceptibility measurements. We have found that the application of hydrostatic pressure suppresses the superconducting transition temperature T c of the 3-K phase with a pressure coefficient of dT c /dP ≈ −0.2 K/GPa, similar to the case of the 1.5-K phase. We have also observed that the effect of hydrostatic pressure on the 3-K phase seems to be elastic whilst that of uniaxial pressure is plastic.

Structure and superconducting properties of Nb-Zr alloy films made by a high-rate sputtering

International Nuclear Information System (INIS)

Sekine, Hisashi; Inoue, Kiyoshi; Tachikawa, Kyoji

1978-01-01

Superconducting Nb-Zr alloy films have been prepared by a continuous high-rate sputtering on tantalum substrates. A deposition rate of 330 nm/min has been attained. The compositional profile in the Nb-Zr film is quite uniform and the film has nearly the same composition as that of the target. The films deposited in a pure argon atmosphere show a columnar structure grown perpendicular to the substrate. The grain size strongly depends on the substrate temperature. The phase transformations in the Nb-Zr film become more apparent and the structure becomes closer to the equilibrium state as the film is deposited in higher atmosphere pressures and/or at lower target voltages. The superconducting transition temperature T sub(c) of the films is about the same as that of bulk samples. The dependence of T sub(c) on the substrate temperature is explainable on the phase transformations in the film. Critical current density J sub(c) and its anisotropy is closely related to the grain structure of the film. Grain boundaries seem to act as the most predominant flux pinning centers in the films. Effects of oxygen in the sputtering atmosphere on the structure and superconducting properties of the Nb-Zr films have been also investigated. Oxygen significantly decreases the grain size of the film. Oxygen increases J sub(c) but decreases T sub(c) of the film. (auth.)

Superconductivity in graphite intercalation compounds

International Nuclear Information System (INIS)

Smith, Robert P.; Weller, Thomas E.; Howard, Christopher A.; Dean, Mark P.M.; Rahnejat, Kaveh C.; Saxena, Siddharth S.; Ellerby, Mark

2015-01-01

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 6 and YbC 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

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.

Superconducting properties of Ca1−xRExFe2As2 (RE: Rare Earths)

International Nuclear Information System (INIS)

Tamegai, T.; Ding, Q.P.; Ishibashi, T.; Nakajima, Y.

2013-01-01

Highlights: ► Superconducting properties in rare-earth doped CaFe 2 As 2 single crystals are characterized. ► Sharp resistive transitions with small anisotropy parameter of ∼1.75 are observed. ► Average critical current density is much smaller than other iron-based superconductors. ► Magneto-optical imaging confirms very inhomogeneous superconducting state. -- Abstract: We have grown rare-earth doped CaFe 2 As 2 single crystals and characterized their normal and superconducting properties. Temperature dependence of resistivity and its absolute value suggest good metallic conduction, suppressing antiferromagnetic (AF) transition in the undoped sample. Hall coefficient shows little temperature dependence, consistent with the suppression AF state. Superconducting transitions characterized by resistivity drops in magnetic fields for both parallel to c-axis and ab-plane are reasonably sharp with a weak anisotropy parameter ∼1.75. Despite these observations, average critical current density estimated from the bulk magnetization is orders of magnitude smaller than other typical iron-based superconductors. Magneto-optical imaging confirms very inhomogeneous superconducting state

Three-terminal superconducting devices

International Nuclear Information System (INIS)

Gallagher, W.J.

1985-01-01

The transistor has a number of properties that make it so useful. The authors discuss these and the additional properties a transistor would need to have for high performance applications at temperatures where superconductivity could contribute advantages to system-level performance. These properties then serve as criteria by which to evaluate three-terminal devices that have been proposed for applications at superconducting temperatures. FETs can retain their transistor properties at low temperatures, but their power consumption is too large for high-speed, high-density cryogenic applications. They discuss in detail why demonstrated superconducting devices with three terminals -Josephson effect based devices, injection controlled weak links, and stacked tunnel junction devices such as the superconducting transistor proposed by K. Gray and the quiteron -- each fail to have true transistor-like properties. They conclude that the potentially very rewarding search for a transistor compatible with superconductivity in high performance applications must be in new directions

Superconductivity

International Nuclear Information System (INIS)

Kakani, S.L.; Kakani, Shubhra

2007-01-01

The monograph provides readable introduction to the basics of superconductivity for beginners and experimentalists. For theorists, the monograph provides nice and brief description of the broad spectrum of experimental properties, theoretical concepts with all details, which theorists should learn, and provides a sound basis for students interested in studying superconducting theory at the microscopic level. Special chapter on the theory of high-temperature superconductivity in cuprates is devoted

Computer simulations of quench properties of thin, large superconducting solenoid magnets

International Nuclear Information System (INIS)

Kishimoto, Takeshi; Mori, Shigeki; Noguchi, Masaharu

1983-01-01

Measured quench data of a 1 m diameter x 1 m thin superconducting solenoid magnet with a single layer aluminum-stabilized NbTi/Cu superconductor of 269 turns were fitted by computer simulations using the one-dimensional approximation. Parameters obtained were used to study quench properties of a 3 m diameter x 5 m (1.5 Tesla) thin superconducting solenoid magnet with a stored magnetic energy of 30 x 10 6 J. Conductor dimensions with which the solenoid could be built substantially safe for the full field quench were optimized. (author)

Influence of laser sputtering parameters on orientation of cerium oxide buffer layer on sapphire and properties of YBa2Cu3Ox superconducting film

International Nuclear Information System (INIS)

Mozhaev, P.B.; Ovsyannikov, G.A.; Skov, J.L.

1999-01-01

Effect of laser sputtering parameters on crystalline properties of CeO 2 buffer layers grown on (1102) orientation sapphire substrate and on properties of YBa 2 Cu 3 O x superconducting thin films was studied. It was shown that depending on the sputtering conditions one might observe growth of CeO 2 (100) and (111) orientations. Varying heater temperature, chamber pressure and density of laser ray energy on the target one managed to obtain mono-oriented buffer layer of the desired orientation [ru

Theoretical study of stability and superconductivity of ScHn (n =4 -8 ) at high pressure

Science.gov (United States)

Qian, Shifeng; Sheng, Xiaowei; Yan, Xiaozhen; Chen, Yangmei; Song, Bo

2017-09-01

The synthesis of hydrogen sulfides, with the potential of high-temperature superconductivity, was recently proposed at high Tc = 203 K. It motivated us to employ an ab initio approach for the predictions of crystal structures to find the stable scandium hydrides. In addition to the earlier predicted three stoichiometries of ScH, ScH2, and ScH3, we identify three other metallic stoichiometries of ScH4, ScH6, and ScH8, which show superconductivity at significantly higher temperatures. The phases of ScH4 and ScH6, whose stability does not require extremely high pressures (ZPE), are primarily ionic compounds containing exotic quasimolecular H2 arrangements. The present electron-phonon calculations revealed the superconductive potential of ScH4 and ScH6 with estimated Tc of 98 K and 129 K at 200 GPa and 130 GPa, respectively. The superconductivity of ScHn stems from the large electron-phonon coupling associated with the wagging, bending, and intermediate-frequency modes attributed mainly to the hydrogen atoms.

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.

The pressure dependence of structural, electronic, mechanical, vibrational, and thermodynamic properties of palladium-based Heusler alloys

Energy Technology Data Exchange (ETDEWEB)

Coban, Cansu [Balikesir Univ. (Turkey). Dept. of Physics

2017-07-01

The pressure dependent behaviour of the structural, electronic, mechanical, vibrational, and thermodynamic properties of Pd{sub 2}TiX (X=Ga, In) Heusler alloys was investigated by ab initio calculations. The lattice constant, the bulk modulus and its first pressure derivative, the electronic band structure and the density of states (DOS), mechanical properties such as elastic constants, anisotropy factor, Young's modulus, etc., the phonon dispersion curves and phonon DOS, entropy, heat capacity, and free energy were obtained under pressure. It was determined that the calculated lattice parameters are in good agreement with the literature, the elastic constants obey the stability criterion, and the phonon dispersion curves have no negative frequency which shows that the compounds are stable. The band structures at 0, 50, and 70 GPa showed valence instability at the L point which explains the superconductivity in Pd{sub 2}TiX (X=Ga, In).

Prediction of superconducting ternary hydride MgGeH6: from divergent high-pressure formation routes.

Science.gov (United States)

Ma, Yanbin; Duan, Defang; Shao, Ziji; Li, Da; Wang, Liyuan; Yu, Hongyu; Tian, Fubo; Xie, Hui; Liu, Bingbing; Cui, Tian

2017-10-18

Invigorated by the high temperature superconductivity in some binary hydrogen-dominated compounds, we systematically explored high-pressure phase diagrams and superconductivity of a ternary Mg-Ge-H system using ab initio methods. Stoichiometric MgGeH 6 with high hydrogen content exhibiting Pm3[combining macron] symmetry was predicted from a series of high-pressure synthesis paths. We performed an in-depth study on three distinct formation routes to MgGeH 6 , i.e., Mg + Ge + 3H 2 → MgGeH 6 , MgGe + 3H 2 → MgGeH 6 and MgH 2 + GeH 4 → MgGeH 6 at high pressures. By directly squeezing three elemental solids Mg + Ge + 3H 2 , we obtained ternary MgGeH 6 at 200 GPa. By adding a little bit of the MgGe alloy into hydrogen, we found that MgGeH 6 can form and stabilize at about 200 GPa. More intriguingly, upon compressing MgH 2 and GeH 4 to 250 GPa, we also predicted the same MgGeH 6 . Electron structure calculations reveal that the cubic MgGeH 6 is a good metal and takes on ionic character. Electron-phonon coupling calculation reveals a large λ = 1.16 for MgGeH 6 at 200 GPa. In particular, we found that ternary MgGeH 6 could be a potential high temperature superconductor with a superconducting transition temperature T c of ∼67 K at 200 GPa.

Electronic, phonon and superconducting properties of LaPtBi half-Heusler compound

Science.gov (United States)

Shrivastava, Deepika; Sanyal, Sankar P.

2018-05-01

In the framework of density functional theory based on plane wave pseudopotential method and linear response technique, we have studied the electronic, phonon and superconducting properties of LaPtBi half-Heusler compound. The electronic band structure and density of states show that it is gapless semiconductor which is consistent with previous results. The positive phonon frequencies confirm the stability of this compound in cubic MgAgAs phase. Superconductivity is studied in terms of Eliashberg spectral function (α2F(ω)), electron-phonon coupling constants (λ). The value of electron-phonon coupling parameter is found to be 0.41 and the superconducting transition temperature is calculated to be 0.76 K, in excellent agreement with the experimentally reported values.

Structural and electronic properties of superconductor MgB sub 2 under high pressure

CERN Document Server

Tang, J; Gu, H W; Matsushita, A; Takano, Y; Togano, K; Kito, H; Ihara, H

2002-01-01

The superconductivity and the lattice properties of a sintered MgB sub 2 material have been investigated under high pressure up to 10 GPa. The transition temperature was found to decrease linearly with increasing hydrostatic pressure at a rate of 1.03 K GPa sup - sup 1 , which can be explained with the classical Bardeen-Cooper-Shrieffer theory based on an electron-phonon coupling mechanism. The crystal lattice exhibits an anisotropic compressibility characterized by a larger compressibility along the c-direction than the a/b-directions. The anisotropy is attributed to a weaker inter-plane bonding along the c-axis in comparison with a stronger intra-plane bonding perpendicular to the c-axis. The bulk modulus of the measured material was deduced to be 172 GPa.

Anomalous He-gas high-pressure studies on superconducting LaO1-xFxFeAs

International Nuclear Information System (INIS)

Bi, W; Banks, H B; Schilling, J S; Takahashi, H; Okada, H; Kamihara, Y; Hirano, M; Hosono, H

2010-01-01

Ac susceptibility measurements have been carried out on superconducting LaO 1-x F x FeAs for x=0.07 and 0.14 under He-gas pressures to ∼0.8 GPa. Not only do the measured values of dT c /dP differ substantially from those obtained in previous studies using other pressure media, but also the T c (P) dependences observed depend on the detailed pressure/temperature history of the sample. A sizeable sensitivity of T c (P) to shear stresses provides a possible explanation.

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.

ac superconducting articles

International Nuclear Information System (INIS)

Meyerhoff, R.W.

1977-01-01

A noval ac superconducting cable is described. It consists of a composite structure having a superconducting surface along with a high thermally conductive material wherein the superconducting surface has the desired physical properties, geometrical shape and surface finish produced by the steps of depositing a superconducting layer upon a substrate having a predetermined surface finish and shape which conforms to that of the desired superconducting article, depositing a supporting layer of material on the superconducting layer and removing the substrate, the surface of the superconductor being a replica of the substrate surface

Superconducting properties of modified YBa2Cu3O7-δ ceramics

International Nuclear Information System (INIS)

Kaleva, G.M.; Politova, E.D.; Kudinova, M.V.; Prutchenko, S.G.; Venevtsev, Yu.N.

1993-01-01

In connection with the promising practical applications of high temperature superconductors (HTSC) particular attention has been paid to studying the influence of dopant elements on the properties of HTSC ceramics. According to earlier work, replacement of the yttrium in the compound YBa 2 Cu 3 O 7-8 (1-2-3) by rare earth elements, excluding Ce, Pr, Tb, and Pm, has almost no influence on the superconducting transition temperature (T c ∼ 90 K). Of the alkaline metals, only Sr will displace Ba over a wide range of concentrations (up to 50 at %), but in this case T c is reduced to 86 K. The strongest influence on the superconducting properties results from replacement of copper by 3d transition metals. Introduction of 10 at.% Zn, Co, Fe, Ni, Ti, Mn, or Cr in place of the copper leads to a drastic lowering of T c . At the same time it has been reported that microadditions of individual elements (replacement of Cu by Pd, Ti, and Fe, at a level of 0.1-0.5 at.%,) may elevate conducting phase and improve the contacts between grains, so that, in particular, there is an increase in the critical current density. In view of the possible positive influence which introduction of small quantities of individual elements may have 1-2-3 compounds, in the present work, the authors have studied the action of dopant additions, including complex ones, on this phase, with the goal of improving its superconducting properties. Structural and superconducting properties were studied for samples of YBa 2 (Cu 1- x M x ) 3 O 7-δ , with M = Sb (I), Mn (II), and Sb 1/2 Mn 1/2 (III), and (1-x)Y 1/3 Ba 2/3 CuO 3-δ ·xSr(Sb 1/2 Mn 1/2 )O 3 (IV), using x-ray diffraction, electron microscopy, Mossbauer spectroscopy, as well as changes in the temperature dependence of the resistivity ρ(T)

Calculated Fermi surface properties of LaSn3 and YSn3 under pressure

International Nuclear Information System (INIS)

Kanchana, V.

2012-01-01

The electronic structure, Fermi surface and elastic properties of the iso-structural and iso-electronic LaSn 3 and YSn 3 intermetallic compounds are studied under pressure within the frame work of density functional theory including spin-orbit coupling. The LaSn 3 Fermi surface consists of two sheets, of which the second is very complex. Under pressure a third sheet appears around compression V/V 0 =0.94, while a small topology changes in the second sheet is seen at compression V/V 0 =0.90. This may be in accordance with the anomalous behavior in the superconducting transition temperature observed in LaSn 3 , which has been suggested to reflect a Fermi surface topological transition, along with a non-monotonic pressure dependence of the density of states at the Fermi level. The similar behavior is not observed in YSn 3 for which the Fermi surface includes three sheets already at ambient conditions, and the topology remains unchanged under pressure. The reason for the difference in behavior between LaSn 3 and YSn 3 is the role of spin-orbit coupling and the hybridization of La-4f state with the Sn-p state in the vicinity of the Fermi level, which is well explained using the band structure calculation. The elastic constants and related mechanical properties are calculated at ambient as well as at elevated pressures. The elastic constants increase with pressure for both compounds and satisfy the conditions for mechanical stability under pressure. (author)

High pressure effect for high-Tc superconductors

International Nuclear Information System (INIS)

Takahashi, Hiroki; Tomita, Takahiro

2011-01-01

A number of experimental and theoretical studies have been performed to understand the mechanism of high-T c superconductivity and to enhance T c . High-pressure techniques have played a very important role for these studies. In this paper, the high-pressure techniques and physical properties of high-T c superconductor under high pressure are presented. (author)

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.

Superconductivity and electron microscopy

International Nuclear Information System (INIS)

Hawkes, P.W.; Valdre, U.

1977-01-01

In this review article, two aspects of the role of superconductivity in electron microscopy are examined: (i) the development of superconducting devices (mainly lenses) and their incorporation in electron microscopes; (ii) the development of electron microscope techniques for studying fundamental and technological problems associated with superconductivity. The first part opens with a brief account of the relevant properties of conventional lenses, after which the various types of superconducting lenses are described and their properties compared. The relative merits and inconveniences of superconducting and conventional lenses are examined, particular attention being paid to the spherical and chromatic aberration coefficients at accelerating voltages above a megavolt. This part closes with a survey of the various microscope designs that have been built or proposed, incorporating superconducting components. In the second part, some methods that have been or might be used in the study of superconductivity in the electron microscope are described. A brief account of the types of application for which they are suitable is given. (author)

UPt3, heavy fermions and superconductivity

International Nuclear Information System (INIS)

Visser, A. de.

1986-01-01

In this thesis an experimental study is presented of one of the heavy-fermion superconductors: UPt 3 (T c =0.5 K). The normal-state properties of this material are governed by pronounced spin-fluctuation effects. The unusual coexistence of spin-fluctuations and superconductivity is strongly suggestive for an unconventional type of superconductivity, mediated by spin-fluctuations instead of phonons, with the condensate formed out of odd-parity electron states. In the first chapter a general introduction is given to the field of the heavy-fermions. In the second chapter a theoretical background for the properties of UPt 3 is presented. Chapter 3 deals with the sample preparation and measuring techniques. In chapter 4 a series of experiments is presented on the normal-phase of UPt 3 , among which are studies of the specific heat, thermal expansion, sound velocity, magnetization, electrical resistivity, magnetoresistivity and magnetostriction. Also the influence of high-magnetic fields (35 T) and high-pressures (5 kbar) has been studied. The superconducting phase of UPt 3 has been discussed in chapter 5. In chapter 6 a series of pseudobinary U(Pt 1-x Pd x ) 3 compounds (x≤0.30) are studied. In the last chapter some final remarks and conclusions are presented. (Auth.)

Unconventional superconductivity in heavy-fermion compounds

Energy Technology Data Exchange (ETDEWEB)

White, B.D. [Department of Physics, University of California, San Diego, La Jolla, CA 92093 (United States); Center for Advanced Nanoscience, University of California, San Diego, La Jolla, CA 92093 (United States); Thompson, J.D. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Maple, M.B., E-mail: mbmaple@ucsd.edu [Department of Physics, University of California, San Diego, La Jolla, CA 92093 (United States); Center for Advanced Nanoscience, University of California, San Diego, La Jolla, CA 92093 (United States)

2015-07-15

Highlights: • Quasiparticles in heavy-fermion compounds are much heavier than free electrons. • Superconductivity involves pairing of these massive quasiparticles. • Quasiparticle pairing mediated by magnetic or quadrupolar fluctuations. • We review the properties of superconductivity in heavy-fermion compounds. - Abstract: Over the past 35 years, research on unconventional superconductivity in heavy-fermion systems has evolved from the surprising observations of unprecedented superconducting properties in compounds that convention dictated should not superconduct at all to performing explorations of rich phase spaces in which the delicate interplay between competing ground states appears to support emergent superconducting states. In this article, we review the current understanding of superconductivity in heavy-fermion compounds and identify a set of characteristics that is common to their unconventional superconducting states. These core properties are compared with those of other classes of unconventional superconductors such as the cuprates and iron-based superconductors. We conclude by speculating on the prospects for future research in this field and how new advances might contribute towards resolving the long-standing mystery of how unconventional superconductivity works.

Superconductivity induced by extremely high pressures in organic Mott-insulator β'-(BEDT-TTF)2IBrCl

International Nuclear Information System (INIS)

Kano, M; Uchiyama, K; Taniguchi, H; Hedo, M; Matsubayashi, K; Uwatoko, Y

2009-01-01

Previous research revealed that, at a pressure of 8.2 GPa, β'-(BEDT-TTF)2ICl2 possesses the highest transition temperature (T C ) among the organic conductors[1]. In the present work, transport studies under extremely high pressure of up to 10.0 GPa, using a cubic anvil press are reported for a related material, β'-(BEDT-TTF)2IBrCl which is an organic Mott-insulator in ambient pressure. Superconductivity with the highest T c (8.5 K, onset) was observed at P = 8.6 GPa.

Collective-pinning properties of superconducting a-NbxGe and a-MoxSi films

International Nuclear Information System (INIS)

Woerdenweber, R.

1987-01-01

This thesis describes a study of superconducting flux pinning in amorphous NbGe and MoSi films of various compositions and thickness. Amorphous NbGe and MoSi alloys belong to the weak-coupling type-II superconductors in the extreme dirty limit. This feature enables to determine several important superconducting parameters from well-known theoretical expressions. It is also responsible for the weak pinning, which is necessary to observe the two-dimensional collective pinning properties according to the Larkin-Ovchinnikov theory. (Auth.)

Fabrication of Y-Ba-Cu-O (123) cuprate superconducting system and study of their electrical and structural properties

International Nuclear Information System (INIS)

Ahmed, F.; Hossain, M.K.; Sultana, H.R.; Abdul Hossain, M.; Khan, A.H.

2005-08-01

We know that in the YBa 2 Cu 3 O 6+x superconducting system transition temperature T c is highly dependent on the oxygen content in the compound. So, in order to fabricate superconducting YBa 2 Cu 3 O 6+x material under oxygen flow we have fabricated a tube furnace. Superconducting YBa 2 Cu 3 O 7-δ compounds were synthesized by the solid state reaction method. Different pressure for the pellet formation, different sintering and annealing conditions in air or in oxygen atmosphere were carried out to study the effect on the formation of superconducting phase. Samples were characterized by dc electrical resistance and X-ray diffraction. Superconducting Y 1-x Ca x Ba 2 Cu 3 O 7-δ compounds are now under investigation. (author)

Pressure effect on crystal structure and superconductivity of La0.8Th0.2FeAsO

International Nuclear Information System (INIS)

Kumar, Ravhi S.; Antonio, Daniel; Cornelius, Andrew L.; Zhao, Yusheng; Kanagaraj, M.; Arumugam, S.; Sinogeikin, Stanislav; Prakash, J.; Thakur, Gohil S.; Ganguli, A.K.; Hartmann, Thomas

2011-01-01

We have studied the effect of pressure on the superconducting transition temperature (T c ) of thorium doped La 1-x Th x FeAsO (x = 0.2) superconductor under hydrostatic pressures up to 1.6 GPa by resistivity and magnetization experiments. Application of pressure increases the T c to 31 K with a positive pressure coefficient of ∝1 K/GPa. Low temperature X-ray diffraction studies performed at 7.8 K at high pressures show no pressure induced structural changes and the tetragonal P4/nmm structure is found to persist up to 31 GPa. (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Ab initio study of properties of BaBiO3 at high pressure

Science.gov (United States)

Martoňák, Roman; Ceresoli, Davide; Kagayama, Tomoko; Tosatti, Erio

BaBiO3 is a mixed-valence perovskite which escapes metallic state by creating a Bi-O bond disproportionation or CDW pattern, resulting in a Peierls semiconductor with gap of nearly 1 eV at zero pressure. Evolution of structural and electronic properties at high pressure is, however, largely unknown. Pressure, it might be natural to expect, could reduce the bond-disproportionation and bring the system closer to metalicity or even superconductivity. We address this question by ab initio DFT methods based on GGA and hybrid functionals in combination with crystal structure prediction techniques based on genetic algorithms. We analyze the pressure evolution of bond disproportionation as well as other order parameters related to octahedra rotation for various phases in connection with corresponding evolution of the electronic structure. Results indicate that BaBiO3 continues to resist metalization also under pressure, through structural phase transitions which sustain and in fact increase the diversity of length of Bi-O bonds for neighboring Bi ions, in agreement with preliminary high pressure resistivity data. R.M. Slovak Research and Development Agency Contract APVV-15-0496, VEGA project No. 1-0904-15; E.T. ERC MODPHYSFRICT Advanced Grant No. 320796.

High-frequency properties of superconducting Y-Ba-Cu-oxide thin films

International Nuclear Information System (INIS)

Ramakrishnan, E.S.; Su, M.; Howng, W.

1992-01-01

rf and microwave properties of superconducting YBa 2 Cu 3 O 7-x thin films were measured and analyzed using a coplanar resonator structure. The films were developed by sequential electron-beam evaporation of the metals followed by postanneal processing. dc properties of the films were obtained from resistance-temperature and current-voltage measurements to evaluate the transition temperature and current densities. High-frequency properties were measured from 70 to 10 K and in the frequency range 1--3 GHz to determine the film characteristics as compared to pure copper films on the same substrates

Single Crystal Growth and Superconducting Properties of Antimony-Substituted NdO0.7F0.3BiS2

Directory of Open Access Journals (Sweden)

Satoshi Demura

2017-12-01

Full Text Available Antimony (Sb substitution of less than 8% was examined on a single crystal of a layered superconductor NdO0.7F0.3BiS2. The superconducting transition temperature of the substituted samples decreased as Sb concentration increased. A lattice constant along the c-axis showed a large decrease compared with that along the a-axis. Since in-plane chemical pressure monotonically decreased as Sb concentration increased, the suppression of the superconductivity is attributed to the decrease in the in-plane chemical pressure.

Organic superconductivity

International Nuclear Information System (INIS)

Jerome, D.

1980-01-01

We present the experimental evidences for the existence of a superconducting state in the Quasi One Dimensional organic conductor (TMTSF) 2 PF 6 . Superconductivity occuring at 1 K under 12 kbar is characterized by a zero resistance diamagnetic state. The anistropy of the upper critical field of this type II superconductor is consistent with the band structure anistropy. We present evidences for the existence of large superconducting precursor effects giving rise to a dominant paraconductive contribution below 40 K. We also discuss the anomalously large pressure dependence of T sb(s), which drops to 0.19 K under 24 kbar in terms of the current theories. (author)

Controllable manipulation of superconductivity using magnetic vortices

International Nuclear Information System (INIS)

Villegas, J E; Schuller, Ivan K

2011-01-01

The magneto-transport of a superconducting/ferromagnetic hybrid structure, consisting of a superconducting thin film in contact with an array of magnetic nanodots in the so-called 'magnetic vortex state', exhibits interesting properties. For certain magnetic states, the stray magnetic field from the vortex array is intense enough to drive the superconducting film into the normal state. In this fashion, the normal-to-superconducting phase transition can be controlled by the magnetic history. The strong coupling between superconducting and magnetic subsystems allows characteristically ferromagnetic properties, such as hysteresis and remanence, to be dramatically transferred into the transport properties of the superconductor.

Interplay between superconductivity and magnetism in organic conductors κ-(BEDT-TTF)2X

International Nuclear Information System (INIS)

Benali, A.; Bennaceur, R.

2008-01-01

We study within a mean field theory the interplay between superconductivity and antiferromagnetism in κ-(ET) 2 X. These compounds are described by a two-band model. When we apply pressure in these compounds, we modify the Fermi surface shape and consequently the nesting property. We compare the pressure effects in experiments and nesting property according to our calculations. Our theoretical description seems to explain various experimental data, for which, as far as we know, no clear theoretical interpretation has been given so far

Superconductive properties, interaction mechanisms, materials preparation and electronic transport in high-Tc superconductors

International Nuclear Information System (INIS)

Saemann-Ischenko, G.

1993-01-01

The final report is composed of eight chapters dealing with the following aspects: I. Mixed state, critical currents, anisotropy, intrinsic and extrinsic pinning. II. Microwave properties and far-infrared reflectivity of epitactic HTSC films. III. Hall effect at the states of normal conductivity and superconductivity, magnetoresistance, superconducting fluctuation phenomena. IV. Effects of the nuclear and the electronic energy loss. V. Scanning electron microscopy. VI. p- and n-doped high-Tc superconductors: Charge symmetry and magnetism. VII. Preparation methods. VIII. Electrochemical examinations of HTSC films and HTSC monocrystals at low temperatures. (orig./MM) [de

Origin of superconductivity in KFe2As2 under positive and negative pressures and relation to other Fe-based families

Science.gov (United States)

Valenti, Roser

KFe2As2 shows an intricate behavior as a function of pressure. At ambient pressure the system is superconductor with a low critical temperature Tc=3.4 K and follows a V-shaped pressure dependence of Tc for moderate pressures with a local minimum at a pressure of 1.5 GPa. Under high pressures Pc=15 GPa, KFe2As2 exhibits a structural phase transition from a tetragonal to a collapsed tetragonal phase accompanied by a boost of the superconducting critical temperature up to 12 K. On the other hand, negative pressures realized through substitution of K by Cs or Rb decrease Tc down to 2.25K. In this talk we will discuss recent progress on the understanding of the microscopic origin of this pressure-dependent behavior by considering a combination of ab initio density functional theory with dynamical mean field theory and spin fluctuation theory calculations. We will argue that a Lifshitz transition associated with the structural collapse changes the pairing symmetry from d-wave (tetragonal) to s+/- (collapsed tetragonal) at high pressures while at ambient and negative pressures correlation effects appear to be detrimental for superconductivity. Further, we shall establish cross-links to the chalcogenide family, in particular FeSe under pressure. The Deutsche Forschungsgemeinschaft (DFG) is gratefully acknowledged for financial support.

Study of superconducting magnetic bearing applicable to the flywheel energy storage system that consist of HTS-bulks and superconducting-coils

International Nuclear Information System (INIS)

Seino, Hiroshi; Nagashima, Ken; Tanaka, Yoshichika; Nakauchi, Masahiko

2010-01-01

The Railway Technical Research Institute conducted a study to develop a superconducting magnetic bearing applicable to the flywheel energy-storage system for railways. In the first step of the study, the thrust rolling bearing was selected for application, and adopted liquid-nitrogen-cooled HTS-bulk as a rotor, and adopted superconducting coil as a stator for the superconducting magnetic bearing. Load capacity of superconducting magnetic bearing was verified up to 10 kN in the static load test. After that, rotation test of that approximately 5 kN thrust load added was performed with maximum rotation of 3000rpm. In the results of bearing rotation test, it was confirmed that position in levitation is able to maintain with stability during the rotation. Heat transfer properties by radiation in vacuum and conductivity by tenuous gas were basically studied by experiment by the reason of confirmation of rotor cooling method. The experimental result demonstrates that the optimal gas pressure is able to obtain without generating windage drag. In the second stage of the development, thrust load capacity of the bearing will be improved aiming at the achievement of the energy capacity of a practical scale. In the static load test of the new superconducting magnetic bearing, stable 20kN-levitation force was obtained.

Effect of point disorder on superconducting properties of ultrathin epitaxial NbN films

International Nuclear Information System (INIS)

Jesudasan, John; Bagwe, Vivas; Mondal, Mintu; Chand, Madhavi; Kamlapure, Anand; Pai, S.P.; Raychaudhuri, Pratap; Mishra, Archana

2009-01-01

We synthesized homogeneously disordered epitaxial NbN films on MgO(100) substrates using reactive dc magnetron sputtering. The disorder of the films is characterized by the Loffe-Regel parameter k F I. The superconducting properties are studied through transport, ac-susceptibility measurements and electron tunneling. The superconducting transition temperature is studied as a function of thickness for films of different disorder. In the case of the less disordered film, there is a smooth decrease in T c with decreasing thickness but for the more disordered film, the T c shows a sharp decrease to zero at a threshold thickness. The superconducting energy gap is studied via planar tunnel junctions. It is found that for the less disordered films, the temperature dependence of the gap follows the BCS variation but for the more disordered ones, there is a significant deviation from the BCS curve, and the gap remains finite at T c indicating that the superconducting transition is either governed by phase fluctuations or a first order phase transition. (author)

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

International Nuclear Information System (INIS)

Lisboa-Filho, P N; Deimling, C V; Ortiz, W A

2010-01-01

In this contribution superconducting specimens of YBa 2 Cu 3 O 7-δ 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.

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.

Pressure rise analysis in superconducting coils during dumping

International Nuclear Information System (INIS)

Tada, E.; Shimamoto, S.

1984-01-01

This chapter describes the ALPHE computer code, whose purpose is to calculate transient helium behavior in a poolboiling coil and to determine suitable characteristics of safety devices to minimize the maximum pressure and the liquid helium lost during dumping due to quench, or when discharging without normalcy. The analysis is compared with the measurements obtained in the domestic test of the Japanese LCT coil. Topics considered include basic equations (helium behavior, heat generation), manual dump without quench, and dumping due to quench. It is demonstrated that the transient behavior, calculated by ALPHE assuming quasi-static equilibrium between helium and coil, is in good agreement with the experimental measurements observed in the domestic test of the Japanese LCT coil. The engineering technique required for the design criteria of superconducting coils and safety device during dumping is established. ALPHE can be used to design an emergency safety system for a helium refrigerator during dumping

High-pressure studies of superconductivity in BiO0. 75F0. 25BiS2

Indian Academy of Sciences (India)

Home; Journals; Bulletin of Materials Science; Volume 40; Issue 6. High-pressure studies of superconductivity in BiO 0.75 F 0.25 BiS 2. ZEBA HAQUE GOHIL S THAKUR GANESAN KALAI SELVAN SONACHALAM ARUMUGAM L C GUPTA A K GANGULI. Volume 40 Issue 6 October 2017 pp 1121-1125 ...

Electronic structure and superconductivity of divalent metals under very high pressure

International Nuclear Information System (INIS)

Bireckoven, B.

1987-05-01

A single crystal, high-pressure diamond cell has been developed for the study of superconductors under pressures to over 50 GPa. A high sensitivity AC-SQUID magnetometer has been employed to detect the diamagnetic response of the very small samples at T C . The T C (p)-dependence of the lead-manometer has been calibrated against the ruby-pressure-scale up to pressures of 30 GPa. In spite of the well-known fcc/hcp-transition at 13 GPa lead shows a smooth T C (p)-behaviour and thus is a very suitable manometer. Band structure calculations for the alkaline earth metals indicate an appreciable s-to-d transfer with increasing pressure. In fact, superconductivity was previously observed in the pressure induced d-transition metals Sr and Ba (however not yet in Ca). For the first time the author presents a quantitative investigation of T C as a function of p up to 50 GPa. Both elements turn out to be ''good'' superconductors featuring T C 's of about 7 K. The possibility of a generalized phase diagram for the alkaline earth metals will be critically discussed. At any rate, the occurrence of such high T C 's is rather strong evidence for a substantial d-transition metal character at high p. Investigations of very dilute BaEu-alloys up to 45 GPa reveal a strong monotonic increase of ΔT C = T C Ba -T C BaEu . (orig./GSCH)

Cryostat for TRISTAN superconducting cavity

International Nuclear Information System (INIS)

Mitsunobu, S.; Furuya, T.; Hara, K.

1990-01-01

Superconducting cavities generate rather high heat load of hundreds watts in one cryostat and have high sensitivity for pressure. We adopted usual pool-boiling type cooling for its stable pressure operation. Two 5-cell Nb cavities were installed in one flange type cryostat. Tuning mechanics actuated by a pulse-motor and a Piezo-electric element are set at outside of vacuum end flange. The design and performance of the cryostat for TRISTAN superconducting cavities are described. (author)

The reexamination of thermal expansion of ferromagnetic superconductors and the pressure differential of its superconducting transition temperature-possible application to UGe2

International Nuclear Information System (INIS)

Konno, Rikio; Hatayama, Nobukuni

2011-01-01

The temperature dependence of thermal expansion of ferromagnetic superconductors below the superconducting transition temperature T scu of a majority spin conduction band is reexamined. In the previous study [to be published in J. M. Phys. B] the volume differential of the kinetic energy of conduction electrons is constant. However, in this study the volume differential of the kinetic energy of conduction electrons is inconstant. The superconducting gap of the majority spin conduction band used in this study has a line node. It is appropriate to UGe 2 . The pressure differential of its superconducting transition temperature is also investigated. We find that the thermal expansion coefficient has the divergence at the superconducting transition temperature. The thermodynamic Grueneisen's relation is satisfied.

Pressure and high-Tc superconductivity in sulfur hydrides.

Science.gov (United States)

Gor'kov, Lev P; Kresin, Vladimir Z

2016-05-11

The paper discusses fundamentals of record-TC superconductivity discovered under high pressure in sulfur hydride. The rapid increase of TC with pressure in the vicinity of Pcr ≈ 123GPa is interpreted as the fingerprint of a first-order structural transition. Based on the cubic symmetry of the high-TC phase, it is argued that the lower-TC phase has a different periodicity, possibly related to an instability with a commensurate structural vector. In addition to the acoustic branches, the phonon spectrum of H3S contains hydrogen modes with much higher frequencies. Because of the complex spectrum, usual methods of calculating TC are here inapplicable. A modified approach is formulated and shown to provide realistic values for TC and to determine the relative contributions of optical and acoustic branches. The isotope effect (change of TC upon Deuterium for Hydrogen substitution) originates from high frequency phonons and differs in the two phases. The decrease of TC following its maximum in the high-TC phase is a sign of intermixing with pairing at hole-like pockets which arise in the energy spectrum of the cubic phase at the structural transition. On-pockets pairing leads to the appearance of a second gap and is remarkable for its non-adiabatic regime: hydrogen mode frequencies are comparable to the Fermi energy.

Nematicity, magnetism and superconductivity in FeSe.

Science.gov (United States)

Böhmer, Anna E; Kreisel, Andreas

2018-01-17

Iron-based superconductors are well known for their complex interplay between structure, magnetism and superconductivity. FeSe offers a particularly fascinating example. This material has been intensely discussed because of its extended nematic phase, whose relationship with magnetism is not obvious. Superconductivity in FeSe is highly tunable, with the superconducting transition temperature, T c , ranging from 8 K in bulk single crystals at ambient pressure to almost 40 K under pressure or in intercalated systems, and to even higher temperatures in thin films. In this topical review, we present an overview of nematicity, magnetism and superconductivity, and discuss the interplay of these phases in FeSe. We focus on bulk FeSe and the effects of physical pressure and chemical substitutions as tuning parameters. The experimental results are discussed in the context of the well-studied iron-pnictide superconductors and interpretations from theoretical approaches are presented.

Field-induced magnetic instability within a superconducting condensate

DEFF Research Database (Denmark)

Mazzone, Daniel Gabriel; Raymond, Stephane; Gavilano, Jorge Luis

2017-01-01

The application of magnetic fields, chemical substitution, or hydrostatic pressure to strongly correlated electron materials can stabilize electronic phases with different organizational principles. We present evidence for a fieldinduced quantum phase transition, in superconducting Nd0.05Ce0.95Co...... that the magnetic instability is not magnetically driven, and we propose that it is driven by a modification of superconducting condensate at H*.......In5, that separates two antiferromagnetic phases with identical magnetic symmetry. At zero field, we find a spin-density wave that is suppressed at the critical field mu H-0* = 8 T. For H > H*, a spin-density phase emerges and shares many properties with the Q phase in CeCoIn5. These results suggest...

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......We have examined the potential of 10 MW superconducting direct drive generators to enter the European offshore wind power market and estimated that the production of about 1200 superconducting turbines until 2030 would correspond to 10% of the EU offshore market. The expected properties of future...... 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...

Superconducting properties of Zr1+xNi2-xGa and Zr1-xNi2+xGa Heusler compounds

Directory of Open Access Journals (Sweden)

Saad Alzahrani

2017-05-01

Full Text Available The superconducting properties of a series of Zr1+xNi2-xGa and Zr1-xNi2+xGa compounds have been investigated by x-ray diffraction, electrical resistivity, dc magnetization, and ac susceptibility measurements. While the parent compound, ZrNi2Ga, exhibited the cubic L21 Heusler structure, multiple non-cubic structures formed in the Zr and Ni rich doped materials. For x ≤ 0.3, all Zr1-xNi2+xGa compounds demonstrated superconducting behavior, but no superconductivity was observed in the Zr1+xNi2-xGa alloys for x > 0.2. The magnetization data revealed that all materials in both Zr1+xNi2-xGa and Zr1-xNi2+xGa series exhibited type-II superconductivity. With increasing doping concentration x, the paramagnetic ordering were enhanced in both systems while the superconducting properties were found to weaken. The observations are discussed considering the structural disorders in the systems.

Electronic properties of γ-U and superconductivity of U–Mo alloys

International Nuclear Information System (INIS)

Tkach, I.; Kim-Ngan, N.-T.H.; Warren, A.; Scott, T.; Gonçalves, A.P.; Havela, L.

2014-01-01

Highlights: • The bcc phase of uranium was stabilized to low temperature in U–Mo alloys. • Ultrafast cooling was utilized. • Negative coefficient dρ/dT indicates very strong disorder. • The alloys are superconducting with T c ≈ 2.1 K. • They exhibit high critical field exceeding 5 T. - Abstract: Fundamental electronic properties of γ-Uranium were determined using Mo doping combined with ultrafast (splat) cooling, which allowed stabilization of the bcc structure to low temperatures. The Sommerfeld coefficient γ e is enhanced to 16 mJ/mol K 2 from 11 mJ/mol K 2 for α-U. Magnetic susceptibility remains weak and T-independent, ≈5 × 10 −8 m 3 /mol. The Mo-doped γ-U exhibits a conventional BCS superconductivity with T c ≈ 2.1 K and critical field exceeding 5 T for 15 at.% Mo. This type of superconductivity is qualitatively different from the one found for pure U splat, which has T c higher than 1 K but the weak specific heat anomaly proves that it is not real bulk effect

The influence of chemical treatments on the superconducting properties of technical niobium materials and their effect on the performance of superconducting radio frequency cavities

International Nuclear Information System (INIS)

Roy, S B; Sahni, V C; Myneni, G R

2009-01-01

We present the results of a study of superconducting response in the niobium materials used in the fabrication of high accelerating gradient (>25 MV m -1 ) superconducting radio frequency (SC-RF) cavities. These results clearly show that the typical surface chemical treatment deployed during the fabrication of SC-RF cavities affects the superconducting properties of pure niobium materials. Such SC-RF cavities operating at 2 K are often found to show anomalous RF losses, causing either a strong degradation of the quality factor or a thermal breakdown for cavity magnetic fields between 1 and 1.5 kOe. The results of our study suggest a correlation between the field for the first flux-line penetration in these chemically treated technical niobium materials and the reported onset field of anomalous losses in the SC-RF cavities.

The influence of chemical treatments on the superconducting properties of technical niobium materials and their effect on the performance of superconducting radio frequency cavities

Science.gov (United States)

Roy, S. B.; Myneni, G. R.; Sahni, V. C.

2009-10-01

We present the results of a study of superconducting response in the niobium materials used in the fabrication of high accelerating gradient (>25 MV m-1) superconducting radio frequency (SC-RF) cavities. These results clearly show that the typical surface chemical treatment deployed during the fabrication of SC-RF cavities affects the superconducting properties of pure niobium materials. Such SC-RF cavities operating at 2 K are often found to show anomalous RF losses, causing either a strong degradation of the quality factor or a thermal breakdown for cavity magnetic fields between 1 and 1.5 kOe. The results of our study suggest a correlation between the field for the first flux-line penetration in these chemically treated technical niobium materials and the reported onset field of anomalous losses in the SC-RF cavities.

Transport and pairing properties of helical edges with proximity induced superconductivity and ferromagnetism

Energy Technology Data Exchange (ETDEWEB)

Keidel, Felix; Burset, Pablo; Trauzettel, Bjoern [Institute of Theoretical Physics and Astrophysics, University of Wuerzburg, 97074 Wuerzburg (Germany); Crepin, Francois [Laboratoire de Physique Theorique de la Matiere Condensee, UPMC, Sorbonne Universites, 75252 Paris (France)

2016-07-01

The scientific interest in Quantum Spin Hall systems is far from declining. While these certainly are fascinating by themselves, there is plenty of new and exciting physics to arise when superconductivity and ferromagnetism are brought into the game. The strong constraint of helicity in the edge states of a two-dimensional topological insulator is responsible for an intimate relation between the allowed scattering processes in a hybrid junction and the parameters of the system, namely the superconducting order parameter and the magnetic field. In our work, we study a helical liquid in proximity to a conventional s-wave superconductor and ferromagnetic insulators by means of a Green's function analysis. The ferromagnet gives rise to sub-gap Andreev/Majorana bound states and non-local crossed Andreev reflection (CAR), both of which decisively affect the pairing and transport properties of the junction. As a result, the simple s-wave symmetry of the superconductor is enriched and unconventional odd-frequency triplet superconductivity emerges. Strikingly, we have identified a setup that favors CAR over electron co-tunneling and may allow for the indirect measurement of the symmetries of the superconducting order parameter.

Superconductivity at the industrial scale

International Nuclear Information System (INIS)

Tixador, P.; Lebrun, Ph.

2011-01-01

The discovery of superconductivity is 100 years old but theoretical works are still necessary: the BCS theory does not apply to the new families of high temperature superconducting materials discovered after 1986. In 2001 it was discovered that MgB 2 is superconducting at 39 K, this critical temperature is not the highest but MgB 2 is easy to produce and cheap. Today's highest critical temperature under atmospheric pressure is that of the HgTlBaCaCuO compound: 138 K. The complexity and the cost of cryogenic systems restrain the applications of superconductivity. The author reviews the applications of superconducting in medical imaging, particle detectors, and in the safety systems of power networks. (A.C.)

Synthesis and study of the magnetic properties of thallium-based over-doped superconducting compounds

International Nuclear Information System (INIS)

Opagiste, C.

1994-07-01

The synthesis, structure and magnetic properties of the normal and superconducting states of over-doped Tl 2 Ba 2 Cu O 6±x and Tl 2 Ba 2 Ca Cu 2 O 8±x superconducting compounds, are presented. Synthesis under high pressure using Tl 2 Ba 2 O 5 as a precursor avoids thallium losses and Ba Cu O 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

Superconducting cable cooling system by helium gas at two pressures

International Nuclear Information System (INIS)

Dean, J.W.

1977-01-01

Thermally contacting, oppositely streaming, cryogenic fluid streams in the same enclosure in a closed cycle changes the fluid from a cool high pressure helium gas to a cooler reduced pressure helium gas in an expander so as to be at different temperature ranges and pressures respectively in go and return legs that are in thermal contact with each other and in thermal contact with a longitudinally extending superconducting transmission line enclosed in the same cable enclosure that insulates the line from the ambient at a temperature T 1 . By first circulating the fluid from a refrigerator at one end of the line as a cool gas at a temperature range T 2 to T 3 in the go leg, then circulating the gas through an expander at the other end of the line where the gas becomes a cooler gas at a reduced pressure and at a reduced temperature T 4 and finally by circulating the cooler gas back again to the refrigerator in a return leg at a temperature range T 4 to T 5 , while in thermal contact with the gas in the go leg, and in the same enclosure therewith for compression into a higher pressure gas at T 2 in a closed cycle, where T 2 greater than T 3 and T 5 greater than T 4 , the fluid leaves the enclosure in the go leg as a gas at its coldest point in the go leg, and the temperature distribution is such that the line temperature decreases along its length from the refrigerator due to the cooling from the gas in the return leg

Superconducting and Normal State Properties of OsB2*

Science.gov (United States)

Singh, Yogesh; Niazi, A.; Zong, X.; Suh, B. J.; Vannette, M. W.; Prozorov, R.; Johnston, D. C.

2007-03-01

OsB2 is a layered superhard metallic material that was found to superconduct below Tc= 2.1 K.^1 We report the first detailed measurements of the static and dynamic magnetic susceptibilities χ, electrical resistivity, heat capacity Cp, penetration depth, and ^11B NMR on OsB2 to characterize its superconducting and normal state properties. The results confirm that OsB2 is a bulk superconductor below Tc= 2.1 K@. Its properties can be described by a close to weak-coupling s-wave BCS model with an electron-phonon coupling constant λ= 0.4--0.5, δ(0)/(kBTc) 1.9, a small Ginzburg-Landau parameter κ of order 5 or less, and a small zero-temperature critical magnetic field of roughly 500 Oe. The ^11B NMR measurements in the normal state show a nuclear spin-lattice relaxation time T1= 2.1 s at room temperature and a Korringa law with T1T = 610 s.K at lower T, and a correspondingly small T-independent Knight shift. These results indicate a small s character of the conduction electron wave function at the B site at the Fermi level. Our results will be compared to corresponding data for MgB2.1. J. K. Vandenberg et al., Mater. Res. Bull. 10, 889 (1975).^*Supported by the USDOE under Contract No. W-7405-Eng-82. Permanent address: Dept. Phys., The Catholic Univ. Korea.

Analytical approximations for thermophysical properties of supercritical nitrogen (SCN) to be used in futuristic high temperature superconducting (HTS) cables

Energy Technology Data Exchange (ETDEWEB)

Dondapati, Raja Sekhar, E-mail: drsekhar@ieee.org [School of Mechanical Engineering, Lovely Professional University, Phagwara, Punjab 144401 (India); Ravula, Jeswanth [School of Mechanical Engineering, Lovely Professional University, Phagwara, Punjab 144401 (India); Thadela, S. [Department of Mechanical Engineering, Andhra University, Visakhapatnam, Andhra Pradesh (India); Usurumarti, Preeti Rao [Department of Mechanical Engineering, P.V.K. Institute of Technology, Anantapur, Andhra Pradesh (India)

2015-12-15

Future power transmission applications demand higher efficiency due to the limited resources of energy. In order to meet such demand, a novel method of transmission is being developed using High Temperature Superconducting (HTS) cables. However, these HTS cables need to be cooled below the critical temperature of superconductors used in constructing the cable to retain the superconductivity. With the advent of new superconductors whose critical temperatures having reached up to 134 K (Hg based), a need arises to find a suitable coolant which can accommodate the heating loads on the superconductors. The present work proposes, Supercritical Nitrogen (SCN) to be a feasible coolant to achieve the required cooling. Further, the feasibility of proposed coolant to be used in futuristic HTS cables is investigated by studying the thermophysical properties such as density, viscosity, specific heat and thermal conductivity with respect to temperature (T{sub C} + 10 K) and pressure (P{sub C} + 10 bar). In addition, few temperature dependent analytical functions are developed for thermophysical properties of SCN which are useful in predicting thermohydraulic performance (pressure drop, pumping power and cooling capacity) using numerical or computational techniques. Also, the developed analytical functions are used to calculate the pumping power and the temperature difference between inlet and outlet of HTS cable. These results are compared with those of liquid nitrogen (LN2) and found that the circulating pumping power required to pump SCN is significantly smaller than that to pump LN2. Further, it is found that the temperature difference between the inlet and outlet is smaller as compared to that when LN2 is used, SCN can be preferred to cool long length Hg based HTS cables. - Highlights: • Analytical functions are developed for thermophysical properties of Supercritical Nitrogen. • Error analysis shows extremely low errors in the developed analytical functions. �

Analytical approximations for thermophysical properties of supercritical nitrogen (SCN) to be used in futuristic high temperature superconducting (HTS) cables

International Nuclear Information System (INIS)

Dondapati, Raja Sekhar; Ravula, Jeswanth; Thadela, S.; Usurumarti, Preeti Rao

2015-01-01

Future power transmission applications demand higher efficiency due to the limited resources of energy. In order to meet such demand, a novel method of transmission is being developed using High Temperature Superconducting (HTS) cables. However, these HTS cables need to be cooled below the critical temperature of superconductors used in constructing the cable to retain the superconductivity. With the advent of new superconductors whose critical temperatures having reached up to 134 K (Hg based), a need arises to find a suitable coolant which can accommodate the heating loads on the superconductors. The present work proposes, Supercritical Nitrogen (SCN) to be a feasible coolant to achieve the required cooling. Further, the feasibility of proposed coolant to be used in futuristic HTS cables is investigated by studying the thermophysical properties such as density, viscosity, specific heat and thermal conductivity with respect to temperature (T_C + 10 K) and pressure (P_C + 10 bar). In addition, few temperature dependent analytical functions are developed for thermophysical properties of SCN which are useful in predicting thermohydraulic performance (pressure drop, pumping power and cooling capacity) using numerical or computational techniques. Also, the developed analytical functions are used to calculate the pumping power and the temperature difference between inlet and outlet of HTS cable. These results are compared with those of liquid nitrogen (LN2) and found that the circulating pumping power required to pump SCN is significantly smaller than that to pump LN2. Further, it is found that the temperature difference between the inlet and outlet is smaller as compared to that when LN2 is used, SCN can be preferred to cool long length Hg based HTS cables. - Highlights: • Analytical functions are developed for thermophysical properties of Supercritical Nitrogen. • Error analysis shows extremely low errors in the developed analytical functions. �

Structural phase transitions and superconductivity in lanthanum copper oxides

International Nuclear Information System (INIS)

Crawford, M.K.; Harlow, R.L.; McCarron, E.M.

1996-01-01

Despite the enormous effort expended over the past ten years to determine the mechanism underlying high temperature superconductivity in cuprates there is still no consensus on the physical origin of this fascinating phenomenon. This is a consequence of a number of factors, among which are the intrinsic difficulties in understanding the strong electron correlations in the copper oxides, determining the roles played by antiferromagnetic interactions and low dimensionality, analyzing the complex phonon dispersion relationships, and characterizing the phase diagrams which are functions of the physical parameters of temperature and pressure, as well as the chemical parameters of stoichiometry and hole concentration. In addition to all of these intrinsic difficulties, extrinsic materials issues such as sample quality and homogeneity present additional complications. Within the field of high temperature superconductivity there exists a subfield centered around the material originally reported to exhibit high temperature superconductivity by Bednorz and Mueller, Ba doped La 2 CuO 4 . This is structurally the simplest cuprate superconductor. The authors report on studies of phase differences observed between such base superconductors doped with Ba or Sr. What these studies have revealed is a fascinating interplay of structural, magnetic and superconducting properties which is unique in the field of high temperature superconductivity and is summarized in this paper

Magnetic and superconducting properties of Ir-doped EuFe2As2

International Nuclear Information System (INIS)

B Paramanik, U; Hossain, Z; L Paulose, P; Ramakrishnan, S; K Nigam, A; Geibel, C

2014-01-01

The magnetic and superconducting properties of 14% Ir-doped EuFe 2 As 2 are studied by means of dc and ac magnetic susceptibilities, electrical resistivity, specific heat and 151 Eu and 57 Fe Mössbauer spectroscopy (MS) measurements. Doping of Ir in EuFe 2 As 2 suppresses the Fe spin density wave transition and in turn gives rise to high temperature superconductivity below 22.5 K with a reentrant feature at lower temperature. Magnetization and 151 Eu Mössbauer data indicate that the Eu 2+ spins order magnetically below 18 K. 57 Fe MS studies show a line broadening in the absorption spectra below 18 K due to transferred hyperfine field from the magnetically ordered Eu sublattices. A pronounced λ-shape peak in the specific heat supports a second-order phase transition of Eu 2+ magnetic ordering with a strong ferromagnetic component, as confirmed by the magnetic field dependences of the transition. For a single crystal, the in-plane resistivity (ρ ab ) and out-of-plane susceptibility (χ c ) show superconducting transitions with zero resistance and diamagnetism, respectively. But the in-plane susceptibility (χ ab ) does not show any diamagnetic shielding against external fields. The observed non-zero resistance in the temperature range 10–17.5 K, below the superconducting transition temperature, suggests the possible existence of a spontaneous vortex state in this superconductor. (papers)

Moessbauer high pressure and magnetic field studies of the superconductor FeSe

Energy Technology Data Exchange (ETDEWEB)

Ksenofontov, Vadim; Felser, Claudia [Institute of Inorganic and Analytical Chemistry, Johannes Gutenberg - University, Mainz (Germany); Wortmann, Gerhard [Department of Physics, University of Paderborn, Paderborn (Germany); Trojan, Ivan; Palasyuk, Taras; Medvedev, Sergey; Eremets, Michail [Max-Planck-Institute for Chemistry, Mainz (Germany); McQueen, Tyrel M.; Cava, Richard J. [Department of Chemistry, Princeton University, Princeton (United States)

2010-07-01

Superconducting FeSe has been investigated by Moessbauer spectroscopy applying high pressure and strong external magnetic fields. It was found that pressure-induced structural phase transition between tetragonal and hexagonal modifications is accompanied by increased distortion of local surrounding of Fe atoms. Appearance of the hexagonal phase above 7.2 GPa is accompanied by degradation of superconducting properties of FeSe. Low-temperature measurements demonstrated that the ground states in both orthorhombic and hexagonal phases of FeSe are nonmagnetic. Moessbauer measurements in the external magnetic field below transition to the superconducting state revealed zero electron spin density on Fe atoms. Interpretation of Moessbauer spectra of FeSe in the Shubnikov phase is discussed.

Coexistence of magnetism and superconductivity in the hole doped FeAs-based superconducting compound

International Nuclear Information System (INIS)

Lu, T.P.; Wu, C.C.; Chou, W.H.; Lan, M.D.

2010-01-01

The magnetic and superconducting properties of the Sm-doped FeAs-based superconducting compound were investigated under wide ranges of temperature and magnetic field. After the systematical magnetic ion substitution, the superconducting transition temperature decreases with increasing magnetic moment. The hysteresis loop of the La 0.87-x Sm x Sr 0.13 FeAsO sample shows a superconducting hysteresis and a paramagnetic background signal. The paramagnetic signal is mainly attributed to the Sm moments. The experiment demonstrates that the coexistence of magnetism and superconductivity in the hole doped FeAs-based superconducting compounds is possible. Unlike the electron doped FeAs-based superconducting compounds SmFeAsOF, the hole doped superconductivity is degraded by the substitution of La by Sm. The hole-doped and electron-doped sides are not symmetric.

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.

Quenching effect on properties of Bi-Sr-Ca-Cu-O superconducting ceramics of various composition

International Nuclear Information System (INIS)

Amitin, E.B.; Gromilov, S.A.; Naumov, V.N.; Royak, A.Ya.; Starikov, M.A.

1989-01-01

Bismuth ceramics quenching effect on superconducting properties of samples of various composition is investigated. Two types of quenching effect on sample properties are detected: an increase of superconducting transition temperature T c by 15-20 K; broadening of temperature interval of the phase transition without anynatable T c displacement. X ray diffraction investigations have not detected sufficient differences in diffraction patterns of quenched and non-quenched samples. Within the limits of composition analysis by oxygen (±3%) no change of its content prior to and after quenching is detected. A correlation between the presence of an amorphous phase in a sample and the type of quenching effect is observed: T c increases in ceramics where an amorphous component is detected

Structure, magnetic and superconducting properties of MoSr2HoCu2O8-δ

International Nuclear Information System (INIS)

Balchev, N.; Nenkov, K.; Mihova, G.; Kunev, B.; Pirov, J.; Dimitrov, D.A.

2009-01-01

Samples with nominal composition MoSr 2 HoCu 2 O 8-δ were synthesized and their magnetic and superconducting (SC) properties were investigated. The obtained samples are Mo-deficient. It was established that the magnetic order is of a long-range type. The coincidence of the experimental value of the Curie constant and the theoretical one of MoSr 2 HoCu 2 O 8-δ shows that the observed magnetic properties of the samples are determined by the highly dominating phase Mo-1212. The two-step resistive SC transition, together with the absence of both diamagnetism and a peak in the specific heat between the two critical temperatures may be associated with the presence of a granular superconductivity. The effect of the Mo-deficiency on the magnetic and SC properties of MoSr 2 HoCu 2 O 8-δ was discussed

Superconducting properties of powder-metallurgically produced Cu-Nb3Sn composite wires

International Nuclear Information System (INIS)

Schaper, W.; Wecker, J.; Heine, K.; Bormann, R.; Freyhardt, H.C.

1988-01-01

The critical current density of composite superconducting wires can be improved by ternary or quaternary additions. If these additions are incorporated into the A15 phase the upper critical field can be increased. An increase in this field, however, can only be realized if the additions do not strongly deteriorate the critical temperature. An enhanced upper critical field in connection with a favorable grain size of the A15 phase finally leads to improved critical current densities in the entire field range. With these parameters as guidelines, the effects of Ti, In, Ga, and Ge additions to the bronze and of Ta additions to the niobium on the superconducting properties of PM produced Cu-Nb 3 Sn wires were investigated

Effect of plasma on the superconductive property of YBCO system

International Nuclear Information System (INIS)

Chaudhary, K.A.; Anwar, M.I.; Zakaullah, M.; Alamgir, K.; Murtaza, G.; Haq, A.U.

1999-01-01

Oxygen deficient Y/sub 1/Ba/sub 2/Cu 3/O/sub 7-x/ samples are exposed to the rarefied are discharge. The air plasma has gas and electron temperatures as 170 deg. C and 2.1 eV, respectively. As a result of plasma treatment the semiconducting tetragonal phase transformed into superconducting orthorhombic phase with Tc= 84K the phase relating properties have been investigated by monochromated X-ray diffraction and low temperature resistivity measurements. (author)

Interplay of multiple charge-density-waves and superconductivity in DyTe{sub 3} at high pressures

Energy Technology Data Exchange (ETDEWEB)

Zocco, Diego A. [Institute for Solid State Physics, Karlsruhe Institute of Technology, D-76021 Karlsruhe (Germany); Department of Physics, University of California, San Diego, CA 92093 (United States); Kapuvari, Andreas; Sauer, Aaron; Weber, Frank [Institute for Solid State Physics, Karlsruhe Institute of Technology, D-76021 Karlsruhe (Germany); Paraskevas, Parisiadis; Garbarino, Gaston [European Synchrotron Radiation Facility, F-38043 Grenoble Cedex (France); Fisher, Ian [Department of Applied Physics, Stanford University, CA 94305 (United States); Hamlin, James; Maple, Brian [Department of Physics, University of California, San Diego, CA 92093 (United States)

2015-07-01

DyTe{sub 3} is a quasi-two-dimensional system in which two successive incommensurate charge-density-wave (CDW) states appear upon cooling at ambient pressure (T{sub CDW,1} = 306 K, T{sub CDW,2} = 49 K). The suppression with pressure of the CDW order is followed by the emergence of superconductivity above 1 GPa and below 1.5 K, as shown by our measurements of electrical resistivity and ac-susceptibility. X-ray diffraction (XRD) experiments under pressure indicate that the lower CDW state merges with the upper one at an intermediate pressure, suggesting that the double-CDW state could be accessed directly below a single T{sub CDW}(P) line. The phase diagram obtained from XRD is compared with the results of our recent electrical resistivity experiments.

Interface superconductivity

Energy Technology Data Exchange (ETDEWEB)

Gariglio, S., E-mail: stefano.gariglio@unige.ch [DQMP, Université de Genève, 24 Quai E.-Ansermet, CH-1211 Genève (Switzerland); Gabay, M. [Laboratoire de Physique des Solides, Bat 510, Université Paris-Sud 11, Centre d’Orsay, 91405 Orsay Cedex (France); Mannhart, J. [Max Planck Institute for Solid State Research, 70569 Stuttgart (Germany); Triscone, J.-M. [DQMP, Université de Genève, 24 Quai E.-Ansermet, CH-1211 Genève (Switzerland)

2015-07-15

Highlights: • We discuss interfacial superconductivity, a field boosted by the discovery of the superconducting interface between LaAlO. • This system allows the electric field control and the on/off switching of the superconducting state. • We compare superconductivity at the interface and in bulk doped SrTiO. • We discuss the role of the interfacially induced Rashba type spin–orbit. • We briefly discuss superconductivity in cuprates, in electrical double layer transistor field effect experiments. • Recent observations of a high T{sub c} in a monolayer of FeSe deposited on SrTiO{sub 3} are presented. - Abstract: Low dimensional superconducting systems have been the subject of numerous studies for many years. In this article, we focus our attention on interfacial superconductivity, a field that has been boosted by the discovery of superconductivity at the interface between the two band insulators LaAlO{sub 3} and SrTiO{sub 3}. We explore the properties of this amazing system that allows the electric field control and on/off switching of superconductivity. We discuss the similarities and differences between bulk doped SrTiO{sub 3} and the interface system and the possible role of the interfacially induced Rashba type spin–orbit. We also, more briefly, discuss interface superconductivity in cuprates, in electrical double layer transistor field effect experiments, and the recent observation of a high T{sub c} in a monolayer of FeSe deposited on SrTiO{sub 3}.

Conceptual design of the superconducting magnet system for the helical fusion reactor

International Nuclear Information System (INIS)

Yanagi, Nagato; Hamaguchi, Shinji; Takahata, Kazuya; Natsume, Kyohei

2013-01-01

Current status of conceptual design of superconducting magnet system and low temperature system for the helical fusion reactor are introduced. There are three kinds of candidates of superconducting magnets such as Cable-in-conduit (CIC), Low-Temperature Superconductor (LTS) and High-Temperature Superconductor (HTS). Their characteristic properties, coil designs and cooling systems are stated. The freezer and low temperature distribution system, bus line and current lead, and excitation power source for superconducting coil are reported. The various elements of superconducting magnet system of FFHR-d1, partial cross section of FFHR helical coil using CIC, conceptual diagram of helical coil winding method of FFHR using CIC, relation among mass flow of supercritical helium supplied into CIC conductor and temperature increasing and pressure loss, cross section structure of LTS indirect-cooling conductor at 100 kA, cross section of 100-kA HTS conductor, connection method of helical coil segment and YBCO conductor are illustrated. (S.Y.)

Superconducting properties of Ca{sub 1−x}RE{sub x}Fe{sub 2}As{sub 2} (RE: Rare Earths)

Energy Technology Data Exchange (ETDEWEB)

Tamegai, T., E-mail: tamegai@ap.t.u-tokyo.ac.jp [Department of Applied Physics, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); JST, Transformative Research-Project on Iron Pnictides (TRIP), Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Ding, Q.P. [Department of Applied Physics, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); JST, Transformative Research-Project on Iron Pnictides (TRIP), Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Ishibashi, T. [Department of Applied Physics, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Nakajima, Y. [Department of Applied Physics, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); JST, Transformative Research-Project on Iron Pnictides (TRIP), Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan)

2013-01-15

Highlights: ► Superconducting properties in rare-earth doped CaFe{sub 2}As{sub 2} single crystals are characterized. ► Sharp resistive transitions with small anisotropy parameter of ∼1.75 are observed. ► Average critical current density is much smaller than other iron-based superconductors. ► Magneto-optical imaging confirms very inhomogeneous superconducting state. -- Abstract: We have grown rare-earth doped CaFe{sub 2}As{sub 2} single crystals and characterized their normal and superconducting properties. Temperature dependence of resistivity and its absolute value suggest good metallic conduction, suppressing antiferromagnetic (AF) transition in the undoped sample. Hall coefficient shows little temperature dependence, consistent with the suppression AF state. Superconducting transitions characterized by resistivity drops in magnetic fields for both parallel to c-axis and ab-plane are reasonably sharp with a weak anisotropy parameter ∼1.75. Despite these observations, average critical current density estimated from the bulk magnetization is orders of magnitude smaller than other typical iron-based superconductors. Magneto-optical imaging confirms very inhomogeneous superconducting state.

Superconducting machines. Chapter 4

International Nuclear Information System (INIS)

Appleton, A.D.

1977-01-01

A brief account is given of the principles of superconductivity and superconductors. The properties of Nb-Ti superconductors and the method of flux stabilization are described. The basic features of superconducting d.c. machines are illustrated by the use of these machines for ship propulsion, steel-mill drives, industrial drives, aluminium production, and other d.c. power supplies. Superconducting a.c. generators and their design parameters are discussed. (U.K.)

Materials and mechanisms of hole superconductivity

Energy Technology Data Exchange (ETDEWEB)

Hirsch, J.E., E-mail: jhirsch@ucsd.edu [Department of Physics, University of California, San Diego, La Jolla, CA 92093-0319 (United States)

2012-01-15

We study the applicability of the model of hole superconductivity to materials. Both conventional and unconventional materials are considered. Many different classes of materials are discussed. The theory is found suitable to describe all of them. No other theory of superconductivity can describe all these classes of materials. The theory of hole superconductivity proposes that there is a single mechanism of superconductivity that applies to all superconducting materials. This paper discusses several material families where superconductivity occurs and how they can be understood within this theory. Materials discussed include the elements, transition metal alloys, high T{sub c} cuprates both hole-doped and electron-doped, MgB{sub 2}, iron pnictides and iron chalcogenides, doped semiconductors, and elements under high pressure.

New sulfur hydride H{sub 3}S and excellent superconductivity at high

Energy Technology Data Exchange (ETDEWEB)

Cui, Tian [State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun (China)

2016-07-01

It is predicted theoretically that molecular hydrogen would dissociate into an atomic phase with metallic properties at high pressures. Metallic hydrogen is believed to be a room-temperature superconductor. However, metallization of hydrogen is still debates in laboratory. As an alternative, hydrogen-rich compounds are extensively explored since their metallization can happen at relatively lower pressures by means of chemical pre-compressions. Here, a new sulfur hydride H{sub 3}S that hardly occur at atmospheric pressure was predicted to be formed at high pressure by two main ways. We also found two intriguing metallic structures with R3m and Im-3m symmetries above 111 GPa and 180 GPa, respectively. Remarkably, the estimated T{sub c} of Im-3m phase at 200 GPa achieves a very high value of 191-204 K, reaching an order of 200 K. Further calculation shown that the H atoms play a significant role in superconductivity. The experimental discovery of superconductivity with a high T{sub c} = 203 K in H-S system at high pressure has verified our theoretically predicted results. Furthermore, the predicted R3m and Im-3m structures have been recently confirmed experimentally by synchrotron XRD.

Anomalous properties and coexistence of antiferromagnetism and superconductivity near a quantum critical point in rare-earth intermetallides

International Nuclear Information System (INIS)

Val’kov, V. V.; Zlotnikov, A. O.

2013-01-01

Mechanisms of the appearance of anomalous properties experimentally observed at the transition through the quantum critical point in rare-earth intermetallides have been studied. Quantum phase transitions are induced by the external pressure and are manifested as the destruction of the long-range antiferromagnetic order at zero temperature. The suppression of the long-range order is accompanied by an increase in the area of the Fermi surface, and the effective electron mass is strongly renormalized near the quantum critical point. It has been shown that such a renormalization is due to the reconstruction of the quasiparticle band, which is responsible for the formation of heavy fermions. It has been established that these features hold when the coexistence phase of antiferromagnetism and superconductivity is implemented near the quantum critical point.

Superconducting rotating machines

International Nuclear Information System (INIS)

Smith, J.L. Jr.; Kirtley, J.L. Jr.; Thullen, P.

1975-01-01

The opportunities and limitations of the applications of superconductors in rotating electric machines are given. The relevant properties of superconductors and the fundamental requirements for rotating electric machines are discussed. The current state-of-the-art of superconducting machines is reviewed. Key problems, future developments and the long range potential of superconducting machines are assessed

Earlier and recent aspects of superconductivity

International Nuclear Information System (INIS)

Bednorz, J.G.; Muller, K.A.

1990-01-01

Contemporary knowledge of superconductivity is set against its historical background in this book. First, the highlights of superconductivity research in the twentieth century are reviewed. Further contributions then describe the basic phenomena resulting from the macroscopic quantum state of superconductivity (such as zero resistivity, the Meissner-Ochsenfeld effect, and flux quantization) and review possible mechanisms, including the classical BCS theory and the more recent alternative theories. The main categories of superconductors - elements, intermetallic phases, chalcogenides, oxides and organic compounds - are described. Common features and differences in their structure and electronic properties are pointed out. This overview of superconductivity is completed by a discussion of properties related to the coherence length

High pressure apparatus for neutron scattering at low temperature

International Nuclear Information System (INIS)

Munakata, Koji; Uwatoko, Yoshiya; Aso, Naofumi

2010-01-01

Effects of pressure on the physical properties are very important for understanding highly correlated electron systems, in which pressure-induced attractive phenomena such as superconductivity and magnetically ordered non-Fermi liquid have been observed. Up to now, many scientists have developed a lot of high pressure apparatus for each purpose. The characteristic features of various materials and pressure transmitting media for use of high pressure apparatus are reported. Then, two kinds of clamp type high-pressure cell designed for low-temperature neutron diffraction measurements are shown; one is a piston cylinder type high-pressure cell which can be attached to the dilution refrigerator, and the other one is a newly-developed cubic anvil type high-pressure cell which can generate pressure above 7GPa. We also introduce the results of magnetic neutron scattering under pressure on a pressure-induced superconducting ferromagnet UGe 2 in use of the piston cylinder type clamp cell, and those on an iron arsenide superconductor SrFe 2 As 2 in use of the cubic anvil type clamp cell. (author)

Superconductive analogue of spin glasses

International Nuclear Information System (INIS)

Feigel'man, M.; Ioffe, L.; Vinokur, V.; Larkin, A.

1987-07-01

The properties of granular superconductors in magnetic fields, namely the existence of a new superconductive state analogue of the low-temperature superconductive state in spin glasses are discussed in the frame of the infinite-range model and the finite-range models. Experiments for elucidation of spin-glass superconductive state in real systems are suggested. 30 refs

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 .

Growth, characterization, and physical properties of Bi-Sr-Ca-Cu-O superconducting whiskers

International Nuclear Information System (INIS)

Kraak, W.; Thiele, P.

1996-01-01

Single crystal whiskers of the Bi-based high-T c superconductors have been grown directly from the stoichiometric melt. Conditions for the preferable growth of the (2212) phase and annealing conditions for the conversion from the (2212) phase to the (2223) and (2234) Bi-based superconducting phases are achieved. The orientation and chemical composition of the crystals were characterized by X-ray diffractometry and energy dispersive X-ray analysis. Characteristic structural properties of the whiskers (incommensurable modulation in b-direction, peculiarities of dislocation networks) have been revealed by transmission electron microscopy and electron diffraction. Some special features of the broad superconducting transition in multiphase whiskers have been examined by spatially resolved measurements using low-temperature scanning electron microscopy. (orig.)

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

International Nuclear Information System (INIS)

Sanchez Valdes, C.F.; Perez-Penichet, C.; Noda, C.; Arronte, M.; Batista-Leyva, A.J.; Haugen, O.; Johansen, T.H.; Han, Z.; Altshuler, E.

2007-01-01

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

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.

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

International Nuclear Information System (INIS)

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

2015-01-01

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. (paper)

Superconductivity: Phenomenology

International Nuclear Information System (INIS)

Falicov, L.M.

1988-08-01

This document discusses first the following topics: (a) The superconducting transition temperature; (b) Zero resistivity; (c) The Meissner effect; (d) The isotope effect; (e) Microwave and optical properties; and (f) The superconducting energy gap. Part II of this document investigates the Ginzburg-Landau equations by discussing: (a) The coherence length; (b) The penetration depth; (c) Flux quantization; (d) Magnetic-field dependence of the energy gap; (e) Quantum interference phenomena; and (f) The Josephson effect

Superconducting thin films of Bi-Sr-Ca-Cu-O by laser ablation

Science.gov (United States)

Bedekar, M. M.; Safari, A.; Wilber, W.

1992-11-01

Superconducting thin films of Bi-Sr-Ca-Cu-O have been deposited by KrF excimer laser ablation. The best in situ films showed a Tc onset of 110 K and a Tc(0) of 76 K. A study of the laser plume revealed the presence of two distinct regimes. The forward directed component increased with fluence and the film composition was stoichiometric in this region. This is in agreement with the results on the 123 system by Venkatesan et al. [1]. The film properties were found to be critically dependent on the substrate temperature and temperatures close to melting gave rise to 2212 and 2223 phases. At lower temperatures, 2201 and amorphous phases were obtained. The film morphology and superconducting properties were a function of the target to substrate distance and the oxygen pressure during deposition and cooling. An increase in the target to substrate distance led to a deterioration of the properties due to the energy consideration for the formation of 2212 and 2223 phases. The best films were obtained using cooling pressures of 700 Torr. The microwave surface resistance of the films measured at 35 GHz dropped below that of copper at 30 K. Film growth was studied using X-ray diffraction and STM/AFM. This work is a discussion of the role of the different variables on the film properties.

Multiple quantum phase transitions and superconductivity in Ce-based heavy fermions.

Science.gov (United States)

Weng, Z F; Smidman, M; Jiao, L; Lu, Xin; Yuan, H Q

2016-09-01

Heavy fermions have served as prototype examples of strongly-correlated electron systems. The occurrence of unconventional superconductivity in close proximity to the electronic instabilities associated with various degrees of freedom points to an intricate relationship between superconductivity and other electronic states, which is unique but also shares some common features with high temperature superconductivity. The magnetic order in heavy fermion compounds can be continuously suppressed by tuning external parameters to a quantum critical point, and the role of quantum criticality in determining the properties of heavy fermion systems is an important unresolved issue. Here we review the recent progress of studies on Ce based heavy fermion superconductors, with an emphasis on the superconductivity emerging on the edge of magnetic and charge instabilities as well as the quantum phase transitions which occur by tuning different parameters, such as pressure, magnetic field and doping. We discuss systems where multiple quantum critical points occur and whether they can be classified in a unified manner, in particular in terms of the evolution of the Fermi surface topology.

Interactions between superconductivity and quantum criticality in CeCoIn5, URhGe and UCoGe

International Nuclear Information System (INIS)

Howald, L.

2011-01-01

The subject of this thesis is the analyze of the superconducting upper critical field (Hc2) and the interaction between superconductivity and quantum critical points (QCP), for the compounds CeCoIn 5 , URhGe and UCoGe. In CeCoIn 5 , study by mean of resistivity of the Fermi liquid domain allows us to localize precisely the QCP at ambient pressure. This analyze rule out the previously suggested pinning of Hc2(0) at the QCP. In a second part, the evolution of Hc2 under pressure is analyzed. The superconducting dome is unconventional in this compound with two characteristic pressures: at 1.6 GPa, the superconducting transition temperature is maximum but it is at 0.4 GPa that physical properties (maximum of Hc2(0), maximum of the initial slope dHc2/dT, maximum of the specific heat jump DC/C,... ) suggest a QCP. We explain this antagonism with pair-breaking effects in the proximity of the QCP. With these two experiments, we suggest a new phase diagram for CeCoIn 5 . In a third part, measurements of thermal conductivity on URhGe and UCoGe are presented. We obtained the bulk superconducting phase transition and confirmed the unusual curvature of the slope dHc2/dT observed by resistivity. The temperatures and fields dependence of thermal conductivity allow us to identify a non-electronic contribution for heat transport down to the lowest temperature (50 mK) and probably associated with magnon or longitudinal fluctuations. We also identified two different domains in the superconducting region, These domains are compatible with a two bands model for superconductivity. Thermopower measurements on UCoGe reveal a strong anisotropy to current direction and several anomaly under field applied in the b direction. We suggest a Lifshitz transition to explain our observations in these two compounds. (author) [fr

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

International Nuclear Information System (INIS)

Ishizuka, M.; Hamajima, T.; Itou, T.; Sakuraba, J.; Nishijima, G.; Awaji, S.; Watanabe, K.

2010-01-01

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 3 Sn superconducting wires particularly showed a low mechanical strength due to those brittle property, Nb 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 ∂Bz/∂z) of 4500 T 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 3 Sn layer and its large diameter formed on Nb-barrier component in Nb 3 Sn wires.

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

Energy Technology Data Exchange (ETDEWEB)

Liu, Wei; Zhang, Xingyi, E-mail: zhangxingyi@lzu.edu.cn; Liu, Cong; Zhang, Wentao; Zhou, Jun; Zhou, YouHe [Key Laboratory of Mechanics on Disaster and Environment in Western China Attached to the Ministry of Education of China, Lanzhou University, Lanzhou, Gansu 730000, People’s Republic of China and Department of Mechanics and Engineering Sciences, College of Civil Engineering and Mechanics, Lanzhou University, Lanzhou, Gansu 730000 (China)

2016-07-15

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.

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. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

Levitation properties of a ring-shaped flywheel supported by high Tc superconducting levitation

International Nuclear Information System (INIS)

Teshima, Hidekazu; Tawara, Taichi; Shimada, Ryuichi.

1997-01-01

In this paper we propose a new combination of high T c superconducting levitation and ring-shaped flywheel energy storage systems. Superconducting levitation is appropriate for rotating a ring-shaped flywheel which has neither shaft nor hub, because it is a non-contact and automatically stable levitation without any control systems. The levitation properties such as static and dynamic lateral stiffnesses, lateral damping, and lateral vibration during rotation have been investigated using a small-scaled experimental machine consisting of 16 bulk superconductors 46 mm in diameter and a ring-shaped flywheel about 300 mm in diameter. The spring constant increased as the levitation gap height decreased, and the dynamic spring constant was slightly higher than the static constant. The damping coefficient increased as the gap height decreased and the vibration amplitude increased. The experimental critical speed was in good agreement with the calculated one using a one-degree of freedom model. Finally, the possibility of large-scaled practical systems is discussed from the viewpoint of superconducting levitation. (author)

High-pressure studies on a new superconducting clathrate: Ba sub 6 Ge sub 2 sub 5

CERN Document Server

Yuan, H Q; Carrillo-Cabrera, W; Paschen, S; Sparn, G; Baenitz, M; Grin, Y; Steglich, F

2002-01-01

The effect of pressure on the low-temperature states of the newly discovered clathrate Ba sub 6 Ge sub 2 sub 5 is investigated by means of measurements of the electrical resistivity. At ambient pressure, Ba sub 6 Ge sub 2 sub 5 undergoes a two-step structural phase transition between 230 and 180 K from metallic behaviour to a high-resistivity state characterized by a mean free path of about 3 A. Interestingly, a Bardeen-Cooper-Schrieffer-like (BCS-like) superconducting transition occurs at T sub C approx 0.24 K from the resulting 'bad metal'. With increasing pressure, the structural phase transition is depressed but T sub C increases drastically. T sub C reaches a maximum value of 3.85 K at the critical pressure p sub C approx 2.8 GPa, where the structural distortion is completely suppressed and the system exhibits metallic behaviour. Higher pressures lead to a slight decrease of T sub C.

Synthesis and pressure effects on the La doped CaFe{sub 2}As{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Shin, Soo Hyun; Park, Tuson [Dept. of physics, Sungkyunkwan University, Suwon (Korea, Republic of); Shang, T.; Yuan, H. Q. [Dept. of physics, Zhejiang University, Hangzhou (China)

2014-09-15

We have synthesized La doped CaFe2As{sub 2} single crystals with Sn flux in an evacuated quartz ampule. Doping and pressure effects on the magnetic and superconducting properties of the under-doped Ca{sub 1-x}La{sub x}Fe{sub 2}As{sub 2} (x=0.08, 0.1) were studied by measuring electrical resistivity under quasi-hydrostatic pressure up to 21 kbar. Magnetic transition temperatures for all studied concentrations were sharply suppressed with slight amplitude of pressure, less than 3 kbar, while superconducting transition temperatures were robust against pressure. In this communication, we report temperature-pressure phase diagram for the La-doped CaFe{sub 2}As{sub 2} single crystals.

Electronic structure and superconductivity of europium

International Nuclear Information System (INIS)

Nixon, Lane W.; Papaconstantopoulos, D.A.

2010-01-01

We have calculated the electronic structure of Eu for the bcc, hcp, and fcc crystal structures for volumes near equilibrium up to a calculated 90 GPa pressure using the augmented-plane-wave method in the local-density approximation. The frozen-core approximation was used with a semi-empirical shift of the f-states energies in the radial Schroedinger equation to move the occupied 4f valence states below the Γ 1 energy and into the core. This shift of the highly localized f-states yields the correct europium phase ordering with lattice parameters and bulk moduli in good agreement with experimental data. The calculated superconductivity properties under pressure for the bcc and hcp structures are also found to agree with and follow a T c trend similar to recent measurement by Debessai et al.

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).

Diatomic substitutionals in superconducting Nb(1-x)B2

International Nuclear Information System (INIS)

Farrell, H.H.; LaViolette, Randall A.; Lillo, T.M.

2006-01-01

Using first-principles, density functional theory calculations, we have shown that the increase in superconducting critical temperature to above 9 K experimentally observed for B-rich, off-stoichiometry NbB 2 material is associated with the formation of B-dimers on Nb sites rather than with the formation of Nb vacancies, as previously proposed. Our calculations show that certain of these B-dimer configurations have lower binding energies than do the vacancy structures. This result is pressure independent in the range between 0 and 10 GPa, and above. Further, the dimer-containing materials have a higher electronic density of states at the Fermi level than do the vacancy structures. Finally, the presence of B-dimers results in the splitting off of phonon normal modes. These last two factors are relevant to the improved superconducting properties

Superconducting, magnetic and magnetotransport properties of FeTe1-xSex single crystals

Science.gov (United States)

Kumar, Rohit; Sudesh, Varma, G. D.

2018-05-01

The single crystalline samples with compositions FeTe1-xSex (0.25 ≤ x ≤ 0.50) have been prepared via self-flux method and the superconducting, magnetic and magnetotransport properties of the grown crystals were investigated. The superconducting onset temperatures have been determined from the measurements of zero field cooled magnetization and resistance with temperatures. In the present case, highest superconducting transition temperature TC (onset) ˜ 15 K has been obtained for x=0.5. The HC2 (T=0 K) values have been estimated by fitting the experimental HC2 - T plots with WHH model. The highest HC2(0) has been obtained for x=0.5. The activation energy of the thermally activated flux flow has been found from the broadening of superconducting transition in an applied magnetic field using the Arrhenius law. Our results show that the activation energy (U0) decreases with the increasing magnetic field. Furthermore, the magnetization measurements for x=0.4 and 0.5 samples have been performed at T=5 K in the magnetic field range ±7 T to estimate critical current density at different applied magnetic fields using Bean formula. We see that the sample x=0.5 has higher values of JC as compared to that of x=0.4 at all magnetic fields. This is in conformity with the behavior of U0-H plots.

Superconducting properties of the hexagonal-close-packed alloy system TcZr

International Nuclear Information System (INIS)

Chatterjee, P.

1984-01-01

The theoretical formula of McMillan, modified via the multiple-scattering theory of Gomersall and Gyorffy, is very successful in computing the electron-phonon coupling constant (lambda) and the superconducting transition temperature (T/sub c/) of elements and compounds from quantities readily obtainable from band structure work or approaches based on the scattering theory. However, for disordered solids this theory fails because of the breakdown of the translational symmetry used in the multiple scattering theory. In the particular case of substitutional alloys, the problem can still be solved however if, at each lattice point, the t-matrix of an individual scatterer is replaced by a configurational average of the t-matrices of the alloying materials (average t-matrix approximation). This modified theory, which has already been successfully applied to some cubic substitutional alloys, is herein used to predict lambda and T/sub c/ for the h.c.p. TcZr alloy system. The results indicate that this system has good superconducting properties. (author)

Superconducting and normal-state properties of the layered boride OsB2

Science.gov (United States)

Singh, Yogesh; Niazi, A.; Vannette, M. D.; Prozorov, R.; Johnston, D. C.

2007-12-01

OsB2 crystallizes in an orthorhombic structure (Pmmn) which contains alternate boron and osmium layers stacked along the c axis. The boron layers consist of puckered hexagons as opposed to the flat graphite-like boron layers in MgB2 . OsB2 is reported to become superconducting below 2.1K . We report results of the dynamic and static magnetic susceptibilities, electrical resistivity, Hall effect, heat capacity, and penetration depth measurements on arc-melted polycrystalline samples of OsB2 to characterize its superconducting and normal-state properties. These measurements confirmed that OsB2 becomes a bulk superconductor below Tc=2.1K . Our results indicate that OsB2 is a moderate-coupling type-II superconductor with an electron-phonon coupling constant λep≈0.4-0.5 , a small Ginzburg-Landau parameter κ˜1-2 , and an upper critical magnetic field Hc2(0.5K)˜420Oe for an unannealed sample and Hc2(1K)˜330Oe for an annealed sample. The temperature dependence of the superfluid density ns(T) for the unannealed sample is consistent with an s -wave superconductor with a slightly enhanced zero temperature gap Δ(0)=1.9kBTc and a zero temperature London penetration depth λ(0)=0.38(2)μm . The ns(T) data for the annealed sample show deviations from the predictions of the single-band s -wave BCS model. The magnetic, transport, and thermal properties in the normal state of isostructural and isoelectronic RuB2 , which is reported to become superconducting below 1.6K , are also reported.

Competition between disorder and exchange splitting in superconducting ZrZn2

International Nuclear Information System (INIS)

Powell, B J; Annett, James F; Gyoerffy, B L

2003-01-01

We propose a simple picture for the occurrence of superconductivity and the pressure dependence of the superconducting critical temperature, T SC , in ZrZn 2 . According to our hypothesis the pairing potential is independent of pressure, but the exchange splitting, E xc , leads to a pressure dependence in the (spin dependent) density of states at the Fermi level, D σ (ε F ). Assuming p-wave pairing T SC is dependent on D σ (ε F ) which ensures that, in the absence of non-magnetic impurities, T SC decreases as pressure is applied until it reaches a minimum in the paramagnetic state. Disorder reduces this minimum to zero, this gives the illusion that the superconductivity disappears at the same pressure as ferromagnetism does. (letter to the editor)

Superconductivity: materials and applications

International Nuclear Information System (INIS)

Duchateau, J.L.; Kircher, F.; Leveque, J.; Tixador, P.

2008-01-01

This digest paper presents the different types of superconducting materials: 1 - the low-TC superconductors: the multi-filament composite as elementary constituent, the world production of NbTi, the superconducting cables of the LHC collider and of the ITER tokamak; 2 - the high-TC superconductors: BiSrCaCuO (PIT 1G) ribbons and wires, deposited coatings; 3 - application to particle physics: the the LHC collider of the CERN, the LHC detectors; 4 - applications to thermonuclear fusion: Tore Supra and ITER tokamaks; 5 - NMR imaging: properties of superconducting magnets; 6 - applications in electrotechnics: cables, motors and alternators, current limiters, transformers, superconducting energy storage systems (SMES). (J.S.)

Superconductivity in power engineering

International Nuclear Information System (INIS)

1989-01-01

This proceedings volume presents 24 conference papers and 15 posters dealing with the following aspects: 1) Principles and elementary aspects of high-temperature superconductivity (3 plenary lectures); 2) Preparation, properties and materials requirements of metallic or oxide superconductors (critical current behaviour, soldered joints, structural studies); 3) Magnet technology (large magnets for thermonuclear fusion devices; magnets for particle accelerators and medical devices); 4) Magnetic levitation and superconductivity; 5) Cryogenics; 6) Energy storage systems using superconducting coils (SMES); 7) Superconducting power transmission cables, switches, transformers, and generator systems for power plant; 8) Supporting activities, industrial aspects, patents. There are thirty-eight records in the ENERGY database relating to individual conference papers. (MM) [de

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.

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

Anomalous pressure dependence of the superconducting transition temperature in the β-Pyrochlore KOs2O6

Science.gov (United States)

Miyoshi, Kiyotaka; Takaichi, Yuta; Takeuchi, Jun

2009-03-01

DC magnetic measurements have been performed for β-pyrochlore superconductor KOs2O6 (Tc = 9.6 K) under pressure for the precise determination of the pressure dependence of Tc, using a miniature diamond anvil cell combined with a commercial SQUID magnetometer. It is found that the critical temperature Tc shows a maximum of ~10 K at P=0.5 GPa. The maximum of Tc is higher than that for CsOs2O6 and RbOs2O6, in both of which Tc is known to increase and saturate at Tcm = 8.8 K by the application of pressure, suggesting the enhanced superconductivity due to the rattling of K ions in an oversized cage of Os-O network. For the further application of pressure, Tc decreases linearly but the decreasing rate appears to be suddenly changed at P~2 GPa and Tc~8 K. The sharp bend of the Tc — P line probably corresponds to the transition concerning to the rattling motion which occurs at Tp=7.5 K at ambient pressure, suggesting the positive pressure dependence of Tp.

Superconducting wind turbine generators

International Nuclear Information System (INIS)

Abrahamsen, A B; Seiler, E; Zirngibl, T; Andersen, N H; Mijatovic, N; Traeholt, C; Pedersen, N F; Oestergaard, J; Noergaard, P B

2010-01-01

We have examined the potential of 10 MW superconducting direct drive generators to enter the European offshore wind power market and estimated that the production of about 1200 superconducting turbines until 2030 would correspond to 10% of the EU offshore market. The expected properties of future 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, 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 MW is suggested to secure the accumulation of reliability experience. Finally, the quantities of high temperature superconducting tape needed for a 10 kW and an extreme high field 10 MW generator are found to be 7.5 km and 1500 km, respectively. A more realistic estimate is 200-300 km of tape per 10 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.

A change of electronic state tuned by pressure: pressure-induced superconductivity of the antiferromagnet Ce{sub 2}Ni{sub 3}Ge{sub 5}

Energy Technology Data Exchange (ETDEWEB)

Nakashima, M [Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan); Research Center for Materials Science at Extreme Conditions, Osaka University, Toyonaka, Osaka 560-8531 (Japan); Kohara, H [Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan); Thamizhavel, A [Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan); Matsuda, T D [Advanced Science and Industrial Research Center, Japan Atomic Energy Research Institute, Tokai, Ibaraki 319-1195 (Japan); Haga, Y [Advanced Science and Industrial Research Center, Japan Atomic Energy Research Institute, Tokai, Ibaraki 319-1195 (Japan); Hedo, M [Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581 (Japan); Uwatoko, Y [Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581 (Japan); Settai, R [Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan); Onuki, Y [Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan); Advanced Science and Industrial Research Center, Japan Atomic Energy Research Institute, Tokai, Ibaraki 319-1195 (Japan)

2005-07-20

We measured the electrical resistivity of an antiferromagnet Ce{sub 2}Ni{sub 3}Ge{sub 5} with the orthorhombic crystal structure under pressure. The Neel temperature T{sub N} = 5.2K decreases with increasing pressure P and becomes zero at a critical P{sub c} {approx} 3.9 GPa. The A and {rho}{sub 0} values of the low-temperature electrical resistivity {rho} = {rho}{sub 0}+AT{sup 2} in the Fermi liquid relation increase steeply above 3 GPa. A value of A 10.7{omega}cmK{sup -2} at 3.9?GPa is comparable to A = 10{omega}cmK{sup -2} in a heavyfermion superconductor CeCu{sub 2}Si{sub 2}. The heavy fermion state was found to be formed around P{sub c}, in which pressure region superconductivity was found below 0.26K.

Hydrostatic pressure study of the structural phase transitions and superconductivity in single crystals of (Ba1-xKx)Fe2As2 (x=0 and 0.45) and CaFe2As2

International Nuclear Information System (INIS)

Torikachvili, M.S.; Bud'ko, S.L.; Ni Ni; Canfield, P.C.

2009-01-01

We studied the effect of hydrostatic pressure (P) on the structural phase transitions and superconductivity in the ternary and pseudo-ternary iron arsenides CaFe 2 As 2 , BaFe 2 As 2 , and (Ba 0.55 K 0.45 )Fe 2 As 2 , by means of measurements of electrical resistivity (ρ) in the 1.8-300 K temperature (T) range, pressures up to 20 kbar, and magnetic fields up to 9 T. CaFe 2 As 2 and BaFe 2 As 2 (lightly doped with Sn) display structural phase transitions near 170 and 85 K, respectively, and do not exhibit superconductivity in ambient pressure, while K-doped (Ba 0.55 K 0.45 )Fe 2 As 2 is superconducting for T 2 As 2 is to shift the onset of the crystallographic transformation down in temperature at the rate of ∼-1.04 K/kbar, while shifting the whole ρ(T) curves downward, whereas its effect on superconducting (Ba 0.55 K 0.45 )Fe 2 As 2 is to shift the onset of superconductivity to lower temperatures at the rate of ∼-0.21 K/kbar. The effect of pressure on CaFe 2 As 2 is first to suppress the crystallographic transformation and induce superconductivity with onset near 12 K very rapidly, i.e., for P c2 ) data in (Ba 0.55 K 0.45 )Fe 2 As 2 and CaFe 2 As 2 are discussed.

Superconductivity and magnetism: Materials properties and developments

International Nuclear Information System (INIS)

Andersen, N.H.; Bay, N.; Grivel, J.C.

2003-01-01

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 c superconductivity, magnetic superconductors, MgB 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)

Pressure dependence of the Raman spectrum, lattice parameters and superconducting critical temperature of MgB2: evidence for pressure-driven phonon-assisted electronic topological transition

International Nuclear Information System (INIS)

Goncharov, A.F.; Struzhkin, V.V.

2003-01-01

We overview recent high-pressure studies of high-temperature superconductor MgB 2 by Raman scattering technique combined with measurements of superconducting critical temperature T c and lattice parameters up to 57 GPa. An anomalously broadened Raman band at 620 cm -1 is observed and assigned to the in-plane boron stretching E 2g mode. It exhibits a large Grueneisen parameter indicating that the vibration is highly anharmonic. The pressure dependencies of the E 2g mode and T c reveal anomalies at 15-22 GPa (isotope dependent). The anharmonic character of the E 2g phonon mode, its anomalous pressure dependence, and also that for T c are interpreted as a result of a phonon-assisted Lifshitz electronic topological transition

Superconductivity in high energy particle accelerators

International Nuclear Information System (INIS)

Schmueser, P.

2002-08-01

The basics of superconductivity are outlined with special emphasis on the features which are relevant for the application in magnets and radio frequency cavities for high energy particle accelerators. The special properties of superconducting accelerator magnets are described in detail: design principles, magnetic field calculations, magnetic forces, quench performance, persistent magnetization currents and eddy currents. The design principles and basic properties of superconducting cavities are explained as well as the observed performance limitations and the countermeasures. The ongoing research efforts towards maximum accelerating fields are addressed and the coupling of radio frequency power to the particle beam is treated. (orig.)

Superconductivity and its devices

International Nuclear Information System (INIS)

Forbes, D.S.

1981-01-01

Among the more important developments that are discussed are cryotrons, superconducting motors and generators, and high-field magnets. Cryotrons will create faster and more economical computer systems. Superconducting motors and generators will cost much less to build than conventional electric generators and cut fuel consumption. Moreover, high-field magnets are being used to confine plasma in connection with nuclear fusion. Superconductors have a vital role to play in all of these developments. Most importantly, though, are the magnetic properties of superconductivity. Superconducting magnets are an integral part of nuclear fusion. In addition, high-field magnets are necessary in the use of accelerators, which are needed to study the interactions between elementary particles

Superconductivity and magnetism: Materials properties and developments

Energy Technology Data Exchange (ETDEWEB)

Andersen, N H; Bay, N; Grivel, J C [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)

Influence of substitutional disorder on the electrical transport and the superconducting properties of Fe1+zTe1−x−ySexSy

International Nuclear Information System (INIS)

Rodríguez, M.G.; Polla, G.; Ramos, C.P.; Acha, C.

2015-01-01

We have carried out an investigation of the structural, magnetic, transport and superconducting properties of Fe 1+z Te 1−x−y Se x S 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 L becomes smaller than the coherence length ξ 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

Color superconductivity

International Nuclear Information System (INIS)

Wilczek, F.

1997-01-01

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

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.

Superconductivity

International Nuclear Information System (INIS)

Buller, L.; Carrillo, F.; Dietert, R.; Kotziapashis, A.

1989-01-01

Superconductors are materials which combine the property of zero electric resistance with the capability to exclude any adjacent magnetic field. This leads to many large scale applications such as the much publicized levitating train, generation of magnetic fields in MHD electric generators, and special medical diagnostic equipment. On a smaller-scale, superconductive materials could replace existing resistive connectors and decrease signal delays by reducing the RLC time constants. Thus, a computer could operate at much higher speeds, and consequently at lower power levels which would reduce the need for heat removal and allow closer spacing of circuitry. Although technical advances and proposed applications are constantly being published, it should be recognized that superconductivity is a slowly developing technology. It has taken scientists almost eighty years to learn what they now know about this material and its function. The present paper provides an overview of the historical development of superconductivity and describes some of the potential applications for this new technology as it pertains to the electronics industry

Crystal structure of 200 K-superconducting phase in sulfur hydride system

Energy Technology Data Exchange (ETDEWEB)

Einaga, Mari; Sakata, Masafumi; Ishikawa, Takahiro; Shimizu, Katsuya [KYOKUGEN, Graduate School of Engineering Science, Osaka Univ. (Japan); Eremets, Mikhail; Drozdov, Alexander; Troyan, Ivan [Max Planck Institut fuer Chemie, Mainz (Germany); Hirao, Naohisa; Ohishi, Yasuo [JASRI/SPring-8, Hyogo (Japan)

2016-07-01

Superconductivity with the critical temperature T{sub c} above 200 K has been recently discovered by compression of H{sub 2}S (or D{sub 2}S) under extreme pressure. It was proposed that these materials decompose under high pressure to elemental sulfur and hydride with higher content of hydrogen which is responsible for the high temperature superconductivity. In this study, we have investigated that the crystal structure of the superconducting compressed H{sub 2}S and D{sub 2}S by synchrotron x-ray diffraction measurements combined with electrical resistance measurements at room and low temperatures. We found that the superconducting phase is in good agreement with theoretically predicted body-centered cubic structure, and coexists with elemental sulfur, which claims that the formation of 3H{sub 2}S → 2H{sub 3}S + S is occured under high pressure.

A study on the development of high-Tc superconducting wire

International Nuclear Information System (INIS)

Won, Dong Yeon; Chang, In Soon; Lee, Jong Min; Um, Tae Yoon; Hong, Kyae Won; Lee, Ho Jin; Lee, Hee Kwun; Kim, Chan Joong; Park, Soon Dong; Kim, Woo Gon; Kim, Ki Baek; Kwon, Sun Chil

1992-10-01

On this study Y-Ba-Cu-O was prepared by partial melt process and superconducting wire was fabricated by powder-in-tube method. First, mechancial properties, electrical properties, microstructure and oxygen diffusion behavior were observed. Second, through fabricated superconducting wire, conceptual design, composition and plasticity of filament superconducting wire were investigated. (Author)

Superconductivity, spin-glass properties, and ferromagnetism in amorphous La--Gd--Au alloys

International Nuclear Information System (INIS)

Poon, S.J.

1978-01-01

The superconducting and magnetic properties of splat cooled amorphous alloys of composition (La/sub 100-x/Gd/sub x/) 80 Au 20 (0 equal to or less than x equal to or less than 100) have been studied. The La 80 Au 20 alloys are ideal type II superconductors (critical temperature T/sub c/ = 3.5 0 K). The concentration range (x 80 Au 20 . The results are compared with recent theories on amorphous magnetism

Superconducting Ferromagnetic Nanodiamond.

Science.gov (United States)

Zhang, Gufei; Samuely, Tomas; Xu, Zheng; Jochum, Johanna K; Volodin, Alexander; Zhou, Shengqiang; May, Paul W; Onufriienko, Oleksandr; Kačmarčík, Jozef; Steele, Julian A; Li, Jun; Vanacken, Johan; Vacík, Jiri; Szabó, Pavol; Yuan, Haifeng; Roeffaers, Maarten B J; Cerbu, Dorin; Samuely, Peter; Hofkens, Johan; Moshchalkov, Victor V

2017-06-27

Superconductivity and ferromagnetism are two mutually antagonistic states in condensed matter. Research on the interplay between these two competing orderings sheds light not only on the cause of various quantum phenomena in strongly correlated systems but also on the general mechanism of superconductivity. Here we report on the observation of the electronic entanglement between superconducting and ferromagnetic states in hydrogenated boron-doped nanodiamond films, which have a superconducting transition temperature T c ∼ 3 K and a Curie temperature T Curie > 400 K. In spite of the high T Curie , our nanodiamond films demonstrate a decrease in the temperature dependence of magnetization below 100 K, in correspondence to an increase in the temperature dependence of resistivity. These anomalous magnetic and electrical transport properties reveal the presence of an intriguing precursor phase, in which spin fluctuations intervene as a result of the interplay between the two antagonistic states. Furthermore, the observations of high-temperature ferromagnetism, giant positive magnetoresistance, and anomalous Hall effect bring attention to the potential applications of our superconducting ferromagnetic nanodiamond films in magnetoelectronics, spintronics, and magnetic field sensing.

Superconducting devices at Brookhaven National Laboratory

International Nuclear Information System (INIS)

Dahl, P.F.

1978-04-01

The various ongoing programs in applied superconductivity supported by BNL are summarized, including the development of high field ac and dc superconducting magnets for accelerators and other applications, of microwave deflecting cavities for high energy particle beam separators, and of cables for underground power transmission, and materials research on methods of fabricating new superconductors and on metallurgical properties affecting the performance of superconducting devices

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.

Probing the local microwave properties of superconducting thin films by a scanning microwave near-field microscope

CERN Document Server

Wu, L Y; Wang, K L; Jiang, T; Kang, L; Yang, S Z; Wu, P H

2002-01-01

In this paper, we present our approach to probe the local microwave properties of superconducting thin films by using the microwave near-field scanning technique. We have employed a coaxial cavity together with a niobium tip as the probe and established a scanning sample stage cooled by liquid nitrogen to study thin film devices at low temperature in our scanning microwave near-field microscope. Nondestructive images have been obtained on the inhomogeneity of the YBaCuO superconducting thin films at microwave frequency. We believe that these results would be helpful in evaluating the microwave performance of the devices.

NQR study in superconducting La2CuO4+δ

International Nuclear Information System (INIS)

Ueda, K.; Sugata, T.; Kohori, Y.; Oda, Y.; Kohara, T.

1992-01-01

Cu NQR signals were observed around 33.1 and 36.0 MHz together with the antiferromagnetic Cu NMR signals in the superconducting La 2 CuO 4+ δ obtained by annealing in high pressure oxygen gas. The NQR intensity increases with increasing oxygen contents. The nuclear spin-lattice relaxation time, T 1 , of Cu NQR indicates that the paramagnetic phase is in the superconducting state at low temperatures. These results show that the NQR and NMR signals were coming from the Cu sites in the superconducting phase and the antiferromagnetic phase, respectively. No appreciable differences were observed in the Cu NQR spectrum and the relaxation time between the superconducting La 2 CuO 4 + δ samples annealed under the oxygen pressure of 400 ≅ 1200 bar. (orig.)

Abstracts of The First Polish-US Conference on High Temperature Superconductivity

International Nuclear Information System (INIS)

1995-01-01

The current problems in high temperature superconductivity science have been presented at the conference. The two main topics have been mostly represented: superconducting material research and fundamental physical research on superconductivity mechanisms. Superconducting material preparation, chemical composition, magnetic and electrical properties of different type of high temperature superconductors, material structure and its influence on superconducting properties and related problems were included in the first of the general topics. In the range of second general topic of the two listed above, many theoretical models being applied for explanation of superconductivity mechanism in different systems up and below transition temperature were presented

Electronic properties of high-Tc superconductors. The normal and the superconducting state of high-Tc materials. Proceedings

International Nuclear Information System (INIS)

Kuzmany, H.; Mehring, M.; Fink, J.

1993-01-01

The International Winter School on Electronic Properties of High-Temperature Superconductors, held between March 7-14, 1992, in Kirchberg, (Tyrol) Austria, was the sixth in a series of meetings to be held at this venue. Four of the earlier meetings were dedicated to issues in the field of conducting polymers, while the winter school held in 1990 was devoted to the new discipline of high-Tc superconductivity. This year's meeting constituted a forum not only for the large number of scientists engaged in high-Tc research, but also for those involved in the new and exciting field of fullerenes. Many of the issues raised during the earlier winter schools on conducting polymers, and the last one on high-Tc superconductivity, have taken on a new significance in the light of the discovery of superconducting C 60 materials. The Kirchberg meetings are organized in the style of a school where experienced scientists from universities, research laboratories and industry have the opportunity to discuss their most recent results, and where students and young scientists can learn about the present status of research and applications from some of the most eminent workers in their field. In common with the previous winter school on high-Tc superconductors, the present one focused on the electronic properties of the cuprate superconductors. In addition, consideration was given to related compounds which are relevant to the understanding of the electronic structure of the cuprates in the normal state, to other oxide superconductors and to fulleride superconductors. Contributions dealing with their preparation, transport and thermal properties, high-energy spectroscopies, nuclear magnetic resonance, inelastic neutron scattering, and optical spectroscopy are presented in this volume. The theory of the normal and superconducting states also occupies a central position. (orig.)

High temperature interface superconductivity

International Nuclear Information System (INIS)

Gozar, A.; Bozovic, I.

2016-01-01

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_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_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.

Design-relevant mechanical properties of 316-type stainless steels for superconducting magnets

Energy Technology Data Exchange (ETDEWEB)

Tobler, R.L.; Nishimura, A.; Yamamoto, J.

1996-08-01

Worldwide interest in austenitic alloys for structural applications in superconducting magnets has led to an expanded database for the 316-type stainless steels. We review the cryogenic mechanical properties of wrought, cast, and welded steels at liquid helium temperature (4 K), focussing on aspects of material behavior relevant to magnet design. Fracture mechanics parameters essential to structural reliability assessments are presented, including strength, toughness, and fatigue parameters that are critical for some component designs. (author). 105 refs.

Design-relevant mechanical properties of 316-type stainless steels for superconducting magnets

International Nuclear Information System (INIS)

Tobler, R.L.; Nishimura, A.; Yamamoto, J.

1996-08-01

Worldwide interest in austenitic alloys for structural applications in superconducting magnets has led to an expanded database for the 316-type stainless steels. We review the cryogenic mechanical properties of wrought, cast, and welded steels at liquid helium temperature (4 K), focussing on aspects of material behavior relevant to magnet design. Fracture mechanics parameters essential to structural reliability assessments are presented, including strength, toughness, and fatigue parameters that are critical for some component designs. (author). 105 refs

Superconductivity

International Nuclear Information System (INIS)

2007-01-01

During 2007, a large amount of the work was centred on the ITER project and related tasks. The activities based on low-temperature superconducting (LTS) materials included the manufacture and qualification of ITER full-size conductors under relevant operating conditions, the design of conductors and magnets for the JT-60SA tokamak and the manufacture of the conductors for the European dipole facility. A preliminary study was also performed to develop a new test facility at ENEA in order to test long-length ITER or DEMO full-size conductors. Several studies on different superconducting materials were also started to create a more complete database of superconductor properties, and also for use in magnet design. In this context, an extensive measurement campaign on transport and magnetic properties was carried out on commercially available NbTi strands. Work was started on characterising MgB 2 wire and bulk samples to optimise their performance. In addition, an intense experimental study was started to clarify the effect of mechanical loads on the transport properties of multi-filamentary Nb 3 Sn strands with twisted or untwisted superconducting filaments. The experimental activity on high-temperature superconducting (HTS) materials was mainly focussed on the development and characterisation of YBa 2 Cu 3 O 7-X (YBCO) based coated conductors. Several characteristics regarding YBCO deposition, current transport performance and tape manufacture were investigated. In the framework of chemical approaches for YBCO film growth, a new method, developed in collaboration with the Technical University of Cluj-Napoca (TUCN), Romania, was studied to obtain YBCO film via chemical solution deposition, which modifies the well-assessed metallic organic deposition trifluoroacetate (MOD-TFA) approach. The results are promising in terms of critical current and film thickness values. YBCO properties in films with artificially added pinning sites were characterised in collaboration with

Molybdenum-rhenium superconducting suspended nanostructures

Energy Technology Data Exchange (ETDEWEB)

Aziz, Mohsin; Christopher Hudson, David; Russo, Saverio [Centre for Graphene Science, College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter EX4 4QF (United Kingdom)

2014-06-09

Suspended superconducting nanostructures of MoRe 50%/50% by weight are fabricated employing commonly used fabrication steps in micro- and nano-meter scale devices followed by wet-etching with Hydro-fluoric acid of a SiO{sub 2} sacrificial layer. Suspended superconducting channels as narrow as 50 nm and length 3 μm have a critical temperature of ≈6.5 K, which can increase by 0.5 K upon annealing at 400 °C. A detailed study of the dependence of the superconducting critical current and critical temperature upon annealing and in devices with different channel widths reveals that desorption of contaminants is responsible for the improved superconducting properties. These findings pave the way for the development of superconducting electromechanical devices using standard fabrication techniques.

Superconducting phases of phosphorus hydride under pressure. Stabilization by mobile molecular hydrogen

Energy Technology Data Exchange (ETDEWEB)

Bi, Tiange; Miller, Daniel P.; Shamp, Andrew; Zurek, Eva [Department of Chemistry, State University of New York, Buffalo, NY (United States)

2017-08-14

At 80 GPa, phases with the PH{sub 2} stoichiometry, which are composed of simple cubic like phosphorus layers capped with hydrogen atoms and layers of H{sub 2} molecules, are predicted to be important species contributing to the recently observed superconductivity in compressed phosphine. The electron-phonon coupling in these phases results from the motions of the phosphorus atoms and the hydrogen atoms bound to them. The role of the mobile H{sub 2} layers is to decrease the Coulomb repulsion between the negatively charged hydrogen atoms capping the phosphorus layers. An insulating PH{sub 5} phase, the structure and bonding of which is reminiscent of diborane, is also predicted to be metastable at this pressure. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

The effect of citric and oxalic acid doping on the superconducting properties of MgB2

International Nuclear Information System (INIS)

Ojha, N; Singla, Rashmi; Varma, G D; Malik, V K; Bernhard, C

2009-01-01

In this paper we report the effect of carbon doping on the structural and superconducting properties of MgB 2 using citric and oxalic acids as carbon sources. The bulk polycrystalline samples have been synthesized via a standard solid state reaction route with composition MgB 2 +x wt% of citric and oxalic acids (x = 0, 5 and 10). The x-ray diffraction results reveal the formation of dominantly MgB 2 with only a small amount of impurity phase MgO and substitution of C at the B site of MgB 2 for both dopants. Improvements in the upper critical field (H C2 ), irreversibility field (H irr ) and high field (>2.5 T) critical current density (J C ) have been observed on C doping in the samples. The correlations between superconducting properties and structural characteristics of the samples are described and discussed in this paper.

Radiation considerations for superconducting fusion magnets

International Nuclear Information System (INIS)

Abdou, M.A.

1977-01-01

Radiation environment for the magnets is characterized for various conditions expected for tokamak power reactor operation. The radiation levels are translated into radiation effects using available experimental data. The impact of the tradeoffs in radiation shielding and the change in the properties of the superconducting magnets on reactor performance and economics is examined. It is shown that (1) superconducting magnets in fusion reactors will operate at much higher radiation level than was previously anticipated; (2) additional data on radiation damage is required to better accuracy than is presently available in order to accurately quantify the change in properties in the superconducting magnet components; and (3) there is a substantial penalty for increasing (or overestimating) the shielding requirements. A perspective of future tokamak power reactors is presented and questions relating to desirable magnetic field strength and selection of materials for superconducting magnets are briefly examined

Specific heat of holmium and YNi2B2C. Criticalbehaviour and superconducting properties

International Nuclear Information System (INIS)

Bekkali, Abdelhakim

2010-01-01

Object of the thesis is the study of the specific heat of holmium and YNi 2 B 2 C in the temperature ranges from 50 to 200 KI respectively from 380 mK to 20 K in magnetic fields up to 9 T. In the present thesis the criticalbehaviour of YNi 2 B 2 C and properties of the superconducting state of tne non-magnetic rare-earth nickel borocarbide YNi 2 B 2 C are studied by means of a self-developed measurement apparatur of the specific heat using the quasi-adiabatic heating-pulse method as well as of holmium by means of the relaxation method. In this thesis reliable statements about the critical exponents on monocrystalline holmium could be made. The study on holmium proves that the critical behaviour of the specific heats cannot be described in the framework of the predictions of the chiral universality classes. By means of measurements of the specific heat in this thesis could be confirmed that YNi 2 B 2 C is a multiband superconductor. The positive curvature of the boundary line below T c in the phase diagram yields a first hint to the many-band character of YNI 2 B 2 C. In the zero-field the electronic specific heat in the superconducting state c es (T) can be not explained in the framework of the pure BCS theory. At low temperatures a residual contribution by normally conducting electrons could be detected, which hints to a not completely opened energy gap. A possible explanation would be that a band (or several bands) with low charge-carrier concentration not contribute to the superconductivity. This result agrees with de Haas-van Alphen measurements on isostructural superconducting LuNi 2 B 2 C monocrystals, which suggest the many-band character of the superconductivity as well as a vanishing energy gap in one band. The fluctuation behaviour of the specific heat of YNi 2 B 2 C in the neighbourhood of the superconducting-normally conducting transition agrees well with that of the 3D-XY model. [de

Bulk Superconductivity and Disorder in Single Crystals of LaFePO

Energy Technology Data Exchange (ETDEWEB)

Analytis, James G.; Chu, Jiun-Haw; Erickson, Ann S.; Kucharczyk, Chris; /Stanford U., Appl. Phys. Dept.; Serafin, Alessandro; Carrington, Antony; /Bristol U.; Cox, Catherine; Kauzlarich, Susan M.; Hope, Hakon; /UC, Davis. Dept. Chem.

2010-02-15

We have studied the intrinsic normal and superconducting properties of the oxypnictide LaFePO. These samples exhibit bulk superconductivity and the evidence suggests that stoichiometric LaFePO is indeed superconducting, in contrast to other reports. We find that superconductivity is independent of the interplane residual resistivity {rho}{sub 0} and discuss the implications of this on the nature of the superconducting order parameter. Finally we find that, unlike T{sub c}, other properties in single-crystal LaFePO including the resistivity and magnetoresistance, can be very sensitive to disorder.

Status of RF superconductivity at Argonne

International Nuclear Information System (INIS)

Shepard, K.W.

1990-01-01

Development of a superconducting slow-wave structures began at Argonne National Laboratory (ANL) in 1971, and led to the first superconducting heavy-ion linac (ATLAS - the Argonne Tandem-Linac Accelerator System). The Physics Division at ANL has continued to develop superconducting RF technology for accelerating heavy-ions, with the result that the linac has been in an almost continuous process of upgrade and expansion. In 1987, the Engineering Physics Division at ANL began developing of superconducting RF components for the acceleration of high-brightness proton and deuterium beams. The two divisions collaborate in work on several applications of RF superconductivity, and also in work to develop the technology generally. The present report briefly describes major features of the superconducting heavy-ion linac (very-low-velocity superconducting linac, positive ion injector), proton accelerating structures (superconducting resonant cavities for acceleration of high-current proton and deuteron beams, RF properties of oxide superconductors), and future work. Both divisions expect to continue a variety of studies, frequently in collaboration, to advance the basic technology of RF superconductivity. (N.K.)

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.

Competition between disorder and exchange splitting in superconducting ZrZn sub 2

CERN Document Server

Powell, B J; Györffy, B L

2003-01-01

We propose a simple picture for the occurrence of superconductivity and the pressure dependence of the superconducting critical temperature, T sub S sub C , in ZrZn sub 2. According to our hypothesis the pairing potential is independent of pressure, but the exchange splitting, E sub x sub c , leads to a pressure dependence in the (spin dependent) density of states at the Fermi level, D subsigma (epsilon sub F). Assuming p-wave pairing T sub S sub C is dependent on D subsigma (epsilon sub F) which ensures that, in the absence of non-magnetic impurities, T sub S sub C decreases as pressure is applied until it reaches a minimum in the paramagnetic state. Disorder reduces this minimum to zero, this gives the illusion that the superconductivity disappears at the same pressure as ferromagnetism does. (letter to the editor)

Superconducting materials

International Nuclear Information System (INIS)

Ruvalds, J.

1990-01-01

This report discusses the following topics: Fermi liquid nesting in high temperature superconductors; optical properties of high temperature superconductors; Hall effect in superconducting La 2-x Sr x CuO 4 ; source of high transition temperatures; and prospects for new superconductors

Pressure-induced Td to 1T′ structural phase transition in WTe{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Zhou, Yonghui [High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei 230031 (China); Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); Chen, Xuliang, E-mail: xlchen@hmfl.ac.cn, E-mail: zryang@issp.ac.cn; Zhang, Ranran; Wang, Xuefei; An, Chao; Zhou, Ying [High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei 230031 (China); Li, Nana [Center for High Pressure Science and Technology Advanced Research, Shanghai 201203 (China); Pan, Xingchen [National Laboratory of Solid State Microstructures, College of Physics, Nanjing University, Nanjing 210093 (China); Song, Fengqi; Wang, Baigeng [National Laboratory of Solid State Microstructures, College of Physics, Nanjing University, Nanjing 210093 (China); Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China); Yang, Wenge [Center for High Pressure Science and Technology Advanced Research, Shanghai 201203 (China); High Pressure Synergetic Consortium, Geophysical Laboratory, Carnegie Institution of Washington, Argonne, IL 60439 (United States); Yang, Zhaorong, E-mail: xlchen@hmfl.ac.cn, E-mail: zryang@issp.ac.cn [High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei 230031 (China); Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China); Zhang, Yuheng [High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei 230031 (China); Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China)

2016-07-15

WTe{sub 2} is provoking immense interest owing to its extraordinary properties, such as large positive magnetoresistance, pressure-driven superconductivity and possible type-II Weyl semimetal state. Here we report results of high-pressure synchrotron X-ray diffraction (XRD), Raman and electrical transport measurements on WTe{sub 2}. Both the XRD and Raman results reveal a structural transition upon compression, starting at 6.0 GPa and completing above 15.5 GPa. We have determined that the high-pressure lattice symmetry is monoclinic 1T′ with space group of P2{sub 1}/m. This transition is related to a lateral sliding of adjacent Te-W-Te layers and results in a collapse of the unit cell volume by ∼20.5%. The structural transition also casts a pressure range with the broadened superconducting transition, where the zero resistance disappears.

A study on the superconducting properties of YBa2Cu9-xNbxOy thin films

International Nuclear Information System (INIS)

Srinivas, S.; Bhatnagar, A.K.; Pinto, R.

1994-01-01

Effect of niobium substitution at the copper site in YBa 2 Cu 9 O 7-x was studied in thin film form. The films were deposited by laser ablation technique using the targets of the YBa 2 Cu 3-x Nb x O 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 9 substrates. Films were characterized by XRD, resistivity, I-V and J 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 σ A/cm 2 and for 0.05 Nb concentration it was 3.2x10 σ A/cm 2 at 77K. However, degradation of the superconducting properties, with the increase of x ≥ 0.1 Nb concentration and drastic suppression and complete loss of superconductivity was noticed for x ≥ 0.4. The growth of impurity phase YBa 2 NbO 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

Synthesis, properties and space applications of chemically precipitated YBa/sub 2/Cu/sub 3/O/sub 7-x/ superconducting powders

International Nuclear Information System (INIS)

Trivedi, A.; Sundahl, R.C.; Olson, W.L.; Welsh, L.B.; Polak, A.J.; Dolgin, B.P.; Barder, T.J.; Karasek, K.R.; Parker, C.A.

1988-01-01

Processing properties of and chemically precipitated YBa/sub 2/Cu/sub 3/O/sub 7-x/ powders were evaluated. The authors have successfully developed a method for precipitating stoichiometric oxalate precursors for YBa/sub 2/Cu/sub 3/O/sub 7-x/ powders. Precipitation and calcination conditions were found to dramatically impact upon key powder characteristics such as particle size, morphology, phase composition and microscopic homogeneity. Four space applications were identified: a superconducting motor/generator, a magnetic bearing, an electromagnetic coupling, and a motor commutator. The primary device, a motor, would make use of superconducting windings and a superconducting flux bottle to improve efficiency

ASC 84: applied superconductivity conference. Final program and abstracts

International Nuclear Information System (INIS)

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

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)

Structural and Transport Properties of the Weyl Semimetal NbAs at High Pressure

International Nuclear Information System (INIS)

Zhang Jun; Liu Feng-Liang; Dong Jin-Kui; Xu Yang; Li Shi-Yan; Li Na-Na; Yang Wen-Ge

2015-01-01

We perform a series of high-pressure synchrotron x-ray diffraction (XRD) and resistance measurements on the Weyl semimetal NbAs. The crystal structure remains stable up to 26 GPa according to the powder XRD data. The resistance of NbAs single crystal increases monotonically with pressure at low temperature. Up to 20 GPa, no superconducting transition is observed down to 0.3 K. These results show that the Weyl semimetal phase is robust in NbAs, and applying pressure may not be a good way to obtain a topological superconductor from Weyl semimetal NbAs. (paper)

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.

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.

Transmission line properties of long strings of superconducting magnets

International Nuclear Information System (INIS)

Shafer, R.E.

1980-09-01

The purpose of this paper is to discuss the electrical characteristics of a long string of superconducting magnets, such as in a superconducting storage ring or accelerator. As the magnets have a shunt capacitance to ground as well as a series inductance, travelling waves can propagate along the string, as in a transmission line. As the string is of finite length, standing waves can also exist. In accelerator quality superconducting magnets, considerable effort has been devoted to minimizing ac losses, the net result being that the magnet string has a high Q precisely at the frequencies which are important for the standing and travelling waves. The magnitude of these effects are estimated, and the solution to be used at Fermilab will be discussed

Structural and physical properties of the NaxCoO2·yH2O superconducting system

International Nuclear Information System (INIS)

Shi, Y G; Li, J Q; Yu, H C; Zhou, Y Q; Zhang, H R; Dong, C

2004-01-01

The structural features and physical properties of Na x CoO 2 and Na x CoO 2 ·yH 2 O materials have been investigated. The Na x CoO 2 -yH 2 O samples, in general, undergo superconducting transitions at around 3.5 K. Energy dispersive x-ray analyses suggest that our samples have average compositions of Na 0.65 CoO 2 for the parent compounds and Na 0.26 CoO 2 ·yH 2 O for the superconducting oxyhydrates. Transmission electron microscopy observations reveal a new superstructure with wave vector q = in the parent material. This superstructure becomes very weak in the superconducting samples. Electron energy loss spectra analyses show that the Co ions have valence states of around +3.3 in Na 0.65 CoO 2 and around +3.7 in Na 0.26 CoO 2 -yH 2 O

Ac superconducting articles and a method for their manufacture

International Nuclear Information System (INIS)

Meyerhoff, R.W.

1975-01-01

A novel ac superconducting article is described comprising a composite structure having a superconducting surface along with a high thermally conductive material wherein the superconducting surface has the desired physical properties, geometrical shape and surface finish produced by the steps of depositing a superconducting layer upon a substrate having a predetermined surface finish and shape which conforms to that of the desired superconducting article, depositing a supporting layer of material on the superconducting layer and removing the substrate, the surface of the superconductor being a replica of the substrate surface. (auth)

Bipolar superconductivity

International Nuclear Information System (INIS)

Pankratov, S.G.

1987-01-01

A model of bipolaron superconductivity suggested by Soviet scientist Alexandrov A.S. and French scientist Ranninger is presentes in a popular way. It is noted that the bipolaron theory gives a good explanation of certain properties of new superconductors, high critical temperature, in particular

Hydrostatic pressure dependence of the superconducting transition temperature of HgBa2CaCu2O6+δ and HgBa2Ca2Cu3O8+δ

International Nuclear Information System (INIS)

Klehe, A.K.; Schilling, J.S.

1994-02-01

The dependence of the superconducting transition temperature T c (P) on purely hydrostatic pressure to 0.9 GPa has been determined in ac susceptibility studies in a He-gas pressure system for optimally doped ceramic samples of HgBa 2 CaCu 2 O 6+δ and HgBa 2 Ca 2 Cu 3 O 8+δ with superconducting transitions at T c (0) ≅ 126.6 K and 133.9 K, respectively. T c increases reversibly under hydrostatic pressure at the rates, d T c /dP ≅ +1.80 ± 0.06 K/GPa and +1.71 ± 0.05 K/GPa, respectively. Within experimental error, these values are the same as found previously for optimally doped single-layered HgBa 2 CuO 4+δ , where d T c /dP ≅ +1.72 ± 0.05 K/GPa. Remarkably, the logarithmic volume derivative of T c is nearly identical for all three compounds, dln T c /dlnV ≅ -1.20 ± 0.05, even though the bulk modulus differs by more than 30%. This provides strong evidence that a common mechanism is responsible for the pressure dependence of the superconducting state in all three compounds

On possibility of superconductivity in SnSb: A first principle study

Energy Technology Data Exchange (ETDEWEB)

Dabhi, Shweta D. [Department of Physics, M. K. Bhavnagar University, Bhavnagar 364001 (India); Shrivastava, Deepika [Department of Physics, Barkatullah University, Bhopal 462026 (India); Jha, Prafulla K., E-mail: prafullaj@yahoo.com [Department of Physics, Faculty of Science, The M. S. University of Baroda, Vadodara 390002 (India); Sanyal, Sankar P. [Department of Physics, Barkatullah University, Bhopal 462026 (India)

2016-09-15

Highlights: • Superconducting property of SnSb is predicted by ab-initio calculations. • Electronic properties of SnSb in RS phase shows metallic behaviour similar to SnAs. • Phonon dispersion confirms the dynamical stability of SnSb in RS phase. • Superconducting transition temperature is 3.1 K, slightly lower than that of SnAs. • Calculated thermodynamic properties are also reported. - Abstract: The electronic, phonon structure and superconducting properties of tin antimonide (SnSb) in rock-salt (RS) structure are calculated using first-principles density functional theory. The electronic band structure and density of states show metallic behavior. The phonon frequencies are positive throughout the Brillouin zone in rock-salt structure indicating its stability in that phase. Superconductivity of SnSb in RS phase is discussed in detail by calculating phonon linewidths, Eliashberg spectral function, electron-phonon coupling constant and superconducting transition temperature. SnSb is found to have a slightly lower T{sub C} (3.1 K), as compared to SnAs.

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.

Superconducting nanostructured materials

International Nuclear Information System (INIS)

Metlushko, V.

1998-01-01

Within the last year it has been realized that the remarkable properties of superconducting thin films containing a periodic array of defects (such as sub-micron sized holes) offer a new route for developing a novel superconducting materials based on precise control of microstructure by modern photolithography. A superconductor is a material which, when cooled below a certain temperature, loses all resistance to electricity. This means that superconducting materials can carry large electrical currents without any energy loss--but there are limits to how much current can flow before superconductivity is destroyed. The current at which superconductivity breaks down is called the critical current. The value of the critical current is determined by the balance of Lorentz forces and pinning forces acting on the flux lines in the superconductor. Lorentz forces proportional to the current flow tend to drive the flux lines into motion, which dissipates energy and destroys zero resistance. Pinning forces created by isolated defects in the microstructure oppose flux line motion and increase the critical current. Many kinds of artificial pinning centers have been proposed and developed to increase critical current performance, ranging from dispersal of small non-superconducting second phases to creation of defects by proton, neutron or heavy ion irradiation. In all of these methods, the pinning centers are randomly distributed over the superconducting material, causing them to operate well below their maximum efficiency. We are overcome this drawback by creating pinning centers in aperiodic lattice (see Fig 1) so that each pin site interacts strongly with only one or a few flux lines

Diatomic substitutionals in superconducting Nb{sub (1-x)}B{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Farrell, H.H. [Idaho National Laboratory, Materials Science Department, 2525 N. Freemont Ave., MS-2211, P.O. Box 1625, Idaho Falls, ID 83415-2211 (United States)]. E-mail: Helen.Farrell@inl.gov; LaViolette, Randall A. [Idaho National Laboratory, Materials Science Department, 2525 N. Freemont Ave., MS-2211, P.O. Box 1625, Idaho Falls, ID 83415-2211 (United States); Lillo, T.M. [Idaho National Laboratory, Materials Science Department, 2525 N. Freemont Ave., MS-2211, P.O. Box 1625, Idaho Falls, ID 83415-2211 (United States)

2006-11-01

Using first-principles, density functional theory calculations, we have shown that the increase in superconducting critical temperature to above 9 K experimentally observed for B-rich, off-stoichiometry NbB{sub 2} material is associated with the formation of B-dimers on Nb sites rather than with the formation of Nb vacancies, as previously proposed. Our calculations show that certain of these B-dimer configurations have lower binding energies than do the vacancy structures. This result is pressure independent in the range between 0 and 10 GPa, and above. Further, the dimer-containing materials have a higher electronic density of states at the Fermi level than do the vacancy structures. Finally, the presence of B-dimers results in the splitting off of phonon normal modes. These last two factors are relevant to the improved superconducting properties.

Effects of irradiation and mechanical stress on the superconducting properties of candidate magnet conductors

International Nuclear Information System (INIS)

Snead, C.L. Jr.; Luhman, T.

1980-01-01

The effects of radiation damage on the superconducting critical properties of candidate magnet materials are reviewed. Neutron, and charged-particle irradiation results are covered. The discussion is restricted to effects in NbTi and the A15-compound superconductors. The utility of these conductors in radiation fields is first explored by defining the magnitude of critical-property changes with the fluence of various irradiating particles. The physical mechanisms that couple the irradiation defects to the observed critical-property changes are discussed. Annealing/recovery data on irradiated materials are included where they pertain to the understanding of the physical mechanisms involved, and thereby to the desirability of magnet annealing in actual operating circumstances

Evaluation of the cryogenic mechanical properties of the insulation material for ITER Feeder superconducting joint

Science.gov (United States)

Wu, Zhixiong; Huang, Rongjin; Huang, ChuanJun; Yang, Yanfang; Huang, Xiongyi; Li, Laifeng

2017-12-01

The Glass-fiber reinforced plastic (GFRP) fabricated by the vacuum bag process was selected as the high voltage electrical insulation and mechanical support for the superconducting joints and the current leads for the ITER Feeder system. To evaluate the cryogenic mechanical properties of the GFRP, the mechanical properties such as the short beam strength (SBS), the tensile strength and the fatigue fracture strength after 30,000 cycles, were measured at 77K in this study. The results demonstrated that the GFRP met the design requirements of ITER.

Superconducting accelerator magnet design

International Nuclear Information System (INIS)

Wolff, S.

1994-01-01

Superconducting dipoles, quadrupoles and correction magnets are necessary to achieve the high magnetic fields required for big accelerators presently in construction or in the design phase. Different designs of superconducting accelerator magnets are described and the designs chosen at the big accelerator laboratories are presented. The most frequently used cosθ coil configuration is discussed in detail. Approaches for calculating the magnetic field quality including coil end fields are presented. Design details of the cables, coils, mechanical structures, yokes, helium vessels and cryostats including thermal radiation shields and support structures used in superconducting magnets are given. Necessary material properties are mentioned. Finally, the main results of magnetic field measurements and quench statistics are presented. (orig.)

Spin, Vibrations and Radiation in Superconducting Junctions

NARCIS (Netherlands)

Padurariu, C.

2013-01-01

This thesis presents the theoretical study of superconducting transport in several devices based on superconducting junctions. The important feature of these devices is that the transport properties of the junction are modified by the interaction with another physical system integrated in the

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.

Superconducting and hybrid systems for magnetic field shielding

International Nuclear Information System (INIS)

Gozzelino, L; Gerbaldo, R; Ghigo, G; Laviano, F; Truccato, M; Agostino, A

2016-01-01

In this paper we investigate and compare the shielding properties of superconducting and hybrid superconducting/ferromagnetic systems, consisting of cylindrical cups with an aspect ratio of height/radius close to unity. First, we reproduced, by finite-element calculations, the induction magnetic field values measured along the symmetry axis in a superconducting (MgB 2 ) and in a hybrid configuration (MgB 2 /Fe) as a function of the applied magnetic field and of the position. The calculations are carried out using the vector potential formalism, taking into account simultaneously the non-linear properties of both the superconducting and the ferromagnetic material. On the basis of the good agreement between the experimental and the computed data we apply the same model to study the influence of the geometric parameters of the ferromagnetic cup as well as of the thickness of the lateral gap between the two cups on the shielding properties of the superconducting cup. The results show that in the considered non-ideal geometry, where the edge effect in the flux penetration cannot be disregarded, the superconducting shield is always the most efficient solution at low magnetic fields. However, a partial recovery of the shielding capability of the hybrid configuration occurs if a mismatch in the open edges of the two cups is considered. In contrast, at high magnetic fields the hybrid configurations are always the most effective. In particular, the highest shielding factor was found for solutions with the ferromagnetic cup protruding over the superconducting one. (paper)

Electronic properties of newly-discovered doped semiconductors. Superconductivity in diamond and transport properties of RuIn{sub 3}; Elektronische Eigenschaften neuer dotierter Halbleiter. Supraleitung im Diamant und Transporteigenschaften von RuIn{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Bogdanov, D.A.

2006-08-01

The properties of the boron-doped diamond are sensitive to the boron concentration. A semiconducting behaviour occurs at low boron concentration and transport properties are given by a hopping-mechanism. The conductivity increases for higher boron concentration. The Mott metal to insulator transition takes place at a critical boron concentration. In the metallic phase superconductivity is observed. The critical temperatures of the superconducting transition are below 3 K. In this work, the influence of boron to the electronic properties, like conductivity and magneto resistance, was studied in the vicinity of the metal to insulator transition point. The superconducting properties (critical temperature, upper critical field) were studied down to 50 mK and compared to the conventional theory of the electron-phonon coupled superconductors. The properties of polycrystalline RuIn{sub 3} are reported in few publications to be metallic. In this work single crystals of this material were grown and analysed. We observe a semiconducting behaviour with an intrinsic gap of 0.4-0.5 eV. The previously reported metallic behaviour could be interpreted in this work as influence of the elementary indium in the samples. The measurements of the specific heat at low temperatures and LDA band structure calculations confirm the semiconducting properties and the value of the semiconducting gap. (orig.)

Dependences on RE of superconducting properties of transition metal co-doped (Ca, RE)FeAs_2 with RE = La–Gd

International Nuclear Information System (INIS)

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

2015-01-01

Highlights: • We synthesized Co or Ni co-doped (Ca, RE)FeAs_2 with RE = La–Gd. • Co or Ni co-doping improved superconducting properties of all (Ca, RE)FeAs_2 samples. • T_c of (Ca, RE)FeAs_2 decreased with decreasing ionic radii of RE"3"+. • Eu doped samples showed exceptionally low T_c and long interlayer distance. • Long interlayer distance of Eu doped samples suggested co-existence of Eu"2"+ and Eu"3"+. - Abstract: Dependence of superconducting properties of (Ca, RE)(Fe, TM)As_2 [(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. T_c of Co-co-doped samples decreased from 38 K for RE = La to 29 K for RE = Gd with decreasing ionic radii of RE"3"+. However, Co-co-doped (Ca, Eu)112 showed exceptionally low T_c = 21 K probably due to the co-existence of Eu"3"+ and Eu"2"+ suggested by longer interlayer distance d_F_e_–_F_e of (Ca, Eu)112 than other (Ca, RE)112.

Liquid phase sintered superconducting cermet

International Nuclear Information System (INIS)

Ray, S.P.

1990-01-01

This patent describes a method of making a superconducting cermet having superconducting properties with improved bulk density, low porosity and in situ stabilization. It comprises: forming a structure of a superconducting ceramic material having the formula RM 2 Cu 3 O (6.5 + x) wherein R is one or more rare earth elements capable of reacting to form a superconducting ceramic, M is one or more alkaline earth metal elements selected from barium and strontium capable of reacting to form a superconducting ceramic, x is greater than 0 and less than 0.5; and a precious metal compound in solid form selected from the class consisting of oxides, sulfides and halides of silver; and liquid phase sintering the mixture at a temperature wherein the precious metal of the precious metal compound is molten and below the melting point of the ceramic material. The liquid phase sintering is carried out for a time less than 36 hours but sufficient to improve the bulk density of the cermet

Low-velocity superconducting accelerating structures

International Nuclear Information System (INIS)

Delayen, J.R.

1990-01-01

The present paper reviews the status of RF superconductivity as applied to low-velocity accelerating properties. Heavy-ion accelerators must accelerate efficiently particles which travel at a velocity much smaller than that of light particles, whose velocity changes along accelerator, and also different particles which have different velocity profiles. Heavy-ion superconducting accelerators operate at frequencies which are lower than high-energy superconducting accelerators. The present paper first discusses the basic features of heavy-ion superconducting structures and linacs. Design choices are then addressed focusing on structure geometry, materials, frequency, phase control, and focusing. The report also gives an outline of the status of superconducting booster projects currently under way at the Argonne National Laboratory, SUNY Stony Brook, Weizmann Institute, University of Washington, Florida State, Saclay, Kansas State, Daresbury, Japanese Atomic Energy Research Institute, Legnaro, Bombay, Sao Paulo, ANU (Canberra), and Munich. Recent developments and future prospects are also described. (N.K.) 68 refs

Pressure-induced Td to 1T' structural phase transition in WTe₂

Energy Technology Data Exchange (ETDEWEB)

Zhou, Yonghui; Chen, Xuliang; Li, Nana; Zhang, Ranran; Wang, Xuefei; An, Chao; Zhou, Ying; Pan, Xingchen; Song, Fengqi; Wang, Baigeng; Yang, Wenge; Yang, Zhaorong; Zhang, Yuheng (CIW); (Chinese Aca. Sci.); (CHPSTAR- China); (Nanjing)

2016-11-21

WTe₂ is provoking immense interest owing to its extraordinary properties, such as large positive magnetoresistance, pressure-driven superconductivity and possible type-II Weyl semimetal state. Here we report results of high-pressure synchrotron X-ray diffraction (XRD), Raman and electrical transport measurements on WTe₂. Both the XRD and Raman results reveal a structural transition upon compression, starting at 6.0 GPa and completing above 15.5 GPa. We have determined that the high-pressure lattice symmetry is monoclinic 1T' with space group of P21/m. This transition is related to a lateral sliding of adjacent Te-W-Te layers and results in a collapse of the unit cell volume by ~20.5%. The structural transition also casts a pressure range with the broadened superconducting transition, where the zero resistance disappears.

Physical Properties of Niobium and Specifications for Fabrication of Superconducting Cavities

International Nuclear Information System (INIS)

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

2011-01-01

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.

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.

Superconductivity in the elements, alloys and simple compounds

Energy Technology Data Exchange (ETDEWEB)

Webb, G.W. [Department of Physics, University of California, San Diego, La Jolla, CA 92093-0319 (United States); Marsiglio, F. [Department of Physics, University of Alberta, Edmonton, Alberta, Canada T6G 2E1 (Canada); Hirsch, J.E., E-mail: jhirsch@ucsd.edu [Department of Physics, University of California, San Diego, La Jolla, CA 92093-0319 (United States)

2015-07-15

Highlights: • A review of superconductivity in elements, alloys and simple compounds is given. • These materials are believed to be described by BCS–Eliashberg theory. • The McMillan–Rowell inversion process is described. • Calculations of Tc’s from first principles are surveyed. • Other criteria beyond BCS to characterize these superconductors are discussed. - Abstract: We give a brief review of superconductivity at ambient pressure in elements, alloys, and simple three-dimensional compounds. Historically these were the first superconducting materials studied, and based on the experimental knowledge gained from them the BCS theory of superconductivity was developed in 1957. Extended to include the effect of phonon retardation, the theory is believed to describe the subset of superconducting materials known as ‘conventional superconductors’, where superconductivity is caused by the electron–phonon interaction. These include the elements, alloys and simple compounds discussed in this article and several other classes of materials discussed in other articles in this Special Issue.

Superconductivity in the elements, alloys and simple compounds

International Nuclear Information System (INIS)

Webb, G.W.; Marsiglio, F.; Hirsch, J.E.

2015-01-01

Highlights: • A review of superconductivity in elements, alloys and simple compounds is given. • These materials are believed to be described by BCS–Eliashberg theory. • The McMillan–Rowell inversion process is described. • Calculations of Tc’s from first principles are surveyed. • Other criteria beyond BCS to characterize these superconductors are discussed. - Abstract: We give a brief review of superconductivity at ambient pressure in elements, alloys, and simple three-dimensional compounds. Historically these were the first superconducting materials studied, and based on the experimental knowledge gained from them the BCS theory of superconductivity was developed in 1957. Extended to include the effect of phonon retardation, the theory is believed to describe the subset of superconducting materials known as ‘conventional superconductors’, where superconductivity is caused by the electron–phonon interaction. These include the elements, alloys and simple compounds discussed in this article and several other classes of materials discussed in other articles in this Special Issue

Application of superconductivity in cyclotron construction

International Nuclear Information System (INIS)

Blosser, H.G.

1982-01-01

This paper reviews major concepts and design features of the new class of cyclotrons which use superconducting coils to provide main magnet excitation. The discussion begins with a brief historical review tracing the evolution of these ''superconducting'' cyclotrons and the impact of this application of superconductivity in pushing back traditional cyclotron construction limits. This is followed by a review of the principal phenomena which come into play to set new limits on the operating regime, and the nature of these limits, some of which arise from orbit properties and some of which result from construction intricacies in the coil and in the rf system. Conclusions anticipate a future widely encompassing role in the application of superconductivity to cyclotron

Fabrication and characterizations of high-Tc superconducting ceramic/polymer 0--3 composites

International Nuclear Information System (INIS)

Du, J.; Unsworth, J.

1994-01-01

High-T c superconducting ceramic YBa 2 Cu 3 O 7-x /thermosetting plastic 0--3 composites were fabricated. The structure, physical property, magnetic susceptibility, levitation, and mechanical strength of the composites were accessed. The influence of filler content on these properties was also studied. Although the 0--3 composites lack an electrical superconducting path through materials, the intrinsic diamagnetic properties were preserved. The magnetic superconducting transition temperature was not degraded. The values of magnetic susceptibility and levitation force for the composites were basically proportional to the actual volume fraction of superconducting filler. These new composite materials are most suitable for the applications in levitating vehicles and mechanical bearings

Sequential structural and antiferromagnetic transitions in BaFe2Se3 under pressure

Science.gov (United States)

Zhang, Yang; Lin, Ling-Fang; Zhang, Jun-Jie; Dagotto, Elbio; Dong, Shuai

2018-01-01

The discovery of superconductivity in the two-leg ladder compound BaFe2S3 has established the 123-type iron chalcogenides as a novel and interesting subgroup of the iron-based superconductor family. However, in this 123 series, BaFe2Se3 is an exceptional member, with a magnetic order and crystalline structure different from all others. Recently, an exciting experiment reported the emergence of superconductivity in BaFe2Se3 at high pressure [J. Ying et al., Phys. Rev. B 95, 241109(R) (2017), 10.1103/PhysRevB.95.241109]. In this paper, we report a first-principles study of BaFe2Se3 . Our analysis unveils a variety of qualitative differences between BaFe2S3 and BaFe2Se3 , including in the latter an unexpected chain of transitions with increasing pressure. First, by gradually reducing the tilting angle of iron ladders, the crystalline structure smoothly transforms from P n m a to C m c m at ˜6 GPa. Second, the system becomes metallic at 10.4 GPa. Third, its unique ambient-pressure Block antiferromagnetic ground state is replaced by the more common stripe (so-called CX-type) antiferromagnetic order at ˜12 GPa, the same magnetic state as the 123-S ladder. This transition is found at a pressure very similar to the experimental superconducting transition. Finally, all magnetic moments vanish at 30 GPa. This reported theoretical diagram of the complete phase evolution is important because of the technical challenges to capture many physical properties in high-pressure experiments. The information obtained in our calculations suggests different characteristics for superconductivity in BaFe2Se3 and BaFe2S3 : in 123-S pairing occurs when magnetic moments vanish, while in 123-Se the transition region from Block- to CX-type magnetism appears to catalyze superconductivity. Finally, an additional superconducting dome above ˜30 GPa is expected to occur.

Dielectric properties of glasses prepared by quenching melts of superconducting Bi-Ca-Sr-Cu-O cuprates

Energy Technology Data Exchange (ETDEWEB)

Varma, K. B. R.; Subbanna, G. N.; Ramakrishnan, T. V.; Rao, C. N. R.

1989-07-03

Glasses obtained from quenching melts of superconducting bismuth cuprates of the formula Bi/sub 2/(Ca,Sr)/sub /ital n/+1/Cu/sub /ital n//O/sub 2/ital n/+4/ with /ital n/=1 and 3 exhibit novel dielectric properties. They possess relatively high dielectric constants as well as high electrical conductivity. The novel dielectric properties of these cuprate glasses are likely to be of electronic origin. They exhibit a weak microwave absorption due to the presence of microcrystallites.

Superconducting thin films of Bi-Sr-Ca-Cu-O by laser ablation

International Nuclear Information System (INIS)

Bedekar, M.M.

1992-01-01

The discovery of a new class of copper oxide superconductors has led to the development of three major systems that exhibit superconducting properties. The Bi-Sr-Ca-Cu-O superconductors offer intrinsic advantages due to the high T c , chemical inertness and tolerance for a range of compositions. However, thin film research on these materials has progressed more slowly than the other cuprate systems. This dissertation examines the film growth, by laser ablation, of the Bi-Sr-Ca-Cu-O superconductors and the effect of the deposition parameters such as the laser target interaction, substrate temperature, target to substrate distance, deposition and cooling pressure, target type and processing and the substrate type. CO 2 laser ablation was shown to give rise to a non-stoichiometric material transfer due to the low fluences and long pulse lengths. In situ superconducting thin films with T c(0) 's of 76 K could be deposited using the KrF laser at substrate temperatures of 5 degrees C to 20 degrees C below phases. Lower temperatures gave rise to a mixture of 2201 and glassy phases. An increase in the target to substrate distance led to a deterioration of the electrical and structural properties of the films due to a decrease in the energy for film formation. A maximum in T c(0) was observed at 450 mtorr as the deposition pressure was varied between 200 to 700 mtorr. Optimum oxygen incorporation could be achieved by cooling the films in high oxygen pressures and the best films were obtained with 700 torr cooling pressure. The oxygen deficiency of the hot pressed targets led to inferior properties compared to the conventionally sintered targets. The microwave surface resistance of the films measured at 35 GHz showed an onset at 80 K and dropped below that of copper at 30 K. The study of the laser ablation process in this system revealed the presence of a stoichiometric forward directed component and a diffuse evaporation component

Ballistic superconductivity in semiconductor nanowires

Science.gov (United States)

Zhang, Hao; Gül, Önder; Conesa-Boj, Sonia; Nowak, Michał P.; Wimmer, Michael; Zuo, Kun; Mourik, Vincent; de Vries, Folkert K.; van Veen, Jasper; de Moor, Michiel W. A.; Bommer, Jouri D. S.; van Woerkom, David J.; Car, Diana; Plissard, Sébastien R; Bakkers, Erik P.A.M.; Quintero-Pérez, Marina; Cassidy, Maja C.; Koelling, Sebastian; Goswami, Srijit; Watanabe, Kenji; Taniguchi, Takashi; Kouwenhoven, Leo P.

2017-01-01

Semiconductor nanowires have opened new research avenues in quantum transport owing to their confined geometry and electrostatic tunability. They have offered an exceptional testbed for superconductivity, leading to the realization of hybrid systems combining the macroscopic quantum properties of superconductors with the possibility to control charges down to a single electron. These advances brought semiconductor nanowires to the forefront of efforts to realize topological superconductivity and Majorana modes. A prime challenge to benefit from the topological properties of Majoranas is to reduce the disorder in hybrid nanowire devices. Here we show ballistic superconductivity in InSb semiconductor nanowires. Our structural and chemical analyses demonstrate a high-quality interface between the nanowire and a NbTiN superconductor that enables ballistic transport. This is manifested by a quantized conductance for normal carriers, a strongly enhanced conductance for Andreev-reflecting carriers, and an induced hard gap with a significantly reduced density of states. These results pave the way for disorder-free Majorana devices. PMID:28681843

Superconductivity and magnet technology

International Nuclear Information System (INIS)

Lubell, M.S.

1975-01-01

The background theory of superconducting behavior is reviewed. Three parameters that characterize superconducting materials with values of commercial materials as examples are discussed. More than 1000 compounds and alloy systems and 26 elements are known to exhibit superconducting properties under normal conditions at very low temperatures. A wide variety of crystal structures are represented among the known superconductors. The most important ones do seem to have cubic symmetry such as the body-centered cubic (NbZr and NbTi), face-centered cubic (NbN), and the A15 or β-tungsten structures (Nb 3 Sn), V 3 Ga, Nb 3 Ge, Nb 3 Al, and V 3 Si). Attempts to understand some of the particular phenomena associated with superconductors as a necessary prelude to constructing superconducting magnets are discussed by the author. The origin of degradation is briefly discussed and methods to stabilize magnets are illustrated. The results of Oak Ridge National Laboratory design studies of toroidal magnet systems for fusion reactors are described

MICROSTRUCTURE OF SUPERCONDUCTING MGB(2).

Energy Technology Data Exchange (ETDEWEB)

ZHU,Y.; LI,Q.; WU,L.; VOLKOV,V.; GU,G.; MOODENBAUGH,A.R.

2001-07-12

Recently, Akimitsu and co-workers [1] discovered superconductivity at 39 K in the intermetallic compound MgB{sub 2}. This discovery provides a new perspective on the mechanism for superconductivity. More specifically, it opens up possibilities for investigation of structure/properties in a new class of materials. With the exceptions of the cuprate and C{sub 60} families of compounds, MgB{sub 2} possesses the highest superconducting transition temperature T{sub c}. Its superconductivity appears to follow the BCS theory, apparently being mediated by electron-phonon coupling. The coherence length of MgB{sub 2} is reported to be longer than that of the cuprates [2]. In contrast to the cuprates, grain boundaries are strongly coupled and current density is determined by flux pinning [2,3]. Presently, samples of MgB{sub 2} commonly display inhomogeneity and porosity on the nanoscale, and are untextured. In spite of these obstacles, magnetization and transport measurements show that polycrystalline samples may carry large current densities circulating across many grains [3,4]. Very high values of critical current densities and critical fields have been recently observed in thin films [5,6]. These attributes suggest possible large scale and electronic applications. The underlying microstructure can be intriguing, both in terms of basic science and in applied areas. Subsequent to the discovery, many papers were published [1-13], most dealing with synthesis, physical properties, and theory. There have yet been few studies of microstructure and structural defects [11, 14]. A thorough understanding of practical superconducting properties can only be developed after an understanding of microstructure is gained. In this work we review transmission electron microscopy (TEM) studies of sintered MgB{sub 2} pellets [14]. Structural defects, including second phase particles, dislocations, stacking faults, and grain boundaries, are analyzed using electron diffraction, electron

Refinement of Crystalline Boron and the Superconducting Properties of MgB2 by Attrition Ball Milling

International Nuclear Information System (INIS)

Lee, J. H.; Shin, S. Y.; Park, H. W.; Jun, B. H.; Kim, C. J.

2008-01-01

We report refinement of crystalline boron by an attrition ball milling system and the superconducting properties of the MgB 2 pellets prepared from the refined boron. In this work, we have conducted the ball milling with only crystalline boron powder, in order to improve homogeneity and control the grain size of the MgB 2 that is formed from it. We observed that the crystalline responses in the ball-milled boron became broader and weaker when the ball-milling time was further increased. On the other hand, the B 2 O 3 peak became stronger in the powders, resulting in an increase in the amount of MgO within the MgB 2 volume. The main reason for this is a greater oxygen uptake. From the perspective of the superconducting properties, however, the sample prepared from boron that was ball milled for 5 hours showed an improvement of critical current density (J c ), even with increased MgO phase, under an external magnetic field at 5 and 20 K.

The filled skutterudite PrOs4Sb12: superconductivity and correlations

International Nuclear Information System (INIS)

Measson, M.A.

2005-12-01

The filled skutterudite PrOs 4 Sb 12 is the first Pr-based heavy fermion superconductor. This thesis addresses several important open questions including the determination of the quasi-particle mass renormalisation, the nature and mechanism of superconductivity, and the intrinsic or extrinsic nature of the double superconducting transition seen in the specific heat. A fit of the specific heat with magnetic interactions between the ions Pr is proposed. We extract from it an electronic term of between 300-750 mJ/K 2 .mol(Pr). Analysis of the specific heat jump provides evidence that heavy carriers are involved in Cooper pairing and that superconductivity is strongly coupled. Extensive characterizations by specific heat, resistivity, susceptibility measurements show that a double transition appears in the best samples. Nevertheless we bring the first serious doubts on the intrinsic nature of the double transition, because we have found samples with a single sharp transition at Tc2 and because the ratio of the two specific heat jumps shows strong dispersion among the samples. Furthermore we have measured the superconducting phase diagrams with an A.C. specific heat technique under magnetic field and under pressure up to 4.2 GPa, and we show that the two transitions, Tc1 and Tc2, exhibit similar behaviours with magnetic field and pressure. We find a strong change in the pressure dependence of Tc's above 2 GPa which might be related to a change in the nature of the superconductivity under pressure (at least partially mediated by fluctuations and only by phonons at respectively low and high pressure) which may be linked to the increase of the crystal field gap of the Pr ions. Analysis of the upper critical field shows the presence of at least two superconducting bands and concludes to a singlet nature of the pairing. A strong distortion of the flux-line lattice, which is constant with temperature and field, is obtained by small angle neutron scattering measurement

Zinc substitution effects on the superconducting properties of Nd1.85Ce0.15CuO4-δ

International Nuclear Information System (INIS)

Garcia-Vazquez, V.; Mazumdar, S.; Falco, C.M.; Barlingay, C.; Risbud, S.H.

1990-01-01

With the discovery of the electron superconductors, a new dimension was added to research in the field of high-temperature superconductivity. Studies of these materials should help elucidate the mechanism responsible for high-temperature superconductivity, as well as improve strategies for finding new superconductors. In this paper, we discuss the superconducting structural properties of Nd 1.85 Ce 0.15 (Cu 1-y Zn y )O 4 as a function of the Zn concentration y. Detailed comparisons with previous results of similar substitution studies in the single-CuO 2 -layer hole superconductor La 1.85 Sr 0.15 CuO 4 also are made. We have found that the non-magnetic element Zn has a detrimental effect on the T'-phase electron superconductor, and that this effect is as strong as in the T-phase hole superconductor. Theoretical implications and the question of electron-hole symmetry are also discussed

Electromechanical characterization of superconducting wires and tapes at 77 K

CERN Document Server

Bjoerstad, Roger

The strain dependency of the critical current in state-of-the-art cuprate high-temperature superconductors (HTS) has been characterized. A universal test machine (UTM) combined with a critical current measurement system has been used to characterize the mechanical and the superconducting properties of conductors immersed in an open liquid nitrogen dewar. A set-up has been developed in order to perform simultaneous measurements of the superconductor lattice parameter changes, critical current, as well as the stress and strain at 77 K in self-field in a high energy synchrotron beamline. The HTS tapes and wires studied were based on YBCO, Bi-2223 and Bi-2212. The YBCO tapes were produced by SuperPower and American Superconductors (AMSC). Two types of Bi-2223 tapes, HT and G, were produced by Sumitomo Electric Industries (SEI). The Bi-2212 wires were produced by Oxford Superconducting Technology (OST) using Nexans granulate precursor, before undergoing a specialized over pressure (OP) processing and heat treatmen...

Experimental Investigation of Magnetic Superconducting, and other Phase Transitions in Novel f-Electron Materials at Ultra-high Pressures Using Designer Diamond Anvils

International Nuclear Information System (INIS)

Maple, M. Brian

2005-01-01

Pressure is a powerful control parameter, owing to its ability to affect crystal and electronic structure without introducing defects, for the investigation of condensed matter systems. Some f-electron, heavy-fermion materials display interesting and novel behavior when exposed to pressures achievable with conventional experimental techniques; however, a growing number of condensed matter systems require extreme conditions such as ultrahigh pressures, high magnetic fields, and ultralow temperatures to sufficiently explore the important properties. To that end, we have been funded to develop an ultrahigh pressure facility at the University of California, San Diego (UCSD) in order to investigate superconductivity, magnetism, non-Fermi liquid behavior, and other phenomena under extreme conditions. Our goals for the second year of this grant were as follows: (a) perform electrical resistivity measurements on novel samples at a myriad of pressures using conventional piston-cylinder techniques, Bridgman anvil techniques, and diamond anvil cell technology; (b) install, commission, and operate an Oxford Kelvinox MX-100 dilution refrigerator for access to ultralow temperatures and high magnetic fields. (c) continue the development of diamond anvil cell (DAC) technology. During the past year, we have successfully installed the Oxford Kelvinox MX-100 dilution refrigerator and verified its operability down to 12 mK. We have begun an experimental program to systematically investigate the f-electron compound URu2Si2 under pressure and in the presence of magnetic fields. We have also continued our collaborative work with Sam Weir at Lawrence Livermore National Laboratory (LLNL) on Au4V and implemented a new corollary study on Au1-xVx using ultrahigh pressures. We have continued developing our DAC facility by designing and constructing an apparatus for in situ pressure measurement as well as designing high pressure cells. This report serves to highlight the progress we have made

Synthesis of Bulk Superconducting Magnesium Diboride

Directory of Open Access Journals (Sweden)

Margie Olbinado

2002-06-01

Full Text Available Bulk polycrystalline superconducting magnesium diboride, MgB2, samples were successfully prepared via a one-step sintering program at 750°C, in pre Argon with a pressure of 1atm. Both electrical resistivity and magnetic susceptibility measurements confirmed the superconductivity of the material at 39K, with a transition width of 5K. The polycrystalline nature, granular morphology, and composition of the sintered bulk material were confirmed using X-ray diffractometry (XRD, scanning electron microscopy (SEM, and energy dispersive X-ray analysis (EDX.

High-Tc cuprate superconductivity in a nutshell

International Nuclear Information System (INIS)

Won, Hyekyung; Haas, Stephan; Parker, David; Maki, Kazumi

2005-01-01

Since the discovery of high-T c cuprate superconductivity in 1986 many new experimental techniques and theoretical concepts have been developed. In particular it was shown that the BCS theory of d-wave superconductivity describes semi-quantitatively the high-T c superconductivity. Furthermore, it was demonstrated that Volovik's approach is extremely useful for finding the quasiparticle properties in the vortex state. Here we survey these developments and forecast future directions. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Field quality of LHC superconducting dipole magnets

International Nuclear Information System (INIS)

Mishra, R.K.

2003-01-01

The author reports here the main results of field measurements performed so far on the LHC superconducting dipoles at superfluid helium temperature. The main field strength at injection, collision conditions and higher order multipoles are discussed. Superconducting magnets exhibit additional field imperfections due to diamagnetic properties of superconducting cables, apart from geometric error, saturation of iron yoke and eddy currents error. Dynamic effects on field harmonics, such as field decay at injection and subsequent snap back are also discussed. (author)

Superconducting composite for magnetic bearings

International Nuclear Information System (INIS)

Rigney, T.K. II.

1995-01-01

A composite includes granules of Type II superconducting material and granules of rare-earth permanent magnets that are distributed in a binder. The composite is a two-phase structure that combines the properties of the superconductor and magnets with the flexibility and toughness of a polymeric material. A bearing made from this composite has the load capacity and stiffness of a permanent magnet bearing with added stability from a Type II superconducting material. 7 figs

Superconducting phase transition in STM tips

Energy Technology Data Exchange (ETDEWEB)

Eltschka, Matthias; Jaeck, Berthold; Assig, Maximilian; Etzkorn, Markus; Ast, Christian R. [Max Planck Institute for Solid State Research, Stuttgart (Germany); Kern, Klaus [Max Planck Institute for Solid State Research, Stuttgart (Germany); Ecole Polytechnique Federale de Lausanne (Switzerland)

2015-07-01

The superconducting properties of systems with dimensions comparable to the London penetration depth considerably differ from macroscopic systems. We have studied the superconducting phase transition of vanadium STM tips in external magnetic fields. Employing Maki's theory we extract the superconducting parameters such as the gap or the Zeeman splitting from differential conductance spectra. While the Zeeman splitting follows the theoretical description of a system with s=1/2 and g=2, the superconducting gaps as well as the critical fields depend on the specific tip. For a better understanding of the experimental results, we solve a one dimensional Usadel equation modeling the superconducting tip as a cone with the opening angle α in an external magnetic field. We find that only a small region at the apex of the tip is superconducting in high magnetic fields and that the order of the phase transition is directly determined by α. Further, the spectral broadening increases with α indicating an intrinsic broadening mechanism due to the conical shape of the tip. Comparing these calculations to our experimental results reveals the order of the superconducting phase transition of the STM tips.

Superconductivity

International Nuclear Information System (INIS)

Palmieri, V.

1990-01-01

This paper reports on superconductivity the absence of electrical resistance has always fascinated the mind of researchers with a promise of applications unachievable by conventional technologies. Since its discovery superconductivity has been posing many questions and challenges to solid state physics, quantum mechanics, chemistry and material science. Simulations arrived to superconductivity from particle physics, astrophysic, electronics, electrical engineering and so on. In seventy-five years the original promises of superconductivity were going to become reality: a microscopical theory gave to superconductivity the cloth of the science and the level of technological advances was getting higher and higher. High field superconducting magnets became commercially available, superconducting electronic devices were invented, high field accelerating gradients were obtained in superconductive cavities and superconducting particle detectors were under study. Other improvements came in a quiet progression when a tornado brought a revolution in the field: new materials had been discovered and superconductivity, from being a phenomenon relegated to the liquid Helium temperatures, became achievable over the liquid Nitrogen temperature. All the physics and the technological implications under superconductivity have to be considered ab initio

Superconducting properties of the η-pairing state in the Penson-Kolb-Hubbard model

International Nuclear Information System (INIS)

Czart, W.R.; Robaszkiewicz, S.

2004-01-01

The Penson-Kolb-Hubbard model, i.e. the Hubbard model with the pair-hopping interaction J is studied. We focus on the properties of the superconducting state with the Cooper-pair center-of mass momentum q Q(η-phase). The transition into the η-phase, which is favorized by the repulsive J (J c |, dependent on band filling, on-site interaction U and band structure, and the system never exhibits standard BCS-like features. This is in obvious contrast with the properties of the isotropic s-wave state, stabilized by the attractive J and attractive U, which exhibit at T = 0 a smooth crossover from the BCS-like limit to that of tightly bound pairs with increasing pairing strength. (author)

Experimental studies on the thermal properties of fast pulsed superconducting accelerator magnets

International Nuclear Information System (INIS)

Bleile, Alexander

2016-01-01

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

Superconducting plasmas

International Nuclear Information System (INIS)

Ohnuma, Toshiro; Ohno, J.

1994-01-01

Superconducting (SC) plasmas are proposed and investigated. The SC plasmas are not yet familiar and have not yet been studied. However, the existence and the importance of SC plasmas are stressed in this report. The existence of SC plasmas are found as follows. There is a fundamental property of Meissner effect in superconductors, which shows a repulsive effect of magnetic fields. Even in that case, in a microscopic view, there is a region of magnetic penetration. The penetration length λ is well-known as London's penetration depth, which is expressed as δ = (m s /μ 0 n s q s 2 ) 1/2 where m s , n s , q s and μ o show the mass, the density, the charge of SC electron and the permeability in free space, respectively. Because this expression is very simple, no one had tried it into more simple and meaningful form. Recently, one of the authors (T.O.) has found that the length can be expressed into more simple and understandable fundamental form as λ = c/ω ps where c = (ε 0 μ 0 ) -1/2 and ω ps = (n s q s 2 /m s ε 0 ) 1/2 are the light velocity and the superconducting plasma frequency. From this simple expression, the penetration depth of the magnetic field to SC is found as a SC plasma skin depth, that is, the fundamental property of SC can be expressed by the SC plasmas. This discovery indicates an importance of the studies of superconducting plasmas. From these points, several properties (propagating modes et al) of SC plasmas, which consist of SC electrons, normal electrons and lattice ions, are investigated in this report. Observations of SC plasma frequency is also reported with a use of Terahertz electromagnet-optical waves

Superconductivity in SnO: a nonmagnetic analog to Fe-based superconductors?

Science.gov (United States)

Forthaus, M K; Sengupta, K; Heyer, O; Christensen, N E; Svane, A; Syassen, K; Khomskii, D I; Lorenz, T; Abd-Elmeguid, M M

2010-10-08

We discovered that under pressure SnO with α-PbO structure, the same structure as in many Fe-based superconductors, e.g., β-FeSe, undergoes a transition to a superconducting state for p≳6 GPa with a maximum Tc of 1.4 K at p=9.3 GPa. The pressure dependence of Tc reveals a domelike shape and superconductivity disappears for p≳16 GPa. It is further shown from band structure calculations that SnO under pressure exhibits a Fermi surface topology similar to that reported for some Fe-based superconductors and that the nesting between the hole and electron pockets correlates with the change of Tc as a function of pressure.

Development of high pressure rinsing set up for 650 MHz, 5- cell superconducting RF cavity cleaning

International Nuclear Information System (INIS)

Suhane, S.K.; Chauhan, S.K.; Bose, A.; Kokil, S.V.; Rajput, D.S.; Oraon, B.; Md Hussain; Sahu, A.; Raghavendra, S.; Joshi, S.C.

2015-01-01

High pressure rinsing (HPR) is an ultra-cleanliness process for the surface preparation of high field superconducting RF cavities. Any dust particle or chemical residue on the interior of cavity causes field emission. Jets of high pressure (80-100 bar) ultra pure water dislodge surface contaminants that normally resist removal with conventional rinsing procedures, leading to substantial reduction in field emission and better cavity performance. For cleaning of 650 MHz, 5-cell SRF cavities, a high pressure rinsing set up has been developed at RRCAT. The HPR tool has a rotating wand coaxial with the vertically mounted SRF cavity that is moving up and down. Fan style spray nozzles are attached to the end of the rotating wand and the water jets emerging from spray nozzles scan the entire internal surface of the cavity. The set-up was installed in a specially built clean area meeting cleanliness class 100 standards. The ultrapure water with resistivity 2 ≥ 18 MΩ-cm required for rinsing is obtained from a dedicated water purification system installed for this purpose. The paper describes the salient design and constructional details of the high pressure rinsing set up. Characterization of water jet parameters based on the momentum transfer between the water jet and a load cell is also presented. (author)

Growth of epitaxial Ba2YCu3O(7-delta) thin films and control of their superconducting properties

International Nuclear Information System (INIS)

Siegal, M.P.; Phillips, J.M.

1992-01-01

The relationship is experimentally defined between the superconducting behavior of Ba2YCu3O(7-delta) (BYCO) films and their structural characteristics. The BYCO films are grown on LaAlO3 100-plane by coevaporating BaF2, Y, and Cu followed by ex situ annealing, and the crystalline quality is tested by Rutherford backscattering ion channeling. SEM is employed to study film morphology, and several techniques are used to measure the transition temperature (Tc), critical current density (Jc), and the penetration length. It is found that point defects and dislocations decrease as the high-temperature stage (Ta) increases; crevices, pinholes, and microcracks are also noted which are related to specific values of Tc, Ta, and penetration length. The results of the present experiments indicate that the material properties of superconducting materials should be examined closely to distinguish between pure superconducting behavior and characteristics related to material structure. 21 refs

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.

Effect of substituted rare earth element in (Yb1-xNd x)Ba2Cu3O y thin film on growth orientation and superconducting properties

International Nuclear Information System (INIS)

Honda, R.; Ichino, Y.; Yoshida, Y.; Takai, Y.; Matsumoto, K.; Ichinose, A.; Kita, R.; Mukaida, M.; Horii, S.

2005-01-01

We studied the orientation and superconducting properties in (Yb 1-x Nd x )Ba 2 Cu 3 O y (Yb/Nd123) thin films as a function of Yb/Nd composition ratio x. As a results, we needed so high oxygen pressure as to increase x for obtaining the c-axis oriented films. J c -B curves in the Yb/Nd123 thin films were superior to that in YBa 2 Cu 3 O y thin film. Since a RE fluctuation in a composition in the Yb/Nd123 thin films was observed with TEM-EDX, we speculated the pinning centers in the Yb/Nd123 thin films were strongly affected by the RE fluctuation

Impurity effects in superconducting UPt3

International Nuclear Information System (INIS)

Aronson, M.C.; Vorenkamp, T.; Koziol, Z.; de Visser, A.; Bakker, K.; Franse, J.J.M.; Smith, J.L.

1991-01-01

Superconducting UPt 3 is characterized by a novel and complex magnetic field-temperature phase diagram, with two superconducting transitions at T c1 and T c2 in zero field. We have studied the effects of Pd and Y impurities on the zero field superconducting properties of UPt 3 . Resistance measurements show that both dopants increase the residual resistivity and decrease the spin fluctuation temperature in the normal state. T c1 is depressed by both dopants, but more effectively by Pd. |T c1 - T c2 | is essentially unaffected by Y doping, but increases dramatically with Pd doping

Quantum confinement effects on superconducting properties of Lead nanocrystals

Science.gov (United States)

Aubin, Herve; Moreira, Helena; Mahler, Benoit; Dubertret, Benoit

2008-03-01

We developed a new chemical synthesis method for producing large quantities of monodispersed lead (Pb) nanocrystals. They are obtained from the alcohol reduction of a mixture of two lead carboxylates with alkyl chains of different lengths, dissolved in a high temperature solvent. The nanocrystals obtained are protected from oxydation and aggregation by long chain fatty acids and their diameter can be tuned to reach values as low as 10 nm. Our results suggest that monodispersed particules are obtained when nucleation and growth occur at distincts temperatures, possibly as a consequence of different reactivities of the two lead carboxylates used in the solution. Owing to the large quantities of monodispersed particles produced, thermodynamics studies as function of particles diameter become possible. In particular, we will present a study of the effect of quantum confinement on superconducting properties of these Pb particles through SQUID magnetometry measurements.

Superconductivity : Controlling magnetism

NARCIS (Netherlands)

Golubov, Alexandre Avraamovitch; Kupriyanov, Mikhail Yu.

Manipulation of the magnetic state in spin valve structures by superconductivity has now been achieved, opening a new route for the development of ultra-fast cryogenic memories. Spintronics is a rapidly developing field that allows insight into fundamental spin-dependent physical properties and the

Superconductivity, energy storage and switching

International Nuclear Information System (INIS)

Laquer, H.L.

1974-01-01

The phenomenon of superconductivity can contribute to the technology of energy storage and switching in two distinct ways. On one hand the zero resistivity of the superconductor can produce essentially infinite time constants so that an inductive storage system can be charged from very low power sources. On the other hand, the recovery of finite resistivity in a normal-going superconducting switch can take place in extremely short times, so that a system can be made to deliver energy at a very high power level. Topics reviewed include: physics of superconductivity, limits to switching speed of superconductors, physical and engineering properties of superconducting materials and assemblies, switching methods, load impedance considerations, refrigeration economics, limitations imposed by present day and near term technology, performance of existing and planned energy storage systems, and a comparison with some alternative methods of storing and switching energy. (U.S.)

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

Critical currents and superconductivity ferromagnetism coexistence in high-Tc oxides

CERN Document Server

Khene, Samir

2016-01-01

The book comprises six chapters which deal with the critical currents and the ferromagnetism-superconductivity coexistence in high-Tc oxides. It begins by gathering key data for superconducting state and the fundamental properties of the conventional superconductors, followed by a recap of the basic theories of superconductivity. It then discusses the differences introduced by the structural anisotropy on the Ginzburg-Landau approach and the Lawrence-Doniach model before addressing the dynamics of vortices and the ferromagnetism-superconductivity coexistence in high-Tc oxides, and provides an outline of the pinning phenomena of vortices in these materials, in particular the pinning of vortices by the spins. It elucidates the methods to improve the properties of superconducting materials for industrial applications. This optimization aims at obtaining critical temperatures and densities of critical currents at the maximum level possible. Whereas the primary objective is the basic mechanisms pushing the superco...

Structural and superconducting properties of sputter-deposited niobium films for applications in RF accelerating cavities

CERN Document Server

Peck, M A

2000-01-01

The present work presents the results of a systematic study of superconducting and structural properties of niobium films sputter deposited onto the inner walls of radiofrequency copper resonators. The measured superconducting quantities include the surface resistance, the critical temperature, the penetration depth and the upper and lower critical fields. In addition to films grown with different discharge gases (Xe, Kr, Ar, Ne and Ar-Ne mixtures) and to films grown on substrates prepared under different conditions, the study also includes massive niobium cavities. The surface resistance is analysed in terms of its dependence on the temperature and on the rf field amplitude and, when possible, compared to theoretical predictions. In general, good agreement with BCS theory is observed. All experimental results are presented in the form of a simple, but adequate parameterisation. The residual resistance is observed to be essentially uncorrelated with the other variables, but strongly dependent on the macroscop...

Dimensionality Driven Enhancement of Ferromagnetic Superconductivity in URhGe

Science.gov (United States)

Braithwaite, Daniel; Aoki, Dai; Brison, Jean-Pascal; Flouquet, Jacques; Knebel, Georg; Nakamura, Ai; Pourret, Alexandre

2018-01-01

In most unconventional superconductors, like the high-Tc cuprates, iron pnictides, or heavy-fermion systems, superconductivity emerges in the proximity of an electronic instability. Identifying unambiguously the pairing mechanism remains nevertheless an enormous challenge. Among these systems, the orthorhombic uranium ferromagnetic superconductors have a unique position, notably because magnetic fields couple directly to ferromagnetic order, leading to the fascinating discovery of the reemergence of superconductivity in URhGe at a high field. Here we show that uniaxial stress is a remarkable tool allowing the fine-tuning of the pairing strength. With a relatively small stress, the superconducting phase diagram is spectacularly modified, with a merging of the low- and high-field superconducting states and a significant enhancement of the superconductivity. The superconducting critical temperature increases both at zero field and under a field, reaching 1 K, more than twice higher than at ambient pressure. This enhancement of superconductivity is shown to be directly related to a change of the magnetic dimensionality detected from an increase of the transverse magnetic susceptibility: In addition to the Ising-type longitudinal ferromagnetic fluctuations, transverse magnetic fluctuations also play an important role in the superconducting pairing.

Collective modes in superconducting rhombohedral graphite

Energy Technology Data Exchange (ETDEWEB)

Kauppila, Ville [O.V. Lounasmaa Laboratory, Aalto University (Finland); Hyart, Timo; Heikkilae, Tero [University of Jyvaeskylae (Finland)

2015-07-01

Recently it was realized that coupling particles with a Dirac dispersion (such as electrons in graphene) can lead to a topologically protected state with flat band dispersion. Such a state could support superconductivity with unusually high critical temperatures. Perhaps the most promising way to realize such coupling in real materials is in the surface of rhombohedrally stacked graphite. We consider collective excitations (i.e. the Higgs modes) in surface superconducting rhombohedral graphite. We find two amplitude and two phase modes corresponding to the two surfaces of the graphite where the superconductivity lives. We calculate the dispersion of these modes. We also derive the Ginzburg-Landau theory for this material. We show that in superconducting rhombohedral graphite, the collective modes, unlike in conventional BCS superconductors, give a large contribution to thermodynamic properties of the material.

Application of high-pressure techniques: stabilization and oxidation-state control of novel superconductive and related multi-layered copper oxides

International Nuclear Information System (INIS)

Yamauchi, H.; Karppinen, M.

2000-01-01

Copper oxide superconductors possess multi-layered structures with a layer sequence of -CuO 2 -(Q-CuO 2 ) n-1 -AO-(MO 1±δ ) m -AO- or -CuO 2 -B-(O 2 -B) s-1 -CuO 2 -AO-(MO 1±δ ) m -AO- along the elongated c axis. Based on this layer sequence, the known copper oxide structures are categorized as members of the homologous series, M m A r Q n-1 Cu n O m+r+2 +n ±δ (M-mr(n-1)n ; category A) or M m A 2k B s Cu 1+k O m +4k +2s±δ (M-m(2k)s (1+k ); category B). Stabilization of such structures especially in the case of high values of the n /s parameter, i.e. the higher members of the homologous series, has been demonstrated to be apparently promoted under high pressures and/or strongly oxidizing conditions. Consequently, techniques for applying both high oxygen gas pressures (10-2000 atm) and ultra-high solid-medium pressures (2-8 GPa) have been advantageously utilized in synthesizing various superconductive copper oxide phases. Especially the ultra-high solid-medium pressure synthesis carried out in the so-called cubic-anvil/belt-type apparatus has proven to be extremely successful in synthesizing novel superconductive phases. In order to achieve high partial pressures of oxygen in the solid-medium environment, 'external' oxygen-generating oxides such as KClO 4 , KClO 3 and Ag 2 O 2 are commonly added to the precursor mixtures. It is emphasized that in some cases it is possible to utilize 'internal' oxidizing agents alone, i.e. highly oxidized precursors such as BaCuO 2+δ and Ba 2 Cu 3 O 5+δ containing metal constituents common with the desired copper oxide phase only. In the present paper, the potential and applications of high-pressure techniques in synthesizing multi-layered copper oxides and related structures are reviewed and discussed with emphasis on the important 'historical' discoveries of novel phases and the present status of controlled production of high-quality samples of such phases. (author)

Unconventional superconductivity in iron pnictides: Magnon mediated pairing

Science.gov (United States)

kar, Raskesh; Paul, Bikash Chandra; Misra, Anirban

2018-02-01

We study the phenomenon of unconventional superconductivity in iron pnictides on the basis of localized-itinerant model. In this proposed model, superconductivity arises from the itinerant part of electrons, whereas antiferromagnetism arises from the localized part. The itinerant electrons move over the sea of localized electrons in antiferromagnetic alignment and interact with them resulting in excitation of magnons. We find that triplet pairing of itinerant electrons via magnons is possible in checkerboard antiferromagnetic spin configuration of the substances CaFe2As2 and BaFe2As2 in pure form for umklapp scattering with scattering wave vector Q =(1 , 1) , in the unit of π/a where a being one orthorhombic crystal parameter, which is the nesting vector between two Fermi surfaces. The interaction potential figured out in this way, increases with the decrease in nearest neighbour (NN) exchange couplings. Under ambient pressure, with stripe antiferromagnetic spin configuration, a very small value of coupling constant is obtained which does not give rise to superconductivity. The critical temperature of superconductivity of the substances CaFe2As2 and BaFe2As2 in higher pressure checkerboard antiferromagnetic spin configuration are found to be 12.12 K and 29.95 K respectively which are in agreement with the experimental results.

Property evaluation of Ni base alloy for superconducting generators and its application to seal welded joints

International Nuclear Information System (INIS)

Nobuhisa Suzuki; Toshiaki Murakami; Kenichi Suzuki; Satoru Asai; Minorou Tanaka; Yoshio Kobayashi

1992-01-01

Property requirements demanded on structural materials for rotors of superconducting generators are quite strict while there are many themes in the technical development of such materials. Components used in the cryogenic temperature are of course required to be nonmagnetic material. Additional requirements demanded on cryogenic structural materials for high response excitation superconducting generators can be summarized as follows: (1) 0.2% yield strength > 800 MPa (RT) (2) Charpy absorbed energy > 25 J (4K) (3) Electrical resistivity > 90 μΩ·cm (4K). As a candidate material which satisfy the above property requirements, we can cite precipitation-hardened Ni base alloys, for example, Inconel 718. However, production of Inconel718 is limited to about 2 tons due to problems related to segregation etc., and therefore fabrication of large-sized ingots for manufacturing generator components may be difficult. Also, there may be problems regarding weldability, especially from the viewpoint of microcracking in the heat affected zone, among strength-supporting parts or the parts requiring functional capability such as seal welded joints. Under such background circumstances, we conducted studies on chemical composition by considering producibility of large-sized ingots and weldability of the alloy as well as property evaluations of materials incorporating such requirements. Further, included in this paper are the application of the alloy to seal welded joints and its unified fatigue strength evaluation method

The superconducting proximity effect in epitaxial Al/Pb nanocomposites

International Nuclear Information System (INIS)

Wang, H; Vantomme, A; Temst, K; Picot, T; Houben, K; Moorkens, T; Van Haesendonck, C; Van Bael, M J; Grigg, J; Brown, S A; Biermans, E; Bals, S

2014-01-01

We have investigated the superconducting properties of Pb nanoparticles with a diameter ranging from 8 to 20 nm, synthesized by Pb + ion implantation in a crystalline Al matrix. A detailed structural characterization of the nanocomposites reveals the highly epitaxial relation between the Al crystalline matrix and the Pb nanoparticles. The Al/Pb nanocomposites display a single superconducting transition, with the critical temperature T c increasing with the Pb content. The dependence of T c on the Pb/Al volume ratio was compared with theoretical models of the superconducting proximity effect based on the bulk properties of Al and Pb. A very good correspondence with the strong-coupling proximity effect model was found, with an electron–phonon coupling constant in the Pb nanoparticles slightly reduced compared to bulk Pb. Our result differs from other studies on Pb nanoparticle based proximity systems where weak-coupling models were found to better describe the T c dependence. We infer that the high interface quality resulting from the ion implantation synthesis method is a determining factor for the superconducting properties. Critical field and critical current measurements support the high quality of the nanocomposite superconducting films. (paper)

Quality measurements of resonance cavities in behalf of investigation of microwave properties of superconducting materials

International Nuclear Information System (INIS)

Dekkers, G.; Ridder, M. de.

1988-01-01

A method for investigating conducting properties at microwave frequencies of superconducting materials by means of quality measurements of a resonance cavity is described. The method is based on the direct relationship of the quality factor of a resonance circuit, in this case a resonance cavity, with the losses in the circuit. In a resonance cavity these losses are caused by the material properties of the resonance cavity. Therefore quality measurements yield, essentially, a possibility for investigation of conducting properties of materials. The underlying theory of the subject, the design of a special resonance cavity, the measuring methods and the accuracy in the relation of the measured quality factor and the specific conductivity of the material is presented. refs.; figs.; tabs

Magnetism and superconductivity in Eu-based iron pnictides

Energy Technology Data Exchange (ETDEWEB)

Zapf, Sina [1. Physikalisches Institut, Universitaet Stuttgart (Germany)

2015-07-01

EuFe{sub 2}As{sub 2} is an extraordinary parent compound of the iron pnictides, as it exhibits at low temperatures - additional to the Fe spin density wave - long-range magnetic order of the Eu{sup 2+} local moments. Nevertheless, bulk superconductivity around 30 K can be induced by mechanical pressure or chemical substitution. In this talk we review the remarkable interplay of unconventional superconductivity, itinerant and local magnetism in Eu based iron pnictides. We focus on the appearance of a re-entrant spin glass phase that coexists with superconductivity and an indirect magneto-elastic coupling, enabling the persistent magnetic detwinning by small magnetic fields.

Moessbauer and muon spin relaxation investigation of magnetic and superconducting properties of Ca{sub 1-x}Na{sub x}Fe{sub 2}As{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Materne, Philipp; Bubel, Sirko; Maeter, Hemke; Sarkar, Rajib; Klauss, Hans-Henning [Institut fuer Festkoerperphysik, Technische Universitaet Dresden, 01062 Dresden (Germany); Harnagea, Luminita; Wurmehl, Sabine; Buechner, Bernd [IFW Dresden, Postfach 270016, 01171 Dresden (Germany); Luetkens, Hubertus [Paul-Scherrer-Institut, 5232 Villigen (Switzerland)

2013-07-01

The antiferromagnetic parent compound, CaFe{sub 2}As{sub 2}, shows a supression of the spin density wave and a subsequent superconducting state upon partial substitution of Ca by Na. Along the substitution series, superconducting transition temperatures up to ∼35 K were found. We studied the electronic phase diagram of Ca{sub 1-x}Na{sub x}Fe{sub 2}As{sub 2} using Moessbauer spectroscopy and muon spin relaxation experiments. We have analyzed the data in terms of magnetic and superconducting properties and possible coexistence of superconductivity and spin density wave order. We compared our results with recently published data of Ba{sub 1-x}Na{sub x}Fe{sub 2}As{sub 2}.

Modern aspects of Josephson dynamics and superconductivity electronics

CERN Document Server

Askerzade, Iman; Cantürk, Mehmet

2017-01-01

In this book new experimental investigations of properties of Josephson junctions and systems are explored with the help of recent developments in superconductivity. The theory of the Josephson effect is presented taking into account the influence of multiband and anisotropy effects in new superconducting compounds. Anharmonicity effects in current-phase relation on Josephson junctions dynamics are discussed. Recent studies in analogue and digital superconductivity electronics are presented. Topics of special interest include resistive single flux quantum logic in digital electronics. Application of Josephson junctions in quantum computing as superconducting quantum bits are analyzed. Particular attention is given to understanding chaotic behaviour of Josephson junctions and systems. The book is written for graduate students and researchers in the field of applied superconductivity.

Solids, liquids, and gases under high pressure

Science.gov (United States)

Mao, Ho-Kwang; Chen, Xiao-Jia; Ding, Yang; Li, Bing; Wang, Lin

2018-01-01

Pressure has long been recognized as a fundamental thermodynamic variable but its application was previously limited by the available pressure vessels and probes. The development of megabar diamond anvil cells and a battery of associated in-laboratory and synchrotron techniques at the turn of the century have opened a vast new window of opportunities. With the addition of the pressure dimension, we are facing a new world with an order of magnitude more materials to be discovered than all that have been explored at ambient pressure. Pressure drastically and categorically alters all elastic, electronic, magnetic, structural, and chemical properties, and pushes materials across conventional barriers between insulators and superconductors, amorphous and crystalline solids, ionic and covalent compounds, vigorously reactive and inert chemicals, etc. In the process, it reveals surprising high-pressure physics and chemistry and creates novel materials. This review describes the principles and methodology used to reach ultrahigh static pressure: the in situ probes, the physical phenomena to be investigated, the long-pursued goals, the surprising discoveries, and the vast potential opportunities. Exciting examples include the quest for metallic hydrogen, the record-breaking superconducting temperature of 203 K in HnS , the complication of "free-electron gas" alkali metals, the magnetic collapse in 3 d transition elements, the pressure-induced superconductivity from topological insulators, the novel stoichiometry in simple compounds, the interaction of nanoscience, the accomplishment of 750 GPa pressure, etc. These highlights are the integral results of technological achievements, specific measurements, and theoretical advancement; therefore, the same highlights will appear in different sections corresponding to these different aspects. Overall, this review demonstrates that high-pressure research is a new dimension in condensed-matter physics.

Growth orientation and superconducting properties of YBa2Cu3O7-δ films prepared by the low-fluorine sol-gel process

International Nuclear Information System (INIS)

Lei Li; Zhao Gaoyang; Xu Hui; Zhao Juanjuan

2010-01-01

YBa 2 Cu 3 O 7-δ (YBCO) films were deposited on (100)-oriented LaAlO 3 (LAO) single crystal substrates by the dip-coating process using low-fluorine solution. Their microstructures were characterized with the aid of X-ray diffractometry, scanning electron microscopy and high-resolution transmission electron microscopy. Their superconducting properties were measured by the standard four-probe method. The experiment results show that the film obtained under high enough humidity conditions exhibits better c-axis texture and superconducting properties than the film under a relatively low humidity conditions. Based on the classical nucleation and chemical reaction thermodynamics theory, the underlying crystalline and growth mechanisms of YBCO films under certain humidity conditions are explained in combination with our experimental results. It is suggested that the unreacted intermediate phases such as BaF 2 and CuO aggregated in the YBCO grain boundary will cause lattice distortion in the YBCO matrix and further induce the formation of a-axis oriented YBCO grains as crystallization proceeds. Therefore, it is believed that the relative content of water vapor within the heat-treatment atmosphere plays quite an important role in the preparation of c-axis oriented YBCO film with good superconducting properties. (semiconductor materials)

Melt formed superconducting joint between superconducting tapes

International Nuclear Information System (INIS)

Benz, M.G.; Knudsen, B.A.; Rumaner, L.E.; Zaabala, R.J.

1992-01-01

This patent describes a superconducting joint between contiguous superconducting tapes having an inner laminate comprised of a parent-metal layer selected from the group niobium, tantalum, technetium, and vanadium, a superconductive intermetallic compound layer on the parent-metal layer, a reactive-metal layer that is capable of combining with the parent-metal and forming the superconductive intermetallic compound, the joint comprising: a continuous precipitate of the superconductive intermetallic compound fused to the tapes forming a continuous superconducting path between the tapes

Superconductivity in Weyl semimetal candidate MoTe{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Qi, Yanpeng; Naumov, Pavel; Rajamathi, Catherine; Barkalov, Oleg; Wu, Shu-Chun; Shekhar, Chandra; Sun, Yan; Suess, Vicky; Schmidt, Marcus; Schwarz, Ulrich; Schnelle, Walter; Felser, Claudia; Medvedev, Sergey [Max Planck Institute for Chemical Physics of Solids, Dresden (Germany); Ali, Mazhar; Cava, Robert [Department of Chemistry, Princeton University, Princeton (United States); Hanfland, Michael [European Synchrotron Radiation Facility, Grenoble (France); Pippel, Eckhard; Werner, Peter; Hillebrand, Reinald; Parkin, Stuart [Max Planck Institute of Microstructure Physics, Halle (Germany); Foerster, Tobias; Kampert, Erik [Dresden High Magnetic Field Laboratory, Dresden (Germany); Yan, Binghai [Max Planck Institute for Chemical Physics of Solids, Dresden (Germany); Max Planck Institute for the Physics of Complex Systems, Dresden (Germany)

2016-07-01

In this work, we investigate the sister compound of WTe{sub 2}, MoTe{sub 2}, which is also predicted to be a Weyl semimetal and a quantum spin Hall insulator in bulk and monolayer form, respectively. We find that MoTe{sub 2} exhibits superconductivity with a resistive transition temperature T{sub c} of 0.1 K. The application of a small pressure is shown to dramatically enhance the T{sub c}, with a maximum value of 8.2 K being obtained at 11.7 GPa (a more than 80-fold increase in Tc). This yields a dome-shaped superconducting phase diagram. Further explorations into the nature of the superconductivity in this system may provide insights into the interplay between superconductivity and topological physics.

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/.

Midwest Superconductivity Consortium: 1994 Progress report

Energy Technology Data Exchange (ETDEWEB)

1995-01-01

The mission of the Midwest Superconductivity Consortium, MISCON, is to advance the science and understanding of high {Tc} superconductivity. During the past year, 27 projects produced over 123 talks and 139 publications. Group activities and interactions involved 2 MISCON group meetings (held in August and January); with the second MISCON Workshop held in August; 13 external speakers; 79 collaborations (with universities, industry, Federal laboratories, and foreign research centers); and 48 exchanges of samples and/or measurements. Research achievements this past year focused on understanding the effects of processing phenomena on structure-property interrelationships and the fundamental nature of transport properties in high-temperature superconductors.

Midwest Superconductivity Consortium: 1994 Progress report

International Nuclear Information System (INIS)

1995-01-01

The mission of the Midwest Superconductivity Consortium, MISCON, is to advance the science and understanding of high T c superconductivity. During the past year, 27 projects produced over 123 talks and 139 publications. Group activities and interactions involved 2 MISCON group meetings (held in August and January); with the second MISCON Workshop held in August; 13 external speakers; 79 collaborations (with universities, industry, Federal laboratories, and foreign research centers); and 48 exchanges of samples and/or measurements. Research achievements this past year focused on understanding the effects of processing phenomena on structure-property interrelationships and the fundamental nature of transport properties in high-temperature superconductors

Contamination issues in superconducting cavity technology

International Nuclear Information System (INIS)

Kneisel, Peter

1997-01-01

The application of radio-frequency superconductivity technology in particle accelerator projects has become increasingly evident in recent years. Several large scale projects around the world are either completed or close to completion, such as CEBAF, HERA, TRISTAN and LEP. And superconducting cavity technology is seriously being considered for future applications in linear colliders (TESLA), high current proton accelerators (APT, spallation neutron sources), muon colliders and free electron lasers for industrial application. The reason for this multitude of activities are matured technology based on a better understanding of the phenomena encountered in superconducting cavities and the influence of improved material properties and contamination and quality control measures

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.

Foreword: Focus on Superconductivity in Semiconductors

Directory of Open Access Journals (Sweden)

Yoshihiko Takano

2008-01-01

Full Text Available Since the discovery of superconductivity in diamond, much attention has been given to the issue of superconductivity in semiconductors. Because diamond has a large band gap of 5.5 eV, it is called a wide-gap semiconductor. Upon heavy boron doping over 3×1020 cm−3, diamond becomes metallic and demonstrates superconductivity at temperatures below 11.4 K. This discovery implies that a semiconductor can become a superconductor upon carrier doping. Recently, superconductivity was also discovered in boron-doped silicon and SiC semiconductors. The number of superconducting semiconductors has increased. In 2008 an Fe-based superconductor was discovered in a research project on carrier doping in a LaCuSeO wide-gap semiconductor. This discovery enhanced research activities in the field of superconductivity, where many scientists place particular importance on superconductivity in semiconductors.This focus issue features a variety of topics on superconductivity in semiconductors selected from the 2nd International Workshop on Superconductivity in Diamond and Related Materials (IWSDRM2008, which was held at the National Institute for Materials Science (NIMS, Tsukuba, Japan in July 2008. The 1st workshop was held in 2005 and was published as a special issue in Science and Technology of Advanced Materials (STAM in 2006 (Takano 2006 Sci. Technol. Adv. Mater. 7 S1.The selection of papers describe many important experimental and theoretical studies on superconductivity in semiconductors. Topics on boron-doped diamond include isotope effects (Ekimov et al and the detailed structure of boron sites, and the relation between superconductivity and disorder induced by boron doping. Regarding other semiconductors, the superconducting properties of silicon and SiC (Kriener et al, Muranaka et al and Yanase et al are discussed, and In2O3 (Makise et al is presented as a new superconducting semiconductor. Iron-based superconductors are presented as a new series of high

Tailoring Superconductivity with Quantum Dislocations.

Science.gov (United States)

Li, Mingda; Song, Qichen; Liu, Te-Huan; Meroueh, Laureen; Mahan, Gerald D; Dresselhaus, Mildred S; Chen, Gang

2017-08-09

Despite the established knowledge that crystal dislocations can affect a material's superconducting properties, the exact mechanism of the electron-dislocation interaction in a dislocated superconductor has long been missing. Being a type of defect, dislocations are expected to decrease a material's superconducting transition temperature (T c ) by breaking the coherence. Yet experimentally, even in isotropic type I superconductors, dislocations can either decrease, increase, or have little influence on T c . These experimental findings have yet to be understood. Although the anisotropic pairing in dirty superconductors has explained impurity-induced T c reduction, no quantitative agreement has been reached in the case a dislocation given its complexity. In this study, by generalizing the one-dimensional quantized dislocation field to three dimensions, we reveal that there are indeed two distinct types of electron-dislocation interactions. Besides the usual electron-dislocation potential scattering, there is another interaction driving an effective attraction between electrons that is caused by dislons, which are quantized modes of a dislocation. The role of dislocations to superconductivity is thus clarified as the competition between the classical and quantum effects, showing excellent agreement with existing experimental data. In particular, the existence of both classical and quantum effects provides a plausible explanation for the illusive origin of dislocation-induced superconductivity in semiconducting PbS/PbTe superlattice nanostructures. A quantitative criterion has been derived, in which a dislocated superconductor with low elastic moduli and small electron effective mass and in a confined environment is inclined to enhance T c . This provides a new pathway for engineering a material's superconducting properties by using dislocations as an additional degree of freedom.

Growth and superconducting properties of Bi2Sr2Ca2Cu3O10 single crystals

International Nuclear Information System (INIS)

Clayton, N; Musolino, N; Giannini, E; Garnier, V; Fluekiger, R

2004-01-01

Single crystals of Bi 2 Sr 2 Ca 2 Cu 3 O 10 (Bi-2223) have been grown using the travelling solvent floating zone technique in an image furnace. Annealing the crystals under high pressures of O 2 increased their critical temperature to 109 K, and resulted in sharp superconducting transitions of ΔT c = 1 K. The superconducting anisotropy of Bi-2223 was found to be ∼ 50, from measurements of the lower critical field with the magnetic field applied parallel and perpendicular to the c-axis. The anisotropy of Bi-2223 is significantly reduced compared to that of Bi 2 Sr 2 CaCu 2 O 8 (Bi-2212), and this accounts for the enhanced irreversibility fields in Bi-2223. Furthermore, Bi-2223 has a higher critical current density, and a reduced magnetic relaxation rate compared to Bi-2212, which are both signatures of more effective pinning in Bi-2223 due to its reduced anisotropy

Variability of mechanical properties of nuclear pressure vessel steels

International Nuclear Information System (INIS)

Petrequin, P.; Soulat, P.

1980-01-01

Causes of variability of mechanical properties nuclear pressure vessel steels are reviewed and discussed. The effects of product shape and size, processing history and heat treatment are investigated. Some quantitative informations are given on the scatter of mechanical properties of typical pressure vessel components. The necessity of using recommended or standardized properties for comparing mechanical properties before and after irradiation in pin pointed. (orig.) [de

Tests of a niobium split-ring superconducting heavy ion accelerating structure

International Nuclear Information System (INIS)

Benaroya, R.; Bollinger, L.M.; Jaffey, A.H.; Khoe, T.K.; Olesen, M.C.; Scheibelhut, C.H.; Shepard, K.W.; Wesolowski, W.A.

1976-01-01

A niobium split-ring accelerating structure designed for use in the Argonne superconducting heavy-ion energy booster was successfully tested. The superconducting resonator has a resonant frequency of 97 MHz and an optimum particle velocity β = 0.11. Ultimate performance is expected to be limited by peak surface fields, which in this structure are 4.7 E/sub a/ electric and 170 E/sub a/ (Gauss) magnetic, where E/sub a/ is the effective accelerating gradient in MV/m. The rf losses in two demountable superconducting joints severely limited performance in initial tests. Following independent measurements of the rf loss properties of several types of demountable joints, one demountable joint was eliminated and the other modified. Subsequently, the resonator could be operated continuously at E/sub a/ = 3.6 MV/m (corresponding to an energy gain of 1.3 MeV per charge) with 10W rf input power. Maximum field level was limited by electron loading. The mechanical stability of the resonator under operating conditions is excellent: vibration induced eigenfrequency noise is less than 120 Hz peak to peak, and the radiation pressure induced frequency shift is Δf/f = 1.6 x 10 -6 E/sub a/ 2

Tests of a niobium split-ring superconducting heavy ion accelerating structure

Energy Technology Data Exchange (ETDEWEB)

Benaroya, R.; Bollinger, L.M.; Jaffey, A.H.; Khoe, T.K.; Olesen, M.C.; Scheibelhut, C.H.; Shepard, K.W.; Wesolowski, W.A.

1976-01-01

A niobium split-ring accelerating structure designed for use in the Argonne superconducting heavy-ion energy booster was successfully tested. The superconducting resonator has a resonant frequency of 97 MHz and an optimum particle velocity ..beta.. = 0.11. Ultimate performance is expected to be limited by peak surface fields, which in this structure are 4.7 E/sub a/ electric and 170 E/sub a/ (Gauss) magnetic, where E/sub a/ is the effective accelerating gradient in MV/m. The rf losses in two demountable superconducting joints severely limited performance in initial tests. Following independent measurements of the rf loss properties of several types of demountable joints, one demountable joint was eliminated and the other modified. Subsequently, the resonator could be operated continuously at E/sub a/ = 3.6 MV/m (corresponding to an energy gain of 1.3 MeV per charge) with 10W rf input power. Maximum field level was limited by electron loading. The mechanical stability of the resonator under operating conditions is excellent: vibration induced eigenfrequency noise is less than 120 Hz peak to peak, and the radiation pressure induced frequency shift is ..delta..f/f = 1.6 x 10/sup -6/ E/sub a//sup 2/.

Investigation of Pb doping on electrical, structural and superconducting properties of YBa2-xPbxCu3O7-δ superconductors

Science.gov (United States)

Ezzatpour, S.; Sharifzadegan, L.; Sarvari, F.; Sedghi, H.

2018-06-01

In this study the high temperature superconductor YBa2-xPbxCu3O7-δ with doping x = ,0.05,0.1,0.15 were prepared by the standard solid-state reaction method. The effect of Pb substitution on Ba site of YBCO superconducting system, structural, electrical and superconducting properties of Y-based superconductor has been investigated. The measurements of dc resisitivity were performed on all samples with four-probe method using low frequency/lowAC current (4 mA) . The superconducting temperature, Tc, were determined from the resistivity versus temperature (R-T) curves. Results show that Pb doping reduced the cirtical temperature(Tc) and superconductivity properties of our samples. The maximum and the minimum Tc were observed for the samples with x = 0.15 and x = 0.1 respectively. The structure and phase purity of samples were examined by the X-ray powder diffraction technique (XRD) performed by means of D8 Advance Bruker diffractometer with Cu kα radiation. The grain morphology of surface of the samples was analyzed by sacanning electron microscopy (SEM). XRD patterns of polycrystalline materials of composition YBa2-xPbxCu3O7-δ revealed that all prepared samples are orthorhombic. All of the peaks of YBCO and YBa2-xPbxCu3O7-δ have been used for the estimation of volume fractions of the phases and ignored the void peaks.

Four-junction superconducting circuit

Science.gov (United States)

Qiu, Yueyin; Xiong, Wei; He, Xiao-Ling; Li, Tie-Fu; You, J. Q.

2016-01-01

We develop a theory for the quantum circuit consisting of a superconducting loop interrupted by four Josephson junctions and pierced by a magnetic flux (either static or time-dependent). In addition to the similarity with the typical three-junction flux qubit in the double-well regime, we demonstrate the difference of the four-junction circuit from its three-junction analogue, including its advantages over the latter. Moreover, the four-junction circuit in the single-well regime is also investigated. Our theory provides a tool to explore the physical properties of this four-junction superconducting circuit. PMID:27356619

Influence of stresses on superconducting properties of Nb3Sn conductors

International Nuclear Information System (INIS)

Suenaga, M.; Luhman, T.S.; Sampson, W.B.; Onishi, T.; Klamut, C.J.

1978-01-01

This investigation of the degradation in the superconducting properties of Nb 3 Sn conductors when subjected to mechanical strain can be divided into the following areas: (I) monofilamentary Nb 3 Sn wires, (II) multifilamentary Nb 3 Sn conductors and wires, (III) effects of additives to Nb 3 Sn, (IV) mechanisms for degradation, and (V) construction of test facilities. Efforts to the present time have been concentrated in the investigation of T/sub c/, J/sub c/, and H/sub c2/ variations in monofilamentary wires. The most important finding in this study is that a Nb 3 Sn composite wire can sustain an effective mechanical strain well beyond ''1%'' if a proper ratio of the matrix to the Nb core has been chosen

Structural, magnetic and superconducting phase transitions in CaFe2As2 under ambient and applied pressure

International Nuclear Information System (INIS)

Canfield, P.C.; Bud'ko, S.L.; Ni, N.; Kreyssig, A.; Goldman, A.I.; McQueeney, R.J.; Torikachvili, M.S.; Argyriou, D.N.; Luke, G.; Yu, W.

2009-01-01

At ambient pressure CaFe 2 As 2 has been found to undergo a first order phase transition from a high temperature, tetragonal phase to a low-temperature orthorhombic/antiferromagnetic phase upon cooling through T ∼ 170 K. With the application of pressure this phase transition is rapidly suppressed and by ∼0.35 GPa it is replaced by a first order phase transition to a low-temperature collapsed tetragonal, non-magnetic phase. Further application of pressure leads to an increase of the tetragonal to collapsed tetragonal phase transition temperature, with it crossing room temperature by ∼1.7 GPa. Given the exceptionally large and anisotropic change in unit cell dimensions associated with the collapsed tetragonal phase, the state of the pressure medium (liquid or solid) at the transition temperature has profound effects on the low-temperature state of the sample. For He-gas cells the pressure is as close to hydrostatic as possible and the transitions are sharp and the sample appears to be single phase at low temperatures. For liquid media cells at temperatures below media freezing, the CaFe 2 As 2 transforms when it is encased by a frozen media and enters into a low-temperature multi-crystallographic-phase state, leading to what appears to be a strain stabilized superconducting state at low temperatures.

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...

Self-contained high-pressure chambers for study on the Moessbauer effect at low temperatures

International Nuclear Information System (INIS)

Stepanov, G.N.

1980-01-01

Designs of two high-pressure chambers intended for studying the Moessbauer effect at low temperatures are described. The high-pressure chamber of the Bridgman anvil type is made of non magnetic materials and intended for operation at helium temperatures. The chamber employs a superconducting pressure gage. A sample and superconducting pressure gage are surrounded with a liquid medium of a high pressure at a room temperature. Measurements of the pressure were taken during heating the chamber in the vapours of liquid helium according to the known dependence of the lead superconducting transition temperature on pressure. The other high-pressure chamber of the piston-to-cylinder type can be used to study the Moessbauer effect at temperatures ranging from 4 to 300 K. Pressure in the chamber is measured by means of the superconducting pressure gage. The maximum pressure obtained in the chamber constitutes 25 kbar

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

(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......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...

Electronic structure and properties of rare earth and actinide intermetallics

International Nuclear Information System (INIS)

Kirchmayr, H.R.

1984-01-01

There are 188 contributions, experimental and theoretical, a few on rare earth and actinide elements but mostly on rare earth and actinide intermetallic compounds and alloys. The properties dealt with include 1) crystal structure, 2) magnetic properties and magnetic structure, 3) magnetic phase transformations and valence fluctuations, 4) electrical properties and superconductivity and their temperature, pressure and magnetic field dependence. A few papers deal with crystal growth and novel measuring methods. (G.Q.)

Itinerant-electron antiferromagnetism and superconductivity in bcc Cr-Re alloys

International Nuclear Information System (INIS)

Nishihara, Y.; Yamaguchi, Y.; Kohara, T.; Tokumoto, M.

1985-01-01

The magnetic and superconducting properties of bcc Cr-Re alloys with up to 40 at. % Re were studied via measurements of the magnetic susceptibility, electrical resistivity, and nuclear magnetic resonance of the Re nuclei. Antiferromagnetic order coexists with superconductivity above 18 at. % Re. The results were analyzed with the coexistence model of spin-density waves and superconductivity. In the Re-concentration range greater than 18 at. %, about 10% of the Fermi surface satisfies the nesting condition and the rest of it contributes to form the superconducting gap. This model also explains the increase in the superconducting transition temperature and the decrease in the magnetic susceptibility by annealing as a competing effect between spin-density waves and superconductivity

Annealing effect on superconductivity of La2CuO4 single crystals

International Nuclear Information System (INIS)

Tanaka, I.; Takahashi, H.; Kojima, H.

1992-01-01

This paper reports that La 2 CuO 4 single crystals grown at an oxygen pressure of 0.2 MPa by TSFZ method are superconducting below 32 K, and show a semiconducting behavior in nonsuperconducting state. The single crystals of La 2 CuO 4 are changed from superconductors to semiconductors by annealing in argon, and are returned to superconductors by annealing at ambient pressure of oxygen. Therefore, superconductivity of the La 2 CuO 4 single crystals is due to excess oxygen

Annealing effect on superconductivity of La2CuO4 single crystals

International Nuclear Information System (INIS)

Tanaka, L.; Takahashi, H.; Kojima, H.

1992-01-01

La 2 CuO 4 single crystals grown at an oxygen pressure of 0.2 MPa by TSFZ method are superconducting below 32 K, and show a semiconducting behavior in nonsuperconducting state. The single crystals of La 2 CuO 4 are changed from superconductors to semiconductors by annealing in argon, and are returned to superconductors by annealing at ambient pressure of oxygen. Therefore, superconductivity of the La 2 CuO 4 single crystals is due to excess oxygen. (orig.)

Superconductivity and vortex properties in various multilayers

International Nuclear Information System (INIS)

Koorevaar, P.

1994-01-01

In this thesis three qualitatively different type of superconducting multilayers are studied. We discuss the vortex lattice structure in Nb/NbZr multilayers, a system where both type of constituting layers are superconducting. At certain temperatures and for parallel fields close to H c2parallel , the Nb/NbZr system has a strongly modulated order parameter, and in this aspect resembles the high-Tc materials. By lowering the field the modulation decreases, having important consequences for the vortex lattice structure. By studying the transport critical currents we show that in the case of strong modulation the vortex lattice has a kinked structure, but at weaker modulations the vortices are straight, and the change in modulation actually results in a vortex lattice transition. Our study confirms the picture of the existence of kinked vortex lattices, but it is rather surprising that these kinked structures can exist in a system which in itself is not at all that anisotropic. It indicates the relevance of other parameters governing the vortex lattice structure. (orig.)

Electronic structure and superconductivity of MgB2

Indian Academy of Sciences (India)

Unknown

High Pressure Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085, India. Abstract. Results ... compared to the experimentally determined values of these quantities. ... that spectroscopies which probe the superconducting gap.

Quantum Theory of Conducting Matter Superconductivity and Quantum Hall Effect

CERN Document Server

Fujita, Shigeji; Godoy, Salvador

2009-01-01

Explains major superconducting properties including zero resistance, Meissner effect, sharp phase change, flux quantization, excitation energy gap, and Josephson effects using quantum statistical mechanical calculations. This book covers the 2D superconductivity and the quantum Hall effects

Superconductivity in SnO: A Nonmagnetic Analog to Fe-Based Superconductors?

DEFF Research Database (Denmark)

Forthaus, M. K.; Sengupta, K.; Heyer, O.

2010-01-01

We discovered that under pressure SnO with α-PbO structure, the same structure as in many Fe-based superconductors, e.g., β-FeSe, undergoes a transition to a superconducting state for p≳6  GPa with a maximum Tc of 1.4 K at p=9.3  GPa. The pressure dependence of Tc reveals a domelike shape...... and superconductivity disappears for p≳16  GPa. It is further shown from band structure calculations that SnO under pressure exhibits a Fermi surface topology similar to that reported for some Fe-based superconductors and that the nesting between the hole and electron pockets correlates with the change of Tc...

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

High pressure study of high-temperature superconductors

Energy Technology Data Exchange (ETDEWEB)

Souliou, Sofia-Michaela

2014-09-29

Imm2). The structural transition is clearly reflected in the high pressure Raman data through the appearance of several new modes, allowing us to map in detail the (P,T) phase diagram and determine the transition line between the two phases. In the new phase, the renormalization of the buckling mode is completely suppressed, while no anomalies are observed in any of the other Raman active phonons. According to ab initio calculations, the coupling of the buckling mode to the electronic system is not significantly affected by the structural phase transition. The absence of phonon renormalizations in the presence of sizable electron-phonon coupling, indicate that, in contrast to earlier transport studies, YBa{sub 2}Cu{sub 4}O{sub 8} is not superconducting anymore under hydrostatic pressures higher than 10 GPa. Finally we proceeded with the investigation of the high pressure structural and vibrational properties of SmFeAsO, a member of the ''1111'' family (space group P4/nmm) of the Fe-based superconductors, in which superconductivity is commonly induced either by substituting F/H for O or by applying high pressures on the parent magnetic compound. The magnetic transition of the undoped compound is accompanied with a tetragonal-to-orthorhombic structural distortion, both of which are commonly suppressed upon the emergence of superconductivity. In the SmFeAsO{sub x}F{sub 1-x} system while the magnetic transition is totally suppressed already at low doping levels, structural studies have reported either the gradual suppression of the orthorhombic distortion or its retention over a wide regime of the superconducting phase. We addressed this controversy using high pressure as an alternative tuning parameter to suppress the magneto-structural transition and induce superconductivity in the parent compound. Our high pressure, low temperature X-ray diffraction measurements on single crystals of SmFeAsO have revealed that the tetragonal

High pressure study of high-temperature superconductors

International Nuclear Information System (INIS)

Souliou, Sofia-Michaela

2014-01-01

Raman data through the appearance of several new modes, allowing us to map in detail the (P,T) phase diagram and determine the transition line between the two phases. In the new phase, the renormalization of the buckling mode is completely suppressed, while no anomalies are observed in any of the other Raman active phonons. According to ab initio calculations, the coupling of the buckling mode to the electronic system is not significantly affected by the structural phase transition. The absence of phonon renormalizations in the presence of sizable electron-phonon coupling, indicate that, in contrast to earlier transport studies, YBa 2 Cu 4 O 8 is not superconducting anymore under hydrostatic pressures higher than 10 GPa. Finally we proceeded with the investigation of the high pressure structural and vibrational properties of SmFeAsO, a member of the ''1111'' family (space group P4/nmm) of the Fe-based superconductors, in which superconductivity is commonly induced either by substituting F/H for O or by applying high pressures on the parent magnetic compound. The magnetic transition of the undoped compound is accompanied with a tetragonal-to-orthorhombic structural distortion, both of which are commonly suppressed upon the emergence of superconductivity. In the SmFeAsO x F 1-x system while the magnetic transition is totally suppressed already at low doping levels, structural studies have reported either the gradual suppression of the orthorhombic distortion or its retention over a wide regime of the superconducting phase. We addressed this controversy using high pressure as an alternative tuning parameter to suppress the magneto-structural transition and induce superconductivity in the parent compound. Our high pressure, low temperature X-ray diffraction measurements on single crystals of SmFeAsO have revealed that the tetragonal-to-orthorhombic transition survives with the application of high pressures up to 85 kbars. In addition, our Raman data

Stability and fast heat removal with He-II cooling for pulsed superconductive magnets

International Nuclear Information System (INIS)

Desportes, H.

1979-01-01

The use of pressurized superfluid helium between 1.6 K and 1.8 K is being considered for a number of superconducting magnet applications. This type of cooling is particularly interesting in the case of pulsed field magnets where large heat fluxes need to be evacuated in a short time. This paper reviews a few recent experiments on heat transport properties and stability in He-II, which contribute to evaluating its potential use for such an application. Present technology is illustrated by the description of a large test facility recently operated at Saclay

Superconducting cosmic strings in models with spontaneously broken family symmetry

International Nuclear Information System (INIS)

Bibilashvili, T.M.; Dvali, G.R.

1990-01-01

It is shown that superconducting cosmic strings with some specific properties naturally exist in models of spontaneously broken family symmetry. Superconductivity may be of both types - bosonic and fermionic. There exists a possible mechanism of string conservation. (orig.)

Attenuation in Superconducting Circular Waveguides

Directory of Open Access Journals (Sweden)

K. H. Yeap

2016-09-01

Full Text Available We present an analysis on wave propagation in superconducting circular waveguides. In order to account for the presence of quasiparticles in the intragap states of a superconductor, we employ the characteristic equation derived from the extended Mattis-Bardeen theory to compute the values of the complex conductivity. To calculate the attenuation in a circular waveguide, the tangential fields at the boundary of the wall are first matched with the electrical properties (which includes the complex conductivity of the wall material. The matching of fields with the electrical properties results in a set of transcendental equations which is able to accurately describe the propagation constant of the fields. Our results show that although the attenuation in the superconducting waveguide above cutoff (but below the gap frequency is finite, it is considerably lower than that in a normal waveguide. Above the gap frequency, however, the attenuation in the superconducting waveguide increases sharply. The attenuation eventually surpasses that in a normal waveguide. As frequency increases above the gap frequency, Cooper pairs break into quasiparticles. Hence, we attribute the sharp rise in attenuation to the increase in random collision of the quasiparticles with the lattice structure.

Superconducting microtraps for ultracold atoms

International Nuclear Information System (INIS)

Hufnagel, C.

2011-01-01

Atom chips are integrated devices in which atoms and atomic clouds are stored and manipulated in miniaturized magnetic traps. State of the art fabrication technologies allow for a flexible design of the trapping potentials and consequently provide extraordinary control over atomic samples, which leads to a promising role of atom chips in the engineering and investigation of quantum mechanical systems. Naturally, for quantum mechanical applications, the atomic coherence has to be preserved. Using room temperature circuits, the coherence time of atoms close to the surface was found to be drastically limited by thermal current fluctuations in the conductors. Superconductors offer an elegant way to circumvent thermal noise and therefore present a promising option for the coherent manipulation of atomic quantum states. In this thesis trapping and manipulation of ultracold Rubidium atoms in superconducting microtraps is demonstrated. In this connection the unique properties of superconductors are used to build traps based on persistent currents, the Meissner effect and remanent magnetization. In experiment it is shown, that in superconducting atom chips, thermal magnetic field noise is significantly reduced. Furthermore it is demonstrated, that atomic samples can be employed to probe the properties of superconducting materials. (author) [de

Superconductivity of a Sn film controlled by an array of Co nanowires

Science.gov (United States)

Wei, Z.; Ye, Z.; Rathnayaka, K. D. D.; Lyuksyutov, I. F.; Wu, W.; Naugle, D. G.

2012-09-01

Superconducting properties of a hybrid structure composed of ferromagnetic Co nanowire arrays and a superconducting Sn film have been investigated. Ordered Co nanowires arrays with 60 nm, 150 nm and 200 nm diameter were electroplated into the pores of self organized Anodic Aluminum Oxide (AAO) membranes. Hysteretic dependence of the Sn film superconducting properties on applied magnetic field and critical current enhancement at moderate fields has been observed. This behavior strongly depends on the ratio of the Sn film thickness to the Co nanowire diameter.

Superconductivity of a Sn film controlled by an array of Co nanowires

International Nuclear Information System (INIS)

Wei, Z.; Ye, Z.; Rathnayaka, K.D.D.; Lyuksyutov, I.F.; Wu, W.; Naugle, D.G.

2012-01-01

Superconducting properties of a hybrid structure composed of ferromagnetic Co nanowire arrays and a superconducting Sn film have been investigated. Ordered Co nanowires arrays with 60 nm, 150 nm and 200 nm diameter were electroplated into the pores of self organized Anodic Aluminum Oxide (AAO) membranes. Hysteretic dependence of the Sn film superconducting properties on applied magnetic field and critical current enhancement at moderate fields has been observed. This behavior strongly depends on the ratio of the Sn film thickness to the Co nanowire diameter.

Superconductivity in SrNi2P2 single crystals

Energy Technology Data Exchange (ETDEWEB)

Ronning, Filip [Los Alamos National Laboratory; Bauer, Eric D [Los Alamos National Laboratory; Park, Tuscon [Los Alamos National Laboratory; Thompson, Joe D [Los Alamos National Laboratory

2009-01-01

Heat capacity, magnetic susceptibility, and resistivity of SrNi{sub 2}P{sub 2} single crystals are presented, illustrating the structural transition at 325 K, and bulk superconductivity at 1.4 K. The magnitude of {Tc}, fits to the heat capacity data, the small upper critical field H{sub c2} = 390 Oe, and {kappa} = 2.1 suggests a conventional fully gapped superconductor. With applied pressure we find that superconductivity persists into the so-called 'collapsed tetragonal' phase, although the transition temperature is monotonically suppressed with increasing pressure. This argues that reduced dimensionality can be a mechanism for increasing the transition temperatures of layered NiP, as well as layered FeAs and NiAs, superconductors.

Development of innovative superconducting DC power cable

Energy Technology Data Exchange (ETDEWEB)

Matsushita, Teruo; Kiuchi, Masaru [Dept. of Computer Science and Electronics Kyushu Institute of Technology, Iizuka (Japan)

2017-09-15

It is required to reduce the cost of superconducting cable to realize a superconducting DC power network that covers a wide area in order to utilize renewable energy. In this paper a new concept of innovative cable is introduced that can enhance the current-carrying capacity even though the same superconducting tape is used. Such a cable can be realized by designing an optimal winding structure in such a way that the angle between the tape and magnetic field becomes small. This idea was confirmed by preliminary experiments for a single layer model cable made of Bi-2223 tapes and REBCO coated conductors. Experiments of three and four layer cables of practical sizes were also done and it was found that the current-carrying capacity increased as theoretically predicted. If the critical current properties of commercial superconducting tapes are further improved in a parallel magnetic field, the enhancement will become pronounced and this technology will surely contribute to realization of superconducting DC power network.

Structural feature controlling superconductivity in compressed BaFe2As2

International Nuclear Information System (INIS)

Yang, Wenge; Jia, Feng-Jiang; Tang, Ling-Yun; Tao, Qian; Xu, Zhu-An; Chen, Xiao-Jia

2014-01-01

Superconductivity can be induced with the application of pressure but it disappears eventually upon heavy compression in the iron-based parent compound BaFe 2 As 2 . Structural evolution with pressure is used to understand this behavior. By performing synchrotron X-ray powder diffraction measurements with diamond anvil cells up to 26.1 GPa, we find an anomalous behavior of the lattice parameter with a S shape along the a axis but a monotonic decrease in the c-axis lattice parameter with increasing pressure. The close relationship between the axial ratio c/a and the superconducting transition temperature T c is established for this parent compound. The c/a ratio is suggested to be a measure of the spin fluctuation strength. The reduction of T c with the further increase of pressure is a result of the pressure-driven weakness of the spin-fluctuation strength in this material

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.

Effects of high-energy proton irradiation on the superconducting properties of Fe(Se,Te) thin films

Science.gov (United States)

Sylva, G.; Bellingeri, E.; Ferdeghini, C.; Martinelli, A.; Pallecchi, I.; Pellegrino, L.; Putti, M.; Ghigo, G.; Gozzelino, L.; Torsello, D.; Grimaldi, G.; Leo, A.; Nigro, A.; Braccini, V.

2018-05-01

In this paper we explore the effects of 3.5 MeV proton irradiation on Fe(Se,Te) thin films grown on CaF2. In particular, we carry out an experimental investigation with different irradiation fluences up to 7.30 · 1016 cm‑2 and different proton implantation depths, in order to clarify whether and to what extent the critical current is enhanced or suppressed, what are the effects of irradiation on the critical temperature, resistivity, and critical magnetic fields, and finally what is the role played by the substrate in this context. We find that the effect of irradiation on superconducting properties is generally small compared to the case of other iron-based superconductors. The irradiation effect is more evident on the critical current density Jc, while it is minor on the transition temperature Tc, normal state resistivity ρ, and on the upper critical field Hc2 up to the highest fluences explored in this work. In more detail, our analysis shows that when protons implant in the substrate far from the superconducting film, the critical current can be enhanced up to 50% of the pristine value at 7 T and 12 K; meanwhile, there is no appreciable effect on critical temperature and critical fields together with a slight decrease in resistivity. On the contrary, when the implantation layer is closer to the film–substrate interface, both critical current and temperature show a decrease accompanied by an enhancement of the resistivity and lattice strain. This result evidences that possible modifications induced by irradiation in the substrate may affect the superconducting properties of the film via lattice strain. The robustness of the Fe(Se,Te) system to irradiation-induced damage makes it a promising compound for the fabrication of magnets in high-energy accelerators.

Second international Israeli conference on High Tc Superconductivity

International Nuclear Information System (INIS)

1993-01-01

The superconductivity fields covered in this conference are: theory, applications, devices, flux properties high frequencies, Josephson junctions, magnetism, material sciences and physical properties of superconductors, spectroscopy and resonances and thin films

Superconductivity in the periodic Anderson model with anisotropic hybridization

International Nuclear Information System (INIS)

Sarasua, L.G.; Continentino, Mucio A.

2003-01-01

In this work we study superconductivity in the periodic Anderson model with both on-site and intersite hybridization, including the interband Coulomb repulsion. We show that the presence of the intersite hybridization together with the on-site hybridization significantly affects the superconducting properties of the system. The symmetry of the hybridization has a strong influence in the symmetry of the superconducting order parameter of the ground state. The interband Coulomb repulsion may increase or decrease the superconducting critical temperature at small values of this interaction, while is detrimental to superconductivity for strong values. We show that the present model can give rise to positive or negative values of dT c /dP, depending on the values of the system parameters

Superconductivity in the background of disordered flux state of spins

International Nuclear Information System (INIS)

Feng Shiping; Guo Rui; Han Fei

1992-01-01

The phase diagram of the copper oxide materials with the antiferromagnetic and the superconducting properties as a function of doping δ is obtained in the framework of the t-J model by using the Schwinger boson-slave fermion theory. The results show that the spiral order of spins competes and coexists with superconductivity for small doping δ. For large doping δ, superconductivity appears, which may be caused by the occurrence of a disordered flux state of spins. The phase diagram suggests a strong relationship between antiferromagnetism and superconductivity. (orig.)

Advances in high pressure research in condensed matter: proceedings of the international conference on condensed matter under high pressures

International Nuclear Information System (INIS)

Sikka, S.K.; Gupta, Satish C.; Godwal, B.K.

1997-01-01

The use of pressure as a thermodynamic variable for studying condensed matter has become very important in recent years. Its main effect is to reduce the volume of a substance. Thus, in some sense, it mimics the phenomena taking place during the cohesion of solids like pressure ionization, modifications in electronic properties and phase changes etc. Some of the phase changes under pressure lead to synthesis of new materials. The recent discovery of high T c superconductivity in YBa 2 Cu 3 O 7 may be indirectly attributed to the pressure effect. In applied fields like simulation of reactor accident, design of inertial confinement fusion schemes and for understanding the rock mechanical effects of shock propagation in earth due to underground nuclear explosions, the pressure versus volume relations of condensed matter are a vital input. This volume containing the proceedings of the International Conference on Condensed Matter Under High Pressure covers various aspects of high pressure pertaining to equations of state, phase transitions, electronic, optical and transport properties of solids, atomic and molecular studies, shock induced reactions, energetic materials, materials synthesis, mineral physics, geophysical and planetary sciences, biological applications and food processing and advances in experimental techniques and numerical simulations. Papers relevant to INIS are indexed separately

Enhanced flux pinning properties in superconducting YBa2Cu3O7−z films by a novel chemical doping approach

International Nuclear Information System (INIS)

Wang, W.T.; Pu, M.H.; Lei, M.; Zhang, H.; Wang, Z.; Zhang, H.; Cheng, C.H.; Zhao, Y.

2013-01-01

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 2 Cu 3 O 7−z (YBCO) films were prepared on (0 0 l) LaAlO 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 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

High temperature superconducting material: Bismuth strontium calcium copper oxide. (Latest citations from the Aerospace database). Published Search

International Nuclear Information System (INIS)

1993-11-01

The bibliography contains citations concerning the development, fabrication, and analysis of a high temperature superconducting material based on bismuth-strontium-calcium-copper-oxides (Bi-Sr-Ca-Cu-O). Topics include the physical properties, structural and compositional analysis, magnetic field and pressure effects, and noble metal dopings of Bi-Sr-Ca-Cu-O based systems. The highest transition temperature recorded to date for this material was 120 degrees Kelvin. Fabrication methods and properties of Bi-Sr-Ca-Cu-O films and ceramics are also considered. (Contains 250 citations and includes a subject term index and title list.)

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.

Superconductivity in doped semiconductors

Energy Technology Data Exchange (ETDEWEB)

Bustarret, E., E-mail: Etienne.bustarret@neel.cnrs.fr

2015-07-15

A historical survey of the main normal and superconducting state properties of several semiconductors doped into superconductivity is proposed. This class of materials includes selenides, tellurides, oxides and column-IV semiconductors. Most of the experimental data point to a weak coupling pairing mechanism, probably phonon-mediated in the case of diamond, but probably not in the case of strontium titanate, these being the most intensively studied materials over the last decade. Despite promising theoretical predictions based on a conventional mechanism, the occurrence of critical temperatures significantly higher than 10 K has not been yet verified. However, the class provides an enticing playground for testing theories and devices alike.

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.

Superconductivity

International Nuclear Information System (INIS)

Onnes, H.K.

1988-01-01

The author traces the development of superconductivity from 1911 to 1986. Some of the areas he explores are the Meissner Effect, theoretical developments, experimental developments, engineering achievements, research in superconducting magnets, and research in superconducting electronics. The article also mentions applications shown to be technically feasible, but not yet commercialized. High-temperature superconductivity may provide enough leverage to bring these applications to the marketplace

Prediction of high-Tc conventional superconductivity in the ternary lithium borohydride system

Science.gov (United States)

Kokail, Christian; von der Linden, Wolfgang; Boeri, Lilia

2017-12-01

We investigate the superconducting ternary lithium borohydride phase diagram at pressures of 0 and 200 GPa using methods for evolutionary crystal structure prediction and linear-response calculations for the electron-phonon coupling. Our calculations show that the ground state phase at ambient pressure, LiBH4, stays in the P n m a space group and remains a wide band-gap insulator at all pressures investigated. Other phases along the 1 :1 :x Li:B:H line are also insulating. However, a full search of the ternary phase diagram at 200 GPa revealed a metallic Li2BH6 phase, which is thermodynamically stable down to 100 GPa. This superhydride phase, crystallizing in a F m 3 ¯m space group, is characterized by sixfold hydrogen-coordinated boron atoms occupying the fcc sites of the unit cell. Due to strong hydrogen-boron bonding this phase displays a critical temperature of ˜100 K between 100 and 200 GPa. Our investigations confirm that ternary compounds used in hydrogen-storage applications should exhibit high-Tc conventional superconductivity in diamond anvil cell experiments, and suggest a viable route to optimize the superconducting behavior of high-pressure hydrides, exploiting metallic covalent bonds.

Superconductivity

International Nuclear Information System (INIS)

Andersen, N.H.; Mortensen, K.

1988-12-01

This report contains lecture notes of the basic lectures presented at the 1st Topsoee Summer School on Superconductivity held at Risoe National Laboratory, June 20-24, 1988. The following lecture notes are included: L.M. Falicov: 'Superconductivity: Phenomenology', A. Bohr and O. Ulfbeck: 'Quantal structure of superconductivity. Gauge angle', G. Aeppli: 'Muons, neutrons and superconductivity', N.F. Pedersen: 'The Josephson junction', C. Michel: 'Physicochemistry of high-T c superconductors', C. Laverick and J.K. Hulm: 'Manufacturing and application of superconducting wires', J. Clarke: 'SQUID concepts and systems'. (orig.) With 10 tabs., 128 figs., 219 refs

Synthesis and superconducting properties of niobium germanium

International Nuclear Information System (INIS)

Kihlstrom, K.E.

1982-01-01

By carefully controlling temperature homogeneity during preparation of the Nb 3 Ge samples, homogeneous films have been prepared of high-T/sub c/Nb 3 Ge. Homogeneity is demonstrated by a sharp transition width (ΔT/sub c/ 6 amps/cm 2 which are the highest ever reported for any material at this temperature. The successful film synthesis has made it possible to study the superconducting properties of Nb 3 Ge. High quality A15 NbGe/(SiO/sub x/)/Pb tunnel juctions on electron beam codeposited oxygen-doped Nb 3 Ge have been fabricated. 2Δ/(k/sub B/T/sub c/ rises from the BCS limit in Ge-poor samples to become strong coupled (2Δk/sub B/T/sub c/ approx. 4.35) as stoichiometry is approached. The electron-phonon spectral function α 2 F(ω) and related microscopic parameters were obtained. As the T/sub c/ and gap increase, a movement of the lowest phonon branch to lower energies is observed with a resultant decrease in (ω 2 ). Thus lambda increases with T/sub c/ while (ω 2 ) decreases in agreement with the idea that mode softening is a major factor in the increase of T/sub c/ with approach to stoichiometry as previously found in Nb 3 Al by Kwo and Geballe

Superconducting microphone for photoacoustic spectroscopy

International Nuclear Information System (INIS)

Ribeiro, P.C.; Labrunie, M.; Weid, J.P. von der; Symko, O.G.

1982-07-01

A superconducting microphone has been developed for photoacoustic spectroscopy at low temperatures. The microphone consists of a thin mylar membrane coated with a film of lead whose motion is detected by a SQUID magnetometer. For the simple set-up presented here, the limiting pressure sensitivity is 7.5x10 -14 atmospheres/√Hz. (Author) [pt

Ceramic/metal and A15/metal superconducting composite materials exploiting the superconducting proximity effect and method of making the same

International Nuclear Information System (INIS)

Holcomb, M.J.

1999-01-01

A composite superconducting material made of coated particles of ceramic superconducting material and a metal matrix material is disclosed. The metal matrix material fills the regions between the coated particles. The coating material is a material that is chemically nonreactive with the ceramic. Preferably, it is silver. The coating serves to chemically insulate the ceramic from the metal matrix material. The metal matrix material is a metal that is susceptible to the superconducting proximity effect. Preferably, it is a NbTi alloy. The metal matrix material is induced to become superconducting by the superconducting proximity effect when the temperature of the material goes below the critical temperature of the ceramic. The material has the improved mechanical properties of the metal matrix material. Preferably, the material consists of approximately 10% NbTi, 90% coated ceramic particles (by volume). Certain aspects of the material and method will depend upon the particular ceramic superconductor employed. An alternative embodiment of the invention utilizes A15 compound superconducting particles in a metal matrix material which is preferably a NbTi alloy

Ceramic/metal and A15/metal superconducting composite materials exploiting the superconducting proximity effect and method of making the same

Science.gov (United States)

Holcomb, Matthew J.

1999-01-01

A composite superconducting material made of coated particles of ceramic superconducting material and a metal matrix material. The metal matrix material fills the regions between the coated particles. The coating material is a material that is chemically nonreactive with the ceramic. Preferably, it is silver. The coating serves to chemically insulate the ceramic from the metal matrix material. The metal matrix material is a metal that is susceptible to the superconducting proximity effect. Preferably, it is a NbTi alloy. The metal matrix material is induced to become superconducting by the superconducting proximity effect when the temperature of the material goes below the critical temperature of the ceramic. The material has the improved mechanical properties of the metal matrix material. Preferably, the material consists of approximately 10% NbTi, 90% coated ceramic particles (by volume). Certain aspects of the material and method will depend upon the particular ceramic superconductor employed. An alternative embodiment of the invention utilizes A15 compound superconducting particles in a metal matrix material which is preferably a NbTi alloy.

Superconductivity: materials and applications; La supraconductivite: materiaux et apllications

Energy Technology Data Exchange (ETDEWEB)

Duchateau, J.L. [CEA Cadarache, 13 - Saint Paul lez Durance (France); Kircher, F. [CEA Saclay, 91 - Gif sur Yvette (France); Leveque, J. [Groupe de Recherche en Electrotechnique et Electronique de Nancy, GREEN - UHP, 54 - Vandoeuvre les Nancy (France); Tixador, P. [INP/Institut Neel, 38 - Grenoble (France)

2008-07-01

This digest paper presents the different types of superconducting materials: 1 - the low-TC superconductors: the multi-filament composite as elementary constituent, the world production of NbTi, the superconducting cables of the LHC collider and of the ITER tokamak; 2 - the high-TC superconductors: BiSrCaCuO (PIT 1G) ribbons and wires, deposited coatings; 3 - application to particle physics: the the LHC collider of the CERN, the LHC detectors; 4 - applications to thermonuclear fusion: Tore Supra and ITER tokamaks; 5 - NMR imaging: properties of superconducting magnets; 6 - applications in electrotechnics: cables, motors and alternators, current limiters, transformers, superconducting energy storage systems (SMES). (J.S.)

Quasiparticles in the superconducting state of high-Tc metals

International Nuclear Information System (INIS)

Amusia, M.Ya.; Shaginyan, V.R.

2003-01-01

The behavior of quasiparticles in the superconducting state of high-T c metals within the framework of the theory of superconducting state based on the fermion condensation quantum phase transition is considered. It is shown that the behavior coincides with the behavior of Bogoliubov quasiparticles, whereas the maximum value of the superconducting gap and other exotic properties are determined by the presence of the fermion condensate. If at low temperatures the normal state is recovered by the application of a magnetic field suppressing the superconductivity, the induced state can be viewed as Landau-Fermi liquid. These observations are in good agreement with recent experimental facts [ru

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

International Nuclear Information System (INIS)

Kim, S.B.; Uwani, Y.; Joo, J.H.; Kawamoto, R.; Jo, Y.S.

2011-01-01

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.

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

Magnetism and superconductivity in Eu(Ho)Mo6S8

International Nuclear Information System (INIS)

Capone, D.W. II; Lai Fook, M.S.; Guertin, R.P.; Hinks, D.G.; Dunlap, B.D.; Foner, S.; Abou-Aly, A.I.; Brooks, J.S.

1984-10-01

A variety of ambient and high pressure experimental results reveal the interplay between magnetism and superconductivity in Ho doped samples of the pressure induced superconductor, EuMo 6 S 8 . Ho concentrations up to 50 atomic percent of the rare earth ions were used. High resolution magnetic measurements are consistent with the crystalline electric field ground state for the Ho 3+ ions being a magnetic doublet consisting largely of J/sub z/ = 18. The results of high pressure magnetization experiments reveal negligible effects of reduced lattice constant on the rare earth-rare earth interactions. Resistivity in a 10 atomic percent sample for P = 10 kbar shows the suppression of a P = 0 structural transition, metallic conductivity down to low temperatures, and finally superconductivity at 8 K. The upper critical field, H/sub c2/(T), for this sample was measured for P = 7, 10 and 12 kbar and showed strong reentrant behavior (dH/sub c2/(T)/dT > 0 as T → 0 K). A minimum with field in the resistivity above H/sub c2/ was also observed at lowest temperatures. The H/sub c2/(T) data are compared with those of EuMo 6 S 8 at high pressure, which shows positive curvature, and HoMo 6 S 8 , in which superconductivity is quenched by ferromagnetism at low temperatures. 14 references, 4 figures

Degradation of superconducting Nb/NbN films by atmospheric oxidation

Energy Technology Data Exchange (ETDEWEB)

Henry, Michael David; Wolfley, Steven L.; Young, Travis Ryan; Monson, Todd; Pearce, Charles Joseph; Lewis, Rupert M.; Clark, Blythe; Brunke, Lyle Brent; Missert, Nancy A.

2017-03-01

Niobium and niobium nitride thin films are transitioning from fundamental research toward wafer scale manufacturing with technology drivers that include superconducting circuits and electronics, optical single photon detectors, logic, and memory. Successful microfabrication requires precise control over the properties of sputtered superconducting films, including oxidation. Previous work has demonstrated the mechanism in oxidation of Nb and how film structure could have deleterious effects upon the superconducting properties. This study provides an examination of atmospheric oxidation of NbN films. By examination of the room temperature sheet resistance of NbN bulk oxidation was identified and confirmed by secondary ion mass spectrometry. As a result, Meissner magnetic measurements confirmed the bulk oxidation not observed with simple cryogenic resistivity measurements.

Ab initio Eliashberg Theory: Making Genuine Predictions of Superconducting Features

Science.gov (United States)

Sanna, Antonio; Flores-Livas, José A.; Davydov, Arkadiy; Profeta, Gianni; Dewhurst, Kay; Sharma, Sangeeta; Gross, E. K. U.

2018-04-01

We present an application of Eliashberg theory of superconductivity to study a set of novel superconducting systems with a wide range of structural and chemical properties. The set includes three intercalated group-IV honeycomb layered structures, SH3 at 200 GPa (the superconductor with the highest measured critical temperature), the similar system SeH3 at 150 GPa, and a lithium doped mono-layer of black phosphorus. The theoretical approach we adopt is a recently developed, fully ab initio Eliashberg approach that takes into account the Coulomb interaction in a full energy-resolved fashion avoiding any free parameters like μ*. This method provides reasonable estimations of superconducting properties, including TC and the excitation spectra of superconductors.

Ab-initio calculations of superconducting properties of YBa2Cu3O7

International Nuclear Information System (INIS)

Zhao, G.L.; Bagayoko, D.

1999-01-01

The authors present ab-initio calculations for the electronic structure and superconducting properties of YBa 2 Cu 3 O 7 (YBCO). The electronic structure was calculated using a self-consistent ab-initio LCAO method. They solved the anisotropic Eliashberg gap equation numerically. The strong coupling of the high energy optical phonons around 60--73 meV, with the electrons at the Fermi surface, leads to a high Tc in YBCO. The calculated Tc is about 89 K for μ* = 0.1. The good agreement of the calculated results with experimental measurements and the ab-initio nature of the calculations support the scenario of an anisotropic s-wave superconductor for YBCO

Interface-Induced Zeeman-Protected Superconductivity in Ultrathin Crystalline Lead Films

Science.gov (United States)

Liu, Yi; Wang, Ziqiao; Zhang, Xuefeng; Liu, Chaofei; Liu, Yongjie; Zhou, Zhimou; Wang, Junfeng; Wang, Qingyan; Liu, Yanzhao; Xi, Chuanying; Tian, Mingliang; Liu, Haiwen; Feng, Ji; Xie, X. C.; Wang, Jian

2018-04-01

Two-dimensional (2D) superconducting systems are of great importance for exploring exotic quantum physics. The recent development of fabrication techniques has stimulated studies of high-quality single-crystalline 2D superconductors, where intrinsic properties give rise to unprecedented physical phenomena. Here, we report the observation of Zeeman-type spin-orbit interaction protected superconductivity (Zeeman-protected superconductivity) in 4-monolayer (ML) to 6-ML crystalline Pb films grown on striped incommensurate Pb layers on Si(111) substrates by molecular beam epitaxy. An anomalously large in-plane critical field far beyond the Pauli limit is detected, which can be attributed to the Zeeman-protected superconductivity due to the in-plane inversion symmetry breaking at the interface. Our work demonstrates that, in superconducting heterostructures, the interface can induce Zeeman-type spin-orbit interactions and modulate the superconductivity.

Dependence of temperature-dependent electrical resistivity of SrIrO3 on hydrostatic pressure to 9.1 kbar

International Nuclear Information System (INIS)

Foroozani, N.; Lim, J.; Li, L.; Cao, G.; Schilling, J.S.

2013-01-01

Non-Fermi-liquid behavior and close proximity to a quantum critical point in the 5d transition metal iridate SrIrO 3 at ambient pressure motivate our search for possible anomalous behavior in its transport properties under pressure. The electrical resistivity in the ab-plane of a single crystal of SrIrO 3 has been measured over the temperature range 1.35–285 K at both ambient and 9.1 kbar hydrostatic pressure. The resistivity decreases slightly over the entire temperature range, but no superconducting transition or changes in the non-Fermi-liquid behavior are observed under pressure. It is estimated that significantly higher pressures are likely required before sizable changes in the properties of SrIrO 3 will occur.

Cryogenic properties of austenitic stainless steels for superconducting magnet

International Nuclear Information System (INIS)

Nohara, K.; Kato, T.; Ono, Y.; Sasaki, T.; Suzuki, S.

1983-01-01

The present study examines the magnetic and mechanical properties of a variety of austenitic stainless steels and high maganese steel which are candidate materials for the superconducting magnet attached to high energy particle accelerators. The effect of a specified heat treatment for the precipitation of intermetallic compound Nb3Sn to be used as superconductor on ductility and toughness are especially examined. It is found that nitrogen-strengthened austenitic stainless steels have high strength and good ductility and toughness, but that these are destroyed by precipitation treatment. The poor ductility and toughness after precipitation are caused by a weakening of the grain boundaries due to the agglomerated chromium carbide percipitates. The addition of vanadium suppresses this effect by refining the grain. Austenitic steels are found to have low magnetic permeabilities and Neel temperatures, and show serrated flow in traction test due to strained martensitic transformation. High manganese steel has extremely low permeability, a Neel temperature about room temperature, and has a serrated flow in traction test due to adiabatic deformation at liquid helium temperature

Theory of superconductivity

International Nuclear Information System (INIS)

Crisan, M.

1988-01-01

This book discusses the most important aspects of the theory. The phenomenological model is followed by the microscopic theory of superconductivity, in which modern formalism of the many-body theory is used to treat most important problems such as superconducting alloys, coexistence of superconductivity with the magnetic order, and superconductivity in quasi-one-dimensional systems. It concludes with a discussion on models for exotic and high temperature superconductivity. Its main aim is to review, as complete as possible, the theory of superconductivity from classical models and methods up to the 1987 results on high temperature superconductivity. Contents: Phenomenological Theory of Superconductivity; Microscopic Theory of Superconductivity; Theory of Superconducting Alloys; Superconductors in a Magnetic Field; Superconductivity and Magnetic Order; Superconductivity in Quasi-One-Dimensional Systems; and Non-Conventional Superconductivity

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

Exploring the physics of superconducting qubits strongly coupled to microwave frequency photons

Energy Technology Data Exchange (ETDEWEB)

Wallraff, Andreas [ETH Zurich (Switzerland)

2013-07-01

Using modern micro and nano-fabrication techniques combined with superconducting materials we realize electronic circuits the properties of which are governed by the laws of quantum mechanics. In such circuits the strong interaction of photons with superconducting quantum two-level systems allows us to probe fundamental quantum properties of light and to develop components for applications in quantum information technology. Here, I present experiments in which we have created and probed entanglement between stationary qubits and microwave photons freely propagating down a transmission line. In these experiments we use superconducting parametric amplifiers realized in our lab to detect both qubit and photon states efficiently. Using similar techniques we aim at demonstrating a deterministic scheme for teleportation of quantum states in a macroscopic system based on superconducting circuits.

Case Studies on Superconducting Magnets for Particle Accelerators

International Nuclear Information System (INIS)

Ferracin, P

2014-01-01

During the CERN Accelerator School 'Superconductivity for accelerators', the students were divided into 18 groups, and 6 different exercises (case studies), involving the design and analysis of superconducting magnets and RF cavities, were assigned. The problems covered a broad spectrum of topics, from properties of superconducting materials to operation conditions and general dimensions of components. The work carried out by the students turned out to be an extremely useful opportunity to review the material explained during the lectures, to become familiar with the orders of magnitude of the key parameters, and to understand and compare different design options. We provide in this paper a summary of the activities related to the case studies on superconducting magnets and present the main outcomes

Case Studies on Superconducting Magnets for Particle Accelerators

Energy Technology Data Exchange (ETDEWEB)

Ferracin, P [European Organization for Nuclear Research, Geneva (Switzerland)

2014-07-01

During the CERN Accelerator School 'Superconductivity for accelerators', the students were divided into 18 groups, and 6 different exercises (case studies), involving the design and analysis of superconducting magnets and RF cavities, were assigned. The problems covered a broad spectrum of topics, from properties of superconducting materials to operation conditions and general dimensions of components. The work carried out by the students turned out to be an extremely useful opportunity to review the material explained during the lectures, to become familiar with the orders of magnitude of the key parameters, and to understand and compare different design options. We provide in this paper a summary of the activities related to the case studies on superconducting magnets and present the main outcomes.

Midwest Superconductivity Consortium: 1995 Progress report

Energy Technology Data Exchange (ETDEWEB)

NONE

1996-01-01

The mission of the Midwest Superconductivity Consortium, MISCON, is to advance the science and understanding of high Tc superconductivity. During the past year, 26 projects produced over 133 talks and 127 publications. Three Master`s Degrees and 9 Doctor`s of Philosophy Degrees were granted to students working on MISCON projects. Group activities and interactions involved 2 MISCON group meetings (held in January and July); the third MISCON Summer School held in July; 12 external speakers; 81 collaborations (with universities, industry, Federal laboratories, and foreign research centers); and 54 exchanges of samples and/or measurements. Research achievements this past year focused on understanding the effects of processing phenomena on structure-property interrelationships and the fundamental nature of transport properties in high-temp superconductors.

Midwest Superconductivity Consortium: 1995 Progress report

International Nuclear Information System (INIS)

1996-01-01

The mission of the Midwest Superconductivity Consortium, MISCON, is to advance the science and understanding of high Tc superconductivity. During the past year, 26 projects produced over 133 talks and 127 publications. Three Master's Degrees and 9 Doctor's of Philosophy Degrees were granted to students working on MISCON projects. Group activities and interactions involved 2 MISCON group meetings (held in January and July); the third MISCON Summer School held in July; 12 external speakers; 81 collaborations (with universities, industry, Federal laboratories, and foreign research centers); and 54 exchanges of samples and/or measurements. Research achievements this past year focused on understanding the effects of processing phenomena on structure-property interrelationships and the fundamental nature of transport properties in high-temp superconductors

Thermal propagation and stability in superconducting films

International Nuclear Information System (INIS)

Gray, K.E.; Kampwirth, R.T.; Zasadzinski, J.F.; Ducharme, S.P.

1983-01-01

Thermal propagation and stable hot spots (normal domains) are studied in various high Tsub(c) superconducting films (Nb 3 Sn, Nb, NbN and Nb 3 Ge). A new energy balance is shown to give reasonable quantitative agreement of the dependence of the propagation velocity on the length of short normal domains. The steady state (zero velocity) measurements indicate the existence of two distinct situations for films on high thermal conductivity (sapphire) substrates. For low power per unit area the film and substrate have the same temperature, and the thermal properties of the substrate dominate. However, for higher power densities in short hot spots, the coupling is relatively weak and the thermal properties of the film alone are important. Here a connection is made between the critical current stability of superconducting films and a critical hot spot size for thermal propagation. As a result efficient heat removal is shown to dominate the stabilisation of superconducting films. The strong and weak coupling situations also lead to modifications of the models for propagation velocities on sapphire substrates. Self-healing of hot spots and other phenomena in superconducting film are explained. The potential use of the thermal propagation model in applications of superconductors, especially switches is discussed. (author)

Pressure dependence of magnetic ordering temperatures of rare earth-Sn/sub 3/ compounds

Energy Technology Data Exchange (ETDEWEB)

Foner, S [Massachusetts Inst. of Tech., Cambridge (USA). Francis Bitter National Magnet Lab.

1979-12-01

Measurements of the hydrostatic pressure dependence of the Neel temperatures, Tsub(N), are reported for PrSn/sub 3/, NdSn/sub 3/, GdSn/sub 3/ and CeIn/sub 3/. Tsub(N) is found to increase with applied pressure for PrSn/sub 3/ and NdSn/sub 3/, whereas Tsub(N) is pressure independent within experimental error for GdSn/sub 3/ and CeIn/sub 3/. Slightly Sn-deficient RESn/sub 3/ (RE = rare earth) compounds are found consistently to be weakly ferromagnetic. The physical properties of the RESn/sub 3/ compounds exhibit analogies with the corresponding properties of dilute superconducting (LaRE)Sn/sub 3/ alloys. The high pressure data for PrSn/sub 3/ and CeIn/sub 3/ are qualitatively consistent with a 'Kondo necklace' model for magnetically ordered RE compounds with unstable 4f shells.

Pressure dependence of magnetic ordering temperatures of rare earth - Sn/sub 3/ compounds

Energy Technology Data Exchange (ETDEWEB)

DeLong, L E [Virginia Univ., Charlottesville (USA). Dept. of Physics; Guertin, R P; Foner, S

1979-12-01

Measurements of the hydrostatic pressure dependence of the Neel temperatures, Tsub(N), are reported for PrSn/sub 3/, NdSn/sub 3/, GdSn/sub 3/ and CeIn/sub 3/. Tsub(N) is found to increase with applied pressure for PrSn/sub 3/ and NdSn/sub 3/, whereas Tsub(N) is pressure independent within experimental error for GdSn/sub 3/ and CeIn/sub 3/. Slightly Sn-deficient RESn/sub 3/ (RE=rare earth) compounds are found consistently to be weakly ferromagnetic. The physical properties of the RESn/sub 3/ compounds exhibit analogies with the corresponding properties of dilute superconducting (LaRE)Sn/sub 3/ alloys. The high pressure data for PrSn/sub 3/ and CeIn/sub 3/ are qualitatively consistent with a 'Kondo necklace' model for magnetically ordered RE compounds with unstable 4f shells.

Investigation on lattice parameters and superconducting properties in Fe(Te, Se, S) ternary-chalcogen system

Energy Technology Data Exchange (ETDEWEB)

Guo, Zhongnan; Zhang, Huanhuan; Han, Bingling; Yuan, Wenxia, E-mail: wxyuanwz@163.com

2015-02-15

Highlights: • A series sample of Fe{sub 1.02}Te{sub 0.85}Se{sub 0.15−x}S{sub x} has been synthesised. • The lattice parameters is basically unchanged with the S doping. • The superconductivity is clearly suppressed with the S substitution of Se. • The solid solubility region of the tetragonal phase in this system is discussed. - Abstract: A series of samples with the nominal compositions Fe{sub 1.02}Te{sub 0.85}Se{sub 0.15−x}S{sub x} (x = 0, 0.0375, 0.075, 0.1125 and 0.15) have been synthesized to study the influence of the S substitution of Se on the lattice parameters and superconducting properties. It has been found that the S substitution basically has no effect on the lattice parameters a and c of the tetragonal phase. However, T{sub c} of Fe{sub 1.02}(Te{sub 0.85}Se{sub 0.15−x}S{sub x}) superconductors clearly decreases with S doping.

Magnetic levitation using high temperature superconducting pancake coils as composite bulk cylinders

International Nuclear Information System (INIS)

Patel, A; Hopkins, S C; Baskys, A; Glowacki, B A; Kalitka, V; Molodyk, A

2015-01-01

Stacks of superconducting tape can be used as composite bulk superconductors for both trapped field magnets and for magnetic levitation. Little previous work has been done on quantifying the levitation force behavior between stacks of tape and permanent magnets. This paper reports the axial levitation force properties of superconducting tape wound into pancake coils to act as a composite bulk cylinder, showing that similar stable forces to those expected from a uniform bulk cylinder are possible. Force creep was also measured and simulated for the system. The geometry tested is a possible candidate for a rotary superconducting bearing. Detailed finite element modeling in COMSOL Multiphysics was also performed including a full critical state model for induced currents, with temperature and field dependent properties and 3D levitation force models. This work represents one of the most complete levitation force modeling frameworks yet reported using the H-formulation and helps explain why the coil-like stacks of tape are able to sustain levitation forces. The flexibility of geometry and consistency of superconducting properties offered by stacks of tapes, make them attractive for superconducting levitation applications. (paper)