On Pokrovskii's anisotropic gap equations in superconductivity theory

Science.gov (United States)

Yang, Yisong

2003-11-01

An existence and uniqueness theorem for Pokrovskii's zero-temperature anisotropic gap equation is proved. Furthermore, it is shown that Pokrovskii's finite-temperature equation is inconsistent with the Bardeen-Cooper-Schrieffer (BCS) theory. A reformulation of the anisotropic gap equation is presented along the line of Pokrovskii and it is shown that the new equation is consistent with the BCS theory for the whole temperature range. As an application, the Markowitz-Kadanoff model for anisotropic superconductivity is considered and a rigorous proof of the half-integer-exponent isotope effect is obtained. Furthermore, a sharp estimate of the gap solution near the transition temperature is established.

Direct observation of superconducting gaps in MgB 2 by angle-resolved photoemission spectroscopy

Science.gov (United States)

Souma, S.; Machida, Y.; Sato, T.; Takahashi, T.; Matsui, H.; Wang, S.-C.; Ding, H.; Kaminski, A.; Campuzano, J. C.; Sasaki, S.; Kadowaki, K.

2004-08-01

High-resolution angle-resolved photoemission spectroscopy has been carried out to clarify the anomalous superconductivity of MgB 2. We observed three bands crossing the Fermi level, which are ascribed to B2p-σ, π and surface bands. We have succeeded for the first time in directly observing the superconducting gaps of these bands separately. We have found that the superconducting-gap sizes of σ and surface bands are 6.5 ± 0.5 and 6.0 ± 0.5 meV, respectively, while that of the π band is much smaller (1.5 ± 0.5 meV). The present experimental result unambiguously demonstrates the validity of the two-band superconductivity in MgB 2.

Direct observation of superconducting gaps in MgB2 by angle-resolved photoemission spectroscopy

International Nuclear Information System (INIS)

Souma, S.; Machida, Y.; Sato, T.; Takahashi, T.; Matsui, H.; Wang, S.-C.; Ding, H.; Kaminski, A.; Campuzano, J.C.; Sasaki, S.; Kadowaki, K.

2004-01-01

High-resolution angle-resolved photoemission spectroscopy has been carried out to clarify the anomalous superconductivity of MgB 2 . We observed three bands crossing the Fermi level, which are ascribed to B2p-σ, π and surface bands. We have succeeded for the first time in directly observing the superconducting gaps of these bands separately. We have found that the superconducting-gap sizes of σ and surface bands are 6.5 ± 0.5 and 6.0 ± 0.5 meV, respectively, while that of the π band is much smaller (1.5 ± 0.5 meV). The present experimental result unambiguously demonstrates the validity of the two-band superconductivity in MgB 2

Gas sensing performance at room temperature of nanogap interdigitated electrodes for detection of acetone at low concentration

NARCIS (Netherlands)

Minh, Q. Nguyen; Tong, H.D.; Kuijk, A.; van de Bent, F.; Beekman, Pepijn; Van Rijn, C. J.M.

2017-01-01

A facile approach for the fabrication of large-scale interdigitated nanogap electrodes (nanogap IDEs) with a controllable gap was demonstrated with conventional micro-fabrication technology to develop chemocapacitors for gas sensing applications. In this work, interdigitated nanogap electrodes

Bulk superconducting gap of V{sub 3}Si studied by low-energy ultrahigh-resolution photoemission spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Sato, T., E-mail: t-sato@arpes.phys.tohoku.ac.jp [Department of Physics, Tohoku University, Sendai 980-8578 (Japan); Souma, S. [WPI Research Center, Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Nakayama, K. [Department of Physics, Tohoku University, Sendai 980-8578 (Japan); Sugawara, K. [WPI Research Center, Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Toyota, N. [Department of Physics, Tohoku University, Sendai 980-8578 (Japan); Takahashi, T. [Department of Physics, Tohoku University, Sendai 980-8578 (Japan); WPI Research Center, Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan)

2016-04-15

Highlights: • We report ultrahigh-resolution photoemission spectroscopy of A15 compound V{sub 3}Si. • We found a sharp quasiparticle peak due to superconducting-gap opening. • The surface metallic component is negligibly small in the bulk-sensitive measurement. • We show that V{sub 3}Si is a single-gap s-wave superconductor. - Abstract: We have performed low-energy ultrahigh-resolution photoemission spectroscopy (PES) of A15 compound V{sub 3}Si with a xenon-plasma discharge lamp to elucidate the bulk superconducting gap. Below the superconducting transition temperature (T{sub c} = 15.9 K), we found a sharp quasiparticle peak at the Fermi level in the PES spectrum. The gap spectrum is well fitted by a single s-wave superconducting-gap function together with a dip structure at ∼30 meV suggestive of a strong electron-phonon coupling. The anomalous in-gap state previously observed in the PES measurement with high-energy photons is absent or negligibly small in the present bulk-sensitive measurement. The present PES result shows that V{sub 3}Si is a single-gap s-wave superconductor.

Radio frequency focused interdigital linear accelerator

Science.gov (United States)

Swenson, Donald A.; Starling, W. Joel

2006-08-29

An interdigital (Wideroe) linear accelerator employing drift tubes, and associated support stems that couple to both the longitudinal and support stem electromagnetic fields of the linac, creating rf quadrupole fields along the axis of the linac to provide transverse focusing for the particle beam. Each drift tube comprises two separate electrodes operating at different electrical potentials as determined by cavity rf fields. Each electrode supports two fingers, pointing towards the opposite end of the drift tube, forming a four-finger geometry that produces an rf quadrupole field distribution along its axis. The fundamental periodicity of the structure is equal to one half of the particle wavelength .beta..lamda., where .beta. is the particle velocity in units of the velocity of light and .lamda. is the free space wavelength of the rf. Particles are accelerated in the gaps between drift tubes. The particle beam is focused in regions inside the drift tubes.

Direct observation of superconducting gaps in MgB{sub 2} by angle-resolved photoemission spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Souma, S.; Machida, Y.; Sato, T.; Takahashi, T.; Matsui, H.; Wang, S.-C.; Ding, H.; Kaminski, A.; Campuzano, J.C.; Sasaki, S.; Kadowaki, K

2004-08-01

High-resolution angle-resolved photoemission spectroscopy has been carried out to clarify the anomalous superconductivity of MgB{sub 2}. We observed three bands crossing the Fermi level, which are ascribed to B2p-{sigma}, {pi} and surface bands. We have succeeded for the first time in directly observing the superconducting gaps of these bands separately. We have found that the superconducting-gap sizes of {sigma} and surface bands are 6.5 {+-} 0.5 and 6.0 {+-} 0.5 meV, respectively, while that of the {pi} band is much smaller (1.5 {+-} 0.5 meV). The present experimental result unambiguously demonstrates the validity of the two-band superconductivity in MgB{sub 2}.

Search for Superconducting Energy Gap in UPt3 by Point-Contact Spectroscopy

International Nuclear Information System (INIS)

Gouchi, Jun; Sumiyama, Akihiko; Yamaguchi, Akira; Motoyama, Gaku; Kimura, Noriaki; Yamamoto, Etsuji; Haga, Yoshinori; Ōnuki, Yoshichika

2015-01-01

We have investigated the differential resistance of the point contacts between heavy-fermion superconductor UPt 3 and a normal metal Pt, which were fabricated using a commercial piezo-electric actuator, and retried the observation of the energy gap of UPt 3 . A V-shaped dip is observed in both normal and superconducting states and disappeared around T K ∼ 20 K, suggesting that it is related to the Kondo effect. Below the superconducting transition temperature, a shallow double-minimum structure, which indicates the energy gap, has been observed for the contacts on the faces perpendicular to the a-, b- and c-axes of UPt 3

Heat Transport as a Probe of Superconducting Gap Structure

International Nuclear Information System (INIS)

Petrovic, C.; Shakeripour, H.; Taillefer, L.

2009-01-01

The structure of the superconducting gap provides important clues on the symmetry of the order parameter and the pairing mechanism. The presence of nodes in the gap function imposed by symmetry implies an unconventional order parameter, other than s-wave. Here we show how measurements of the thermal conductivity at very low temperature can be used to determine whether such nodes are present in a particular superconductor, and shed light on their nature and location. We focus on the residual linear term at T → 0. A finite value in zero magnetic field is strong evidence for symmetry-imposed nodes, and the dependence on impurity scattering can distinguish between a line of nodes or point nodes. Application of a magnetic field probes the low-energy quasiparticle excitations, whether associated with nodes or with a small value of the gap on some part of the Fermi surface, as in a multi-band superconductor. We frame our discussion around archetypal materials: Nb for s-wave, Tl 2 Ba 2 CuO 6+δ for d-wave, Sr 2 RuO 4 for p-wave, and NbSe 2 for multi-band superconductivity. In that framework, we discuss three heavy-fermion superconductors: CeIrIn 5 , CeCoIn 5 and UPt 3 .

Robust determination of the superconducting gap sign structure via quasiparticle interference

Energy Technology Data Exchange (ETDEWEB)

Altenfeld, Dustin [Institut fuer Theoretische Physik III, Ruhr-Universitaet Bochum, D-44801 Bochum (Germany); Hirschfeld, Peter [Department of Physics, University of Florida, Gainesville, Florida 32611 (United States); Eremin, Ilya [Institut fuer Theoretische Physik III, Ruhr-Universitaet Bochum, D-44801 Bochum (Germany); Kazan Federal University, Kazan 420008 (Russian Federation); Mazin, Igor [Naval Research Laboratory, Code 6393, Washington, DC 20375 (United States)

2016-07-01

Using an electronic theory, we present a qualitative description to identify sign changes of the superconducting order parameter via quasiparticle interference (QPI) measurement in Fe-based superconductors (FeSc). In particular, we point out that the temperature dependence of the momentum-integrated QPI data can be used to differentiate between s{sub +-} and s{sub ++} states in a system with typical iron pnictide Fermi surface. We show that the signed symmetrized and antisymmetrized QPI maps are useful to obtain a characteristic signature of a gap sign change or lack thereof, starting from two-band model up to ab initio based band structure calculation. We further suggest this method as a robust way of the determination of the superconducting gap sign structure in experiment and discuss its application to the LiFeAs compounds.

Design of interdigital spiral and concentric capacitive sensors for materials evaluation

Science.gov (United States)

Chen, Tianming; Bowler, Nicola

2013-01-01

This paper describes the design of two circular coplanar interdigital sensors with i) a spiral interdigital configuration and ii) a concentric interdigital configuration for the nondestructive evaluation of multilayered dielectric structures. A numerical model accounting for sensor geometry, test-piece geometry and real permittivity, and metal electrode thickness has been developed to calculate the capacitance of the sensors when in contact with a planar test-piece comprising up to four layers. Compared with a disk-and-ring coplanar capacitive sensor developed previously, the interdigital configurations are predicted to have higher signal-to-noise ratio and better accuracy in materials characterization. The disk-and-ring configuration, on the other hand, possesses advantages such as deeper penetration depth and better immunity to lift-off variations.

Gap features of layered iron-selenium-tellurium compound below and above the superconducting transition temperature by break-junction spectroscopy combined with STS

Science.gov (United States)

Ekino, T.; Sugimoto, A.; Gabovich, A. M.

2018-05-01

We studied correlations between the superconducting gap features of Te-substituted FeSe observed by scanning tunnelling spectroscopy (STS) and break-junction tunnelling spectroscopy (BJTS). At bias voltages outside the superconducting gap-energy range, the broad gap structure exists, which becomes the normal-state gap above the critical temperature, T c. Such behaviour is consistent with the model of the partially gapped density-wave superconductor involving both superconducting gaps and pseudogaps, which has been applied by us earlier to high-Tc cuprates. The similarity suggests that the parent electronic spectrum features should have much in common for these classes of materials.

Characterisation of nano-interdigitated electrodes

Energy Technology Data Exchange (ETDEWEB)

Skjolding, L H D; Ribayrol, A; Montelius, L [Division of Solid State Physics, Lund University, Box 118, SE-221 00 Lund (Sweden); Spegel, C [Department of Analytical Chemistry Lund University, Box 124, SE-221 00 Lund (Sweden); Emneus, J [MIC - Department of Micro and Nanotechnology, DTU - Building 345 East, DK-2800 Kgs. Lyngby (Denmark)], E-mail: lars_henrik.daehli_skjolding@ftf.lth.se

2008-03-15

Interdigitated electrodes made up of two individually addressable interdigitated comb-like electrode structures have frequently been suggested as ultra sensitive electrochemical biosensors. Since the signal enhancement effects due to cycling of the reduced and oxidized species are strongly dependent on the inter electrode distances, since the nature of the enhancement is due to overlying diffusion layers, interdigitated electrodes with an electrode separation of less then one micrometer are desired for maximum signal amplification. Fabrication of submicron structures can only be made by advanced lithography techniques. By use of electron beam lithography we have fabricated arrays of interdigitated electrodes with an electrode separation distance of 200 nm and an electrode finger width of likewise 200 nm. The entire electrode structure is 100 micrometre times 100 micrometre, and the active electrode area is dictated by the opening in the passivation layer, that is defined by UV lithography. Here we report measurements of redox cycling of ferrocyanide by coupled cyclic voltammograms, where the potential at one of the working electrodes are varied and either an oxidising or reducing potential is applied to the complimentary interdigitated electrode. The measurements show fast conversion and high collection efficiency round 87% as expected for nano-interdigitated electrodes.

Subharmonic energy-gap structure and heating effects in superconducting niobium point contacts

DEFF Research Database (Denmark)

Flensberg, K.; Hansen, Jørn Bindslev

1989-01-01

We present experimental data of the temperature-dependent subharmonic energy-gap structure (SGS) in the current-voltage (I-V) curves of superconducting niobium point contacts. The observed SGS is modified by heating effects. We construct a model of the quasiparticle conductance of metallic...

Superconducting gap symmetry in the superconductor BaFe1.9Ni0.1As2

Science.gov (United States)

Kuzmicheva, T. E.; Kuzmichev, S. A.; Sadakov, A. V.; Gavrilkin, S. Yu.; Tsvetkov, A. Yu.; Lu, X.; Luo, H.; Vasiliev, A. N.; Pudalov, V. M.; Chen, Xiao-Jia; Abdel-Hafiez, Mahmoud

2018-06-01

We report on the Andreev spectroscopy and specific heat of high-quality single crystals of BaFe1.9Ni0.1As2 . The intrinsic multiple Andreev reflection spectroscopy reveals two anisotropic superconducting gaps ΔL≈3.2 -4.5 meV , ΔS≈1.2 -1.6 meV (the ranges correspond to the minimum and maximum value of the coupling energy in the kxky plane). The 25 %-30 % anisotropy shows the absence of nodes in the superconducting gaps. Using a two-band model with s -wave-like gaps ΔL≈3.2 meV and ΔS≈1.6 meV , the temperature dependence of the electronic specific heat can be well described. A linear magnetic field dependence of the low-temperature specific heat offers further support of s -wave type of the order parameter. We find that a d -wave or single-gap BCS theory under the weak-coupling approach cannot describe our experiments.

Effect of external magnetic field on superconducting and spin density wave gaps of high-Tc superconductors

International Nuclear Information System (INIS)

Pradhan, B.; Raj, B.K.; Rout, G.C.

2009-01-01

A theoretical model is addressed here to study the interplay of the superconductivity (SC) and the spin density wave (SDW) long range orders in underdoped region in the vicinity of on-set of superconductivity in presence of an external magnetic field. The order parameters are calculated by using Zubarev's technique of Green's functions and determined numerically self-consistently. The gap parameters are found to be strongly coupled to each other through their coupling constants. The interplay displays BCS type two gaps in the quasi-particle density of states (DOS) which resemble the tunneling conductance of STM experiments. The gap edges in the DOS appear at ±(z+z 1 ) and ±(z-z 1 ). The applied magnetic field further induces Zeeman splitting which is explained on the basis of spin-filter effect of tunneling experiment.

Observation of gap inhomogeneity in superconducting aluminum tunnel junctions

International Nuclear Information System (INIS)

Gilmartin, H.R.

1982-01-01

Experiments using a novel technique to investigate spatial variations in the superconducting gap parameter of aluminum films driven out of equilibrium by intense tunnel injection are described. The technique features fine spatial and energy resolution of the gap parameter. The experiments employed a finely focused laser spot scanned across the surface of a double tunnel junction sandwich to produce a very weak electrical signal that was analyzed to determine the gap parameter as a function of position in the plane of the device. Technical aspects of the problem are emphasized, since a new technique is presented. An elaborate explanation of the origin and analysis of the laser induced signal is given, as well as a detailed description of the experimental apparatus. Very briefly, the principle of operation is that a large flux of quasiparticles is injected through the lower junction of the sandwich into the middle aluminum film, and the upper junction serves to detect the effects of that injection. The middle film takes on two or more values of the gap parameter under injection, presumably indicating spatial variation. The presence of a small laser spot on a given point on the device perturbs the potential on the detector junction very slightly. That perturbation is measured as a function of bias current to determine the gap parameter of the middle film at that point. The spot is scanned in a raster pattern to produce a picture of the space dependence of the gap parameter

Antiferromagnetic and superconducting gaps and their interrelation in high-Tc cuprates

International Nuclear Information System (INIS)

Arrigoni, E.; Zacher, M.G.; Eckl, T.; Hanke, W.

2003-01-01

We propose a phenomenological model, comprising a microscopic SO(5) model plus the on-site Hubbard interaction U (projected SO(5) model) to understand the interrelation between the d-wave-gap modulation observed by recent angle-resolved photoemission experiments in the insulating antiferromagnet Ca 2 CuO 2 Cl 2 and the d-wave gap of high-T c superconducting materials. The on-site interaction U is important in order to produce a Mott gap of the correct order of magnitude, which would be absent in an exact SO(5) theory. The projected SO(5)-model explains the gap characteristics, namely both the symmetry and the different order of magnitude of the gap modulations between the AF and the SCc phases. Furthermore, it is shown that the projected SO(5) theory can provide an explanation for a recent observation [E. Pavarini et al., Phys. Rev. Lett. 87, 47003 (2001)], i. e. that the maximum T c observed in a large variety of high-T c cuprates scales with the next-nearest-neighbor hopping matrix element t'. (Abstract Copyright [2003], Wiley Periodicals, Inc.)

Superconducting low-velocity linac for the Argonne positive-ion injector

International Nuclear Information System (INIS)

Shepard, K.W.; Markovich, P.K.; Zinkann, G.P.; Clifft, B.; Benaroya, R.

1989-01-01

A low-velocity superconducting linac has been developed as part of a positive-ion injector system, which is replacing a 9 MV tandem as the injector for the ATLAS accelerator. The linac consists of an independently phased array of resonators, and is designed to accelerate various ions over a velocity range .008 < v/c < .06. The resonator array is formed of four different types of superconducting interdigital structures. The linac is being constructed in three phases, each of which will cover the full velocity range. Successive phases will increase the total accelerating potential and permit heavier ions to be accelerated. Assembly of the first phase was completed in early 1989. In initial tests with beam, a five-resonator array provided approximately 3.5 MV of accelerating potential and operated without difficulty for several hundred hours. The second phase is scheduled for completion in late 1989, and will increase the accelerating potential to more than 8 MV. 5 refs., 2 figs., 1 tab

Superconducting low-velocity linac for the Argonne positive-ion injector

Energy Technology Data Exchange (ETDEWEB)

Shepard, K.W.; Markovich, P.K.; Zinkann, G.P.; Clifft, B.; Benaroya, R.

1989-01-01

A low-velocity superconducting linac has been developed as part of a positive-ion injector system, which is replacing a 9 MV tandem as the injector for the ATLAS accelerator. The linac consists of an independently phased array of resonators, and is designed to accelerate various ions over a velocity range .008 < v/c < .06. The resonator array is formed of four different types of superconducting interdigital structures. The linac is being constructed in three phases, each of which will cover the full velocity range. Successive phases will increase the total accelerating potential and permit heavier ions to be accelerated. Assembly of the first phase was completed in early 1989. In initial tests with beam, a five-resonator array provided approximately 3.5 MV of accelerating potential and operated without difficulty for several hundred hours. The second phase is scheduled for completion in late 1989, and will increase the accelerating potential to more than 8 MV. 5 refs., 2 figs., 1 tab.

Tunnelling determined superconducting energy gap of bulk single crystal aluminum

International Nuclear Information System (INIS)

Civiak, R.L.

1974-01-01

A procedure has been developed for fabricating Giaver tunnel junctions on bulk aluminum. Al-I-Ag junctions were prepared, where I is the naturally formed oxide on the polished, chemically treated aluminum surface. The aluminum energy gap was determined from tunneling conductance curves obtained from samples oriented in three different crystal directions, and as a function of magnetic field in each of these orientations. In contrast to the results of microwave absorption measurements on superconducting aluminum, no magnetic field dependence could be measured for either the average gap or the spread in gap values of the tunneling electrons. This is consistent with commonly accepted tunneling selection rules, and Garfunkel's interpretation of the microwave behavior which depended upon adjusting the energy spectrum of only the electrons traveling parallel to the surface in the presence of a magnetic field. The energy gaps measured for samples oriented in the 100, 110 and 111 directions are 3.52, 3.50 and 3.39 kT/sub c/, respectively. The trend in the anisotropy is the same as in the calculation of Leavens and Carbotte, however, the magnitude of the anisotropy is smaller than in their calculation and that which previous measurements have indicated

Realization of a mixed-symmetry superconducting gap in correlated organic metals

Science.gov (United States)

Altmeyer, Michaela; Guterding, Daniel; Jeschke, Harald O.; Diehl, Sandra; Methfessel, Torsten; Tutsch, Ulrich; Schubert, Harald; Lang, Michael; Müller, Jens; Huth, Michael; Jourdan, Martin; Elmers, Hans-Joachim; Valenti, Roser

Recent scanning tunneling spectroscopy measurements on the organic charge tranfer salt κ-(BEDT-TTF)2Cu[N(CN)2]Br show clear evidence of a highly anisotropic gap structure. Based on an ab initio derived model Hamiltonian we employ random phase approximation spin fluctuation theory yielding a composite order parameter of (extended) s+dx2-y2 symmetry. Taking explicitly also the shape of the Fermi surface into account we calculate STS spectra that are in excellent agreement to the experimental observations [1]. Moreover we determine the minimal tight binding model to describe the general lattice structure of these compounds accurately and generate a phase diagram for the gap symmetry by varying the hopping parameters. Based on ab initio derived parameter sets we predict the gap symmetry of other superconducting κ charge transfer salts. This work was supported by Deutsche Forschungsgemeinschaft under Grant No. SFB/TR 49.

Superconducting energy gap of BaPb/sub 1-//sub x/Bi/sub x/O3

International Nuclear Information System (INIS)

Schlesinger, Z.; Collins, R.T.; Scott, B.A.; Calise, J.A.

1988-01-01

We report the first infrared measurement of the superconducting energy gap of BaPb/sub 1-//sub x/Bi/sub x/O 3 . In our polycrystalline samples with T/sub c/≅9.5 K (x≅0.2) we obtain 2Δ≅3.2kT/sub c/, roughly in agreement with the weak-coupling Bardeen-Cooper-Schrieffer prediction, 2Δ = 3.5kT/sub c/, and with tunneling measurements of the gap. We do not observe any structure above the gap energy associated with strong coupling

Microscopic theory of the superconducting gap in the quasi-one-dimensional organic conductor (TMTSF) 2ClO4 : Model derivation and two-particle self-consistent analysis

Science.gov (United States)

Aizawa, Hirohito; Kuroki, Kazuhiko

2018-03-01

We present a first-principles band calculation for the quasi-one-dimensional (Q1D) organic superconductor (TMTSF) 2ClO4 . An effective tight-binding model with the TMTSF molecule to be regarded as the site is derived from a calculation based on maximally localized Wannier orbitals. We apply a two-particle self-consistent (TPSC) analysis by using a four-site Hubbard model, which is composed of the tight-binding model and an onsite (intramolecular) repulsive interaction, which serves as a variable parameter. We assume that the pairing mechanism is mediated by the spin fluctuation, and the sign of the superconducting gap changes between the inner and outer Fermi surfaces, which correspond to a d -wave gap function in a simplified Q1D model. With the parameters we adopt, the critical temperature for superconductivity estimated by the TPSC approach is approximately 1 K, which is consistent with experiment.

Interdigital Melanoma of the Foot Affecting Two Neighbouring Interdigital Spaces – Second Case Report

Directory of Open Access Journals (Sweden)

Uwe Wollina

2017-07-01

Full Text Available Melanoma affecting two interdigital spaces has been recently described by our group for the first time in medical literature. Here we present a second patient with acrolentiginous melanoma of the sole affecting the 1st and 2nd interdigital space. The tumour was removed by delayed Mohs surgery. Due to the extension of the melanoma, digit II and III had to be removed. Staging excluded metastatic spread. The tumour was classified as pT4bN0M0.

Effect of external magnetic field on superconducting and spin density wave gaps of high-T{sub c} superconductors

Energy Technology Data Exchange (ETDEWEB)

Pradhan, B., E-mail: brunda@iopb.res.i [Govt. Science College, Malkangiri 764 048 (India); Raj, B.K. [B.J.B. College, Bhubaneswar 751 014 (India); Rout, G.C., E-mail: gcr@iopb.res.i [Condensed Matter Physics Group P.G. Dept. of Applied Physics and Ballistics, F.M. University, Balasore 756 019 (India)

2009-07-01

A theoretical model is addressed here to study the interplay of the superconductivity (SC) and the spin density wave (SDW) long range orders in underdoped region in the vicinity of on-set of superconductivity in presence of an external magnetic field. The order parameters are calculated by using Zubarev's technique of Green's functions and determined numerically self-consistently. The gap parameters are found to be strongly coupled to each other through their coupling constants. The interplay displays BCS type two gaps in the quasi-particle density of states (DOS) which resemble the tunneling conductance of STM experiments. The gap edges in the DOS appear at +-(z+z{sub 1}) and +-(z-z{sub 1}). The applied magnetic field further induces Zeeman splitting which is explained on the basis of spin-filter effect of tunneling experiment.

Spectroscopic evidence for two-gap superconductivity in the quasi-1D chalcogenide Nb2Pd0.81S5

Science.gov (United States)

Park, Eunsung; Lee, Sangyun; Ronning, Filip; Thompson, Joe D.; Zhang, Qiu; Balicas, Luis; Lu, Xin; Park, Tuson

2018-04-01

Low-dimensional electronic systems with confined electronic wave functions have attracted interest due to their propensity toward novel quantum phases and their use in wide range of nanotechnologies. The newly discovered chalcogenide Nb2PdS5 possesses a quasi-one-dimensional electronic structure and becomes superconducting. Here, we report spectroscopic evidence for two-band superconductivity, where soft point-contact spectroscopic measurements in the superconducting (SC) state reveal Andreev reflection in the differential conductance G. Multiple peaks in G are observed at 1.8 K and explained by the two-band Blonder–Tinkham–Klapwijk model with two gaps Δ1  =  0.61 meV and Δ2  =  1.20 meV. The progressive evolution of G with temperature and magnetic field corroborates the multiple nature of the SC gaps.

Specific heat of FeSe: Two gaps with different anisotropy in superconducting state

Science.gov (United States)

Muratov, A. V.; Sadakov, A. V.; Gavrilkin, S. Yu.; Prishchepa, A. R.; Epifanova, G. S.; Chareev, D. A.; Pudalov, V. M.

2018-05-01

We present detailed study of specific heat of FeSe single crystals with critical temperature Tc = 8.45 K at 0.4 - 200 K in magnetic fields 0 - 9 T. Analysis of the electronic specific heat at low temperatures shows the coexistence of isotropic s-wave gap and strongly anisotropic extended s-wave gap without nodes. It was found two possibilities of superconducting gap parameters which give equally description of experimental data: (i) two gaps with approximately equal amplitudes and weight contribution to specific heat: isotropic Δ1 = 1.7 meV (2Δ1 /kBTc =4.7) and anisotropic gap with the amplitude Δ2max = 1.8 meV (2 Δ2max /kBTc =4.9 and anisotropy parameter m = 0.85); (ii) two gaps with substantially different values: isotropic large gap Δ1 = 1.65 meV (2Δ1 /kBTc = 4.52) and anisotropic small gap Δ2max = 0.75 meV (2Δ2max /kBTc = 2) with anisotropy parameter m = 0.71 . These results are confirmed by the field behavior of the residual electronic specific heat γr.

Multiqubit quantum phase gate using four-level superconducting quantum interference devices coupled to superconducting resonator

Energy Technology Data Exchange (ETDEWEB)

Waseem, Muhammad; Irfan, Muhammad [Department of Physics and Applied Mathematics, Pakistan Institute of Engineering and Applied Sciences, Nilore, Islamabad 45650 (Pakistan); Qamar, Shahid, E-mail: shahid_qamar@pieas.edu.pk [Department of Physics and Applied Mathematics, Pakistan Institute of Engineering and Applied Sciences, Nilore, Islamabad 45650 (Pakistan)

2012-07-15

In this paper, we propose a scheme to realize three-qubit quantum phase gate of one qubit simultaneously controlling two target qubits using four-level superconducting quantum interference devices (SQUIDs) coupled to a superconducting resonator. The two lowest levels Divides 0 Right-Pointing-Angle-Bracket and Divides 1 Right-Pointing-Angle-Bracket of each SQUID are used to represent logical states while the higher energy levels Divides 2 Right-Pointing-Angle-Bracket and Divides 3 Right-Pointing-Angle-Bracket are utilized for gate realization. Our scheme does not require adiabatic passage, second order detuning, and the adjustment of the level spacing during gate operation which reduce the gate time significantly. The scheme is generalized for an arbitrary n-qubit quantum phase gate. We also apply the scheme to implement three-qubit quantum Fourier transform.

Antiferromagnetic and superconducting gaps and their interrelation in high-T sub c cuprates

CERN Document Server

Arrigoni, E; Eckl, T; Hanke, W

2003-01-01

We propose a phenomenological model, comprising a microscopic SO(5) model plus the on-site Hubbard interaction U (projected SO(5) model) to understand the interrelation between the d-wave-gap modulation observed by recent angle-resolved photoemission experiments in the insulating antiferromagnet Ca sub 2 CuO sub 2 Cl sub 2 and the d-wave gap of high-T sub c superconducting materials. The on-site interaction U is important in order to produce a Mott gap of the correct order of magnitude, which would be absent in an exact SO(5) theory. The projected SO(5)-model explains the gap characteristics, namely both the symmetry and the different order of magnitude of the gap modulations between the AF and the SCc phases. Furthermore, it is shown that the projected SO(5) theory can provide an explanation for a recent observation [E. Pavarini et al., Phys. Rev. Lett. 87, 47003 (2001)], i. e. that the maximum T sub c observed in a large variety of high-T sub c cuprates scales with the next-nearest-neighbor hopping matrix e...

Energy gap and surface structure of superconducting diamond films probed by scanning tunneling microscopy

International Nuclear Information System (INIS)

Nishizaki, Terukazu; Takano, Yoshihiko; Nagao, Masanori; Takenouchi, Tomohiro; Kawarada, Hiroshi; Kobayashi, Norio

2007-01-01

We have performed scanning tunneling microscopy/spectroscopy (STM/STS) experiments on (1 1 1)-oriented epitaxial films of heavily boron-doped diamond at T = 0.47 K. The STM topography shows two kinds of atomic structures: a hydrogenated 1 x 1 structure, C(1 1 1)1 x 1:H, and an amorphous structure. On the C(1 1 1)1 x 1:H region, the tunneling spectra show superconducting property with the energy gap Δ = 0.83 meV. The obtained gap ratio 2Δ/k B T c = 3.57 is consistent with the weak-coupling BCS theory

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

Tunneling observation at very low temperature of impurity bands within the gap of the Kondo superconducting system CuFe/Pb(T(K)>T(c))

International Nuclear Information System (INIS)

Dumoulin, Louis; Le Fur, Daniel

1976-01-01

Very low temperature superconducting tunneling experiments on CuFe(12.10 -6 ) backed by superconducting lead show a band of localized states next to the gap edge. There is no quantitative agreement with the perturbative approach of Mueller-Hartmann Zittartz in this system where the Kondo temperature is larger than the superconductive T(c) [fr

Two-gap superconductivity with line nodes in CsCa2Fe4As4F2

Science.gov (United States)

Kirschner, Franziska K. K.; Adroja, Devashibhai T.; Wang, Zhi-Cheng; Lang, Franz; Smidman, Michael; Baker, Peter J.; Cao, Guang-Han; Blundell, Stephen J.

2018-02-01

We report the results of a muon-spin rotation (μ SR ) experiment to determine the superconducting ground state of the iron-based superconductor CsCa2Fe4As4F2 with Tc≈28.3 K . This compound is related to the fully gapped superconductor CaCsFe4As4 , but here the Ca-containing spacer layer is replaced with one containing Ca2F2 . The temperature evolution of the penetration depth strongly suggests the presence of line nodes and is best modeled by a system consisting of both an s - and a d -wave gap. We also find a potentially magnetic phase which appears below ≈10 K but does not appear to compete with the superconductivity. This compound contains the largest alkali atom in this family of superconductors, and our results yield a value for the in-plane penetration depth of λa b(T =0 ) =244 (3 ) nm .

Design Tool for Liquid-Nitrogen Gaps in Superconducting Apparatus

International Nuclear Information System (INIS)

Pace, Marshall O.; Sauers, Isidor; James, David Randy; Tuncer, Enis; Polyzos, Georgios

2011-01-01

For designers of high temperature superconducting equipment with liquid nitrogen as a dielectric, an expedient universal curve is sought that provides breakdown strength for a specified class of electrode shapes, with any practical sizes of electrodes and gap; thus the universal curve fills in missing experimental data. Universal breakdown strength curves at pressures of or slightly above 100 kPa, are being developed for AC, DC or impulse stress for the class with sphere-sphere, plane-plane and sphere-plane gaps, with three independent parameters: the size of each electrode and gap. A user can normalize his parameters and find the corresponding breakdown strength, even though no data were available for his exact dimensions. For AC and DC stresses the geometrical effects of stressed area/volume are incorporated from most published AC and DC experimental data of the last 50 years, by plotting breakdown field versus new geometrical quantities, such that all data fall approximately on or near one normalized universal curve. This avoids the usual difficult task of calculating stressed area and volume effects on the breakdown values for the graph ordinate. For impulse stress a more traditional plot suffices to produce a universal curve. This suggests that area/volume effects might not be so important with impulse stress. If the method proves reliable, it may be possible to determine design parameters for a broad range of geometries, help unify seemingly disparate breakdown data in the literature, and provide easily used, practical guidance for designers.

Superconducting accelerating structures for very low velocity ion beams

Directory of Open Access Journals (Sweden)

J. Xu

2008-03-01

Full Text Available This paper presents designs for four types of very-low-velocity superconducting (SC accelerating cavity capable of providing several MV of accelerating potential per cavity, and suitable for particle velocities in the range 0.006Superconducting TEM-class cavities have been widely applied to cw acceleration of ion beams. SC linacs can be formed as an array of independently phased cavities, enabling a variable velocity profile to maximize the output energy for each of a number of different ion species. Several laboratories in the U.S. and Europe are planning exotic beam facilities based on SC linacs. The cavity designs presented here are intended for the front end of such linacs, particularly for the postacceleration of rare isotopes of low charge state. Several types of SC cavities have been developed recently to cover particle velocities above 0.06c. Superconducting four-gap quarter-wave resonators for velocities 0.008<β=v/c<0.05 were developed about two decades ago and have been successfully operated at the ATLAS SC linac at Argonne National Laboratory. Since that time, progress in simulation tools, cavity fabrication, and processing have increased SC cavity gradients by a factor of 3–4. This paper applies these tools to optimize the design of a four-gap quarter-wave resonator for exotic beam facilities and other low-velocity applications.

Superconducting accelerating structures for very low velocity ion beams

Energy Technology Data Exchange (ETDEWEB)

Xu, J.; Shepard, K.W.; Ostroumov, P.N.; Fuerst, J.D.; Waldschmidt, G.; /Argonne; Gonin, I.V.; /Fermilab

2008-01-01

This paper presents designs for four types of very-low-velocity superconducting accelerating cavity capable of providing several MV of accelerating potential per cavity, and suitable for particle velocities in the range 0.006 < v/c < 0.06. Superconducting TEM-class cavities have been widely applied to CW acceleration of ion beams. SC linacs can be formed as an array of independently-phased cavities, enabling a variable velocity profile to maximize the output energy for each of a number of different ion species. Several laboratories in the US and Europe are planning exotic beam facilities based on SC linacs. The cavity designs presented here are intended for the front-end of such linacs, particularly for the post-acceleration of rare isotopes of low charge state. Several types of SC cavities have been developed recently to cover particle velocities above 0.06c. Superconducting four-gap quarter-wave resonators for velocities 0.008 < {beta} = v/c < 0.05 were developed about two decades ago and have been successfully operated at the ATLAS SC linac at Argonne National Laboratory. Since that time, progress in simulation tools, cavity fabrication and processing have increased SC cavity gradients by a factor of 3-4. This paper applies these tools to optimize the design of a four-gap quarter-wave resonator for exotic beam facilities and other low-velocity applications.

Hermetically sealed superconducting magnet motor

Science.gov (United States)

DeVault, Robert C.; McConnell, Benjamin W.; Phillips, Benjamin A.

1996-01-01

A hermetically sealed superconducting magnet motor includes a rotor separated from a stator by either a radial gap, an axial gap, or a combined axial and radial gap. Dual conically shaped stators are used in one embodiment to levitate a disc-shaped rotor made of superconducting material within a conduit for moving cryogenic fluid. As the rotor is caused to rotate when the field stator is energized, the fluid is pumped through the conduit.

Anisotropy in superconducting gap in YBa2Cu3O7-δ

Science.gov (United States)

Verma, Sanjeev K.; Kumari, Anita; Gupta, Anushri; Indu, B. D.

2018-04-01

Taking into account the modified form of Born-Mayer-Huggins potential (MBMHP) and many body quantum dynamics based Green's function theory via a modified Hamiltonian which includes the effects of electrons, phonons, anharmonicities, defects and electron-phonon interactions; the quasiparticle renormalized frequency has been obtained and numerically analyzed for high temperature superconductor (HTS) cuprate YBa2Cu3O7-δ. This evaluation enables one to calculate superconducting gap (SG) in [100] and [010] direction through the dispersion of renormalized mode. A higher SG found in [010] than [100] direction at different doping level establishing its anisotropic nature.

Dependence of the quasiparticle recombination rate on the superconducting gap and TC

Science.gov (United States)

Carr, G. L.; Xi, Xiaoxiang; Hwang, J.; Tashiro, H.; Reitze, D. H.; Tanner, D. B.

2010-03-01

The relaxation of excess quasiparticles in a BCS superconductor is known to depend on quantities such as the quasiparticle & phonon density of states, and their coupling (Kaplan et al, Phys. Rev. B 14 4854, 1976). Disorder or an applied field can disrupt superconductivity, as evidenced by a reduced TC. We consider some simple modifications to the quasiparticle density of states consistent with a suppressed energy gap and TC, leading to changes in the intrinsic and effective (measured) rates for excess quasiparticles to recombine into pairs. We review some results for disordered MoGe and discuss the magnetic-field dependence of the recombination process.

First-principles calculation of the superconducting gap function due to electron-electron interaction for YBa2Cu3O/sub 7-//sub x/

International Nuclear Information System (INIS)

Chui, S.T.; Kasowski, R.V.; Hsu, W.Y.

1989-01-01

We argue that because of the anisotropic nature of YBa 2 Cu 3 O/sub 7-//sub x/, one-dimensional-type charge- and spin-density fluctuations produce an effective attraction that overcomes the electron-electron Coulomb repulsion, but only at large distances. This effective attraction is further enhanced by band-structure effects such that a substantial superconducting transition temperature can be obtained. Without making any assumption of the symmetry of the gap function, we solve the Bardeen-Cooper-Schrieffer (BCS) superconducting gap equation for the six bands closest to the Fermi level. A highly anisotropic gap function with a maximum of about 0.11 eV is found. From the linearized gap equation, a transition temperature of about 0.035 eV is obtained. This is about one-quarter the maximum of the gap function, consistent with the experimental ratio of the transition temperature to the gap determined from tunneling, infrared, and nuclear quadrupole resonance measurements. The important participants to the superconducting pair come from electrons close to planar copper [Cu(2)] and chain oxygen [O(1) and O(4)] sites, consistent with recent quadrupole resonance measurements. Our calculation produces a coherence length of the order of 30 A in the xy direction, the same order of magnitude as the experimental result and considerably smaller than the conventional magnitude of ordinary BCS materials. Similar calculations for YBa 2 Cu 3 O/sub 6.5/ where periodic O vacancies are introduced along the one-dimensional Cu-O chains shows that the transition temperature is reduced by half

Effects of Out-of-Plane Disorder on the Nodal Quasiparticle and Superconducting Gap in Single-Layer Bi_2Sr_1.6Ln_0.4CuO_6 delta (Ln = La, Nd, Gd)

Energy Technology Data Exchange (ETDEWEB)

Hashimoto, M.

2011-01-04

How out-of-plane disorder affects the electronic structure has been investigated for the single-layer cuprates Bi{sub 2}Sr{sub 1.6}Ln{sub 0.4}CuO{sub 6+{delta}} (Ln = La, Nd, Gd) by angle-resolved photoemission spectroscopy. We have observed that, with increasing disorder, while the Fermi surface shape and band dispersions are not affected, the quasi-particle width increases, the anti-nodal gap is enhanced and the superconducting gap in the nodal region is depressed. The results indicate that the superconductivity is significantly depressed by out-of-plane disorder through the enhancement of the anti-nodal gap and the depression of the superconducting gap in the nodal region.

Rigorous study of the gap equation for an inhomogeneous superconducting state near T/sub c/

International Nuclear Information System (INIS)

Hu, C.R.

1975-01-01

An analytical study of the gap equation in the Bogoliubov formulation is presented. The normal-superconducting phase boundary is simulated by the expression Δ (R/sup =/) = Δ/sub infinity/ tanh / α Δ/sub infinity/z/v/sub f/) theta(z) where Δ/sub infinity/(t) is the equilibrium gap, theta (z) a unit step function and v/sub f/ the Fermi velocity. The Bogoliubov-de Gennes equations are solved in a nonperturbative WKBJ approximation. The gap equation is expanded near T/sub c/ in powers of Δ/sub infinity/ and the major term is of the same order as that given by the Ginzburg-Landau-Gor'kov approximation. Discrepancies in the two values are discussed in detail. It is concluded that the present technique reproduces the Ginzburg-Landau-Gor'kov results except within a BCS coherence length. 25 references

Rigorous study of the gap equation for an inhomogeneous superconducting state near T/sub c/

International Nuclear Information System (INIS)

Hu, C.

1975-01-01

A rigorous analytic study of the self-consistent gap equation (symobolically Δ=F/sub T/Δ), for an inhomogeneous superconducting state, is presented in the Bogoliubov formulation. The gap function Δ (r) is taken to simulate a planar normal-superconducting phase boundary: Δ (r) =Δ/sub infinity/ tanh(αΔ/sub infinity/z/v/sub F/) THETA (z), where Δ/sub infinity/(T) is the equilibrium gap, v/subF/ is the Fermi velocity, and THETA (z) is a unit step function. First a special space integral of the gap equation proportional∫ 0 /sub +//sup infinity/(F/sub T/-Δ)(dΔ/dz) dz is evaluated essentially exactly, except for a nonperturbative WKBJ approximation used in solving the Bogoliubov--de Gennes equations. It is then expanded near the transition temperature T/sub c/ in power of Δ/sub infinity/proportional (1-T/T/sub c/) 1 / 2 , demonstrating an exact cancellation of a subseries of ''anomalous-order'' terms. The leading surviving term is found to agree in order, but not in magnitude, with the Ginzburg-Landau-Gor'kov (GLG) approximation. The discrepancy is found to be linked to the slope discontinuity in our chosen Δ. A contour-integral technique in a complex-energy plane is then devised to evaluate the local value of F/sub T/-Δ exactly. Our result reveals that near T/sub c/ this method can reproduce the GLG result essentially everywhere, except within a BCS coherence length not xi (T) exclamation from a singularity in Δ, where F/sub T/-Δ can have a singular contribution with an ''anomalous'' local magnitude, not expected from the GLG approach. This anomalous term precisely accounts for the discrepancy found in the special integral of the gap equation as mentioned above, and likely explains the ultimate origin of the anomalous terms found in the free energy of an isolated vortex line by Cleary

S-I-N tunneling spectroscopy of MgB2 superconductor: evidence of two superconducting energy gaps

International Nuclear Information System (INIS)

Sen, Shashwati; Aswal, D.K.; Singh, Ajay; Gadkari, S.C.; Shah, K.; Gupta, S.K.; Sahni, V.C.

2002-01-01

The tunneling spectra of polycrystalline MgB 2 , have been recorded, at different temperatures between 29 K and T c , using planar superconductor- insulating-normal (S-I-N) tunneling spectroscopy. The planar S-I-N tunnel junctions have been fabricated by thermally evaporating Ag electrodes on MgB 2 surface. The naive layer, which forms at the surface of MgB 2 , due to atmospheric degradation, was employed as an insulating layer between Ag electrodes and MgB 2 . We have found presence of two clear superconducting energy gaps in MgB 2 . The magnitudes of these gaps at 29.5 K are 1.8 and 5.9 MeV, respectively. In the vicinity of T c , while larger energy gap obeyed BCS temperature dependence, the smaller energy gap deviated from BCS dependence. All the spectra exhibited zero-bias conductance, which decreased linearly with temperature and vanished at T c . (author)

Superconductivity in MgB{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Muranaka, Takahiro; Akimitsu, Jun [Aoyama Gakuin Univ., Kanagawa (Japan). Dept. of Physics and Mathematics

2011-07-01

We review superconductivity in MgB{sub 2} in terms of crystal and electronic structure, electron-phonon coupling, two-gap superconductivity and application. Finally, we introduce the development of new superconducting materials in related compounds. (orig.)

Self-consistent T-matrix theory of superconductivity

Czech Academy of Sciences Publication Activity Database

Šopík, B.; Lipavský, Pavel; Männel, M.; Morawetz, K.; Matlock, P.

2011-01-01

Roč. 84, č. 9 (2011), 094529/1-094529/13 ISSN 1098-0121 R&D Projects: GA ČR GAP204/10/0212; GA ČR(CZ) GAP204/11/0015 Institutional research plan: CEZ:AV0Z10100521 Keywords : superconductivity * T-matrix * superconducting gap * restricted self-consistency Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.691, year: 2011

Universal doping evolution of the superconducting gap anisotropy in single crystals of electron-doped Ba(Fe1‑x Rh x )2As2 from London penetration depth measurements

Science.gov (United States)

Kim, Hyunsoo; Tanatar, M. A.; Martin, C.; Blomberg, E. C.; Ni, Ni; Bud’ko, S. L.; Canfield, P. C.; Prozorov, R.

2018-06-01

Doping evolution of the superconducting gap anisotropy was studied in single crystals of 4d-electron doped Ba(Fe1‑x Rh x )2As2 using tunnel diode resonator measurements of the temperature variation of the London penetration depth . Single crystals with doping levels representative of an underdoped regime x  =  0.039 ( K), close to optimal doping x  =  0.057 ( K) and overdoped x  =  0.079 ( K) and x  =  0.131( K) were studied. Superconducting energy gap anisotropy was characterized by the exponent, n, by fitting the data to the power-law, . The exponent n varies non-monotonically with x, increasing to a maximum n  =  2.5 for x  =  0.079 and rapidly decreasing towards overdoped compositions to 1.6 for x  =  0.131. This behavior is qualitatively similar to the doping evolution of the superconducting gap anisotropy in other iron pnictides, including hole-doped (Ba,K)Fe2As2 and 3d-electron-doped Ba(Fe,Co)2As2 superconductors, finding a full gap near optimal doping and strong anisotropy toward the ends of the superconducting dome in the T-x phase diagram. The normalized superfluid density in an optimally Rh-doped sample is almost identical to the temperature-dependence in the optimally doped Ba(Fe,Co)2As2 samples. Our study supports the universal superconducting gap variation with doping and pairing at least in iron based superconductors of the BaFe2As2 family.

Status of the uranium upgrade of ATLAS

International Nuclear Information System (INIS)

Bollinger, L.M.; Billquist, P.J.; Bogaty, J.M.; Clifft, B.E.; Markovich, P.; Munson, F.H.; Pardo, R.C.; Shepard, K.W.; Zinkann, G.P.

1991-01-01

The ATLAS Positive Ion Injector (PII) is designed to replace the tandem injector for the ATLAS heavy-ion facility. When the PII project is complete, ATLAS will be able to accelerate all ions through uranium to energies above the Coulomb barrier. PII consists of an ECR ion source on a 350 KV platform and a very low-velocity superconducting linac. The linac is composed of an independently-phased array of superconducting four-gap interdigital resonators which accelerate over a velocity range of .007c to .05c. the PII project is approximately 75% complete. Beam tests and experiments using the partially completed PII have demonstrated that the technical design goals are being met. The design, construction status, and results of recent operational experience using the PII will be discussed. 10 refs., 2 figs., 1 tab

Status of the uranium upgrade of ATLAS

Energy Technology Data Exchange (ETDEWEB)

Bollinger, L.M.; Billquist, P.J.; Bogaty, J.M.; Clifft, B.E.; Markovich, P.; Munson, F.H.; Pardo, R.C.; Shepard, K.W.; Zinkann, G.P.

1991-01-01

The ATLAS Positive Ion Injector (PII) is designed to replace the tandem injector for the ATLAS heavy-ion facility. When the PII project is complete, ATLAS will be able to accelerate all ions through uranium to energies above the Coulomb barrier. PII consists of an ECR ion source on a 350 KV platform and a very low-velocity superconducting linac. The linac is composed of an independently-phased array of superconducting four-gap interdigital resonators which accelerate over a velocity range of .007c to .05c. the PII project is approximately 75% complete. Beam tests and experiments using the partially completed PII have demonstrated that the technical design goals are being met. The design, construction status, and results of recent operational experience using the PII will be discussed. 10 refs., 2 figs., 1 tab.

Coupler Development and Gap Field Analysis for the 352 MHz Superconducting CH-Cavity

CERN Document Server

Liebermann, H; Ratzinger, U; Sauer, A C

2004-01-01

The cross-bar H-type (CH) cavity is a multi-gap drift tube structure based on the H-210 mode currently under development at IAP Frankfurt and in collaboration with GSI. Numerical simulations and rf model measurements showed that the CH-type cavity is an excellent candidate to realize s.c. multi-cell structures ranging from the RFQ exit energy up to the injection energy into elliptical multi-cell cavities. The reasonable frequency range is from about 150 MHz up to 800 MHz. A 19-cell, β=0.1, 352 MHz, bulk niobium prototype cavity is under development at the ACCEL-Company, Bergisch-Gladbach. This paper will present detailed MicroWave Studio simulations and measurements for the coupler development of the 352 MHz superconducting CH cavity. It will describe possibilities for coupling into the superconducting CH-Cavity. The development of the coupler is supported by measurement on a room temperature CH-copper model. We will present the first results of the measurements of different couplers, e.g. capacitiv...

Microstrip Cross-coupled Interdigital SIR Based Bandpass Filter

Directory of Open Access Journals (Sweden)

R. K. Maharjan

2012-09-01

Full Text Available A simple and compact 4.9 GHz bandpass filter for C-band applications is proposed. This paper presents a novel microstrip cross-coupled interdigital half-wavelength stepped impedance resonator (SIR based bandpass filter (BPF.The designed structure is similar to that of a combination of two parallel interdigital capacitors. The scattering parameters of the structure are measured using vector network analyzer (VNA. The self generated capacitive and inductive reactances within the interdigital resonators exhibited in a resonance frequency of 4.9 GHz. The resonant frequency and bandwidth of the capacitive cross-coupled resonator is directly optimized from the physical arrangement of the resonators. The measured insertion loss (S21 and return loss (S11 were 0.3 dB and 28 dB, respectively, at resonance frequency which were almost close to the simulation results.

Hydrocarbon deposition in gaps of tungsten and graphite tiles in Experimental Advanced Superconducting Tokamak edge plasma parameters

International Nuclear Information System (INIS)

Xu Qian; Yang Zhongshi; Luo Guangnan

2015-01-01

The three-dimensional (3D) Monte Carlo code PIC-EDDY has been utilized to investigate the mechanism of hydrocarbon deposition in gaps of tungsten tiles in the Experimental Advanced Superconducting Tokamak (EAST), where the sheath potential is calculated by the 2D in space and 3D in velocity particle-in-cell method. The calculated results for graphite tiles using the same method are also presented for comparison. Calculation results show that the amount of carbon deposited in the gaps of carbon tiles is three times larger than that in the gaps of tungsten tiles when the carbon particles from re-erosion on the top surface of monoblocks are taken into account. However, the deposition amount is found to be larger in the gaps of tungsten tiles at the same CH 4 flux. When chemical sputtering becomes significant as carbon coverage on tungsten increases with exposure time, the deposition inside the gaps of tungsten tiles would be considerable. (author)

Design and Fabrication of Interdigital Nanocapacitors Coated with HfO2

Directory of Open Access Journals (Sweden)

Gabriel González

2015-01-01

Full Text Available In this article nickel interdigital capacitors were fabricated on top of silicon substrates. The capacitance of the interdigital capacitor was optimized by coating the electrodes with a 60 nm layer of HfO2. An analytical solution of the capacitance was compared to electromagnetic simulations using COMSOL and with experimental measurements. Results show that modeling interdigital capacitors using Finite Element Method software such as COMSOL is effective in the design and electrical characterization of these transducers.

Role of superconducting energy gap in extended BCS-Bose crossover theory

Science.gov (United States)

Chávez, I.; García, L. A.; de Llano, M.; Grether, M.

2017-10-01

The generalized Bose-Einstein condensation (GBEC) theory of superconductivity (SC) is briefly surveyed. It hinges on three distinct new ingredients: (i) Treatment of Cooper pairs (CPs) as actual bosons since they obey Bose statistics, in contrast to BCS pairs which do not obey Bose commutation relations; (ii) inclusion of two-hole Cooper pairs (2hCPs) on an equal footing with two-electron Cooper pairs (2eCPs), thus making this a complete boson-fermion (BF) model; and (iii) inclusion in the resulting ternary ideal BF gas with particular BF vertex interactions that drive boson formation/disintegration processes. GBEC subsumes as special cases both BCS (having its 50-50 symmetry of both kinds of CPs) and ordinary BEC theories (having no 2hCPs), as well as the now familiar BCS-Bose crossover theory. We extended the crossover theory with the explicit inclusion of 2hCPs and construct a phase diagram of Tc/TF versus n/nf, where Tc and TF are the critical and Fermi temperatures, n is the total number density and nf that of unbound electrons at T = 0. Also, with this extended crossover one can construct the energy gap Δ(T)/Δ(0) versus T/Tc for some elemental SCs by solving at least two equations numerically: a gap-like and a number equation. In 50-50 symmetry, the energy gap curve agrees quite well with experimental data. But ignoring 2hCPs altogether leads to the gap curve falling substantially below that with 50-50 symmetry which already fits the data quite well, showing that 2hCPs are indispensable to describe SCs.

Interdigitated electrodes as impedance and capacitance biosensors: A review

Science.gov (United States)

Mazlan, N. S.; Ramli, M. M.; Abdullah, M. M. A. B.; Halin, D. S. C.; Isa, S. S. M.; Talip, L. F. A.; Danial, N. S.; Murad, S. A. Z.

2017-09-01

Interdigitated electrodes (IDEs) are made of two individually addressable interdigitated comb-like electrode structures. IDEs are one of the most favored transducers, widely utilized in technological applications especially in the field of biological and chemical sensors due to their inexpensive, ease of fabrication process and high sensitivity. In order to detect and analyze a biochemical molecule or analyte, the impedance and capacitance signal need to be obtained. This paper investigates the working principle and influencer of the impedance and capacitance biosensors. The impedance biosensor depends on the resistance and capacitance while the capacitance biosensor influenced by the dielectric permittivity. However, the geometry and structures of the interdigitated electrodes affect both impedance and capacitance biosensor. The details have been discussed in this paper.

Superconducting gap anisotropy and d-wave pairing in YBa2Cu3O7-δ

Science.gov (United States)

Verma, Sanjeev K.; Gupta, Anushri; Kumari, Anita; Indu, B. D.

2018-02-01

Considering Born-Mayer-Huggins potential as a most suitable potential to study the dynamical properties of high-temperature superconductors (HTS), the many-body quantum dynamics to obtain phonon Green’s functions has been developed via a Hamiltonian that incorporates the contributions of harmonic electron and phonon fields, phonon field anharmonicities, defects and electron-phonon interactions without considering BCS structure. This enables one to develop the quasiparticle renormalized frequency dispersion in the representative high-temperature cuprate superconductor YBa2Cu3O7-δ. The superconducting gap shows substantial changes with increased doping. The in-plane gap study revealed a v-shape gap with a nodal point along kx = ±ky direction for optimum doping (δ = 0.16) and the nodal point vanished in underdoped and overdoped regimes. The dx2-y2 pairing symmetry is observed at optimum doping with the presence of s or dxy components ( < 3%) in underdoped and overdoped regimes.

Enhanced superconductivity of fullerenes

Energy Technology Data Exchange (ETDEWEB)

Washington, II, Aaron L.; Teprovich, Joseph A.; Zidan, Ragaiy

2017-06-20

Methods for enhancing characteristics of superconductive fullerenes and devices incorporating the fullerenes are disclosed. Enhancements can include increase in the critical transition temperature at a constant magnetic field; the existence of a superconducting hysteresis over a changing magnetic field; a decrease in the stabilizing magnetic field required for the onset of superconductivity; and/or an increase in the stability of superconductivity over a large magnetic field. The enhancements can be brought about by transmitting electromagnetic radiation to the superconductive fullerene such that the electromagnetic radiation impinges on the fullerene with an energy that is greater than the band gap of the fullerene.

Cryomodule tests of four Tesla-like cavities in the Superconducting RF Test Facility at KEK

Directory of Open Access Journals (Sweden)

Eiji Kako

2010-04-01

Full Text Available A 6-m cryomodule including four Tesla-like cavities was developed, and was tested in the Superconducting RF Test Facility phase-I at KEK. The performance as a total superconducting cavity system was checked in the cryomodule tests at 2 K with high rf power. One of the four cavities achieved a stable pulsed operation at 32  MV/m, which is higher than the operating accelerating gradient in the ILC. The maximum accelerating gradient (E_{acc,max⁡} obtained in the vertical cw tests was maintained or slightly improved in the cryomodule tests operating in a pulse mode. Compensation of the Lorentz force detuning at 31  MV/m was successfully demonstrated by a piezo tuner and predetuning.

Numerical analysis on effective electric field penetration depth for interdigital impedance sensor

International Nuclear Information System (INIS)

Kim, Chon-ung; Jong, Hakchol; Ro, Cholwu; Pak, Gilhung; Im, Songil; Li, Guofeng; Li, Jie; Song, Yunho

2013-01-01

Interdigital (finger-like) electrodes are widely used for electrical impedance and capacitance tomography of composite dielectric materials and complex insulating structures. Because of their advantages, they are now effectively introduced as capacitance sensors into a variety of industrial branches, agriculture, medical science, biological engineering, military branches, etc. In order to effectively apply the so-called interdigital impedance sensors in practice, of great importance is to optimize the sensor design parameters such as the electric field penetration depth, signal strength and so on. The general design principles of the interdigital capacitance sensor have been discussed for a long time by many researchers. However, there is no consensus on the definition of the effective electric field penetration depth of interdigital electrode. This paper discusses how to determine the effective electric field penetration depth of interdigital sensor on the basis of the refractive principle of electric field intensity and the FEM analyses of electric field distribution and capacitance for the sensor model.

Transformation of the superconducting gap to an insulating pseudogap at a critical hole density in the cuprates

Science.gov (United States)

Liu, Ye-Hua; Wang, Wan-Sheng; Wang, Qiang-Hua; Zhang, Fu-Chun; Rice, T. M.

2017-07-01

We apply the recent wave-packet formalism developed by Ossadnik to describe the origin of the short-range ordered pseudogap state as the hole doping is lowered through a critical density in cuprates. We argue that the energy gain that drives this precursor state to Mott localization, follows from maximizing umklapp scattering near the Fermi energy. To this end, we show how energy gaps driven by umklapp scattering can open on an appropriately chosen surface, as proposed earlier by Yang, Rice, and Zhang. The key feature is that the pairing instability includes umklapp scattering, leading to an energy gap not only in the single-particle spectrum but also in the pair spectrum. As a result the superconducting gap at overdoping is turned into an insulating pseudogap in the antinodal parts of the Fermi surface.

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

Vertical Line Nodes in the Superconducting Gap Structure of Sr_{2}RuO_{4}

Directory of Open Access Journals (Sweden)

E. Hassinger

2017-03-01

Full Text Available There is strong experimental evidence that the superconductor Sr_{2}RuO_{4} has a chiral p-wave order parameter. This symmetry does not require that the associated gap has nodes, yet specific heat, ultrasound, and thermal conductivity measurements indicate the presence of nodes in the superconducting gap structure of Sr_{2}RuO_{4}. Theoretical scenarios have been proposed to account for the existence of deep minima or accidental nodes (minima tuned to zero or below by material parameters within a p-wave state. Other scenarios propose chiral d-wave and f-wave states, with horizontal and vertical line nodes, respectively. To elucidate the nodal structure of the gap, it is essential to know whether the lines of nodes (or minima are vertical (parallel to the tetragonal c axis or horizontal (perpendicular to the c axis. Here, we report thermal conductivity measurements on single crystals of Sr_{2}RuO_{4} down to 50 mK for currents parallel and perpendicular to the c axis. We find that there is substantial quasiparticle transport in the T=0 limit for both current directions. A magnetic field H immediately excites quasiparticles with velocities both in the basal plane and in the c direction. Our data down to T_{c}/30 and down to H_{c2}/100 show no evidence that the nodes are in fact deep minima. Relative to the normal state, the thermal conductivity of the superconducting state is found to be very similar for the two current directions, from H=0 to H=H_{c2}. These findings show that the gap structure of Sr_{2}RuO_{4} consists of vertical line nodes. This rules out a chiral d-wave state. Given that the c-axis dispersion (warping of the Fermi surface in Sr_{2}RuO_{4} varies strongly from sheet to sheet, the small a-c anisotropy suggests that the line nodes are present on all three sheets of the Fermi surface. If imposed by symmetry, vertical line nodes would be inconsistent with a p-wave order parameter for Sr_{2}RuO_{4}. To reconcile the gap structure

Two gap superconductivity in Ba0.55K0.45Fe2As2 single crystals studied by the directional point-contact Andreev reflection spectroscopy

International Nuclear Information System (INIS)

Szabo, P.; Pribulova, Z.; Pristas, G.; Bud'ko, S.L.; Canfield, P.C.; Samuely, P.

2009-01-01

First directional point-contact Andreev reflection spectroscopy on the Ba 0.55 K 0.45 Fe 2 As 2 single crystals is presented. The spectra show significant differences when measured in the ab plane in comparison with those measured in the c direction. In the latter case no traces of superconducting energy gap could be found, just a reduced point-contact conductance persisting up to about 100 K and indicating reduced density of states. On the other hand within the ab plane two nodeless superconducting energy gaps Δ S ∼2-5 meV and Δ L ∼9-11 meV are detected.

Heel erosion and other interdigital disorders in dairy cows

DEFF Research Database (Denmark)

Enevoldsen, Carsten; Gröhn, Y.T.; Thysen, Iver

1991-01-01

Epidemiologic associations between variables obtainable from dairy cow records and the occurrence of heel erosion, interdigital dermatitis, and interdigital hyperplasia at claw trimmings were estimated with multivariable logistic regression analysis on data from 1170 and 542 cows in lactation 1...... and lactations 2 to 9, respectively. In the 17 herds, heel erosion, interdigital dermatitis, and hyperplasia occurred among 43.8, 4.5, and .9% of cows in lactation 1 and among 69.1, 7.6 and 5.9% of cows in lactations 2 to 9, respectively. Severity of heel erosion increased with parity, and risk increased...... with stage of lactation. Strong seasonal effects were present. Various combinations of veterinary treatments were associated with heel erosion and hyperplasia depending on parity, stage of lactation, and the presence of other claw disorders. In contrast, veterinary treatment had a protective effect...

The ATLAS positive ion injector

International Nuclear Information System (INIS)

Shepard, K.W.; Bollinger, L.M.; Pardo, R.C.

1990-01-01

This paper reviews the design, construction status, and beam tests to date of the positive ion injector (PII) which is replacing the tandem injector for the ATLAS heavy-ion facility. PII consists of an ECR ion source on a 350 KV platform injecting a very low velocity superconducting linac. The linac is composed of an independently-phased array of superconducting four-gap interdigital resonators which accelerate over a velocity range of .006 to .05c. In finished form, PII will be able to inject ions as heavy as uranium into the existing ATLAS linac. Although at the present time little more than 50% of the linac is operational, the indenpently-phased array is sufficiently flexible that ions in the lower half of the periodic table can be accelerated and injected into ATLAS. Results of recent operational experience will be discussed. 5 refs

The ATLAS positive ion injector

Energy Technology Data Exchange (ETDEWEB)

Shepard, K.W.; Bollinger, L.M.; Pardo, R.C.

1990-01-01

This paper reviews the design, construction status, and beam tests to date of the positive ion injector (PII) which is replacing the tandem injector for the ATLAS heavy-ion facility. PII consists of an ECR ion source on a 350 KV platform injecting a very low velocity superconducting linac. The linac is composed of an independently-phased array of superconducting four-gap interdigital resonators which accelerate over a velocity range of .006 to .05c. In finished form, PII will be able to inject ions as heavy as uranium into the existing ATLAS linac. Although at the present time little more than 50% of the linac is operational, the indenpently-phased array is sufficiently flexible that ions in the lower half of the periodic table can be accelerated and injected into ATLAS. Results of recent operational experience will be discussed. 5 refs.

Laser activated superconducting switch

International Nuclear Information System (INIS)

Wolf, A.A.

1976-01-01

A superconducting switch or bistable device is described consisting of a superconductor in a cryogen maintaining a temperature just below the transition temperature, having a window of the proper optical frequency band for passing a laser beam which may impinge on the superconductor when desired. The frequency of the laser is equal to or greater than the optical absorption frequency of the superconducting material and is consistent with the ratio of the gap energy of the switch material to Planck's constant, to cause depairing of electrons, and thereby normalize the superconductor. Some embodiments comprise first and second superconducting metals. Other embodiments feature the two superconducting metals separated by a thin film insulator through which the superconducting electrons tunnel during superconductivity

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.

Research on DC-RF superconducting photocathode injector for high average power FELs

International Nuclear Information System (INIS)

Zhao Kui; Hao Jiankui; Hu Yanle; Zhang Baocheng; Quan Shengwen; Chen Jiaer; Zhuang Jiejia

2001-01-01

To obtain high average current electron beams for a high average power Free Electron Laser (FEL), a DC-RF superconducting injector is designed. It consists of a DC extraction gap, a 1+((1)/(2)) superconducting cavity and a coaxial input system. The DC gap, which takes the form of a Pierce configuration, is connected to the 1+((1)/(2)) superconducting cavity. The photocathode is attached to the negative electrode of the DC gap. The anode forms the bottom of the ((1)/(2)) cavity. Simulations are made to model the beam dynamics of the electron beams extracted by the DC gap and accelerated by the superconducting cavity. High quality electron beams with emittance lower than 3 π-mm-mrad can be obtained. The optimization of experiments with the DC gap, as well as the design of experiments with the coaxial coupler have all been completed. An optimized 1+((1)/(2)) superconducting cavity is in the process of being studied and manufactured

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.

Phonon-induced enhancement of the energy gap and critical current of superconducting aluminum films

International Nuclear Information System (INIS)

Seligson, D.; Clarke, J.

1983-01-01

Enhancements of the energy gap Δ and the critical current I/sub c/ have been induced in thin superconducting aluminum films near the transition temperature T/sub c/ by pulses of phonons at approximately 9 GHz. In terms of the change in temperature Vertical BardeltaT/T/sub c/Vertical Bar necessary to produce the same enhancement in equilibrium, the gap enhancement increased smoothly with phonon power at fixed temperature and decreasing temperature at fixed phonon power; however, very close to T/sub c/ the enhancement rolled off. At relatively low phonon powers, the data were in good agreement with the theory of Eckern, Schmid, Schmutz, and Schoen, but at higher power levels the data fell markedly below the predictions of the theory. The critical-current enhancements in terms of Vertical BardeltaT/T/sub c/Vertical Bar were always larger than the gap enhancements at the same temperature and phonon power. At fixed phonon power the critical-current enhancements were nearly independent of temperature, except very close to T/sub c/ where the enhancement became small. The inclusion of the nonequilibrium quasiparticle distribution and the kinetic energy of the supercurrent in the theory relating the critical-current enhancement to the gap enhancement did not resolve the discrepancies between the two enhancements. It appears likely that there is an additional mechanism for critical-current enhancement that has not yet been identified

LT-STM/STS observation of definite superconducting gap states on the multistage crystal surface of Bi2Sr2CaCu2O8+x

International Nuclear Information System (INIS)

Murakami, Hironaru; Aoki, Ryozo

1996-01-01

Low temperature STM/STS observations have been carried out on cleaved BSCCO crystal surfaces. The authors have succeeded in detection of a special layer, probably a CuO 2 or Ca layer exposed on the surface. The STS spectrum which was reproducibly observed on this special site shows a considerably anisotropic but distinct superconducting gap structure with a definite and flat gap bottom region. This gap structure shows significantly different characteristic from another gap structure observed on the BiO layer, which shows a rounded shape at the gap bottom region without any indication of a finite gap state

Superconductivity

International Nuclear Information System (INIS)

Caruana, C.M.

1988-01-01

Despite reports of new, high-temperature superconductive materials almost every day, participants at the First Congress on Superconductivity do not anticipate commercial applications with these materials soon. What many do envision is the discovery of superconducting materials that can function at much warmer, perhaps even room temperatures. Others hope superconductivity will usher in a new age of technology as semiconductors and transistors did. This article reviews what the speakers had to say at the four-day congress held in Houston last February. Several speakers voiced concern that the Reagan administration's apparent lack of interest in funding superconductivity research while other countries, notably Japan, continue to pour money into research and development could hamper America's international competitiveness

Superconducting-electromagnetic hybrid bearing using YBCO bulk blocks for passive axial levitation

Science.gov (United States)

Nicolsky, R.; de Andrade, R., Jr.; Ripper, A.; David, D. F. B.; Santisteban, J. A.; Stephan, R. M.; Gawalek, W.; Habisreuther, T.; Strasser, T.

2000-06-01

A superconducting/electromagnetic hybrid bearing has been designed using active radial electromagnetic positioning and a superconducting passive axial levitator. This bearing has been tested for an induction machine with a vertical shaft. The prototype was conceived as a four-pole, two-phase induction machine using specially designed stator windings for delivering torque and radial positioning simultaneously. The radial bearing uses four eddy-current sensors, displaced 90° from each other, for measuring the shaft position and a PID control system for feeding back the currents. The stator windings have been adapted from the ones of a standard induction motor. The superconducting axial bearing has been assembled with commercial NdFeB permanent magnets and a set of seven top-seeded-melt-textured YBCO large-grain cylindrical blocks. The bearing set-up was previously simulated by a finite element method for different permanent magnet-superconductor block configurations. The stiffness of the superconducting axial bearing has been investigated by measuring by a dynamic method the vertical and transversal elastic constants for different field cooling processes. The resulting elastic constants show a linear dependence on the air gap, i.e. the clearance between the permanent magnet assembly and the set of superconducting large-grain blocks, which is dependent on cooling distance.

Interdigital foot infections: Corynebacterium minutissimum and agents of superficial mycoses

Directory of Open Access Journals (Sweden)

Fatma Mutlu Sariguzel

2014-09-01

Full Text Available Interdigital foot infections are mostly caused initially by dermatophytes, yeasts and less frequently by bacteria. Erythrasma caused by Corynebacterium minutissimum can be confused with superficial mycoses. The aim of the study was to determine the prevalence of the etiologic agents of superficial mycoses and the frequency of Corynebacterium minutissimum in interdigital foot infections. All the samples obtained from the 121 patients with interdigital foot infections were examined directly with the use of 20% potassium hydroxide mounts and Gram stain under the microscope and cultured on Sabouraud's dextrose agar plates. In identification of superficial mycoses, the rate was found to be 14% with the cultural method and 14% with direct microscopic examination. Using a combination of direct microscopic examination and culture, a 33.8% ratio was achieved. In the culture of these samples, the most isolated factor was Trichophyton rubrum (33.7%. In 24 of the patients (19.8% Corynebacterium minutissimum was detected by Gram staining, in 6 of these patients Trichophyton rubrum was found, Trichophyton mentagrophytes was found in 2 and Trichosporon spp. was found in 1. The examination of interdigital foot lesions in the laboratory, the coexistence of erythrasma with dermatophytes and yeast should be considered.

Hole superconductivity

International Nuclear Information System (INIS)

Hirsch, J.E.; Marsiglio, F.

1989-01-01

The authors review recent work on a mechanism proposed to explain high T c superconductivity in oxides as well as superconductivity of conventional materials. It is based on pairing of hole carriers through their direct Coulomb interaction, and gives rise to superconductivity because of the momentum dependence of the repulsive interaction in the solid state environment. In the regime of parameters appropriate for high T c oxides this mechanism leads to characteristic signatures that should be experimentally verifiable. In the regime of conventional superconductors most of these signatures become unobservable, but the characteristic dependence of T c on band filling survives. New features discussed her include the demonstration that superconductivity can result from repulsive interactions even if the gap function does not change sign and the inclusion of a self-energy correction to the hole propagator that reduces the range of band filling where T c is not zero

Anisotropic energy-gaps of iron-based superconductivity from intra-band quasiparticle interference in LiFeAs

Energy Technology Data Exchange (ETDEWEB)

Rost, A.W. [LASSP, Department of Physics, Cornell, Ithaca, NY 14853 (United States); SUPA, School of Physics and Astronomy, Univ. of St Andrews, St Andrews, Fife KY16 9SS (United Kingdom); Allan, M.P. [LASSP, Department of Physics, Cornell, Ithaca, NY 14853 (United States); SUPA, School of Physics and Astronomy, Univ. of St Andrews, St Andrews, Fife KY16 9SS (United Kingdom); CMPMS Department, Brookhaven National Laboratory, Upton, NY 11973 (United States); Mackenzie, A.P. [SUPA, School of Physics and Astronomy, Univ. of St Andrews, St Andrews, Fife KY16 9SS (United Kingdom); Xie, Y. [CMPMS Department, Brookhaven National Laboratory, Upton, NY 11973 (United States); Davis, J.C. [LASSP, Department of Physics, Cornell, Ithaca, NY 14853 (United States); SUPA, School of Physics and Astronomy, Univ. of St Andrews, St Andrews, Fife KY16 9SS (United Kingdom); CMPMS Department, Brookhaven National Laboratory, Upton, NY 11973 (United States); Kavli Institute at Cornell for Nanoscale Science, Cornell, Ithaca, NY 14853 (United States); Kihou, K.; Lee, C.H.; Iyo, A.; Eisaki, H. [AIST, Tsukuba, Ibaraki 305-8568 (Japan); Chuang, T.M. [LASSP, Department of Physics, Cornell, Ithaca, NY 14853 (United States); CMPMS Department, Brookhaven National Laboratory, Upton, NY 11973 (United States); Inst. of Physics, Academica Sinica, Nankang, Taipei 11529, Taiwan (China)

2012-07-01

Cooper pairing in the Fe-based superconductors is thought to occur due to the projection of the antiferromagnetic interactions between iron atoms onto the complex momentum-space electronic structure. A key consequence is that distinct anisotropic energy gaps {Delta}{sub i}(k) with specific relative orientations should occur on the different electronic bands i. To determine this previously unresolved gap structure high-precision spectroscopy is required. Here we introduce the STM technique of intra-band Bogolyubov quasiparticle scattering interference (QPI) to iron-based superconductor studies, focusing on LiFeAs. We identify the QPI signatures of three hole-like dispersions and, by introducing a new QPI technique, determine the magnitude and relative orientations of corresponding anisotropic {Delta}{sub i}(k). Intra-band Bogolyubov QPI therefore yields the spectroscopic information required to identify the mechanism of superconductivity in Fe-based superconductors.

Capability of leaf interdigitation with different inverse planning strategies in Monaco: an investigation of representative tumour sites

International Nuclear Information System (INIS)

Duan, Jinghao; Meng, Xiangjuan; Liu, Tonghai; Yin, Yong

2016-01-01

The aim of this study was to experimentally assess the dosimetric impact of leaf interdigitation using different inverse treatment strategies for representative tumour sites and to identify the situations in which leaf interdigitation can benefit these tumour sites. Sixty previously treated patients (15 nasopharyngeal carcinoma (NPC), 15 multiple brain metastasis (MBM), 15 cervical cancer and 15 prostate cancer) were re-planned for volumetric modulated arc therapy (VMAT), sliding window IMRT (dMLC) and step-and-shoot IMRT (ssIMRT) with and without leaf interdigitation. Various dosimetric variables, such as PTV coverage, OARs sparing, delivery efficiency and planning time, were evaluated for each plan. In addition, a protocol developed by our group was applied to identify the situations in which leaf interdigitation can achieve benefits in clinical practice. Leaf interdigitation produced few benefits in PTV homogeneity for the MBM VMAT plans and NPC ssIMRT plans. For OARs, sparing was equivalent with and without leaf interdigitation. Leaf interdigitation showed an increase in MUs for dMLC plans and a decrease in MUs for ssIMRT plans. Leaf interdigitation resulted in an increase in segments for dMLC plans and a decrease in segments for NPC and MBM ssIMRT plans. For beam on time, leaf interdigitation showed an increase in MBM dMLC, NPC ssIMRT and prostate ssIMRT plans. In addition, leaf interdigitation saved planning time for VMAT and dMLC plans but increased planning time for ssIMRT plans. Leaf interdigitation does not improve plan quality when performing inverse treatment strategies, regardless of whether the target is simple or complex. However, it influences the delivery efficiency and planning time. Based on these observations, our study suggests that leaf interdigitation should be utilized when performing MBM VMAT plans and NPC ssIMRT plans. The online version of this article (doi:10.1186/s13014-016-0655-1) contains supplementary material, which is available to

A Course on Applied Superconductivity Shared by Four Departments

DEFF Research Database (Denmark)

Jensen, Bogi Bech; Abrahamsen, Asger Bech; Sørensen, Mads Peter

2011-01-01

superconductivity the focus was on an application, which could benefit from using superconductors. The application used in this course was superconducting generators for direct drive wind turbines. As part of the course the students built a small-scale superconducting machine and set up finite element models...... of that machine as well as large-scale wind turbine generators with superconductors and also permanent magnet generators. The course was assessed by a student conference contribution and reports from the students. The quality of the course was evaluated by interviewing the students after the course had finished....... The students were very pleased with the course and gave suggestions of how the course could be improved further....

SU-E-T-306: Dosimetric Comparison of Leaf with Or Without Interdigitation in Multiple Brain Metastasis VMAT Treatment Planning

Energy Technology Data Exchange (ETDEWEB)

NONE

2015-06-15

Purpose: To evaluate the effects of leaf with or without interdigitation in multiple brain metastasis volumetric modulated arc therapy (VMAT) plans. Methods: Twenty patients with 2 to 6 brain metastases of our hospital were retrospectively studied to be planned with dual arc VMAT using Monaco 3.3 TPS on the Elekta Synergy linear accelerator. The prescription dose of PTV was 60Gy/30 fractions. Two plans with or without leaf interdigitation were designed. The homogeneity index (HI), conformity index (CI), dose volume histograms (DVHs), monitor unit (MU), treatment time (T), the segments, the dose coverage of the target, were all evaluated. Results: The plans with leaf interdigitation could achieve better CI (p<0.05) than without leaf interdigitation, while no significant difference were found in HI (p> 0.05) and the dose coverage of the target (p> 0.05).The MU,T, and the segments of the plan with leaf interdigitation were more than the plan without leaf interdigitation (p<0.05). There was no significant difference found in radiation dose of spinal cord, lenses and parotids, while the maximum dose of brain stem of leaf without interdigitation was higher than leaf with interdigitation (p< 0.05). It was worth noting that the areas of low dose regions with leaf interdigitation plan were much less than the without leaf interdigitation plan in the doublication planes (p< 0.05). Conclusion: This study shows that leaf with interdigitation has some advantages than leaf without interdigitation in multiple brain metastasis VMAT plans although the clinical relevance remains to be proven.

SU-E-T-306: Dosimetric Comparison of Leaf with Or Without Interdigitation in Multiple Brain Metastasis VMAT Treatment Planning

International Nuclear Information System (INIS)

2015-01-01

Purpose: To evaluate the effects of leaf with or without interdigitation in multiple brain metastasis volumetric modulated arc therapy (VMAT) plans. Methods: Twenty patients with 2 to 6 brain metastases of our hospital were retrospectively studied to be planned with dual arc VMAT using Monaco 3.3 TPS on the Elekta Synergy linear accelerator. The prescription dose of PTV was 60Gy/30 fractions. Two plans with or without leaf interdigitation were designed. The homogeneity index (HI), conformity index (CI), dose volume histograms (DVHs), monitor unit (MU), treatment time (T), the segments, the dose coverage of the target, were all evaluated. Results: The plans with leaf interdigitation could achieve better CI (p<0.05) than without leaf interdigitation, while no significant difference were found in HI (p> 0.05) and the dose coverage of the target (p> 0.05).The MU,T, and the segments of the plan with leaf interdigitation were more than the plan without leaf interdigitation (p<0.05). There was no significant difference found in radiation dose of spinal cord, lenses and parotids, while the maximum dose of brain stem of leaf without interdigitation was higher than leaf with interdigitation (p< 0.05). It was worth noting that the areas of low dose regions with leaf interdigitation plan were much less than the without leaf interdigitation plan in the doublication planes (p< 0.05). Conclusion: This study shows that leaf with interdigitation has some advantages than leaf without interdigitation in multiple brain metastasis VMAT plans although the clinical relevance remains to be proven

Rate-capability study for a four-gap phenolic RPC with a Cs-137 source

CERN Document Server

Lee, Kyong Sei

2014-01-01

We report test results of a prototype four-gap phenolic resistive plate chamber (RPC) with high-rate gamma rays irradiated from a 200-mCi 137Cs source. The detector signals of the prototype four-gap RPC were digitized at charge thresholds of 80, 130, and 170 fC by using a 32-channel front-end-electronics board, previously developed for the current double-gap RPCs in CMS. We confirmed from the test that the cosmic muons were reliably measured with efficiencies higher than 95pct up to a gamma-background rate of 5.3 kHz cm-2. We concluded from the present R and D that use of the current four-gap phenolic RPCs is advantageous to the high-η triggers in CMS in virtue of the high rate capability.

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.

Superconductivity in multilayer perovskite. Weak coupling analysis

International Nuclear Information System (INIS)

Koikegami, Shigeru; Yanagisawa, Takashi

2006-01-01

We investigate the superconductivity of a three-dimensional d-p model with a multilayer perovskite structure on the basis of the second-order perturbation theory within the weak coupling framework. Our model has been designed with multilayer high-T c superconducting cuprates in mind. In our model, multiple Fermi surfaces appear, and the component of a superconducting gap function develops on each band. We have found that the multilayer structure can stabilize the superconductivity in a wide doping range. (author)

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.

Pair Fermi contour and high-temperature superconductivity

CERN Document Server

Belyavsky, V I

2002-01-01

The holes superconducting coupling with the pair high summarized pulse and the relative motion low pulses is considered with an account of the quasi-two-dimensional electron structure of the HTSC-cuprates with the clearly-pronounced nesting of the Fermi contour. The superconducting energy gap and the condensation energy are determined and their dependences on the doping level are qualitatively studied. It is shown that the energy gap takes place in some holes concentration area, limited on both sides. The superconducting state, whereby the condensation energy is positive, originates in the more narrower doping interval inside this area. The hole pair redistribution in the pulse space constitutes the cause of the superconducting state origination by the holes repulsive screened Coulomb interaction. The coupling mechanism discussed hereby, males it possible to explain qualitatively not only the phase diagram basic peculiarities but also the key experimental facts, related to the cuprate HTSC-materials

Simulation, elaboration and analysis of inter-digitated back contacts photovoltaic cells

International Nuclear Information System (INIS)

Nichiporuk, O.

2005-05-01

Solar energy is the most promising and powerful energy source among renewable energies. Photovoltaic electricity is obtained by direct transformation of the sunlight into electricity by means of photovoltaic cells. The objective of this work is to develop photovoltaic cells with back inter-digitated contacts. In the first chapter, we recall the principle of operation and the fundamental parameters of a photovoltaic cell. In a second part, we explain specificities of the inter-digitated back-contact solar cells, as well as the advantages and the disadvantages of such cells. In the second chapter we study the operation of inter-digitated back-contacts solar cells by two dimensional numerical simulation in order to optimize the geometry and doping profiles of the cell. The third chapter relates to the techniques and the methods of characterization of photovoltaic devices and components. In the fourth chapter, we describe the elaboration of inter-digitated back-contact cells. Three technological processes are presented in order to develop a simple technology for cells realization. In particular, we develop the auto-aligned technological process, which enables to elaborate the cells by using only one lithography step. In the last chapter we examine various approaches to reduce the surface recombination: SiO 2 , silicon nitride deposited by UVCVD, hydrogen annealing, etc.. (author)

Simulation, elaboration and analysis of inter-digitated back-contacts photovoltaic cells

International Nuclear Information System (INIS)

Nichiporuk, O.

2005-05-01

Solar energy is the most promising and powerful energy source among renewable energies. Photovoltaic electricity is obtained by direct transformation of the sunlight into electricity by means of photovoltaic cells. The objective of this work is to develop photovoltaic cells with back inter-digitated contacts. In the first chapter, we recall the principle of operation and the fundamental parameters of a photovoltaic cell. In a second part, we explain specificities of the inter-digitated back-contact solar cells, as well as the advantages and the disadvantages of such cells. In the second chapter we study the operation of inter-digitated back-contacts solar cells by two dimensional numerical simulation in order to optimize the geometry and doping profiles of the cell. The third chapter relates to the techniques and the methods of characterization of photovoltaic devices and components. In the fourth chapter, we describe the elaboration of inter-digitated back-contact cells. Three technological processes are presented in order to develop a simple technology for cells realization. In particular, we develop the auto-aligned technological process, which enables to elaborate the cells by using only one lithography step. In the last chapter we examine various approaches to reduce the surface recombination: SiO 2 , silicon nitride deposited by UVCVD, hydrogen annealing, etc... (author)

Two gap superconductivity in Ba{sub 0.55}K{sub 0.45}Fe{sub 2}As{sub 2} single crystals studied by the directional point-contact Andreev reflection spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Szabo, P.; Pribulova, Z. [Centre of Low Temperature Physics, IEP Slovak Academy of Sciences and P.J.Safarik University, Watsonova 47, SK-04001 Kosice (Slovakia); Pristas, G.; Bud' ko, S.L.; Canfield, P.C. [Ames Laboratory and Iowa State University, Ames, IA 50011 (United States); Samuely, P., E-mail: samuely@saske.s [Centre of Low Temperature Physics, IEP Slovak Academy of Sciences and P.J.Safarik University, Watsonova 47, SK-04001 Kosice (Slovakia)

2009-10-15

First directional point-contact Andreev reflection spectroscopy on the Ba{sub 0.55}K{sub 0.45}Fe{sub 2}As{sub 2} single crystals is presented. The spectra show significant differences when measured in the ab plane in comparison with those measured in the c direction. In the latter case no traces of superconducting energy gap could be found, just a reduced point-contact conductance persisting up to about 100 K and indicating reduced density of states. On the other hand within the ab plane two nodeless superconducting energy gaps DELTA{sub S}approx2-5 meV and DELTA{sub L}approx9-11 meV are detected.

Fast, Highly-Sensitive, and Wide-Dynamic-Range Interdigitated Capacitor Glucose Biosensor Using Solvatochromic Dye-Containing Sensing Membrane.

Science.gov (United States)

Khan, Md Rajibur Rahaman; Khalilian, Alireza; Kang, Shin-Won

2016-02-20

In this paper, we proposed an interdigitated capacitor (IDC)-based glucose biosensor to measure different concentrations of glucose from 1 μM to 1 M. We studied four different types of solvatochromic dyes: Auramine O, Nile red, Rhodamine B, and Reichardt's dye (R-dye). These dyes were individually incorporated into a polymer [polyvinyl chloride (PVC)] and N,N-Dimethylacetamide (DMAC) solution to make the respective dielectric/sensing materials. To the best of our knowledge, we report for the first time an IDC glucose biosensing system utilizing a solvatochromic-dye-containing sensing membrane. These four dielectric or sensing materials were individually placed into the interdigitated electrode (IDE) by spin coating to make four IDC glucose biosensing elements. The proposed IDC glucose biosensor has a high sensing ability over a wide dynamic range and its sensitivity was about 23.32 mV/decade. It also has fast response and recovery times of approximately 7 s and 5 s, respectively, excellent reproducibility with a standard deviation of approximately 0.023, highly stable sensing performance, and real-time monitoring capabilities. The proposed IDC glucose biosensor was compared with an IDC, potentiometric, FET, and fiber-optic glucose sensor with respect to response time, dynamic range width, sensitivity, and linearity. We observed that the designed IDC glucose biosensor offered excellent performance.

Emergent Higgsless Superconductivity

Directory of Open Access Journals (Sweden)

Cristina Diamantini M.

2017-01-01

Full Text Available We present a new Higgsless model of superconductivity, inspired from anyon superconductivity but P- and T-invariant and generalizable to any dimension. While the original anyon superconductivity mechanism was based on incompressible quantum Hall fluids as average field states, our mechanism involves topological insulators as average field states. In D space dimensions it involves a (D-1-form fictitious pseudovector gauge field which originates from the condensation of topological defects in compact lowenergy effective BF theories. There is no massive Higgs scalar as there is no local order parameter. When electromagnetism is switched on, the photon acquires mass by the topological BF mechanism. Although the charge of the gapless mode (2 and the topological order (4 are the same as those of the standard Higgs model, the two models of superconductivity are clearly different since the origins of the gap, reflected in the high-energy sectors are totally different. In 2D thi! s type of superconductivity is explicitly realized as global superconductivity in Josephson junction arrays. In 3D this model predicts a possible phase transition from topological insulators to Higgsless superconductors.

Transport through hybrid superconducting/normal nanostructures

Energy Technology Data Exchange (ETDEWEB)

Futterer, David

2013-01-29

We mainly investigate transport through interacting quantum dots proximized by superconductors. For this purpose we extend an existing theory to describe transport through proximized quantum dots coupled to normal and superconducting leads. It allows us to study the influence of a strong Coulomb interaction on Andreev currents and Josephson currents. This is a particularly interesting topic because it combines two competing properties: in superconductors Cooper pairs are formed by two electrons which experience an attractive interaction while two electrons located on a quantum dot repel each other due to the Coulomb interaction. It seems at first glance that transport processes involving Cooper pairs should be suppressed because of the two competing interactions. However, it is possible to proximize the dot in nonequilibrium situations. At first, we study a setup composed of a quantum dot coupled to one normal, one ferromagnetic, and one superconducting lead in the limit of an infinitely-large superconducting gap. Within this limit the coupling between dot and superconductor is described exactly by the presented theory. It leads to the formation of Andreev-bound states (ABS) and an additional bias scheme opens in which a pure spin current, i.e. a spin current with a vanishing associated charge current, can be generated. In a second work, starting from the infinite-gap limit, we perform a systematic expansion of the superconducting gap around infinity and investigate Andreev currents and Josephson currents. This allows us to estimate the validity of infinite-gap calculations for real systems in which the superconducting gap is usually a rather small quantity. We find indications that a finite gap renormalizes the ABS and propose a resummation approach to explore the finite-gap ABS. Despite the renormalization effects the modifications of transport by finite gaps are rather small. This result lets us conclude that the infinite-gap calculation is a valuable tool to

Transport through hybrid superconducting/normal nanostructures

International Nuclear Information System (INIS)

Futterer, David

2013-01-01

We mainly investigate transport through interacting quantum dots proximized by superconductors. For this purpose we extend an existing theory to describe transport through proximized quantum dots coupled to normal and superconducting leads. It allows us to study the influence of a strong Coulomb interaction on Andreev currents and Josephson currents. This is a particularly interesting topic because it combines two competing properties: in superconductors Cooper pairs are formed by two electrons which experience an attractive interaction while two electrons located on a quantum dot repel each other due to the Coulomb interaction. It seems at first glance that transport processes involving Cooper pairs should be suppressed because of the two competing interactions. However, it is possible to proximize the dot in nonequilibrium situations. At first, we study a setup composed of a quantum dot coupled to one normal, one ferromagnetic, and one superconducting lead in the limit of an infinitely-large superconducting gap. Within this limit the coupling between dot and superconductor is described exactly by the presented theory. It leads to the formation of Andreev-bound states (ABS) and an additional bias scheme opens in which a pure spin current, i.e. a spin current with a vanishing associated charge current, can be generated. In a second work, starting from the infinite-gap limit, we perform a systematic expansion of the superconducting gap around infinity and investigate Andreev currents and Josephson currents. This allows us to estimate the validity of infinite-gap calculations for real systems in which the superconducting gap is usually a rather small quantity. We find indications that a finite gap renormalizes the ABS and propose a resummation approach to explore the finite-gap ABS. Despite the renormalization effects the modifications of transport by finite gaps are rather small. This result lets us conclude that the infinite-gap calculation is a valuable tool to

Spin dynamics in the pseudo-gap state of a high-temperature superconductor

Energy Technology Data Exchange (ETDEWEB)

Hinkov, V; Lin, C T; Chen, D P; Keimer, B [Max Planck Inst Solid State Res, D-70569 Stuttgart, (Germany); Bourges, P; Pailhes, S; Sidis, Y [CEA, CNRS, CE Saclay, Lab Leon Brillouin, F-91191 Gif Sur Yvette, (France); Ivanov, A [Inst Max Von Laue Paul Langevin, F-38042 Grenoble, (France); Frost, C D; Perring, T G [Rutherford Appleton Lab, ISIS Facil, Didcot OX11 0QX, Oxon, (United Kingdom)

2007-07-01

The pseudo-gap is one of the most pervasive phenomena of high-temperature superconductors. It is attributed either to incoherent Cooper pairing setting in above the superconducting transition temperature, Tc, or to a hidden order parameter competing with superconductivity. Here, we use inelastic neutron scattering from under-doped YBa{sub 2}Cu{sub 3}O{sub 6.6} to show that the dispersion relations of spin excitations in the superconducting and pseudo-gap states are qualitatively different. Specifically, the extensively studied 'hour glass' shape of the magnetic dispersions in the superconducting state is no longer discernible in the pseudo-gap state and we observe an unusual 'vertical' dispersion with pronounced in-plane anisotropy. The differences between superconducting and pseudo-gap states are thus more profound than generally believed, suggesting a competition between these two states. Whereas the high-energy excitations are common to both states and obey the symmetry of the copper oxide square lattice, the low-energy excitations in the pseudo-gap state may be indicative of collective fluctuations towards a state with broken orientational symmetry predicted in theoretical work. (authors)

Anisotropic superconductivity in β-(BDA-TTP)2SbF6: STM spectroscopy

Science.gov (United States)

Nomura, K.; Muraoka, R.; Matsunaga, N.; Ichimura, K.; Yamada, J.

2009-03-01

We have investigated the gap symmetry in the superconducting phase of β-(BDA-TTP)2SbF6 with use of the scanning tunneling microscope (STM). The tunneling spectra obtained on the conducting surface show a clear superconducting gap structure. Its functional form is of V-shaped similarly to κ-(BEDT-TTF)2X and suggests the anisotropic superconducting gap with line nodes. For lateral surfaces the shape of tunneling spectra varies from the U-shape with relatively large gap to the V-shape with small gap depending on the tunneling direction alternately twice between directional angle 0 and π. From the analysis of conductance curve taking the k dependence of the tunneling probability into account, it is found that the gap has maximum near the a* and c* axes and the nodes appear along near a*+c* and the a-c* directions. These indicate that the d like superconducting pair is formed in this system as the case of κ-(BEDT-TTF)2X. This node direction is consistent with the theoretical prediction based on the spin fluctuation mechanism. However, the zero-bias conductance peak has not been observed yet.

Anisotropic superconductivity in β-(BDA-TTP)2SbF6: STM spectroscopy

International Nuclear Information System (INIS)

Nomura, K.; Muraoka, R.; Matsunaga, N.; Ichimura, K.; Yamada, J.

2009-01-01

We have investigated the gap symmetry in the superconducting phase of β-(BDA-TTP) 2 SbF 6 with use of the scanning tunneling microscope (STM). The tunneling spectra obtained on the conducting surface show a clear superconducting gap structure. Its functional form is of V-shaped similarly to κ-(BEDT-TTF) 2 X and suggests the anisotropic superconducting gap with line nodes. For lateral surfaces the shape of tunneling spectra varies from the U-shape with relatively large gap to the V-shape with small gap depending on the tunneling direction alternately twice between directional angle 0 and π. From the analysis of conductance curve taking the k dependence of the tunneling probability into account, it is found that the gap has maximum near the a* and c* axes and the nodes appear along near a*+c* and the a-c* directions. These indicate that the d x 2 -y 2 like superconducting pair is formed in this system as the case of κ-(BEDT-TTF) 2 X. This node direction is consistent with the theoretical prediction based on the spin fluctuation mechanism. However, the zero-bias conductance peak has not been observed yet

Ultrasonic attenuation in superconducting zinc

International Nuclear Information System (INIS)

Auluck, S.

1978-01-01

The differences in the Zn ultrasonic attenuation data of different workers are analyzed. The superconducting energy gaps deduced from our analysis of the ultrasonic-attenuation data of Cleavelin and Marshall are consistent with the gaps deduced from the knowledge of the Fermi surface and the electron-phonon mass enhancement factor

Phonon-induced enhancements of the energy gap and critical current in superconducting aluminum

International Nuclear Information System (INIS)

Seligson, D.

1983-01-01

The enhancement of the energy gap, Δ, and critical current, i/sub c/, in superconducting aluminum thin films were under the influence of 8 to 10 GHz phonons. The phonons were generated by piezoelectric transduction of a 1 kW microwave pulse of about 1 μsec duration. By means of a quartz delay line, the phonons were allowed to enter the aluminum only after the microwaves had long since disappeared. The critical current was measured in long narrow Al strips, in which the current flow is 1-dimensional and well described by Ginsburg-Landau theory. To measure Δ the Al film was used as one electrode in a superconductor-insulator-superconductor tunnel junction whose current-voltage characteristic gave Δ directly. For the measurements of i/sub c/, the total critical current was measured in the presence of the phonon perturbation. For the measurements of Δ the change of Δ away from its equilibrium value was measured. In both cases the first measurements of enhancement of these macroscopic variables under phonon irradiation is reported. The gap-enhancement was found to be in good agreement with theory, but only for relatively and surprisingly low input power. The critical current measurements are predicted to be in rough agreement with the Δ measurements but this was not observed

A modified BCS theory of heavy fermion superconductivity

International Nuclear Information System (INIS)

Baral, P.C.; Rout, G.C.

2012-01-01

In this paper we derive an expression for the superconducting gap equation for U and Ce based heavy fermion (HF) systems within a modified weak coupling theory of superconductivity. The calculated gap equation presents a mixture of pairing amplitudes of two different quasi-particle bands α and β. These two gap equations are solved numerically and self-consistently within the cut-off energy which arises due to the Kondo energy. It is found that the energy dependence of the enhanced density of states for the HF systems clearly manifests itself in the theory and the Kondo energy naturally takes the role of cut-off energy (ω c ), as long as the effective cut-off energy is large in comparison with the Kondo energy. The numerical analysis confirms this result and shows that superconducting transition temperature is independent of effective cut-off energy employed within this approach. The temperature dependence of gap equations are studied by varying the model parameters like positions of f-level, hybridization and coupling constants of the HF systems. (author)

Multiple scattering theory for superconducting heterostructures

Energy Technology Data Exchange (ETDEWEB)

Ujfalussy, Balazs [Wigner Research Centre for Physics, Budapest (Hungary)

2016-07-01

We generalize the screened Korringa-Kohn-Rostoker method for solving the corresponding Kohn-Sham-Bogoliubov-de Gennes equations for surfaces and interfaces. As an application of the theory, we study the quasiparticle spectrum of Au overlayers on a Nb(100) host. We find that within the superconducting gap region, the quasiparticle spectrum consists of Andreev bound states with a dispersion which is closely connected to the underlying electronic structure of the overlayer. We also find that the spectrum has a strongly k-dependent induced gap. The properties of the gap are discussed in relation to the thickness of the overlayer, and it is shown that certain states do not participate in the Andreev scattering process. From the thickness dependence of the gap size we calculate the superconducting critical temperature of Au/Nb(100) heterostructures what we compare with with experiments. Moreover, predictions are made for similar heterostructures of other compounds.

Experimental Observation of Non-'S-Wave' Superconducting Behavior in Bulk Superconducting Tunneling Junctions of Yba2Cu3O7-δ

Directory of Open Access Journals (Sweden)

Leandro Jose Guerra

1998-06-01

Full Text Available Evidence of non-s-wave superconductivity from normal tunneling experiments in bulk tunneling junctions of YBa2Cu3O7-δ is presented. The I-V and dI/dV characteristics of bulk superconducting tunneling junctions of YBa2Cu3O7-δ have been measured at 77.0K and clear deviation from s-wave superconducting behavior has been observed. The result agrees with d-wave symmetry, and interpreting the data in this way, the magnitude of the superconducting energy gap, 2Δ, is found to be (0.038 ± 0.002 eV. Comparing this energy gap with Tc (2Δ/kB Tc = 5.735, indicates that these high-Tc superconductors are strongly correlated materials, which in contrast with BCS-superconductors are believed to be weakly correlated.

Conduction spectroscopy of a proximity induced superconducting topological insulator

Science.gov (United States)

Stehno, M. P.; Hendrickx, N. W.; Snelder, M.; Scholten, T.; Huang, Y. K.; Golden, M. S.; Brinkman, A.

2017-09-01

The combination of superconductivity and the helical spin-momentum locking at the surface state of a topological insulator (TI) has been predicted to give rise to p-wave superconductivity and Majorana bound states. The superconductivity can be induced by the proximity effect of a s-wave superconductor (S) into the TI. To probe the superconducting correlations inside the TI, dI/dV spectroscopy has been performed across such S-TI interfaces. Both the alloyed Bi1.5Sb0.5Te1.7Se1.3 and the stoichiometric BiSbTeSe2 have been used as three-dimensional TI. In the case of Bi1.5Sb0.5Te1.7Se1.3, the presence of disorder induced electron-electron interactions can give rise to an additional zero-bias resistance peak. For the stoichiometric BiSbTeSe2 with less disorder, tunnel barriers were employed in order to enhance the signal from the interface. The general observations in the spectra of a large variety of samples are conductance dips at the induced gap voltage, combined with an increased sub-gap conductance, consistent with p-wave predictions. The induced gap voltage is typically smaller than the gap of the Nb superconducting electrode, especially in the presence of an intentional tunnel barrier. Additional uncovered spectroscopic features are oscillations that are linearly spaced in energy, as well as a possible second order parameter component.

Pair-breaking effects by parallel magnetic field in electric-field-induced surface superconductivity

International Nuclear Information System (INIS)

Nabeta, Masahiro; Tanaka, Kenta K.; Onari, Seiichiro; Ichioka, Masanori

2016-01-01

Highlights: • Zeeman effect shifts superconducting gaps of sub-band system, towards pair-breaking. • Higher-level sub-bands become normal-state-like electronic states by magnetic fields. • Magnetic field dependence of zero-energy DOS reflects multi-gap superconductivity. - Abstract: We study paramagnetic pair-breaking in electric-field-induced surface superconductivity, when magnetic field is applied parallel to the surface. The calculation is performed by Bogoliubov-de Gennes theory with s-wave pairing, including the screening effect of electric fields by the induced carriers near the surface. Due to the Zeeman shift by applied fields, electronic states at higher-level sub-bands become normal-state-like. Therefore, the magnetic field dependence of Fermi-energy density of states reflects the multi-gap structure in the surface superconductivity.

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.

Energy-gap spectroscopy of superconductors using a tunneling microscope

International Nuclear Information System (INIS)

Le Duc, H.G.; Kaiser, W.J.; Stern, J.A.

1987-01-01

A unique scanning tunneling microscope (STM) system has been developed for spectroscopy of the superconducting energy gap. High-resolution control of tunnel current and voltage allows for measurement of superconducting properties at tunnel resistance levels 10 2 --10 3 greater than that achieved in prior work. The previously used STM methods for superconductor spectroscopy are compared to those developed for the work reported here. Superconducting energy-gap spectra are reported for three superconductors, Pb, PbBi, and NbN, over a range of tunnel resistance. The measured spectra are compared directly to theory

Anisotropic type-I superconductivity and anomalous superfluid density in OsB2

Science.gov (United States)

Bekaert, J.; Vercauteren, S.; Aperis, A.; Komendová, L.; Prozorov, R.; Partoens, B.; Milošević, M. V.

2016-10-01

We present a microscopic study of superconductivity in OsB2, and discuss the origin and characteristic length scales of the superconducting state. From first-principles we show that OsB2 is characterized by three different Fermi sheets, and we prove that this fermiology complies with recent quantum-oscillation experiments. Using the found microscopic properties, and experimental data from the literature, we employ Ginzburg-Landau relations to reveal that OsB2 is a distinctly type-I superconductor with a very low Ginzburg-Landau parameter κ —a rare property among compound materials. We show that the found coherence length and penetration depth corroborate the measured thermodynamic critical field. Moreover, our calculation of the superconducting gap structure using anisotropic Eliashberg theory and ab initio calculated electron-phonon interaction as input reveals a single but anisotropic gap. The calculated gap spectrum is shown to give an excellent account for the unconventional behavior of the superfluid density of OsB2 measured in experiments as a function of temperature. This reveals that gap anisotropy can explain such behavior, observed in several compounds, which was previously attributed solely to a two-gap nature of superconductivity.

Fast, Highly-Sensitive, and Wide-Dynamic-Range Interdigitated Capacitor Glucose Biosensor Using Solvatochromic Dye-Containing Sensing Membrane

Directory of Open Access Journals (Sweden)

Md. Rajibur Rahaman Khan

2016-02-01

Full Text Available In this paper, we proposed an interdigitated capacitor (IDC-based glucose biosensor to measure different concentrations of glucose from 1 μM to 1 M. We studied four different types of solvatochromic dyes: Auramine O, Nile red, Rhodamine B, and Reichardt’s dye (R-dye. These dyes were individually incorporated into a polymer [polyvinyl chloride (PVC] and N,N-Dimethylacetamide (DMAC solution to make the respective dielectric/sensing materials. To the best of our knowledge, we report for the first time an IDC glucose biosensing system utilizing a solvatochromic-dye-containing sensing membrane. These four dielectric or sensing materials were individually placed into the interdigitated electrode (IDE by spin coating to make four IDC glucose biosensing elements. The proposed IDC glucose biosensor has a high sensing ability over a wide dynamic range and its sensitivity was about 23.32 mV/decade. It also has fast response and recovery times of approximately 7 s and 5 s, respectively, excellent reproducibility with a standard deviation of approximately 0.023, highly stable sensing performance, and real-time monitoring capabilities. The proposed IDC glucose biosensor was compared with an IDC, potentiometric, FET, and fiber-optic glucose sensor with respect to response time, dynamic range width, sensitivity, and linearity. We observed that the designed IDC glucose biosensor offered excellent performance.

The superconducting gaps of C-substituted and Al-substituted MgB2 single crystals by point-contact spectroscopy

International Nuclear Information System (INIS)

Daghero, D.; Gonnelli, R.S.; Ummarino, G.A.; Calzolari, A.; Dellarocca, Valeria; Stepanov, V.A.; Zhigadlo, N.; Kazakov, S.M.; Karpinski, J.

2005-01-01

We studied the effects of carbon and aluminum substitutions on the gaps of the two-band superconductor MgB 2 by means of point-contact measurements in Mg(B 1-x C x ) 2 and Mg 1-y Al y B 2 single crystals with 0≤x≤0.132 and 0≤y≤0.21. The gap amplitudes, Δ ω and Δ π , were determined by fitting the conductance curves of the point contacts with the standard Blonder-Tinkham-Klapwijk (BTK) model generalized to the two-band case. Whenever possible, their values were confirmed by the independent fit (with a single-band BTK model) of the partial contribution of the two bands to the conductance, separated by means of a suitable magnetic field B*. In C-substituted crystals, the two gaps remain clearly distinct up to x∝0.10, but at x=0.132 we observed for the first time their merging into a single gap Δ≅3 meV with a gap ratio 2Δ=k B T c close to the standard BCS value. In Al-substituted crystals, we found no evidence of this gap merging. Instead, Δ π reaches the value 0.4 meV at y=0.21, where Δ π saturates at about 4 meV. These results are compared with other recent experimental findings in polycrystals and with the predictions of the models for multiband superconductivity. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Low-frequency and wideband vibration energy harvester with flexible frame and interdigital structure

Energy Technology Data Exchange (ETDEWEB)

Li, Pengwei, E-mail: lipengwei@tyut.edu.cn; Wang, Yanfen; Luo, Cuixian; Li, Gang; Hu, Jie; Zhang, Wendong [MicroNano System Research Center of College of Information Engineering and Key Lab of Advanced Transducers and Intelligent Control System of the Ministry of Education, Taiyuan University of Technology, Taiyuan 030024, Shanxi (China); Liu, Ying [MicroNano System Research Center of College of Information Engineering and Key Lab of Advanced Transducers and Intelligent Control System of the Ministry of Education, Taiyuan University of Technology, Taiyuan 030024, Shanxi (China); Baicheng Ordnance Test Center of China, Baicheng 137000, Jilin (China); Liu, Wei [Baicheng Ordnance Test Center of China, Baicheng 137000, Jilin (China)

2015-04-15

As an alternative to traditional cantilever beam structures and their evolutions, a flexible beam based, interdigital structure, vibration energy harvester has been presented and investigated. The proposed interdigital-shaped oscillator consists of a rectangular flexible frame and series of cantilever beams interdigitally bonded to it. In order to achieve low frequency and wide-bandwidth harvesting, Young’s modulus of materials, frame size and the amount of the cantilevers have been studied systematically. The measured frequency responses of the designed device (PDMS frame, quintuple piezoelectric cantilever beams) show a 460% increase in bandwidth below 80Hz. When excited at an acceleration of 1.0 g, the energy harvester achieves to a maximum open-circuit voltage of 65V, and the maximum output power 4.5 mW.

Superconductivity in heavily boron-doped silicon carbide

Directory of Open Access Journals (Sweden)

Markus Kriener, Takahiro Muranaka, Junya Kato, Zhi-An Ren, Jun Akimitsu and Yoshiteru Maeno

2008-01-01

Full Text Available The discoveries of superconductivity in heavily boron-doped diamond in 2004 and silicon in 2006 have renewed the interest in the superconducting state of semiconductors. Charge-carrier doping of wide-gap semiconductors leads to a metallic phase from which upon further doping superconductivity can emerge. Recently, we discovered superconductivity in a closely related system: heavily boron-doped silicon carbide. The sample used for that study consisted of cubic and hexagonal SiC phase fractions and hence this led to the question which of them participated in the superconductivity. Here we studied a hexagonal SiC sample, free from cubic SiC phase by means of x-ray diffraction, resistivity, and ac susceptibility.

Unusual temperature evolution of superconductivity in LiFeAs

Energy Technology Data Exchange (ETDEWEB)

Nag, Pranab Kumar; Schlegel, Ronny; Baumann, Danny; Grafe, Hans-Joachim; Beck, Robert [Leibniz Institute for Solid State and Materials Research Dresden, IFW Dresden (Germany); Wurmehl, Sabine [Leibniz Institute for Solid State and Materials Research Dresden, IFW Dresden (Germany); Institute for Solid State Physics, TU Dresden (Germany); Buechner, Bernd [Leibniz Institute for Solid State and Materials Research Dresden, IFW Dresden (Germany); Institute for Solid State Physics, TU Dresden (Germany); Center for Transport and Devices, TU Dresden (Germany); Hess, Christian [Leibniz Institute for Solid State and Materials Research Dresden, IFW Dresden (Germany); Center for Transport and Devices, TU Dresden (Germany)

2016-07-01

We have performed temperature dependent scanning tunneling spectroscopy on an impurity-free surface area of a LiFeAs single crystal. Our data reveal a highly unusual temperature evolution of superconductivity: at T{sub c}{sup *}=18 K a partial superconducting gap opens, as is evidenced by subtle, yet clear features in the tunneling spectra, i.e. particle-hole symmetric coherence peaks and dip-hump structures. At T{sub c}=16 K, these features substantiate dramatically and become characteristic of full superconductivity. Remarkably, this is accompanied by an almost jump-like increase of the gap energy at T{sub c} to about 87% of its low-temperature gap value. The energy of the dip as measured by its distance to the coherence peak remains practically constant in the whole temperature regime T ≤ T{sub c}{sup *}. We compare these findings with established experimental and theoretical results.

Characterization of superconducting thin films by infrared reflection

International Nuclear Information System (INIS)

Gervais, F.

1988-01-01

Infrared reflectivity spectroscopy is shown to be a powerful tool to characterize the new high-Tc oxide superconductors since it gives information about the superconducting gap, phonons, plasmon and possibly low-energy electronic excitations such as excitons, information relevant to understand the mechanism of superconductivity [fr

Thermal expansion of coexistence of ferromagnetism and superconductivity

International Nuclear Information System (INIS)

Hatayama, Nobukuni; Konno, Rikio

2010-01-01

The temperature dependence of thermal expansion of coexistence of ferromag-netism and superconductivity below the superconducting transition temperature T cu of a majority spin conduction band is investigated. Majority spin and minority spin superconducting gaps exist in the coexistent state. We assume that the Curie temperature is much larger than the superconducting transition temperatures. The free energy that Linder et al. [Phys. Rev. B76, 054511 (2007)] derived is used. The thermal expansion of coexistence of ferromagnetism and superconductivity is derived by the application of the method of Takahashi and Nakano [J. Phys.: Condens. Matter 18, 521 (2006)]. We find that we have the anomalies of the thermal expansion in the vicinity of the superconducting transition temperatures.

Fabrication of interdigitated electrodes by inkjet printing technology for apllication in ammonia sensing

International Nuclear Information System (INIS)

Le, Duy Dam; Nguyen, Thi Ngoc Nhien; Doan, Duc Chanh Tin; Dang, Thi My Dung; Dang, Mau Chien

2016-01-01

In this paper interdigitated electrodes for gas sensors were fabricated by inkjet printing technology. Silver electrodes were inkjet printed on Si/SiO 2 substrates instead of traditional photolithography method. The inkjet printing parameters to obtain desired dimensions, thickness of the electrodes and distance between the interdigitated electrodes were optimized in this study. The fabricated interdigitated silver electrodes were tested for application in ammonia gas sensors. Conductive polyaniline (PANI) layer was coated on the silver interdigitated electrodes by drop-coating. Ammonia detection of the PANI-coated chips was characterized with a gas measurement system in which humidity and ammonia concentrations were well-controlled. The electrical conductivity of the PANI films coated on the electrodes was measured when the PANI films were exposed to nitrogen and ammonia. The conductivity of the PANI films decreased significantly due to the deprotonation process of PANI upon ammonia expodure. The recovery time was about 15 min by heating up the polymer chip at 60 °C. The results showed that the silver electrodes fabricated by inkjet printing technique could be used as a sensor platform for ammonia detection. (paper)

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.

Optimization of the coplanar interdigital capacitive sensor

Science.gov (United States)

Huang, Yunzhi; Zhan, Zheng; Bowler, Nicola

2017-02-01

Interdigital capacitive sensors are applied in nondestructive testing and material property characterization of low-conductivity materials. The sensor performance is typically described based on the penetration depth of the electric field into the sample material, the sensor signal strength and its sensitivity. These factors all depend on the geometry and material properties of the sensor and sample. In this paper, a detailed analysis is provided, through finite element simulations, of the ways in which the sensor's geometrical parameters affect its performance. The geometrical parameters include the number of digits forming the interdigital electrodes and the ratio of digit width to their separation. In addition, the influence of the presence or absence of a metal backplane on the sample is analyzed. Further, the effects of sensor substrate thickness and material on signal strength are studied. The results of the analysis show that it is necessary to take into account a trade-off between the desired sensitivity and penetration depth when designing the sensor. Parametric equations are presented to assist the sensor designer or nondestructive evaluation specialist in optimizing the design of a capacitive sensor.

Ultrasensitive interdigitated capacitance immunosensor using gold nanoparticles

Science.gov (United States)

Alizadeh Zeinabad, Hojjat; Ghourchian, Hedayatollah; Falahati, Mojtaba; Fathipour, Morteza; Azizi, Marzieh; Boutorabi, Seyed Mehdi

2018-06-01

Immunosensors based on interdigitated electrodes (IDEs), have recently demonstrated significant improvements in the sensitivity of capacitance detection. Herein, a novel type of highly sensitive, compact and portable immunosensor based on a gold interdigital capacitor has been designed and developed for the rapid detection of hepatitis B surface antigen (HBsAg). To improve the efficiency of antibody immobilization and time-saving, a self-assembled monolayer (SAM) of 2-mercaptoethylamine film was coated on IDEs. Afterwards, carboxyl groups on primary antibodies were activated through 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and were immobilized on amino-terminated SAM for better control of the oriented immobilization of antibodies on gold IDEs. In addition, gold nanoparticles conjugated with a secondary antibody were used to enhance the sensitivity. Under optimal conditions, the immunosensor exhibited the sensitivity of 0.22 nF.pg ml–1, the linear range from 5 pg ml‑1 to 1 ng ml–1 and the detection limit of 1.34 pg ml‑1, at a signal-to-noise ratio of 3.

A new perspective on anisotropy and multiple energy gaps in superconductors

International Nuclear Information System (INIS)

Milkove, K.R.; Bostock, J.; MacVicar, M.L.A.

1976-01-01

New perspective on superconducting anisotropy and multiple energy gaps: direct experimental evidence shows that widely accepted anisotropy and multiple energy gap interpretations of tunneling data are consistent with a voltage divider model and may not relate to intrinsic superconducting properties. The model also accounts for other common data anomalies. (author)

WORKSHOP: Radiofrequency superconductivity

Energy Technology Data Exchange (ETDEWEB)

Anon.

1984-10-15

The Second Workshop on Radiofrequency Superconductivity was held at CERN from 23-27 July, four years after the first, organized at Karlsruhe. 35 invited talks were presented to the about 80 participants from Australia, Brazil, Europe, Japan and the United States. For the first time, ten Laboratories operating or planning superconducting accelerators for heavy ions participated and shared their experience with the community proposing the use of superconducting accelerating sections for electron accelerators.

WORKSHOP: Radiofrequency superconductivity

International Nuclear Information System (INIS)

Anon.

1984-01-01

The Second Workshop on Radiofrequency Superconductivity was held at CERN from 23-27 July, four years after the first, organized at Karlsruhe. 35 invited talks were presented to the about 80 participants from Australia, Brazil, Europe, Japan and the United States. For the first time, ten Laboratories operating or planning superconducting accelerators for heavy ions participated and shared their experience with the community proposing the use of superconducting accelerating sections for electron accelerators

Low-frequency and wideband vibration energy harvester with flexible frame and interdigital structure

Directory of Open Access Journals (Sweden)

Pengwei Li

2015-04-01

Full Text Available As an alternative to traditional cantilever beam structures and their evolutions, a flexible beam based, interdigital structure, vibration energy harvester has been presented and investigated. The proposed interdigital-shaped oscillator consists of a rectangular flexible frame and series of cantilever beams interdigitally bonded to it. In order to achieve low frequency and wide-bandwidth harvesting, Young’s modulus of materials, frame size and the amount of the cantilevers have been studied systematically. The measured frequency responses of the designed device (PDMS frame, quintuple piezoelectric cantilever beams show a 460% increase in bandwidth below 80Hz. When excited at an acceleration of 1.0 g, the energy harvester achieves to a maximum open-circuit voltage of 65V, and the maximum output power 4.5 mW.

High-Tc superconductivity in the d-p electron system

International Nuclear Information System (INIS)

Ivanov, V.A.; Zaitsev, R.A.

1991-01-01

The relaxation time with spin flip τ s and the parameters ξ, δ, χ of superconducting phase have been calculated on the basis of the kinematical mechanism of superconductivity in strongly correlated oxide models. An inter-relation between the superconducting gap Δ o and the specific heat jump Δ c allowing the experimental verification was obtained and the Ginsburg-Landau equation derived. (author). 8 refs., 2 figs

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

{sup 119}Sn-NMR investigations on superconducting Ca{sub 3}Ir{sub 4}Sn{sub 13}: Evidence for multigap superconductivity

Energy Technology Data Exchange (ETDEWEB)

Sarkar, R., E-mail: rajibsarkarsinp@gmail.com [Institute for Solid State Physics, TU Dresden, D-01069 Dresden (Germany); Brückner, F.; Günther, M. [Institute for Solid State Physics, TU Dresden, D-01069 Dresden (Germany); Wang, Kefeng; Petrovic, C. [Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY 11973 (United States); Biswas, P.K.; Luetkens, H.; Morenzoni, E.; Amato, A. [Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, CH-5232 Villigen PSI (Switzerland); Klauss, H-H. [Institute for Solid State Physics, TU Dresden, D-01069 Dresden (Germany)

2015-12-15

We report bulk superconductivity (SC) in Ca{sub 3}Ir{sub 4}Sn{sub 13} by means of {sup 119}Sn nuclear magnetic resonance (NMR) experiments. Two classical signatures of BCS superconductivity in spin-lattice relaxation rate (1/T{sub 1}), namely the Hebel–Slichter coherence peak just below the T{sub c}, and the exponential decay in the superconducting phase, are evident. The noticeable decrease of {sup 119}Sn Knight shift below T{sub c} indicates spin-singlet superconductivity. The temperature dependence of the spin-lattice relaxation rate {sup 119}(1/T{sub 1}) is convincingly described by the multigap isotropic superconducting gap. NMR experiments do not witness any sign of enhanced spin fluctuations.

Superconducting superferric dipole magnet with cold iron core for the VLHC

CERN Document Server

Foster, G W

2002-01-01

Magnetic system of the stage I Very Large Hadron Collider (VLHC) is based on 2 Tesla superconducting magnets with combined functions. These magnets have a room temperature iron yoke with two 20 mm air gaps. Magnetic field in both horizontally separated air gaps is generated by a single, 100 kA superconducting transmission line. An alternative design with a cold iron yoke, horizontally or vertically separated air gaps is under investigation. The cold iron option with horizontally separated air gaps reduces the amount of iron, which is one of the major cost drivers for the 233-km magnet system of future accelerator. The vertical beam separation decreases the superconductor volume, heat load from the synchrotron radiation and eliminates fringe field from the return bus. Nevertheless, the horizontal beam separation provides lowest volume of the iron yoke and, therefore, smaller heat load on the cryogenic system during cooling down. All these options are discussed and compared in the paper. Superconducting correct...

Superconducting Sweet-Spot in Microcrystalline Graphite Revealed by Point-Contact Spectroscopy

Science.gov (United States)

Arnold, F.; Nyéki, J.; Saunders, J.

2018-05-01

In this letter we describe the observation of a magnetic field dependent electronic gap, suggestive of local superconductivity, in the point-contact spectrum of micro-crystalline graphite. Magnetic field dependent point-contact spectroscopy was carried out at a temperature of 1.8K using an etched aluminium tip. At zero field a gap structure in the differential conductance is observed, showing a gap of Δ = 4.2 meV. On applying magnetic fields of up to 500mT, this gap gradually closes, following the theoretical prediction by Ginzburg and Landau for a fully flux-penetrated superconductor. By applying BCS-theory, we infer a critical superconducting temperature of 14K.

Superconductivity versus quantum criticality: Effects of thermal fluctuations

Science.gov (United States)

Wang, Huajia; Wang, Yuxuan; Torroba, Gonzalo

2018-02-01

We study the interplay between superconductivity and non-Fermi liquid behavior of a Fermi surface coupled to a massless SU(N ) matrix boson near the quantum critical point. The presence of thermal infrared singularities in both the fermionic self-energy and the gap equation invalidates the Eliashberg approximation, and makes the quantum-critical pairing problem qualitatively different from that at zero temperature. Taking the large N limit, we solve the gap equation beyond the Eliashberg approximation, and obtain the superconducting temperature Tc as a function of N . Our results show an anomalous scaling between the zero-temperature gap and Tc. For N greater than a critical value, we find that Tc vanishes with a Berezinskii-Kosterlitz-Thouless scaling behavior, and the system retains non-Fermi liquid behavior down to zero temperature. This confirms and extends previous renormalization-group analyses done at T =0 , and provides a controlled example of a naked quantum critical point. We discuss the crucial role of thermal fluctuations in relating our results with earlier work where superconductivity always develops due to the special role of the first Matsubara frequency.

Design study of the KIRAMS-430 superconducting cyclotron magnet

International Nuclear Information System (INIS)

Kim, Hyun Wook; Kang, Joonsun; Hong, Bong Hwan; Jung, In Su

2016-01-01

Design study of superconducting cyclotron magnet for the carbon therapy was performed at the Korea Institute of Radiological and Medical Science (KIRAMS). The name of this project is The Korea Heavy Ion Medical Accelerator (KHIMA) project and a fixed frequency cyclotron with four spiral sector magnet was one of the candidate for the accelerator type. Basic parameters of the cyclotron magnet and its characteristics were studied. The isochronous magnetic field which can guide the "1"2C"6"+ ions up to 430 MeV/u was designed and used for the single particle tracking simulation. The isochronous condition of magnetic field was achieved by optimization of sector gap and width along the radius. Operating range of superconducting coil current was calculated and changing of the magnetic field caused by mechanical deformations of yokes was considered. From the result of magnetic field design, structure of the magnet yoke was planned.

Design study of the KIRAMS-430 superconducting cyclotron magnet

Energy Technology Data Exchange (ETDEWEB)

Kim, Hyun Wook; Kang, Joonsun, E-mail: genuinei@kirams.re.kr; Hong, Bong Hwan; Jung, In Su

2016-07-01

Design study of superconducting cyclotron magnet for the carbon therapy was performed at the Korea Institute of Radiological and Medical Science (KIRAMS). The name of this project is The Korea Heavy Ion Medical Accelerator (KHIMA) project and a fixed frequency cyclotron with four spiral sector magnet was one of the candidate for the accelerator type. Basic parameters of the cyclotron magnet and its characteristics were studied. The isochronous magnetic field which can guide the {sup 12}C{sup 6+} ions up to 430 MeV/u was designed and used for the single particle tracking simulation. The isochronous condition of magnetic field was achieved by optimization of sector gap and width along the radius. Operating range of superconducting coil current was calculated and changing of the magnetic field caused by mechanical deformations of yokes was considered. From the result of magnetic field design, structure of the magnet yoke was planned.

Theory of spin-fluctuation induced superconductivity in iron-based superconductors

International Nuclear Information System (INIS)

Zhang, Junhua

2011-01-01

In this dissertation we focus on the investigation of the pairing mechanism in the recently discovered high-temperature superconductor, iron pnictides. Due to the proximity to magnetic instability of the system, we considered short-range spin fluctuations as the major mediating source to induce superconductivity. Our calculation supports the magnetic fluctuations as a strong candidate that drives Cooper-pair formation in this material. We find the corresponding order parameter to be of the so-called ss-wave type and show its evolution with temperature as well as the capability of supporting high transition temperature up to several tens of Kelvin. On the other hand, our itinerant model calculation shows pronounced spin correlation at the observed antiferromagnetic ordering wave vector, indicating the underlying electronic structure in favor of antiferromagnetic state. Therefore, the electronic degrees of freedom could participate both in the magnetic and in the superconducting properties. Our work shows that the interplay between magnetism and superconductivity plays an important role to the understanding of the rich physics in this material. The magnetic-excitation spectrum carries important information on the nature of magnetism and the characteristics of superconductivity. We analyze the spin excitation spectrum in the normal and superconducting states of iron pnictides in the magnetic scenario. As a consequence of the sign-reversed gap structure obtained in the above, a spin resonance mode appears below the superconducting transition temperature. The calculated resonance energy, scaled with the gap magnitude and the magnetic correlation length, agrees well with the inelastic neutron scattering (INS) measurements. More interestingly, we find a common feature of those short-range spin fluctuations that are capable of inducing a fully gapped ss state is the momentum anisotropy with elongated span along the direction transverse to the antiferromagnetic momentum

Anisotropic superconductivity in {beta}-(BDA-TTP){sub 2}SbF{sub 6}: STM spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Nomura, K. [Department of Physics, Hokkaido University, Sapporo 060-0810 (Japan)], E-mail: knmr@phys.sci.hokudai.ac.jp; Muraoka, R.; Matsunaga, N. [Department of Physics, Hokkaido University, Sapporo 060-0810 (Japan); Ichimura, K. [Division of Applied Physics, Hokkaido University, Sapporo 060-8628 (Japan); Yamada, J. [Division of Material Science, University of Hyogo, Hyogo 678-1297 (Japan)

2009-03-01

We have investigated the gap symmetry in the superconducting phase of {beta}-(BDA-TTP){sub 2}SbF{sub 6} with use of the scanning tunneling microscope (STM). The tunneling spectra obtained on the conducting surface show a clear superconducting gap structure. Its functional form is of V-shaped similarly to {kappa}-(BEDT-TTF){sub 2}X and suggests the anisotropic superconducting gap with line nodes. For lateral surfaces the shape of tunneling spectra varies from the U-shape with relatively large gap to the V-shape with small gap depending on the tunneling direction alternately twice between directional angle 0 and {pi}. From the analysis of conductance curve taking the k dependence of the tunneling probability into account, it is found that the gap has maximum near the a* and c* axes and the nodes appear along near a*+c* and the a-c* directions. These indicate that the d{sub x{sup 2}-y{sup 2}} like superconducting pair is formed in this system as the case of {kappa}-(BEDT-TTF){sub 2}X. This node direction is consistent with the theoretical prediction based on the spin fluctuation mechanism. However, the zero-bias conductance peak has not been observed yet.

Design of a superconducting wiggler system

International Nuclear Information System (INIS)

Shen, S.S.; Miller, J.R.; Heim, J.R.; Slack, D.S.

1988-01-01

We present a wiggler system based on currently available superconducting technology. The system is designed to provide maximum central field of 4.4 tesla with a specified period length of 160 mm and a gap of 40 mm, while meeting the field quality requirements along all axes. Also included are preliminary cost estimates and a survey of world-wide RandD efforts on superconducting wiggler systems. 12 refs., 6 figs., 3 tabs

Thermal stress in flexible interdigital transducers with anisotropic electroactive cellulose substrates

Science.gov (United States)

Yoon, Sean J.; Kim, Jung Woong; Kim, Hyun Chan; Kang, Jinmo; Kim, Jaehwan

2017-12-01

Thermal stress in flexible interdigital transducers a reliability concern in the development of flexible devices, which may lead to interface delamination, stress voiding and plastic deformation. In this paper, a mathematical model is presented to investigate the effect of material selections on the thermal stress in interdigital transducers. We modified the linear relationships in the composite materials theory with the effect of high curvature, anisotropic substrate and small substrate thickness. We evaluated the thermal stresses of interdigital transducers, fabricated with various electrodes, insulators and substrate materials for the comparison. The results show that, among various insulators, organic polymer developed the highest stress level while oxide showed the lowest stress level. Aluminium shows a higher stress level and curvature as an electrode than gold. As substrate materials, polyimide and electroactive cellulose show similar stress levels except the opposite sign convention to each other. Polyimide shows positive curvatures while electroactive cellulose shows negative curvatures, which is attributed to the stress and thermal expansion state of the metal/insulator composite. The results show that the insulator is found to be responsible for the confinement across the metal lines while the substrate is responsible for the confinement along the metal lines.

Micromachined Planar Supercapacitor with Interdigital Buckypaper Electrodes

Directory of Open Access Journals (Sweden)

Yun-Ting Chen

2018-05-01

Full Text Available In this work, a flexible micro-supercapacitor with interdigital planar buckypaper electrodes is presented. A simple fabrication process involving vacuum filtration method and SU-8 molding techniques is proposed to fabricate in-plane interdigital buckypaper electrodes on a membrane filter substrate. The proposed process exhibits excellent flexibility for future integration of the micro-supercapacitors (micro-SC with other electronic components. The device’s maximum specific capacitance measured using cyclic voltammetry was 107.27 mF/cm2 at a scan rate of 20 mV/s. The electrochemical stability was investigated by measuring the performance of charge-discharge at different discharge rates. Devices with different buckypaper electrode thicknesses were also fabricated and measured. The specific capacitance of the proposed device increased linearly with the buckypaper electrode thickness. The measured leakage current was approximately 9.95 µA after 3600 s. The device exhibited high cycle stability, with 96.59% specific capacitance retention after 1000 cycles. A Nyquist plot of the micro-SC was also obtained by measuring the impedances with frequencies from 1 Hz to 50 kHz; it indicated that the equivalent series resistance value was approximately 18 Ω.

On the mechanism of high-temperature superconductivity in hydrogen sulfide at 200 GPa: Transition into superconducting anti-adiabatic state in coupling to H-vibrations

Directory of Open Access Journals (Sweden)

Pavol Baňacký

Full Text Available It has been shown that the adiabatic electronic structure of the superconducting phase of sulfur hydride at 200 GPa is unstable toward the vibration motion of H-atoms. A theoretical study indicates that in coupling to H-vibrations, the system undergoes a transition from adiabatic into a stabilized anti-adiabatic multi-gap superconducting state at a temperature that can reach 203 K. Keywords: Superconductivity of sulfur hydride, Electron–phonon coupling in superconductors, Anti-adiabatic theory of superconductivity

Bridging the Gap for High-Coherence, Strongly Coupled Superconducting Qubits

Science.gov (United States)

Yoder, Jonilyn; Kim, David; Baldo, Peter; Day, Alexandra; Fitch, George; Holihan, Eric; Hover, David; Samach, Gabriel; Weber, Steven; Oliver, William

Crossovers can play a critical role in increasing superconducting qubit device performance, as long as device coherence can be maintained even with the increased fabrication and circuit complexity. Specifically, crossovers can (1) enable a fully-connected ground plane, which reduces spurious modes and crosstalk in the circuit, and (2) increase coupling strength between qubits by facilitating interwoven qubit loops with large mutual inductances. Here we will describe our work at MIT Lincoln Laboratory to integrate superconducting air bridge crossovers into the fabrication of high-coherence capacitively-shunted superconducting flux qubits. We will discuss our process flow for patterning air bridges by resist reflow, and we will describe implementation of air bridges within our circuits. This research was funded in part by the Office of the Director of National Intelligence (ODNI), Intelligence Advanced Research Projects Activity (IARPA) and by the Assistant Secretary of Defense for Research and Engineering under Air Force Contract No. FA8721-05-C-0002. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of ODNI, IARPA, or the US Government.

Redox cycling with facing interdigitated array electrodes as a method for selective detection of redox species

NARCIS (Netherlands)

Dam, T.V.A.; Olthuis, Wouter; van den Berg, Albert

2007-01-01

A pair of interdigitated ultramicroelectrodes (UMEs) is used to electrochemically detect a weak reductor ( dopamine) in the presence of a stronger one (K-4[ Fe(CN)(6)]). In the mixture of both reductors, one of the two interdigitated electrodes ( the generator electrode) is used to oxidize both

Superconducting proximity effect in topological materials

Science.gov (United States)

Reeg, Christopher R.

In recent years, there has been a renewed interest in the proximity effect due to its role in the realization of topological superconductivity. In this dissertation, we discuss several results that have been obtained in the field of proximity-induced superconductivity and relate the results to the search for Majorana fermions. First, we show that repulsive electron-electron interactions can induce a non-Majorana zero-energy bound state at the interface between a conventional superconductor and a normal metal. We show that this state is very sensitive to disorder, owing to its lack of topological protection. Second, we show that Rashba spin-orbit coupling, which is one of the key ingredients in engineering a topological superconductor, induces triplet pairing in the proximity effect. When the spin-orbit coupling is strong (i.e., when the characteristic energy scale for spin-orbit coupling is comparable to the Fermi energy), the induced singlet and triplet pairing amplitudes can be comparable in magnitude. Finally, we discuss how the size of the proximity-induced gap, which appears in a low-dimensional material coupled to a superconductor, evolves as the thickness of the (quasi-)low-dimensional material is increased. We show that the induced gap can be comparable to the bulk energy gap of the underlying superconductor in materials that are much thicker than the Fermi wavelength, even in the presence of an interfacial barrier and strong Fermi surface mismatch. This result has important experimental consequences for topological superconductivity, as a sizable gap is required to isolate and detect the Majorana modes.

New universality class for superconducting order parameter

International Nuclear Information System (INIS)

Dobroliubov, M.I.; Khlebnikov, S.Yu.

1991-04-01

We present a model of superconductivity with pairing due to Aharonov-Bohm forces. The gap is proportional to the first power of the small parameter (in which the self-consistent perturbation scheme is developed), as opposed to the BCS class of models where the gap is exponentially suppressed with the small parameter. (orig.)

Redox cycling with facing interdigitated array electrodes as a method for selective detection of redox species

NARCIS (Netherlands)

Dam, V.A.T.; Olthuis, W.; Berg, van den A.

2007-01-01

A pair of interdigitated ultramicroelectrodes (UMEs) is used to electrochemically detect a weak reductor (dopamine) in the presence of a stronger one (K4[Fe(CN)6]). In the mixture of both reductors, one of the two interdigitated electrodes (the generator electrode) is used to oxidize both species at

A novel Ka-band coaxial transit-time oscillator with a four-gap buncher

Energy Technology Data Exchange (ETDEWEB)

Song, Lili; He, Juntao; Ling, Junpu [College of Optoelectronic Science and Engineering, National University of Defense Technology, Changsha 410073 (China)

2015-05-15

A novel Ka-band coaxial transit-time oscillator (TTO) with a four-gap buncher is proposed and investigated. Simulation results show that an output power of 1.27 GW and a frequency of 26.18 GHz can be achieved with a diode voltage of 447 kV and a beam current of 7.4 kA. The corresponding power efficiency is 38.5%, and the guiding magnetic field is 0.6 T. Studies and analysis indicate that a buncher with four gaps can modulate the electron beam better than the three-gap buncher in such a Ka-band TTO. Moreover, power efficiency increases with the coupling coefficient between the buncher and the extractor. Further simulation demonstrates that power efficiency can reach higher than 30% with a guiding magnetic field of above 0.5 T. Besides, the power efficiency exceeds 30% in a relatively large range of diode voltage from 375 kV to 495 kV.

Crystalline color superconductivity

International Nuclear Information System (INIS)

Alford, Mark; Bowers, Jeffrey A.; Rajagopal, Krishna

2001-01-01

In any context in which color superconductivity arises in nature, it is likely to involve pairing between species of quarks with differing chemical potentials. For suitable values of the differences between chemical potentials, Cooper pairs with nonzero total momentum are favored, as was first realized by Larkin, Ovchinnikov, Fulde, and Ferrell (LOFF). Condensates of this sort spontaneously break translational and rotational invariance, leading to gaps which vary periodically in a crystalline pattern. Unlike the original LOFF state, these crystalline quark matter condensates include both spin-zero and spin-one Cooper pairs. We explore the range of parameters for which crystalline color superconductivity arises in the QCD phase diagram. If in some shell within the quark matter core of a neutron star (or within a strange quark star) the quark number densities are such that crystalline color superconductivity arises, rotational vortices may be pinned in this shell, making it a locus for glitch phenomena

Hard gap in epitaxial semiconductor-superconductor nanowires

DEFF Research Database (Denmark)

Chang, W.; Albrecht, S. M.; Jespersen, T. S.

2015-01-01

a continuum of subgap states---a situation that nullifies topological protection. Here, we report a hard superconducting gap induced by proximity effect in a semiconductor, using epitaxial Al-InAs superconductor-semiconductor nanowires. The hard gap, along with favorable material properties and gate...

Strongly correlated impurity band superconductivity in diamond: X-ray spectroscopic evidence

Directory of Open Access Journals (Sweden)

G. Baskaran

2006-01-01

Full Text Available In a recent X-ray absorption study in boron doped diamond, Nakamura et al. have seen a well isolated narrow boron impurity band in non-superconducting samples and an additional narrow band at the chemical potential in a superconducting sample. We interpret the beautiful spectra as evidence for upper Hubbard band of a Mott insulating impurity band and an additional metallic 'mid-gap band' of a conducting 'self-doped' Mott insulator. This supports the basic framework of a recent theory of the present author of strongly correlated impurity band superconductivity (impurity band resonating valence bond, IBRVB theory in a template of a wide-gap insulator, with no direct involvement of valence band states.

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

Holographic Superconductivity with Gauss-Bonnet gravity

OpenAIRE

Gregory, Ruth

2010-01-01

I review recent work on holographic superconductivity with Einstein-Gauss-Bonnet gravity, and show how the critical temperature of the superconductor depends on both gravitational backreaction and the Gauss-Bonnet parameter, using both analytic and numerical arguments. I also review computations of the conductivity, finding the energy gap, and demonstrating that there is no universal gap ratio, $\\omega_g/T_c$, for these superconductors.

Flux sensitivity of a piecewise normal and superconducting metal loop

International Nuclear Information System (INIS)

Buettiker, M.; Klapwijk, T.M.

1986-01-01

We consider a loop composed of a superconducting segment and a normal segment with an Aharonov-Bohm flux through the hole of the loop. The normal segment is assumed to be long compared to the superconducting coherence length xi but short compared to a mean inelastic diffusion length. The elementary excitation spectrum of the ground state of this loop is periodic with period hc/2e as long as the superconducting segment is larger than xi. If the superconducting segment length becomes of the order of xi, quasiparticles can tunnel through the superconducting gap and give rise to an excitation spectrum which is periodic with period hc/e. .AE

Terahertz Mixing Characteristics of NbN Superconducting Tunnel Junctions and Related Astronomical Observations

Science.gov (United States)

Li, J.

2010-01-01

High-sensitivity superconducting SIS (superconductor-insulator-superconductor) mixers are playing an increasingly important role in the terahertz (THz) astronomical observation, which is an emerging research frontier in modern astrophysics. Superconducting SIS mixers with niobium (Nb) tunnel junctions have reached a sensitivity close to the quantum limit, but have a frequency limit about 0.7 THz (i.e., gap frequency of Nb tunnel junctions). Beyond this frequency Nb superconducting films will absorb energetic photons (i.e., energy loss) to break Cooper pairs, thereby resulting in significant degradation of the mixer performance. Therefore, it is of particular interest to develop THz superconducting SIS mixers incorporating tunnel junctions with a larger energy gap. Niobium-nitride (NbN) superconducting tunnel junctions have been long known for their large energy gap, almost double that of Nb ones. With the introduction of epitaxially grown NbN films, the fabrication technology of NbN superconducting tunnel junctions has been considerably improved in the recent years. Nevertheless, their performances are still not as good as Nb ones, and furthermore they are not yet demonstrated in real astronomical applications. Given the facts mentioned above, in this paper we systematically study the quantum mixing behaviors of NbN superconducting tunnel junctions in the THz regime and demonstrate an astronomical testing observation with a 0.5 THz superconducting SIS mixer developed with NbN tunnel junctions. The main results of this study include: (1) successful design and fabrication of a 0.4˜0.6 THz waveguide mixing circuit with the high-dielectric-constant MgO substrate; (2) successful fabrication of NbN superconducting tunnel junctions with the gap voltage reaching 5.6 mV and the quality factor as high as 15; (3) demonstration of a 0.5 THz waveguide NbN superconducting SIS mixer with a measured receiver noise temperature (no correction) as low as five times the quantum limit

Superconductivity with twofold symmetry in Bi2Te3/FeTe0.55Se0.45 heterostructures

Science.gov (United States)

Du, Zengyi

2018-01-01

Topological superconductors are an interesting and frontier topic in condensed matter physics. In the superconducting state, an order parameter will be established with the basic or subsidiary symmetry of the crystalline lattice. In doped Bi2Se3 or Bi2Te3 with a basic threefold symmetry, it was predicted, however, that bulk superconductivity with order parameters of twofold symmetry may exist because of the presence of odd parity. We report the proximity effect–induced superconductivity in the Bi2Te3 thin film on top of the iron-based superconductor FeTe0.55Se0.45. By using the quasiparticle interference technique, we demonstrate clear evidence of twofold symmetry of the superconducting gap. The gap minimum is along one of the main crystalline axes following the so-called Δ4y notation. This is also accompanied by the elongated vortex shape mapped out by the density of states within the superconducting gap. Our results provide an easily accessible platform for investigating possible topological superconductivity in Bi2Te3/FeTe0.55Se0.45 heterostructures. PMID:29888330

Detection of bacterial endotoxin in food: New planar interdigital sensors based approach

KAUST Repository

Abdul Rahman, Mohd Syaifudin

2013-02-01

Food poisoning caused by endotoxins or Lipopolysaccharide (LPS) are associated with Gram-negative bacteria. Two major food-borne pathogens, Escherichia coli and Salmonella are examples of Gram-negative bacteria which cause a large number of outbreaks of food poisoning. New types of planar interdigital sensors have been fabricated with different coating materials to assess their response to endotoxins. A carboxyl-functional polymer, APTES (3-Aminopropyltriethoxysilane) and Thionine were chosen to be coated onto FR4 interdigital sensors. The chosen coating materials have carboxylic or amine functional groups, which were optimized to be stable in water. All coated sensors were immobilized with PmB (Polymyxin B) which has specific binding properties to LPS. The sensors were tested with different concentrations of LPS O111:B4, ranging from 0.1 to 1000 μg/ml. Analyses of sensors\\' performance were based on the impedance spectroscopy method. The impedance spectra were modeled using a constant phase-element (CPE) equivalent circuit, and a principal component analysis (PCA) was used for data classification. Sensor coated with APTES has shown better selectivity for LPS detection. The experiments were repeated by coating APTES and immobilizing PmB to a new improve designed of novel interdigital sensors (thin film silicon based sensors). These sensors were observed to have better sensitivity and selectivity to the target biomolecules of LPS. Further experiments were conducted to study the effect of different coating thickness on sensor sensitivity, selectivity and stability. Different food samples contaminated with endotoxin were also tested to verify that the interdigital sensing approach is able to be used for endotoxin detection. © 2012 Elsevier Ltd. All rights reserved.

Flow maldistribution in the anode of a polymer electrolyte membrane electrolysis cell employing interdigitated channels

DEFF Research Database (Denmark)

Olesen, Anders Christian; Kær, Søren Knudsen

2014-01-01

of liquid water towards the catalytic layer of the electrode. As opposed to the more common serpentine and parallel channels, interdigitated channels force liquid water through the porous gas diffusion layer (GDL) of the electrode. This improves the supply of water, however it increases pressure losses......-circular cell design on the distribution of water in the anode. In the electrolysis of water using PEMEC the anode is fed by demineralized water. Throughout the anode, oxygen is produced and a two-phase flow develops. Interdigitated channels assist in avoiding that gaseous oxygen obstructs the transport......: water stoichiometry, temperature, GDL permeability and thickness. In conclusion, it is found that the interdigitated flow field results in an uneven distribution across the cell and that the extent depends strongly on the permeability and weaker on the remaining parameters....

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)

Coexistence of Superconductivity and Ferromagnetism in ...

African Journals Online (AJOL)

KBHEEMA

Ferromagnetic alignment can be expected to be strongly opposed by superconductivity. .... To obtain temperature dependent of energy gap of equation (23), we used the same techniques to solve the integral .... band metal ZrZn2. Nature, 412: ...

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

Development of 50 MVA superconducting generator

International Nuclear Information System (INIS)

Ueda, Kiyotaka; Maki, Naoki; Takahashi, Noriyoshi; Ogata, Hisanao; Sanematsu, Toshihiro.

1984-01-01

Superconducting synchronous generators are expected to be the large capacity turbogenerators of next generation, but they have the structural features considerably different from conventional generators, such as low temperature multiple cylinder rotors and air gap armature winding. For the purpose of grasping the performance of superconducting generators and establishing the fundamental technology for their practical use, Hitachi Ltd. manufactured a 50 MVA superconducting generator. As the results of test, the precooling operation was smoothly finished for about 40 hours, and the superconducting rotor rotated stably at 3000 rpm. The steady and transient electrical characteristics were able to be grasped. It is intended to reflect these results to the development of a practical generator of 500 MVA class expected as the next step. When the superconducting exciting winding cooled by liquid helium is used, the reduction of weight, the improvement of efficiency and the improvement of the stability of power system can be expected. The structural features and the function of superconducting generators, the present state of the development in the world, the outline of the 50 MVA generator, the test results and the problems and the prospect hereafter are reported. The superconducting winding was made of NbTiZr alloy multicore wires. (Kako, I.)

A study of multi-phase flow through the cathode side of an interdigitated flow field using a multi-fluid model

DEFF Research Database (Denmark)

Berning, Torsten; Odgaard, Madeleine; Kær, Søren Knudsen

2010-01-01

This work presents a study of multi-phase flow through the cathode side of a polymer electrolyte membrane fuel cell employing an interdigitated flow field plate. A previously published model has been extended in order to account for phase change kinetics, and a comparison between the interdigitated...... flow field design and a conventional straight channel design has been conducted. It is found that the parasitic pressure drop in the interdigitated design is in the range of a few thousand Pa and could be reduced to a few hundred Pa by choosing diffusion media with high in-plane permeability....... In the interdigitated design more product water is carried out of the cell in the vapor phase compared to the straight channel design which indicates that liquid water management might be less problematic. This effect also leads to the finding that in the interdigitated design more waste heat is carried out of the cell...

Superconductivity and ferromagnetism in topological insulators

Science.gov (United States)

Zhang, Duming

Topological insulators, a new state of matter discovered recently, have attracted great interest due to their novel properties. They are insulating inside the bulk, but conducting at the surface or edges. This peculiar behavior is characterized by an insulating bulk energy gap and gapless surface or edge states, which originate from strong spin-orbit coupling and time-reversal symmetry. The spin and momentum locked surface states not only provide a model system to study fundamental physics, but can also lead to applications in spintronics and dissipationless electronics. While topological insulators are interesting by themselves, more exotic behaviors are predicted when an energy gap is induced at the surface. This dissertation explores two types of surface state gap in topological insulators, a superconducting gap induced by proximity effect and a magnetic gap induced by chemical doping. The first three chapters provide introductory theory and experimental details of my research. Chapter 1 provides a brief introduction to the theoretical background of topological insulators. Chapter 2 is dedicated to material synthesis principles and techniques. I will focus on two major synthesis methods: molecular beam epitaxy for the growth of Bi2Se3 thin films and chemical vapor deposition for the growth of Bi2Se3 nanoribbons and nanowires. Material characterization is discussed in Chapter 3. I will describe structural, morphological, magnetic, electrical, and electronic characterization techniques used to study topological insulators. Chapter 4 discusses the experiments on proximity-induced superconductivity in topological insulator (Bi2Se3) nanoribbons. This work is motivated by the search for the elusive Majorana fermions, which act as their own antiparticles. They were proposed by Ettore Majorara in 1937, but have remained undiscovered. Recently, Majorana's concept has been revived in condensed matter physics: a condensed matter analog of Majorana fermions is predicted to

The Zeeman-split superconductivity with Rashba and Dresselhaus spin-orbit coupling

Science.gov (United States)

Zhao, Jingxiang; Yan, Xu; Gu, Qiang

2017-10-01

The superconductivity with Rashba and Dressehlaus spin-orbit coupling and Zeeman effect is investigated. The energy gaps of quasi-particles are carefully calculated. It is shown that the coexistence of two spin-orbit coupling might suppress superconductivity. Moreover, the Zeeman effect favors spin-triplet Cooper pairs.

Scanning tunneling spectroscopy of Co adsorbates on superconducting Pb nanostructures

Energy Technology Data Exchange (ETDEWEB)

Decker, Regis; Caminale, Michael; Oka, Hirofumi; Stepniak, Agnieszka; Leon Vanegas, Augusto A.; Sander, Dirk; Kirschner, Juergen [Max-Planck-Institut fuer Mikrostrukturphysik, Weinberg 2, 06120 Halle (Germany)

2015-07-01

Superconductivity in low-dimensional structures has become an active research area. In order to understand the superconducting pairing, long-standing work has been devoted to the pair breaking effect, where magnetic impurities break Cooper pair singlets. We performed scanning tunneling spectroscopy at low temperature on Co adsorbates on superconducting Pb nanoislands. On the Co adsorbates, we observe spectral features in the superconductor's energy gap, which we attribute to magnetic impurity induced bound states, a hallmark of the pair breaking effect. We discuss the response of the superconducting islands to the presence of Co adsorbates.

Enhancement of magnetic flux distribution in a DC superconducting electric motor

International Nuclear Information System (INIS)

Hamid, N A; Ewe, L S; Chin, K M

2013-01-01

Most motor designs require an air gap between the rotor and stator to enable the armature to rotate freely. The interaction of magnetic flux from rotor and stator within the air gap will provide the thrust for rotational motion. Thus, the understanding of magnetic flux in the vicinity of the air gap is very important to mathematically calculate the magnetic flux generated in the area. In this work, a finite element analysis was employed to study the behavior of the magnetic flux in view of designing a synchronous DC superconducting electric motor. The analysis provides an ideal magnetic flux distribution within the components of the motor. From the flux plot analysis, it indicates that flux losses are mainly in the forms of leakage and fringe effect. The analysis also shows that the flux density is high at the area around the air gap and the rotor. The high flux density will provide a high force area that enables the rotor to rotate. In contrast, the other parts of the motor body do not show high flux density indicating low distribution of flux. Consequently, a bench top model of a DC superconducting motor was developed where by motor with a 2-pole type winding was chosen. Each field coil was designed with a racetrack-shaped double pancake wound using DI-BSCCO Bi-2223 superconducting tapes. The performance and energy efficiency of the superconducting motor was superior when compared to the conventional motor with similar capacity.

Magnetic-field and temperature dependence of the energy gap in InN nanobelt

Directory of Open Access Journals (Sweden)

K. Aravind

2012-03-01

Full Text Available We present tunneling measurements on an InN nanobelt which shows signatures of superconductivity. Superconducting transition takes place at temperature of 1.3K and the critical magnetic field is measured to be about 5.5kGs. The energy gap extrapolated to absolute temperature is about 110μeV. As the magnetic field is decreased to cross the critical magnetic field, the device shows a huge zero-bias magnetoresistance ratio of about 400%. This is attributed to the suppression of quasiparticle subgap tunneling in the presence of superconductivity. The measured magnetic-field and temperature dependence of the superconducting gap agree well with the reported dependences for conventional metallic superconductors.

Large superconducting wind turbine generators

DEFF Research Database (Denmark)

Abrahamsen, Asger Bech; Magnusson, Niklas; Jensen, Bogi Bech

2012-01-01

and the rotation speed is lowered in order to limit the tip speed of the blades. The ability of superconducting materials to carry high current densities with very small losses might facilitate a new class of generators operating with an air gap flux density considerably higher than conventional generators...... and thereby having a smaller size and weight [1, 2]. A 5 MW superconducting wind turbine generator forms the basics for the feasibility considerations, particularly for the YBCO and MgB2 superconductors entering the commercial market. Initial results indicate that a 5 MW generator with an active weight of 34...

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.

Ac loss measurements on a superconducting transformer for a 25 kA superconducting rectifier

NARCIS (Netherlands)

ten Kate, Herman H.J.; Mulders, J.M.; de Reuver, J.L.; van de Klundert, L.J.M.

1984-01-01

Ac loss measurements have been performed on a superconducting transformer. The transformer is a part of a 25 kA thermally switched superconducting rectifier operating at a frequency of 0.1 Hz. The loss measurements have been automatized by means of a microcomputer sampling four relevant signals and

Sensing with Superconducting Point Contacts

Directory of Open Access Journals (Sweden)

Argo Nurbawono

2012-05-01

Full Text Available Superconducting point contacts have been used for measuring magnetic polarizations, identifying magnetic impurities, electronic structures, and even the vibrational modes of small molecules. Due to intrinsically small energy scale in the subgap structures of the supercurrent determined by the size of the superconducting energy gap, superconductors provide ultrahigh sensitivities for high resolution spectroscopies. The so-called Andreev reflection process between normal metal and superconductor carries complex and rich information which can be utilized as powerful sensor when fully exploited. In this review, we would discuss recent experimental and theoretical developments in the supercurrent transport through superconducting point contacts and their relevance to sensing applications, and we would highlight their current issues and potentials. A true utilization of the method based on Andreev reflection analysis opens up possibilities for a new class of ultrasensitive sensors.

Suppressing band gap of MoS{sub 2} by the incorporation of four- and eight-membered rings

Energy Technology Data Exchange (ETDEWEB)

Zhu, Liyan; Zhang, Tingting, E-mail: ttzhang@hytc.edu.cn [Huaiyin Normal University, School of Physics and Electronic & Electrical Engineering, and Jiangsu Key Laboratory of Modern Measurement Technology and Intelligent Systems (China)

2015-05-15

A stable planar allotrope of MoS{sub 2}, formed by introducing four- and eight-membered rings into its hexagonal network (H468), is identified to be a narrow direct-band-gap semiconductor by first principle calculations, which is remarkably different from the large band gap semiconductor of conventional MoS{sub 2} and also the zero band gap allotrope consisting of four- and eight-membered rings (H48) only. The medium-sized direct band gap indicates that H468 would find applications in nanoelectronics and near-infrared optoelectronic devices. Furthermore, the distinctive simulated scanning tunneling microscope images under positive and negative biases might be a unique characteristic for the experimental identification of such an allotrope of MoS{sub 2}.

ESR spectrometer with a loop-gap resonator for cw and time resolved studies in a superconducting magnet.

Science.gov (United States)

Simon, Ferenc; Murányi, Ferenc

2005-04-01

The design and performance of an electron spin resonance spectrometer operating at 3 and 9 GHz microwave frequencies combined with a 9-T superconducting magnet are described. The probehead contains a compact two-loop, one gap resonator, and is inside the variable temperature insert of the magnet enabling measurements in the 0-9T magnetic field and 1.5-400 K temperature range. The spectrometer allows studies on systems where resonance occurs at fields far above the g approximately 2 paramagnetic condition such as in antiferromagnets. The low quality factor of the resonator allows time resolved experiments such as, e.g., longitudinally detected ESR. We demonstrate the performance of the spectrometer on the NaNiO2 antiferromagnet, the MgB2 superconductor, and the RbC60 conducting alkaline fulleride polymer.

Maskless fabrication of a microfluidic device with interdigitated electrodes on PCB using laser ablation

Science.gov (United States)

Contreras-Saenz, Michael; Hassard, Christian; Vargas-Chacon, Rafael; Gordillo, Jose Luis; Camacho-Leon, Sergio

2016-03-01

This paper reports the maskless fabrication of a microfluidic device with interdigitated electrodes (IDE) based on the technology of MicroElectroMechanical Systems on Printed Circuit Board (PCB-MEMS) and laser ablation. The device has flame retardant (FR)-4 resin as substrate, cooper (Cu) as active material and SU-8 polymer as structural material. By adjusting the laser parameters, Cu IDEs and SU-8 microchannels were successfully patterned onto the FR-4 substrate. The respective width, gap and overlap of the IDEs were 50 μm, 25 μm and 500 μm. The respective width, depth and length of the microchannels were 210 μm, 24.6 μm and 6.3 mm. The resolution and repeatability achieved in this approach, along with the low cost of the involved materials and techniques, enable an affordable micromachining platform with rapid fabrication-test cycle to develop active multiphysic microdevices with several applications in the fields of biosensing, cell culture, drug delivery, transport and sorting of molecules, among others.

Superconducting β-ZrNClx probed by scanning-tunnelling and break-junction spectroscopy

International Nuclear Information System (INIS)

Ekino, Toshikazu; Sugimoto, Akira; Gabovich, Alexander M.; Zheng, Zhanfeng; Yamanaka, Shoji

2013-01-01

Highlights: •STM/STS combined with break-junction tunnelling spectroscopy (BJTS) on β-ZrNCl. •STM image on the ab plane shows triangular atomic lattice spots with a period of 0.36 nm. •The gap peaks are widely distributed (Δ p–p = 9–28 meV)over the area of 100 nm 2 . •Average gap ratio 2Δ/k B T c ∼ 10 is confirmed by both STS and BJTS. -- Abstract: Superconducting layered compound β-ZrNCl x (x = 0.7) with the critical temperature T c = 13–14 K was investigated by means of scanning tunnelling microscopy/spectroscopy. The single-crystal domain facet of ∼100 μm 2 in the c-axis-oriented polycrystal was used as a probing surface. The STM image at 4.9 K shows triangular atomic lattice spots with the period of ∼0.36 nm, which agrees with the X-ray diffraction measurements. The STS measurements of the local conductance, dI/dV, exhibit broadened gap structures with a substantial distribution of the gap-edge values. Most frequently observed peak-to-peak value of ∼20 mV is remarkably similar to the superconducting gap edge of the isostructural β-HfNCl x with T c = 24 K. Temperature, T, dependence of the dI/dV shows that the gap structure disappears above T c ∼ 13 K. Fitting of the dI/dV curve by the broadened BCS density of states leads to the superconducting gap of 2Δ(4.9 K) = 11–13 meV. This is in accordance with our former break-junction data confirming the intrinsic character of the previously obtained extremely large gap to T c ratio 2Δ(0)/k B T c ≈ 10 (k B is the Boltzmann constant), thereby pointing to the unusual superconducting properties of this compound

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.

Superconducting magnet for a Ku-band maser.

Science.gov (United States)

Berwin, R.; Wiebe, E.; Dachel, P.

1972-01-01

A superconducting magnet to provide a uniform magnetic field of up to 8000 G in a 1.14-cm gap for the 15.3-GHz (Ku-band) traveling wave maser is described. The magnet operates in a persistent mode in the vacuum environment of a closed-cycle helium refrigerator (4.5 K). The features of a superconducting switch, which has both leads connected to 4.5 K heat stations and thereby does not receive heat generated by the magnet charging leads, are described.

Scientific Affairs Division of NATO Advanced Study Institute: abstracts for nonequilibrium superconductivity, phonons and Kapitza boundaries

International Nuclear Information System (INIS)

1980-05-01

Abstracts of papers presented at the meeting are given. Topics covered include: Kapitza resistance; superconducting tunneling; energy gap enhancement in superconductors; instabilities in nonequilibrium superconducting states; exchange of charge between superconducting pairs and quasiparticles; motion of magnetic flux (flux flow); and other new phenomena

Measuring ac-loss in high temperature superconducting cable-conductors using four probe methods

DEFF Research Database (Denmark)

Kühle (fratrådt), Anders Van Der Aa; Træholt, Chresten; Olsen, Søren Krüger

1999-01-01

Measuring the ac-loss of superconducting cable conductors have many aspects in common with measuring the ac-loss of single superconducting tapes. In a cable conductor all tapes are connected to each other and to the test circuit through normal metal joints in each end. This makes such measurement...

μSR and NMR study of the superconducting Heusler compound YPd2Sn

Science.gov (United States)

Saadaoui, H.; Shiroka, T.; Amato, A.; Baines, C.; Luetkens, H.; Pomjakushina, E.; Pomjakushin, V.; Mesot, J.; Pikulski, M.; Morenzoni, E.

2013-09-01

We report on muon-spin rotation and relaxation (μSR) and 119Sn nuclear magnetic resonance (NMR) measurements to study the microscopic superconducting and magnetic properties of the Heusler compound with the highest superconducting transition temperature, YPd2Sn (Tc=5.4 K). Measurements in the vortex state provide the temperature dependence of the effective magnetic penetration depth λ(T) and the field dependence of the superconducting gap Δ(0). The results are consistent with a very dirty s-wave BCS superconductor with a gap Δ(0)=0.85(3) meV, λ(0)=212(1) nm, and a Ginzburg-Landau coherence length ξGL(0)≅23 nm. In spite of its very dirty character, the effective density of condensed charge carriers is high compared to that in the normal state. The μSR data in a broad range of applied fields are well reproduced by taking into account a field-related reduction of the effective superconducting gap. Zero-field μSR measurements, sensitive to the possible presence of very small magnetic moments, do not show any indications of magnetism in this compound.

The role of engineered materials in superconducting tunnel junction X-ray detectors - Suppression of quasiparticle recombination losses via a phononic band gap

Science.gov (United States)

Rippert, Edward D.; Ketterson, John B.; Chen, Jun; Song, Shenian; Lomatch, Susanne; Maglic, Stevan R.; Thomas, Christopher; Cheida, M. A.; Ulmer, Melville P.

1992-01-01

An engineered structure is proposed that can alleviate quasi-particle recombination losses via the existence of a phononic band gap that overlaps the 2-Delta energy of phonons produced during recombination of quasi-particles. Attention is given to a 1D Kronig-Penny model for phonons normally incident to the layers of a multilayered superconducting tunnel junction as an idealized example. A device with a high density of Bragg resonances is identified as desirable; both Nb/Si and NbN/SiN superlattices have been produced, with the latter having generally superior performance.

Prediction of superconductivity in Li-intercalated bilayer phosphorene

International Nuclear Information System (INIS)

Huang, G. Q.; Xing, Z. W.; Xing, D. Y.

2015-01-01

It is shown that bilayer phosphorene can be transformed from a direct-gap semiconductor to a BCS superconductor by intercalating Li atoms. For the Li-intercalated bilayer phosphorene, we find that the electron occupation of Li-derived band is small and superconductivity is intrinsic. With increasing the intercalation of Li atoms, both increased metallicity and strong electron-phonon coupling are favorable for the enhancement of superconductivity. The obtained electron-phonon coupling λ can be larger than 1 and the superconducting temperature T c can be increased up to 16.5 K, suggesting that phosphorene may be a good candidate for a nanoscale superconductor

Prediction of superconductivity in Li-intercalated bilayer phosphorene

Energy Technology Data Exchange (ETDEWEB)

Huang, G. Q. [Department of Physics, Nanjing Normal University, Nanjing 210023 (China); National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093 (China); Xing, Z. W., E-mail: zwxing@nju.edu.cn [National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093 (China); Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Xing, D. Y. [National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093 (China); Collaborative Innovation Center of Advanced Microstructures and Department of Physics, Nanjing University, Nanjing 210093 (China)

2015-03-16

It is shown that bilayer phosphorene can be transformed from a direct-gap semiconductor to a BCS superconductor by intercalating Li atoms. For the Li-intercalated bilayer phosphorene, we find that the electron occupation of Li-derived band is small and superconductivity is intrinsic. With increasing the intercalation of Li atoms, both increased metallicity and strong electron-phonon coupling are favorable for the enhancement of superconductivity. The obtained electron-phonon coupling λ can be larger than 1 and the superconducting temperature T{sub c} can be increased up to 16.5 K, suggesting that phosphorene may be a good candidate for a nanoscale superconductor.

Characterization of double-loop four-Josephson-junction flux qubit

International Nuclear Information System (INIS)

Shimazu, Y.; Saito, Y.; Wada, Z.

2009-01-01

An advantage of a double-loop four-Josephson-junction (4-JJ) flux qubit is the tunability of the energy gap at a symmetry point, i.e., the point at which the double-well potential of the qubit is symmetric. The energy gap is controlled via the magnetic flux in a DC superconducting quantum interference device (DC-SQUID) loop incorporated in a 4-JJ qubit. We investigate the locus of the symmetry point in the plane of two control fluxes of the qubit, taking into account the asymmetry in the DC-SQUID, which is inevitable in practical cases. The observed positions of the qubit steps are in reasonable agreement with the calculated locus of the symmetry point. We estimate the asymmetry parameter of the DC-SQUID from this analysis.

Higgsless superconductivity from topological defects in compact BF terms

Directory of Open Access Journals (Sweden)

M. Cristina Diamantini

2015-02-01

Full Text Available We present a new Higgsless model of superconductivity, inspired from anyon superconductivity but P- and T-invariant and generalisable to any dimension. While the original anyon superconductivity mechanism was based on incompressible quantum Hall fluids as average field states, our mechanism involves topological insulators as average field states. In D space dimensions it involves a (D−1-form fictitious pseudovector gauge field which originates from the condensation of topological defects in compact low-energy effective BF theories. In the average field approximation, the corresponding uniform emergent charge creates a gap for the (D−2-dimensional branes via the Magnus force, the dual of the Lorentz force. One particular combination of intrinsic and emergent charge fluctuations that leaves the total charge distribution invariant constitutes an isolated gapless mode leading to superfluidity. The remaining massive modes organise themselves into a D-dimensional charged, massive vector. There is no massive Higgs scalar as there is no local order parameter. When electromagnetism is switched on, the photon acquires mass by the topological BF mechanism. Although the charge of the gapless mode (2 and the topological order (4 are the same as those of the standard Higgs model, the two models of superconductivity are clearly different since the origins of the gap, reflected in the high-energy sectors are totally different. In 2D this type of superconductivity is explicitly realised as global superconductivity in Josephson junction arrays. In 3D this model predicts a possible phase transition from topological insulators to Higgsless superconductors.

Unconventional superconductivity near inhomogeneities

International Nuclear Information System (INIS)

Poenicke, A.F.

2008-01-01

After the presentation of a quasi-classical theory the specific heat of Sr 2 RuO 4 is considered. Then tunneling spectroscopy on cuprate superconductors is discussed. Thereafter the subharmonic gap structure in d-wave superconductors is considered. Finally the application of the S-matrix in superconductivity is discussed with spin mixing, CrO 2 as example, and an interface model. (HSI)

Substrate-enhanced superconductivity in Li-decorated graphene

KAUST Repository

Kaloni, Thaneshwor P.

2013-11-01

We investigate the role of the substrate for the strength of the electron-phonon coupling in Li-decorated graphene. We find that the interaction with a h-BN substrate leads to a significant enhancement from to , which corresponds to a 25% increase of the transition temperature from to . The superconducting gaps amount to 1.56 meV (suspended) and 1.98 meV (supported). These findings open up a new route to enhanced superconducting transition temperatures in graphene-based materials by substrate engineering. © 2013 EPLA.

Superconducting tin core fiber

International Nuclear Information System (INIS)

Homa, Daniel; Liang, Yongxuan; Hill, Cary; Kaur, Gurbinder; Pickrell, Gary

2015-01-01

In this study, we demonstrated superconductivity in a fiber with a tin core and fused silica cladding. The fibers were fabricated via a modified melt-draw technique and maintained core diameters ranging from 50-300 microns and overall diameters of 125-800 microns. Superconductivity of this fiber design was validated via the traditional four-probe test method in a bath of liquid helium at temperatures on the order of 3.8 K. The synthesis route and fiber design are perquisites to ongoing research dedicated all-fiber optoelectronics and the relationships between superconductivity and the material structures, as well as corresponding fabrication techniques. (orig.)

ESCAR superconducting magnet system

International Nuclear Information System (INIS)

Gilbert, W.S.; Meuser, R.B.; Pope, W.L.; Green, M.A.

1975-01-01

Twenty-four superconducting dipoles, each about 1 meter long, provide the guide field for the Experimental Superconducting Accelerator Ring proton accelerator--storage ring. Injection of 50 MeV protons corresponds to a 3 kG central dipole field, and a peak proton energy of 4.2 GeV corresponds to a 46 kG central field. Thirty-two quadrupoles provide focusing. The 56 superconducting magnets are contained in 40 cryostats that are cryogenically connected in a novel series ''weir'' arrangement. A single 1500 W refrigeration plant is required. Design and testing of the magnet and cryostat system are described. (U.S.)

Raman scattering and luminescence of high-Tc superconducting oxides

International Nuclear Information System (INIS)

Eremenko, V.V.; Gnezdilov, V.P.; Fomin, V.I.; Fugol', I.Ya.; Samovarov, V.N.

1989-01-01

Raman and luminescence spectra of high-T c superconducting oxides are summarized, mainly YBa 2 Cu 3 O 7-σ and partly La 2-x Ba x CuO 4-σ . In raman spectra we succeeded to distinguish electron scattering to define the energy gap Δ in the superconducting state. The luminescence spectra are due to the emission of oxygen and interaction with conduction electrons. 70 refs.; 13 figs

Superconducting quantum circuits theory and application

OpenAIRE

Deng, Xiuhao

2015-01-01

Superconducting quantum circuit models are widely used to understand superconducting devices. This thesis consists of four studies wherein the superconducting quantum circuit is used to illustrate challenges related to quantum information encoding and processing, quantum simulation, quantum signal detection and amplification.The existence of scalar Aharanov-Bohm phase has been a controversial topic for decades. Scalar AB phase, defined as time integral of electric potential, gives rises to a...

Interdigitated microelectrode based impedance biosensor for detection of salmonella enteritidis in food samples

International Nuclear Information System (INIS)

Kim, G; Morgan, M; Hahm, B K; Bhunia, A; Mun, J H; Om, A S

2008-01-01

Salmonella enteritidis outbreaks continue to occur, and S. enteritidis-related outbreaks from various food sources have increased public awareness of this pathogen. Conventional methods for pathogens detection and identification are labor-intensive and take days to complete. Some immunological rapid assays are developed, but these assays still require prolonged enrichment steps. Recently developed biosensors have shown great potential for the rapid detection of foodborne pathogens. To develop the biosensor, an interdigitated microelectrode (IME) was fabricated by using semiconductor fabrication process. Anti-Salmonella antibodies were immobilized based on avidin-biotin binding on the surface of the IME to form an active sensing layer. To increase the sensitivity of the sensor, three types of sensors that have different electrode gap sizes (2 μm, 5 μm, 10 μm) were fabricated and tested. The impedimetric biosensor could detect 10 3 CFU/mL of Salmonella in pork meat extract with an incubation time of 5 minutes. This method may provide a simple, rapid and sensitive method to detect foodborne pathogens

Interdigitated microelectrode based impedance biosensor for detection of salmonella enteritidis in food samples

Energy Technology Data Exchange (ETDEWEB)

Kim, G [National Institute of Agricultural Engineering, 249 Seodun-dong, Suwon, Republic of Korea, 441-100 (Korea, Republic of); Morgan, M; Hahm, B K; Bhunia, A [Department of Food Science, Purdue University, West Lafayette, IN 47907 (United States); Mun, J H; Om, A S [Department of Food and Nutrient, Hanyang University, 17 Haengdang-dong, Seoul, Republic of Korea, 133-791 (Korea, Republic of)], E-mail: giyoungkim@rda.go.kr

2008-03-15

Salmonella enteritidis outbreaks continue to occur, and S. enteritidis-related outbreaks from various food sources have increased public awareness of this pathogen. Conventional methods for pathogens detection and identification are labor-intensive and take days to complete. Some immunological rapid assays are developed, but these assays still require prolonged enrichment steps. Recently developed biosensors have shown great potential for the rapid detection of foodborne pathogens. To develop the biosensor, an interdigitated microelectrode (IME) was fabricated by using semiconductor fabrication process. Anti-Salmonella antibodies were immobilized based on avidin-biotin binding on the surface of the IME to form an active sensing layer. To increase the sensitivity of the sensor, three types of sensors that have different electrode gap sizes (2 {mu}m, 5 {mu}m, 10 {mu}m) were fabricated and tested. The impedimetric biosensor could detect 10{sup 3} CFU/mL of Salmonella in pork meat extract with an incubation time of 5 minutes. This method may provide a simple, rapid and sensitive method to detect foodborne pathogens.

Laser-excited photoemission spectroscopy study of superconducting boron-doped diamond

Directory of Open Access Journals (Sweden)

K. Ishizaka, R. Eguchi, S. Tsuda, T. Kiss, T. Shimojima, T. Yokoya, S. Shin, T. Togashi, S. Watanabe, C.-T. Chen, C.Q. Zhang, Y. Takano, M. Nagao, I. Sakaguchi, T. Takenouchi and H. Kawarada

2006-01-01

Full Text Available We have investigated the low-energy electronic state of boron-doped diamond thin film by the laser-excited photoemission spectroscopy. A clear Fermi-edge is observed for samples doped above the semiconductor–metal boundary, together with the characteristic structures at 150×n meV possibly due to the strong electron–lattice coupling effect. In addition, for the superconducting sample, we observed a shift of the leading edge below Tc indicative of a superconducting gap opening. We discuss the electron–lattice coupling and the superconductivity in doped diamond.

Four-layer, two-inch bore, superconducting dipole magnet

International Nuclear Information System (INIS)

Hassenzahl, W.V.; Peters, C.; Gilbert, W.; Taylor, C.; Meuser, R.

1982-11-01

Superconductors provide the accelerator designer with a unique opportunity to construct machines that can achieve high particle energies and yet have low operating costs. This paper describes the design, fabrication and testing of a 4 layer, 50 mm bore superconducting dipole magnet, D-9A. The magnet reached short sample, 5.8 T at 4.4 K and 8.0 T and 1.8 K, with little training, and exhibited low losses and low ramp rate sensitivity

Three-flavor color superconductivity

Energy Technology Data Exchange (ETDEWEB)

Malekzadeh, H.

2007-12-15

I investigate some of the inert phases in three-flavor, spin-zero color-superconducting quark matter: the CFL phase (the analogue of the B phase in superfluid {sup 3}He), the A and A{sup *} phases, and the 2SC and sSC phases. I compute the pressure of these phases with and without the neutrality condition. Without the neutrality condition, after the CFL phase the sSC phase is the dominant phase. However, including the neutrality condition, the CFL phase is again the energetically favored phase except for a small region of intermediate densities where the 2SC/A{sup *} phase is favored. It is shown that the 2SC phase is identical to the A{sup *} phase up to a color rotation. In addition, I calculate the self-energies and the spectral densities of longitudinal and transverse gluons at zero temperature in color-superconducting quark matter in the CFL phase. I find a collective excitation, a plasmon, at energies smaller than two times the gap parameter and momenta smaller than about eight times the gap. The dispersion relation of this mode exhibits a minimum at some nonzero value of momentum, indicating a van Hove singularity. (orig.)

Three-flavor color superconductivity

International Nuclear Information System (INIS)

Malekzadeh, H.

2007-12-01

I investigate some of the inert phases in three-flavor, spin-zero color-superconducting quark matter: the CFL phase (the analogue of the B phase in superfluid 3 He), the A and A * phases, and the 2SC and sSC phases. I compute the pressure of these phases with and without the neutrality condition. Without the neutrality condition, after the CFL phase the sSC phase is the dominant phase. However, including the neutrality condition, the CFL phase is again the energetically favored phase except for a small region of intermediate densities where the 2SC/A * phase is favored. It is shown that the 2SC phase is identical to the A * phase up to a color rotation. In addition, I calculate the self-energies and the spectral densities of longitudinal and transverse gluons at zero temperature in color-superconducting quark matter in the CFL phase. I find a collective excitation, a plasmon, at energies smaller than two times the gap parameter and momenta smaller than about eight times the gap. The dispersion relation of this mode exhibits a minimum at some nonzero value of momentum, indicating a van Hove singularity. (orig.)

Anomalous enhancement of the lower critical field deep in the superconducting state of LaRu4As12

Science.gov (United States)

Juraszek, J.; Bochenek, Ł.; Wawryk, R.; Henkie, Z.; Konczykowski, M.; Cichorek, T.

2018-05-01

LaRu4As12 with the critical temperature Tc = 10.4 K displays several features which point at a non-singlet superconducting order parameter, although the bcc crystal structure of the filled skutterudites does not favour the emergence of multiple energy gaps. LaRu4As12 displays an unexpected enhancement of the lower critical field deep in superconducting state which can be attributed to the existence of two superconducting gaps. At T = 0.4 K, the local magnetization measurements were performed utilizing miniaturized Hall sensors.

The g-2 storage ring superconducting magnet system

International Nuclear Information System (INIS)

Green, M.A.

1993-09-01

The g-2 μ lepton (muon) storage ring is a single dipole magnet that is 44 meters in circumference. The storage ring dipole field is created by three large superconducting solenoid coils. A single outer solenoid, 15.1 meters in diameter, carries 254 kA. Two inner solenoids, 13.4 meters in diameter, carry 127 kA each in opposition to the current carried by the outer solenoid. A room temperature C shaped iron yoke returns the magnetic flux and shapes the magnetic field in a 180 mm gap where the stored muon beam circulates. The gap induction will be 1.47 T. This report describes the three large superconducting solenoids, the cryogenic system needed to keep them cold, the solenoid power supply and the magnet quench protection system

The dosimetric impact of leaf interdigitation and leaf width on VMAT treatment planning in Pinnacle: comparing Pareto fronts

International Nuclear Information System (INIS)

Van Kesteren, Z; Janssen, T M; Damen, E; Van Vliet-Vroegindeweij, C

2012-01-01

To evaluate in an objective way the effect of leaf interdigitation and leaf width on volumetric modulated arc therapy plans in Pinnacle. Three multileaf collimators (MLCs) were modeled: two 10 mm leaf width MLCs, with and without interdigitating leafs, and a 5 mm leaf width MLC with interdigitating leafs. Three rectum patients and three prostate patients were used for the planning study. In order to compare treatment techniques in an objective way, a Pareto front comparison was carried out. 200 plans were generated in an automated way, per patient per MLC model, resulting in a total of 3600 plans. From these plans, Pareto-optimal plans were selected which were evaluated for various dosimetric variables. The capability of leaf interdigitation showed little dosimetric impact on the treatment plans, when comparing the 10 mm leaf width MLC with and without leaf interdigitation. When comparing the 10 mm leaf width MLC with the 5 mm leaf width MLC, both with interdigitating leafs, improvement in plan quality was observed. For both patient groups, the integral dose was reduced by 0.6 J for the thin MLC. For the prostate patients, the mean dose to the anal sphincter was reduced by 1.8 Gy and the conformity of the V 95% was reduced by 0.02 using the thin MLC. The V 65% of the rectum was reduced by 0.1% and the dose homogeneity with 1.5%. For rectum patients, the mean dose to the bowel was reduced by 1.4 Gy and the mean dose to the bladder with 0.8 Gy for the thin MLC. The conformity of the V 95% was equivalent for the 10 and 5 mm leaf width MLCs for the rectum patients. We have objectively compared three types of MLCs in a planning study for prostate and rectum patients by analyzing Pareto-optimal plans which were generated in an automated way. Interdigitation of MLC leafs does not generate better plans using the SmartArc algorithm in Pinnacle. Changing the MLC leaf width from 10 to 5 mm generates better treatment plans although the clinical relevance remains to be proven

The dosimetric impact of leaf interdigitation and leaf width on VMAT treatment planning in Pinnacle: comparing Pareto fronts.

Science.gov (United States)

van Kesteren, Z; Janssen, T M; Damen, E; van Vliet-Vroegindeweij, C

2012-05-21

To evaluate in an objective way the effect of leaf interdigitation and leaf width on volumetric modulated arc therapy plans in Pinnacle. Three multileaf collimators (MLCs) were modeled: two 10 mm leaf width MLCs, with and without interdigitating leafs, and a 5 mm leaf width MLC with interdigitating leafs. Three rectum patients and three prostate patients were used for the planning study. In order to compare treatment techniques in an objective way, a Pareto front comparison was carried out. 200 plans were generated in an automated way, per patient per MLC model, resulting in a total of 3600 plans. From these plans, Pareto-optimal plans were selected which were evaluated for various dosimetric variables. The capability of leaf interdigitation showed little dosimetric impact on the treatment plans, when comparing the 10 mm leaf width MLC with and without leaf interdigitation. When comparing the 10 mm leaf width MLC with the 5 mm leaf width MLC, both with interdigitating leafs, improvement in plan quality was observed. For both patient groups, the integral dose was reduced by 0.6 J for the thin MLC. For the prostate patients, the mean dose to the anal sphincter was reduced by 1.8 Gy and the conformity of the V(95%) was reduced by 0.02 using the thin MLC. The V(65%) of the rectum was reduced by 0.1% and the dose homogeneity with 1.5%. For rectum patients, the mean dose to the bowel was reduced by 1.4 Gy and the mean dose to the bladder with 0.8 Gy for the thin MLC. The conformity of the V(95%) was equivalent for the 10 and 5 mm leaf width MLCs for the rectum patients. We have objectively compared three types of MLCs in a planning study for prostate and rectum patients by analyzing Pareto-optimal plans which were generated in an automated way. Interdigitation of MLC leafs does not generate better plans using the SmartArc algorithm in Pinnacle. Changing the MLC leaf width from 10 to 5 mm generates better treatment plans although the clinical relevance remains

Unconventional superconductivity near inhomogeneities

Energy Technology Data Exchange (ETDEWEB)

Poenicke, A F

2008-01-25

After the presentation of a quasi-classical theory the specific heat of Sr{sub 2}RuO{sub 4} is considered. Then tunneling spectroscopy on cuprate superconductors is discussed. Thereafter the subharmonic gap structure in d-wave superconductors is considered. Finally the application of the S-matrix in superconductivity is discussed with spin mixing, CrO{sub 2} as example, and an interface model. (HSI)

Low-charge-state linac

Energy Technology Data Exchange (ETDEWEB)

Shepard, K.W.; Kim, J.W.

1995-08-01

A design is being developed for a low-charge-state linac suitable for injecting ATLAS with a low-charge-state, radioactive beam. Initial work indicates that the existing ATLAS interdigital superconducting accelerating structures, together with the superconducting quadrupole transverse focussing element discussed above, provides a basis for a high-performance low-charge-state linac. The initial 2 or 3 MV of such a linac could be based on a normally-conducting, low-frequency RFQ, possibly combined with 24-MHz superconducting interdigital structures. Beam dynamics studies of the whole low-charge-state post-accelerator section were carried out in early FY 1995.

Recent Progress in Micro-Supercapacitors with In-Plane Interdigital Electrode Architecture.

Science.gov (United States)

Liu, Nishuang; Gao, Yihua

2017-12-01

Due to the boom of miniaturized electronic devices in the last decade, there are great demands for ultrathin and flexible on-chip rechargeable energy storage microdevices. Supercapacitor, as one of the most hopeful appearing energy storage devices, can provide a wonderful alternative to batteries or electrolytic capacitors, owing to its fast charge and discharge rates, high power density, and long cycling stability. Especially for the recently developed micro-supercapacitors, the unique in-plane interdigital electrode architecture can fully meet the integration requirements of rapidly developed miniaturized electronic devices, and improve the power density of the unit via shortening the ionic diffusion distance between the interdigital electrodes. This concept introduces the recent advances on the design, fabrication, and application of planar micro-supercapacitors for on-chip energy storage from an overall perspective. Moreover, challenges and future development trends are discussed. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

Observation of Momentum-Confined In-Gap Impurity State in Ba_{0.6}K_{0.4}Fe_{2}As_{2}: Evidence for Antiphase s_{±} Pairing

Directory of Open Access Journals (Sweden)

P. Zhang

2014-07-01

Full Text Available We report the observation by angle-resolved photoemission spectroscopy of an impurity state located inside the superconducting gap of Ba_{0.6}K_{0.4}Fe_{2}As_{2} and vanishing above the superconducting critical temperature, for which the spectral weight is confined in momentum space near the Fermi wave-vector positions. We demonstrate, supported by theoretical simulations, that this in-gap state originates from weak scattering between bands with opposite sign of the superconducting-gap phase. This weak scattering, likely due to off-plane nonmagnetic (Ba, K disorder, occurs mostly among neighboring Fermi surfaces, suggesting that the superconducting-gap phase changes sign within holelike (and electronlike bands. Our results impose severe restrictions on the models promoted to explain high-temperature superconductivity in these materials.

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

Superconducting Technology Program: Sandia 1993 annual report

International Nuclear Information System (INIS)

Roth, E.P.

1994-05-01

Sandia's STP program is a four-part high-temperature superconductor (HTS) research and development program consisting of efforts in powder synthesis and process development, thallium-based HTS film development, wire and tape fabrication, and HTS motor design. The objective of this work is to develop high-temperature superconducting conductors (wire and tape) capable of meeting requirements for high-power electrical devices of interest to industry. The four research efforts currently underway are: (1) process research on the material synthesis of high-temperature superconductors; (2) investigation of the synthesis and processing of thallium-based high-temperature superconducting thick films; (3) process development and characterization of high-temperature superconducting wire and tape, and (4) cryogenic design of a high-temperature superconducting motor. This report outlines the research that has been performed during FY93 in each of these four areas. A brief background of each project is included to provide historical context and perspective. Major areas of research are described, although no attempt has been made to exhaustively include all work performed in each of these areas

LHC Abort Gap Monitoring and Cleaning

CERN Document Server

Meddahi, M; Boccardi, A; Butterworth, A; Fisher, A S; Gianfelice-Wendt, E; Goddard, B; Hemelsoet, G H; Höfle, W; Jacquet, D; Jaussi, M; Kain, V; Lefevre, T; Shaposhnikova, E; Uythoven, J; Valuch, D

2010-01-01

Unbunched beam is a potentially serious issue in the LHC as it may quench the superconducting magnets during a beam abort. Unbunched particles, either not captured by the RF system at injection or leaking out of the RF bucket, will be removed by using the existing damper kickers to excite resonantly the particles in the abort gap. Following beam simulations, a strategy for cleaning the abort gap at different energies was proposed. The plans for the commissioning of the beam abort gap cleaning are described and first results from the beam commissioning are presented.

Superconducting instabilities and quasipartical interference in the LiFeAs and Co-doped NaFeAs iron-based superconductors

Energy Technology Data Exchange (ETDEWEB)

Altenfeld, Dustin; Ahn, Felix; Eremin, Ilya [Institut fuer Theoretische Physik III, Ruhr-Universitaet Bochum, D-44801 Bochum (Germany); Borisenko, Sergey [Leibniz-Institute for Solid State Research, IFW-Dresden, D-01171 Dresden (Germany)

2015-07-01

We analyze and compare the structure of the pairing interaction and superconducting gaps in LiFeAs and Co-doped NaFeAs by using the ten-orbital tight-binding model, derived from ab initio LDA calculations with hopping parameters extracted from the fit to ARPES experiments. We discuss the phase diagram and experimental probes to determine the structure of the superconducting gap in these systems with special emphasis on the quasiparticle interference, computed using the T-matrix approximation. In particular, we analyze how the superconducting state with opposite sign of the gaps on the two inner hole pockets in LiFeAs evolve upon changing the parameters towards NaFeAs compound.

Superconducting Gap Symmetry of LaFeP(O,F Observed by Impurity Doping Effect

Directory of Open Access Journals (Sweden)

Shigeki Miyasaka

2016-08-01

Full Text Available We have investigated Mn, Co and Ni substitution effects on polycrystalline samples of LaFePO0.95F0.05 by resistivity and magnetoresistance measurements. In LaFe1-xMxPO0.95F0.05 (M = Mn, Co and Ni, the superconducting transition temperature (Tc monotonously decreases with increasing the impurity doping level of x. There is a clear difference of Tc suppression rates among Mn, Co and Ni doping cases, and the decreasing rate of Tc by Mn doping as a magnetic impurity is larger than those by the nonmagnetic doping impurities (Co/Ni. This result indicates that in LaFePO0.95F0.05, Tc is rapidly suppressed by the pair-breaking effect of magnetic impurities, and the pairing symmetry is a full-gapped s-wave. In the nonmagnetic impurity-doped systems, the residual resistivity in the normal state has nearly the same value when Tc becomes zero. The residual resistivity value is almost consistent with the universal value of sheet resistance for two-dimensional superconductors, suggesting that Tc is suppressed by electron localization in Co/Ni-doped LaFePO0.95F0.05.

Effect of superconducting correlation on the localization of quasiparticles in low dimensions

International Nuclear Information System (INIS)

Xiang, T.

1995-01-01

Localization lengths of superconducting quasiparticles λ s are evaluated and compared with the corresponding normal-state values λ n in one-dimensional (1D) and two-dimensional lattices. The effect of superconducting correlation on the localization of quasiparticles is generally stronger in an off-site pairing state than in an on-site pairing state. The modification of superconducting correlation to λ is strongly correlated with the density of states (DOS) of superconducting quasiparticles. λ s drops within the energy gap but is largely enhanced around energies where DOS peaks appear. For a gapless pairing state in 1D or a d-wave pairing state in 2D, λ s /λ n at the Fermi energy E F is of order 1 and determined purely by the value of gap parameter not by the random potential. For the d-wave pairing state, the localization effect is largely weakened compared with the corresponding normal state and quasiparticles with energies close to E F are more strongly localized than other low-energy quasiparticles

Superconducting spiral phase in the two-dimensional t-J model

International Nuclear Information System (INIS)

Sushkov, Oleg P.; Kotov, Valeri N.

2004-01-01

We analyze the t-t ' -t '' -J model, relevant to the superconducting cuprates. By using chiral perturbation theory we have determined the ground state to be a spiral for small doping δ1 near half filling. In this limit the solution does not contain any uncontrolled approximations. We evaluate the spin-wave Green's functions and address the issue of stability of the spiral state, leading to the phase diagram of the model. At t ' =t '' =0 the spiral state is unstable towards a local enhancement of the spiral pitch, and the nature of the true ground state remains unclear. However, for values of t ' and t '' corresponding to real cuprates the (1,0) spiral state is stabilized by quantum fluctuations ('order from disorder' effect). We show that at δ≅0.119 the spiral is commensurate with the lattice with a period of eight lattice spacings. It is also demonstrated that spin-wave mediated superconductivity develops in the spiral state and a lower limit for the superconducting gap is derived. Even though one cannot classify the gap symmetry according to the lattice representations (s,p,d, ellipsis (horizontal)) since the symmetry of the lattice is spontaneously broken by the spiral, the gap always has lines of nodes along the (1,±1) directions

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.

Superconductivity

International Nuclear Information System (INIS)

Narlikar, A.V.

1993-01-01

Amongst the numerous scientific discoveries that the 20th century has to its credit, superconductivity stands out as an exceptional example of having retained its original dynamism and excitement even for more than 80 years after its discovery. It has proved itself to be a rich field by continually offering frontal challenges in both research and applications. Indeed, one finds that a majority of internationally renowned condensed matter theorists, at some point of their career, have found excitement in working in this important area. Superconductivity presents a unique example of having fetched Nobel awards as many as four times to date, and yet, interestingly enough, the field still remains open for new insights and discoveries which could undeniably be of immense technological value. 1 fig

Control of the superconducting magnet power supply for SECRAL

International Nuclear Information System (INIS)

Zhou Wenxiong; Wang Yanyu; Zhou Detai; Lu Wang; Feng Yucheng; Su Jianjun

2014-01-01

The control of the superconducting magnet power supply (SMPS) is very important for Superconducting Electron Cyclotron Resonance Ion source with Advanced design in Lanzhou (SECRAL). In order to improve the safety and the reliability of the SMPS, a remote control system was designed and implemented. There are four power supplies needed to be controlled with suitable strategy to avoid the quench of the superconducting magnet. These four power supplies are used to supply four superconducting solenoids. Because the value and the changing rates of the current for these four solenoids are different, the power supplies must be operated synchronously to keep the current of the solenoids balanced. In this paper, we provide a detailed description for the control strategy of the four power supplies and the architecture of the hardware and the software. A serial switch is used for protocol conversion between TCP/IP and RS232 in firmware. And the software is implemented using VC++. The system can operate the four power supplies automatically after it is triggered. With the help of the control system, operation of the SMPS gets easier and safer. (authors)

Detection of bacterial endotoxin in food: New planar interdigital sensors based approach

KAUST Repository

Abdul Rahman, Mohd Syaifudin; Mukhopadhyay, Subhas Chandra; Yu, Paklam; Goicoechea, J.; Matias, Ignacio R.; Gooneratne, Chinthaka Pasan; Kosel, Jü rgen

2013-01-01

coating thickness on sensor sensitivity, selectivity and stability. Different food samples contaminated with endotoxin were also tested to verify that the interdigital sensing approach is able to be used for endotoxin detection. © 2012 Elsevier Ltd. All

Characteristics of persistent-current mode of HTS coil on superconducting electromagnet

International Nuclear Information System (INIS)

Lee, C.Y.; Kim, J.; Han, Y.J.; Kang, B.; Chung, Y.D.; Yoon, Y.S.; Chu, S.Y.; Hwang, Y.J.; Jo, H.C.; Jang, J.Y.; Ko, T.K.

2011-01-01

The levitation gap of an electromagnetic suspension (EMS) system affects the current decay rate of superconducting electromagnet. The presence of iron core provides a significant benefit in the PCM performance of SC coil. The increased levitation gap of the EMS model with the SC-EM could negatively affect the design of SC-EM operated in PCM. This paper investigates the way in which the levitation gap of an electromagnetic suspension (EMS) system affects the current decay rate of superconducting electromagnet (SC-EM) operated in persistence-current mode (PCM). Using inductance analyzed from the magnetic circuit of an EMS model, the current decay rate caused by the variation in the levitation gap was simulated. In order to experimentally verify the simulation results, we fabricated a small-scale EMS model with SC coil operated in PCM and measured the current decay rates at different levitation gaps. The result showed that the presence of iron core provides a significant benefit in the PCM performance of SC coil, but the benefit decreased as the levitation gap increases. This study revealed that the increased levitation gap of the EMS model with the SC-EM could negatively affect the design of SC-EM operated in PCM.

Superconducting classes in heavy fermions systems

International Nuclear Information System (INIS)

Volovik, G.E.; Gor'kov, L.P.

1985-01-01

A mathematical method for constructing of the superconductivity classes for nontrivial superconductors is described. All superconducting phases which can arise directly on transition from the normal state for cubic, hexagonal and tetragonal symmetries are enumerated. It is shown that in the triplet case the types of zeros in the energy gap always correspond to points on the Fermi surface, whereas for signlet pairing the whole zero lines are possible. For the phases with zeros on the lines or points, the low-temperature specific heat varies as T 2 on T 3 respectivelty. The superconducting phases which arise from the multydimensional representations may possess a magnetic moment which induces currents on the surface of a monodomain sample even in the absence of an external magnetic field. The specific case of a domain wall is considered and it is shown that large magnetic currents of magnetization are present in the wall

Current distribution characteristics of superconducting parallel circuits

International Nuclear Information System (INIS)

Mori, K.; Suzuki, Y.; Hara, N.; Kitamura, M.; Tominaka, T.

1994-01-01

In order to increase the current carrying capacity of the current path of the superconducting magnet system, the portion of parallel circuits such as insulated multi-strand cables or parallel persistent current switches (PCS) are made. In superconducting parallel circuits of an insulated multi-strand cable or a parallel persistent current switch (PCS), the current distribution during the current sweep, the persistent mode, and the quench process were investigated. In order to measure the current distribution, two methods were used. (1) Each strand was surrounded with a pure iron core with the air gap. In the air gap, a Hall probe was located. The accuracy of this method was deteriorated by the magnetic hysteresis of iron. (2) The Rogowski coil without iron was used for the current measurement of each path in a 4-parallel PCS. As a result, it was shown that the current distribution characteristics of a parallel PCS is very similar to that of an insulated multi-strand cable for the quench process

Superconductivity induced by interfacial coupling to magnons

Science.gov (United States)

Rohling, Niklas; Fjærbu, Eirik Løhaugen; Brataas, Arne

2018-03-01

We consider a thin normal metal sandwiched between two ferromagnetic insulators. At the interfaces, the exchange coupling causes electrons within the metal to interact with magnons in the insulators. This electron-magnon interaction induces electron-electron interactions, which in turn can result in p -wave superconductivity. We solve the gap equation numerically and estimate the critical temperature. In yttrium iron garnet (YIG)-Au-YIG trilayers, superconductivity sets in at temperatures somewhere in the interval between 1 and 10 K. EuO-Au-EuO trilayers require a lower temperature, in the range from 0.01 to 1 K.

Magnetic, superconducting and electron-boson properties of GdO(F)FeAs oxypnictides

Science.gov (United States)

Kuzmicheva, Tatiana; Sadakov, Andrey; Muratov, Andrei; Kuzmichev, Svetoslav; Khlybov, Yevgeny; Kulikova, Lyudmila; Eltsev, Yuri

2018-05-01

We performed comprehensive studies of nearly optimal fluorine-substituted GdO1-xFx FeAs oxypnictide superconductors with TC = 48 - 53 K . Specific heat measurements revealed a sharp peak at T = 3.5 K that shifts to lower temperatures with magnetic field increase. This peak corresponds to an antiferromagnetic ordering in Gd3+ ion sublattice and may indicate coexistence between superconducting and magnetic orderings. Andreev transport through artificially made constriction demonstrated two channels for the carriers from the band(s) with the large superconducting gap as well as from those with the small gap. As expected, the presence of a transport channel with the bands mixing (ΔL +ΔS) was not detected. Using intrinsic multiple Andreev reflections effect (IMARE) spectroscopy, we determined two superconducting gaps, ΔS ≈ 2.7 meV , and ΔL ≈ 11.6 meV . The reproducible fine structure in the dI(V)/dV spectra of the Andreev contacts (satellites of the main subharmonic gap structure for ΔL) was interpreted as caused by a resonant emission of bosons with the energy ε0 = 12 - 15 meV ≈ΔL +ΔS during the process of multiple Andreev reflections (MAR) for normal carriers in ΔL-band(s) transport channel.

Superconducting Magnet with the Minimum Steel Yoke for the Hadron Future Circular Collider Detector

CERN Document Server

Klyukhin, V I; Ball, A.; Curé, B.; Dudarev, A.; Gaddi, A.; Gerwig, H.; Mentink, M.; Da Silva, H. Pais; Rolando, G.; ten Kate, H. H. J.; Berriaud, C.P.

2016-01-01

The conceptual design study of a hadron Future Circular Collider (FCC-hh) with a center-of-mass energy of the order of 100 TeV in a new tunnel of 80-100 km circumference assumes the determination of the basic requirements for its detectors. A superconducting solenoid magnet of 12 m diameter inner bore with the central magnetic flux density of 6 T in combination with two superconducting dipole and two conventional toroid magnets is proposed for a FCC-hh experimental setup. The coil of 23.468 m long has seven 3.35 m long modules included into one cryostat. The steel yoke with a mass of 22.6 kt consists of two barrel layers of 0.5 m radial thickness, and the 0.7 m thick nose disk and four 0.6 m thick end-cap disks each side. The maximum outer diameter of the yoke is 17.7 m; the length is 62.6 m. The air gaps between the end-cap disks provide the installation of the muon chambers up to the pseudorapidity about \\pm 2.7. The superconducting dipole magnets allow measuring the charged particle momenta in the pseudora...

Unconventional superconductivity and surface pairing symmetry in half-Heusler compounds

Science.gov (United States)

Wang, Qing-Ze; Yu, Jiabin; Liu, Chao-Xing

2018-06-01

Signatures of nodal line/point superconductivity [Kim et al., Sci. Adv. 4, eaao4513 (2018), 10.1126/sciadv.aao4513; Brydon et al., Phys. Rev. Lett. 116, 177001 (2016), 10.1103/PhysRevLett.116.177001] have been observed in half-Heusler compounds, such as LnPtBi (Ln = Y, Lu). Topologically nontrivial band structures, as well as topological surface states, have also been confirmed by angular-resolved photoemission spectroscopy in these compounds [Liu et al., Nat. Commun. 7, 12924 (2016), 10.1038/ncomms12924]. In this paper, we present a systematical classification of possible gap functions of bulk states and surface states in half-Heusler compounds and the corresponding topological properties based on the representations of crystalline symmetry group. Different from all the previous studies based on the four band Luttinger model, our study starts with the six-band Kane model, which involves both four p-orbital type of Γ8 bands and two s-orbital type of Γ6 bands. Although the Γ6 bands are away from the Fermi energy, our results reveal the importance of topological surface states, which originate from the band inversion between Γ6 and Γ8 bands, in determining surface properties of these compounds in the superconducting regime by combining topological bulk state picture and nontrivial surface state picture.

Field theory methods applied for the study of superconductivity in one-dimensional systems

International Nuclear Information System (INIS)

Martins, M.J.

1986-01-01

It is shown that the Froehlich's hamiltonian in one spatial dimension is identical to that of an exactly solvable field Theory. The spectrum of the theory is computed. A critical coupling is found above which the system becomes unstable, indicating a superconducting transition. It is also proposed and investigated a renormalizable relativistic field theory model in two space-time dimensions, with quartic self-interaction among N species of fermions, which undergoes dynamical generation of a superconducting gap and is asymptotically free. A finite temperature is introduced and, for N -> ∞ a critical value T c is found above which the gap vanishes. (author)

Phase II trial evaluating the feasibility of interdigitating folfox with chemoradiotherapy in locally advanced and metastatic rectal cancer.

Science.gov (United States)

Michael, M; Chander, S; McKendrick, J; MacKay, J R; Steel, M; Hicks, R; Heriot, A; Leong, T; Cooray, P; Jefford, M; Zalcberg, J; Bressel, M; McClure, B; Ngan, S Y

2014-11-11

Patients (pts) with metastatic rectal cancer and symptomatic primary, require local and systemic control. Chemotherapy used during chemoradiotherapy (CRT) is adequate for radiosensitisation, but suboptimal for systemic control. The aim of this phase II study was to assess tolerability, local/systemic benefits, of a novel regimen delivering interdigitating intensive chemotherapy with radical CRT. Eligible pts had untreated synchronous symptomatic primary/metastatic rectal cancer. A total of 12 weeks of treatment with split-course pelvic CRT (total 50.4 Gy with concurrent oxaliplatin and 5-FU infusion) alternating with FOLFOX chemotherapy. All pts staged with CT, MRI and FDG-PET pre and post treatment. Twenty-six pts were treated. Rectal primary MRI stage: T3 81% and T4 15%. Liver metastases in 81%. Twenty-four pts (92%) completed the 12-week regimen. All patients received planned RT dose, and for both agents over 88% of patients achieved a relative dose intensity of >75%. Grade 3 toxicities: neutropenia 23%, diarrhoea 15%, and radiation skin reaction 12%. Grade 4 toxicity: neutropenia 15%. FDG-PET metabolic response rate for rectal primary 96%, and for metastatic disease 60%. Delivery of interdigitating chemotherapy with radical CRT was feasible to treat both primary and metastatic rectal cancer. High completion and response rates were encouraging.

Interplay of antiferromagnetism and superconductivity in cuprates with impurity effect and d-wave pairing

Energy Technology Data Exchange (ETDEWEB)

Mohapatra, Rasmita, E-mail: rmrmmohapatra@gmail.com [P.G. Department of Applied Physics and Ballistics, F.M. University, Balasore, Odisha 756019 (India); Rout, G.C., E-mail: gcr@iopb.res.in [Physics Enclave, Plot no-664/4825, Lane-4A, Shree Vihar, Patia, Bhubaneswar, Odisha 751024 (India)

2015-05-15

Highlights: • We considered here the interplay of antiferromagnetism (AFM) and Superconductivity (SC) with d-wave pairing symmetry in presence of impurity effect. • The tunneling conductance explains the multiple peaks and dip-hump structure. • It is observed that AFM coupling enhances the superconducting transition temperature. • The low temperature specific heat anomaly due to impurity atoms. - Abstract: We present here a model Hamiltonian to study the interplay between staggered magnetic field and the superconductivity with d-wave pairing symmetry in presence of hybridization between impurity f-electrons of rare-earth ions and 3d-electrons of copper ions. The staggered field and superconducting (SC) gaps are calculated by Green’s function technique and solved self-consistently. The coupling constants are compared using s-wave and d-wave pairings. The strength of hybridization suppresses the magnitude of the gaps; while antiferromagnetic coupling enhances the superconducting transition temperature, but suppresses the Neel temperature. The density of states (DOS) representing tunneling conductance shows complex character with impurity level lying at the Fermi level. The electronic specific heat explains prototype heavy fermion behavior in cuprate systems at low temperatures.

Interplay of antiferromagnetism and superconductivity in cuprates with impurity effect and d-wave pairing

International Nuclear Information System (INIS)

Mohapatra, Rasmita; Rout, G.C.

2015-01-01

Highlights: • We considered here the interplay of antiferromagnetism (AFM) and Superconductivity (SC) with d-wave pairing symmetry in presence of impurity effect. • The tunneling conductance explains the multiple peaks and dip-hump structure. • It is observed that AFM coupling enhances the superconducting transition temperature. • The low temperature specific heat anomaly due to impurity atoms. - Abstract: We present here a model Hamiltonian to study the interplay between staggered magnetic field and the superconductivity with d-wave pairing symmetry in presence of hybridization between impurity f-electrons of rare-earth ions and 3d-electrons of copper ions. The staggered field and superconducting (SC) gaps are calculated by Green’s function technique and solved self-consistently. The coupling constants are compared using s-wave and d-wave pairings. The strength of hybridization suppresses the magnitude of the gaps; while antiferromagnetic coupling enhances the superconducting transition temperature, but suppresses the Neel temperature. The density of states (DOS) representing tunneling conductance shows complex character with impurity level lying at the Fermi level. The electronic specific heat explains prototype heavy fermion behavior in cuprate systems at low temperatures

Magnetic field dependence of the superconducting proximity effect in a two atomic layer thin metallic film

Energy Technology Data Exchange (ETDEWEB)

Caminale, Michael; Leon Vanegas, Augusto A.; Stepniak, Agnieszka; Oka, Hirofumi; Fischer, Jeison A.; Sander, Dirk; Kirschner, Juergen [Max-Planck-Institut fuer Mikrostrukturphysik, Halle (Germany)

2015-07-01

The intriguing possibility to induce superconductivity in a metal, in direct contact with a superconductor, is under renewed interest for applications and for fundamental aspects. The underlying phenomenon is commonly known as proximity effect. In this work we exploit the high spatial resolution of scanning tunneling spectroscopy at sub-K temperatures and in magnetic fields. We probe the differential conductance along a line from a superconducting 9 ML high Pb nanoisland into the surrounding two layer thin Pb/Ag wetting layer on a Si(111) substrate. A gap in the differential conductance indicates superconductivity of the Pb island. We observe an induced gap in the wetting layer, which decays with increasing distance from the Pb island. This proximity length is 21 nm at 0.38 K and 0 T. We find a non-trivial dependence of the proximity length on magnetic field. Surprisingly, we find that the magnetic field does not affect the induced superconductivity up to 0.3 T. However, larger fields of 0.6 T suppress superconductivity in the wetting layer, where the Pb island still remains superconducting. We discuss the unexpected robustness of induced superconductivity in view of the high electronic diffusivity in the metallic wetting layer.

Superconducting linac booster

International Nuclear Information System (INIS)

Srinivasan, B.; Betigeri, M.G.; Pandey, M.K.; Pillay, R.G.; Kurup, M.B.

1997-01-01

The report on superconducting LINAC booster, which is a joint project of Bhabha Atomic Research Centre (BARC) and Tata Institute of Fundamental Research (TIFR), brings out the work accomplished so far towards the development of the technology of superconducting LINAC to boost the energy of ions from the 14UD Pelletron. The LINAC is modular in construction with each module comprising of a helium cryostat housing four lead-plated quarter wave resonators. The resonators are superconducting for temperatures below 7.19K. An energy boost of 2 MeV/q per module is expected to be achieved. The first module and the post-tandem superbuncher have been fabricated and tested on the LINAC beam line. This report gives a summary of the technological achievements and also brings out the difficulties encountered during the R and D phase. (author)

Non-uniform absorption of terahertz radiation on superconducting hot electron bolometer microbridges

International Nuclear Information System (INIS)

Miao, W.; Zhang, W.; Zhong, J. Q.; Shi, S. C.; Delorme, Y.; Lefevre, R.; Feret, A.; Vacelet, T.

2014-01-01

We interpret the experimental observation of a frequency-dependence of superconducting hot electron bolometer (HEB) mixers by taking into account the non-uniform absorption of the terahertz radiation on the superconducting HEB microbridge. The radiation absorption is assumed to be proportional to the local surface resistance of the HEB microbridge, which is computed using the Mattis-Bardeen theory. With this assumption the dc and mixing characteristics of a superconducting niobium-nitride (NbN) HEB device have been modeled at frequencies below and above the equilibrium gap frequency of the NbN film

10th International Symposium on Superconductivity

CERN Document Server

Hirabayashi, Izumi

1998-01-01

The International Symposium on Superconductivity, which has been held annu­ ally since 1988, is a forum for presenting the most up-to-date information about a broad range of research and development in superconductivity, from funda­ mental aspects to applications. More than 10 years have passed since the discovery of oxide superconductors and since various developments of applications began. It may be said that the prospects for application of oxide superconductors recently have opened up. Great progress has been made toward practical use, for example, of the flywheel, which uses bulk materials, and the high-performance cryo-cooled magnet made of bismuth wire. These were the results of persistent efforts to develop materials from the viewpoint of materials science and engineering. Also important is the progress in comprehensive understanding of high­ temperature superconductivity. Unique electronic properties of cuprates such as the non-Fermi liquid normal state, spin-charge separation, spin gap, and d-wav...

Broadband illumination of superconducting pair breaking photon detectors

International Nuclear Information System (INIS)

Guruswamy, T; Goldie, D J; Withington, S

2016-01-01

Understanding the detailed behaviour of superconducting pair breaking photon detectors such as Kinetic Inductance Detectors (KIDs) requires knowledge of the nonequilibrium quasiparticle energy distributions. We have previously calculated the steady state distributions resulting from uniform absorption of monochromatic sub gap and above gap frequency radiation by thin films. In this work, we use the same methods to calculate the effect of illumination by broadband sources, such as thermal radiation from astrophysical phenomena or from the readout system. Absorption of photons at multiple above gap frequencies is shown to leave unchanged the structure of the quasiparticle energy distribution close to the superconducting gap. Hence for typical absorbed powers, we find the effects of absorption of broadband pair breaking radiation can simply be considered as the sum of the effects of absorption of many monochromatic sources. Distribution averaged quantities, like quasiparticle generation efficiency η, match exactly a weighted average over the bandwidth of the source of calculations assuming a monochromatic source. For sub gap frequencies, however, distributing the absorbed power across multiple frequencies does change the low energy quasiparticle distribution. For moderate and high absorbed powers, this results in a significantly larger η–a higher number of excess quasiparticles for a broadband source compared to a monochromatic source of equal total absorbed power. Typically in KIDs the microwave power absorbed has a very narrow bandwidth, but in devices with broad resonance characteristics (low quality factors), this increase in η may be measurable. (paper)

Low-Symmetry Gap Functions of Organic Superconductors

Science.gov (United States)

Mori, Takehiko

2018-04-01

Superconducting gap functions of various low-symmetry organic superconductors are investigated starting from the tight-binding energy band and the random phase approximation by numerically solving Eliashberg's equation. The obtained singlet gap function is approximately represented by an asymmetrical dx2 - y2 form, where two cosine functions are mixed in an appropriate ratio. This is usually called d + s wave, where the ratio of the two cosine functions varies from 1:1 in the two-dimensional limit to 1:0 in the one-dimensional limit. A single cosine function does not make a superconducting gap in an ideal one-dimensional conductor, but works as a relevant gap function in quasi-one-dimensional conductors with slight interchain transfer integrals. Even when the Fermi surface is composed of small pockets, the gap function is obtained supposing a globally connected elliptical Fermi surface. In such a case, we have to connect the second energy band in the second Brillouin zone. The periodicity of the resulting gap function is larger than the first Brillouin zone. This is because the susceptibility has peaks at 2kF, where the periodicity has to be twice the size of the global Fermi surface. In general, periodicity of gap function corresponds to one electron or two molecules in the real space. In the κ-phase, two axes are nonequivalent, but the exact dx2 - y2 symmetry is maintained because the diagonal transfer integral introduced to a square lattice is oriented to the node direction of the dx2 - y2 wave. By contrast, the θ-phase gap function shows considerable anisotropy because a quarter-filled square lattice has a different dxy symmetry.

Topological crystalline superconductivity and second-order topological superconductivity in nodal-loop materials

Science.gov (United States)

Shapourian, Hassan; Wang, Yuxuan; Ryu, Shinsei

2018-03-01

We study the intrinsic fully gapped odd-parity superconducting order in doped nodal-loop materials with a torus-shaped Fermi surface. We show that the mirror symmetry, which protects the nodal loop in the normal state, also protects the superconducting state as a topological crystalline superconductor. As a result, the surfaces preserving the mirror symmetry host gapless Majorana cones. Moreover, for a Weyl-loop system (twofold degenerate at the nodal loop), the surfaces that break the mirror symmetry (those parallel to the bulk nodal loop) contribute a Chern (winding) number to the quasi-two-dimensional system in a slab geometry, which leads to a quantized thermal Hall effect and a single Majorana zero mode bound at a vortex line penetrating the system. This Chern number can be viewed as a higher-order topological invariant, which supports hinge modes in a cubic sample when mirror symmetry is broken. For a Dirac-loop system (fourfold degenerate at the nodal loop), the fully gapped odd-parity state can be either time-reversal symmetry-breaking or symmetric, similar to the A and B phases of 3He. In a slab geometry, the A phase has a Chern number two, while the B phase carries a nontrivial Z2 invariant. We discuss the experimental relevance of our results to nodal-loop materials such as CaAgAs.

Superconductivity mediated by anharmonic phonons: application to β-pyrochlore oxides

Science.gov (United States)

Hattori, Kazumasa; Tsunetsugu, Hirokazu

2010-03-01

We investigate three dimensional anharmonic phonons under tetrahedral symmetry and superconductivity mediated by these phonons. Three dimensional anharmonic phonon spectra are calculated directly by solving Schr"odinger equation and the superconducting transition temperature is determined by using the theory of strong coupling superconductivity assuming an isotropic gap function. With increasing the third order anharmonicity b of the tetrahedral potential, we find a crossover in the energy spectrum to a quantum tunneling regime. We obtain strongly enhanced transition temperatures around the crossover point. The first order transition observed in KOs2O6 is discussed in terms of the first excited state energy δ, and the coupling constant λ in the strong coupling theory of superconductivity. Our results suggest that the decrease of λ and increase of δ below the first order transition temperature. We point out that the change in the oscillation amplitude and characterizes this isomorphic transition. The chemical trends of the superconducting transition temperature, λ, and δ in the β-pyrochlore compounds are also discussed.

Unconventional superconductivity in a two-dimensional repulsive gas of fermions with spin-orbit coupling

Science.gov (United States)

Wang, Luyang; Vafek, Oskar

2014-02-01

We investigate the superconducting instability of a two-dimensional repulsive Fermi gas with Rashba spin-orbit coupling αR. Using renormalization group approach, we find the superconducting transition temperature as a function of the dimensionless ratio Θ=1}/{2}mαR2/EF where EF = 0 when the smaller Fermi surface shrinks to a (Dirac) point. The general trend is that superconductivity is enhanced as Θ increases, but in an intermediate regime Θ ∼ 0.1, a dome-like behavior appears. At a very small value of Θ, the angular momentum channel jz in which superconductivity occurs is quite high. With increasing Θ, jz decreases with a step of 2 down to jz = 6, after which we find the sequence jz = 6, 4, 6, 2, the last value of which continues to Θ → ∞. In an extended range of Θ, the superconducting gap predominantly resides on the large Fermi surface, while Josephson coupling induces a much smaller gap on the small Fermi surface. Below the superconducting transition temperature, we apply mean field theory to derive the self-consistent equations and find the condensation energies. The state with the lowest condensation energy is an unconventional superconducting state which breaks time-reversal symmetry, and in which singlet and triplet pairings are mixed. In general, these states are topologically nontrivial, and the Chern number of the state with total angular momentum jz is C = 2jz.

Higher order mode damping in a five-cell superconducting rf cavity with a photonic band gap coupler cell

Science.gov (United States)

Arsenyev, Sergey A.; Temkin, Richard J.; Shchegolkov, Dmitry Yu.; Simakov, Evgenya I.; Boulware, Chase H.; Grimm, Terry L.; Rogacki, Adam R.

2016-08-01

We present a study of higher order mode (HOM) damping in the first multicell superconducting radio-frequency (SRF) cavity with a photonic band gap (PBG) coupler cell. Achieving higher average beam currents is particularly desirable for future light sources and particle colliders based on SRF energy-recovery linacs (ERLs). Beam current in ERLs is limited by the beam breakup instability, caused by parasitic HOMs interacting with the beam in accelerating cavities. A PBG cell incorporated in an accelerating cavity can reduce the negative effect of HOMs by providing a frequency selective damping mechanism, thus allowing significantly higher beam currents. The five-cell cavity with a PBG cell was designed and optimized for HOM damping. Monopole and dipole HOMs were simulated. The SRF cavity was fabricated and tuned. External quality factors for some HOMs were measured in a cold test. The measurements agreed well with the simulations.

Higher order mode damping in a five-cell superconducting rf cavity with a photonic band gap coupler cell

Directory of Open Access Journals (Sweden)

Sergey A. Arsenyev

2016-08-01

Full Text Available We present a study of higher order mode (HOM damping in the first multicell superconducting radio-frequency (SRF cavity with a photonic band gap (PBG coupler cell. Achieving higher average beam currents is particularly desirable for future light sources and particle colliders based on SRF energy-recovery linacs (ERLs. Beam current in ERLs is limited by the beam breakup instability, caused by parasitic HOMs interacting with the beam in accelerating cavities. A PBG cell incorporated in an accelerating cavity can reduce the negative effect of HOMs by providing a frequency selective damping mechanism, thus allowing significantly higher beam currents. The five-cell cavity with a PBG cell was designed and optimized for HOM damping. Monopole and dipole HOMs were simulated. The SRF cavity was fabricated and tuned. External quality factors for some HOMs were measured in a cold test. The measurements agreed well with the simulations.

Electride and superconductivity behaviors in Mn5Si3-type intermetallics

Science.gov (United States)

Zhang, Yaoqing; Wang, Bosen; Xiao, Zewen; Lu, Yangfan; Kamiya, Toshio; Uwatoko, Yoshiya; Kageyama, Hiroshi; Hosono, Hideo

2017-08-01

Electrides are unique in the sense that they contain localized anionic electrons in the interstitial regions. Yet they exist with a diversity of chemical compositions, especially under extreme conditions, implying generalized underlying principles for their existence. What is rarely observed is the combination of electride state and superconductivity within the same material, but such behavior would open up a new category of superconductors. Here, we report a hexagonal Nb5Ir3 phase of Mn5Si3-type structure that falls into this category and extends the electride concept into intermetallics. The confined electrons in the one-dimensional cavities are reflected by the characteristic channel bands in the electronic structure. Filling these free spaces with foreign oxygen atoms serves to engineer the band topology and increase the superconducting transition temperature to 10.5 K in Nb5Ir3O. Specific heat analysis indicates the appearance of low-lying phonons and two-gap s-wave superconductivity. Strong electron-phonon coupling is revealed to be the pairing glue with an anomalously large ratio between the superconducting gap Δ0 and Tc, 2Δ0/kBTc = 6.12. The general rule governing the formation of electrides concerns the structural stability against the cation filling/extraction in the channel site.

Dielectric capacitors with three-dimensional nanoscale interdigital electrodes for energy storage.

Science.gov (United States)

Han, Fangming; Meng, Guowen; Zhou, Fei; Song, Li; Li, Xinhua; Hu, Xiaoye; Zhu, Xiaoguang; Wu, Bing; Wei, Bingqing

2015-10-01

Dielectric capacitors are promising candidates for high-performance energy storage systems due to their high power density and increasing energy density. However, the traditional approach strategies to enhance the performance of dielectric capacitors cannot simultaneously achieve large capacitance and high breakdown voltage. We demonstrate that such limitations can be overcome by using a completely new three-dimensional (3D) nanoarchitectural electrode design. First, we fabricate a unique nanoporous anodic aluminum oxide (AAO) membrane with two sets of interdigitated and isolated straight nanopores opening toward opposite planar surfaces. By depositing carbon nanotubes in both sets of pores inside the AAO membrane, the new dielectric capacitor with 3D nanoscale interdigital electrodes is simply realized. In our new capacitors, the large specific surface area of AAO can provide large capacitance, whereas uniform pore walls and hemispheric barrier layers can enhance breakdown voltage. As a result, a high energy density of 2 Wh/kg, which is close to the value of a supercapacitor, can be achieved, showing promising potential in high-density electrical energy storage for various applications.

Magnetic design of a 14 mm period prototype superconducting undulator

Energy Technology Data Exchange (ETDEWEB)

Gehlot, Mona, E-mail: mona_gehlot@yahoo.com [Insertion Device Development Laboratory, School of Physics, Devi Ahilya University, Indore 452001, MP (India); Mishra, G. [Insertion Device Development Laboratory, School of Physics, Devi Ahilya University, Indore 452001, MP (India); Institute of Engineering, UNAM (Mexico); Soleil, Paris (France); Trillaud, Frederic [Institute of Engineering, UNAM (Mexico); Sharma, Geetanjali [Soleil, Paris (France)

2017-02-21

In this paper we report the design of a 14 mm period prototype superconducting undulator that is under fabrication at Insertion Device Development Laboratory (IDDL) at Devi Ahilya Vishwavidyalaya, Indore, India. The field computations are made in RADIA and results are presented in an analytical form for computation of the on axis field and the field on the surface of the coil. On the basis of the findings, a best fit is presented for the model to calculate the field dependence on the gap and the current density. The fit is compared with Moser-Rossmanith formula proposed earlier to predict the magnetic flux density of a superconducting undulator. The field mapping is used to calculate the field integrals and its dependence on gap and current densities as well.

Designing focusing solenoids for superconducting RF accelerators

Energy Technology Data Exchange (ETDEWEB)

Davis, G.; Kashikhin, V.V.; Page, T.; Terechkine, I.; Tompkins, J.; Wokas, T.; /Fermilab

2006-08-01

The design of a focusing solenoid for use in a superconducting RF linac requires resolving a range of problems with conflicting requirements. Providing the required focusing strength contradicts the goal of minimizing the stray field on the surfaces of adjacent superconducting RF cavities. The requirement of a compact solenoid, able to fit into a gap between cavities, contradicts the need of mechanical support necessary to restrain electromagnetic forces that can result in coil motion and subsequent quenching. In this report we will attempt to address these and other issues arising during the development of focusing solenoids. Some relevant test data will also be presented.

High speed superconducting flywheel system for energy storage

Science.gov (United States)

Bornemann, H. J.; Urban, C.; Boegler, P.; Ritter, T.; Zaitsev, O.; Weber, K.; Rietschel, H.

1994-12-01

A prototype of a flywheel system with auto stable high temperature superconducting bearings was built and tested. The bearings offered good vertical and lateral stability. A metallic flywheel disk, ø 190 mm x 30 mm, was safely rotated at speeds up to 15000 rpm. The disk was driven by a 3 phase synchronous homopolar motor/generator. Maximum energy capacity was 3.8 Wh, maximum power was 1.5 KW. The dynamic behavior of the prototype was tested, characterized and evaluated with respect to axial and lateral stiffness, decay torques (bearing drag), vibrational modes and critical speeds. The bearings supports a maximum weight of 65 N at zero gap, axial and lateral stiffness at 1 mm gap were 440 N/cm and 130 N/cm, respectively. Spin down experiments were performed to investigate the energy efficiency of the system. The decay rate was found to depend upon background pressure in the vacuum chamber and upon the gap width in the bearing. At a background pressure of 5x10 -4 Torr, the coefficient of friction (drag-to-lift ratio) was measured to be 0.000009 at low speeds for 6 mm gap width in the bearing. Our results indicate that further refinement of this technology will allow operation of higly efficient superconducting flywheels in the kWh range.

The formation of Cooper pairs and the nature of superconducting currents

International Nuclear Information System (INIS)

Weisskopf, V.F.

1979-12-01

A simple physical explanation is given for the formation of Cooper pairs in a superconducting metal, for the origin of the attractive force causing the binding of the pairs, for the forming of a degenerate Bose gas by the Cooper pairs, for the finite energy gap that prevents the ensemble of electrons to change its quantum state at low temperatures, and for the existence of permanent currents in a superconducting wire. (orig.)

The formation of Cooper pairs and the nature of superconducting currents

International Nuclear Information System (INIS)

Weisskopf, V.F.

1981-01-01

A simple physical explanation is given for the formation of Cooper pairs in a superconducting metal, for the origin of the attractive force causing the binding of the pairs, for the forming of a degenerate Bose gas by the Cooper pairs, for the finite energy gap that prevents the ensemble of electrons from changing its quantum state at low temperatures, and for the existence of permanent currents in a superconducting wire. (author)

Laminitis and interdigital dermatitis and heel horn erosion. A European perspective.

Science.gov (United States)

Peterse, D J

1985-03-01

Laminitis is one of the most important claw disorders in dairy herds. Nutrition, calving, burdening of the lateral claw of the rear feet, and hereditary susceptibility are all contributing factors. Interdigital dermatitis in cattle may be a result of infection by Bacteroides nodosus and Fusobacterium necrophorum. If this infection becomes chronic, heel horn erosion is its consequence.

Superconducting transistor

International Nuclear Information System (INIS)

Gray, K.E.

1978-01-01

A three film superconducting tunneling device, analogous to a semiconductor transistor, is presented, including a theoretical description and experimental results showing a current gain of four. Much larger current gains are shown to be feasible. Such a development is particularly interesting because of its novelty and the striking analogies with the semiconductor junction transistor

Thermodynamic and fluorescence studies of the underlying factors in benzyl alcohol-induced lipid interdigitated phase.

Science.gov (United States)

Chen, C H; Hoye, K; Roth, L G

1996-09-15

To further investigate factors contributing to the action of alcohol in the solute-induced lipid interdigitation phase, thermodynamic and fluorescence polarization measurements were carried out to study the interaction of benzyl alcohol with dipalmitoyl phosphatidylcholine bilayer vesicles. The obtained results were compared with those previously reported for ethanol and cyclohexanol (L. G. Roth and C-H. Chen, Arch. Biochem. Biophys. 296, 207, 1992). Similar to ethanol, benzyl alcohol was found to exhibit a biphasic effect on the enthalpy (delta Hm) and the temperature (tm) of the lipid-phase transition and the steady-state fluorescence polarization (P) monitored by 1,6-diphenyl-1,3,5-hexatriene. At a total concentration of benzyl alcohol delta Hm and P, which were correlated with the formation of a lipid interdigitated phase, as evidenced by reported X-ray diffraction data. Combining the results with benzyl alcohol and ethanol suggested that simultaneously large changes in delta Hm and P can be used as an indication of the occurrence of a solute-induced lipid interdigitated phase. The overall interacting force in the formation of this lipid phase, as derived from the interactions of the hydroxyl portion of an alcohol with the lipid phosphate head group and the hydrophobic portion of an alcohol with the lipid hydrocarbon chains, may or may not be dominated by hydrophobic interaction. Although lipid/water partition coefficients and the contribution of hydrophobic interaction to the overall interacting force were comparable between benzyl alcohol and cyclohexanol, benzyl alcohol induced lipid interdigitated phase, but not for cyclohexanol. This was due to the ability of benzyl alcohol to be more effective than cyclohexanol in simultaneously interacting with the phosphate head group and the hydrocarbon chains of lipid.

Non-BCS superconductivity for underdoped cuprates by spin-vortex attraction

OpenAIRE

Marchetti, P. A.; Ye, F.; Su, Z. B.; Yu, L.

2011-01-01

Within a gauge approach to the t-J model, we propose a new, non-BCS mechanism of superconductivity for underdoped cuprates. The gluing force of the superconducting mechanism is an attraction between spin vortices on two different N\\'eel sublattices, centered around the empty sites described in terms of fermionic holons. The spin fluctuations are described by bosonic spinons with a gap generated by the spin vortices. Due to the no-double occupation constraint, there is a gauge attraction betwe...

Asymmetric d-wave superconducting topological insulator in proximity with a magnetic order

Science.gov (United States)

Khezerlou, M.; Goudarzi, H.; Asgarifar, S.

2018-02-01

In the framework of the Dirac-Bogoliubov-de Gennes formalism, we investigate the transport properties in the surface of a 3-dimensional topological insulator-based hybrid structure, where the ferromagnetic and superconducting orders are simultaneously induced to the surface states via the proximity effect. The superconductor gap is taken to be spin-singlet d-wave symmetry. The asymmetric role of this gap respect to the electron-hole exchange, in one hand, affects the topological insulator superconducting binding excitations and, on the other hand, gives rise to forming distinct Majorana bound states at the ferromagnet/superconductor interface. We propose a topological insulator N/F/FS junction and proceed to clarify the role of d-wave asymmetry pairing in the resulting subgap and overgap tunneling conductance. The perpendicular component of magnetizations in F and FS regions can be at the parallel and antiparallel configurations leading to capture the experimentally important magnetoresistance (MR) of junction. It is found that the zero-bias conductance is strongly sensitive to the magnitude of magnetization in FS region mzfs and orbital rotated angle α of superconductor gap. The negative MR only occurs in zero orbital rotated angle. This result can pave the way to distinguish the unconventional superconducting state in the relating topological insulator hybrid structures.

Preliminary study on a rotating armature type superconducting motor

International Nuclear Information System (INIS)

Hoshino, Tsutomu; Muta, Itsuya; Itoh, Takeshi; Hayashi, K.; Mukai, E.

1994-01-01

A rotating armature type motor with a laboratory made four pole saddle shape superconducting field winding has been constructed. Cool-down tests were carried out successfully several times.By the motor operating as a generator under no load and resistive load conditions, machine constants are obtained. The air gap field with outer magnetic shield yoke is 29% higher than without yoke. The field coil could stand current up to 120 A. The rated terminal voltage should be 200 V for 1,800 rpm (at 90 A field current). The armature coil could stand current up to 50 A, with a rate armature current value of 40 A corresponding to 15 kW at 0.98 power factor. Moreover the experimental and theoretical characteristics of the motor will be presented

Interplay between superconductivity and magnetism in iron-based superconductors

Energy Technology Data Exchange (ETDEWEB)

Chubukov, Andrey V [University of Wisconsin

2015-06-10

This proposal is for theoretical work on strongly correlated electron systems, which are at the center of experimental and theoretical activities in condensed-matter physics. The interest to this field is driven fascinating variety of observed effects, universality of underlying theoretical ideas, and practical applications. I propose to do research on Iron-based superconductors (FeSCs), which currently attract high attention in the physics community. My goal is to understand superconductivity and magnetism in these materials at various dopings, the interplay between the two, and the physics in the phase in which magnetism and superconductivity co-exist. A related goal is to understand the origin of the observed pseudogap-like behavior in the normal state. My research explores the idea that superconductivity is of electronic origin and is caused by the exchange of spin-fluctuations, enhanced due to close proximity to antiferromagnetism. The multi-orbital/multi-band nature of FeSCs opens routes for qualitatively new superconducting states, particularly the ones which break time-reversal symmetry. By all accounts, the coupling in pnictdes is below the threshold for Mott physics and I intend to analyze these systems within the itinerant approach. My plan is to do research in two stages. I first plan to address several problems within weak-coupling approach. Among them: (i) what sets stripe magnetic order at small doping, (ii) is there a preemptive instability into a spin-nematic state, and how stripe order affects fermions; (iii) is there a co-existence between magnetism and superconductivity and what are the system properties in the co-existence state; (iv) how superconductivity emerges despite strong Coulomb repulsion and can the gap be s-wave but with nodes along electron FSs, (v) are there complex superconducting states, like s+id, which break time reversal symmetry. My second goal is to go beyond weak coupling and derive spin-mediated, dynamic interaction between

Theory of the superconducting proximity effect below the transition temperature

International Nuclear Information System (INIS)

Silvert, W.

1975-01-01

The form of the low-temperature theory of the superconducting proximity effect depends on whether the non-linear terms are assumed to depend only on the local value of the gap or on its average value over some finite range. The local assumption leads to smaller values of the gap and to unphysical results at low temperatures. The effect of non-locality is significant even in the Ginsburg-Landau regime. (author)

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

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

Mathematical analysis of the multiband BCS gap equations in superconductivity

Science.gov (United States)

Yang, Yisong

2005-01-01

In this paper, we present a mathematical analysis for the phonon-dominated multiband isotropic and anisotropic BCS gap equations at any finite temperature T. We establish the existence of a critical temperature T so that, when TT, the only nonnegative gap solution is the zero solution, representing the normal phase. Furthermore, when T=T, we prove that the only gap solution is the zero solution and that the positive gap solution depend on the temperature TMarkowitz-Kadanoff model and we prove that the presence of anisotropic fluctuations enhances T as in the single-band case. A special consequence of these results is that the half-unity exponent isotope effect may rigorously be proved in the multiband BCS theory, isotropic or anisotropic.

Tunneling probe of fluctuating superconductivity in disordered thin films

Science.gov (United States)

Dentelski, David; Frydman, Aviad; Shimshoni, Efrat; Dalla Torre, Emanuele G.

2018-03-01

Disordered thin films close to the superconductor-insulator phase transition (SIT) hold the key to understanding quantum phase transition in strongly correlated materials. The SIT is governed by superconducting quantum fluctuations, which can be revealed, for example, by tunneling measurements. These experiments detect a spectral gap, accompanied by suppressed coherence peaks, on both sides of the transition. Here we describe the insulating side in terms of a fluctuating superconducting field with finite-range correlations. We perform a controlled diagrammatic resummation and derive analytic expressions for the tunneling differential conductance. We find that short-range superconducting fluctuations suppress the coherence peaks even in the presence of long-range correlations. Our approach offers a quantitative description of existing measurements on disordered thin films and accounts for tunneling spectra with suppressed coherence peaks.

A common thread in unconventional superconductivity. The functional renormalization group in multi-band systems

International Nuclear Information System (INIS)

Platt, Christian

2012-01-01

The superconducting properties of complex materials like the recently discovered iron-pnictides or strontium-ruthenate are often governed by multi-orbital effects. In order to unravel the superconductivity of those materials, we develop a multi-orbital implementation of the functional renormalization group and study the pairing states of several characteristic material systems. Starting with the iron-pnictides, we find competing spin-fluctuation channels that become attractive if the superconducting gap changes sign between the nested portions of the Fermi surface. Depending on material details like doping or pnictogen height, these spin fluctuations then give rise to s ± -wave pairing with or without gap nodes and, in some cases, also change the symmetry to d-wave. Near the transition from nodal s ± -wave to d-wave pairing, we predict the occurrence of a time-reversal symmetry-broken (s+id)-pairing state which avoids gap nodes and is therefore energetically favored. We further study the electronic instabilities of doped graphene, another fascinating material which has recently become accessible and which can effectively be regarded as multi-orbital system. Here, the hexagonal lattice structure assures the degeneracy of two d-wave pairing channels, and the system then realizes a chiral (d+id)-pairing state in a wide doping range around van-Hove filling. In addition, we also find spin-triplet pairing as well as an exotic spin-density wave phase which both become leading if the long-ranged hopping or interaction parameters are slightly modified, for example, by choosing different substrate materials. Finally, we consider the superconducting state of strontium-ruthenate, a possible candidate for chiral spin-triplet pairing with fascinating properties like the existence of half-quantum vortices obeying non-Abelian statistics. Using a microscopic three orbital description including spin-orbit coupling, we demonstrate that ferromagnetic fluctuations are still

A Four-Gap Glass-RPC Time-of-Flight Array with 90 ps Time Resolution

CERN Document Server

Akindinov, A; Formenti, F; Golovine, V; Klempt, W; Kluge, A; Martemyanov, A N; Martinengo, P; Pinhão, J; Smirnitsky, A V; Spegel, M; Szymanski, P; Zalipska, J

2001-01-01

In this paper, we describe the performance of a prototype developed in the context of the ALICE time-of-flight research and development system. The detector module consists of a 32-channel array of 3 x 3 cm2 glass resistive plate chamber (RPC) cells, each of which has four accurately space gaps of 0.3 mm thickness arranged as a pair of double-gap resisitive plate chambers. Operated with a nonflammable gas mixture at atmospheric pressure, the system achieved a time resolution of 90 ps at 98% efficiency with good uniformity and moderate crosstalk. This result shows the feasibility of large-area high-resolution time-of-flight systems based on RPCs at affordable cost.

Gap enhancement in phonon-irradiated superconducting tin films

International Nuclear Information System (INIS)

Miller, N.D.; Rutledge, J.E.

1982-01-01

We have measured the current-voltage (I-V) characteristics of tin-tin tunnel junctions driven out of equilibrium by a flux of near-thermal phonons from a heater. The reduced ambient temperature was T/T/sub c/ = 0.41. The nonequilibrium I-V curves are compared to equilibrium thermal I-V curves at an elevated temperature chosen to match the total number of quasiparticles. The nonequilibrium curves show a smaller current near zero bias and a larger gap than the thermal curves. This is the first experimental evidence of phonon-induced gap enhancement far below T/sub c/. The results are discussed in terms of the coupled kinetic equations of Chang and Scalapino

Technical Challenges and Potential Solutions for Cross-Country Multi-Terminal Superconducting DC Power Cables

Science.gov (United States)

Al-Taie, A.; Graber, L.; Pamidi, S. V.

2017-12-01

Opportunities for applications of high temperature superconducting (HTS) DC power cables for long distance power transmission in increasing the reliability of the electric power grid and to enable easier integration of distributed renewable sources into the grid are discussed. The gaps in the technology developments both in the superconducting cable designs and cryogenic systems as well as power electronic devices are identified. Various technology components in multi-terminal high voltage DC power transmission networks and the available options are discussed. The potential of ongoing efforts in the development of superconducting DC transmission systems is discussed.

Highly sensitive three-dimensional interdigitated microelectrode for microparticle detection using electrical impedance spectroscopy

International Nuclear Information System (INIS)

Chang, Fu-Yu; Chen, Ming-Kun; Jang, Ling-Sheng; Wang, Min-Haw

2016-01-01

Cell impedance analysis is widely used for monitoring biological and medical reactions. In this study, a highly sensitive three-dimensional (3D) interdigitated microelectrode (IME) with a high aspect ratio on a polyimide (PI) flexible substrate was fabricated for microparticle detection (e.g. cell quantity detection) using electroforming and lithography technology. 3D finite element simulations were performed to compare the performance of the 3D IME (in terms of sensitivity and signal-to-noise ratio) to that of a planar IME for particles in the sensing area. Various quantities of particles were captured in Dulbecco’s modified Eagle medium and their impedances were measured. With the 3D IME, the particles were arranged in the gap, not on the electrode, avoiding the noise due to particle position. For the maximum particle quantities, the results show that the 3D IME has at least 5-fold higher sensitivity than that of the planar IME. The trends of impedance magnitude and phase due to particle quantity were verified using the equivalent circuit model. The impedance (1269 Ω) of 69 particles was used to estimate the particle quantity (68 particles) with 98.6% accuracy using a parabolic regression curve at 500 kHz. (paper)

Rotational loss 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

This paper describes the experimental results for the rotational loss of a ring-shaped flywheel supported by high T c superconducting levitation. 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 rotational loss has 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 rotational loss decreased as the levitation gap height increased. In low-speed rotational regions, the rotational loss was in proportion to the rotation speed and depended more on the levitation gap. In high-speed rotational regions, the rotational loss was in proportion to the third power of the rotation speed and depended less on the levitation gap. The cubic rotational loss in He was reduced to one-fifth of that in air. The magnetic field pinned in bulk superconductors induces a loss in the materials composing the ring-shaped flywheel. The rotational loss of a ring-shaped flywheel supported by superconducting levitation can be reduced by improving the uniformity of the magnetic fields along the ring, enlargement of the bulk superconductor(s), and densely arranging the bulk superconductors. (author)

Quantitative analysis of Josephson-quasiparticle current in superconducting single-electron transistors

International Nuclear Information System (INIS)

Nakamura, Y.; Chen, C.D.; Tsai, J.S.

1996-01-01

We have investigated Josephson-quasiparticle (JQP) current in superconducting single-electron transistors in which charging energy E C was larger than superconducting gap energy Δ and junction resistances were much larger than R Q ≡h/4e 2 . We found that not only the shapes of the JQP peaks but also their absolute height were reproduced quantitatively with a theory by Averin and Aleshkin using a Josephson energy of Ambegaokar-Baratoff close-quote s value. copyright 1996 The American Physical Society

Superconducting quantum circuits theory and application

Science.gov (United States)

Deng, Xiuhao

Superconducting quantum circuit models are widely used to understand superconducting devices. This thesis consists of four studies wherein the superconducting quantum circuit is used to illustrate challenges related to quantum information encoding and processing, quantum simulation, quantum signal detection and amplification. The existence of scalar Aharanov-Bohm phase has been a controversial topic for decades. Scalar AB phase, defined as time integral of electric potential, gives rises to an extra phase factor in wavefunction. We proposed a superconducting quantum Faraday cage to detect temporal interference effect as a consequence of scalar AB phase. Using the superconducting quantum circuit model, the physical system is solved and resulting AB effect is predicted. Further discussion in this chapter shows that treating the experimental apparatus quantum mechanically, spatial scalar AB effect, proposed by Aharanov-Bohm, can't be observed. Either a decoherent interference apparatus is used to observe spatial scalar AB effect, or a quantum Faraday cage is used to observe temporal scalar AB effect. The second study involves protecting a quantum system from losing coherence, which is crucial to any practical quantum computation scheme. We present a theory to encode any qubit, especially superconducting qubits, into a universal quantum degeneracy point (UQDP) where low frequency noise is suppressed significantly. Numerical simulations for superconducting charge qubit using experimental parameters show that its coherence time is prolong by two orders of magnitude using our universal degeneracy point approach. With this improvement, a set of universal quantum gates can be performed at high fidelity without losing too much quantum coherence. Starting in 2004, the use of circuit QED has enabled the manipulation of superconducting qubits with photons. We applied quantum optical approach to model coupled resonators and obtained a four-wave mixing toolbox to operate photons

Superconducting transition in TlBiTe/sub 2/ and TlTe compounds

Energy Technology Data Exchange (ETDEWEB)

Kantser, V G; Popovich, N S; Sidorenko, A S

1985-10-01

On the basis of zone structure calculation for TlBiTe/sub 2/ and TlTe it is found that TlBiTe/sub 2/ is a narrow-gap semiconductor and TlTe is a p-metal. At Tsub(c)=0.19 K TlTe is found to experience the superconducting transition. In TlBiTe/sub 2/ superconductivity is not observed to occur up to 0.05 K, since there is a possibility of occupying the high density of states zones because they are remote from actual ones. The earlier discovered superconducting transition in TlBiTe/sub 2/ is inherent in the alien phase of TlTe.

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)

Origin of Superconductivity and Latent Charge Density Wave in NbS2

Science.gov (United States)

Heil, Christoph; Poncé, Samuel; Lambert, Henry; Schlipf, Martin; Margine, Elena R.; Giustino, Feliciano

2017-08-01

We elucidate the origin of the phonon-mediated superconductivity in 2 H -NbS2 using the ab initio anisotropic Migdal-Eliashberg theory including Coulomb interactions. We demonstrate that superconductivity is associated with Fermi surface hot spots exhibiting an unusually strong electron-phonon interaction. The electron-lattice coupling is dominated by low-energy anharmonic phonons, which place the system on the verge of a charge density wave instability. We also provide definitive evidence for two-gap superconductivity in 2 H -NbS2 , and show that the low- and high-energy peaks observed in tunneling spectra correspond to the Γ - and K -centered Fermi surface pockets, respectively. The present findings call for further efforts to determine whether our proposed mechanism underpins superconductivity in the whole family of metallic transition metal dichalcogenides.

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.

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).

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

Circuit modeling on polyaniline functionalized nanowire-templated micro-interdigital capacitors for pH sensing

DEFF Research Database (Denmark)

Antohe, V.A.; Radu, A.; Mátéfi-Tempfli, Stefan

2011-01-01

This study presents an improved alternative current (ac) circuit modeling of a highly sensitive capacitive pH-sensing element based on polyaniline (PANI) functionalized nanowire-templated micro-interdigited electrodes (NWs μIDEs). While electrical resonance measurements deal with a total equivale...

Interface-enhanced high-temperature superconductivity in single-unit-cell FeT e1 -xS ex films on SrTi O3

Science.gov (United States)

Li, Fangsen; Ding, Hao; Tang, Chenjia; Peng, Junping; Zhang, Qinghua; Zhang, Wenhao; Zhou, Guanyu; Zhang, Ding; Song, Can-Li; He, Ke; Ji, Shuaihua; Chen, Xi; Gu, Lin; Wang, Lili; Ma, Xu-Cun; Xue, Qi-Kun

2015-06-01

Recently discovered high-temperature superconductivity in single-unit-cell (UC) FeSe films on SrTi O3 (STO) substrate has stimulated tremendous research interest, both experimental and theoretical. Whether this scenario could be extended to other superconductors is vital in both identifying the enhanced superconductivity mechanism and further raising the critical transition temperature (Tc). Here we successfully prepared single-UC FeT e1 -xS ex(0.1 ≤x ≤0.6 ) films on STO substrates by molecular beam epitaxy and observed U -shaped superconducting gaps (Δ ) up to ˜16.5 meV , nearly ten times the gap value (Δ ˜1.7 meV ) of the optimally doped bulk FeT e0 .6S e0 .4 single crystal (Tc˜14.5 K ). No superconducting gap has been observed on the second UC and thicker FeT e1 -xS ex films at 5.7 K, indicating the important role of the interface. This interface-enhanced high-temperature superconductivity is further confirmed by ex situ transport measurements, which revealed an onset superconducting transition temperature above 40 K, nearly two times higher than that of the optimally doped bulk FeT e0 .6S e0 .4 single crystal. This work demonstrates that interface engineering is a feasible way to discover alternative superconductors with higher Tc.

Superconductivity of small particles

International Nuclear Information System (INIS)

Leavens, C.R.; Fenton, E.W.

1981-01-01

The Eliashberg gap equations are used to investigate the contribution of surface-phonon softening to the size dependence of the superconducting transition temperature (T/sub c/) of small metallic particles. Because of our limited quantitative knowledge of phonon spectra and electron-phonon coupling in the surface region, the effect cannot be calculated with certainty. Previous calculations which agree with experiment depend on a fortuitous choice of input parameters which cannot be justified at present. For this reason the absence of any observable size effect for T/sub c/ in Pb is especially important. This null effect is obtained in Pb if the electron-phonon coupling strength is the same in the surface region as in the bulk. This assumption can be tested experimentally because it means that the energy gap of Pb should not be independent of particle size but rather should increase significantly with decreasing radius. Hence, measurement of the size dependence of the energy gap for well-characterized small particles of Pb could provide information regarding the importance of the phonon-softening mechanism, at least for Pb

Superconducting magnets for toroidal fusion reactors

International Nuclear Information System (INIS)

Haubenreich, P.N.

1980-01-01

Fusion reactors will soon be employing superconducting magnets to confine plasma in which deuterium and tritium (D-T) are fused to produce usable energy. At present there is one small confinement experiment with superconducting toroidal field (TF) coils: Tokamak 7 (T-7), in the USSR, which operates at 4 T. By 1983, six different 2.5 x 3.5-m D-shaped coils from six manufacturers in four countries will be assembled in a toroidal array in the Large Coil Test Facility (LCTF) at Oak Ridge National Laboratory (ORNL) for testing at fields up to 8 T. Soon afterwards ELMO Bumpy Torus (EBT-P) will begin operation at Oak Ridge with superconducting TF coils. At the same time there will be tokamaks with superconducting TF coils 2 to 3 m in diameter in the USSR and France. Toroidal field strength in these machines will range from 6 to 9 T. NbTi and Nb 3 Sn, bath cooling and forced flow, cryostable and metastable - various designs are being tried in this period when this new application of superconductivity is growing and maturing

Unconventional superconductivity in PuRhGa5: Ga NMR/NQR study

International Nuclear Information System (INIS)

Sakai, H.; Tokunaga, Y.; Fujimoto, T.; Kambe, S.; Walstedt, R.E.; Yasuoka, H.; Aoki, D.; Homma, Y.; Yamamoto, E.; Nakamura, A.; Shiokawa, Y.; Nakajima, K.; Arai, Y.; Matsuda, T.D.; Haga, Y.; Onuki, Y.

2006-01-01

69,71 Ga NMR/NQR studies have been performed on a single crystal of the transuranium superconductor PuRhGa 5 with T c ∼9K. The spin-lattice relaxation rate 1/T 1 reveals that PuRhGa 5 is an unconventional superconductor having an anisotropic superconducting gap. Moreover, Korringa behavior (1/T 1 T=const.) is observed in the normal state below ∼30K. This result suggests that the superconductivity sets in after the formation of a Fermi liquid state in this compound

Spin-fluctuation mediated superconductivity and magnetic order in the cuprate La_1.88Sr_0.12CuO₄

DEFF Research Database (Denmark)

Rømer, Astrid Tranum

, show a very rich electronic phase diagram. A common feature that characterizes both cuprates, heavy fermions, and iron pnictides is the proximity to magnetic order. Therefore, the idea of spin-uctuation mediated pairing is a popular paradigm proposed for unconventional superconductivity. A _ngerprint...... of the pairing mechanism is found in the superconducting gap symmetry. Therefore the study of gap symmetries constitutes one of the most important parts of resolving the superconducting puzzle. This thesis consists of a theoretical and an experimental part. In the theoretical part, we address spin...

Cryogenic testing of the 2.1 GHz five-cell superconducting RF cavity with a photonic band gap coupler cell

Science.gov (United States)

Arsenyev, Sergey A.; Temkin, Richard J.; Haynes, W. Brian; Shchegolkov, Dmitry Yu.; Simakov, Evgenya I.; Tajima, Tsuyoshi; Boulware, Chase H.; Grimm, Terrence L.; Rogacki, Adam R.

2016-05-01

We present results from cryogenic tests of the multi-cell superconducting radio frequency (SRF) cavity with a photonic band gap (PBG) coupler cell. Achieving high average beam currents is particularly desirable for future light sources and particle colliders based on SRF energy-recovery-linacs (ERLs). Beam current in ERLs is limited by the beam break-up instability, caused by parasitic higher order modes (HOMs) interacting with the beam in accelerating cavities. A PBG cell incorporated in an accelerating cavity can reduce the negative effect of HOMs by providing a frequency selective damping mechanism, thus allowing significantly higher beam currents. The multi-cell cavity was designed and fabricated of niobium. Two cryogenic (vertical) tests were conducted. The high unloaded Q-factor was demonstrated at a temperature of 4.2 K at accelerating gradients up to 3 MV/m. The measured value of the unloaded Q-factor was 1.55 × 108, in agreement with prediction.

Superconducting quasiparticle lifetimes due to spin-fluctuation scattering

International Nuclear Information System (INIS)

Quinlan, S.M.; Scalapino, D.J.; Bulut, N.

1994-01-01

Superconducting quasiparticle lifetimes associated with spin-fluctuation scattering are calculated. A Berk-Schrieffer interaction with an irreducible susceptibility given by a BCS form is used to model the quasiparticle damping due to spin fluctuations. Results are presented for both s-wave and d-wave gaps. Also, quasiparticle lifetimes due to impurity scattering are calculated for a d-wave superconductor

Theoretical and experimental study of the bending influence on the capacitance of interdigitated micro-electrodes patterned on flexible substrates

International Nuclear Information System (INIS)

Molina-Lopez, F.; Briand, D.; Rooij, N. F. de; Kinkeldei, T.; Tröster, G.

2013-01-01

Interdigitated electrodes are common structures in the fields of microelectronics and MEMS. Recent developments in flexible electronics compel an understanding of such structures under bending constraints. In this work, the behavior of interdigitated micro-electrodes when subjected to circular bending has been theoretically and experimentally studied through changes in capacitance. An analytical model has been developed to calculate the expected variation in capacitance of such structures while undergoing outward and inward bending along the direction perpendicular to the electrodes. The model combines conformal mapping techniques to account for the electric field redistribution and fundamental aspects of solid mechanics in order to define the geometrical deformation of the electrodes while bending. To experimentally verify our theoretical predictions, several interdigitated electrode structures with different geometries were fabricated on polymeric substrates by means of photolithography. The samples, placed in a customized bending setup, were bent to controlled radii of curvature while measuring their capacitance. A maximum variation in capacitance of less than 3% was observed at a minimum radius of curvature of 2.5 mm for all the devices tested with very thin electrodes whereas changes of up to 7% were found on stiffer, plated electrodes. Larger or smaller variations would be possible, in theory, by adjusting the geometry of the device. This work establishes a useful predictive tool for the design and evaluation of truly flexible/bendable electronics consisting of interdigitated structures, allowing one to tune the bending influence on the capacitance value through geometrical design

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.

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)

Superconductivity applications for infrared and microwave devices; Proceedings of the Meeting, Orlando, FL, Apr. 19, 20, 1990

Science.gov (United States)

Bhasin, Kul B.; Heinen, Vernon O.

1990-10-01

Various papers on superconductivity applications for IR and microwave devices are presented. The individual topics addressed include: pulsed laser deposition of Tl-Ca-Ba-Cu-O films, patterning of high-Tc superconducting thin films on Si substrates, IR spectra and the energy gap in thin film YBa2Cu3O(7-delta), high-temperature superconducting thin film microwave circuits, novel filter implementation utilizing HTS materials, high-temperature superconductor antenna investigations, high-Tc superconducting IR detectors, high-Tc superconducting IR detectors from Y-Ba-Cu-O thin films, Y-Ba-Cu0-O thin films as high-speed IR detectors, fabrication of a high-Tc superconducting bolometer, transition-edge microbolometer, photoresponse of YBa2Cu3O(7-delta) granular and epitaxial superconducting thin films, fast IR response of YBCO thin films, kinetic inductance effects in high-Tc microstrip circuits at microwave frequencies.

Vertical Vibration Characteristics of a High-Temperature Superconducting Maglev Vehicle System

Science.gov (United States)

Jiang, Jing; Li, Ke Cai; Zhao, Li Feng; Ma, Jia Qing; Zhang, Yong; Zhao, Yong

2013-06-01

The vertical vibration characteristics of a high-temperature superconducting maglev vehicle system are investigated experimentally. The displacement variations of the maglev vehicle system are measured with different external excitation frequency, in the case of a certain levitation gap. When the external vibration frequency is low, the amplitude variations of the response curve are small. With the increase of the vibration frequency, chaos status can be found. The resonance frequencies with difference levitation gap are also investigated, while the external excitation frequency range is 0-100 Hz. Along with the different levitation gap, resonance frequency is also different. There almost is a linear relationship between the levitation gap and the resonance frequency.

Enhanced Andreev reflection in gapped graphene

Science.gov (United States)

Majidi, Leyla; Zareyan, Malek

2012-08-01

We theoretically demonstrate unusual features of superconducting proximity effect in gapped graphene that presents a pseudospin symmetry-broken ferromagnet with a net pseudomagnetization. We find that the presence of a band gap makes the Andreev conductance of graphene superconductor/pseudoferromagnet (S/PF) junction to behave similar to that of a graphene ferromagnet-superconductor junction. The energy gap ΔN can enhance the pseudospin inverted Andreev conductance of S/PF junction to reach a limiting maximum value for ΔN≫μ, which depending on the bias voltage can be larger than the value for the corresponding junction with no energy gap. We further demonstrate a damped-oscillatory behavior for the local density of states of the PF region of S/PF junction and a long-range crossed Andreev reflection process in PF/S/PF structure with antiparallel alignment of pseudomagnetizations of PFs, which confirm that, in this respect, the gapped normal graphene behaves like a ferromagnetic graphene.

Study of the skin effect in superconducting materials

Energy Technology Data Exchange (ETDEWEB)

Szeftel, Jacob, E-mail: jszeftel@lpqm.ens-cachan.fr [ENS Cachan, LPQM, 61 avenue du Président Wilson, 94230 Cachan (France); Sandeau, Nicolas [Aix Marseille Univ, CNRS, Centrale Marseille, Institut Fresnel, F-13013 Marseille (France); Khater, Antoine [Université du Maine, UMR 6087 Laboratoire PEC, F-72000 Le Mans (France)

2017-05-03

Highlights: • Comprehensive theoretical study of the skin effect in superconductors. • Based on Newton and Maxwell's equations. • Usual and anomalous skin effects dealt with in the same framework. - Abstract: The skin effect is analyzed to provide the numerous measurements of the penetration depth of the electromagnetic field in superconducting materials with a theoretical basis. Both the normal and anomalous skin effects are accounted for within a single framework, focusing on frequencies less than the superconducting gap. The emphasis is laid on the conditions required for the penetration depth to be equal to London's length, which enables us to validate an assumption widely used in the interpretation of all current experimental results.

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

Cooper pairs' magnetic moment in MCFL color superconductivity

International Nuclear Information System (INIS)

Feng Bo; Ferrer, Efrain J.; Incera, Vivian de la

2011-01-01

We investigate the effect of the alignment of the magnetic moments of Cooper pairs of charged quarks that form at high density in three-flavor quark matter. The high-density phase of this matter in the presence of a magnetic field is known to be the Magnetic Color-Flavor-Locked (MCFL) phase of color superconductivity. We derive the Fierz identities of the theory and show how the explicit breaking of the rotational symmetry by the uniform magnetic field opens new channels of interactions and allows the formation of a new diquark condensate. The new order parameter is a spin-1 condensate proportional to the component in the field direction of the average magnetic moment of the pairs of charged quarks. The magnitude of the spin-1 condensate becomes comparable to the larger of the two scalar gaps in the region of large fields. The existence of the spin-1 condensate is unavoidable, as in the presence of a magnetic field there is no solution of the gap equations with nonzero scalar gaps and zero magnetic moment condensate. This is consistent with the fact that the extra condensate does not break any symmetry that has not already been broken by the known MCFL gaps. The spin-1 condensate enhances the condensation energy of pairs formed by charged quarks and the magnetization of the system. We discuss the possible consequences of the new order parameter on the issue of the chromomagnetic instability that appears in color superconductivity at moderate density.

Evaluation of factor IX deficiency by interdigitated electrode (IDE)

Science.gov (United States)

Gopinath, Subash C. B.; Hashim, Uda; Uda, M. N. A.

2017-03-01

Factor IX deficiency is the main cause of hemophilia A and B. This a severe excessive bleeding disorder that can even kill the patient if not treated with the right prescription of Factor IX hormone to stop the bleeding. The bleeding can be caused by an injury or even a sudden bleeding in some very rare cases. To find the Factor IX effectiveness and to understand the deficiency more carefully for the future of medicine, experiments are conducted to test the Factor IX using the Interdigitated Electrode (IDE) and gold Nanoparticle with the help of Nanoelectrical technology.

Effects of Armature Winding Segmentation with Multiple Converters on the Short Circuit Torque of 10-MW Superconducting Wind Turbine Generators

DEFF Research Database (Denmark)

Liu, Dong; Polinder, Henk; Abrahamsen, Asger Bech

2017-01-01

Superconducting synchronous generators (SCSGs) are drawing more attention in large direct-drive wind turbine applications. Despite low weight and compactness, the short circuit torque of an SCSG may be too high for wind turbine constructions due to a large magnetic air gap of an SCSG. This paper...... aims at assessing the effects of armature winding segmentation on reducing the short circuit torque of 10-MW SCSGs. A concept of armature winding segmentation with multiple power electronic converters is presented. Four SCSG designs using different topologies are examined. Results show that armature...... winding segmentation effectively reduce the short circuit torque in all the four SCSG designs when one segment is shorted at the terminal....

Electrical and structural characterisation of nanostructured titania coatings deposited on interdigitated electrode system

International Nuclear Information System (INIS)

Milanovic, Marija; Stojanovic, Goran; Nikolic, Ljubica M.; Radovanovic, Milan; Skoric, Branko; Miletic, Aleksandar

2011-01-01

Highlights: → La/TiO 2 and Nb/TiO 2 nanocrystalline coatings as interdigitated electrode system for sensors. → A method for the computation of conductivity and relative permittivity was proposed. → Nb causes an increase of electrical properties, while La has the opposite effect. - Abstract: This paper presents the electrical properties of La- and Nb-doped nanostructured titanium dioxide (TiO 2 ) thin coatings deposited on the alumina substrate with gold electrodes in the interdigitated form to obtain appropriate devices for sensor application. Electrical parameters such as conductivity σ and permittivity ε were calculated using measured values of phase angle θ m , capacitance C m and resistance R m . These values were measured using an HP-4194A Impedance/Gain-Phase Analyzer with a Z-probe in the frequency range from 10 3 Hz to 10 8 Hz. The measured results showed that with addition of 2, 4 or 6 at% of lanthanum, conductivity and permittivity of analysed samples are decreasing, whereas the addition of niobium in the same percentage follows the opposite trend.

Dense high-aspect ratio 3D carbon pillars on interdigitated microelectrode arrays

DEFF Research Database (Denmark)

Amato, Letizia; Heiskanen, Arto; Hansen, Rasmus

2015-01-01

In this work we present high-aspect ratio carbon pillars (1.4 μm in diameter and ∼11 μm in height) on top of interdigitated electrode arrays to be used for electrochemical applications. For this purpose, different types of 2D and 3D pyrolysed carbon structures were fabricated and characterised...... of pyrolysed carbon films with increased film resistance due to oxidation during storage....

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)

Rotational loss of a ring-shaped flywheel supported by high T{sub c} superconducting levitation

Energy Technology Data Exchange (ETDEWEB)

Teshima, Hidekazu [Nippon Steel Corp., Kawasaki, Kanagawa (Japan). Advanced Materials and Technology Research Labs.; Tawara, Taichi; Shimada, Ryuichi

1997-08-01

This paper describes the experimental results for the rotational loss of a ring-shaped flywheel supported by high T{sub c} superconducting levitation. 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 rotational loss has 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 rotational loss decreased as the levitation gap height increased. In low-speed rotational regions, the rotational loss was in proportion to the rotation speed and depended more on the levitation gap. In high-speed rotational regions, the rotational loss was in proportion to the third power of the rotation speed and depended less on the levitation gap. The cubic rotational loss in He was reduced to one-fifth of that in air. The magnetic field pinned in bulk superconductors induces a loss in the materials composing the ring-shaped flywheel. The rotational loss of a ring-shaped flywheel supported by superconducting levitation can be reduced by improving the uniformity of the magnetic fields along the ring, enlargement of the bulk superconductor(s), and densely arranging the bulk superconductors. (author)

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

Evidence of a Normal-State Pseudogap in Bulk Superconducting Tunneling Junctions of YBa2Cu3O7-δ

Directory of Open Access Journals (Sweden)

Leandro Guerra

1999-12-01

Full Text Available Planar contact tunneling experiments have been performed on bulk superconducting tunneling junctions of YBa2Cu3O7-δ in the temperature range 77 -295K. A clear depression in the conductance curves measured, attributed to the pseudogap, has been observed in temperatures above Tc (approx. 90K determined from dc resistivity measurements before disappearing at T*=275K. The width of the pseudogap has been quantitatively measured as Dps, ave = 25.6meV from the differential conductance plots. These results agree with the current understanding of the phenomenology and nature of this pseudogap, namely: (I the pseudogap value is relatively temperature-independent; (2 the superconducting gap and the pseudogap have the same d-wave nature; and (3 the superconducting gap evolves from the pseudogap.

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

Isotope effect on superconductivity and Raman phonons of Pyrochlore Cd2Re2O7

Science.gov (United States)

Razavi, F. S.; Hajialamdari, M.; Reedyk, M.; Kremer, R. K.

2018-06-01

Cd2Re2O7 is the only α-Pyrochlore exhibiting superconductivity with a transition temperature (Tc) of ∼ 1 K. In this study, we present the effect of oxygen isotope (18O) as well as combined 18O and cadmium isotope (116Cd) substitution on the superconductivity and Raman scattering spectrum of Cd2Re2O7. The change of Tc and the energy gap Δ(T) are reported using various techniques including point contact spectroscopy. The shift in Raman phonon frequencies upon isotope substitution will be compared with measurement of the isotope effect on the superconducting transition temperature.

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

Excitonic Order and Superconductivity in the Two-Orbital Hubbard Model: Variational Cluster Approach

Science.gov (United States)

Fujiuchi, Ryo; Sugimoto, Koudai; Ohta, Yukinori

2018-06-01

Using the variational cluster approach based on the self-energy functional theory, we study the possible occurrence of excitonic order and superconductivity in the two-orbital Hubbard model with intra- and inter-orbital Coulomb interactions. It is known that an antiferromagnetic Mott insulator state appears in the regime of strong intra-orbital interaction, a band insulator state appears in the regime of strong inter-orbital interaction, and an excitonic insulator state appears between them. In addition to these states, we find that the s±-wave superconducting state appears in the small-correlation regime, and the dx2 - y2-wave superconducting state appears on the boundary of the antiferromagnetic Mott insulator state. We calculate the single-particle spectral function of the model and compare the band gap formation due to the superconducting and excitonic orders.

Design and Characteristics Analysis of a Rod Type High-Tc Superconducting Fault Current Limiter through Electromagnetic Analysis

Energy Technology Data Exchange (ETDEWEB)

Hyun, O.B. [Korea Electric Power Research Institute, Taejeon (Korea); Lee, C.J.; Lee, S.J.; Ko, T.K. [Yonsei University, Seoul (Korea)

2001-07-01

The existence of a large air gaps between a High-Tc Superconducting (HTS) tube and an iron core, or between a primary winding and a HTS tube possibly causes magnetic flux leaks, resulting in undesirable voltage drops under normal operation. For this reason optimization of air gaps is essential in designing a high-Tc superconducting fault current limiter (SFCL). In this paper we performed the electromagnetic analysis for the optimization. The inductance L decreases by 20% as the hight of the winding increases from 50 to 200 mm. But, L increases from 5.6 mH to 10.5 mH as the hight of the rod changes from 150 to 400 mm. L is found to be almost constant for the air gap between 5 to 10 mm, but L decreases by 20% as the gap increases from 10 to 20 mm. The computational and experimental results will bo compared. (author). 7 refs., 8 figs., 1 tab.

Properties of a tunnel point contact between aluminum and the superconducting amorphous alloy NiZr2

International Nuclear Information System (INIS)

Gantmakher, V.F.; Golubov, A.A.; Osherov, M.V.

1989-01-01

The I-V characteristics of a tunnel point contact between aluminum and an amorphous ribbon resembling NiZr 2 in composition differ qualitatively from those of ordinary tunnel junctions between a superconductor and a normal metal. It is demonstrated that the observed curve shapes cannot be explained by accounting solely for one-particle tunneling in conditions of the proximity effect. This is followed by a qualitative discussion of a model in which the current rise at the potential eV equal to the gap width Δ (T) is generated by two-particle electron tunneling through the intermediate state which is manifested as a Cooper pair on the Fermi-level in the thin superconducting layer produced in the aluminum by the proximity effect. The current flowing through the contact will cause a breakdown of superconductivity in the vicinity of the contact at voltages exceeding the gap width. Smallness of the junction plays a decisive role both in inducing superconductivity for eV Δ

Cryogenic safety of the superconducting ALPI accelerator at INFN-LNL

CERN Multimedia

CERN. Geneva

2016-01-01

The superconducting linac ALPI at INFN-LNL is composed of 20 identical cryostats housing, at a group of four (or two), 74 superconducting QWR type cavities: 58 resonators are made of copper with Nb sputtered on the internal surface and 16 are made of Nb bulk. In each cryostat is installed a 100 liter volume LHe reservoir feeding by gravity the QWR’s. The thermal shield around is cooled by GHe at 6 bar abs at 60-80 K. The linac ALPI is a post-accelerator which can receive heavy ions from either the 16 MV Tandem Van de Graaf or from the superconducting injector PIAVE. The latter is composed by an ECR source, two superconducting RFQ, and two cryostats each containg four superconducting bulk Nb QWR. The ALPI cryostats are cooled by a Helium refrigerator whose refrigerator capacity is 1200 W at 4.5 K and 3900 W additional at 60-80 K. PIAVE cryostats are cooled by a separate TCF50 helium refrigerator. The complex ALPI-PIAVE is installed in a semi-open removable concrete tunnel in the same building where the two h...

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

Superconductivity and spin gap in the zigzag-chain t-J model simulating a CuO double chain in Pr2Ba4Cu7O15-δ

International Nuclear Information System (INIS)

Sano, Kazuhiro; Ono, Yoshiaki

2007-01-01

Using the numerical diagonalization method, we examine the one-dimensional t 1 -t 2 -J 1 -J 2 model (zigzag-chain t-J model) which is an effective model for metallic CuO double chains in the super-conductor Pr 2 Ba 4 Cu 7 O 15-δ . Based on the Tomonaga-Luttinger liquid theory, we calculate the Luttinger liquid parameter K ρ as a function of the electron density n. It is found that superconductivity is realized in the parameter region, which is in accordance with experimental results. We show the phase diagram of a spin gap in the t 2 /|t 1 |-n plane by analyzing the expectation value of the twist operator Z σ in the spin sector. The spin gap appears in the region with a large t 2 /|t 1 |, where the phase boundary at half filling is consistent with that of the known frustrated quantum spin system. The analysis also suggests that the estimated value of the spin gap reaches ∼100 K in the realistic parameter region of Pr 2 Ba 4 Cu 7 O 15-δ . (author)

Topological Superconductivity on the Surface of Fe-Based Superconductors.

Science.gov (United States)

Xu, Gang; Lian, Biao; Tang, Peizhe; Qi, Xiao-Liang; Zhang, Shou-Cheng

2016-07-22

As one of the simplest systems for realizing Majorana fermions, the topological superconductor plays an important role in both condensed matter physics and quantum computations. Based on ab initio calculations and the analysis of an effective 8-band model with superconducting pairing, we demonstrate that the three-dimensional extended s-wave Fe-based superconductors such as Fe_{1+y}Se_{0.5}Te_{0.5} have a metallic topologically nontrivial band structure, and exhibit a normal-topological-normal superconductivity phase transition on the (001) surface by tuning the bulk carrier doping level. In the topological superconductivity (TSC) phase, a Majorana zero mode is trapped at the end of a magnetic vortex line. We further show that the surface TSC phase only exists up to a certain bulk pairing gap, and there is a normal-topological phase transition driven by the temperature, which has not been discussed before. These results pave an effective way to realize the TSC and Majorana fermions in a large class of superconductors.

ISTS of Fe adatoms in contact to superconducting Ta

Energy Technology Data Exchange (ETDEWEB)

Kamlapure, Anand; Cornils, Lasse; Wiebe, Jens; Wiesendanger, Roland [Department of Physics, Hamburg University, Hamburg (Germany); Zhou, Lihui [Department of Physics, Hamburg University, Hamburg (Germany); Max-Planck Institute for Solid State-Research, Stuttgart (Germany); Khajetoorians, Alexander A. [Department of Physics, Hamburg University, Hamburg (Germany); Institute for Molecules and Materials, Radboud University, Nijmegen (Netherlands)

2015-07-01

Recent local scale investigations of the competition of superconductivity and magnetism in molecular systems revealed rich physics associated with a quantum phase transition. Here, we experimentally study individual Fe atoms adsorbed on a reconstructed surface of superconducting Ta by inelastic scanning tunneling spectroscopy (ISTS) at a temperature of 1 K and as a function of magnetic field of strength up to 3 T perpendicular to the surface. We observe strong inelastic excitations at three different adsorption sites of the Fe adatoms. The majority site shows a sharp step around 2 meV which is almost independent of the magnetic field. The other two sites exhibit excitations around 1 meV and 4 meV which have a weak magnetic field dependence indicating the magnetic origin of this excitation. In all three cases the superconducting energy gap and coherence peaks are preserved at zero magnetic field indicating very weak coupling between the magnetic moment and the cooper pairs.

LHC Abort Gap Cleaning with the Transverse Damper

CERN Document Server

Gianfelice-Wendt, E; Höfle, Wolfgang; Kain, V; Meddahi, M; Shaposhnikova, E; Koschik, A

2010-01-01

In the Large Hadron Collider, LHC, particles not captured by the RF system at injection or leaking out of the RF bucket may quench the superconducting magnets during beam abort. The problem, common to other superconducting machines, is particularly serious for the LHC due to the very large stored energy in the beam. For the LHC a way of removing the unbunched beam has been studied and it uses the existing damper kickers to excite resonantly the particles travelling along the abort gap. In this paper we describe the results of simulations performed with MAD X for various LHC optics configurations, including the estimated multipolar errors.

On the universality of the ''smile''-gap in the density of states of a chaotic Josephson junction

Energy Technology Data Exchange (ETDEWEB)

Reutlinger, Johannes; Belzig, Wolfgang [University of Konstanz, Department of Physics (Germany); Nazarov, Yuli [Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft (Netherlands); Glazman, Leonid [Department of Physics, Yale University, New Haven, CT (United States)

2015-07-01

The superconducting proximity effect strongly modifies the local density of states in chaotic Josephson junctions. Recently we found that besides the well-known minigap a secondary gap appears just below the superconducting gap edge Δ in the limit of a large Thouless energy E{sub Th} >or similar Δ. To check the universality of this novel gap phenomenon we study the effect of nonideal contacts and show that the ''smile''-gap crucially depends on the transmission eigenvalue distribution. In a next step we use the random matrix method to investigate the ''smile''-gap. This allows us to approach the statistics of Andreev levels, going beyond the quasiclassical Greens function method. It turns out that the hard gap edge softens similar to what is already known from the minigap.

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.

Proposal for the Purchase, Without a New Call for Tenders, of Four Additional Superconducting Quadrupole Magnets for the Duplication of the Low-Beta Insertion of the CERN Intersecting Storage Rings (ISR)

CERN Document Server

1978-01-01

Proposal for the Purchase, Without a New Call for Tenders, of Four Additional Superconducting Quadrupole Magnets for the Duplication of the Low-Beta Insertion of the CERN Intersecting Storage Rings (ISR)

Unconventional superconductivity of the heavy fermion compound UNi2Al3

International Nuclear Information System (INIS)

Zakharov, Andrey

2008-01-01

The heavy fermion compound UNi 2 Al 3 exhibits the coexistence of superconductivity and magnetic order at low temperatures, stimulating speculations about possible exotic Cooper-pairing interaction in this superconductor. However, the preparation of good quality bulk single crystals of UNi 2 Al 3 has proven to be a non-trivial task due to metallurgical problems, which result in the formation of an UAl 2 impurity phase and hence a strongly reduced sample purity. The present work concentrates on the preparation, characterization and electronic properties investigation of UNi 2 Al 3 single crystalline thin film samples. The preparation of thin films was accomplished in a molecular beam epitaxy (MBE) system. (100)-oriented epitaxial thin films of UNi 2 Al 3 were grown on single crystalline YAlO 3 substrates cut in (010)- or (112)-direction. The high crystallographic quality of the samples was proved by several characterisation methods, such as X-ray analysis, RHEED and TEM. To study the magnetic structure of epitaxial thin films resonant magnetic X-ray scattering was employed. The magnetic order of thin the film samples, the formation of magnetic domains with different moment directions, and the magnetic correlation length were discussed. The electronic properties of the UNi 2 Al 3 thin films in the normal and superconducting states were investigated by means of transport measurements. A pronounced anisotropy of the temperature dependent resistivity ρ(T) was observed. Moreover, it was found that the temperature of the resistive superconducting transition depends on the current direction, providing evidence for multiband superconductivity in UNi 2 Al 3 . The initial slope of the upper critical field H' c2 (T) of the thin film samples suggests an unconventional spin-singlet superconducting state, as opposed to bulk single crystal data. To probe the superconducting gap of UNi 2 Al 3 directly by means of tunnelling spectroscopy many planar junctions of different design

Neutron star cooling constraints for color superconductivity in hybrid stars

International Nuclear Information System (INIS)

Popov, S.; Grigoryan, Kh.; Blaschke, D.

2005-01-01

We apply the recently developed LogN-LogS test of compact star cooling theories for the first time to hybrid stars with a color superconducting quark matter core. While there is not yet a microscopically founded superconducting quark matter phase which would fulfill constraints from cooling phenomenology, we explore the hypothetical 2SC+X phase and show that the magnitude and density-dependence of the X-gap can be chosen to satisfy a set of tests: temperature-age (T-t), the brightness constraint, LogN-LogS, and the mass spectrum constraint. The latter test appears as a new conjecture from the present investigation

Interdigitation of long-chain sphingomyelin induces coupling of membrane leaflets in a cholesterol dependent manner

DEFF Research Database (Denmark)

Róg, Tomasz; Orłowski, Adam; Llorente, Alicia

2016-01-01

It has been a long-standing question how the two leaflets in a lipid bilayer modulate each others' physical properties. In this paper, we discuss how this interaction may take place through interdigitation. We use atomistic molecular dynamics simulations to consider asymmetric lipid membrane mode...

Energy Gap, Microwave-Assisted Tunneling, and Josephson Steps in Thin-Film Weak Links at 63 and 302 GHz

DEFF Research Database (Denmark)

Kofoed, Bent; Særmark, Knud

1973-01-01

We present experimental evidence for the occurrence of energy-gap structure and microwave-assisted tunneling in the IV curves for superconducting thin-film weak links. From measurements of the power and the temperature dependence of the Josephson steps we argue that also the Riedel peak is observ......We present experimental evidence for the occurrence of energy-gap structure and microwave-assisted tunneling in the IV curves for superconducting thin-film weak links. From measurements of the power and the temperature dependence of the Josephson steps we argue that also the Riedel peak...

Design of a gap tunable flux qubit with FastHenry

Science.gov (United States)

Akhtar, Naheed; Zheng, Yarui; Nazir, Mudassar; Wu, Yulin; Deng, Hui; Zheng, Dongning; Zhu, Xiaobo

2016-12-01

In the preparations of superconducting qubits, circuit design is a vital process because the parameters and layout of the circuit not only determine the way we address the qubits, but also strongly affect the qubit coherence properties. One of the most important circuit parameters, which needs to be carefully designed, is the mutual inductance among different parts of a superconducting circuit. In this paper we demonstrate how to design a gap-tunable flux qubit by layout design and inductance extraction using a fast field solver FastHenry. The energy spectrum of the gap-tunable flux qubit shows that the measured parameters are close to the design values. Project supported by the National Natural Science Foundation of China (Grant Nos. 11374344, 11404386, and 91321208), the National Basic Research Program of China (Grant No. 2014CB921401), and the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDB07010300).

In-plane magnetic penetration depth of superconducting CaKFe4As4

Science.gov (United States)

Khasanov, Rustem; Meier, William R.; Wu, Yun; Mou, Daixiang; Bud'ko, Sergey L.; Eremin, Ilya; Luetkens, Hubertus; Kaminski, Adam; Canfield, Paul C.; Amato, Alex

2018-04-01

The temperature dependence of the in-plane magnetic penetration depth (λa b) in an extensively characterized sample of superconducting CaKFe4As4(Tc≃35 K ) was investigated using muon-spin rotation (μ SR ). A comparison of λab -2(T ) measured by μ SR with the one inferred from angle-resolved photoemission spectroscopy (ARPES) data confirms the presence of multiple gaps at the Fermi level. An agreement between μ SR and ARPES requires the presence of additional bands, which are not resolved by ARPES experiments. These bands are characterized by small superconducting gaps with an average zero-temperature value of Δ0=2.4 (2 ) meV . Our data suggest that in CaKFe4As4 the s± order parameter symmetry acquires a more sophisticated form by allowing a sign change not only between electron and hole pockets, but also within pockets of similar type.

Interplay of CDW, SDW and superconductivity in high-Tc cuprates

International Nuclear Information System (INIS)

Panda, S.K.; Rout, G.C.

2009-01-01

We present a model calculation of the interplay of the charge density wave (CDW), spin density wave (SDW) and superconductivity in high temperature superconductors. In low doping situation the long range antiferromagnetic order is destroyed to give rise to SDW state accompanied by a CDW state in the system due to doping. For suitable doping the superconductivity appears in the system. The CDW state may describe the pseudogap phenomenon which co-exists with the superconducting phase and extends to normal phase in high-T c systems. These three competiting interactions co-exist together. These three gap parameters are calculated from the model Hamiltonian and solved self-consistently. By varying their coupling constants their interplay are investigated. Finally density of states is calculated for the conduction band which displays the experimental conductance data of Ekino et al. [T. Ekino, Y. Sezaki, H. Fujji, Phys. Rev. B 60 (1999) 6916].

Two energy scales and two quasiparticle dynamics in the superconducting state of under-doped cuprates

Energy Technology Data Exchange (ETDEWEB)

Le Tacon, M.; Sacuto, A. [Paris-7 Univ., Lab. Mat riaux et Ph nom nes Quantiques (UMR 7162 CNRS), 75 (France); Laboratoire de Physique du Solide, ESPCI, 75 - Paris (France); Georges, A. [Centre de Physique Theorique, Ecole Polytechnique, 91 - Palaiseau (France); Kotliar, G. [Centre de Physique Theorique, Ecole Polytechnique, 91 - Palaiseau (France); Rutgers Univ., Serin Physics Lab. (United States); Gallais, Y. [Columbia Univ. New York, Dept. of Physics and Applied Physics, NY (United States); Colson, D.; Forget, A. [CEA Saclay, Service de Physique de l' Etat Condense, 91 - Gif-sur-Yvette (France)

2006-07-01

The superconducting state of under-doped cuprates is often described in terms of a single energy scale, associated with the maximum of the (d-wave) gap. Here, we report on electronic Raman scattering results, which show that the gap function in the under-doped regime is characterized by two energy scales, depending on doping in opposite manners. Their ratios to the maximum critical temperature are found to be universal in cuprates. Our experimental results also reveal two different quasiparticle dynamics in the under-doped superconducting state, associated with two regions of momentum space: nodal regions near the zeros of the gap and anti-nodal regions. While anti-nodal quasiparticles quickly loose coherence as doping is reduced, coherent nodal quasiparticles persist down to low doping levels. A theoretical analysis using a new sum-rule allows us to relate the low-frequency-dependence of the Raman response to the temperature-dependence of the superfluid density, both controlled by nodal excitations. (authors)

Micro-supercapacitors based on interdigital electrodes of reduced graphene oxide and carbon nanotube composites with ultrahigh power handling performance

Energy Technology Data Exchange (ETDEWEB)

Beidaghi, Majid; Wang, Chunlei [Department of Mechanical and Materials Engineering, Florida International University, 10555 W. Flagler St., EC 3463, FL 33174 (United States)

2012-11-07

A novel method for fabricating micro-patterned interdigitated electrodes based on reduced graphene oxide (rGO) and carbon nanotube (CNT) composites for ultra-high power handling micro-supercapacitor application is reported. The binder-free microelectrodes were developed by combining electrostatic spray deposition (ESD) and photolithography lift-off methods. Without typically used thermal or chemical reduction, GO sheets are readily reduced to rGO during the ESD deposition. Electrochemical measurements show that the in-plane interdigital design of the microelectrodes is effective in increasing accessibility of electrolyte ions in-between stacked rGO sheets through an electro-activation process. Addition of CNTs results in reduced restacking of rGO sheets and improved energy and power density. Cyclic voltammetry (CV) measurements show that the specific capacitance of the micro-supercapacitor based on rGO-CNT composites is 6.1 mF cm{sup -2} at 0.01 V s{sup -1}. At a very high scan rate of 50 V s{sup -1}, a specific capacitance of 2.8 mF cm{sup -2} (stack capacitance of 3.1 F cm{sup -3}) is recorded, which is an unprecedented performance for supercapacitors. The addition of CNT, electrolyte-accessible and binder-free microelectrodes, as well as an interdigitated in-plane design result in a high-frequency response of the micro-supercapacitors with resistive-capacitive time constants as low as 4.8 ms. These characteristics suggest that interdigitated rGO-CNT composite electrodes are promising for on-chip energy storage application with high power demands. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Development of 3D carbon nanotube interdigitated finger electrodes on polymer substrate for flexible capacitive sensor application

International Nuclear Information System (INIS)

Hu, Chih-Fan; Wang, Jhih-Yu; Fang, Weileun; Liu, Yu-Chia; Tsai, Ming-Han

2013-01-01

This study reports a novel approach to the implementation of 3D carbon nanotube (CNT) interdigitated finger electrodes on flexible polymer, and the detection of strain, bending curvature, tactile force and proximity distance are demonstrated. The merits of the presented CNT-based flexible sensor are as follows: (1) the silicon substrate is patterned to enable the formation of 3D vertically aligned CNTs on the substrate surface; (2) polymer molding on the silicon substrate with 3D CNTs is further employed to transfer the 3D CNTs to the flexible polymer substrate; (3) the CNT–polymer composite (∼70 μm in height) is employed to form interdigitated finger electrodes to increase the sensing area and initial capacitance; (4) other structures such as electrical routings, resistors and mechanical supporters are also available using the CNT–polymer composite. The preliminary fabrication results demonstrate a flexible capacitive sensor with 50 μm high CNT interdigitated electrodes on a poly-dimethylsiloxane substrate. The tests show that the typical capacitance change is several dozens of fF and the gauge factor is in the range of 3.44–4.88 for strain and bending curvature measurement; the sensitivity of the tactile sensor is 1.11% N −1 ; a proximity distance near 2 mm away from the sensor can be detected. (paper)

Probing the superconducting ground state of the rare-earth ternary boride superconductors R RuB2 (R = Lu,Y) using muon-spin rotation and relaxation

Science.gov (United States)

Barker, J. A. T.; Singh, R. P.; Hillier, A. D.; Paul, D. McK.

2018-03-01

The superconductivity in the rare-earth transition-metal ternary borides R RuB2 (where R =Lu and Y) has been investigated using muon-spin rotation and relaxation. Measurements made in zero field suggest that time-reversal symmetry is preserved upon entering the superconducting state in both materials; a small difference in depolarization is observed above and below the superconducting transition in both compounds, however, this has been attributed to quasistatic magnetic fluctuations. Transverse-field measurements of the flux-line lattice indicate that the superconductivity in both materials is fully gapped, with a conventional s -wave pairing symmetry and BCS-like magnitudes for the zero-temperature gap energies. The electronic properties of the charge carriers in the superconducting state have been calculated, with effective masses m*/me=9.8 ±0.1 and 15.0 ±0.1 in the Lu and Y compounds, respectively, with superconducting carrier densities ns=(2.73 ±0.04 ) ×1028m-3 and (2.17 ±0.02 ) ×1028m-3 . The materials have been classified according to the Uemura scheme for superconductivity, with values for Tc/TF of 1 /(414 ±6 ) and 1 /(304 ±3 ) , implying that the superconductivity may not be entirely conventional in nature.

MgB2 energy gap determination by scanning tunnelling spectroscopy

International Nuclear Information System (INIS)

Heitmann, T W; Bu, S D; Kim, D M; Choi, J H; Giencke, J; Eom, C B; Regan, K A; Rogado, N; Hayward, M A; He, T; Slusky, J S; Khalifah, P; Haas, M; Cava, R J; Larbalestier, D C; Rzchowski, M S

2004-01-01

We report scanning tunnelling spectroscopy (STS) measurements of the gap properties of both ceramic MgB 2 and c-axis oriented epitaxial MgB 2 thin films. Both show a temperature dependent zero bias conductance peak and evidence for two superconducting gaps. We report tunnelling spectroscopy of superconductor-insulator-superconductor (S-I-S) junctions formed in two ways in addition to normal metal-insulator-superconductor (N-I-S) junctions. We find a gap δ = 2.2-2.8 meV, with spectral features and temperature dependence that are consistent between S-I-S junction types. In addition, we observe evidence of a second, larger gap, δ 7.2 meV, consistent with a proposed two-band model

Probing spin-polarized edge state superconductivity by Andreev reflection in in-plane magnetic fields

Energy Technology Data Exchange (ETDEWEB)

Reinthaler, Rolf W.; Tkachov, Grigory; Hankiewicz, Ewelina M. [Faculty of Physics and Astrophysics, University of Wuerzburg, Wuerzburg (Germany)

2015-07-01

Finding signatures of unconventional superconductivity in Quantum Spin Hall systems is one of the challenges of solid state physics. Here we induce superconductivity in a 3D topological insulator thin film to cause the formation of helical edge states, which are protected against backscattering even in finite magnetic fields. Above a critical in-plane magnetic field, which is much smaller than the critical field of typical superconductors, the quasi-particle gap closes, giving rise to energy-dependent spin polarization. In this regime the spin-polarized edge state superconductivity can be detected by Andreev reflection. We propose measurement setups to experimentally observe the spin-dependent excess current and dI/dV characteristics.

One-Dimensional Contact Mode Interdigitated Center of Pressure Sensor (CMIPS)

Science.gov (United States)

Xu, Tian-Bing; Kang, Jinho; Park, Cheol; Harrison, Joycelyn S.; Guerreiro, Nelson M.; Hubbard, James E.

2009-01-01

A one dimensional contact mode interdigitated center of pressure sensor (CMIPS) has been developed. The experimental study demonstrated that the CMIPS has the capability to measure the overall pressure as well as the center of pressure in one dimension, simultaneously. A theoretical model for the CMIPS is established here based on the equivalent circuit of the configuration of the CMIPS as well as the material properties of the sensor. The experimental results match well with theoretical modeling predictions. A system mapped with two or more pieces of the CMIPS can be used to obtain information from the pressure distribution in multi-dimensions.

Superconductivity, Pairing Symmetry, and Disorder in the Doped Topological Insulator Sn_1-xIn_xTe for x >= 0.10.

Energy Technology Data Exchange (ETDEWEB)

Smylie, M. P.; Claus, H.; Kwok, W. -K.; Louden, E. R.; Eskildsen, M. R.; Sefat, A. S.; Zhong, R. D.; Schneeloch, J.; Gu, G. D.; Bokari, E.; Niraula, P. M.; Kayani, A.; Dewhurst, C. D.; Snezhko, A.; Welp, U.

2018-01-19

The temperature dependence of the London penetration depth Delta lambda(T) in the superconducting doped topological crystalline insulator Sn1-xInxTe was measured down to 450 mK for two different doping levels, x approximate to 0.45 (optimally doped) and x approximate to 0.10 (underdoped), bookending the range of cubic phase in the compound. The results indicate no deviation from fully gapped BCS-like behavior, eliminating several candidate unconventional gap structures. Critical field values below 1 K and other superconducting parameters are also presented. The introduction of disorder by repeated particle irradiation with 5 MeV protons does not enhance T-c, indicating that ferroelectric interactions do not compete with superconductivity.

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

The T-J model and superconductivity | Umo | Global Journal of Pure ...

African Journals Online (AJOL)

The t-J model written in terms of Hubbard operators is studied with a view to contributing to the search for the mechanism of high temperature superconductivity in the cuprates. The method of irreducible Green function is used to obtain the spectrum of quasiparticles excitation and d-wave pairing gap function.

Influence of Superconductivity on Crystal Electric Field Transitions in La1-xTbxAl2

DEFF Research Database (Denmark)

Feile, R.; Loewenhaupt, M.; Kjems, Jørgen

1981-01-01

Inelastic neutron scattering from the crystal electric field transitions in La1-xTbxAl2 single crystals has revealed an abrupt increase in the lifetimes of these transitions when the system becomes superconducting. An increase in the integrated intensities is also observed. The lifetime effects...... are quantitatively reproduced by existing theories, which take into account the reduced scattering of the conduction electrons by the magnetic ions due to the creation of the superconducting energy gap 2Δ(T)....

SCMAG series of programs for calculating superconducting dipole and quadrupole magnets

International Nuclear Information System (INIS)

Green, M.A.

1974-01-01

A general description is given of four computer programs for calculating the characteristics of superconducting magnets used in the bending and focusing of high-energy particle beams. The programs are being used in the design of magnets for the LBL ESCAR (Experimental Superconducting Accelerator Ring) accelerator. (U.S.)

Dynamics and tolerances for the CERN interdigital H LINAC

International Nuclear Information System (INIS)

Valero, S.; Ratzinger, U.

1992-01-01

A three tank interdigital H structure has been chosen for the 0.25 to 4.2 MeV/u part of the CERN heavy-ion injector linac. The complete design has been developed by GSI, in particular the longitudinal dimensions have been determined and multi-particle studies have been made using the program LORAS. Some RF tolerance studies have also be made at CERN using this program. For more general approach to the dynamics, the program DYNAC is being used at CERN especially where statistical analyses are essential i.e for determining emittance growth, tolerances on accelerator parameters and alignment. The approaches and results of these two programs are compared for this novel type of accelerator

Suppression of superconductivity in a single Pb layer on Ag/Si(111)

Energy Technology Data Exchange (ETDEWEB)

Leon-Vanegas, Augusto; Kirschner, Juergen [Max Plank Instituet fuer Mikrostukturphysik (Germany); Martin Luther Univeristaet, Halle-Wittenberg (Germany); Caminale, Michael; Stepniak, Agnieszka; Oka, Hirofumi; Sanna, Antonio; Linscheid, Andreas; Sander, Dirk [Max Plank Instituet fuer Mikrostukturphysik (Germany)

2015-07-01

Recently, superconductivity was reported in a single layer of Pb on Si(111) with a critical temperature of 1.83 K. It has been proposed that the interaction of Pb with the Si substrate provides the electron phonon coupling to support superconductivity in this system. We have used a {sup 3}He-cooled STM with a vector magnetic field to study the effect of insertion of a Ag interlayer on the superconducting properties of a single Pb layer on Si(111). In contrast to the experiments on Pb/Si(111), the differential conductance of Pb/Ag/Si(111) does not show a gap indicative of superconductivity even at the lowest experimental temperature of 0.38 K. We ascribe this to the suppression of superconductivity. This result is explained by means of ab-initio calculations, showing that the effect of a chemical hybridization between Pb and Ag/Si occurring at the Fermi level dramatically reduces the strength of the electron phonon coupling. This contrasts with the case of Pb/Si(111), where no overlap between Pb and Si electronic states at the Fermi level is found in the calculations.

Large enhancement of thermoelectric effects in a tunneling-coupled parallel DQD-AB ring attached to one normal and one superconducting lead

Science.gov (United States)

Yao, Hui; Zhang, Chao; Li, Zhi-Jian; Nie, Yi-Hang; Niu, Peng-bin

2018-05-01

We theoretically investigate the thermoelectric properties in a tunneling-coupled parallel DQD-AB ring attached to one normal and one superconducting lead. The role of the intrinsic and extrinsic parameters in improving thermoelectric properties is discussed. The peak value of figure of merit near gap edges increases with the asymmetry parameter decreasing, particularly, when asymmetry parameter is less than 0.5, the figure of merit near gap edges rapidly rises. When the interdot coupling strengh is less than the superconducting gap the thermopower spectrum presents a single-platform structure. While when the interdot coupling strengh is larger than the gap, a double-platform structure appears in thermopower spectrum. Outside the gap the peak values of figure of merit might reach the order of 102. On the basis of optimizing internal parameters the thermoelectric conversion efficiency of the device can be further improved by appropriately matching the total magnetic flux and the flux difference between two subrings.

3D Magnetic field modeling of a new superconducting synchronous machine using reluctance network method

Science.gov (United States)

Kelouaz, Moussa; Ouazir, Youcef; Hadjout, Larbi; Mezani, Smail; Lubin, Thiery; Berger, Kévin; Lévêque, Jean

2018-05-01

In this paper a new superconducting inductor topology intended for synchronous machine is presented. The studied machine has a standard 3-phase armature and a new kind of 2-poles inductor (claw-pole structure) excited by two coaxial superconducting coils. The air-gap spatial variation of the radial flux density is obtained by inserting a superconducting bulk, which deviates the magnetic field due to the coils. The complex geometry of this inductor usually needs 3D finite elements (FEM) for its analysis. However, to avoid a long computational time inherent to 3D FEM, we propose in this work an alternative modeling, which uses a 3D meshed reluctance network. The results obtained with the developed model are compared to 3D FEM computations as well as to measurements carried out on a laboratory prototype. Finally, a 3D FEM study of the shielding properties of the superconducting screen demonstrates the suitability of using a diamagnetic-like model of the superconducting screen.

Critical current enhancement driven by suppression of superconducting fluctuation in ion-gated ultrathin FeSe

Science.gov (United States)

Harada, T.; Shiogai, J.; Miyakawa, T.; Nojima, T.; Tsukazaki, A.

2018-05-01

The framework of phase transition, such as superconducting transition, occasionally depends on the dimensionality of materials. Superconductivity is often weakened in the experimental conditions of two-dimensional thin films due to the fragile superconducting state against defects and interfacial effects. In contrast to this general trend, superconductivity in the thin limit of FeSe exhibits an opposite trend, such as an increase in critical temperature (T c) and the superconducting gap exceeding the bulk values; however, the dominant mechanism is still under debate. Here, we measured thickness-dependent electrical transport properties of the ion-gated FeSe thin films to evaluate the superconducting critical current (I c) in the ultrathin FeSe. Upon systematically decreasing the FeSe thickness by the electrochemical etching technique in the Hall bar-shaped electric double-layer transistors, we observed a dramatic enhancement of I c reaching about 10 mA and corresponding to about 107 A cm‑2 in the thinnest condition. By analyzing the transition behavior, we clarify that the suppressed superconducting fluctuation is one of the origins of the large I c in the ion-gated ultrathin FeSe films. These results indicate the existence of a robust superconducting state possibly with dense Cooper pairs at the thin limit of FeSe.

101Ru NQR study in superconducting CeRu2

International Nuclear Information System (INIS)

Matsuda, Kazuyuki; Kohori, Yoh; Kohara, Takao

1995-01-01

We present measurements of the NQR spectrum and the nuclear spin lattice relaxation rate, 1/T 1 , of 101 Ru in superconducting CeRu 2 from 1.9 K to 10 K. From the NQR spectrum, the electric quadrupole interaction parameters were determined to be ν Q =13.2 MHz and η=0.1/T 1 varies in proportion to temperature in the normal state, and has the Hebel-Slichter coherence peak just below the superconducting transition temperature, T C , of 6.2 K, and decreases exponentially at low temperatures with the energy gap of 2Δ=4.0k B T C . 101 Ru NQR study indicates that CeRu 2 is an s-wave and strong-coupling superconductor. (author)

Probing Andreev bound states in one-atom superconducting contacts

Energy Technology Data Exchange (ETDEWEB)

Pothier, Hugues; Janvier, Camille; Tosi, Leandro; Girit, Caglar; Goffman, Marcelo; Esteve, Daniel; Urbina, Cristian [Quantronics Group, SPEC, CEA-Saclay (France)

2015-07-01

Superconductors are characterized by a dissipationless current. Since the work of Josephson 50 years ago, it is known that a supercurrent can even flow through tunnel junctions between superconductors. This Josephson effect also occurs through any type of ''weak links'' between superconductors: non-superconducting materials, constrictions,.. A unified understanding of the Josephson effect has emerged from a mesoscopic description of weak links. It relies on the existence of doublets of localized states that have energies below the superconducting gap: the Andreev bound states. I will present experiments performed on the simplest conductor possible, a single-atom contact between superconductors, that illustrate these concepts. The most recent work demonstrates time-domain manipulation of quantum superpositions of Andreev bound states.

Microwave superconductivity for particle accelerators - How the high TC superconductors measure up

International Nuclear Information System (INIS)

Padamsee, H.; Green, K.; Gruschus, J.

1988-01-01

Application of superconducting niobium cavities to accelerators for high energy physics, nuclear physics and free electron laser is growing rapidly. Cornell has a long standing effort in the development of superconducting RF accelerator technology. Nb cavities developed here from the basis for constructing the world's highest energy electron accelerator for nuclear physics. These cavities have set a standard against which the behavior of the new superconductors must be compared. From available results on dc critical fields, and the energy gap, it appears that the new materials could make a significant impact on the capabilities of future accelerators. Crucial to this assessment, however, are direct microwave loss measurements, together with measurements of the energy gap and RF frequency dependence as well as the behavior at high RF fields. Latest results on these properties for bulk sintered ceramics, thin films and single crystals at RF frequencies of 1.5 and 6 Ghz are presented

Doping dependence of low-energy quasiparticle excitations in superconducting Bi2212.

Science.gov (United States)

Ino, Akihiro; Anzai, Hiroaki; Arita, Masashi; Namatame, Hirofumi; Taniguchi, Masaki; Ishikado, Motoyuki; Fujita, Kazuhiro; Ishida, Shigeyuki; Uchida, Shinichi

2013-12-05

: The doping-dependent evolution of the d-wave superconducting state is studied from the perspective of the angle-resolved photoemission spectra of a high-Tc cuprate, Bi2Sr2CaCu2 O8+δ (Bi2212). The anisotropic evolution of the energy gap for Bogoliubov quasiparticles is parametrized by critical temperature and superfluid density. The renormalization of nodal quasiparticles is evaluated in terms of mass enhancement spectra. These quantities shed light on the strong coupling nature of electron pairing and the impact of forward elastic or inelastic scatterings. We suggest that the quasiparticle excitations in the superconducting cuprates are profoundly affected by doping-dependent screening.

Interplay of superconductivity and magnetism in presence of inter sub-lattice effect in cuprates

International Nuclear Information System (INIS)

Bishoyi, K.C.; Mohapatra, S.P.; Rout, G.C.

2010-01-01

In the present communication, we report a model Hamiltonian to study the interplay between the two long range orders of anti-ferromagnetism (AFM) and superconductivity (SC) in cuprate superconductors in presence of the intersite pairing effect. The BCS type but non-phonon pairing mechanism is considered among the electrons of two equivalent Cu sites. The pairing among the electrons of two nearest neighbour non-equivalent Cu sites is included in the Hamiltonian and its effect on the interplay of SC and AFM is investigated. The Hamiltonian is solved by the Green's function method and the corresponding gap equations are calculated and solved self-consistently. The influence of model parameters like AFM coupling (λ), SC coupling (λ 1 ) and the coupling (λ 2 ) for intersite superconducting interactions on the gaps (SC and AFM) are studied numerically and the results are reported. (author)

THz spectroscopy on superconducting NbN thin films

Energy Technology Data Exchange (ETDEWEB)

Daschke, Lena; Pracht, Uwe S.; Dressel, Martin; Scheffler, Marc [1. Physikalisches Institut, Universitaet Stuttgart (Germany); Ilin, Konstantin S.; Siegel, Michael [Institut fuer Mikro- und Nanoelektronische Systeme, Karlsruher Institut fuer Technologie (Germany)

2015-07-01

Epitaxial thin-film niobium nitride (NbN) is a conventional BCS superconductor. In presence of strong disorder, however, electronic inhomogeneities appear, which is not fully understood yet. To obtain a better insight into the physics of such disordered materials, studies on model systems such as structurally tailored films might be useful. Furthermore, disordered NbN films are used for single-photon detection devices, whose proper performance depends on a profound understanding of the superconducting properties. The studied NbN films have a T{sub c} ranging from 10 to 15 K and the superconducting energy gap is easily accessible with THz spectroscopy (0.4 - 5.6 meV). We investigate thin films of NbN sputtered on a sapphire substrate. With a Mach-Zehnder interferometer we measure the amplitude and phase shift of radiation transmitted through the thin-film sample. From there we can determine the real and imaginary parts of the optical conductivity. These results give information about the energy gap, Cooper pair density, and quasiparticle dynamics, including the temperature evolution of these quantities. We found that a film with 10 nm thickness roughly follows the BCS behavior, as expected. We will present results of our measurements on several different NbN samples.

Scattering theory of superconductive tunneling in quantum junctions

International Nuclear Information System (INIS)

Shumeiko, V.S.; Bratus', E.N.

1997-01-01

A consistent theory of superconductive tunneling in single-mode junctions within a scattering formulation of Bogolyubov-de Gennes quantum mechanics is presented. The dc Josephson effect and dc quasiparticle transport in the voltage-biased junctions are considered. Elastic quasiparticle scattering by the junction determines the equilibrium Josephson current. The origin of Andreev bound states in tunnel junctions and their role in equilibrium Josephson transport are discussed. In contrast, quasiparticle tunneling in voltage-biased junctions is determined by inelastic scattering. A general expression for inelastic scattering amplitudes is derived and the quasiparticle current is calculated at all voltages with emphasis on a discussion of the properties of sub gap tunnel current and the nature of subharmonic gap structure

High power density superconducting motor for control applications

International Nuclear Information System (INIS)

Lopez, J; Granados, X; Lloberas, J; Torres, R; Grau, J; Maynou, R; Bosch, R

2008-01-01

A high dynamics superconducting low power motor for control applications has been considered for design. The rotor is cylindrical with machined bulks that generate the field by trapping flux in a four poles configuration. The toothless iron armature is wound by copper, acting iron only as magnetic screen. Details of the magnetic assembling, cryogenics and electrical supply conditioning will be reported. Improvements due to the use of a superconducting set are compared with performances of equivalent conventional motors

Effect of boron dimers on the superconducting critical temperature inboron-doped diamond

Czech Academy of Sciences Publication Activity Database

Šopík, Břetislav; Lipavský, P.

2012-01-01

Roč. 21, č. 1 (2012), 77-82 ISSN 0925-9635 R&D Projects: GA ČR GAP204/10/0212 Institutional research plan: CEZ:AV0Z10100521 Keywords : boron * superconductivity * disorder * correlations * dimers Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.709, year: 2012

Superconducting quantum interference monitor of charged particle beam current

International Nuclear Information System (INIS)

Gertsev, K.F.; Mikheev, M.S.

1981-01-01

Description and test results of the monitor of charged particle beam current on the base of the high-frequency superconducting quantum interference detector with lead slotted shield are presented. The toroidal superconducting coil, which covers the measured beam has 16 turns wound by the lead belt of 7 mm width with 0.5 mm gaps between the turns. A superconducting low-coupling monitor having two holes and point oxidated niobium contact has been used in the mode of quanta counting of magnetic flux. The lead point shield was 2 mm thick and it had 30 mm aperture. The coefficient of background shielding within 0-200 Hz frequency range constituted more than 10 8 . The threshold current resolution of the monitor had the value less than 01 μA √Hz. The suggested monitor requires helium cooling. The proposed design of the monitor is applicable for mounting on the vacuum chamber when it is surrounded by helium conductor. In other cases mounting of low-powerful autonomic system or cryostat of helium storage up to several weeks is possible [ru

Two-dimensional macroscopic quantum tunneling in multi-gap superconductor Josephson junctions

International Nuclear Information System (INIS)

Asai, Hidehiro; Kawabata, Shiro; Ota, Yukihiro; Machida, Masahiko

2014-01-01

Low-temperature characters of superconducting devices yield definite probes for different superconducting phenomena. We study the macroscopic quantum tunneling (MQT) in a Josephson junction, composed of a single-gap superconductor and a two-gap superconductor. Since this junction has two kinds to the superconducting phase differences, calculating the MQT escape rate requires the analysis of quantum tunneling in a multi-dimensional configuration space. Our approach is the semi-classical approximation along a 1D curve in a 2D potential- energy landscape, connecting two adjacent potential (local) minimums through a saddle point. We find that this system has two plausible tunneling paths; an in-phase path and an out-of-phase path. The former is characterized by the Josephson-plasma frequency, whereas the latter is by the frequency of the characteristic collective mode in a two-band superconductor, Josephson- Leggett mode. Depending on external bias current and inter-band Josephson-coupling energy, one of them mainly contributes to the MQT. Our numerical calculations show that the difference between the in-phase path and the out-of-phase path is manifest, with respect to the bias- current-dependence of the MQT escape rate. This result suggests that our MQT setting be an indicator of the Josephson-Leggett mode

Behaviour of superconductivity energetic characteristics in electron-doped cuprates. A simple model

International Nuclear Information System (INIS)

Kristoffel, N.; Rubin, P.

2008-01-01

A simple model to describe the energetic phase diagram of electron-doped cuprate superconductor is developed. Interband pairing operates between the UHB and the defect states created by doping and supplied by both extincting HB-s. Two defect subbands correspond to the (π,0) and (π/2,π/2) momentum regions. Extended doping quenches the bare normal state gaps (pseudogaps). Maximal transition temperature corresponds to overlapping bands ensemble intersected by the chemical potential. Illustrative results for T c , pseudo- and superconducting gaps are calculated on the whole doping scale. Major characteristic features on the phase diagram are reproduced. Anticipated manifestation of gaps doping dynamics is discussed

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}.

Multi-frequency modes in superconducting resonators: Bridging frequency gaps in off-resonant couplings

Science.gov (United States)

Andersen, Christian Kraglund; Mølmer, Klaus

2015-03-01

A SQUID inserted in a superconducting waveguide resonator imposes current and voltage boundary conditions that makes it suitable as a tuning element for the resonator modes. If such a SQUID element is subject to a periodically varying magnetic flux, the resonator modes acquire frequency side bands. We calculate the multi-frequency eigenmodes and these can couple resonantly to physical systems with different transition frequencies and this makes the resonator an efficient quantum bus for state transfer and coherent quantum operations in hybrid quantum systems. As an example of the application, we determine their coupling to transmon qubits with different frequencies and we present a bi-chromatic scheme for entanglement and gate operations. In this calculation, we obtain a maximally entangled state with a fidelity F = 95 % . Our proposal is competitive with the achievements of other entanglement-gates with superconducting devices and it may offer some advantages: (i) There is no need for additional control lines and dephasing associated with the conventional frequency tuning of qubits. (ii) When our qubits are idle, they are far detuned with respect to each other and to the resonator, and hence they are immune to cross talk and Purcell-enhanced decay.

Superconducting coil and method of stress management in a superconducting coil

Science.gov (United States)

McIntyre, Peter M.; Shen, Weijun; Diaczenko, Nick; Gross, Dan A.

1999-01-01

A superconducting coil (12) having a plurality of superconducting layers (18) is provided. Each superconducting layer (18) may have at least one superconducting element (20) which produces an operational load. An outer support structure (24) may be disposed outwardly from the plurality of layers (18). A load transfer system (22) may be coupled between at least one of the superconducting elements (20) and the outer support structure (24). The load transfer system (22) may include a support matrix structure (30) operable to transfer the operational load from the superconducting element (20) directly to the outer support structure (24). A shear release layer (40) may be disposed, in part, between the superconducting element (20) and the support matrix structure (30) for relieving a shear stress between the superconducting element (20) and the support matrix structure (30). A compliant layer (42) may also be disposed, in part, between the superconducting element (20) and the support matrix structure (30) for relieving a compressive stress on the superconducting element (20).

Low stoichiometry operation of a polymer electrolyte membrane fuel cell employing the interdigitated flow field design

DEFF Research Database (Denmark)

Berning, Torsten; Odgaard, Madeleine; Kær, Søren Knudsen

2011-01-01

Fuel cell operation on dry reactant gases under low stoichiometry conditions employing the interdigitated flow field is investigated using a multi-fluid model. It is assumed that the MEA contains a water uptake layer which facilitates water absorption to the membrane and hence prevents the anode...

Raman scattering spectra of superconducting Bi2Sr2CaCu2O8 single crystals

International Nuclear Information System (INIS)

Kirillov, D.; Bozovic, I.; Geballe, T.H.; Kapitulnik, A.; Mitzi, D.B.

1988-01-01

Raman spectra of Bi 2 Sr 2 CaCu 2 O 8 single crystals with superconducting phase-transition temperature of 90 K have been studied. The spectra contained phonon lines and electronic continuum. Phonon energies and polarization selection rules were measured. A gap in the electronic continuum spectrum was observed in a superconducting state. Noticeable similarity between Raman spectra of Bi 2 Sr 2 CaCu 2 O 8 and YBa 2 Cu 3 O 7 was found

Raman scattering spectra of superconducting Bi2Sr2CaCu2O8 single crystals

Science.gov (United States)

Kirillov, D.; Bozovic, I.; Geballe, T. H.; Kapitulnik, A.; Mitzi, D. B.

1988-12-01

Raman spectra of Bi2Sr2CaCu2O8 single crystals with superconducting phase-transition temperature of 90 K have been studied. The spectra contained phonon lines and electronic continuum. Phonon energies and polarization selection rules were measured. A gap in the electronic continuum spectrum was observed in a superconducting state. Noticeable similarity between Raman spectra of Bi2Sr2CaCu2O8 and YBa2Cu3O7 was found.

Topological superconductivity in the extended Kitaev-Heisenberg model

Science.gov (United States)

Schmidt, Johann; Scherer, Daniel D.; Black-Schaffer, Annica M.

2018-01-01

We study superconducting pairing in the doped Kitaev-Heisenberg model by taking into account the recently proposed symmetric off-diagonal exchange Γ . By performing a mean-field analysis, we classify all possible superconducting phases in terms of symmetry, explicitly taking into account effects of spin-orbit coupling. Solving the resulting gap equations self-consistently, we map out a phase diagram that involves several topologically nontrivial states. For Γ breaking chiral phase with Chern number ±1 and a time-reversal symmetric nematic phase that breaks the rotational symmetry of the lattice. On the other hand, for Γ ≥0 we find a time-reversal symmetric phase that preserves all the lattice symmetries, thus yielding clearly distinguishable experimental signatures for all superconducting phases. Both of the time-reversal symmetric phases display a transition to a Z2 nontrivial phase at high doping levels. Finally, we also include a symmetry-allowed spin-orbit coupling kinetic energy and show that it destroys a tentative symmetry-protected topological order at lower doping levels. However, it can be used to tune the time-reversal symmetric phases into a Z2 nontrivial phase even at lower doping.

A new design of a miniature filter on microstrip resonators with an interdigital structure of conductors

Science.gov (United States)

Belyaev, B. A.; Serzhantov, A. M.; Bal'va, Ya. F.; Leksikov, An. A.; Galeev, R. G.

2015-05-01

A microstrip bandpass filter of new design based on original resonators with an interdigital structure of conductors has been studied. The proposed filters of third to sixth order are distinguished for their high frequency-selective properties and much smaller size than analogs. It is established that a broad stop band, extending up to a sixfold central bandpass frequency, is determined by low unloaded Q of higher resonance mode and weak coupling of resonators in the pass band. It is shown for the first time that, as the spacing of interdigital stripe conductors decreases, the Q of higher resonance mode monotonically drops, while the Q value for the first operating mode remains high. A prototype fourth-order filter with a central frequency of 0.9 GHz manufactured on a ceramic substrate with dielectric permittivity ɛ = 80 has microstrip topology dimensions of 9.5 × 4.6 × 1 mm3. The electrodynamic 3D model simulations of the filter characteristics agree well with the results of measurements.

Color superconductivity from the chiral quark-meson model

Science.gov (United States)

Sedrakian, Armen; Tripolt, Ralf-Arno; Wambach, Jochen

2018-05-01

We study the two-flavor color superconductivity of low-temperature quark matter in the vicinity of chiral phase transition in the quark-meson model where the interactions between quarks are generated by pion and sigma exchanges. Starting from the Nambu-Gorkov propagator in real-time formulation we obtain finite temperature (real axis) Eliashberg-type equations for the quark self-energies (gap functions) in terms of the in-medium spectral function of mesons. Exact numerical solutions of the coupled nonlinear integral equations for the real and imaginary parts of the gap function are obtained in the zero temperature limit using a model input spectral function. We find that these components of the gap display a complicated structure with the real part being strongly suppressed above 2Δ0, where Δ0 is its on-shell value. We find Δ0 ≃ 40MeV close to the chiral phase transition.

Dynamics and tolerances for the CERN Interdigital H linac

International Nuclear Information System (INIS)

Bylinsky, Y.; Ratzinger, U.; Valero, S.

1992-01-01

A three tank Interdigital H structure has been chosen for the 0.25 to 4.2 MeV/u part of the CERN heavy-ion injector linac. The complete design has been developed by GSI; in particular the longitudinal dimensions have been determined and multi-particle studies have been made using the program LORAS. Some RF tolerance studies have also been made at CERN using this program. For a more general approach to the dynamics, the program DYNAC is being used at CERN, especially where statistical analyses are essential; i.e. for determining emittance growth, tolerances on accelerator parameters and alignment. The approaches and results of these two programs are compared for this novel type of accelerator. (Author) 6 refs., 3 tabs., 3 figs

Superconducting correlations in the one-band Hubbard model with intermediate on-site and weak attractive intersite interactions

International Nuclear Information System (INIS)

Jain, K.P.; Ramakumar, R.; Chancey, C.C.

1990-01-01

In this paper, we analyze a simple extended Hubbard model with an intermediate on-site interaction (both repulsive and attractive) and a weak intersite attractive interaction. Following Hubbard decoupling approximations and introducing Hubbard subband operators, we obtain a generalized gap function for singlet s-wave pairing that explicitly depends on the Hubbard subband energies. For the on-site repulsive-interaction case, we find that the superconductivity is not destroyed in the intermediate-interaction regime, contrary to the prediction of a Hartree-Fock mean-field treatment. The essential consequence of the on-site repulsion is the formation of the Hubbard subbands separated by the Mott-Hubbard gap, and it is within these subbands that pairing induced by the intersite interaction occurs. For the attractive on-site interaction case, the on-site pairing amplitude is found to be proportional to the bandwidth, and the gap function has contributions from both on-site and intersite pairing. The relevance of the model to high-temperature superconductivity is discussed

Robustness of Topological Superconductivity in Solid State Hybrid Structures

Science.gov (United States)

Sitthison, Piyapong

The non-Abelian statistics of Majorana fermions (MFs) makes them an ideal platform for implementing topological quantum computation. In addition to the fascinating fundamental physics underlying the emergence of MFs, this potential for applications makes the study of these quasiparticles an extremely popular subject in condensed matter physics. The commonly called `Majorana fermions' are zero-energy bound states that emerge near boundaries and defects in topological superconducting phases, which can be engineered, for example, by proximity coupling strong spin-orbit coupling semiconductor nanowires and ordinary s-wave superconductors. The stability of these bound states is determined by the stability of the underlying topological superconducting phase. Hence, understanding their stability (which is critical for quantum computation), involves studying the robustness of the engineered topological superconductors. This work addresses this important problem in the context of two types of hybrid structures that have been proposed for realizing topological superconductivity: topological insulator - superconductor (TI-SC) and semiconductor - superconductor (SM-SC) nanostructures. In both structures, electrostatic effects due to applied external potentials and interface-induced potentials are significant. This work focuses on developing a theoretical framework for understanding these effects, to facilitate the optimization of the nanostructures studied in the laboratory. The approach presented in this thesis is based on describing the low-energy physics of the hybrid structure using effective tight-binding models that explicitly incorporate the proximity effects emerging at interfaces. Generically, as a result of the proximity coupling to the superconductor, an induced gap emerges in the semiconductor (topological insulator) sub-system. The strength of the proximity-induced gap is determined by the transparency of the interface and by the amplitude of the low- energy SM

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

Unlocking color and flavor in superconducting strange quark matter

International Nuclear Information System (INIS)

Alford, Mark; Berges, Juergen; Rajagopal, Krishna

1999-01-01

We explore the phase diagram of strongly interacting matter with massless u and d quarks as a function of the strange quark mass m s and the chemical potential μ for baryon number. Neglecting electromagnetism, we describe the different baryonic and quark matter phases at zero temperature. For quark matter, we support our model-independent arguments with a quantitative analysis of a model which uses a four-fermion interaction abstracted from single-gluon exchange. For any finite m s , at sufficiently large μ we find quark matter in a color-flavor-locked state which leaves a global vector-like SU(2) color+L+R symmetry unbroken. As a consequence, chiral symmetry is always broken in sufficiently dense quark matter. As the density is reduced, for sufficiently large m s we observe a first-order transition from the color-flavor-locked phase to color superconducting phase analogous to that in two-flavor QCD. At this unlocking transition chiral symmetry is restored. For realistic values of m s our analysis indicates that chiral symmetry breaking may be present for all densities down to those characteristic of baryonic matter. This supports the idea that quark matter and baryonic matter may be continuously connected in nature. We map the gaps at the quark Fermi surfaces in the high density color-flavor-locked phase onto gaps at the baryon Fermi surfaces at low densities

Anisotropic two-gap superconductivity and the absence of a Pauli paramagnetic limit in single-crystalline LaO0.5F0.5BiS2

Science.gov (United States)

Chan, Y. C.; Yip, K. Y.; Cheung, Y. W.; Chan, Y. T.; Niu, Q.; Kajitani, J.; Higashinaka, R.; Matsuda, T. D.; Yanase, Y.; Aoki, Y.; Lai, K. T.; Goh, Swee K.

2018-03-01

Ambient-pressure-grown LaO0.5F0.5BiS2 with a superconducting transition temperature Tc˜3 K possesses a highly anisotropic normal state. By a series of electrical resistivity measurements with a magnetic-field direction varying between the crystalline c axis and the a b plane, we present datasets displaying the temperature dependence of the out-of-plane upper critical field Hc2 ⊥(T ) , the in-plane upper critical field Hc2 ∥(T ) , as well as the angular dependence of Hc 2 at fixed temperatures for ambient-pressure-grown LaO0.5F0.5BiS2 single crystals. The anisotropy of the superconductivity, Hc2 ∥/Hc2 ⊥ , reaches ˜16 on approaching 0 K, but it decreases significantly near Tc. A pronounced upward curvature of Hc2 ∥(T ) is observed near Tc, which we analyze using a two-gap model. Moreover, Hc2 ∥(0 ) is found to exceed the Pauli paramagnetic limit, which can be understood by considering the strong spin-orbit coupling associated with Bi as well as the breaking of the local inversion symmetry at the electronically active BiS2 bilayers. Hence, LaO0.5F0.5BiS2 with a centrosymmetric lattice structure is a unique platform to explore the physics associated with local parity violation in the bulk crystal.

Possible multigap type-I superconductivity in the layered boride RuB2

Science.gov (United States)

Singh, Jaskaran; Jayaraj, Anooja; Srivastava, D.; Gayen, S.; Thamizhavel, A.; Singh, Yogesh

2018-02-01

The structure of the layered transition-metal borides A B2 (A =Os,Ru ) is built up by alternating T and B layers with the B layers forming a puckered honeycomb. Here we report superconducting properties of RuB2 with a Tc≈1.5 K using measurements of the magnetic susceptibility versus temperature T , magnetization M versus magnetic field H , resistivity versus T , and heat capacity versus T at various H . We observe a reduced heat capacity anomaly at Tc given by Δ C /γ Tc≈1.1 suggesting multigap superconductivity. Strong support for this is obtained by the successful fitting of the electronic specific heat data to a two-gap model with gap values Δ1/kBTc≈1.88 and Δ2/kBTc≈1.13 . Additionally, M versus H measurements reveal a behavior consistent with type-I superconductivity. This is confirmed by comparing the experimental critical field ≈122 Oe obtained from extrapolation to T =0 of the H -T phase diagram, with an estimate of the T =0 thermodynamic critical field ≈114 Oe. Additionally, the Ginzburg-Landau parameter was estimated to be κ ≈0.1 -0.66 . These results strongly suggest multigap type-I superconductivity in RuB2. We also calculate the band structure and obtain the Fermi surface for RuB2. The Fermi surface consists of one quasi-two-dimensional sheet and two concentric ellipsoidal sheets very similar to OsB2. An additional small fourth sheet is also found for RuB2. RuB2 could thus be an example of a multigap type-I superconductor.

Solutions of the Bogoliubov–de Gennes equation with position dependent Fermi-velocity and gap profiles

Energy Technology Data Exchange (ETDEWEB)

Presilla, M. [Dipartimento di Fisica e Geologia, Università degli Studi di Perugia, Via A. Pascoli, I-06123 Perugia (Italy); Panella, O., E-mail: orlando.panella@pg.infn.it [Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, Via A. Pascoli, I-06123 Perugia (Italy); Roy, P. [Physics and Applied Mathematics Unit, Indian Statistical Institute, Kolkata-700108 (India)

2017-02-19

It is shown that bound state solutions of the one dimensional Bogoliubov–de Gennes (BdG) equation may exist when the Fermi velocity becomes dependent on the space coordinate. The existence of bound states in continuum (BIC) like solutions has also been confirmed both in the normal phase as well as in the super-conducting phase. We also show that a combination of Fermi velocity and gap parameter step-like profiles provides scattering solutions with normal reflection and transmission. - Highlights: • Bound states of BdG equation via Fermi velocity modulation. • Existence of bound states in continuum in both the normal and the superconducting phase. • Scattering solutions and bound states within a combination of step-like Fermi velocity and gap profiles.

Superconductivity drives magnetism in δ -doped La2CuO4

Science.gov (United States)

Suter, A.; Logvenov, G.; Boris, A. V.; Baiutti, F.; Wrobel, F.; Howald, L.; Stilp, E.; Salman, Z.; Prokscha, T.; Keimer, B.

2018-04-01

Understanding the interplay between different orders in a solid is a key challenge in highly correlated electronic systems. In real systems this is even more difficult since disorder can have strong influence on the subtle balance between these orders and thus can obscure the interpretation of the observed physical properties. Here we present a study on δ -doped La2CuO4 (δ -LCON ) superlattices. By means of molecular beam epitaxy whole LaO2 layers were periodically replaced by SrO2 layers, providing a charge reservoir yet reducing the level of disorder typically present in doped cuprates to an absolute minimum. The induced superconductivity and its interplay with the antiferromagnetic order is studied by means of low-energy muon spin rotation. We find a quasi-two-dimensional superconducting state which couples to the antiferromagnetic order in a nontrivial way. Below the superconducting transition temperature, the magnetic volume fraction increases strongly. The reason could be a charge redistribution of the free carriers due to the opening of the superconducting gap which is possible due to the close proximity and low disorder between the different ordered regions.

Unconventional superconductivity of the heavy fermion compound UNi{sub 2}Al{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Zakharov, Andrey

2008-07-01

The heavy fermion compound UNi{sub 2}Al{sub 3} exhibits the coexistence of superconductivity and magnetic order at low temperatures, stimulating speculations about possible exotic Cooper-pairing interaction in this superconductor. However, the preparation of good quality bulk single crystals of UNi{sub 2}Al{sub 3} has proven to be a non-trivial task due to metallurgical problems, which result in the formation of an UAl{sub 2} impurity phase and hence a strongly reduced sample purity. The present work concentrates on the preparation, characterization and electronic properties investigation of UNi{sub 2}Al{sub 3} single crystalline thin film samples. The preparation of thin films was accomplished in a molecular beam epitaxy (MBE) system. (100)-oriented epitaxial thin films of UNi{sub 2}Al{sub 3} were grown on single crystalline YAlO{sub 3} substrates cut in (010)- or (112)-direction. The high crystallographic quality of the samples was proved by several characterisation methods, such as X-ray analysis, RHEED and TEM. To study the magnetic structure of epitaxial thin films resonant magnetic X-ray scattering was employed. The magnetic order of thin the film samples, the formation of magnetic domains with different moment directions, and the magnetic correlation length were discussed. The electronic properties of the UNi{sub 2}Al{sub 3} thin films in the normal and superconducting states were investigated by means of transport measurements. A pronounced anisotropy of the temperature dependent resistivity {rho}(T) was observed. Moreover, it was found that the temperature of the resistive superconducting transition depends on the current direction, providing evidence for multiband superconductivity in UNi{sub 2}Al{sub 3}. The initial slope of the upper critical field H'{sub c2}(T) of the thin film samples suggests an unconventional spin-singlet superconducting state, as opposed to bulk single crystal data. To probe the superconducting gap of UNi{sub 2}Al{sub 3

Numerical analysis of the stability of HTS power cable under fault current considering the gaps in the cable

International Nuclear Information System (INIS)

Fang, J.; Li, H.F.; Zhu, J.H.; Zhou, Z.N.; Li, Y.X.; Shen, Z.; Dong, D.L.; Yu, T.; Li, Z.M.; Qiu, M.

2013-01-01

Highlights: •The equivalent circuit equations and the heat balance equations were established. •The current distributions of the HTS cable under fault current were obtained. •The temperature curves of conductor layers under fault current were obtained. •The effect of the gap liquid nitrogen on the thermal characteristics was studied. -- Abstract: During the operation of a high temperature superconducting power cable in a real grid, the power cable can be impacted inevitably by large fault current. The study on current distribution and thermal characteristics in the cable under fault current is the foundation to analyze its stability. To analyze the operation situation of 110 kV/3 kA class superconducting cable under the fault current of 25 kA rms for 3 s, the equivalent circuit equations and heat balance equations were established. The current distribution curves and the temperature distribution curves were obtained. The liquid nitrogen which exists in the gaps of HTS cable was taken into consideration, the influence of gap liquid nitrogen on the thermal characteristics was investigated. The analysis results can be used to estimate the security and stability of the superconducting cable

Numerical analysis of the stability of HTS power cable under fault current considering the gaps in the cable

Energy Technology Data Exchange (ETDEWEB)

Fang, J., E-mail: fangseer@sina.com [School of Electrical Engineering, Beijing Jiaotong University, Beijing 100044 (China); Li, H.F. [School of Electrical Engineering, Beijing Jiaotong University, Beijing 100044 (China); Zhu, J.H.; Zhou, Z.N. [China Electric Power Research Institute, Beijing 100192 (China); Li, Y.X.; Shen, Z.; Dong, D.L.; Yu, T. [School of Electrical Engineering, Beijing Jiaotong University, Beijing 100044 (China); Li, Z.M.; Qiu, M. [China Electric Power Research Institute, Beijing 100192 (China)

2013-11-15

Highlights: •The equivalent circuit equations and the heat balance equations were established. •The current distributions of the HTS cable under fault current were obtained. •The temperature curves of conductor layers under fault current were obtained. •The effect of the gap liquid nitrogen on the thermal characteristics was studied. -- Abstract: During the operation of a high temperature superconducting power cable in a real grid, the power cable can be impacted inevitably by large fault current. The study on current distribution and thermal characteristics in the cable under fault current is the foundation to analyze its stability. To analyze the operation situation of 110 kV/3 kA class superconducting cable under the fault current of 25 kA{sub rms} for 3 s, the equivalent circuit equations and heat balance equations were established. The current distribution curves and the temperature distribution curves were obtained. The liquid nitrogen which exists in the gaps of HTS cable was taken into consideration, the influence of gap liquid nitrogen on the thermal characteristics was investigated. The analysis results can be used to estimate the security and stability of the superconducting cable.

Superconductivity

International Nuclear Information System (INIS)

Langone, J.

1989-01-01

This book explains the theoretical background of superconductivity. Includes discussion of electricity, material fabrication, maglev trains, the superconducting supercollider, and Japanese-US competition. The authors reports the latest discoveries

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

High-temperature superconductivity

International Nuclear Information System (INIS)

Ginzburg, V.L.

1987-07-01

After a short account of the history of experimental studies on superconductivity, the microscopic theory of superconductivity, the calculation of the control temperature and its possible maximum value are presented. An explanation of the mechanism of superconductivity in recently discovered superconducting metal oxide ceramics and the perspectives for the realization of new high-temperature superconducting materials are discussed. 56 refs, 2 figs, 3 tabs

Superconducting accelerator technology

International Nuclear Information System (INIS)

Grunder, H.A.; Hartline, B.K.

1986-01-01

Modern and future accelerators for high energy and nuclear physics rely increasingly on superconducting components to achieve the required magnetic fields and accelerating fields. This paper presents a practical overview of the phenomenon of superconductivity, and describes the design issues and solutions associated with superconducting magnets and superconducting rf acceleration structures. Further development and application of superconducting components promises increased accelerator performance at reduced electric power cost

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

Superconducting technology

International Nuclear Information System (INIS)

2010-01-01

Superconductivity has a long history of about 100 years. Over the past 50 years, progress in superconducting materials has been mainly in metallic superconductors, such as Nb, Nb-Ti and Nb 3 Sn, resulting in the creation of various application fields based on the superconducting technologies. High-T c superconductors, the first of which was discovered in 1986, have been changing the future vision of superconducting technology through the development of new application fields such as power cables. On basis of these trends, future prospects of superconductor technology up to 2040 are discussed. In this article from the viewpoints of material development and the applications of superconducting wires and electronic devices. (author)

Interplay of CDW, SDW and superconductivity in high-T{sub c} cuprates

Energy Technology Data Exchange (ETDEWEB)

Panda, S K [K.D. Science College, Pochilima, Hinjilicut 761 101, Ganjam, Orissa (India); Rout, G.C., E-mail: gcr@iopb.res.i [Condensed Matter Physics Group, Dept. of Applied Physics and Ballistics, F.M. University, Balasore 756 019, Orissa (India)

2009-07-01

We present a model calculation of the interplay of the charge density wave (CDW), spin density wave (SDW) and superconductivity in high temperature superconductors. In low doping situation the long range antiferromagnetic order is destroyed to give rise to SDW state accompanied by a CDW state in the system due to doping. For suitable doping the superconductivity appears in the system. The CDW state may describe the pseudogap phenomenon which co-exists with the superconducting phase and extends to normal phase in high-T{sub c} systems. These three competiting interactions co-exist together. These three gap parameters are calculated from the model Hamiltonian and solved self-consistently. By varying their coupling constants their interplay are investigated. Finally density of states is calculated for the conduction band which displays the experimental conductance data of Ekino et al. [T. Ekino, Y. Sezaki, H. Fujji, Phys. Rev. B 60 (1999) 6916].

Superconductivity pairing mechanism from cobalt impurity doping in FeSe: Spin (s±) or orbital (s++) fluctuation

Science.gov (United States)

Urata, T.; Tanabe, Y.; Huynh, K. K.; Yamakawa, Y.; Kontani, H.; Tanigaki, K.

2016-01-01

In high-superconducting transition temperature (Tc) iron-based superconductors, interband sign reversal (s±) and sign preserving (s++) s -wave superconducting states have been primarily discussed as the plausible superconducting mechanism. We study Co impurity scattering effects on the superconductivity in order to achieve an important clue on the pairing mechanism using single-crystal Fe1 -xCoxSe and depict a phase diagram of a FeSe system. Both superconductivity and structural transition/orbital order are suppressed by the Co replacement on the Fe sites and disappear above x = 0.036. These correlated suppressions represent a common background physics behind these physical phenomena in the multiband Fermi surfaces of FeSe. By comparing experimental data and theories so far proposed, the suppression of Tc against the residual resistivity is shown to be much weaker than that predicted in the case of general sign reversal and full gap s± models. The origin of the superconducting paring in FeSe is discussed in terms of its multiband electronic structure.

Superconducting heavy-ion linacs

International Nuclear Information System (INIS)

Bollinger, L.M.

1977-01-01

A summary is given of plans developed by four different groups for the construction of small superconducting linacs to boost the energy of heavy ions from existing tandem electrostatic accelerators. The projects considered are the linac under construction at Argonne and the design efforts at Karlsruhe, at Stanford, and by a Cal Tech-Stony Brook collaboration. The intended uses of the accelerator systems are stated. Beam dynamics of linacs formed of short independently-phased resonators are reviewed, and the implications for performance are discussed. The main parameters of the four linacs are compared, and a brief analysis of accelerating structures is given

Electron-tunneling observation of localized excited states in superconducting manganese-doped lead

International Nuclear Information System (INIS)

Tsang, J.; Ginsberg, D.M.

1980-01-01

We have made electron-tunneling measurements on a dilute, superconducting lead-manganese alloy. A well-defined structure was observed in the ac-conductance--voltage curves, indicating excited states within the BCS energy gap. These states were partially accounted for by Shiba theory when spin-dependent s-, p-, and d-wave scattering were included. The phase shifts used in doing that were the results of band calculations. The experimental data also show the existence of a broad background density of states in the energy gap, which cannot be accounted for by the theory

Observation of a common symmetry for the pseudogap and the superconducting order parameter near the surface of underdoped YBa2Cu3O6+x

International Nuclear Information System (INIS)

Koren, G.; Shkedy, L.; Polturak, E.

2004-01-01

Measurements of the angular dependence of conductance spectra in the a-b plane of underdoped YBa 2 Cu 3 O 6+x junctions are reported. At zero magnetic field the superconducting gap shows a vertical bar d+is vertical bar-like symmetry. Application of a magnetic field strongly suppresses this gap leaving only the pseudogap feature which also shows a vertical bar d+is vertical bar-like angular dependence. We thus observe the same symmetry for the superconducting gap and the pseudogap characterizing the YBCO electrodes near the interface with the barrier. An H c2 value of ∼5 T of the secondary (is) order parameter can also be deduced from our results

The large superconducting solenoids for the g-2 muon storage ring

International Nuclear Information System (INIS)

Bunce, G.; Cullen, J.; Danby, G.

1994-01-01

The g-2 muon storage ring at Brookhaven National Laboratory consists of four large superconducting solenoids. The two outer solenoids, which are 15.1 meters in diameter, share a common cryostat. The two inner solenoids, which are 13.4 meters in diameter, are in separate cryostats. The two 24 turn inner solenoids are operated at an opposite polarity from the two 24 turn outer solenoids. This generates a dipole field between the inner and outer solenoids. The flux between the solenoids is returned through a C shaped iron return yoke that also shapes the dipole field. The integrated field around the 14 meter diameter storage ring must be good to about 1 part in one million over the 90 mm dia. circular cross section where the muons are stored, averaged over the azimuth. When the four solenoids carry their 5300 A design current, the field in the 18 centimeter gap between the poles is 1.45 T. When the solenoid operates at its design current 5.5 MJ is stored between the poles. The solenoids were wound on site at Brookhaven National Laboratory. The cryostats were built around the solenoid windings which are indirectly cooled using two-phase helium

Mean-field approach to unconventional superconductivity

International Nuclear Information System (INIS)

Sacks, William; Mauger, Alain; Noat, Yves

2014-01-01

Highlights: • A model Hamiltonian for unconventional superconductivity (SC) is proposed. • The pseudogap (PG) state is described in terms of pair fluctuations. • SC coherence is restored by a new pair–pair interaction, which counteracts fluctuations. • Given the temperature dependence of the parameters, the SC to PG transition is examined. • The theory fits the ‘peak–dip–hump’ features of cuprate and pnictide excitation spectra. - Abstract: We propose a model that connects the quasiparticle spectral function of high-T c superconductors to the condensation energy. Given the evidence for pair correlations above T c , we consider a coarse-grain Hamiltonian of fluctuating pairs describing the incoherent pseudogap (PG) state, together with a novel pair–pair interaction term that restores long-range superconducting (SC) coherence below T c . A mean-field solution then leads to a self-consistent gap equation containing the new pair–pair coupling. The corresponding spectral function A(k,E) reveals the characteristic peak–dip–hump features of cuprates, now observed on iron pnictides (LiFeAs). The continuous transition from SC to PG states is discussed

Experimental investigation on streaming due to a gap between blanket modules in ITER

International Nuclear Information System (INIS)

Konno, Chikara; Maekawa, Fujio; Oyama, Yukio; Uno, Yoshitomo; Kasugai, Yoshimi; Maekawa, Hiroshi; Ikeda, Yujiro; Wada, Masayuki

2000-01-01

A gap streaming experiment was performed by using a D-T neutron source at FNS/JAERI as the ITER/EDA R and D Task T-218, in order to examine the streaming effects due to gap between shield blanket modules in ITER. The experiment had three phases. The first one defined neutron source characteristics (Source Characterization Experiment), the second (Experiment-l ) aimed at shield for welding part between shield blanket and back plate and the third (Experiment-2) focused on the influence that the gap between shield blanket modules would have on superconducting magnet. The effects of gap streaming were examined in detail experimentally. (author)

Possible mechanism to enhance spin-fluctuation-mediated superconductivity in two-dimensional organic conductor

Energy Technology Data Exchange (ETDEWEB)

Nonoyama, Yoshito; Maekawa, Yukiko; Kobayashi, Akito; Suzumura, Yoshikazu [Department of Physics, Nagoya University, Nagoya 464-8602 (Japan); Yamada, Jun-ichi [Department of Material Science, Graduate School of Material Science, University of Hyogo, Hyogo 678-1297 (Japan)], E-mail: nonoyama@slab.phys.nagoya-u.ac.jp

2008-10-15

Mechanisms of superconductivity in quasi-two-dimensional organic conductors have been investigated using an extended Hubbard model by using the transfer energies between BDA-TTP molecules for {beta}-(BDA-TTP){sub 2}I{sub 3} based on the X-ray experiment data and the extended Hueckel calculation. We obtain several mean-field solutions with charge orderings which may represent short-range orderings or low-energy fluctuations in the low-dimensional electronic system. In the pressure-temperature phase diagram, a charge ordered metal state almost degenerates with a normal metal state between an insulating phase with charge ordering and the normal metal phase. Using the random phase approximation (RPA) and the linearized gap equation, the transition temperature of the superconducting state is estimated for the charge-ordered metal state and the normal metal state. It is found that transition temperature of the superconductivity induced by spin fluctuations in the charge-ordered metal state is much higher than that of the normal metal state and that the superconductivity in the charge-ordered metal state is the gapless d-wave. This suggests that the short range charge ordering may also contribute to an enhancement of spin-fluctuation-mediated superconductivity. The difference in the superconducting states between {beta}-(BDA-TTP){sub 2}I{sub 3} and {beta}-(BDA-TTP){sub 2}SbF{sub 6} are briefly discussed.

Possible mechanism to enhance spin-fluctuation-mediated superconductivity in two-dimensional organic conductor

International Nuclear Information System (INIS)

Nonoyama, Yoshito; Maekawa, Yukiko; Kobayashi, Akito; Suzumura, Yoshikazu; Yamada, Jun-ichi

2008-01-01

Mechanisms of superconductivity in quasi-two-dimensional organic conductors have been investigated using an extended Hubbard model by using the transfer energies between BDA-TTP molecules for β-(BDA-TTP) 2 I 3 based on the X-ray experiment data and the extended Hueckel calculation. We obtain several mean-field solutions with charge orderings which may represent short-range orderings or low-energy fluctuations in the low-dimensional electronic system. In the pressure-temperature phase diagram, a charge ordered metal state almost degenerates with a normal metal state between an insulating phase with charge ordering and the normal metal phase. Using the random phase approximation (RPA) and the linearized gap equation, the transition temperature of the superconducting state is estimated for the charge-ordered metal state and the normal metal state. It is found that transition temperature of the superconductivity induced by spin fluctuations in the charge-ordered metal state is much higher than that of the normal metal state and that the superconductivity in the charge-ordered metal state is the gapless d-wave. This suggests that the short range charge ordering may also contribute to an enhancement of spin-fluctuation-mediated superconductivity. The difference in the superconducting states between β-(BDA-TTP) 2 I 3 and β-(BDA-TTP) 2 SbF 6 are briefly discussed.

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.

Electromechanical characteristics of discal piezoelectric transducers with spiral interdigitated electrodes

International Nuclear Information System (INIS)

Pan, Chengliang; Xiao, Guangjun; Feng, Zhihua; Liao, Wei-Hsin

2014-01-01

In this study, piezoceramic thin disks with spiral interdigitated electrodes on their surfaces are proposed to generate in-plane torsional vibrations. Electromechanical characteristics of the discal piezoelectric transducers are investigated. Working principles of the transducers are explained while their static deformations are formulated. Dynamic models are derived to analyze the in-plane torsional vibrations of the disks together with the radial vibrations. The corresponding electromechanical equivalent circuits are also obtained. With different boundary conditions and structural parameters, frequency responses of their electric admittances are calculated numerically. Resonant frequencies, mode shapes, and electromechanical coupling coefficients of the vibration modes are also extracted. Prototype transducers are fabricated and tested to validate the theoretical results. (paper)

Subharmonic energy-gap structure in superconducting weak links

DEFF Research Database (Denmark)

Flensberg, K.; Hansen, Jørn Bindslev; Octavio, M.

1988-01-01

We present corrected calculations of the subharmonic energy-gap structure using the model of Octavio, Tinkham, Blonder, and Klapwijk, which includes the effect of normal scattering in the weak link. We show that while the overall predictions of this model do not change qualitatively, the details...... of the predicted curves are different and in better agreement with experiment. We also present calculation of the current-voltage characteristics and of the excess currents for T=0, as the normal scattering parameter Z is varied. We also show how the calculation can be shortened using symmetry arguments...

Superconductivity

CERN Document Server

Ketterson, John B

2008-01-01

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

Design of a vertical wiggler with superconducting coils

International Nuclear Information System (INIS)

Huke, K.; Yamakawa, T.

1980-01-01

A vertical wiggler has been designed, which will be installed in the 2.5 GeV electron storage ring under construction at KEK-PF. The wiggler magnet with superconducting coils produces magnetic fields of 6 T and wiggles electron beams in a vertical plane. Synchrotron radiation generated by the wiggler has a critical wavelength of 0.5 Angstroem and has an electric field-vector in the vertical direction, which is very important for precise experiments in various fields of the material sciences. The wiggler consists of three pairs of superconducting coils, an iron magnetic shield, a beam pipe and a liquid helium cryogenic system and is contained in a vacuum vessel which can move up and down together with the wiggler. During the injection time, the vessel is pushed up, so that electron beams with a large spatial spread go through the lower part of the beam pipe, where the aperture of the beam pipe is large enough. After the beam size becomes small due to radiation damping, the vessel is pushed down so that the electron beams go through the narrow gap of the wiggler magnet. Using the iron magnetic shield with iron pole pieces, the ratio between the magnetic field in the gap and the maximum field on the superconductor coils is reduced to 1.1. (orig.)

Report on the achievements in fiscal 1999. Research and development on a basic technology to apply superconductivity (Research and development on a basic technology to apply superconductivity); 1999 nendo chodendo oyo kiban gijutsu kenkyu kaihatsu seika hokokusho. Chodendo oyo kiban gijutsu kenkyu kaihatsu

Energy Technology Data Exchange (ETDEWEB)

NONE

2000-05-01

The development of a basic technology to improve superconductivity characteristics has performed (1) studies on the high-temperature superconductivity mechanism, (2) studies on the critical current mechanism, and (3) search for materials. In Item (1), composition and temperature dependence were investigated by measuring superconductivity gap and change in the electron state of pseudo gap using photo-electron spectra and Raman scattering spectra. In Item (2), magnetic flux behavior in the vicinity of the irreversible line was investigated on magnetic flux dynamics of Bi2212 by measuring magnetic resistance and magnetization. High viscosity condition having strong magnetic flux liquid zone was discovered. In Item (3), Sr was used in place of Ba as the constituting element, and several new mercury-based superconductors were synthesized successfully by using the high pressure synthesizing method. In developing superconductive bulk materials and wire materials, elucidation was given on (1) an element technology for high magnetic power bulk materials, (2) an element technology for high critical temperature bulk materials, (3) a fundamental technology for manufacturing next generation wire materials, (4) a fundamental technology for manufacturing next generation large current conductors, and (5) growth mechanism in wire material crystals. Development of laminating and processing technologies for superconductive materials has worked on (1) a single crystal substrate technology, (2) a thin film lamination technology, (3) a standard bonding technology, (4) an advanced bonding technology, and (5) a thin film and bond evaluation technology. (NEDO)

Superconductivity optimization and phase formation kinetics study of internal-Sn Nb3Sn superconducting wires

International Nuclear Information System (INIS)

Zhang, Chaowu

2007-07-01

Superconductors Nb 3 Sn wires are one of the most applicable cryogenic superconducting materials and the best choice for high-field magnets exceeding 10 T. One of the most significant utilization is the ITER project which is regarded as the hope of future energy source. The high-Cu composite designs with smaller number of sub-element and non-reactive diffusion barrier, and the RRP (Restacked Rod Process) internal-Sn technology are usually applied for the wire manufacturing. Such designed and processed wires were supplied by MSA/Alstom and WST/NIN in this research. The systematic investigation on internal-Sn superconducting wires includes the optimization of heat treatment (HT) conditions, phase formation and its relation with superconductivity, microstructure analysis, and the phase formation kinetics. Because of the anfractuosity of the configuration design and metallurgical processing, the MF wires are not sufficient for studying a sole factor effect on superconductivity. Therefore, four sets of mono-element (ME) wires with different Sn ratios and different third-element addition were designed and fabricated in order to explore the relationship between phase formation and superconducting performances, particularly the A15 layer growth kinetics. Different characterization technic have been used (magnetization measurements, neutron diffraction and SEM/TEM/EDX analysis). The A15 layer thicknesses of various ME samples were measured and carried out linear and non-linear fits by means of two model equations. The results have clearly demonstrated that the phase formation kinetics of Nb 3 Sn solid-state reaction is in accordance with an n power relation and the n value is increased with the increase of HT temperature and the Sn ratio in the wire composite. (author)

Superconductivity revisited

CERN Document Server

Dougherty, Ralph

2013-01-01

While the macroscopic phenomenon of superconductivity is well known and in practical use worldwide in many industries, including MRIs in medical diagnostics, the current theoretical paradigm for superconductivity (BCS theory) suffers from a number of limitations, not the least of which is an adequate explanation of high temperature superconductivity. This book reviews the current theory and its limitations and suggests new ideas and approaches in addressing these issues. The central objective of the book is to develop a new, coherent, understandable theory of superconductivity directly based on molecular quantum mechanics.

High field superconducting magnets

Science.gov (United States)

Hait, Thomas P. (Inventor); Shirron, Peter J. (Inventor)

2011-01-01

A superconducting magnet includes an insulating layer disposed about the surface of a mandrel; a superconducting wire wound in adjacent turns about the mandrel to form the superconducting magnet, wherein the superconducting wire is in thermal communication with the mandrel, and the superconducting magnet has a field-to-current ratio equal to or greater than 1.1 Tesla per Ampere; a thermally conductive potting material configured to fill interstices between the adjacent turns, wherein the thermally conductive potting material and the superconducting wire provide a path for dissipation of heat; and a voltage limiting device disposed across each end of the superconducting wire, wherein the voltage limiting device is configured to prevent a voltage excursion across the superconducting wire during quench of the superconducting magnet.

Superconducting muon channel at J-PARC

International Nuclear Information System (INIS)

Shimomura, K.; Koda, A.; Strasser, P.; Kawamura, N.; Fujimori, H.; Makimura, S.; Higemoto, W.; Nakahara, K.; Ishida, K.; Nishiyama, K.; Nagamine, K.; Miyake, Y.

2009-01-01

The Muon Science Laboratory at the Materials and Life Science Facility is now under construction in Japan Proton Accelerator Research Complex (J-PARC), where four types of muon channels are planned to be installed. A conventional superconducting muon channel will be installed at the first stage, which can extract surface (positive) muons and decay positive/negative muons up to 120 MeV/c, and the expected muon yield is a few 10 6 /s at 60 MeV/c (for both positive and negative). This channel will be used for various kinds of experiments like muon catalyzed fusion, μSR and nondestructive elements analysis. The present status of the superconducting muon channel is briefly reported.

Electrical resistivity measurements in superconducting ceramics

International Nuclear Information System (INIS)

Muccillo, R.; Bressiani, A.H.A.; Muccillo, E.N.S.; Bressiani, J.C.

1988-01-01

Electrical resistivity measurements have been done in (Y, Ba, Cu, O) - and (Y, A1, Ba, Cu, O) - based superconducting ceramics. The sintered specimens were prepared by applying gold electrodes and winding on the non-metalized part with a copper strip to be immersed in liquid nitrogen for cooling. The resistivity measurements have been done by the four-probe method. A copper-constantan or chromel-alumel thermocouple inserted between the specimen and the copper cold finger has been used for the determination of the critical temperature T c . Details of the experimental set-up and resistivity versus temperature plots in the LNT-RT range for the superconducting ceramics are the major contributions of this communication. (author) [pt

Electrical resistivity measurements in superconducting ceramics

International Nuclear Information System (INIS)

Muccillo, R.; Bressiani, A.H.A.; Muccillo, E.N.S.; Bressian, J.C.

1988-01-01

Electrical resistivity measurements have been done in (Y,Ba,Cu,O)- and (Y,Al,Ba,Cu,O)-based superconducting ceramics. The sintered specimens were prepared by applying gold electrodes and winding on the non-metalized part with a copper strip to be immersed in liquid nitrogen for cooling. The resistivity measurements have been done by the four-probe method. A copper constantan or chromel-alumel thermocouple inserted between the specimen and the copper cold finger has been used for the determination of the critical temperature T c . Details of the experimental set-up and resistivity versus temperature plots in the LNT-RT range for the superconducting ceramics are the major contributions of this communication. (author) [pt

Evidence of a Nonequilibrium Distribution of Quasiparticles in the Microwave Response of a Superconducting Aluminum Resonator

NARCIS (Netherlands)

De Visser, P.J.; Goldie, D.J.; Diener, P.; Withington, S.; Baselmans, J.J.A.; Klapwijk, T.M.

2014-01-01

In a superconductor, absorption of photons with an energy below the superconducting gap leads to redistribution of quasiparticles over energy and thus induces a strong nonequilibrium quasiparticle energy distribution. We have measured the electrodynamic response, quality factor, and resonant

Metal-insulator transition and superconductivity in heavily boron-doped diamond and related materials

Energy Technology Data Exchange (ETDEWEB)

Achatz, Philipp

2009-05-15

During this PhD project, the metal-insulator transition and superconductivity of highly boron-doped single crystal diamond and related materials have been investigated. The critical boron concentration n{sub c} for the metal-insulator transition was found to be the same as for the normal-superconductor transition. All metallic samples have been found to be superconducting and we were able to link the occurence of superconductivity to the proximity to the metal-insulator transition. For this purpose, a scaling law approach based on low temperature transport was proposed. Furthermore, we tried to study the nature of the superconductivity in highly boron doped single crystal diamond. Raman spectroscopy measurements on the isotopically substituted series suggest that the feature occuring at low wavenumbers ({approx} 500 cm{sup -1}) is the A1g vibrational mode associated with boron dimers. Usual Hall effect measurements yielded a puzzling situation in metallic boron-doped diamond samples, leading to carrier concentrations up to a factor 10 higher than the boron concentration determined by secondary ion mass spectroscopy (SIMS). The low temperature transport follows the one expected for a granular metal or insulator, depending on the interplay of intergranular and intragranular (tunneling) conductance. The metal-insulator transition takes place at a critical conductance g{sub c}. The granularity also influences significantly the superconducting properties by introducing the superconducting gap {delta} in the grain and Josephson coupling J between superconducting grains. A peak in magnetoresistance is observed which can be explained by superconducting fluctuations and the granularity of the system. Additionally we studied the low temperature transport of boron-doped Si samples grown by gas immersion laser doping, some of which yielded a superconducting transition at very low temperatures. Furthermore, preliminary results on the LO-phonon-plasmon coupling are shown for the

Metal-insulator transition and superconductivity in heavily boron-doped diamond and related materials

International Nuclear Information System (INIS)

Achatz, Philipp

2009-01-01

During this PhD project, the metal-insulator transition and superconductivity of highly boron-doped single crystal diamond and related materials have been investigated. The critical boron concentration n c for the metal-insulator transition was found to be the same as for the normal-superconductor transition. All metallic samples have been found to be superconducting and we were able to link the occurence of superconductivity to the proximity to the metal-insulator transition. For this purpose, a scaling law approach based on low temperature transport was proposed. Furthermore, we tried to study the nature of the superconductivity in highly boron doped single crystal diamond. Raman spectroscopy measurements on the isotopically substituted series suggest that the feature occuring at low wavenumbers (∼ 500 cm -1 ) is the A1g vibrational mode associated with boron dimers. Usual Hall effect measurements yielded a puzzling situation in metallic boron-doped diamond samples, leading to carrier concentrations up to a factor 10 higher than the boron concentration determined by secondary ion mass spectroscopy (SIMS). The low temperature transport follows the one expected for a granular metal or insulator, depending on the interplay of intergranular and intragranular (tunneling) conductance. The metal-insulator transition takes place at a critical conductance g c . The granularity also influences significantly the superconducting properties by introducing the superconducting gap Δ in the grain and Josephson coupling J between superconducting grains. A peak in magnetoresistance is observed which can be explained by superconducting fluctuations and the granularity of the system. Additionally we studied the low temperature transport of boron-doped Si samples grown by gas immersion laser doping, some of which yielded a superconducting transition at very low temperatures. Furthermore, preliminary results on the LO-phonon-plasmon coupling are shown for the first time in aluminum

Lithographed Superconducting Resonator Development for Next-Generation Frequency Multiplexing Readout of Transition-Edge Sensors

Science.gov (United States)

Faramarzi, F.; De Haan, T.; Kusaka, A.; Lee, A.; Neuhauser, B.; Plambeck, R.; Raum, C.; Suzuki, A.; Westbrook, B.

2018-03-01

Ground-based cosmic microwave background (CMB) experiments are undergoing a period of exponential growth. Current experiments are observing with 1000-10,000 detectors, and the next-generation experiment (CMB stage 4) is proposing to deploy approximately 500,000 detectors. This order of magnitude increase in detector count will require a new approach for readout electronics. We have developed superconducting resonators for next-generation frequency-domain multiplexing (fMUX) readout architecture. Our goal is to reduce the physical size of resonators, such that resonators and detectors can eventually be integrated on a single wafer. To reduce the size of these resonators, we have designed spiral inductors and interdigitated capacitors that resonate around 10-100 MHz, an order of magnitude higher frequency compared to current fMUX readout systems. The higher frequency leads to a wider bandwidth and would enable higher multiplexing factor than the current ˜ 50 detectors per readout channel. We will report on the simulation, fabrication method, characterization technique, and measurement of quality factor of these resonators.

Far-infrared electrodynamics of thin superconducting NbN film in magnetic fields

Czech Academy of Sciences Publication Activity Database

Šindler, Michal; Tesař, Roman; Koláček, Jan; Szabó, P.; Samuely, P.; Hašková, V.; Kadlec, Christelle; Kadlec, Filip; Kužel, Petr

2014-01-01

Roč. 27, č. 5 (2014), 1-8 ISSN 0953-2048 R&D Projects: GA ČR(CZ) GAP204/11/0015; GA MŠk(CZ) LD14060 Institutional support: RVO:68378271 Keywords : superconductivity * thin films * scanning tunneling spectroscopy * time-domain terahertz spectroscopy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.325, year: 2014

Tuning of superconductivity by Ni substitution into noncentrosymmetric ThC o1 -xN ixC2

Science.gov (United States)

Grant, T. W.; Cigarroa, O. V.; Rosa, P. F. S.; Machado, A. J. S.; Fisk, Z.

2017-07-01

The recently discovered noncentrosymmetric superconductor ThCoC2 was observed to show unusual superconducting behavior with a critical temperature of Tc=2.65 K . Here we investigate the effect of nickel substitution on the superconducting state in ThC o1 -xN ixC2 . Magnetization, resistivity, and heat capacity measurements demonstrate Ni substitution has a dramatic effect with critical temperature increased up to Tc=12.1 K for x =0.4 Ni concentration, which is a rather high transition temperature for a noncentrosymmetric superconductor. In addition, the unusual superconducting characteristics observed in pure ThCoC2 appear to be suppressed or tuned with Ni substitution towards a more conventional fully gapped superconductor.

Exotic superconductivity with enhanced energy scales in materials with three band crossings

Science.gov (United States)

Lin, Yu-Ping; Nandkishore, Rahul M.

2018-04-01

Three band crossings can arise in three-dimensional quantum materials with certain space group symmetries. The low energy Hamiltonian supports spin one fermions and a flat band. We study the pairing problem in this setting. We write down a minimal BCS Hamiltonian and decompose it into spin-orbit coupled irreducible pairing channels. We then solve the resulting gap equations in channels with zero total angular momentum. We find that in the s-wave spin singlet channel (and also in an unusual d-wave `spin quintet' channel), superconductivity is enormously enhanced, with a possibility for the critical temperature to be linear in interaction strength. Meanwhile, in the p-wave spin triplet channel, the superconductivity exhibits features of conventional BCS theory due to the absence of flat band pairing. Three band crossings thus represent an exciting new platform for realizing exotic superconducting states with enhanced energy scales. We also discuss the effects of doping, nonzero temperature, and of retaining additional terms in the k .p expansion of the Hamiltonian.

Induced superconductivity in the topological insulator mercury telluride

International Nuclear Information System (INIS)

Maier, Luis

2015-01-01

The combination of a topological insulator (TI) and a superconductor (S), which together form a TI/S interface, is expected to influence the possible surface states in the TI. It is of special interest, if the theoretical prediction of zero energy Majorana states in this system is verifiable. This thesis presents the experimental realization of such an interface between the TI strained bulk HgTe and the S Nb and studies if the afore mentioned expectations are met. As these types of interfaces were produced for the first time the initial step was to develop a new lithographic process. Optimization of the S deposition technique as well as the application of cleaning processes allowed for reproducible fabrication of structures. In parallel the measurement setup was upgraded to be able to execute the sensitive measurements at low energy. Furthermore several filters have been implemented into the system to reduce high frequency noise and the magnetic field control unit was additionally replaced to achieve the needed resolution in the μT range. Two kinds of basic geometries have been studied: Josephson junctions (JJs) and superconducting quantum interference devices (SQUIDs). A JJ consists of two Nb contacts with a small separation on a HgTe layer. These S/TI/S junctions are one of the most basic structures possible and are studied via transport measurements. The transport through this geometry is strongly influenced by the behavior at the two S/TI interfaces. In voltage dependent differential resistance measurements it was possible to detect multiple Andreev reflections in the JJ, indicating that electrons and holes are able to traverse the HgTe gap between both interfaces multiple times while keeping phase coherence. Additionally using BTK theory it was possible to extract the interface transparency of several junctions. This allowed iterative optimization for the highest transparency via lithographic improvements at these interfaces. The increased transparency and

Expression of Fas, FasL, caspase-8 and other factors of the extrinsic apoptotic pathway during the onset of interdigital tissue elimination.

Science.gov (United States)

Svandova, E Budisova; Vesela, B; Lesot, H; Poliard, A; Matalova, E

2017-04-01

Elimination of the interdigital web is considered to be the classical model for assessing apoptosis. So far, most of the molecules described in the process have been connected to the intrinsic (mitochondrial) pathway. The extrinsic (receptor mediated) apoptotic pathway has been rather neglected, although it is important in development, immunomodulation and cancer therapy. This work aimed to investigate factors of the extrinsic apoptotic machinery during interdigital regression with a focus on three crucial initiators: Fas, Fas ligand and caspase-8. Immunofluorescent analysis of mouse forelimb histological sections revealed abundant expression of these molecules prior to digit separation. Subsequent PCR Array analyses indicated the expression of several markers engaged in the extrinsic pathway. Between embryonic days 11 and 13, statistically significant increases in the expression of Fas and caspase-8 were observed, along with other molecules involved in the extrinsic apoptotic pathway such as Dapk1, Traf3, Tnsf12, Tnfrsf1A and Ripk1. These results demonstrate for the first time the presence of extrinsic apoptotic components in mouse limb development and indicate novel candidates in the molecular network accompanying the regression of interdigital tissue during digitalisation.

SCMAG series of programs for calculating superconducting dipole and quadrupole magnets

International Nuclear Information System (INIS)

Green, M.A.

1974-10-01

Programs SCMAG1, SCMAG2, SCMAG3, and SCMAG4 are a group of programs used to design and calculate the characteristics of conductor dominated superconducting dipole and quadrupole magnets. These magnets are used to bend and focus beams of high energy particles and are being used to design the superconducting magnets for the LBL ESCAR accelerator. The four programs are briefly described. (TFD)

Fabrication of Superconducting Traction Transformer for Railway Rolling Stock

International Nuclear Information System (INIS)

Kamijo, H; Hata, H; Fujimoto, H; Inoue, A; Nagashima, K; Ikeda, K; Yamada, H; Sanuki, Y; Tomioka, A; Uwamori, K; Yoshida, S; Iwakuma, M; Funaki, K

2006-01-01

We designed a floor type single-phase 4 MVA superconducting traction transformer for Shinkansen rolling stock. In this study, we fabricated a prototype superconducting traction transformer based on this design. This transformer of the core-type design has a primary winding, four secondary windings and a tertiary winding. The windings are wound by Bi2223 superconducting tapes and cooled by subcooled liquid nitrogen. The core is kept at room temperature. The cryostat is made of GFRP with two holes to pass core legs through. The outer dimensions are about 1.2m x 0.7m x 1.9m excluding the compressor. Its weight is 1.71t excluding that of refrigerator and compressor. The transformer was tested according to Japanese Industrial Standards (JIS)-E5007. We confirmed that the performance of transformer has been achieved almost exactly as planned. The rated capacity is equivalent to 3.5MVA in the superconducting state

Current high-temperature superconducting coils and applications in Japan

International Nuclear Information System (INIS)

Matsushita, T.

2000-01-01

In Japan, four projects for the application of Bi-based superconducting magnets to practical apparatus are currently underway. These projects involve the development of an insert magnet for a 1 GHz nuclear magnetic resonance spectrometer, a magnet for a silicon single-crystal pulling apparatus, a magnet for a magnetic separation system, and a 1 T pulse magnet for a superconducting magnet energy storage system. For example, the magnet for the silicon single-crystal pulling apparatus is of the class with stored energy of 1 MJ to be operated at around 20 K. This review focuses on the present status of the development of these magnets, followed by a discussion of the problems of the present superconducting tapes that need to be overcome for future applications. (author)

Superconductivity suppression near metal-dielectric in transition highly disordered systems

International Nuclear Information System (INIS)

Kuchinskij, Eh.Z.; Sadovskij, M.V.; Ehrkabaev, M.A.

1997-01-01

The effects of temperature suppression of superconducting transition T c within wide limits of disorders values from low-disordered to highly-disordered ones caused by formation of the Coulomb gap in the states density are studied on the bases of the earlier proposed self consistent theory on the metal-dielectric. It is shown that the proposed theory gives satisfactory description of experimental data for a number of the systems under study

The design, magnetization and control of a superconducting permanent magnet synchronous motor

Energy Technology Data Exchange (ETDEWEB)

Jiang, Y; Pei, R; Xian, W; Hong, Z; Coombs, T A [Engineering Department, University of Cambridge, Trumpington Street, Cambridge CB2 1PZ (United Kingdom)], E-mail: yj222@cam.ac.uk

2008-06-15

This paper describes in detail the method of magnetization of a superconducting permanent magnet synchronous motor. The rotor of the motor consists of 60 superconducting pucks, which are magnetized by two additional copper windings. The pulse field magnetization (PFM) method is considered and the resulted distribution of the magnetizing flux linkage from the rotor is not a perfect sine wave in the air gap, which leads to a large torque ripple and harmonics of the stator currents. In order to suppress the torque ripple, an iterative learning control (ILC) algorithm is used in addition to the former field-oriented control method. The results show the ILC algorithm can largely reduce the torque ripple.

Superconductivity in Medicine

Science.gov (United States)

Alonso, Jose R.; Antaya, Timothy A.

2012-01-01

Superconductivity is playing an increasingly important role in advanced medical technologies. Compact superconducting cyclotrons are emerging as powerful tools for external beam therapy with protons and carbon ions, and offer advantages of cost and size reduction in isotope production as well. Superconducting magnets in isocentric gantries reduce their size and weight to practical proportions. In diagnostic imaging, superconducting magnets have been crucial for the successful clinical implementation of magnetic resonance imaging. This article introduces each of those areas and describes the role which superconductivity is playing in them.

Conceptual design of the superconducting magnet for the 250 MeV proton cyclotron.

Science.gov (United States)

Ren, Yong; Liu, Xiaogang; Gao, Xiang

2016-01-01

The superconducting cyclotron is of great importance to treat cancer parts of the body. To reduce the operation costs, a superconducting magnet system for the 250 MeV proton cyclotron was designed to confirm the feasibility of the superconducting cyclotron. The superconducting magnet system consists of a pair of split coils, the cryostat and a pair of binary high temperature superconductor current leads. The superconducting magnet can reach a central magnetic field of about 1.155 T at 160 A. The three GM cryocooler with cooling capacities of 1.5 W at 4.5 K and 35 W at 50 K and one GM cryocooler of 100 W at 50 K were adopted to cool the superconducting magnet system through the thermosiphon technology. The four GM cryocoolers were used to cool the superconducting magnet to realize zero evaporation of the liquid helium.

Electrostatic deflector development at the Chalk River superconducting cyclotron

International Nuclear Information System (INIS)

Diamond, W.T.; Mitchel, G.R.; Almeida, J.; Schmeing, H.

1991-01-01

An electrostatic deflector is used to extract heavy-ion beans from the Chalk River superconducting cyclotron. Deflector voltages up to 100 kV across a 7 m gap (143 kV/cm) are needed to extract the full range of beams that the cyclotron is designed to accelerate. This goal remains a challenge, but substantial progress has been made over the past year. Voltages over 90 kV have been reliably maintained over a 7.5 mm gap with a magnetic field of 3 T. Voltages of 74 kV have been used with a reduced gap of 4.75 mm (corresponding to a field greater than 150 kV/cm) to extract beams with magnetic fields up to 4.25 T. Major progress was achieved when the authors introduced a water-cooled, negative high-voltage electrode, and changed the sparking plates and the thin septum from molybdenum to stainless steel. Efforts are continuing to attain a field of at least 143 kV/cm over a gap of at least 6 mm width

Theory of high-T sub c superconductivity based on the fermion-condensation quantum phase transition

CERN Document Server

Amusia, M Ya; Shaginyan, V R

2001-01-01

A theory of high temperature superconductivity based on the combination of the fermion-condensation quantum phase transition and the conventional theory of superconductivity is presented. This theory describes maximum values of the superconducting gap which can be as big as DELTA sub 1 approx 0.1 epsilon sub F , with epsilon sub F being the Fermi level. It is shown that the critical temperature 2T sub c approx = DELTA sub 1. If there exists the pseudogap above T sub c then 2T* approx = DELTA sub 1 , and T* is the temperature at which the pseudogap vanished. A discontinuity in the specific heat at T sub c is calculated. The transition from conventional superconductors to high-T sub c ones as a function of the doping level is investigated

Evidence of multiband superconductivity in the quaternary borocarbide superconductor YNi2B2C using directional point-contact spectroscopy

International Nuclear Information System (INIS)

Raychaudhuri, Pratap; Sheet, Goutam; Mukhopadhyay, Sourin; Takeya, H.

2007-01-01

In this paper, we review our recent investigations on the gap anisotropy of the quaternary borocarbide superconductor YNi 2 B 2 C using directional point-contact spectroscopy. Through a detailed study of the temperature and magnetic field dependence of the superconducting energy gaps we show that the gap anisotropy in this material originates from electrons on different Fermi sheets having very different Fermi velocities. The gap anisotropy in this material is therefore well explained through a multiband scenario where electrons in different k-directions have very different electron-phonon coupling strength

Direct evidence of superconductivity and determination of the superfluid density in buried ultrathin FeSe grown on SrTiO3

Science.gov (United States)

Biswas, P. K.; Salman, Z.; Song, Q.; Peng, R.; Zhang, J.; Shu, L.; Feng, D. L.; Prokscha, T.; Morenzoni, E.

2018-05-01

Bulk FeSe is superconducting with a critical temperature Tc≅8 K and SrTiO3 is insulating in nature, yet high-temperature superconductivity has been reported at the interface between a single-layer FeSe and SrTiO3. Angle-resolved photoemission spectroscopy and scanning tunneling microscopy measurements observe a gap opening at the Fermi surface below ≈60 K. Elucidating the microscopic properties and understanding the pairing mechanism of single-layer FeSe is of utmost importance as it is a basic building block of iron-based superconductors. Here, we use the low-energy muon spin rotation/relaxation technique to detect and quantify the supercarrier density and determine the gap symmetry in FeSe grown on SrTiO3 (100). Measurements in applied field show a temperature-dependent broadening of the field distribution below ˜60 K, reflecting the superconducting transition and formation of a vortex state. Zero-field measurements rule out the presence of magnetism of static or fluctuating origin. From the inhomogeneous field distribution, we determine an effective sheet supercarrier density ns2 D≃6 ×1014cm-2 at T →0 K, which is a factor of 4 larger than expected from ARPES measurements of the excess electron count per Fe of 1 monolayer FeSe. The temperature dependence of the superfluid density ns(T ) can be well described down to ˜10 K by simple s -wave BCS, indicating a rather clean superconducting phase with a gap of 10.2(1.1) meV. The result is a clear indication of the gradual formation of a two-dimensional vortex lattice existing over the entire large FeSe/STO interface and provides unambiguous evidence for robust superconductivity below 60 K in ultrathin FeSe.

p -wave superconductivity in weakly repulsive 2D Hubbard model with Zeeman splitting and weak Rashba spin-orbit coupling

Science.gov (United States)

Hugdal, Henning G.; Sudbø, Asle

2018-01-01

We study the superconducting order in a two-dimensional square lattice Hubbard model with weak repulsive interactions, subject to a Zeeman field and weak Rashba spin-orbit interactions. Diagonalizing the noninteracting Hamiltonian leads to two separate bands, and by deriving an effective low-energy interaction we find the mean field gap equations for the superconducting order parameter on the bands. Solving the gap equations just below the critical temperature, we find that superconductivity is caused by Kohn-Luttinger-type interaction, while the pairing symmetry of the bands is indirectly affected by the spin-orbit coupling. The dominating attractive momentum channel of the Kohn-Luttinger term depends on the filling fraction n of the system, and it is therefore possible to change the momentum dependence of the order parameter by tuning n . Moreover, n also determines which band has the highest critical temperature. Rotating the magnetic field changes the momentum dependence from states that for small momenta reduce to a chiral px±i py type state for out-of-plane fields, to a nodal p -wave-type state for purely in-plane fields.

Florida State University superconducting linac

International Nuclear Information System (INIS)

Myers, E.G.; Fox, J.D.; Frawley, A.D.; Allen, P.; Faragasso, J.; Smith, D.; Wright, L.

1988-01-01

As early as the fall of 1977 it was decided that the future research needs of their nuclear structure laboratory required an increase in energy capability to at least 8 MeV per nucleon for the lighter ions, and that these needs could be met by the installation of a 17 MV tandem Van de Graaff accelerator. The chief problem with this proposal was the high cost. It became apparent that a far less expensive option was to construct a linear accelerator to boost the energy from their existing 9 MV tandem. The options open to them among linac boosters were well represented by the room temperature linac at Heidelberg and the superconducting Stony Brook and Argonne systems. By the Spring of 1979 it had been decided that both capital cost and electric power requirements favored a superconducting system. As regards the two superconducting resonator technologies - the Argonne niobium-copper or the Caltech-Stony Brook lead plated copper - the Argonne resonators, though more expensive to construct, had the advantages of more boost per resonator, greater durability of the superconducting surface and less stringent beam bunching requirements. In 1980 pilot funding from the State of Florida enabled the construction of a building addition to house the linac and a new target area, and the setting up of a small, three resonator, test booster. Major funding by the NSF for the laboratory upgrade started in 1984. With these funds they purchased their present helium liquefaction and transfer system and constructed three large cryostats, each housing four Argonne beta = 0.105 resonators and two superconducting solenoids. The last large cryostat was completed and installed on-line early this year and the linac was dedicated on March 20. Nuclear physics experiments using the whole linac began in early June. 4 references, 6 figures, 1 table

Superconductivity in technology

International Nuclear Information System (INIS)

Komarek, P.

1976-01-01

Physics, especially high energy physics and solid state physics was the first area in which superconducting magnets were used but in the long run, the most extensive application of superconductivity will probably be in energy technology. Superconducting power transmission cables, magnets for energy conversion in superconducting electrical machines, MHD-generators and fusion reactors and magnets for energy storage are being investigated. Magnets for fusion reactors will have particularly large physical dimensions, which means that much development effort is still needed, for there is no economic alternative. Superconducting surfaces in radio frequency cavities can give Q-values up to a factor of 10 6 higher than those of conventional resonators. Particle accelerators are the important application. And for telecommunication, simple coaxial superconducting radio frequency cables seem promising. The tunnel effect in superconducting junctions is now being developed commercially for sensitive magnetometers and may soon possibly feature in the memory cells of computer devices. Hence superconductivity can play an important role in the technological world, solving physical and technological problems and showing economic advantages as compared with possible conventional techniques, bearing also in mind the importance of reliability and safety. (author)

Anomalous spectral weight transfer at the superconducting transition of Bi2Sr2CaCu2O8+δ

International Nuclear Information System (INIS)

Dessau, D.S.; Wells, B.O.; Shen, Z.; Spicer, W.E.; Arko, A.J.; List, R.S.; Mitzi, D.B.; Kapitulnik, A.

1991-01-01

Anomalous spectral weight transfer at the superconducting transition of single-crystalline Bi 2 Sr 2 CaCu 2 O 8+δ was observed by high-resolution angle-resolved photoemission spectroscopy. As the sample goes superconducting, not only is there spectral weight transfer from the gap region to the pileup peak as in BCS theory, but along the Γ-bar M direction there is also some spectral weight transfer from higher binding energies in the form of a dip. In addition, we note that at the superconducting transition there is a decrease (increase) in the occupied spectral weight for the spectra taken along Γ-bar M (Γ-X)

Correlated Dirac particles and superconductivity on the honeycomb lattice

Science.gov (United States)

Wu, Wei; Scherer, Michael M.; Honerkamp, Carsten; Le Hur, Karyn

2013-03-01

We investigate the properties of the nearest-neighbor singlet pairing and the emergence of d-wave superconductivity in the doped honeycomb lattice considering the limit of large interactions and the t-J1-J2 model. First, by applying a renormalized mean-field procedure as well as slave-boson theories which account for the proximity to the Mott-insulating state, we confirm the emergence of d-wave superconductivity, in agreement with earlier works. We show that a small but finite J2 spin coupling between next-nearest neighbors stabilizes d-wave symmetry compared to the extendeds-wave scenario. At small hole doping, to minimize the energy and to gap the whole Fermi surface or all the Dirac points, the superconducting ground state is characterized by a d+id singlet pairing assigned to one valley and a d-id singlet pairing to the other, which then preserves time-reversal symmetry. The slightly doped situation is distinct from the heavily doped case (around 3/8 and 5/8 filling) supporting a pure chiral d+id symmetry and breaking time-reversal symmetry. Then, we apply the functional renormalization group and study in more detail the competition between antiferromagnetism and superconductivity in the vicinity of half filling. We discuss possible applications to strongly correlated compounds with copper hexagonal planes such as In3Cu2VO9. Our findings are also relevant to the understanding of exotic superfluidity with cold atoms.

Superconductivity and its pressure variation in GaAs

International Nuclear Information System (INIS)

Nirmala Louis, C.; Jayam, Sr. Gerardin; Amalraj, A.

2005-01-01

The electronic band structure, metallization, phase transition and superconducting transition of gallium arsenide under pressure are studied using TB-LMTO method. Metallization occurs via indirect closing of band gap between Γ and X points. GaAs becomes superconductor under high pressure but before that it undergoes structural phase transition from ZnS phase to NaCl phase. The ground state properties are analyzed by fitting the calculated total energies to the Birch-Murnaghan's equation of state. The superconducting transition temperatures (T c ) obtained as a function of pressure for both the ZnS and NaCl structures and GaAs comes under the class of pressure induced superconductor. When pressure is increased T c increases in both the normal and high pressure structures. The dependence of T c on electron-phonon mass enhancement factor λ shows that GaAs is an electron-phonon-mediated superconductor. Also it is found that GaAs retained in their normal structure under high pressure give appreciably high T c . (author)

A Green function approach to superconductivity in nanofilms

Energy Technology Data Exchange (ETDEWEB)

Saniz, Rolando; Partoens, Bart; Peeters, Francois [Universiteit Antwerpen, Antwerpen (Belgium)

2012-07-01

We reformulate the BCS theory of superconductivity in the Green function framework in such a way that it is readily applied to inhomogeneous systems. We study here nanofilms and go beyond previous models in that we take into account the effects of confinement on electron-phonon coupling, as well as on the electron and phonon fields. We show that, contrary to what has been advanced in recent years, the increases of the density of states as the film thickness increases will tend to suppress the critical temperature, and not enhance it. Instead, it is the increase of the phonon modes with increasing film thickness that can lead to increases of the critical temperature above the bulk value. Further, we show that the multigap character of superconductivity in nanofilms will result in general in a condensate composed of subcondensates with different coherence lengths. This is in analogy with the very recent suggestion that different coherence lengths exist in two-gap superconductors such as MgB{sub 2}.

Momentum-resolved hidden-order gap reveals symmetry breaking and origin of entropy loss in URu2Si2

Science.gov (United States)

Bareille, C.; Boariu, F. L.; Schwab, H.; Lejay, P.; Reinert, F.; Santander-Syro, A. F.

2014-07-01

Spontaneous symmetry breaking in physical systems leads to salient phenomena at all scales, from the Higgs mechanism and the emergence of the mass of the elementary particles, to superconductivity and magnetism in solids. The hidden-order state arising below 17.5 K in URu2Si2 is a puzzling example of one of such phase transitions: its associated broken symmetry and gap structure have remained longstanding riddles. Here we directly image how, across the hidden-order transition, the electronic structure of URu2Si2 abruptly reconstructs. We observe an energy gap of 7 meV opening over 70% of a large diamond-like heavy-fermion Fermi surface, resulting in the formation of four small Fermi petals, and a change in the electronic periodicity from body-centred tetragonal to simple tetragonal. Our results explain the large entropy loss in the hidden-order phase, and the similarity between this phase and the high-pressure antiferromagnetic phase found in quantum-oscillation experiments.

The Effect of Temperature Dependence of AC Losses in a Bi-2223/Ag Insert of an 8-T Superconducting Magnet

DEFF Research Database (Denmark)

Wang, Lei; Wang, Qiuliang; Wang, Hui

2016-01-01

A conduction-cooled split-gap superconducting magnet system with a center field of 8 T has been designed and fabricated in the Institute of Electrical Engineering, Chinese Academy of Sciences. The system consists of two Bi-2223/Ag coils and six NbTi coils. Due to a large aspect ratio of the high-...... in the second case. Hence, it is a good way to reduce the ac losses by changing the charging sequences of the Bi-2223/Ag and NbTi cols. Afterward, the calculated results are compared with the experimental data, and they show a good agreement.......A conduction-cooled split-gap superconducting magnet system with a center field of 8 T has been designed and fabricated in the Institute of Electrical Engineering, Chinese Academy of Sciences. The system consists of two Bi-2223/Ag coils and six NbTi coils. Due to a large aspect ratio of the high......-temperature superconducting tape, there will be large ac losses when the magnet is ramped up and down. An accurate estimation of the total ac losses in the high-temperature superconducting coils is essential for the cryogenic system design. In the Bi-2223/Ag coils, the total ac losses mainly originate from two parts: One...

Superconductivity optimization and phase formation kinetics study of internal-Sn Nb{sub 3}Sn superconducting wires

Energy Technology Data Exchange (ETDEWEB)

Zhang, Chaowu

2007-07-15

Superconductors Nb{sub 3}Sn wires are one of the most applicable cryogenic superconducting materials and the best choice for high-field magnets exceeding 10 T. One of the most significant utilization is the ITER project which is regarded as the hope of future energy source. The high-Cu composite designs with smaller number of sub-element and non-reactive diffusion barrier, and the RRP (Restacked Rod Process) internal-Sn technology are usually applied for the wire manufacturing. Such designed and processed wires were supplied by MSA/Alstom and WST/NIN in this research. The systematic investigation on internal-Sn superconducting wires includes the optimization of heat treatment (HT) conditions, phase formation and its relation with superconductivity, microstructure analysis, and the phase formation kinetics. Because of the anfractuosity of the configuration design and metallurgical processing, the MF wires are not sufficient for studying a sole factor effect on superconductivity. Therefore, four sets of mono-element (ME) wires with different Sn ratios and different third-element addition were designed and fabricated in order to explore the relationship between phase formation and superconducting performances, particularly the A15 layer growth kinetics. Different characterization technic have been used (magnetization measurements, neutron diffraction and SEM/TEM/EDX analysis). The A15 layer thicknesses of various ME samples were measured and carried out linear and non-linear fits by means of two model equations. The results have clearly demonstrated that the phase formation kinetics of Nb{sub 3}Sn solid-state reaction is in accordance with an n power relation and the n value is increased with the increase of HT temperature and the Sn ratio in the wire composite. (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.

Temperature evolution of subharmonic gap structures in MgB{sub 2}/Nb point-contacts

Energy Technology Data Exchange (ETDEWEB)

Giubileo, F. [CNR-INFM Laboratorio Regionale SUPERMAT e Dipartimento di Fisica ' E.R. Caianiello' , Universita degli Studi di Salerno, via Salvador Allende, 84081 Baronissi (Italy)], E-mail: giubileo@sa.infn.it; Bobba, F.; Scarfato, A.; Piano, S. [CNR-INFM Laboratorio Regionale SUPERMAT e Dipartimento di Fisica ' E.R. Caianiello' , Universita degli Studi di Salerno, via Salvador Allende, 84081 Baronissi (Italy); Aprili, M. [Laboratoire de Spectroscopie en Lumiere Polarisee, ESPCI, 10 rue Vauquelin, 75005 Paris (France); CSNSM-CNRS, Bat. 108 Universite Paris-Sud, 91405 Orsay (France); Cucolo, A.M. [CNR-INFM Laboratorio Regionale SUPERMAT e Dipartimento di Fisica ' E.R. Caianiello' , Universita degli Studi di Salerno, via Salvador Allende, 84081 Baronissi (Italy)

2007-09-01

We have performed point-contact spectroscopy experiments on superconducting micro-constrictions between Nb tips and high quality MgB{sub 2} pellets. We measured the temperature evolution (between 4.2 K and 300 K) of the current-voltage (I-V) and of the dynamical conductance (dI/dV-V) characteristics. Above the Nb critical temperature T{sub C}{sup Nb}, the conductance of the constrictions behaves as predicted by the BTK model for S/N contacts being Nb in its normal state below T{sub C}{sup Nb}, the contacts show Josephson current and subharmonic gap structures, due to multiple Andreev reflections. These observations clearly indicate the coupling of the MgB{sub 2} 3D {pi}-band with the Nb superconducting order parameter. We found {delta}{sub {pi}} = 2.4 {+-} 0.2 meV for the three-dimensional gap of MgB{sub 2}.

Theory of multiwave mixing within the superconducting kinetic-inductance traveling-wave amplifier

Science.gov (United States)

Erickson, R. P.; Pappas, D. P.

2017-03-01

We present a theory of parametric mixing within the coplanar waveguide (CPW) of a superconducting nonlinear kinetic-inductance traveling-wave (KIT) amplifier engineered with periodic dispersion loadings. This is done by first developing a metamaterial band theory of the dispersion-engineered KIT using a Floquet-Bloch construction and then applying it to the description of mixing of the nonlinear RF traveling waves. Our theory allows us to calculate signal gain versus signal frequency in the presence of a frequency stop gap, based solely on loading design. We present results for both three-wave mixing (3WM), with applied dc bias, and four-wave mixing (4WM), without dc. Our theory predicts an intrinsic and deterministic origin to undulations of 4WM signal gain with signal frequency, apart from extrinsic sources, such as impedance mismatch, and shows that such undulations are absent from 3WM signal gain achievable with dc. Our theory is extensible to amplifiers based on Josephson junctions in a lumped LC-ladder transmission line (TWPA).

III-V/Si Tandem Cells Utilizing Interdigitated Back Contact Si Cells and Varying Terminal Configurations: Preprint

Energy Technology Data Exchange (ETDEWEB)

Schnabel, Manuel; Klein, Talysa R.; Jain, Nikhil; Essig, Stephanie; Schulte-Huxel, Henning; Warren, Emily; van Hest, Maikel F. A. M.; Geisz, John; Stradins, Paul; Tamboli, Adele; Rienacker, Michael; Merkle, Agnes; Schmidt, Jan; Brendel, Rolf; Peibst, Robby

2017-07-11

Solar cells made from bulk crystalline silicon (c-Si) dominate the market, but laboratory efficiencies have stagnated because the current record efficiency of 26.3% is already very close to the theoretical limit of 29.4% for a single-junction c-Si cell. In order to substantially boost the efficiency of Si solar cells we have been developing stacked III-V/Si tandem cells, recently attaining efficiencies above 32% in four-terminal configuration. In this contribution, we use state-of-the-art III-V cells coupled with equivalent circuit simulations to compare four-terminal (4T) to three- and two-terminal (3T, 2T) operation. Equivalent circuit simulations are used to show that tandem cells can be operated just as efficiently using three terminals as with four terminals. However, care must be taken not to overestimate 3T efficiency, as the two circuits used to extract current interact, and a method is described to accurately determine this efficiency. Experimentally, a 4T GaInP/Si tandem cell utilizing an interdigitated back contact cell is shown, exhibiting a 4T efficiency of 31.5% and a 2T efficiency of 28.1%. In 3T configuration, it is used to verify the finding from simulation that 3T efficiency is overestimated when interactions between the two circuits are neglected. Considering these, a 3T efficiency approaching the 4T efficiency is found, showing that 3T operation is efficient, and an outlook on fully integrated high-efficiency 3T and 2T tandem cells is given.

Superconducting tunnel junctions on MgB{sub 2} using MgO and CaF{sub 2} as a barrier

Energy Technology Data Exchange (ETDEWEB)

Sakoda, Masahito, E-mail: sakoda@cc.tuat.ac.jp [Department of Applied Physics, Tokyo University of Agriculture and Technology, 2-24-16, Koganei, Tokyo 184-8588 (Japan); Aibara, Masato; Mede, Kazuya; Kikuchi, Motoyuki; Naito, Michio [Department of Applied Physics, Tokyo University of Agriculture and Technology, 2-24-16, Koganei, Tokyo 184-8588 (Japan)

2016-11-15

Highlights: • We have revised the manuscript according to reviewer's comments. The details are in “Response to Reviewers”. • Superconducting junctions with MgO and CaF{sub 2} barrier were fabricated in order to improve the quality of junctions. • In SIN junctions with MgO barrier, clear superconducting gap was observed. (). • In SIS junctions with CaF2 barrier, Josephson current was observed over 30 K. (). • The compatibility of each barrier material at the upper and lower interfaces was clarified. (). - Abstract: We report the fabrication of superconducting tunnel junctions, both of superconductor–insulator-normal metal (SIN) and superconductor–insulator-superconductor (SIS), on MgB{sub 2} using MgO and CaF{sub 2} as a barrier. The SIN junctions fabricated using an MgO barrier showed excellent quasi-particle characteristics, including a large superconducting gap (Δ) of 2.5–3 meV and a low zero-bias conductance. We have also fabricated SIS junctions with an MgO barrier, but the quasi-particle characteristics of the SIS junctions are not as good as those of the SIN junctions, namely a reduced superconducting gap and a high zero-bias conductance. It appears that top MgB{sub 2} electrodes do not grow well on an MgO barrier, which is also suggested from in-situ RHEED observation. The SIN junctions fabricated using a CaF{sub 2} barrier showed less sharp quasi-particle characteristics than using an MgO barrier. However, the SIS junctions using a CaF{sub 2} barrier showed a fairly large I{sub c}R{sub N} value at 4.2 K over 1 mV and also exhibited finite Josephson current up to almost the film's T{sub c} (∼30 K). The RHEED observation revealed that top MgB{sub 2} electrodes grow well on a CaF{sub 2} barrier.

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.

The Kohn-Luttinger mechanism and phase diagram of the superconducting state in the Shubin-Vonsovsky model

International Nuclear Information System (INIS)

Kagan, M. Yu.; Val’kov, V. V.; Mitskan, V. A.; Korovuskin, M. M.

2013-01-01

Using the Shubin-Vonsovsky model in the weak-coupling regime W > U > V (W is the bandwidth, U is the Hubbard onsite repulsion, and V is the Coulomb interaction at neighboring sites) based on the Kohn-Luttinger mechanism, we determined the regions of the existence of the superconducting phases with the d xy , p, s, and d x 2 -y 2 symmetry types of the order parameter. It is shown that the effective interaction in the Cooper channel considerably depends not only on single-site but also on intersite Coulomb correlations. This is demonstrated by the example of the qualitative change and complication of the phase diagram of the superconducting state. The superconducting (SC) phase induction mechanism is determined taking into account polarization contributions in the second-order perturbation theory in the Coulomb interaction. The results obtained for the angular dependence of the superconducting gap in different channels are compared with angule-resolved photoemission spectroscopy (ARPES) results. The influence of long-range hops in the phase diagram and critical superconducting transition temperature in different channels is analyzed. The conditions for the appearance of the Kohn-Luttinger superconductivity with the d x 2 -y 2 symmetry and high critical temperatures T c ∼ 100 K near the half-filling are determined

Calculation of mechanical vibration frequencies of stiffened superconducting cavities

International Nuclear Information System (INIS)

Black, S.J.; Spalek, G.

1992-01-01

We calculated the frequencies of transverse and longitudinal mechanical-vibration modes of the HEPL- modified, CERN/DESY four-cell superconducting cavity, using finite-element techniques. We compared the results of these calculations, including the stiffening of the cavity with rods, with mode frequencies measured at HEPL. The correlation between data was significant. The same techniques were also used to design and optimize the stiffening scheme for the seven-cell 805-MHz superconducting cavity being developed at Los Alamos. In this report, we describe the final stiffening scheme and the results of our calculations

Spin-polarons and high-Tc superconductivity

International Nuclear Information System (INIS)

Wood, R.F.

1994-03-01

The spin-polaron concept is introduced in analogy to ionic and electronic polarons and the assumptions underlying the author's approach to spin-polaron mediated high-T c superconductivity are discussed. Elementary considerations about the spin-polaron formation energy are reviewed and the possible origin of the pairing mechanism illustrated schematically. The electronic structure of the CuO 2 planes is treated from the standpoint of antiferromagnetic band calculations that lead directly to the picture of holes predominantly on the oxygen sublattice in a Mott-Hubbard/charge transfer insulator. Assuming the holes to be described in a Bloch representation but with the effective mass renormalized by spin-polaron formation, equations for the superconducting gap, Δ, and transition temperature, T c , are developed and the symmetry of Δ discussed. After further simplifications, T c is calculated as a function of the carrier concentration, x. It is shown that the calculated behavior of T c (x) follows the experimental results closely and leads to a natural explanation of the effects of under- and over-doping. The paper concludes with a few remarks about the evidence for the carriers being fermions (polarons) or bosons (bipolarons)

Bulk viscosity of spin-one color superconducting strange quark matter

International Nuclear Information System (INIS)

Wang Xinyang; Shovkovy, Igor A.

2010-01-01

The bulk viscosity in spin-one color superconducting strange quark matter is calculated by taking into account the interplay between the nonleptonic and semileptonic week processes. In agreement with previous studies, it is found that the inclusion of the semileptonic processes may result in non-negligible corrections to the bulk viscosity in a narrow window of temperatures. The effect is generally more pronounced for pulsars with longer periods. Compared to the normal phase, however, this effect due to the semileptonic processes is less pronounced in spin-one color superconductors. Assuming that the critical temperature of the phase transition is much larger than 40 keV, the main effect of spin-one color superconductivity in a wide range of temperatures is an overall increase of the bulk viscosity with respect to the normal phase. The corresponding enhancement factor reaches up to about 9 in the polar and A phases, about 25 in the planar phase, and about 29 in the color-spin-locked (CSL) phase. This factor is determined by the suppression of the nonleptonic rate in color superconducting matter and, therefore, may be even larger if all quark quasiparticles happen to be gapped.

Evidence for phonon-mediated coupling in superconducting Ba0.6K0.4BiO3

International Nuclear Information System (INIS)

Hinks, D.G.; Dabrowski, B.; Richards, D.R.; Jorgensen, J.D.; Pei, S.; Zasadzinski, J.F.

1989-01-01

Superconducting Ba 0.6 K 0.4 BiO 3 , with a T c of 30 K, shows a large 18 O isotope effect which indicates that phonons are involved in the pairing mechanism. Infrared reflectivity measurements indicate a value for the superconducting gap consistent with moderate coupling (2Δ/k T c = 3.5 ± 0.5). A mediating energy for pairing of about 40 meV would be required to obtain a T c of 30 K. Strong coupling of electrons by optical phonons (which are present in this material with energies up to 80 meV) could account for the observed transition temperature. Recent tunneling spectroscopy shows the presence of strongly coupled optical phonons in the 40 to 70 meV region, indicating that superconductivity in this material may be phonon mediated

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.

Nonlinearity in superconductivity and Josephson junctions

International Nuclear Information System (INIS)

Lazarides, N.

1995-01-01

Within the framework of the Bardeen, Cooper and Schrieffers (BCS) theory, the influence of anisotropy on superconducting states are investigated. Crystal anisotropy exists in un-conventional low temperature superconductors as e.g. U 1-x Th x Be 13 and in high temperature superconductors. Starting from a phenomenological pairing interaction of the electrons or holes, the BCS approach is used to derive a set of coupled nonlinear algebraic equations for the momentum dependent gap parameter. The emphasis is put on bifurcation phenomena between s-, d-wave and mixed s- and d-wave symmetry and the influence on measurable quantities as the electron specific heat, spin susceptibility and Josephson tunnelling. Pitch-fork and perturbed pitch-fork bifurcations have been found separating s- and d-wave superconducting states from mixed s- and d-wave states. The additional superconducting states give rise to jumps in the electron specific heat below the transition temperature. These jumps are rounded in the case of perturbed pitch-fork bifurcations. An experiment to measure the sign of the interlayer interaction using dc SQUIDS is suggested. The Ambegaokar-Baratoff formalism has been used for calculating the quasiparticle current and the two phase coherent tunnelling currents in a Josephson junction made of anisotropic superconductors. It is shown that anisotropy can lead to a reduction in the product of the normal resistance and the critical current. For low voltages across the junction the usual resistively shunted Josephson model can be used. Finally, bunching in long circular Josephson junctions and suppression of chaos in point junctions have been investigated. (au) 113 refs

Fabrication and energy harvesting characteristics of unimorph piezoelectric cantilever generators with interdigitated electrode lead zirconate titanate laminates

Science.gov (United States)

Lee, Min-seon; Yun, Ji-sun; Park, Woon-ik; Hong, Youn-woo; Cho, Jeong-ho; Paik, Jong-hoo; Park, Yong Ho; Son, Chun-myung; Jeong, Young Hun

2017-12-01

Interdigitated electrode (IDE) unimorph piezoelectric cantilever generators (UPCGs) were fabricated and their energy harvesting characteristics were investigated. A hard lead zirconate titanate (PZT) material with a high mechanical quality factor (Q m) of 1280 was used for the active piezoelectric film of the IDE UPCGs. Two different laminated IDE UPCGs were prepared; one has Ag/Pd interdigitated electrode (IDE) formed only on the top and bottom PZT sheets (D-IDE), while the other has Ag/Pd IDE on all of the PZT sheets (M-IDE). Cofiring was conducted at 1050 °C for 2 h for PZT laminates with IDEs. The fabricated IDE UPCGs exhibited power densities of 50.4 µW/cm3 for the D-IDE and 820 µW/cm3 for the M-IDE. The UPCG with the M-IDE exhibited a higher performance than that with the D-IDE. Specifically, a significantly enhanced normalized power factor of 670 µW/(g2·cm3) was found at 118 Hz across 100 kΩ.

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.

Extended Majorana zero modes in a topological superconducting-normal T-junction

Science.gov (United States)

Spånslätt, Christian; Ardonne, Eddy

2017-03-01

We investigate the sub gap properties of a three terminal Josephson T-junction composed of topologically superconducting wires connected by a normal metal region. This system naturally hosts zero energy Andreev bound states which are of self-conjugate Majorana nature and we show that they are, in contrast to ordinary Majorana zero modes, spatially extended in the normal metal region. If the T-junction respects time-reversal symmetry, we show that a zero mode is distributed only in two out of three arms in the junction and tuning the superconducting phases allows for transfer of the mode between the junction arms. We further provide tunneling conductance calculations showing that these features can be detected in experiments. Our findings suggest an experimental platform for studying the nature of spatially extended Majorana zero modes.

Spatial distribution of superconducting and charge-density-wave order parameters in cuprates and its influence on the quasiparticle tunnel current (Review Article)

Science.gov (United States)

Gabovich, Alexander M.; Voitenko, Alexander I.

2016-10-01

The state of the art concerning tunnel measurements of energy gaps in cuprate oxides has been analyzed. A detailed review of the relevant literature is made, and original results calculated for the quasiparticle tunnel current J(V) between a metallic tip and a disordered d-wave superconductor partially gapped by charge density waves (CDWs) are reported, because it is this model of high-temperature superconductors that becomes popular owing to recent experiments in which CDWs were observed directly. The current was calculated suggesting the scatter of both the superconducting and CDW order parameters due to the samples' intrinsic inhomogeneity. It was shown that peculiarities in the current-voltage characteristics inherent to the case of homogeneous superconducting material are severely smeared, and the CDW-related features transform into experimentally observed peak-dip-hump structures. Theoretical results were used to fit data measured for YBa2Cu3O7-δ and Bi2Sr2CaCu2O8+δ. The fitting demonstrated a good qualitative agreement between the experiment and model calculations. The analysis of the energy gaps in high-Tc superconductors is important both per se and as a tool to uncover the nature of superconductivity in cuprates not elucidated so far despite of much theoretical effort and experimental progress.

Submicron superconducting structures

International Nuclear Information System (INIS)

Golovashkin, A.I.; Lykov, A.N.

1986-01-01

An overview of works concerning superconducting structures of submicron dimensions and a system of such structures is given. It is noted that usage of the above structures in superconducting microelectronics permits, first, to increase the element packing density, to decrease the signal transmission time, capacity, power dissipated in high-frequency applications. Secondly, negligible coherence length in transition metals, their alloys and high-temperature compounds also restrict the dimensions of superconducting weak couplings when the 'classical' Josephson effect is displayed. The most effective methods for production of submicron superconducting structures are the following: lithography, double scribering. Recently the systems of superconducting submicron elements are extensively studied. It is shown that such systems can be phased by magnetic field

Experimental and analytical study of the DC breakdown characteristics of polypropylene laminated paper with a butt gap condition considering the insulation design of superconducting cable

Science.gov (United States)

Seo, In-jin; Choi, Won; Seong, Jae-gyu; Lee, Bang-wook; Koo, Ja-yoon

2014-08-01

It has been reported that the insulation design under DC stress is considered as one of the critical factors in determining the performance of high-voltage direct current (HVDC) superconducting cable. Therefore, it is fundamentally necessary to investigate the DC breakdown characteristics of the composite insulation system consisting of liquid nitrogen (LN2)/polypropylene-laminated-paper (PPLP). In particular, the insulation characteristics under DC polarity reversal condition should be verified to understand the polarity effect of the DC voltage considering the unexpected incidents taking place at line-commutated-converters (LCC) under service at a DC power grid. In this study, to examine the variation of DC electric field strength, the step voltage and polarity reversal breakdown tests are performed under DC stress. Also, we investigate the electric field distributions in a butt gap of the LN2/PPLP condition considering the DC polarity reversal by using simulation software.

Superconducting magnets for the RAON electron cyclotron resonance ion source.

Science.gov (United States)

Choi, S; Kim, Y; Hong, I S; Jeon, D

2014-02-01

The RAON linear accelerator of Rare Isotope Science Project has been developed since 2011, and the superconducting magnet for ECRIS was designed. The RAON ECR ion source was considered as a 3rd generation source. The fully superconducting magnet has been designed for operating using 28 GHz radio frequency. The RAON ECRIS operates in a minimum B field configuration which means that a magnetic sextupole field for radial confinement is superimposed with a magnetic mirror field for axial confinement. The highest field strength reaches 3.5 T on axis and 2 T at the plasma chamber wall for operating frequency up to 28 GHz. In this paper, the design results are presented of optimized superconducting magnet consisting of four solenoids and sextupole. The prototype magnet for ECRIS was fabricated and tested to verify the feasibility of the design. On the basis of test results, a fully superconducting magnet will be fabricated and tested.