scholarly journals Josephson Currents and Gap Enhancement in Graph Arrays of Superconductive Islands

Entropy ◽  
2021 ◽  
Vol 23 (7) ◽  
pp. 811
Author(s):  
Massimiliano Lucci ◽  
Davide Cassi ◽  
Vittorio Merlo ◽  
Roberto Russo ◽  
Gaetano Salina ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Energy Gap ◽  
Quantitative Agreement ◽  
Josephson Coupling ◽  
Cooper Pairs ◽  
Coupling Energy ◽  
Qualitative And Quantitative ◽  
Superconducting Energy Gap ◽  
Theoretical Predictions ◽  
New Phase

Evidence is reported that topological effects in graph-shaped arrays of superconducting islands can condition superconducting energy gap and transition temperature. The carriers giving rise to the new phase are couples of electrons (Cooper pairs) which, in the superconducting state, behave as predicted for bosons in our structures. The presented results have been obtained both on star and double comb-shaped arrays and the coupling between the islands is provided by Josephson junctions whose potential can be tuned by external magnetic field or temperature. Our peculiar technique for probing distribution on the islands is such that the hopping of bosons between the different islands occurs because their thermal energy is of the same order of the Josephson coupling energy between the islands. Both for star and double comb graph topologies the results are in qualitative and quantitative agreement with theoretical predictions.

scholarly journals Generalized Anderson’s theorem for superconductors derived from topological insulators

2020 ◽  
Vol 6 (9) ◽  
pp. eaay6502 ◽  
Author(s):  
Lionel Andersen ◽  
Aline Ramires ◽  
Zhiwei Wang ◽  
Thomas Lorenz ◽  
Yoichi Ando
Keyword(s):  
Degrees Of Freedom ◽  
Energy Gap ◽  
Energy Scale ◽  
Cooper Pairs ◽  
Topological Superconductors ◽  
Scattering Rate ◽  
Nonmagnetic Impurities ◽  
Superconducting Energy Gap ◽  
Strong Scattering ◽  
Internal Degrees Of Freedom

A well-known result in unconventional superconductivity is the fragility of nodal superconductors against nonmagnetic impurities. Despite this common wisdom, Bi2Se3-based topological superconductors have recently displayed unusual robustness against disorder. Here, we provide a theoretical framework that naturally explains what protects Cooper pairs from strong scattering in complex superconductors. Our analysis is based on the concept of superconducting fitness and generalizes the famous Anderson’s theorem into superconductors having multiple internal degrees of freedom with simple assumptions such as the Born approximation. For concreteness, we report on the extreme example of the Cux(PbSe)5(BiSe3)6 superconductor. Thermal conductivity measurements down to 50 mK not only give unambiguous evidence for the existence of nodes but also reveal that the energy scale corresponding to the scattering rate is orders of magnitude larger than the superconducting energy gap. This provides the most spectacular case of the generalized Anderson’s theorem protecting a nodal superconductor.

MASS LOSSES OF MAGNETIZED RHEOLOGICAL MEDIUMS SUBJECTED TO MAGNETIC FIELD

2002 ◽  
Vol 16 (17n18) ◽  
pp. 2718-2724
Author(s):  
A. R. BAEV ◽  
N. P. MATOUSSEVITCH
Keyword(s):  
Magnetic Field ◽  
Experimental Data ◽  
Quantitative Agreement ◽  
Normal Vector ◽  
Magnetic Intensity ◽  
Moving Plate ◽  
Qualitative And Quantitative ◽  
Mass Losses ◽  
Solid Plate ◽  
Real Behavior

Theoretical analysis and experimental research of the film flowing of magnetorheologic fluids when infinitive solid plate is retrieving from the former mediums were carried out. We have got dependencies of fluids mass losses m vs: velocity of moving plate V; magnitude of magnetic intensity, its gradient and angle φ between direction of intensity lines and normal vector to plane of plate. It is shown that theoretical and experimental m(φ) is anisotropy one and may change its magnitude more than 10 times. Real behavior and extreme characteristics of m(φ) depends on rhelogiacal parameters of MRS and its magnetization. Obtained experimental data of dependence m(V) are in qualitative and quantitative agreement with the modernized theory.

FIELD-INDUCED TOMONAGA–LUTTINGER LIQUID OF A QUASI-ONE-DIMENSIONAL S = 1 ANTIFERROMAGNET

2007 ◽  
Vol 21 (16) ◽  
pp. 965-976
Author(s):  
M. HAGIWARA ◽  
H. TSUJII ◽  
C. R. ROTUNDU ◽  
B. ANDRAKA ◽  
Y. TAKANO ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Specific Heat ◽  
Energy Gap ◽  
Luttinger Liquid ◽  
Quantitative Agreement ◽  
Conclusive Evidence ◽  
One Dimensional ◽  
Conformal Field ◽  
Magnetic Specific Heat ◽  
Field Approaches

We review the results of specific-heat experiments on the S = 1 quasi-one-dimensional (quasi-1D) bond-alternating antiferromagnet Ni(C 9 H 24 N 4)( NO 2) ClO 4, alias NTENP. At low temperatures above the transition temperature of a field-induced long-range order, the magnetic specific heat (C mag ) of this compound becomes proportional to temperature (T), when a magnetic field along the spin chains exceeds the critical field H c at which the energy gap vanishes. The ratio C mag /T, which increases as the magnetic field approaches H c from above, is in good quantitative agreement with a prediction of conformal field theory combined with the field-dependent velocity of the excitations calculated by the Lanczos method. This result is the first conclusive evidence for a Tomonaga–Luttinger liquid in a gapped quasi-1D antiferromagnet.

scholarly journals Effect of external magnetic field on the co-existence of superconductivity and antiferromagnetism in rare earth nickel borocarbides (RNi2B2C)

2016 ◽  
Vol 30 (08) ◽  
pp. 1650044
Author(s):  
Salila Das ◽  
Prakash Chandra Padhi
Keyword(s):  
Magnetic Field ◽  
Rare Earth ◽  
External Magnetic Field ◽  
Energy Gap ◽  
Density Wave ◽  
Spin Density Wave ◽  
Mean Field ◽  
Antiferromagnetic Order ◽  
Superconducting Energy Gap ◽  
Nickel Borocarbides

In this paper, we have studied the effect of external magnetic field in the co-existing phase of superconducting and antiferromagnetism (AFM) of rare earth nickel borocarbides. The AFM in these systems might have originated due to both localized “f” electrons as well as itinerant electrons which are responsible for conduction. On the other hand, superconductivity (SC) is due to spin density wave, arising out of Fermi surface instability. The AFM order is mostly influenced by hybridization of the “f” electron with the conduction electron. Here, we have obtained the dependence of superconducting energy gap as well as staggered magnetic field on temperature T and energy [Formula: see text] in a framework based on mean field Hamiltonian using double time electron Green’s function. We have shown in our calculation the effect of external magnetic field on superconducting and antiferromagnetic order parameters for [Formula: see text] in the presence of hybridization. The ratio of the calculated effective gap and [Formula: see text] is close to BCS value which agrees quite well with experimental results.

scholarly journals Spectroscopic evidence of mixed angular momentum symmetry in non-centrosymmetric Ru$$_7$$B$$_3$$

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Soumya Datta ◽  
Aastha Vasdev ◽  
Ranjani Ramachandran ◽  
Soumyadip Halder ◽  
Kapil Motla ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Angular Momentum ◽  
Energy Gap ◽  
Inversion Symmetry ◽  
Pairing Symmetries ◽  
Superconducting Energy Gap ◽  
Field Dependent ◽  
Scanning Tunnelling ◽  
Triplet Pairing ◽  
Scanning Tunnelling Spectroscopy

AbstractSuperconducting crystals with a lack of inversion symmetry can potentially host unconventional pairing. However, till today, no direct conclusive experimental evidence of such unconventional order parameters in non-centrosymmetric superconductors has been reported. In this paper, through direct measurement of the superconducting energy gap by scanning tunnelling spectroscopy, we report the existence of both s-wave (singlet) and p-wave (triplet) pairing symmetries in non-centrosymmetric Ru$$_7$$ 7 B$$_3$$ 3 . Our temperature and magnetic field-dependent studies also indicate that the relative amplitudes of the singlet and triplet components change differently with temperature.

Sign in / Sign up

Export Citation Format

Share Document