Evaluation of a practical level of critical current densities in pnictides and recently discovered superconductors

Abstract

A dissipation-free current is one of the most fascinating and practically important properties of superconductors. At self-field conditions (when no external magnetic field is applied) dissipation-free current density, Jc(sf, T), in thin weak-link-free superconductors described by the equation (where λ(T) is the London penetration depth, and κ is the Ginzburg–Landau parameter) was proved for more than 90 superconductors, including type-I and type-II superconductors, elementary superconductors, pnictides, cuprates, MgB2, heavy fermions and H3S. In addition, it was recently proposed for quasi-two dimensional superconductors (namely pnictides and cuprates), that maximum achievable critical current density, Jc(sf, T ∼ 0 K), is linked with the transition temperature, Tc, and the mean spacing between superconducting sheets, d, by the following equation: (Talantsev and Crump 2018 Supercond. Sci. Technol. 31 124001). In this paper, we focused on the inverse problem, i.e., to find the best candidates for the developing practical wires in terms of their self-field critical current capacity from known parameters of newly discovered superconductors (for which we draw largely on Hosono et al 2015 Sci. Technol. Adv. Mater. 16 033503). Considering that in-field critical currents of iron-based superconductors are very slow functions of applied magnetic fields, our calculations may have wider applicability outside self-field conditions.

Classifying hydrogen-rich superconductors

“…36,37) for compressed LaH10 there is a need to make an assumption about the value for Ginzburg-Landau parameter, . Our approach is based on an assumption that  for LaH10 will be not much different from  for H3S and other unconventional superconductors (primarily, pnictides and cuprates) which have values within a range of  = 60-120 [65][66][67][68][69][70][71]. Calculated 𝑇 𝑓𝑙𝑢𝑐,𝑝ℎ𝑎𝑠𝑒 and 𝑇 𝑓𝑙𝑢𝑐,𝑎𝑚𝑝 for LaH10 are given in Table III.…”

Cooper pair trajectories in superconducting slab at self-field conditions

“…To deduce the London penetration depth, 𝜆(𝑇 = 2𝐾), universal equation for isotropic superconductor [26,27]):…”

“…To calculate trajectories there is a need to determine Cooper pair velocity, 𝑣 𝑦 (𝑡 = 0) = 𝑣 𝐶,𝑐 , at the condition of critical current flow. The value of 𝑣 𝐶,𝑐 is determined by the use of the momentum of the Cooper pair expressed through its de Broglie wavelength, dB,c(T) [27], at critical current:…”

DC Self-Field Critical Current in Superconductor/Dirac-Cone Material/Superconductor Junctions

“…Herein, the simplest available function [53] that was proposed for the S/DCM/S junction in the Equation (9) was chosen as an example. However, other proposed functions for Equation (9) (for which we refer the reader to Reference [12]) have identical unresolved problem, because, as this was shown for about 100 weak-link superconductors [2,3,4,5,66], the limit should be (Equation (1)):Ic(sf,T)=limL→0(1.33·e·sans-serifΔ(T)ℏ·Wπ·L)=ϕ0π·μ0·[ln(1+2·κc(T))λab3(T)·(λc(T)b·tanh(bλc(T)))+newlineln(1+2·γ(T)·κc(T))γ(T)·λab3<...>…”