Double-valued strong-coupling corrections to Bardeen-Cooper-Schrieffer ratios

Abstract

The experimental discovery of near-room-temperature (NRT) superconductivity in highlycompressed H3S, LaH10 and YH6 has restored fundamental interest in the electron-phonon pairing mechanism in superconductors. One of the prerequisites of phonon-mediated NRT superconductivity in highly compressed hydrides is strong electron-phonon interactions, which can be quantified by dimensionless ratios of the Bardeen-Cooper-Schrieffer (BCS) theory vs variable, where Tc is the critical temperature and ωln is the logarithmic phonon frequency (Mitrovic et al 1984 Phys. Rev. B 29 184). However, all known strong-coupling correction functions for the BCS ratios are applicable for < 0.20, which is not a high enough range for NRT superconductors, because the latter exhibit variable values of 0.13 < < 0.32. In this paper, we reanalyze the full experimental dataset (including data for highly compressed H3S) and find that the strong-coupling correction functions for the gap-to-critical-temperature ratio and for the specific-heat-jump ratio are double-valued nearly linear functions of . © 2020 IOP Publishing Ltd.