Doublevalued strongcoupling corrections to BardeenCooperSchrieffer ratios
Abstract
The experimental discovery of nearroomtemperature (NRT) superconductivity in highlycompressed H_{3}S, LaH_{10} and YH_{6} has restored fundamental interest in the electronphonon pairing mechanism in superconductors. One of the prerequisites of phononmediated NRT superconductivity in highly compressed hydrides is strong electronphonon interactions, which can be quantified by dimensionless ratios of the BardeenCooperSchrieffer (BCS) theory vs $\left( {{k_B}{T_c}} \right)/\left( {\hbar {\omega _{ln}}} \right)$ variable, where T_{c} is the critical temperature and ${\omega _{ln}}$ is the logarithmic phonon frequency (Mitrovic et al 1984 Phys. Rev. B 29 184). However, all known strongcoupling correction functions for the BCS ratios are applicable for $\left( {{k_B}{T_c}} \right)/\left( {\hbar {\omega _{ln}}} \right)$ < 0.20, which is not a high enough $\left( {{k_B}{T_c}} \right)/\left( {\hbar {\omega _{ln}}} \right)$ range for NRT superconductors, because the latter exhibit variable values of 0.13 < $\left( {{k_B}{T_c}} \right)/\left( {\hbar {\omega _{ln}}} \right)$ < 0.32. In this paper, we reanalyze the full experimental dataset (including data for highly compressed H_{3}S) and find that the strongcoupling correction functions for the gaptocriticaltemperature ratio and for the specificheatjump ratio are doublevalued nearly linear functions of $\left( {{k_B}{T_c}} \right)/\left( {\hbar {\omega _{ln}}} \right)$ .
 Publication:

Superconductor Science Technology
 Pub Date:
 December 2020
 DOI:
 10.1088/13616668/abbb19
 arXiv:
 arXiv:2006.08390
 Bibcode:
 2020SuScT..33l4003T
 Keywords:

 highlycompressed sulphur hydride;
 gaptocriticaltemperature ratio;
 specificheatjump ratio;
 strongcoupling correction functions for BCS theory;
 Condensed Matter  Superconductivity
 EPrint:
 22 pages, 8 figures