Evolution of two-gap behavior of the superconductor FeSe_1-x

TL;DR

This study investigates how the superfluid density of FeSe_1-x changes with pressure and reveals that the large-gap band primarily influences the increase in transition temperature and superfluid density.

Contribution

It demonstrates that pressure-induced changes in FeSe_1-x are mainly driven by the band with the large superconducting gap, advancing understanding of multi-gap superconductivity.

Findings

Superfluid density increases with pressure and T_c.

Large-gap band dominates the pressure effect on superconductivity.

Small-gap band remains unaffected by pressure.

Abstract

The superfluid density, \rho_s, of the iron chalcogenide superconductor, FeSe_1-x, was studied as a function of pressure by means of muon-spin rotation. The zero-temperature value of \rho_s increases with increasing transition temperature T_c (increasing pressure) following the tendency observed for various Fe-based and cuprate superconductors. The analysis of \rho_s(T) within the two-gap scheme reveals that the effect on both, T_c and \rho_s(0), is entirely determined by the band(s) where the large superconducting gap develops, while the band(s) with the small gap become practically unaffected.