Superconducting gap symmetry of the BiS$_2$-based superconductor LaO$_{0.5}$F$_{0.5}$BiSSe elucidated through specific heat measurement

TL;DR

This study investigates the superconducting gap symmetry of LaO$_{0.5}$F$_{0.5}$BiSSe using specific heat measurements on a single crystal, revealing strong electron-phonon coupling and a fully gapped superconducting state.

Contribution

The paper provides the first specific heat analysis of LaO$_{0.5}$F$_{0.5}$BiSSe, demonstrating strong coupling and a fully gapped superconducting state in this BiS$_2$-based superconductor.

Findings

Superconducting transition at 3.95 K confirmed bulk superconductivity.

Strong electron-phonon coupling indicated by specific heat ratios.

Superconductivity is fully gapped based on temperature and magnetic field dependence.

Abstract

In this study, the superconducting gap symmetry of LaO$_{0.5}$F$_{0.5}$BiSSe is elucidated through specific heat measurements with one single crystal of LaO$_{0.5}$F$_{0.5}$BiSSe. A clear jump is observed at 3.95 K in LaO$_{0.5}$F$_{0.5}$BiSSe, suggesting bulk superconductivity. From specific heat measurements, $\Delta C_\mathrm{e}/\gamma T_\mathrm{c}$ and 2$\Delta$(0)/$k_\mathrm{B}T_\mathrm{c}$ are obtained as 2.31 and 4.5. These values indicate strong electron-phonon coupling superconductivity. The temperature ($T$) and magnetic-field ($H$) dependence of the electronic specific heat $C_\mathrm{e}(T, H)$ suggests that superconductivity is fully gapped. Our handmade system successfully elucidates superconducting gap symmetry of the BiS$_2$-based compound with a small single crystal.