Conventional s-wave superconductivity in BiS2-based NdO0.71F0.29BiS2 revealed by thermal transport measurements

TL;DR

This study uses thermal transport measurements to demonstrate that NdO$_{0.71}$F$_{0.29}$BiS$_{2}$ exhibits conventional s-wave superconductivity with a fully gapped structure, contrasting with nodal superconductors.

Contribution

The paper provides experimental evidence for conventional s-wave superconductivity in a BiS$_2$-based compound through thermal conductivity analysis.

Findings

Small residual linear thermal conductivity at zero field

Magnetic field has little effect on thermal conductivity

Indicates a fully gapped, conventional s-wave superconductor

Abstract

To study the superconducting gap structure of BiS$_2$-based layered compound NdO$_{0.71}$F$_{0.29}$BiS$_{2}$ ($T$$_{\rm c}$ = 5 K), we measured the thermal conductivity $\kappa$, which is a sensitive probe of the low-energy quasiparticle spectrum. In the absence of a magnetic field, there is only a very small residual linear term in the thermal conductivity $\kappa_{0}$/$T$ at $T$ $\rightarrow$ 0, indicating the absence of a residual normal fluid, expected for nodal superconductors. Moreover, the applied magnetic field hardly affects the thermal conductivity in the wide range of the vortex state, indicating the absence of Doppler shifted quasiparticles. These results provide evidence that NdO$_{0.71}$F$_{0.29}$BiS$_{2}$ is fully gapped superconductor. The obtained gap structure, along with the robustness of the superconductivity against the impurity, suggest a conventional $s$-wave superconducting state in NdO$_{0.71}$F$_{0.29}$BiS$_{2}$.