Superconducting gap structure in ambient-pressure-grown $\mathrm{LaO_{0.5}F_{0.5}BiS_{2}}$

TL;DR

This study investigates the superconducting gap structure of ambient-pressure-grown LaO0.5F0.5BiS2 using muon spin relaxation, revealing multigap or anisotropic s-wave behavior and no magnetic order down to 25 mK.

Contribution

It provides the first detailed muon spin relaxation analysis of ambient-pressure-grown LaO0.5F0.5BiS2, identifying its gap symmetry and comparing it with other BiS2-based superconductors.

Findings

No magnetic order detected down to 25 mK.

Superconducting gap fits multigap s + s-wave or anisotropic s-wave models.

BiS2-based superconductors follow the Uemura relation.

Abstract

We have performed transverse-field muon spin relaxation (TF-$\mu$SR) measurements on ambient-pressure-grown polycrystalline $\mathrm{LaO_{0.5}F_{0.5}BiS_{2}}$. From these measurements, no signature of magnetic order is found down to 25 mK. The value of the magnetic penetration depth extrapolated to 0 K is 0.89 (5) $\mu$m. The temperature dependence of superconducting penetration depth is best described by either a multigap s + s-wave model with $\Delta_{1}$ = 0.947 (7) meV and $\Delta_{2}$ = 0.22 (4) meV or the ansiotropic s-wave model with $\Delta(0)$ = 0.776 meV and anisotropic gap amplitude ratio $\Delta_{min}/\Delta_{max}$ = 0.34. Comparisons with other potentially multigap $\mathrm{BiS_{2}}$-based superconductors are discussed. We find that these $\mathrm{BiS_{2}}$-based superconductors, including $\mathrm{Bi_{4}O_{4}S_3}$ and the high-pressure synthesized $\mathrm{LaO_{0.5}F_{0.5}BiS_{2}}$, generally conform to the Uemura relation.