Muon spin relaxation study of the layered kagome superconductor CsV3Sb5

Abstract

The ${\mathbb{Z}}_{2}$ topological metals $R{\mathrm{V}}_{3}{\mathrm{Sb}}_{5}$ ($R$ = K, Rb, Cs) with a layered kagome structure provide a unique opportunity to investigate the interplay between charge order, superconductivity, and topology. Here, we report muon-spin relaxation/rotation ($\ensuremath{\mu}\mathrm{SR}$) measurements performed on $\mathrm{Cs}{\mathrm{V}}_{3}{\mathrm{Sb}}_{5}$ across a broad temperature range, in order to uncover the nature of the charge density wave order and superconductivity in this material. From zero-field $\ensuremath{\mu}\mathrm{SR}$, we find that spontaneous magnetic fields appear below 50 K, which is well below the charge density wave transition (${T}^{*}\ensuremath{\sim}93$ K). We show that these spontaneous fields are dynamic in nature making it difficult to associate them with a hidden static order. The superconducting state of $\mathrm{Cs}{\mathrm{V}}_{3}{\mathrm{Sb}}_{5}$ is found to preserve time-reversal symmetry, and the transverse-field $\ensuremath{\mu}\mathrm{SR}$ results are consistent with a superconducting state that has two fully open gaps.