Nonreciprocal Charge Transport in Topological Kagome Superconductor CsV$_{3}$Sb$_{5}$

TL;DR

This paper reports a strong nonreciprocal charge transport in superconducting CsV$_{3}$Sb$_{5}$ thin flakes, linked to symmetry breaking possibly from an unconventional superconducting order parameter, despite its centrosymmetric structure.

Contribution

It demonstrates nonreciprocal transport phenomena in CsV$_{3}$Sb$_{5}$, highlighting effects of symmetry breaking in a centrosymmetric superconductor, which is a novel observation.

Findings

Second harmonic voltages indicate vortex motion rectification.

Magnetoresistances show peaks and sign reversals.

Nonreciprocity suggests unconventional symmetry breaking.

Abstract

Nonreciprocal charge transport phenomena are widely studied in two-dimensional superconductors, which demonstrate unidirectional-anisotropy magnetoresistances as a result of symmetry breaking. Here, we report a strong nonreciprocal transport phenomenon in superconducting CsV$_{3}$Sb$_{5}$ thin flakes. The second harmonic voltages, mainly originating from the rectification effect of vortex motion, are unambiguously developed with in-plane and out-of-plane magnetic fields, and their magnitudes are comparable to those in noncentrosymmetric superconductors. The second harmonic magnetoresistances split into several peaks and some of them reverse their signs by ramping the magnetic field or the current within the superconducting transition. The nonreciprocity suggests a strong asymmetry in CsV$_{3}$Sb$_{5}$. The centrosymmetric structure and symmetric electronic phases in CsV$_{3}$Sb$_{5}$ can hardly induce the distinct nonreciprocal transport phenomenon, which could be correlated to a symmetry breaking from an unconventional superconducting order parameter symmetry.