Time-reversal symmetry-breaking phenomena in transport study of kagome superconductivity

TL;DR

This paper reviews recent experimental evidence of time-reversal symmetry-breaking in kagome superconductors, highlighting phenomena like magnetic hysteresis and diode effects, and discusses potential mechanisms such as chiral order parameters.

Contribution

It provides a comparative analysis of experiments on vanadium-based kagome superconductors and explores possible unconventional superconducting mechanisms.

Findings

Magnetic hysteresis observed in Josephson junctions below Tc

Zero-field superconducting diode effect in CsV3Sb5

Chiral superconducting order and pair density waves as possible explanations

Abstract

Recent studies have found that all three materials within the vanadium-based kagome superconductors ($\textit{A}$V$_{3}$Sb$_{5}$, $\textit{A}$ = K, Cs, Rb) exhibit time-reversal symmetry-breaking behaviors in the superconducting states. Among the three, the Josephson junctions structured Nb/K$_{1-x}$V$_{3}$Sb$_{5}$/Nb and RbV$_{3}$Sb$_{5}$ show magnetic hysteresis below the superconducting transition temperature. CsV$_{3}$Sb$_{5}$ exhibits a zero-field superconducting diode effect, meaning the magnitude of the positive and negative superconducting critical currents are different. We first discuss the similarities and differences among the three above-mentioned experiments. Then, we discuss the possible mechanisms responsible for the unconventional superconducting transport phenomena: such as a chiral superconducting order parameter, and chiral pair density waves arising from the intertwining of the chiral charge order with superconductivity.