Vortex phase diagram of kagome superconductor CsV$_3$Sb$_5$

TL;DR

This study maps the vortex phase diagram of the kagome superconductor CsV$_3$Sb$_5$ using ac mutual inductance, revealing complex vortex behaviors including peak effects, vortex glass phase, and pinning crossover.

Contribution

It provides the first detailed vortex phase diagram of CsV$_3$Sb$_5$, identifying vortex glass and pinning phenomena through combined ac inductance, resistance, and magnetization measurements.

Findings

Observation of peak effect and enhanced vortex pinning

Identification of vortex glass phase via hysteresis

Mapping of the H-T phase diagram and irreversibility line

Abstract

The screening response of vortices in kagome superconductor CsV$_3$Sb$_5$ was measured using the ac mutual inductance technique. Besides confirming the absence of gapless quasiparticles in zero external magnetic field, we observe the peak effect, manifested in enhanced vortex pinning strength and critical current, in a broad intermediate range of magnetic field. The peaks are followed by another crossover from strong to weak pinning, unlike the usual peak effect that diminishes smoothly at $H_{c2}$. Hysteresis in the screening response allows the identification of a vortex glass phase which strongly correlates with the onset of the peaks. A variety of features in the temperature- and field-dependence of the screening response, corroborated by resistance and dc magnetization measurements, have allowed us to extract an $H$-$T$ phase diagram of the vortex states and to infer the irreversibility line $H_\text{irr}(T)$.