Competing superconductivity and charge-density wave in Kagome metal CsV3Sb5: evidence from their evolutions with sample thickness

TL;DR

This study investigates how superconductivity and charge-density wave (CDW) in CsV3Sb5 Kagome metals evolve with sample thickness, revealing a competition between these phases driven by a dimensional crossover.

Contribution

It provides the first detailed analysis of the thickness-dependent evolution of superconductivity and CDW in CsV3Sb5, demonstrating their competing nature and the influence of dimensional crossover.

Findings

CDW transition temperature decreases then increases with decreasing thickness

Superconducting transition temperature shows opposite trend to CDW

Evidence of competition between superconductivity and CDW phases

Abstract

Recently superconductivity and topological charge-density wave (CDW) were discovered in the Kagome metals $A$V$_3$Sb$_5$ ($A$ = Cs, Rb, and K), which have an ideal Kagome lattice of vanadium. Here we report resistance measurements on thin flakes of CsV$_3$Sb$_5$ to investigate the evolution of superconductivity and CDW with sample thickness. The CDW transition temperature ${\it T}_{\rm CDW}$ decreases from 94 K in bulk to a minimum of 82 K at thickness of 60 nm, then increases to 120 K as the thickness is reduced further to 4.8 nm (about five monolayers). Since the CDW order in CsV$_3$Sb$_5$ is quite three-dimensional (3D) in the bulk sample, the non-monotonic evolution of ${\it T}_{\rm CDW}$ with reducing sample thickness can be explained by a 3D to 2D crossover around 60 nm. Strikingly, the superconducting transition temperature ${\it T}_{\rm c}$ shows an exactly opposite evolution, increasing from 3.64 K in the bulk to a maximum of 4.28 K at thickness of 60 nm, then decreasing to 0.76 K at 4.8 nm. Such exactly opposite evolutions provide strong evidence for competing superconductivity and CDW, which helps us to understand these exotic phases in $A$V$_3$Sb$_5$ Kagome metals.