Electronic Correlations and Evolution of the Charge-Density Wave in the Kagome Metals $A$V$_{3}$Sb$_{5}$ ($A$ = K, Rb, Cs)

TL;DR

This study investigates how electronic correlations influence the charge-density wave and superconductivity in kagome metals $A$V$_{3}$Sb$_{5}$, revealing that increased correlations suppress CDW while enhancing superconductivity across the alkali-metal series.

Contribution

It provides new insights into the role of electronic correlations in modulating the intertwined CDW and superconductivity in $A$V$_{3}$Sb$_{5}$ compounds.

Findings

CDW gap increases with alkali-metal radius from K to Cs

$T_{CDW}$ first rises then drops, contrary to conventional CDW behavior

Enhanced electronic correlations in CsV$_{3}$Sb$_{5}$ suppress CDW but boost superconductivity

Abstract

The kagome metals $A$V$_{3}$Sb$_{5}$ ($A$ = K, Rb, Cs) have attracted enormous interest as they exhibit intertwined charge-density wave (CDW) and superconductivity. The alkali-metal dependence of these characteristics contains pivotal information about the CDW and its interplay with superconductivity. Here, we report optical studies of $A$V$_{3}$Sb$_{5}$ across the whole family. With increasing alkali-metal atom radius from K to Cs, the CDW gap increases monotonically, whereas $T_{\text{CDW}}$ first rises and then drops, at variance with conventional CDW. While the Fermi surface gapped by the CDW grows, $T_{c}$ is elevated in CsV$_{3}$Sb$_{5}$, indicating that the interplay between the CDW and superconductivity is not simply a competition for the density of states near \EF. More importantly, we observe an enhancement of electronic correlations in CsV$_{3}$Sb$_{5}$, which suppresses the CDW but enhances superconductivity, thus accounting for the above peculiar observations. Our results suggest electronic correlations as an important factor in manipulating the CDW and its entanglement with superconductivity in $A$V$_{3}$Sb$_{5}$.