Charge fluctuations above $T_\mathrm{CDW}$ revealed by glasslike thermal transport in kagome metals $A$V$_3$Sb$_5$ ($A$ = K, Rb, Cs)

TL;DR

This study reveals that above the charge density wave transition temperature, kagome metals exhibit glasslike phonon thermal transport due to charge fluctuation-induced scattering, indicating strong electron-phonon coupling.

Contribution

It provides direct experimental evidence of charge fluctuation effects on phonon transport in kagome metals above $T_{CDW}$, highlighting the role of electron-phonon interactions.

Findings

Glasslike phonon thermal conductivity above $T_{CDW}$

Charge fluctuations strongly scatter phonons

Electron-phonon coupling is sizable in $A$V$_3$Sb$_5$

Abstract

We present heat capacity, electrical and thermal transport measurements of kagome metals $A$V$_3$Sb$_5$ ($A$ = K, Rb, Cs). In all three compounds, development of short-range charge fluctuations above the charge density wave (CDW) transition temperature $T_\mathrm{CDW}$ strongly scatters phonons via electron-phonon coupling, leading to glasslike phonon heat transport, i.e., phonon thermal conductivity decreases weakly upon cooling. Once the long-range charge order sets in below $T_\mathrm{CDW}$, short-range charge fluctuations are quenched, and the typical Umklapp scattering dominated phonon heat transport is recovered. The charge-fluctuations-induced glasslike phonon thermal conductivity implies sizable electron-phonon coupling in $A$V$_3$Sb$_5$.