Charge fluctuations above TCDW revealed by glasslike thermal transport in kagome metals AV3Sb5

We present heat capacity, electrical, and thermal transport measurements of kagome metals $A{\mathrm{V}}_{3}{\mathrm{Sb}}_{5}$ $(A=\mathrm{K},\mathrm{Rb},\mathrm{Cs})$. In all three compounds, the development of short-range charge fluctuations above the charge density wave (CDW) transition temperature ${T}_{\mathrm{CDW}}$ strongly scatters phonons via the electron-phonon coupling, leading to the glasslike phonon heat transport, i.e., the 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 $A{\mathrm{V}}_{3}{\mathrm{Sb}}_{5}$.