Observation of Room-temperature Charge Density Wave Correlations via Coherent Phonon Spectroscopy in Sn-doped Kagome Superconductor CsV$_3$Sb$_5$

TL;DR

This study uses ultrafast spectroscopy to reveal persistent short-range charge density wave correlations at room temperature in Sn-doped CsV$_3$Sb$_5$, highlighting disorder's role in stabilizing these correlations beyond long-range order.

Contribution

It demonstrates that Sn doping induces static short-range CDW correlations that survive at room temperature, expanding understanding of disorder effects in Kagome superconductors.

Findings

Short-range CDW correlations persist up to room temperature.

Sn doping introduces quenched disorder that pins CDW.

Persistent CDW signatures are observed beyond phase boundary.

Abstract

In this work, we perform ultrafast time-resolved reflectivity measurements to track the evolution of charge density wave (CDW) correlations in Sn-doped Kagome superconductor CsV$_3$Sb$_{5-x}$Sn$_x$. By extracting the coherent phonon spectrum, we evidence robust signatures of CDW correlations at temperature and doping ranges far beyond the phase boundary of long-range CDW order. Remarkably, we unveil short-range CDW correlations survive up to room temperature in $x = 0.32$ Sn-doped CsV$_3$Sb$_5$, supported by synchrotron X-ray diffraction measurements. We point out the introduction of quenched disorder by Sn doping can pin the CDW and form static short-range CDW, which can explain the observed persistent CDW signatures. Our results thus corroborate the ubiquity and robustness of CDW correlations in Sn-doped CsV$_3$Sb$_5$ and provide new insights on the role of disorders on the CDW correlations in AV$_3$Sb$_5$ family.