Ultrafast Dynamics of the Topological Semimetal GdSb$_{x}$Te$_{2-x-\delta}$ In the Presence and Absence of a Charge Density Wave

TL;DR

This study investigates the ultrafast electronic responses of GdSb$_{x}$Te$_{2-x- ext{delta}}$ materials, revealing how charge density waves influence their dynamics and providing insights for future ultrafast research on CDW systems.

Contribution

It demonstrates the tunability of ultrafast dynamics in GdSb$_{x}$Te$_{2-x- ext{delta}}$ by adjusting Fermi level and CDW presence, highlighting the effects of Sb content and excitation conditions.

Findings

Spectral features shift with Sb content and excitation energy.

Enhanced transient lifetime when CDW is suppressed.

Evidence of photo-induced transient CDW suppression.

Abstract

Time-resolved dynamics in charge-density-wave materials have revealed interesting out-of-equilibrium electronic responses. However these are typically only performed in a single material possessing a CDW. As such, it is challenging to separate subtle effects originating from the CDW. Here, we report on the ultrafast dynamics of the GdSb$_{x}$Te$_{2-x-\delta}$ series of materials where E$_{F}$ can be tuned, resulting in a change from an undistorted tetraganal phase to a CDW with a wavevector that depends on $x$. Using mid-infrared, near-infrared, and visible excitation, we find the dynamics are sensitive to both E$_{F}$ and the presence of the CDW. Specifically, as the Sb content of the compounds increases, transient spectral features shift to higher probe energies. In addition, we observe an enhanced lifetime and change in the sign of the transient signal upon removing the CDW with high Sb concentrations. Finally, we reveal fluence- and temperature-dependent photo-induced responses of the differential reflectivity, which provide evidence of transient charge density wave suppression in related telluride materials. Taken together our results provide a blueprint for future ultrafast studies of CDW systems.