Dirac semimetal PdTe2 temperature-dependent quasiparticle dynamics and electron-phonon coupling

TL;DR

This study investigates the temperature-dependent quasiparticle and phonon dynamics in PdTe2, revealing distinct relaxation processes and phonon mode behaviors that shed light on its electron-phonon interactions and superconductivity.

Contribution

It provides the first detailed analysis of ultrafast carrier and phonon relaxation processes in PdTe2 across a wide temperature range, highlighting electron-phonon coupling effects.

Findings

Fast subpicosecond electron-phonon thermalization process identified

Phonon modes soften with increasing temperature, affecting superconductivity

Two vibrational modes (E_g and A_1g) were characterized across temperatures

Abstract

Dirac semimetal PdTe2 single-crystal temperature-dependent ultrafast carrier and phonon dynamics were studied using ultrafast optical pump-probe spectroscopy. Two distinct carrier and coherent phonons relaxation processes were identified in the 5 K - 300 K range. Quantitative analysis revealed a fast relaxation process ({\tau}_f) occurring on a subpicosecond time scale which originated from electron-phonon thermalization. This was followed by a slower relaxation process ({\tau}_s) with a time scale of ~ 7-9.5 ps which originated from phonon-assisted electron-hole recombination. Two significant vibrational modes resolved at all measured temperatures and corresponded to Te atoms in-plane (E_g), and out-of-plane (A_1g), motion. As temperature increased both phonon modes softened markedly. A_1g mode frequency monotonically decreased as temperature increased. Its damping rate remained virtually unchanged. As expected, E_g decreased uniformly as temperatures rose. At temperatures above 80 K, there was insignificant change. Test results suggested that pure dephasing played an important role in the relaxation processes. PdTe2 phonon is thought responsible for its superconductive properties. Examining phonons behavior should improve the understanding of its complex superconductivity.