Ultrafast Nonequilibrium Enhancement of Electron-Phonon Interaction in 2H-MoTe$_2$

TL;DR

This study reveals that photoexcited carrier density can be used to ultrafast enhance electron-phonon interactions in 2H-MoTe2, providing insights into nonequilibrium coupling mechanisms in driven solids.

Contribution

It combines experimental ultrafast spectroscopy with theoretical analysis to show how carrier density tuning affects electron-phonon interactions in a transition-metal dichalcogenide.

Findings

Carrier density increases lead to band-gap renormalization.

Reduced population lifetimes at higher carrier densities.

Transient electron-phonon coupling modifications observed.

Abstract

Understanding nonequilibrium electron-phonon interactions at the microscopic level and on ultrafast timescales is a central goal of modern condensed matter physics. Combining time- and angle-resolved extreme ultraviolet photoemission spectroscopy with constrained density functional perturbation theory, we demonstrate that photoexcited carrier density can serve as a tuning knob to enhance electron-phonon interactions in nonequilibrium conditions. Specifically, nonequilibrium band structure mapping and valley-resolved ultrafast population dynamics in semiconducting transition-metal dichalcogenide 2H-MoTe$_2$ reveal band-gap renormalizations and reduced population lifetimes as photoexcited carrier densities increase. Through theoretical analysis of photoinduced electron and phonon energy and linewidth renormalizations, we attribute these transient features to nonequilibrium modifications of electron-phonon coupling matrix elements. The present study advances our understanding of microscopic coupling mechanisms enabling control over relaxation pathways in driven solids.