Exciton-Scattering-Induced Dephasing in Two-Dimensional Semiconductors

TL;DR

This paper presents a microscopic theoretical framework for understanding excitation-induced dephasing (EID) in monolayer transition metal dichalcogenides, revealing exciton-exciton scattering as the key mechanism and aligning well with experimental data.

Contribution

It introduces a microscopic model based on excitonic Heisenberg equations to explain EID in exciton-dominated semiconductors, which was previously lacking.

Findings

Exciton-exciton scattering causes power-dependent linewidth broadening.

The model quantitatively matches recent experimental observations.

EID is identified as a dominant dephasing mechanism in these materials.

Abstract

Enhanced Coulomb interactions in monolayer transition metal dichalcogenides cause tightly bound electron-hole pairs (excitons) which dominate their linear and nonlinear optical response. The latter includes bleaching, energy renormalizations, and higher-order Coulomb correlation effects like biexcitons and excitation-induced dephasing (EID). While the first three are extensively studied, no theoretical footing for EID in exciton dominated semiconductors is available so far. In this study, we present microscopic calculations based on excitonic Heisenberg equations of motion and identify the coupling of optically pumped excitons to exciton-exciton scattering continua as the leading mechanism responsible for an optical power dependent linewidth broadening (EID) and sideband formation. Performing time-, momentum-, and energy-resolved simulations, we quantitatively evaluate the EID for the most common monolayer transition metal dichalcogenides and find an excellent agreement with recent experiments.