Trion-phonon interaction in atomically thin semiconductors

TL;DR

This paper models the microscopic trion-phonon interactions in monolayer semiconductors, revealing how these interactions influence trion dynamics, diffusion, and mobility, with implications for optoelectronic properties of 2D materials.

Contribution

It introduces a microscopic model of trion-phonon interactions in monolayer semiconductors and analyzes their effects on trion diffusion and mobility, especially at varying densities.

Findings

Trions diffuse less efficiently than excitons and electrons at low densities.

Increased trion density enhances diffusion due to fermionic pressure effects.

The model provides insights into trion dynamics relevant for 2D semiconductor applications.

Abstract

Optical and transport properties of doped monolayer semiconductors are dominated by trions, which are three-particle compounds formed by two electrons and one hole or vice versa. In this work, we investigate the trion-phonon interaction on a microscopic footing and apply our model to the exemplary case of a molybdenum diselenide (MoSe2) monolayer. We determine the trion series of states and their internal quantum structure by solving the trion Schr\"odinger equation. Transforming the system into a trion basis and solving equations of motion, including the trion-phonon interaction within the second-order Born-Markov approximation, provides a microscopic access to the trion dynamics. In particular, we investigate trion propagation and compute the diffusion coefficient and mobility. In the low density limit, we find that trions propagate less efficiently than excitons and electrons due to their stronger coupling with phonons and their larger mass. For increasing densities, we predict a drastic enhancement of diffusion caused by the build-up of a large pressure by the degenerate trion gas, which is a direct consequence of the fermionic character of trions. Our work provides microscopic insights into the trion-phonon interaction and its impact on the diffusion behaviour in atomically thin semiconductors.