Radiative Lifetimes of Excitons and Trions in Monolayers of Metal Dichalcogenide MoS2

TL;DR

This paper investigates the radiative lifetimes of excitons and trions in monolayer MoS2, revealing how these lifetimes depend on temperature, localization, and momentum, with implications for other 2D materials.

Contribution

The study provides detailed theoretical predictions of exciton and trion radiative lifetimes in monolayer MoS2, highlighting their dependence on temperature, localization, and momentum, applicable to similar 2D materials.

Findings

Exciton lifetimes are 0.18-0.30 ps for small in-plane momenta.

Thermally distributed exciton lifetimes depend linearly on temperature.

Trion lifetimes are in the hundreds of picoseconds and increase with momentum.

Abstract

We present results on the radiative lifetimes of excitons and trions in a monolayer of metal dichalcogenide MoS2. The small exciton radius and the large exciton optical oscillator strength result in radiative lifetimes in the 0.18-0.30 ps range for excitons that have small in-plane momenta and couple to radiation. Average lifetimes of thermally distributed excitons depend linearly on the exciton temperature and can be in the few picoseconds range at small temperatures and more than a nanosecond near room temperature. Localized excitons exhibit lifetimes in the same range and the lifetime increases as the localization length decreases. The radiative lifetimes of trions are in the hundreds of picosecond range and increase with the increase in the trion momentum. Average lifetimes of thermally distributed trions increase with the trion temperature as the trions acquire thermal energy and larger momenta. We expect our theoretical results to be applicable to most other 2D transition metal dichalcogenides.