Bistability of electron temperature in atomically thin semiconductors in the presence of exciton photogeneration

TL;DR

This paper investigates how continuous photogeneration and charge interactions in monolayer transition metal dichalcogenides lead to a bistable electron temperature state, with rapid switching affecting optical and electronic properties.

Contribution

It reveals a novel bistability in electron temperature caused by exciton and trion dynamics under continuous photogeneration in 2D semiconductors.

Findings

Bistability occurs between low and high-temperature states.

Switching times are on the order of tens to hundreds of picoseconds.

Observable jumps in temperature, current, and luminescence accompany state transitions.

Abstract

We study the dynamic equilibrium between trions and excitons in monolayers of transition metal dichalcogenides in the presence of resident charge carriers and continuous photogeneration of excitons. We show that heating of the system via Drude absorption of low-frequency radiation leads to bistability of the steady-state equilibrium. The first is a low-temperature state, in which almost all resident charge carriers are bound into trions. The second state occurs at high temperatures, where most trions are dissociated; in this regime, the heating is more efficient due to the higher Drude conductivity of unbound charge carriers compared to trions. Switching between these two states occurs on a timescale of tens to hundreds of picoseconds and is accompanied by a jump in various observables such as temperature, current, and the intensity of exciton or trion luminescence.