Exciton-Polaritons Dynamics of a Monolayer Tungsten Disulphide (WS2) Coupled to a Semiconductor Microcavity

TL;DR

This paper models exciton-polariton dynamics in a monolayer WS2 microcavity, highlighting the effects of cavity detuning, radiative lifetime, and excitation power on polariton relaxation and occupation.

Contribution

It introduces a theoretical model that describes polariton kinetics in WS2 microcavities, emphasizing the role of radiative lifetime and cavity detuning in polariton behavior.

Findings

UP branch can be tuned from excitonlike to photonlike with detuning.

Faster UP lifetime leads to efficient relaxation into LP states.

Nonlinear polariton behavior observed at high pump rates.

Abstract

We present a theoretical model that allows us to describe the dynamics of exciton polaritons in the strong-coupling regime in a monolayer WS2 based semiconductor microcavity. Numerical simulations using Boltzmann equations give an overall description of polariton kinetics over a temperature range of 130-230K, under nonresonant excitation. Here, only the scattering rate via optical phonons (LO) from the upper (UP) towards lower (LP) polariton branches is considered. According this model we show the importance of the radiative lifetime of the polaritonic states relative to polariton relaxation rate. Our results show as the cavity detuning changes from negative (130 K) to positive (230 K) values, the UP branch can be tuned from a more excitonlike to a more photonlike state at small wave vector k. We deduce that the UP states have a faster lifetime and the polariton relaxation time into the LP energy states becomes very efficient. Thus, the UP occupation starts to decrease, and we observe a simultaneous increase in the occupation of the LP branch. Furthermore, the polariton states are less occupied for small excitation pump rate, the calculated behavior is linear. In the high pumping regime, we observe the nonlinear behavior of cavity polaritons and occupation factors much larger than unity are reached.