# Low-Temperature Annihilation Rate for Quasi-Localized Excitons in Monolayer MoS2

## TL;DR

This paper investigates low-temperature exciton annihilation in monolayer MoS2, revealing dipole-dipole interactions leading to Auger-like recombination, modeled through localized excitons behaving fermionically and derived using Fermi's Golden Rule.

## Contribution

It introduces a model for exciton annihilation in monolayer MoS2 considering quasi-localized excitons and dipole interactions, deriving the recombination rate analytically.

## Key findings

- Excitons undergo dipole-dipole interaction leading to annihilation.
- The model predicts the recombination rate as a function of exciton density.
- Localized excitons behave fermionically due to their confinement.

## Abstract

The strong Coulomb forces in monolayer transition metal dichalcogenides ensure that optical excitation of band electrons gives rise to Wannier-Mott excitonic states, each of which can be conceptualized as a composite of a Gaussian wavepacket corresponding to center-of-mass motion and an orbital state corresponding to the motion of the electron and hole about the center-of-mass. Here, we show that at low temperature in monolayer MoS2, given quasi-localized excitons and consequently a significant inter-exciton spacing, the excitons undergo dipole-dipole interaction and annihilate one another in a manner analogous to Auger recombination. To construct our model, we assume that each exciton is localized in a region whose length is on the same scale as the excitonic diameter, thus causing the exciton to behave in a fermionic manner, while the distance between neighboring excitons is much larger than the exciton diameter. We construct the orbital ladder operators for each exciton and apply Fermi's Golden Rule to derive the overall recombination rate as a function of exciton density.