# Diffusion quantum Monte Carlo study of excitonic complexes in two-dimensional transition-metal dichalcogenides

## TL;DR

This study uses diffusion quantum Monte Carlo to accurately compute binding energies of excitonic complexes in 2D transition-metal dichalcogenides, providing insights into their stability and spectral signatures.

## Contribution

It offers statistically exact binding energy data and classification of excitonic complexes in 2D semiconductors, enhancing interpretation of experimental spectra.

## Key findings

- Biexcitons are only bound when identical particles are much heavier.
- Donor/acceptor-bound biexcitons have energies similar to experimental values.
- Predicted spectral positions of excitonic complexes in WSe₂ and MoSe₂.

## Abstract

Excitonic effects play a particularly important role in the optoelectronic behavior of two-dimensional semiconductors. To facilitate the interpretation of experimental photoabsorption and photoluminescence spectra we provide (i) statistically exact diffusion quantum Monte Carlo binding-energy data for a Mott-Wannier model of (donor/acceptor-bound) excitons, trions, and biexcitons in two-dimensional semiconductors in which charges interact via the Keldysh potential, (ii) contact pair-distribution functions to allow a perturbative description of contact interactions between charge carriers, and (iii) an analysis and classification of the different types of bright trion and biexciton that can be seen in single-layer molybdenum and tungsten dichalcogenides. We investigate the stability of biexcitons in which two charge carriers are indistinguishable, finding that they are only bound when the indistinguishable particles are several times heavier than the distinguishable ones. Donor/acceptor-bound biexcitons have similar binding energies to the experimentally measured biexciton binding energies. We predict the relative positions of all stable free and bound excitonic complexes of distinguishable charge carriers in the photoluminescence spectra of WSe$_2$ and MoSe$_2$.