Charge-tuneable biexciton complexes in monolayer WSe$_{2}$

TL;DR

This paper reports the experimental observation and control of neutral and negatively charged biexciton complexes in monolayer WSe₂, revealing their internal structure and fine-structure splitting, advancing understanding of multi-particle exciton states.

Contribution

It provides the first direct experimental evidence of biexcitons in monolayer WSe₂ and demonstrates bias-controlled switching between different biexciton states.

Findings

Identification of neutral and charged biexcitons in monolayer WSe₂

Bias-controlled switching between biexciton states

Resolution of a 2.5 meV fine-structure splitting

Abstract

Multi-exciton states such as biexcitons, albeit theoretically predicted, have remained challenging to identify in atomically thin transition metal dichalcogenides so far. Here, we use excitation-power, electric-field and magnetic-field dependence of photoluminescence to report direct experimental evidence of two biexciton complexes in monolayer tungsten diselenide: the neutral and the negatively charged biexciton. We demonstrate bias-controlled switching between these two states, we determine their internal structure and we resolve a fine-structure splitting of 2.5 meV for the neutral biexciton. Our results unveil multi-particle exciton complexes in transition metal dichalcogenides and offer direct routes to their deterministic control in many-body quantum phenomena.