Probing biexciton in monolayer WS$_2$ through controlled many-body interaction

TL;DR

This study investigates the charged biexciton in monolayer WS$_2$, demonstrating controlled manipulation and revealing insights into its binding energy and recombination processes through experimental and theoretical analysis.

Contribution

It provides the first systematic experimental and theoretical analysis of the charged biexciton in monolayer WS$_2$, including its dependence on external parameters and recombination mechanisms.

Findings

Charged biexciton binding energy is less than its spectral separation from neutral exciton.

Recombination of charged biexciton is less restricted by the light cone compared to neutral exciton.

Experimental data combined with a rate equation model elucidate biexciton properties.

Abstract

The monolayers of semiconducting transition metal dichalcogenides host strongly bound excitonic complexes and are an excellent platform for exploring many-body physics. Here we demonstrate a controlled kinetic manipulation of the five-particle excitonic complex, the charged biexciton, through a systematic dependence of the biexciton peak on excitation power, gate voltage, and temperature using steady-state and time-resolved photoluminescence (PL). With the help of a combination of the experimental data and a rate equation model, we argue that the binding energy of the charged biexciton is less than the spectral separation of its peak from the neutral exciton. We also note that while the momentum-direct radiative recombination of the neutral exciton is restricted within the light cone, such restriction is relaxed for a charged biexciton recombination due to the presence of near-parallel excited and final states in the momentum space.