Zeeman Splitting and Inverted Polarization of Biexciton Emission in Monolayer WS2

TL;DR

This study explores how magnetic fields affect biexciton emissions in monolayer WS2, revealing a specific g factor, inverted polarization behavior, and the importance of dark excitons in these many-body states.

Contribution

It provides the first detailed analysis of Zeeman splitting and polarization inversion in biexcitons in monolayer WS2, highlighting the role of dark excitons.

Findings

Biexciton g factor of -3.89 matches neutral exciton

Inverted circular polarization observed under magnetic field

Dark excitons are crucial in biexciton composition

Abstract

We investigate the magnetic-field-induced splitting of biexcitons in monolayer WS$_2$ using polarization-resolved photoluminescence spectroscopy in out-of-plane magnetic fields up to 30 T. The observed $g$ factor of the biexciton amounts to $-3.89$, closely matching the $g$ factor of the neutral exciton. The biexciton emission shows an inverted circular field-induced polarization upon linearly polarized excitation, i.e. it exhibits preferential emission from the high-energy peak in a magnetic field. This phenomenon is explained by taking into account the configuration of the biexciton constituents in momentum space and their respective energetic behavior in magnetic fields. Our findings reveal the critical role of dark excitons in the composition of this many-body state.