Trions in MoS$_2$ are quantum superpositions of intra- and intervalley spin states

TL;DR

This study uses high magnetic field magneto-photoluminescence spectroscopy and ab initio calculations to reveal that trions in MoS$_2$ monolayers are quantum superpositions of inter- and intravalley spin states, emphasizing exchange interactions' role.

Contribution

It provides the first detailed experimental and theoretical analysis showing trions as quantum superpositions of valley states in MoS$_2$, advancing understanding of exciton physics in 2D semiconductors.

Findings

Identification of three trion resonances not explained by single-particle models.

Demonstration of quantum superpositions of inter- and intravalley spin states.

Highlighting the significance of exchange interactions in monolayer MoS$_2$.

Abstract

We report magneto-photoluminescence spectroscopy of gated MoS$_2$ monolayers in high magnetic fields to 28 T. At B = 0T and electron density $n_s\sim 10^{12}cm^-2$, we observe three trion resonances that cannot be explained within a single-particle picture. Employing ab initio calculations that take into account three-particle correlation effects as well as local and non-local electron-hole exchange interaction, we identify those features as quantum superpositions of inter- and intravalley spin states. We experimentally investigate the mixed character of the trion wave function via the filling factor dependent valley Zeeman shift in positive and negative magnetic fields. Our results highlight the importance of exchange interactions for exciton physics in monolayer MoS$_2$ and provide new insights into the microscopic understanding of trion physics in 2D multi-valley semiconductors for low excess carrier densities.