Controlling exciton many-body states by the electric-field effect in monolayer MoS$_2$

TL;DR

This study uses high magnetic field magneto-optical spectroscopy to explore how electric fields influence many-body exciton states in monolayer MoS₂, revealing transitions from neutral excitons to polaronic states with specific spin-valley characteristics.

Contribution

It provides new insights into the many-body interactions of excitons in monolayer MoS₂ under high magnetic fields and varying charge doping levels, highlighting the transition from neutral excitons to polaronic states.

Findings

Valley Zeeman shift depends on local carrier concentration.

Magneto-optical response varies with Landau level occupation.

Excitons transition into polaronic states away from charge neutrality.

Abstract

We report magneto-optical spectroscopy of gated monolayer MoS$_2$ in high magnetic fields up to 28T and obtain new insights on the many-body interaction of neutral and charged excitons with the resident charges of distinct spin and valley texture. For neutral excitons at low electron doping, we observe a nonlinear valley Zeeman shift due to dipolar spin-interactions that depends sensitively on the local carrier concentration. As the Fermi energy increases to dominate over the other relevant energy scales in the system, the magneto-optical response depends on the occupation of the fully spin-polarized Landau levels in both $K/K^{\prime}$ valleys. This manifests itself in a many-body state. Our experiments demonstrate that the exciton in monolayer semiconductors is only a single particle boson close to charge neutrality. We find that away from charge neutrality it smoothly transitions into polaronic states with a distinct spin-valley flavour that is defined by the Landau level quantized spin and valley texture.