Valley Splitting and Polarization by the Zeeman Effect in Monolayer MoSe2

TL;DR

This study investigates how magnetic fields influence valley splitting and polarization in monolayer MoSe2, revealing Zeeman shifts, valley degeneracy lifting, and many-body effects on exciton binding energies.

Contribution

It provides experimental evidence of valley splitting and polarization effects in monolayer MoSe2 under magnetic fields, including the role of doping levels and many-body interactions.

Findings

Zeeman shifts of .12 meV/T and .18 meV/T for neutral and charged excitons

Magnetic field induces valley polarization and lifts valley degeneracy

Many-body effects enhance Zeeman shifts at high doping levels

Abstract

We have measured circularly polarized photoluminescence in monolayer MoSe2 under perpendicular magnetic fields up to 10 T. At low doping densities, the neutral and charged excitons shift linearly with field strength at a rate of $\mp$ 0.12 meV/T for emission arising, respectively, from the K and K' valleys. The opposite sign for emission from different valleys demonstrates lifting of the valley degeneracy. The magnitude of the Zeeman shift agrees with predicted magnetic moments for carriers in the conduction and valence bands. The relative intensity of neutral and charged exciton emission is modified by the magnetic field, reflecting the creation of field-induced valley polarization. At high doping levels, the Zeeman shift of the charged exciton increases to $\mp$ 0.18 meV/T. This enhancement is attributed to many-body effects on the binding energy of the charged excitons.