Valley Splitting and Polarization by Zeeman Effect in Monolayer MoSe2

Abstract

We have measured circularly polarization resolved photoluminescence in monolayer MoSe2 under magnetic fields up to 10 T in the Faraday geometry. The circularly polarized photoluminescence correspond to the emission from the K and K′ valleys, respectively. At low doping densities, the neutral and charged excitons shift linearly with field strength at a rate of \( \mp 0.12\;\mathrm{meV}/\mathrm{T} \) for emission arising from the two valleys, respectively. 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 \( \mp 0.18\;\mathrm{meV}/\mathrm{T} \). This enhancement is attributed to many-body effects on the binding energy of the charged excitons [1].