Breaking of Valley Degeneracy by Magnetic Field in Monolayer MoSe2

David, MacNeill and Colin, Heikes and Kin, Fai Mak and Zachary, Anderson and Kormányos, Andor and Zólyomi, Viktor and Jiwoong, Park and Daniel, C Ralph (2015) Breaking of Valley Degeneracy by Magnetic Field in Monolayer MoSe2. PHYSICAL REVIEW LETTERS, 114 (3). ISSN 0031-9007

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Abstract

Using polarization-resolved photoluminescence spectroscopy, we investigate breaking of valley degeneracy by out-of-plane magnetic field in back-gated monolayer MoSe2 devices. We observe a linear splitting of −0.22 meV T between luminescence peak energies in σ+ and σ− emission for both neutral and charged excitons. The optical selection rules of monolayer MoSe2 couple photon handedness to the exciton valley degree of freedom, so this splitting demonstrates valley degeneracy breaking. In addition, we find that the luminescence handedness can be controlled with magnetic field, to a degree that depends on the back-gate voltage. An applied magnetic field therefore provides effective strategies for control over the valley degree of freedom.

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