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It is theoretically predicted that the valley degeneracy in transition metal dichalcogenides (TMDs) can be removed using relatively small magnetic fields if the film is on a magnetic substrate [1], [2]. Recent experiments demonstrate the proximity-induced exchange splitting in monolayer TMDs on magnetic substrates such as EuS [3] and CrI₃ [4]. We report systematic magneto-optical measurements on a TMD film that is grown on the magnetic substrate YIG (yttrium iron garnet). We perform photoluminescence (PL) measurements using a visible laser (E_pump = 2.33 eV) as a function of magnetic fields up to 7T at 10K. We observe an enhanced magnetic field dependence of the PL peak splitting of 0.42 meV/T for the charged exciton, compared to a smaller splitting with SiO₂ substrates of 0.1~0.2 meV/T. We observe a linear magnetic field dependence of the PL polarization and PL peak positions of the neutral exciton, charged exciton and local states.
[1] J. Qi et al., Phys. Rev. B 92, 121403(R) (2015)
[2] B. Scharf et al., Phys. Rev. Lett. 119, 127403 (2017)
[3] C. Zhao et al., Nat. Nanotechnol. 12, 757 (2017)
[4] D. Zhong et al., Sci. Adv. 3(5), e1603113 (2017)