Valley polarization in MoS2 monolayers by optical pumping

Valley polarization in MoS2 monolayers by optical pumping

| Hualing Zeng†1, Junfeng Dai†1,3, Wang Yao1, Di Xiao2, Xiaodong Cui1*
The paper reports experimental evidence of valley polarization in MoS₂ monolayers using circularly polarized optical pumping. Over 30% valley polarization is observed in the polarization-resolved luminescence spectra of pristine MoS₂ monolayers, demonstrating the feasibility of optical valley control. This finding is significant for integrated valleytronics and spintronics applications, as it leverages the discrete degrees of freedom provided by degenerate valleys in momentum space. The valley polarization is attributed to the valley-dependent optical selection rules arising from inversion symmetry breaking in MoS₂ monolayers, which is not present in bilayers due to their hexagonal symmetry. The study also shows that the valley polarization decays with temperature, indicating inter-valley scattering dominated by acoustic phonons at high temperatures.The paper reports experimental evidence of valley polarization in MoS₂ monolayers using circularly polarized optical pumping. Over 30% valley polarization is observed in the polarization-resolved luminescence spectra of pristine MoS₂ monolayers, demonstrating the feasibility of optical valley control. This finding is significant for integrated valleytronics and spintronics applications, as it leverages the discrete degrees of freedom provided by degenerate valleys in momentum space. The valley polarization is attributed to the valley-dependent optical selection rules arising from inversion symmetry breaking in MoS₂ monolayers, which is not present in bilayers due to their hexagonal symmetry. The study also shows that the valley polarization decays with temperature, indicating inter-valley scattering dominated by acoustic phonons at high temperatures.
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