%0 Journal Article %T Valley polarization in MoS2 monolayers by optical pumping %A Hualing Zeng %A Junfeng Dai %A Wang Yao %A Di Xiao %A Xiaodong Cui %J Physics %D 2012 %I arXiv %R 10.1038/nnano.2012.95 %X We report experimental evidences on selective occupation of the degenerate valleys in MoS2 monolayers by circularly polarized optical pumping. Over 30% valley polarization has been observed at K and K' valley via the polarization resolved luminescence spectra on pristine MoS2 monolayers. It demonstrates one viable way to generate and detect valley polarization towards the conceptual valleytronics applications with information carried by the valley index. %U http://arxiv.org/abs/1202.1592v1