title: Anomalously robust valley polarization and valley coherence in bilayer WS2.
abstract: We report the observation of anomalously robust valley polarization and valley coherence in bilayer WS2. The polarization of the photoluminescence from bilayer WS2 follows that of the excitation source with both circular and linear polarization, and remains even at room temperature. The near-unity circular polarization of the luminescence reveals the coupling of spin, layer, and valley degree of freedom in bilayer system, and the linearly polarized photoluminescence manifests quantum coherence between the two inequivalent band extrema in momentum space, namely, the valley quantum coherence in atomically thin bilayer WS2. This observation provides insight into quantum manipulation in atomically thin semiconductors.
authors: Physics Department, University of Hong Kong, Hong Kong 999077, China;
authors: Bairen
authors: B
authors: Zhu
authors: Physics Department, Chinese University of Hong Kong, Hong Kong 999077, China; and hualingzeng@hotmail.com xdcui@hku.hk.
authors: Hualing
authors: H
authors: Zeng
authors: Physics Department, South University of Science and Technology of China, Shenzhen 518055, China.
authors: Junfeng
authors: J
authors: Dai
authors: Physics Department, University of Hong Kong, Hong Kong 999077, China;
authors: Zhirui
authors: Z
authors: Gong
authors: Physics Department, University of Hong Kong, Hong Kong 999077, China; hualingzeng@hotmail.com xdcui@hku.hk.
authors: Xiaodong
authors: X
authors: Cui
keywords: spin–valley coupling; valley quantum control; valleytronics