Du Luojun, Tang Jian, Liang Jing, Liao Mengzhou, Jia Zhiyan, Zhang Qinghua, Zhao Yanchong, Yang Rong, Shi Dongxia, Gu Lin, Xiang Jianyong, Liu Kaihui, Sun Zhipei, Zhang Guangyu
Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
Department of Electronics and Nanoengineering, Aalto University, Tietotie 3, FI-02150, Finland.
Research (Wash D C). 2019 Oct 13;2019:6494565. doi: 10.34133/2019/6494565. eCollection 2019.
Breaking the space-time symmetries in materials can markedly influence their electronic and optical properties. In 3R-stacked transition metal dichalcogenides, the explicitly broken inversion symmetry enables valley-contrasting Berry curvature and quantization of electronic angular momentum, providing an unprecedented platform for valleytronics. Here, we study the valley coherence of 3R WS large single-crystal with thicknesses ranging from monolayer to octalayer at room temperature. Our measurements demonstrate that both A and B excitons possess robust and thickness-independent valley coherence. The valley coherence of direct A (B) excitons can reach 0.742 (0.653) with excitation conditions on resonance with it. Such giant and thickness-independent valley coherence of large single-crystal 3R WS at room temperature would provide a firm foundation for quantum manipulation of the valley degree of freedom and practical application of valleytronics.
打破材料中的时空对称性会显著影响其电学和光学性质。在3R堆叠的过渡金属二卤化物中，明显打破的反演对称性使谷对比度的贝里曲率和电子角动量量子化成为可能，为谷电子学提供了一个前所未有的平台。在此，我们研究了室温下厚度从单层到八层的3R WS大单晶的谷相干性。我们的测量表明，A和B激子都具有稳健且与厚度无关的谷相干性。直接A（B）激子在与共振激发条件下的谷相干性可达0.742（0.653）。室温下大单晶3R WS这种巨大且与厚度无关的谷相干性将为谷自由度的量子操控和谷电子学的实际应用提供坚实基础。
