Giant Valley Coherence at Room Temperature in 3R WS2 with Broken Inversion Symmetry

• Published in: Research (Washington) Vol. 2019; p. 6494565
• Main Authors: 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
• Format: Journal Article
• Language: English
• Published: AAAS 01.01.2019; American Association for the Advancement of Science (AAAS)
• ISSN: 2639-5274
• DOI: 10.34133/2019/6494565

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 2 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 2 at room temperature would provide a firm foundation for quantum manipulation of the valley degree of freedom and practical application of valleytronics.