Spin-Valley Locking Effect in Defect States of Monolayer MoS2

Yaqian Wang; Longjiang Deng; Qilin Wei; Yi Wan; Zhen Liu; Xiao Lu; Yue Li; Lei Bi; Li Zhang; Haipeng Lu; Haiyan Chen; Peiheng Zhou; Linbo Zhang; Yingchun Cheng; Xiaoxu Zhao; Yu Ye; Wei Huang; Stephen John Pennycook; Kian Ping Loh; Bo Peng

doi:10.1021/acs.nanolett.0c00138

Spin-Valley Locking Effect in Defect States of Monolayer MoS₂

Nano Lett. 2020 Mar 11;20(3):2129-2136. doi: 10.1021/acs.nanolett.0c00138. Epub 2020 Feb 24.

Authors

Yaqian Wang^{1

2}, Longjiang Deng^{1

2}, Qilin Wei³, Yi Wan⁴, Zhen Liu^{1

2}, Xiao Lu^{1

2}, Yue Li^{1

2}, Lei Bi^{1

2}, Li Zhang^{1

2}, Haipeng Lu^{1

2}, Haiyan Chen^{1

2}, Peiheng Zhou^{1

2}, Linbo Zhang^{1

2}, Yingchun Cheng³, Xiaoxu Zhao⁵, Yu Ye⁴, Wei Huang³, Stephen John Pennycook⁵, Kian Ping Loh⁶, Bo Peng^{1

2}

Affiliations

¹ National Engineering Research Center of Electromagnetic Radiation Control Materials, School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China.
² State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 611731, China.
³ Key Laboratory of Flexible Electronics and Institute of Advanced Materials, Nanjing Tech University, Nanjing 211816, China.
⁴ State Key Laboratory for Artificial Microstructure and Mesoscopic Physics, Frontiers Center for Nano-optoelectronics, School of Physics, Peking University, Beijing 100871, China.
⁵ Department of Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, 117575, Singapore.
⁶ Department of Chemistry and Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, 117549, Singapore.

PMID: 32078769
DOI: 10.1021/acs.nanolett.0c00138

Abstract

Valley pseudospin in two-dimensional (2D) transition-metal dichalcogenides (TMDs) allows optical control of spin-valley polarization and intervalley quantum coherence. Defect states in TMDs give rise to new exciton features and theoretically exhibit spin-valley polarization; however, experimental achievement of this phenomenon remains challenges. Here, we report unambiguous valley pseudospin of defect-bound localized excitons in CVD-grown monolayer MoS₂; enhanced valley Zeeman splitting with an effective g-factor of -6.2 is observed. Our results reveal that all five d-orbitals and the increased effective electron mass contribute to the band shift of defect states, demonstrating a new physics of the magnetic responses of defect-bound localized excitons, strikingly different from that of A excitons. Our work paves the way for the manipulation of the spin-valley degrees of freedom through defects toward valleytronic devices.

Keywords: defect engineering; defect exciton; spin manipulation; spintronic; valleytronic.