1. School of Integrated Circuits and Electronics, MIIT Key Laboratory for Low-Dimensional Quantum Structure and Devices, Beijing Institute of Technology, Beijing 100081, China
2. School of Automation, Beijing Information Science and Technology University, Beijing 100085, China
3. Centre for Advanced 2D Materials, National University of Singapore, 117546 Singapore
4. Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China