1. Hunan Key Laboratory of Two-Dimensional Materials, Department of Applied Physics, School of Physics and Electronics, Hunan University, Changsha 410082, China
2. Hunan Key Laboratory of Two-Dimensional Materials, State Key Laboratory for Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, China
3. School of Physics and Electronics, Central South University, Changsha 410083, China