1. School of Physics, Sun Yat-Sen University, Guangzhou, 510275, China
2. Condensed Matter Physics & Materials Science Division, Brookhaven National Laboratory, Upton, New York, 11973, USA
3. Department of Materials Science & Engineering, National University of Singapore, 9 Engineering Drive 1, 117576, Singapore
4. Center for Terahertz Waves, College of Precision Instrument and Optoelectronics Engineering, Tianjin University, Key Laboratory of Optoelectronics Information and Technology (Ministry of Education), Tianjin, China
5. Singapore Synchrotron Light Source (SSLS), National University of Singapore, 5 Research Link, 117603, Singapore
6. Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000, P. R. China