1. School of Physics, State Key Laboratory of Optoelectronic Materials and Technologies, Guangdong Provincial Key Laboratory of Photovoltaics Technologies, Sun Yat-sen University, Guangzhou 510006, People's Republic of China
2. Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
3. School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
4. Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China