1. Beijing National Laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences Beijing 100190 China
2. Physics and Optoelectronic Engineering College Guangdong University of Technology Guangzhou 510006 China
3. School of Materials Science and Engineering Tongji University Shanghai 201804 China
4. Department of Materials Science and Engineering Northwestern University Evanston IL 60208 USA
5. Department of Physics and TcSUH University of Houston Houston TX 77204 USA