1. Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
2. Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190, China
3. Department of Physics and Astronomy, University of Waterloo, Waterloo N2L 3G1, Canada
4. Perimeter Institute for Theoretical Physics, Waterloo, Ontario N2L 2Y5, Canada
5. Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China