1. Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada.
2. Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada.
3. Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
4. School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China.
5. Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY 11973, USA.
6. Department of Physics, Yale University, New Haven, CT 06520, USA.
7. Department of Applied Physics, Yale University, New Haven, CT 06520, USA.
8. Canadian Light Source, Saskatoon, Saskatchewan S7N 2V3, Canada.
9. Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China.