1. Joseph
Henry Laboratory, Department of Physics, Princeton University, Princeton, New Jersey 08544, United States
2. Department
of Physics, University of Illinois at Urbana—Champaign, 1110 West Green Street, Urbana, Illinois 61801-3080, United States
3. Department
of Materials Science and Engineering, University of Utah, Salt Lake City, Utah 84122, United States
4. College
of Science, Nanjing University of Science and Technology, Nanjing 210094, China
5. Frederick
Seitz Materials Research Laboratory, University of Illinois at Urbana—Champaign, 104 South Goodwin Avenue, Urbana, Illinois 61801-2902, United States
6. Collaborative Innovation Center of Quantum Matter, Beijing 100084, China