[1
]Department of Physics and Astronomy, University of California, Riverside, California
92521, United States
[2
]International Center for Quantum Materials, School of Physics, Peking University,
Beijing 100871, P. R. China
[3
]National Laboratory of Solid State Microstructures, Department of Materials Science
and Engineering, College of Engineering and Applied Sciences, and Collaborative Innovation
Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
[4
]Department of Physics and Astronomy, University of California, Irvine, California
92697, United States