1. Department of Physics, University of Science and Technology of China, Hefei 230026, China
2. International Center for Quantum Design of Functional Materials/Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230026, China
3. Department of Physics and Astronomy and the IQ Initiative, University of Pittsburgh, Pittsburgh, PA 15260
4. Hefei National Laboratory, University of Science and Technology of China, Hefei 230088, China