1. International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, P. R. China
2. Department of Physics, College of Science, Shihezi University, Shihezi 832003, PR China
3. Frontiers Science Center for High Energy Material (MOE), Beijing Institute of Technology, Beijing 100081, P. R. China
4. School of Physics, Beijing Institute of Technology, Beijing 100081, P. R. China