1. Institute of Atomic and Molecular Physics, Sichuan University, Chengdu, Sichuan 610065, P. R. China
2. Quantum Solid-State Physics, Department of Physics and Astronomy, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
3. Engineering Research Center in Biomaterials, Sichuan University, Chengdu, Sichuan 610065, P. R. China
4. State Key Laboratory of Polymer Materials Engineering, Sichuan University, Chengdu, Sichuan 610065, P. R. China