1. Department of Physics, Xiamen University, Xiamen 361005, Fujian, China
2. CAS Key Laboratory of Theoretical Physics and Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190, China
3. Department of Physics, Tianshui Normal University, Tianshui 741001, Gansu, China
4. Lanzhou Center for Theoretical Physics, Key Laboratory of Theoretical Physics of Gansu Province, Lanzhou University, Lanzhou, Gansu 730000, China