1. College of Physics Science, Qingdao University, Qingdao 266071, People’s Republic of China
2. National Laboratory of Solid State Microstructures, Physics School, Nanjing University, Nanjing 210093, People’s Republic of China
3. College of Electronic and Information Engineering, Qingdao University, Qingdao 266071, People’s Republic of China
4. School of Materials Science and Physics, China University of Mining and Technology, Xuzhou 221116, China