1. Key Laboratory of Magnetic Levitation Technologies and Maglev Trains, Ministry of Education, School of Electrical Engineering, Southwest Jiaotong University, Chengdu, Sichuan 610031, People’s Republic of China
2. School of Physical Science and Technology, Southwest Jiaotong University, Chengdu, Sichuan 610031, People’s Republic of China
3. Frontier Institute of Science and Technology (FIST), Xi’an Jiaotong University, Xi’an, Shaanxi 710049, People’s Republic of China
4. College of Physics and Energy, Fujian Normal University, Fuzhou, Fujian 350117, People’s Republic of China
5. Southwestern Institute of Physics, Chengdu, Sichuan 610041, People’s Republic of China