1. Zhejiang CHINT Electrics Co., Ltd. Shanghai 201600 P. R. China
2. Department of Physics Xi'an Jiaotong‐Liverpool University Suzhou 215123 P. R. China
3. Department of Applied Mathematics Xi'an Jiaotong‐Liverpool University Suzhou 215123 P. R. China
4. Department of Mathematical Sciences University of Liverpool Liverpool L69 7ZL UK
5. School of Nano‐Tech and Nano‐Bionics University of Science and Technology of China Hefei 230026 P. R. China