1. Department of Physics, University of Surrey, Guildford, Surrey GU2 7XH, United Kingdom
2. Department of Electrical and Electronic Engineering, University of Surrey, Guildford, Surrey GU2 7XH, United Kingdom
3. School of Materials Science and Engineering, Hubei University, Wuhan 430062, People's Republic of China
4. Joule Physics Laboratory, School of Computing Science and Engineering, University of Salford, Salford M5 4WT, United Kingdom