1. School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, People's Republic of China
2. Electrical and Computer Engineering, Harold Frank Hall, Room 4155, University of California, Santa Barbara, California 93106-9560, USA
3. Institute of Superconducting and Electrical Materials, Australian Institute of Innovative Materials, University of Wollongong, Wollongong, NSW 2522, Australia