1. Institute for Superconducting and Electronic Materials (ISEM), Australian Institute for Innovative Materials (AIIM), UOW-Beihang Joint Research Centre, University of Wollongong, Wollongong, NSW 2525, Australia.
2. Beihang-UOW Joint Research Centre and School of Physics, Beihang University, Beijing 10191, P. R. China.
3. School of Physics, Nankai University, Tianjin 300071, P. R. China.
4. University of Chinese Academy of Sciences, Beijing 100049, P. R. China.
5. Institute of Physics, Chinese Academy of Sciences, Beijing 100190, P. R. China.