1. Department of Materials Science and Engineering, Southern University of Science and Technology (SUSTech), Shenzhen 518055, P. R. China
2. Department of Physics, The Hong Kong University of Science and Technology (HKUST), Clear Water Bay, Kowloon, Hong Kong 999077, P. R. China
3. College of Science, Hohai University, Nanjing 210098, P. R. China
4. Center for Infrastructure Engineering, Western Sydney University, Kingswood, New South Wales 2751, Australia
5. Key Laboratory of Advanced Materials of Ministry of Education, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China