1. Joint School of National University of Singapore and Tianjin University, International Campus of Tianjin University, Binhai New City, Fuzhou 350207, China
2. Department of Chemistry, National University of Singapore, Singapore 117543, Singapore
3. Department of Physics, National University of Singapore, Singapore 117551, Singapore
4. School of Mathematics and Physics, University of Science and Technology Beijing, Beijing 100083, China
5. Department of Applied Physics, The Hong Kong Polytechnic University, Kowloon 999077, Hong Kong, China
6. Institute of Physical Chemistry of Romanian Academy, Splaiul Independentei 202, Bucharest 060021, Romania
7. Consiglio Nazionale delle Ricerche, Institute for Superconducting and Innovative Materials and Devices (CNR-SPIN), c/o Department of Physical and Chemical Sciences, University of L’Aquila, Via Vetoio, I-67100 Coppito, L’Aquila, Italy