1. Department of Chemistry; National University of Singapore; 3 Science Drive 3 Singapore 117543 Singapore
2. NUS Graduate School for Integrative Sciences and Engineering; National University of Singapore; 13 Centre for Life Sciences, #05-01, 28 Medical Drive Singapore 117456 Singapore
3. Department of Materials Science and Engineering; National University of Singapore; 9 Engineering Drive 1 Singapore 117575 Singapore
4. School of Physical Sciences and CAS Center for Excellence in Topological Quantum Computation; University of Chinese Academy of Sciences; Beijing 100049 China