1. College of Materials Science and Opto-Electronic Technology & Center of Materials Science and Optoelectronics Engineering & CAS Center for Excellence in Topological Quantum Computation & CAS Key Laboratory of Vacuum PhysicsUniversity of Chinese Academy of Sciences Beijing 100049 P. R. China
2. Department of Chemical and Biochemical Engineering, Technical University of Denmark, Building 229, 2800 Kgs. Lyngby. Sino-Danish College, University of Chinese Academy of Sciences, Beijing, 100049, China.Sino-Danish center for Education and ResearchUniversity of Chinese Academy of Sciences Beijing 100049 China