1. CAS Key Laboratory of Nanophotonic Materials and Devices CAS Key Laboratory of Standardization and Measurement for Nanotechnology CAS Center for Excellence in Nanoscience National Center for Nanoscience and Technology Beijing 100190 P. R. China
2. Sino‐Danish College University of Chinese Academy of Sciences Beijing 100049 P. R. China
3. School of Nanoscience and Technology University of Chinese Academy of Sciences Beijing 100049 P. R. China
4. Beijing National Laboratory for Molecular Sciences Key Laboratory of Organic Solids Institute of Chemistry Beijing 100190 P. R. China
5. ICFO‐Institut de Ciencies Fotoniques The Barcelona Institute of Science and Technology Castelldefels (Barcelona) 08860 Spain
6. Wenzhou Institute University of Chinese Academy of Sciences Wenzhou 325001 China
7. The Institute of Physics Chinese Academy of Sciences Beijing 100190 China
8. School of Physical Sciences University of Chinese Academy of Sciences Beijing 100049 P. R. China
9. Department of Electronics and Nanoengineering Aalto University Espoo FI‐02150 Finland
10. QTF Centre of Excellence Department of Applied Physics Aalto University Aalto FI‐00076 Finland
11. Department of Physics and Astronomy Stony Brook University Stony Brook NY 11794 USA
12. ICREA‐Institució Catalana de Recerca i Estudis Avançats Passeig Lluís Companys 23 Barcelona 08010 Spain