1. Division of Nanophotonics; 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. Laboratory of Nano Oxides for Sustainable Energy; Material Science and Engineering (MSE); King Abdullah University of Science & Technology (KAUST); Thuwal 23955-6900 Saudi Arabia
3. Department of Materials Science and Engineering; College of Engineering; Peking University; Beijing 100871 P. R. China
4. State Key Laboratory for Mesoscopic Physics & Department of Physics; Collaborative Innovation Center of Quantum Matter; Peking University; Beijing 100190 P. R. China