1. Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
2. Department of Materials Science, Fudan University, Shanghai 200433, China
3. World Premier International Research Centers Initiative (WPI), Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
4. ESRF-The European Synchrotron, CS 40220, Grenoble 38043 Cedex 9, France
5. Univ Lyon, Université Claude Bernard Lyon 1, CNRS, Institut Lumière Matière, Villeurbanne 69622, France
6. Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China
7. Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China