1. School of Physical Science and Technology Jiangsu Key Laboratory of Thin Films Soochow University Suzhou 215006 China
2. Institute of Theoretical and Applied Physics Soochow University Suzhou 215006 China
3. Institute of Physics Chinese Academy of Sciences Beijing 100190 China
4. Singapore Synchrotron Light Source National University of Singapore 5 Research Link Singapore 117603 Singapore
5. Department of Physics Guangdong Provincial Key Laboratory of Functional Oxide Materials and Devices Southern University of Science and Technology Guangdong Shenzhen 518055 China