1. Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY 11973, USA.
2. Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117576, Singapore.
3. Center for Ultrafast Science and Technology, School of Chemistry and Chemical Engineering, Collaborative Innovation Center of IFSA, Shanghai Jiao Tong University, Shanghai 200240, China.
4. Physical Biology Center for Ultrafast Science and Technology, Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, CA 91125, USA.