Affiliation: | (1) Nanjing University, Department of Physics, National Laboratory of Solid State Microstructure, Center for Advanced Studies in Science and Technology of Microstructures, Nanjing 210093, P.R. China (Fax: +86-25/3300535, E-mail: snzhu@nju.edu.cn), CN;(2) National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093, P.R. China, CN;(3) CCAST (World Laboratory), P.O. Box 8730, Beijing 100080, P.R. China, CN |