Affiliation: | (1) National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093, P.R. China (Fax: +86-25/3300-535, E-mail: yqlu@nju.edu.cn), CN;(2) CCAST (World Laboratory), P.O. 8730, Beijing 100080, and National Laboratory of Solid State Microstructures, Nanjing 210093, P.R. China, CN |