作者机构:[1]State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing 100861, China, [2]Center for Applied Physics and Technology, Peking University, Beijing 100861, China
相关基金:Project supported by the National Natural Science Foundation of China (Grant No. 10675009).Acknowledgement The authors thank Professor Zhao Zi-Qiang for insightful discussion.