Wei Jiang^1,2, A-Min Tong², Ji-Qiang Gu², Xi-Ze Dong², Shui-Ming Hu^1,2, Zheng-Tian Lu^1,2, Florian Ritterbusch^1,2 and Guo-Min Yang^1,2, (1)Hefei National Laboratory for Physical Sciences at the Microscale, Hefei, China, (2)University of Science and Technology of China (USTC), Hefei, China