1. Department of Physics, State Key Laboratory of Surface Physics, the Key Laboratory of Micro- and Nano-Photonic Structures (Ministry of Education), Fudan University, Shanghai, China
2. Department of Physics, State Key Laboratory of Surface Physics, the Key Laboratory of Micro- and Nano-Photonic Structures (Ministry of Education), Institute for Nanoelectronic Devices and Quantum Computing, Fudan University, Shanghai, China