[1] Univ Elect Sci & Technol China, State Key Lab Elect Thin Film & Integrated Device, Chengdu 610054, Peoples R China
[2] Peking Univ, Sch Phys, State Key Lab Mesoscop Phys, Collaborat Innovat Ctr Quantum Matter, Beijing 100871, Peoples R China
[3] Fudan Univ, State Key Lab Surface Phys, Key Lab Micro & Nano Photon Struct MOE, Dept Phys, Shanghai 200433, Peoples R China
[4] Fudan Univ, Inst Nanoelect Devices & Quantum Comp, Key Lab Micro & Nano Photon Struct MOE, State Key Lab Surface Phys, Shanghai 200433, Peoples R China