[1] Beijing Univ Technol, Fac Mat & Mfg, Beijing 100124, Peoples R China
[2] Beijing Univ Technol, Fac Informat Technol, Key Lab Optoelect Technol, Educ Minist China, Beijing 100124, Peoples R China
[3] Peking Univ, State Key Lab Mesoscop Phys, Beijing 100871, Peoples R China
[4] Peking Univ, Dept Phys, Beijing 100871, Peoples R China
[5] Collaborat Innovat Ctr Quantum Matter, Beijing 100871, Peoples R China