[1] Peking Univ, Ctr Nanochem CNC, Beijing Natl Lab Mol Sci, Coll Chem & Mol Engn,Acad Adv Interdisciplinary S, Beijing 100871, Peoples R China
[2] Peking Univ, Coll Engn, Dept Mat Sci & Engn, Beijing 100871, Peoples R China
[3] Chinese Acad Sci, Natl Ctr Nanosci & Technol, Beijing 100190, Peoples R China
[4] Tsinghua Univ, Dept Phys, Beijing 100084, Peoples R China
[5] Tsinghua Univ, State Key Lab Low Dimens Quantum Phys, Beijing 100084, Peoples R China
[6] Tsinghua Univ, Inst Adv Study, Beijing 100084, Peoples R China