[1] Tsinghua Univ, Inst Adv Study, Beijing 100084, Peoples R China
[2] Univ Calif Santa Barbara, Kavli Inst Theoret Phys, Santa Barbara, CA 93106 USA
[3] Tsinghua Univ, Dept Phys, Beijing 100084, Peoples R China
[4] Tsinghua Univ, State Key Lab Low Dimens Quantum Phys, Beijing 100084, Peoples R China
[5] Chinese Acad Sci, Beijing Natl Lab Condensed Matter Phys, Beijing 100190, Peoples R China
[6] Chinese Acad Sci, Inst Phys, Beijing 100190, Peoples R China
[7] Univ Chinese Acad Sci, Beijing 100049, Peoples R China
[8] Hefei Natl Lab, Hefei 230088, Peoples R China