[1] Chinese Acad Sci, Inst Phys, Beijing Natl Lab Condensed Matter Phys, Beijing 100190, Peoples R China
[2] Chinese Acad Sci, Natl Space Sci Ctr, Beijing 100190, Peoples R China
[3] Univ Punjab, Ctr Excellence Solid State Phys, Lahore 54590, Pakistan
[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