[1] Calif State Univ Northridge, Dept Phys & Astron, Northridge, CA 91330 USA
[2] Westlake Univ, Sch Sci, Key Lab Quantum Mat Zhejiang Prov, Hangzhou 310024, Peoples R China
[3] Beihang Univ, Dept Phys, Beijing 100191, Peoples R China
[4] SLAC, Stanford Inst Mat & Energy Sci, Menlo Pk, CA 94025 USA
[5] Stanford Univ, Menlo Pk, CA 94025 USA