title: Experimental Observation of a Topological Band Gap Opening in Ultracold Fermi Gases with Two-Dimensional Spin-Orbit Coupling.
abstract: The recent experimental realization of synthetic spin-orbit coupling (SOC) opens a new avenue for exploring novel quantum states with ultracold atoms. However, in experiments for generating two-dimensional SOC (e.g., Rashba type), a perpendicular Zeeman field, which opens a band gap at the Dirac point and induces many topological phenomena, is still lacking. Here, we theoretically propose and experimentally realize a simple scheme for generating two-dimensional SOC and a perpendicular Zeeman field simultaneously in ultracold Fermi gases by tuning the polarization of three Raman lasers that couple three hyperfine ground states of atoms. The resulting band gap opening at the Dirac point is probed using spin injection radio-frequency spectroscopy. Our observation may pave the way for exploring topological transport and topological superfluids with exotic Majorana and Weyl fermion excitations in ultracold atoms.
authors.affiliation: State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan 030006, People's Republic of China.|Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, People's Republic of China.
authors.forename: Zengming
authors.initials: Z
authors.lastname: Meng
authors.affiliation: State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan 030006, People's Republic of China.|Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, People's Republic of China.
authors.forename: Lianghui
authors.initials: L
authors.lastname: Huang
authors.affiliation: State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan 030006, People's Republic of China.
authors.forename: Peng
authors.initials: P
authors.lastname: Peng
authors.affiliation: State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan 030006, People's Republic of China.
authors.forename: Donghao
authors.initials: D
authors.lastname: Li
authors.affiliation: State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan 030006, People's Republic of China.
authors.forename: Liangchao
authors.initials: L
authors.lastname: Chen
authors.affiliation: Department of Physics, The University of Texas at Dallas, Richardson, Texas 75080-3021, USA.
authors.forename: Yong
authors.initials: Y
authors.lastname: Xu
authors.affiliation: Department of Physics, The University of Texas at Dallas, Richardson, Texas 75080-3021, USA.
authors.forename: Chuanwei
authors.initials: C
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan 030006, People's Republic of China.|Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, People's Republic of China.
authors.forename: Pengjun
authors.initials: P
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan 030006, People's Republic of China.|Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China.
authors.forename: Jing
authors.initials: J
authors.lastname: Zhang