title: Topological Superradiant States in a Degenerate Fermi Gas.
abstract: We predict the existence of a topological superradiant state in a two-component degenerate Fermi gas in a cavity. The superradiant light generation in the transversely driven cavity mode induces a cavity-assisted spin-orbit coupling and opens a bulk gap at half filling. This mechanism can simultaneously drive a topological phase transition in the system, yielding a topological superradiant state. We map out the steady-state phase diagram in the presence of an effective Zeeman field, and identify a critical tetracritical point beyond which the topological and the conventional superraidiant phase boundaries separate. The topological phase transition can be detected from its signatures in either the momentum distribution of the atoms or the variation of the cavity photon occupation due to the nontrivial feedback of the atoms on the cavity field.
authors.affiliation: Key Laboratory of Quantum Information, University of Science and Technology of China, CAS, Hefei, Anhui 230026, China.|Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.
authors.forename: Jian-Song
authors.initials: JS
authors.lastname: Pan
authors.affiliation: International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China.|Collaborative Innovation Center of Quantum Matter, Beijing 100871, China.
authors.forename: Xiong-Jun
authors.initials: XJ
authors.lastname: Liu
authors.affiliation: Department of Physics, Renmin University of China, Beijing 100872, China.|Beijing Key Laboratory of Opto-electronic Functional Materials and Micro-nano Devices, Renmin University of China, Beijing 100872, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Quantum Information, University of Science and Technology of China, CAS, Hefei, Anhui 230026, China.|Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Yi
authors.affiliation: Key Laboratory of Quantum Information, University of Science and Technology of China, CAS, Hefei, Anhui 230026, China.|Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.
authors.forename: Guang-Can
authors.initials: GC
authors.lastname: Guo