title: Weyl Exceptional Rings in a Three-Dimensional Dissipative Cold Atomic Gas.
abstract: Three-dimensional topological Weyl semimetals can generally support a zero-dimensional Weyl point characterized by a quantized Chern number or a one-dimensional Weyl nodal ring characterized by a quantized Berry phase in the momentum space. Here, in a dissipative system with particle gain and loss, we discover a new type of topological ring, dubbed a Weyl exceptional ring consisting of exceptional points at which two eigenstates coalesce. Such a Weyl exceptional ring is characterized by both a quantized Chern number and a quantized Berry phase, which are defined via the Riemann surface. We propose an experimental scheme to realize and measure the Weyl exceptional ring in a dissipative cold atomic gas trapped in an optical lattice.
authors.affiliation: Department of Physics, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors.forename: Yong
authors.initials: Y
authors.lastname: Xu
authors.affiliation: Department of Physics, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors.forename: Sheng-Tao
authors.initials: ST
authors.lastname: Wang
authors.affiliation: Department of Physics, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors.forename: L-M
authors.initials: LM
authors.lastname: Duan