Weyl Exceptional Rings in a Three-Dimensional Dissipative Cold Atomic Gas

TL;DR

This paper introduces a new topological feature called Weyl exceptional rings in dissipative cold atomic gases, characterized by exceptional points with quantized topological invariants, and proposes an experimental realization scheme.

Contribution

It reveals the existence of Weyl exceptional rings in dissipative systems, expanding topological phenomena beyond Hermitian systems.

Findings

Discovery of Weyl exceptional rings with quantized invariants

Characterization of these rings via Riemann surfaces

Proposed experimental scheme in cold atomic gases

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 (or line) 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 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.