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

Area of Science:

• Condensed Matter Physics
• Topological Materials
• Quantum Mechanics

Background:

• Topological Weyl semimetals feature Weyl points or nodal rings in momentum space.
• These topological features are typically found in conservative systems.

Purpose of the Study:

• To discover and characterize novel topological structures in dissipative systems.
• To introduce the concept of a Weyl exceptional ring.
• To propose an experimental realization of this new topological object.

Main Methods:

• Theoretical investigation of dissipative systems with particle gain and loss.
• Characterization of topological properties using quantized Chern numbers and Berry phases defined on a Riemann surface.
• Proposal of an experimental scheme using cold atomic gases in an optical lattice.

Main Results:

• Discovery of a new topological ring structure, the Weyl exceptional ring.
• Demonstration that this ring is characterized by both a quantized Chern number and a quantized Berry phase.
• Identification of exceptional points where two eigenstates coalesce as key features of the ring.

Conclusions:

• Weyl exceptional rings represent a new class of topological objects in non-Hermitian systems.
• The proposed experimental scheme provides a viable pathway for observing these novel topological phenomena.
• This work extends the understanding of topological phases into dissipative quantum systems.