# Topological Gapless Matters in Three-dimensional Ultracold Atomic Gases

## TL;DR

This review summarizes recent advances in topological gapless phenomena in three-dimensional ultracold atomic gases, highlighting Weyl and Dirac points, nodal rings, and the role of interactions in these systems.

## Contribution

It provides a comprehensive overview of the experimental and theoretical progress in realizing and studying topological gapless states in cold atom systems.

## Key findings

- Identification of Weyl and Dirac points in cold atom systems
- Observation of nodal rings and Weyl exceptional rings
- Control of interactions via Feshbach resonances enhances topological phases

## Abstract

Three-dimensional topological gapless matters with gapless degeneracies protected by a topological invariant defined over a closed manifold in momentum space have attracted considerable interest in various fields ranging from condensed matter materials to ultracold atomic gases. As a highly controllable and disorder free system, ultracold atomic gases provide a versatile platform to simulate topological gapless matters. Here, the current progress in studies of topological gapless phenomena in three-dimensional cold atom systems is summarized in the review. It is mainly focused on Weyl points, structured (type-II) Weyl points, Dirac points, nodal rings and Weyl exceptional rings in cold atoms. Since interactions in cold atoms can be controlled via Feshbach resonances, the progress in both superfluids for attractive interactions and non-interacting cold atom gases is reviewed.