Geometrically protected triple-point crossings in an optical lattice

TL;DR

This paper proposes a method to realize topologically protected triple-point crossings of energy bands in 3D optical lattices using existing ultracold atom techniques, enabling exploration of novel topological phenomena.

Contribution

It introduces a new way to create and observe spin-1 Weyl points and tilted triple-point crossings in optical lattices, which are not yet seen in solid-state materials.

Findings

Isolated triple-point crossings (TPCs) can be realized with existing ultracold atom techniques.

The symmetries allow for the existence of type-II, or tilted, TPCs.

Spin-1 Weyl points are within experimental reach in ultracold atom systems.

Abstract

We show how to realize topologically protected crossings of three energy bands, integer-spin analogs of Weyl fermions, in three-dimensional optical lattices. Our proposal only involves ultracold atom techniques that have already been experimentally demonstrated and leads to isolated triple-point crossings (TPCs) which are required to exist by a novel combination of lattice symmetries. The symmetries also allow for a new type of topological object, the type-II, or tilted, TPC. Our Rapid Communication shows that spin-1 Weyl points, which have not yet been observed in the bandstructure of crystals, are within reach of ultracold atom experiments.