Double Weyl points and Fermi arcs of topological semimetals in non-Abelian gauge potentials

TL;DR

This paper investigates how non-Abelian gauge potentials modify topological semimetals with Weyl points, revealing the emergence of double monopoles and analyzing surface Fermi arcs, with implications for ultracold atom experiments.

Contribution

It demonstrates the transformation of Weyl points into double monopoles under non-Abelian gauge fields and analyzes their surface states and stability.

Findings

Weyl points become quadratic and form double monopoles with non-Abelian fields

Surface Fermi arcs are characterized and their stability is analyzed

System remains robust under certain symmetry-breaking perturbations

Abstract

We study the effect of a non-Abelian SU(2) gauge potential on the topological semimetal induced by a magnetic field having {\pi}-flux per plaquette and acting on fermions in a cubic lattice. The Abelian {\pi}-flux term gives rise to a spectrum characterized by Weyl points. When the non-Abelian part is turned on, due to the presence of a C4 rotation symmetry, the Weyl points assume a quadratic dispersion along two directions and constitute double monopoles for the Berry curvature. We examine both analytically and numerically the main features of this system, focusing on its gapless surface modes, the so-called Fermi arcs. We discuss the stability of the system under confining hard-wall and harmonic potentials, relevant for the implementation in ultracold atom settings, and the effect of rotation symmetry breaking.