Unpaired Weyl nodes from Long-Ranged Interactions: Fate of Quantum Anomalies

TL;DR

This paper explores how long-range interactions in Weyl semimetals can create unpaired Weyl nodes, challenging the fermion doubling theorem, and examines the robustness of the chiral anomaly and surface states under these conditions.

Contribution

It demonstrates the possibility of unpaired Weyl nodes induced by interactions and analyzes their impact on quantum anomalies and surface states, which is novel compared to non-interacting models.

Findings

Unpaired Weyl nodes can be realized with long-range interactions.

The chiral anomaly persists even with a single Weyl node under weak magnetic fields.

Long-range interactions modify topologically protected Fermi-arc surface states.

Abstract

We study the effect of long-ranged interactions on Weyl semimetals. Such interactions can give rise to unpaired Weyl nodes, which we demonstrate by explicitly constructing a system with just a single node - a situation that is fundamentally forbidden by fermion doubling in non-interacting band structures. Adding a magnetic field, we investigate the fate of the chiral anomaly. Remarkably, as long as a system exhibits a single Weyl node in the absence of magnetic fields, arbitrarily weak fields qualitatively restore the lowest Landau level structure of a non-interacting Weyl semimetal. This underlines the universality of the chiral anomaly in the context of Weyl semimetals. We furthermore demonstrate how the topologically protected Fermi-arc surface states are modified by long-ranged interactions.