Surface to bulk Fermi arcs via Weyl nodes as topological defects

Kun Woo Kim,Woo-Ram Lee,Yong Baek Kim,Kwon Park

doi:10.1038/ncomms13489

Kun Woo Kim, Woo-Ram Lee + Show 2 more

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https://doi.org/10.1038/ncomms13489

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Abstract

A hallmark of Weyl semimetal is the existence of surface Fermi arcs. An intriguing question is what determines the connectivity of surface Fermi arcs, when multiple pairs of Weyl nodes are present. To answer this question, we show that the locations of surface Fermi arcs are predominantly determined by the condition that the Zak phase integrated along the normal-to-surface direction is . The Zak phase can reveal the peculiar topological structure of Weyl semimetal directly in the bulk. Here, we show that the winding of the Zak phase around each projected Weyl node manifests itself as a topological defect of the Wannier–Stark ladder, energy eigenstates under an electric field. Remarkably, this leads to bulk Fermi arcs, open-line segments in the bulk spectra. Bulk Fermi arcs should exist in conjunction with surface counterparts to conserve the Weyl fermion number under an electric field, which is supported by explicit numerical evidence.

Highlights

A hallmark of Weyl semimetal is the existence of surface Fermi arcs
We provide an argument that the existence of bulk Fermi arcs is required to conserve the Weyl fermion number under an electric field, which is supported by explicit numerical evidence
We argue that the existence of bulk Fermi arcs is required to conserve the Weyl fermion number under an electric field

Summary

Introduction

A hallmark of Weyl semimetal is the existence of surface Fermi arcs. An intriguing question is what determines the connectivity of surface Fermi arcs, when multiple pairs of Weyl nodes are present. We show that the winding of the Zak phase around each projected Weyl node manifests itself as a topological defect of the Wannier–Stark ladder, energy eigenstates under an electric field. This leads to bulk Fermi arcs, open-line segments in the bulk spectra. We show that, in Weyl semimetal, the Zak phase winds by 2p around each projected Weyl node, creating a screw dislocation in the energy spectrum of WSL eigenstates These topological defects induce open-line segments in the momentum spectra of WSL, which we call bulk Fermi arcs. We provide an argument that the existence of bulk Fermi arcs is required to conserve the Weyl fermion number under an electric field, which is supported by explicit numerical evidence

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