Topological Lifshitz transitions and Fermi arc manipulation in Weyl semimetal NbAs

H F Yang,M Schmidt,D Prabhakaran,B A Bernevig,L X Yang,B H Yan,Y L Chen,H Peng,Z K Liu,Y Sun,C Chen,C Felser

doi:10.1038/s41467-019-11491-4

Abstract

Surface Fermi arcs (SFAs), the unique open Fermi-surfaces (FSs) discovered recently in topological Weyl semimetals (TWSs), are unlike closed FSs in conventional materials and can give rise to many exotic phenomena, such as anomalous SFA-mediated quantum oscillations, chiral magnetic effects, three-dimensional quantum Hall effect, non-local voltage generation and anomalous electromagnetic wave transmission. Here, by using in-situ surface decoration, we demonstrate successful manipulation of the shape, size and even the connections of SFAs in a model TWS, NbAs, and observe their evolution that leads to an unusual topological Lifshitz transition not caused by the change of the carrier concentration. The phase transition teleports the SFAs between different parts of the surface Brillouin zone. Despite the dramatic surface evolution, the existence of SFAs is robust and each SFA remains tied to a pair of Weyl points of opposite chirality, as dictated by the bulk topology.

Highlights

Surface Fermi arcs (SFAs), the unique open Fermi-surfaces (FSs) discovered recently in topological Weyl semimetals (TWSs), are unlike closed FSs in conventional materials and can give rise to many exotic phenomena, such as anomalous surface Fermi arcs (SFAs)-mediated quantum oscillations, chiral magnetic effects, three-dimensional quantum Hall effect, non-local voltage generation and anomalous electromagnetic wave transmission
The unusual SFAs and their interplay with bulk Weyl fermions can result in many exotic physical phenomena, such as anomalous SFA-mediated quantum oscillations[6,7,8,9] (Fig. 1b), the realization of chiral magnetic effects, 3D quantum Hall effect[15], novel quasiparticle interference in tunneling spectroscopy[16,17,18,19], intriguing non-local voltage generation (Fig. 1c) and unusual electromagnetic wave transmission[20,21,22,23] (Fig. 1d), and the emergence of Majorana modes when coupled with superconductivity[24]
The crystal can be naturally cleaved between two adjacent Nb-As layers to yield a flat (001) surface ideal for angle-resolved photoemission spectroscopy (ARPES) measurements

Summary

Introduction

Surface Fermi arcs (SFAs), the unique open Fermi-surfaces (FSs) discovered recently in topological Weyl semimetals (TWSs), are unlike closed FSs in conventional materials and can give rise to many exotic phenomena, such as anomalous SFA-mediated quantum oscillations, chiral magnetic effects, three-dimensional quantum Hall effect, non-local voltage generation and anomalous electromagnetic wave transmission. FSs form closed shapes, such as closed curves in two-dimensional (2D) electronic systems or closed surfaces in three-dimensional (3D) electronic systems This orthodoxy was recently upended by the theoretical and experimental discovery of a new type of quantum state–the topological Weyl semimetal (TWS), in which open FSs—surface Fermi arcs (SFAs)—emerge[1,2,3,4,5].

Methods

Results

Conclusion