Chiral charge transfer along magnetic field lines in a Weyl superconductor

Abstract

Three-dimensional Weyl fermions have a definite chirality, given by the ± sign in the Weyl Hamiltonian ±p ·σ. Three spatial dimensions are essential, if p ·σ = pxσx+pyσy contains only two Pauli matrices, then +p·σ and −p ·σ can be transformed into each other by a unitary transformation (conjugation with σz). The chirality is therefore a characteristic feature of 3D Weyl semimetals, not shared by 2D graphene. The search for observable signatures of chirality is a common theme in the study of this new class of materials [1–4]. The basic mechanism used for that purpose is the chirality dependent motion in a magnetic field: Weyl fermions in the zeroth Landau level propagate parallel or antiparallel to the field lines, dependent on their chirality [5]. A population imbalance between the two chiralities then produces the chiral magnetic effect [6, 7]: An electrical current along the field lines, which changes sign if the field is inverted. Here we present a novel, albeit less dramatic, signature of chirality: An electrical conductance which depends on the magnetic field direction. The effect appears if super-