Anisotropic resistance with a 90-degree twist in a ferromagnetic Weyl semimetal, Co2MnGa

TL;DR

This study reveals a unique 90-degree twist in resistance anisotropy in a ferromagnetic Weyl semimetal, Co2MnGa, linked to anisotropic surface states affecting electrical transport.

Contribution

It uncovers a novel 90-degree resistance anisotropy in Co2MnGa and attributes it to anisotropic surface states, supported by symmetry analysis and simulations.

Findings

Resistance anisotropy of about 10 times with 90-degree axis rotation.

Surface states impede hybridization with bulk, causing anisotropic transport.

Anisotropic surface states resemble an isotropic conductor with directional dependence.

Abstract

Co$_2$MnGa is a ferromagnetic semimetal with Weyl nodal lines identified by ARPES. We studied electrical transport in thin Co$_2$MnGa lamellae (10 $\times$ 10 $\times$ 0.4-5 microns) cut from single-crystals using a focused ion beam. These crystals exhibit an unexpected and highly unusual planar resistance anisotropy ($\sim$10 times) with principal axes that rotate by 90 degrees between the upper and lower faces. Using symmetry arguments and simulations, we find that the observed resistance anisotropy resembles that of an isotropic conductor with anisotropic surface states that are impeded from hybridization with bulk states. The origin of these states awaits further experiments that can correlate the surface bands with the observed 90$^\circ$-twist geometry.