Magnetochiral Tunneling in Paramagnetic Co$_{1/3}$NbS$_2$

TL;DR

This paper reports the discovery of magnetochiral tunneling in Co$_{1/3}$NbS$_2$, enabling atomic-scale imaging of chiral domains through current-induced magnetization detection.

Contribution

It introduces a novel tunneling phenomenon in a paramagnetic chiral material, linking electronic tunneling with magnetization and structural chirality detection.

Findings

Detection of magnetization induced by tunneling current in Co$_{1/3}$NbS$_2$

Atomic-scale contrast of chiral domains achieved

First-principles calculations support the mechanism

Abstract

Electric currents have the intriguing ability to induce magnetization in nonmagnetic crystals with sufficiently low crystallographic symmetry. Some associated phenomena include the non-linear anomalous Hall effect in polar crystals and the nonreciprocal directional dichroism in chiral crystals when magnetic fields are applied. In this work, we demonstrate that the same underlying physics is also manifested in the electronic tunneling process between the surface of a nonmagnetic chiral material and a magnetized scanning probe. In the paramagnetic but chiral metallic compound Co$_{1/3}$NbS$_2$, the magnetization induced by the tunneling current is shown to become detectable by its coupling to the magnetization of the tip itself. This results in a contrast across different chiral domains, achieving atomic-scale spatial resolution of structural chirality. To support the proposed mechanism, we used first-principles theory to compute the chirality-dependent current-induced magnetization and Berry curvature in the bulk of the material. Our demonstration of this magnetochiral tunneling effect opens up a new avenue for investigating atomic-scale variations in the local crystallographic symmetry and electronic structure across the structural domain boundaries of low-symmetry nonmagnetic crystals.