Nanosculpted 3D helices of a magnetic Weyl semimetal with switchable nonreciprocity

TL;DR

This study demonstrates how nanosculpting 3D helices in a magnetic Weyl semimetal induces switchable nonreciprocal electron transport and magnetization switching, revealing new functionalities in quantum materials through geometrical engineering.

Contribution

The paper introduces 3D nanosculpting of a magnetic Weyl semimetal to control nonreciprocal transport and magnetization, expanding the exploration of symmetry-breaking effects in quantum materials.

Findings

Nanosculpted helices exhibit large, reversible diode effects.

High carrier mobility enhances asymmetrical boundary scattering.

Current-induced magnetization switching occurs without external magnetic fields.

Abstract

The emergent properties of materials are defined by the symmetries of their underlying atomic, spin and charge order. The explorations of symmetry breaking effects are therefore usually limited by the intrinsic properties of known, stable materials. In recent years, advances in focused ion beam (FIB) fabrication have enabled the nanostructuring of bulk crystals into ultraprecise transport devices [1-4], facilitating the investigation of geometrical effects on mesoscopic length scales. In this work, we expand such explorations into three-dimensional (3D), curvilinear shapes, by sculpting helical nanostructure devices from single crystals of the high-mobility, centrosymmetric magnetic Weyl semimetal Co$_3$Sn$_2$S$_2$ [5,6]. The combination of the imposed chiral geometry and intrinsic ferromagnetism yields nonreciprocal electron transport [7-9]. The high coercivity results in an anomalous, reversable diode effect remnant under zero applied magnetic field, which is orders of magnitude larger than can be explained by a classical self-field mechanism. We argue the enhancement originates from the high carrier mobility and the resulting quasi-ballistic transport: the conduction electron mean free path approaches the length scale of the curvature, resulting in increased asymmetrical scattering at the boundaries. We further demonstrate the inverse effect of the nonreciprocal transport: the field-free, current-induced switching of the magnetisation. The results establish the vast potential of 3D nanosculpting to explore and enrich the functionality of quantum materials.