Observation of an unexpected negative magnetoresistance in magnetic Weyl semimetal Co$_3$Sn$_2$S$_2$

TL;DR

This study reports an unexpected negative magnetoresistance in the magnetic Weyl semimetal Co$_3$Sn$_2$S$_2$, revealing complex interplay between magnetic, topological, and transport properties, with implications for understanding magnon-electron interactions.

Contribution

It provides the first detailed investigation of magnetotransport in Co$_3$Sn$_2$S$_2$ micro-ribbons, highlighting unexpected anisotropic negative MR and its origin in magnon-electron coupling.

Findings

Magnetoresistance up to 1% with strong anisotropy.

Unexpected negative MR attributed to magnon-electron coupling.

Angular dependence linked to Hall effects.

Abstract

Time-reversal symmetry breaking allows for a rich set of magneto-transport properties related to electronic topology. Focusing on the magnetic Weyl semimetal Co$_3$Sn$_2$S$_2$, we prepared micro-ribbons and investigated their transverse and longitudinal transport properties from 100 K to 180 K in magnetic fields $\mu_0 H$ up to 2T. We establish the presence of a magnetoresistance (MR) up to 1 % with a strong anisotropy depending the projection of $H$ on the easy-axis magnetization, which exceeds all other magnetoresistive effects. Based on detailed phenomenological modeling, we attribute the observed results with unexpected form of anisotropy to magnon MR resulting from magnon-electron coupling. Moreover, a similar angular dependence is also found in the transverse resistivity which we show to originate from the combination of ordinary Hall and anomalous Hall effects. Thus the interplay of magnetic and topological properties governs the magnetotransport features of this magnetic Weyl system.