Scaling of Berry-curvature monopole dominated large linear positive magnetoresistance

TL;DR

This paper presents a quantitative model linking large linear positive magnetoresistance in a ferromagnetic Weyl semimetal to Berry curvature monopoles, supported by experimental data and theoretical calculations, advancing understanding in topological spintronics.

Contribution

It introduces a scaling model connecting Berry curvature to magnetoresistance, validated by experiments on CoS2, a magnetic topological semimetal with record LPMR, and explains the underlying mechanism.

Findings

CoS2 exhibits over 500% LPMR at 2K and 9T.

The model relates MR to Berry curvature and magnetic field.

Experimental data supports the Berry-curvature monopole mechanism.

Abstract

The linear positive magnetoresistance (LPMR) is a widely observed phenomenon in topological materials, which is promising for potential applications on topological spintronics. However, its mechanism remains ambiguous yet and the effect is thus uncontrollable. Here, we report a quantitative scaling model that correlates the LPMR with the Berry curvature, based on a ferromagnetic Weyl semimetal CoS2 that bears the largest LPMR of over 500% at 2 Kelvin and 9 Tesla, among known magnetic topological semimetals. In this system, masses of Weyl nodes existing near the Fermi level, revealed by theoretical calculations, serve as Berry-curvature monopoles and low-effective-mass carriers. Based on the Weyl picture, we propose a relation \[\text{MR}=\frac{e}{\hbar }B{{\Omega }_{\text{F}}}\], with B being the applied magnetic field and \[{{\Omega }_{\text{F}}}\] the average Berry curvature near the Fermi surface, and further introduce temperature factor to both MR/B slope (MR per unit field) and anomalous Hall conductivity, which establishes the connection between the model and experimental measurements. A clear picture of the linearly slowing down of carriers, i.e., the LPMR effect, is demonstrated under the cooperation of the k-space Berry curvature and real-space magnetic field. Our study not only provides an experimental evidence of Berry curvature induced LPMR for the first time, but also promotes the common understanding and functional designing of the large Berry-curvature MR in topological Dirac/Weyl systems for magnetic sensing or information storage.