Negative magnetoresistance due to conductivity fluctuations in films of the topological semimetal Cd3As2

TL;DR

This study shows that conductivity fluctuations in Cd3As2 thin films cause negative magnetoresistance and positive transverse magnetoresistance, challenging the interpretation that these effects are solely due to chiral anomaly in Dirac semimetals.

Contribution

It demonstrates that conductivity fluctuations, not chiral anomaly, can explain negative magnetoresistance in Cd3As2 thin films, providing an alternative explanation for magnetotransport phenomena.

Findings

Conductivity fluctuations cause negative magnetoresistance.

Both positive and negative magnetoresistance are explained without chiral anomaly.

Magnetoresistance characteristics correlate with film thickness and temperature-dependent carrier properties.

Abstract

Recently discovered Dirac and Weyl semimetals display unusual magnetoresistance phenomena, including a large, non-saturating, linear transverse magnetoresistance and a negative longitudinal magnetoresistance. The latter is often considered as evidence of fermions having a defined chirality. Classical mechanisms, due to disorder or non-uniform current injection, can however, also produce negative longitudinal magnetoresistance. Here, we report on magnetotransport measurements performed on epitaxial thin films of Cd3As2, a three-dimensional Dirac semimetal. Quasi-linear positive transverse magnetoresistance and negative longitudinal magnetoresistance are observed. By evaluating films of different thickness and by correlating the temperature dependence of the carrier density and mobility with the magnetoresistance characteristics, we demonstrate that both the quasi-linear positive and the negative magnetoresistance are caused by conductivity fluctuations. Chiral anomaly is not needed to explain the observed features.