Negative magnetoresistance in strained $\alpha$-Sn and $\alpha$-SnGe films in an in-plane magnetic field

TL;DR

This study investigates negative magnetoresistance in strained -Sn and -SnGe films, finding results inconsistent with the chiral anomaly hypothesis and suggesting alternative mechanisms.

Contribution

It provides new experimental data on magnetotransport in strained -Sn and -SnGe films, challenging the chiral anomaly explanation for negative MR.

Findings

Negative MR observed in both -Sn and -SnGe films.

Results are inconsistent with the chiral anomaly hypothesis.

Sample design and material quality may influence MR observations.

Abstract

To test the hypothesis that the chiral anomaly is responsible for negative magnetoresitance (MR) in \atn{}, we have studied magnetotransport in strained, epitaxial films of pure \aSn{} and the alloy \aSnGe{} that are in the Dirac semimetal and 3D topological insulator state, respectively. We have observed for both states a negative MR with current either parallel or transverse to the in-plane magnetic field, but with a different dependence of MR on $\vec{B}$ strength. Our results are inconsistent with the chiral anomaly and suggest that other mechanisms may be responsible for negative MR in the Dirac/Weyl semimetal phase of \aSn{}. We also discuss several factors in sample design and material quality that may be contributing to the incongruous observations of MR reported in studies of strained \atn{} films.