# Gigantic negative magnetoresistance in a disordered topological insulator

## TL;DR

This paper reports a giant negative magnetoresistance of 98% in a disordered topological insulator, revealing a new disorder-related mechanism supported by simulations, distinct from magnetic or chiral anomaly effects.

## Contribution

It introduces a novel disorder-induced mechanism for large negative MR in topological insulators, expanding understanding beyond magnetic and chiral anomaly origins.

## Key findings

- Gigantic negative MR of 98% at 14 T and 10 K in TlBi0.15Sb0.85Te2
- Numerical simulations suggest Zeeman effect on disordered current paths as the cause
- Disorder engineering can induce large negative MR in narrow-gap systems

## Abstract

With the recent discovery of Weyl semimetals, the phenomenon of negative magnetoresistance (MR) is attracting renewed interest. While small negative MR can occur due to the suppression of spin scattering or weak localization, large negative MR is rare in materials, and when it happens, it is usually related to magnetism. The large negative MR in Weyl semimetals is peculiar in that it is unrelated to magnetism and comes from chiral anomaly. Here we report that there is a new mechanism for large negative MR which is not related to magnetism but is related to disorder. In the newly-synthesized bulk-insulating topological insulator TlBi$_{0.15}$Sb$_{0.85}$Te$_2$, we observed gigantic negative MR reaching 98% in 14 T at 10 K, which is unprecedented in a nonmagnetic system. Supported by numerical simulations, we argue that this phenomenon is likely due to the Zeeman effect on a barely percolating current path formed in the disordered bulk. Since disorder can also lead to non-saturating linear MR in Ag$_{2+\delta}$Se, the present finding suggests that disorder engineering in narrow-gap systems is useful for realizing gigantic MR in both positive and negative directions.