Negative longitudinal magnetoresistance in the density wave phase of Y$_2$Ir$_2$O$_7$

TL;DR

This study reports negative longitudinal magnetoresistance in Y$_2$Ir$_2$O$_7$ nanowires, attributed to the chiral anomaly in its Weyl semimetal phase, contrasting with positive magnetoresistance under transverse fields.

Contribution

It provides evidence of chiral anomaly effects in the density wave phase of Y$_2$Ir$_2$O$_7$, linking magnetoresistance behavior to Weyl semimetal properties.

Findings

Negative longitudinal magnetoresistance observed.

Magnetic field influences the density wave depinning threshold.

Chiral anomaly likely causes the negative magnetoresistance.

Abstract

The ground state of nanowires of single crystalline Pyrochlore Y$_2$Ir$_2$O$_7$ is a density wave. Application of a {\it transverse} magnetic field increases the threshold electric field for the collective de-pinning of the density wave state at low temperature, leading to colossal magnetoresistance for voltages around the de-pinning threshold. This is in striking contrast to the case where even a vanishingly small {\it longitudinal} magnetic field sharply reduces the de-pinning threshold voltage resulting in {\it negative} magnetoresistance. Ruling out several other possibilities we argue that this phenomenon is likely to be a consequence of the chiral anomaly in the gapped out Weyl semimetal phase in Y$_2$Ir$_2$O$_7$.