Magnetoresistance in quasi-one dimensional Weyl semimetal (TaSe$_4$)$_2$I

TL;DR

This study investigates the magnetoresistance behavior in a quasi-one-dimensional Weyl semimetal with a charge density wave, revealing small positive magnetoresistance in all regimes and a notable negative magnetoresistance in nonlinear conduction, questioning conditions for axion anomaly observation.

Contribution

It provides new experimental insights into magnetotransport in Weyl semimetals with CDW, especially under phase slip conditions, contrasting previous findings and raising questions about axion anomaly detection.

Findings

Longitudinal magnetoresistance is small and positive across all CDW regimes.

Negative magnetoresistance appears in nonlinear conduction with phase slip.

Results challenge previous observations and implications for axion anomaly detection.

Abstract

Magnetic field effect on linear and nonlinear conductivity in a quasi-one-dimensional Weyl semimetal with a charge density wave (CDW) (TaSe$_4$)$_2$I is studied. Longitudinal magnetoresistance in all known regimes of CDW motion (linear conduction, creep, sliding, "Fr\"ohlich superconductivity") is small, positive and do not exceed a fraction of per cent. Similar magnetotransport measurements were performed in samples profiled by focused ion beams is such a way that motion of the CDW in them is accompanied by phase slip of the CDW. In such samples, a peak-like non-parabolic negative magnetoresistance is observed in relatively small magnetic fields $B \lesssim 4$ T in the nonlinear conduction regime in both longitudinal and transverse geometries. Our results differ significantly from ones obtained earlier and raise the question concerning conditions for observing the axion anomaly in Weyl semimetals in the Peierls state.