Negative magnetoresistance without well-defined chirality in the Weyl semimetal TaP

TLDR

Weyl semimetals host linearly dispersing bands around Weyl points with fixed chirality, and nonorthogonal electric and magnetic fields can trigger a chiral anomaly that produces negative longitudinal magnetoresistance. The study aims to determine whether the chiral‑anomaly‑induced negative magnetoresistance persists when the Weyl points’ chirality is not well defined. Using angle‑resolved quantum‑oscillation spectra and band‑structure calculations, the authors mapped TaP’s banana‑shaped electron and hole pockets around Weyl points and demonstrated that magnetic‑field‑induced inhomogeneous current distribution can influence the magnetoresistance. Despite the ill‑defined chirality, TaP exhibits a pronounced negative longitudinal magnetoresistance.

Abstract

Abstract Weyl semimetals (WSMs) are topological quantum states wherein the electronic bands disperse linearly around pairs of nodes with fixed chirality, the Weyl points. In WSMs, nonorthogonal electric and magnetic fields induce an exotic phenomenon known as the chiral anomaly, resulting in an unconventional negative longitudinal magnetoresistance, the chiral-magnetic effect. However, it remains an open question to which extent this effect survives when chirality is not well-defined. Here, we establish the detailed Fermi-surface topology of the recently identified WSM TaP via combined angle-resolved quantum-oscillation spectra and band-structure calculations. The Fermi surface forms banana-shaped electron and hole pockets surrounding pairs of Weyl points. Although this means that chirality is ill-defined in TaP, we observe a large negative longitudinal magnetoresistance. We show that the magnetoresistance can be affected by a magnetic field-induced inhomogeneous current distribution inside the sample.