The chiral anomaly and thermopower of Weyl fermions in the half-Heusler GdPtBi

TL;DR

This paper provides evidence of the chiral anomaly in GdPtBi, a half-Heusler material, demonstrating Weyl physics in a broader class of semimetals through negative magnetoresistance and thermopower suppression.

Contribution

It shows that Weyl nodes and the chiral anomaly can emerge from quadratic bands in half-Heusler GdPtBi, expanding the class of materials exhibiting Weyl physics.

Findings

Large negative longitudinal magnetoresistance observed

Suppression of thermopower linked to chiral anomaly

Weyl nodes induced by magnetic field in GdPtBi

Abstract

The Dirac and Weyl semimetals are unusual materials in which the nodes of the bulk states are protected against gap formation by crystalline symmetry. The chiral anomaly~\cite{Adler,Bell}, predicted to occur in both systems, was recently observed as a negative longitudinal magnetoresistance (LMR) in Na$_3$Bi and in TaAs. An important issue is whether Weyl physics appears in a broader class of materials. We report evidence for the chiral anomaly in the half-Heusler GdPtBi. In zero field, GdPtBi is a zero-gap semiconductor with quadratic bands. In a magnetic field, the Zeeman energy leads to Weyl nodes. We have observed a large negative LMR with the field-steering properties specific to the chiral anomaly. The chiral anomaly also induces strong suppression of the thermopower. We report a detailed study of the thermoelectric response function $\alpha_{xx}$ of Weyl fermions. The scheme of creating Weyl nodes from quadratic bands suggests that the chiral anomaly may be observable in a broad class of semimetals.