Evidence for Weyl fermions in a canonical heavy-fermion semimetal YbPtBi

TL;DR

This paper provides evidence that the heavy-fermion semimetal YbPtBi hosts Weyl fermions, with experimental and theoretical data showing how electronic correlations influence their properties and topological features.

Contribution

It demonstrates the existence of Weyl fermions in YbPtBi and explores how strong correlations affect their manifestation and detection.

Findings

Weyl nodes appear at high temperatures with localized 4f-electrons.

Chiral anomaly contributes to magnetotransport signals.

Topological Hall effect indicates Berry curvature associated with Weyl fermions.

Abstract

The manifestation of Weyl fermions in strongly correlated electron systems is of particular interest. We report evidence for Weyl fermions in the heavy fermion semimetal YbPtBi from electronic structure calculations, angle-resolved photoemission spectroscopy, magnetotransport and calorimetric measurements. At elevated temperatures where $4f$-electrons are localized, there are triply degenerate points, yielding Weyl nodes in applied magnetic fields. These are revealed by a contribution from the chiral anomaly in the magnetotransport, which at low temperatures becomes negligible due to the influence of electronic correlations. Instead, Weyl fermions are inferred from the topological Hall effect, which provides evidence for a Berry curvature, and a cubic temperature dependence of the specific heat, as expected from the linear dispersion near the Weyl nodes. The results suggest that YbPtBi is a Weyl heavy fermion semimetal, where the Kondo interaction renormalizes the bands hosting Weyl points. These findings open up an opportunity to explore the interplay between topology and strong electronic correlations.