Observation of Weyl fermions in a magnetic non-centrosymmetric crystal

TL;DR

This paper reports the discovery of magnetic Weyl fermions and topological surface states in the non-centrosymmetric magnet PrAlGe, revealing novel topological phases with robust surface states and anomalous Hall effects.

Contribution

It provides the first experimental evidence of magnetic Weyl quasiparticles and topological surface states in a non-centrosymmetric magnetic material.

Findings

Observation of topological surface arcs via photoemission spectroscopy

Detection of projected topological charges of ±1

Large anomalous Hall response linked to Weyl band structure

Abstract

Characterized by the absence of inversion symmetry, non-centrosymmetric materials are of great interest because they exhibit ferroelectricity, second harmonic generation, emergent Weyl fermions, and other fascinating phenomena. It is expected that if time-reversal symmetry is also broken, additional magneto-electric effects can emerge from the interplay between magnetism and electronic order. Here we report topological conducting properties in the non-centrosymmetric magnet PrAlGe. By photoemission spectroscopy, we observe an arc parametrizing surface-localized states---a topological arc. Using the bulk-boundary correspondence, we conclude that these arcs correspond to projected topological charges of $\pm{1}$ in the surface Brillouin zone, demonstrating the presence of magnetic Weyl quasiparticles in bulk. We further observe a large anomalous Hall response, arising from diverging bulk Berry curvature fields associated with the magnetic Weyl band structure. Our results demonstrate a topological phase with robust electronic surface states and anomalous transport in a non-centrosymmetric magnet for the first time, providing a novel material platform to study the interplay between magnetic order, band topology and transport.