Field-linear anomalous Hall effect and Berry curvature induced by spin chirality in the kagome antiferromagnet Mn3Sn

TL;DR

This paper reports a novel field-linear anomalous Hall effect in Mn3Sn, driven by Berry curvature modifications due to spin chirality, revealing a new link between real-space spin textures and momentum-space topology.

Contribution

It uncovers a unique field-linear AHE in Mn3Sn caused by spin chirality-induced Berry curvature changes, bridging real-space spin textures and band topology.

Findings

In-plane Hall response is linear in magnetic field and larger than semiclassical predictions.

Magnetic field induces out-of-plane spin canting and spin chirality, affecting electronic topology.

Spin chirality gaps Weyl nodal lines, explaining the observed AHE.

Abstract

During the past two decades, it has been established that a non-trivial electron wave-function topology generates an anomalous Hall effect (AHE), which shows itself as a Hall conductivity non-linear in magnetic field. Here, we report on an unprecedented case of field-linear AHE. In Mn$_3$Sn, a kagome magnet, the out-of-plane Hall response, which shows an abrupt jump, was discovered to be a case of AHE. We find now that the in-plane Hall response, which is perfectly linear in magnetic field, is set by the Berry curvature of the wavefunction. The amplitude of the Hall response and its concomitant Nernst signal exceed by far what is expected in the semiclassical picture. We argue that magnetic field induces out-of-plane spin canting and thereafter gives rise to nontrivial spin chirality on the kagome lattice. In band structure, we find that the spin chirality modifies the topology by gapping out Weyl nodal lines unknown before, accounting for the AHE observed. Our work reveals intriguing unification of real-space Berry phase from spin chirality and momentum-space Berry curvature.