Vector Chirality $\kappa$ Driven Topological Phase Transition and the Associated Anomalous Hall Conductivity Tuning in a Non-Collinear Antiferromagnet

TL;DR

This paper demonstrates how switching vector chirality in a noncollinear antiferromagnet induces a topological phase transition, significantly altering the anomalous Hall conductivity and enabling tunable electronic properties through magnetic order manipulation.

Contribution

It introduces a novel mechanism for topological phase transition driven by vector chirality switching in a noncollinear AFM, with implications for electronic property control.

Findings

Chirality switching causes transition from nodal-ring to Weyl semimetal.

Topological transition results in a giant anomalous Hall conductivity.

Manipulating AFM order allows tuning of in-plane AHC components.

Abstract

Based on the first-principles electronic structure calculations and subsequent symmetry adapted effective low-energy $\textbf{k.p}$ theory, we show the switching of the vector chirality, $\kappa$, in a noncollinear antiferromagnet (AFM), Mn$_3$Sn, as an unconventional route to topological phase transition from a nodal-ring to a Weyl point semimetal. Specifically, we find that the switching of $\kappa$ leads to gaping out an elliptic nodal-ring everywhere at the Fermi-level except for a pair of points on the ring. As a consequence, the topological phase transition switches the anomalous Hall conductivity (AHC) from zero to a giant value. Furthermore, we theoretically demonstrate how the controlled manipulation of the chiral AFM order keeping $\kappa$ unaltered favors unusual rotation of Weyl-points on the ring. This in turn enables us to tune in-plane components of the AHC by a collective uniform rotations of spins in the AFM unit cell.