Noncollinear Magnetic Modulation of Weyl Nodes in Ferrimagnetic Mn$_3$Ga

TL;DR

This study reveals how noncollinear magnetic structures in Mn$_3$Ga can modulate Weyl nodes, showing the emergence, evolution, and tunability of topological features driven by magnetic orientation and symmetry considerations.

Contribution

It demonstrates the emergence and magnetic-tuning of Weyl nodes in Mn$_3$Ga, highlighting the role of noncollinear ferrimagnetic order and symmetry protection in topological electronic structures.

Findings

Weyl nodes protected by mirror and rotational symmetries without SOC.

SOC induces Weyl nodes with chiral charge ±2.

Magnetic tilt angle splits double Weyl nodes into charge-1 Weyl nodes.

Abstract

The tetragonal ferrimagnetic Mn$_3$Ga exhibits a wide range of intriguing magnetic properties. Here, we report the emergence of topologically nontrivial nodal lines in the absence of spin orbit coupling (SOC) which are protected by both mirror and $C_{4z}$ rotational symmetries. In the presence of SOC we demonstrate that the doubly degenerate nontrivial crossing points evolve into $C_{4z}$-protected Weyl nodes with chiral charge of $\pm$2. Furthermore, we have considered the experimentally reported noncollinear ferrimagnetic structure, where the magnetic moment of the Mn$_I$ atom (on the Mn-Ga plane) is tilted by an angle $\theta$ with respect to the crystallographic $c$ axis. The evolution of the Weyl nodes with $\theta$ reveals that the double Weyl nodes split into a pair of charge-1 Weyl nodes whose separation can be tuned by the magnetic orientation in the noncollinear ferrimagnetic structure.