Nearly triple nodal point topological phase in half-metallic GdN

TL;DR

This paper demonstrates that ferromagnetic GdN exhibits a tunable topological phase transition involving nearly triple nodal points, with potential for novel surface states and applications in topological electronics.

Contribution

It introduces a ferromagnetic material, GdN, as a platform for nearly triple nodal points where spin-orbit coupling induces tunable topological phases.

Findings

Splitting of triple nodal points ranges from 15 to 150 meV.

Magnetization orientation controls the topological phase transition.

Surface spectra and transport resemble true triple-node systems.

Abstract

Recent developments in topological semimetals open a way to realize relativistic dispersions in condensed matter systems. One recently studied type of topological feature is the "triple nodal point" where three bands become degenerate. In contrast to Weyl and Dirac nodes, triple nodal points, which are protected by a rotational symmetry, have nodal lines attached, so that a characterization in terms of a chirality is not possible. Previous studies of triple nodal points considered nonmagnetic systems, although an artificial Zeeman splitting was used to probe the topological nature. Here instead we treat a ferromagnetic material, half-metallic GdN, where the splitting of the triple nodal points comes from the spin-orbit coupling. The size of the splitting ranges from 15 to 150 meV depending on the magnetization orientation, enabling a transition between a Weyl-point phase and a "nearly triple nodal point" phase that exhibits very similar surface spectra and transport properties compared to a true triple-node system. The rich topological surface states, manipulable via the orientation of the magnetization, make half-metallic GdN a promising platform for future investigations and applications.