GdN thin-film: Chern Insulating State on Square Lattice

TL;DR

This paper predicts a Chern insulating phase in ferromagnetic GdN thin films on a square lattice, which could enable quantum anomalous Hall effects without complex doping or substrates, based on first-principles calculations.

Contribution

It introduces a new candidate material, GdN thin films, for Chern insulators on a square lattice, simplifying experimental realization.

Findings

Chern insulating phase predicted in GdN thin films.

Band gap up to 100 meV in trilayer GdN.

Band gap decreases with increasing film thickness.

Abstract

Using first-principles calculations, we predict a Chern insulating phase in thin films of the ferromagnetic semi-metal GdN. In contrast to previously proposed Chern insulator candidates, which mostly rely on honeycomb lattices, this system affords a great chance to realize the quantum anomalous Hall Effect on a square lattice without either a magnetic substrate or transition metal doping, making synthesis easier. The band inversion between 5d-orbitals of Gd and 2p-orbitals of N is verified by first-principles calculation based on density functional theory, and the band gap can be as large as 100 meV within GdN trilayer. With further increase of film thickness, the band gap tends to close and the metallic bulk property becomes obvious.