Magnetization-Tunable Topological Phase Transitions in Ferromagnetic Kagome Monolayers of Co$_3$X$_3$Y$_2$ ($X=\mathrm{Sn},\mathrm{Pb}$; $Y=\mathrm{S},\mathrm{Se}$)

TL;DR

This study shows how magnetic moment orientation can tune topological phases in ferromagnetic kagome monolayers, supported by a minimal model and DFT calculations, enabling design of tunable topological materials.

Contribution

It introduces a symmetry-adapted tight-binding model incorporating SOC to predict topological phase transitions driven by magnetic orientation in kagome ferromagnets.

Findings

Magnetic moment orientation controls topological phase transitions.

Restoration of mirror symmetry induces topological changes.

DFT calculations support the model's predictions.

Abstract

The quantum anomalous Hall effect in magnetic kagome materials has emerged as a versatile platform for dissipationless electronic and spintronic devices. In this work, we demonstrate that the orientation of magnetic moments $\hat{m}(\theta,\phi)$ at lattice sites provides a practical tuning mechanism for engineering nontrivial topological phases in monolayer kagome ferromagnets. To elucidate the mechanism, we construct a symmetry-adapted minimal tight-binding model for kagome ferromagnets that includes intrinsic spin-orbit coupling (SOC) and the intrinsic Rashba SOC permitted by broken out-of-plane mirror symmetry between nearest-neighbor kagome sites and can capture the resulting topological phase diagram as a function of $\hat{m}(\theta,\phi)$. In particular, the restoration of in-plane mirror symmetry for specific values of $\phi$ drives a topological phase transition upon varying the in-plane orientation of the moments $\hat{m}(\theta = 90^{\circ}, \phi)$. In contrast, for fixed $\phi$, the transitions driven by varying $\theta$ originate from the competition between Rashba SOC and intrinsic SOC. Density functional theory calculations for ferromagnetic kagome monolayers belonging to the Co$_3$X$_3$Y$_2$ family ($X=\mathrm{Sn},\mathrm{Pb}$; $Y=\mathrm{S},\mathrm{Se}$) support the predictions of the proposed minimal tight-binding model. These findings provide design guidelines for tunable topological phases in kagome materials.