Controlling topology through targeted composite symmetry manipulation in magnetic systems

TL;DR

This study demonstrates how tuning magnetization direction in a 2D magnetic material can switch its topological phase between semimetal and insulator, revealing a pathway for spintronic device applications.

Contribution

It introduces a method to control topological phases in 2D magnetic systems via targeted symmetry manipulation, supported by theoretical models and material examples.

Findings

Out-of-plane magnetization yields a semimetallic phase.

In-plane magnetization opens a band gap near 100 meV.

Breaking inversion symmetry induces a Chern insulator phase.

Abstract

The possibility of selecting magnetic space groups by orienting the magnetization direction or tuning magnetic orders offers a vast playground for engineering symmetry protected topological phases in magnetic materials. In this work, we study how selective tuning of symmetry and magnetism can influence and control the resulting topology in a 2D magnetic system, and illustrate such procedure in the ferromagnetic monolayer MnPSe$_3$. Density functional theory calculations reveals a symmetry-protected accidental semimetalic (SM) phase for out-of-plane magnetization which becomes an insulator when the magnetization is tilted in-plane, reaching band gap values close to $100$ meV. We identify an order-two composite antiunitary symmetry and threefold rotational symmetry that induce the band crossing and classify the possible topological phases using symmetry analysis, which we support with tight-binding and $\mathbf{k}\cdot\mathbf{p}$ models. Breaking of inversion symmetry opens a gap in the SM phase, giving rise to a Chern insulator. We demonstrate this explicitly in the isostructural Janus compound Mn$_2$P$_2$S$_3$Se$_3$, which naturally exhibits Rashba spin-orbit coupling that breaks inversion symmetry. Our results map out the phase space of topological properties of ferromagnetic transition metal phosphorus trichalcogenides and demonstrate the potential of the magnetization-dependent metal-to-insulator transition as a spin switch in integrated two-dimensional electronics.