Symmetry tuning topological states of an axion insulator with noncollinear magnetic order

TL;DR

This paper investigates how applying an in-plane magnetic field to EuIn$_2$As$_2$ can tune its magnetic symmetry and topological surface and hinge states, revealing potential for controllable topological phase transitions and chiral transport pathways.

Contribution

It demonstrates the control of magnetic and topological states in EuIn$_2$As$_2$ through magnetic field tuning, combining experimental and theoretical analysis.

Findings

Magnetic field induces a transition from broken-helix to field-polarized phase.

Field-tunable hinge-state patterns and topological phase transitions are predicted.

Domain walls can host pinned hinge states, affecting chiral charge transport.

Abstract

Topological properties of quantum materials are intimately related to symmetry. Here, we tune the magnetic order of the axion insulator candidate EuIn$_2$As$_2$ from its broken-helix ground state to the field-polarized phase by applying an in-plane magnetic field. Using results from neutron diffraction and magnetization measurements with ab inito theory and symmetry analysis, we determine how the field tunes the magnetic symmetry within individual magnetic domains and examine the resulting changes to the topological surface states and hinge states existing on edges shared by certain surfaces hosting gapped Dirac states. We predict field-tunable complex and domain-specific hinge-state patterns, with some crystal surfaces undergoing a field-induced topological phase transition. We further find that domain walls have pinned hinge states when intersecting certain crystal surfaces, providing another channel for tuning the chiral-charge-transport pathways.