Spin-Dependent High-Order Topological Insulator and Two Types of Distinct Corner Modes in Monolayer FeSe/GdClO Heterostructure

TL;DR

This paper predicts a spin-dependent second-order topological insulator in monolayer FeSe/GdClO, revealing two distinct types of corner modes with unique properties, advancing understanding of high-order topological phases.

Contribution

It introduces a novel spin-dependent second-order topological insulator in a specific heterostructure and characterizes two distinct corner modes with different physical origins.

Findings

Identification of a spin-dependent second-order topological insulator in FeSe/GdClO.

Discovery of two types of corner modes with different physical mechanisms.

Robustness of ferromagnetic corner mode against spin-orbit coupling.

Abstract

We propose that a spin-dependent second-order topological insulator can be realized in monolayer FeSe/GdClO heterostructure, in which substrate GdClO helps to stabilize and enhance the antiferromagnetic order in FeSe. The second-order topological insulator is free from spin-orbit coupling and in-plane magnetic field. We also find that there exist two types of distinct corner modes residing in intersections of two ferromagnetic edges and two antiferromagnetic edges, respectively. The underlying physics for ferromagnetic corner mode follows a sublattice-chirality-kink picture. More interestingly, ferromagnetic corner mode shows spin-dependent property, which is also robust against spin-orbit coupling. Unexpectedly, antiferromagnetic corner mode can be taken as a typical emergent and hierarchical phenomenon from an array of ferromagnetic corner modes. Remarkably, antiferromagnetic corner modes violate general kink picture and can be understood as bound states of a one-dimensional Schrodinger equation under a connected potential well. Our findings not only provide a promising second-order topological insulator in electronic materials, but uncover some new properties of corner modes in high-order topological insulator.