Higher-order topological insulators in a crisscross antiferromagnetic model

TL;DR

This paper introduces a new class of higher-order topological insulators in 2D and 3D antiferromagnetic models, characterized by fractional charges, quantized quadrupole moments, and chiral hinge states, with unique magnetic and transport properties.

Contribution

It presents a $Z_2$-classified crisscross antiferromagnetic model exhibiting novel HOTI phases with fractional charges, quantized magnetic quadrupole moments, and chiral hinge states.

Findings

Fractional charge localized at corners in 2D model

Quantized magnetic quadrupole moment in 2D model

Chiral 1D hinge states in 3D stacked system

Abstract

We present a $4'/m'$-respecting crisscross AFM model in 2D and 3D, both belonging to the $Z_2$ classification and exhibiting interesting magnetic high-order topological insulating (HOTI) phases. The topologically nontrivial phase in the 2D model is characterized by the fractional charge localized around the corners and the quantized charge quadrupole moment. Moreover, our 2D model also exhibits the quantized magnetic quadrupole moment, which is a unique feature compared with previous studies. The 3D system stacked from layers of the 2D model possesses the HOTI phase holding chiral 1D metallic states on the hinge, which corresponds to the Wannier center flow between the valence and conduction bands. The novel transport properties such as the half-quantum spin-flop pumping phenomena on the side surfaces of the HOTI phase is also discussed.