Quasi-1D Planar Magnetic Topological Heterostructure

TL;DR

This paper introduces a theoretical quasi-1D magnetic heterostructure combining topological and normal insulators, revealing rich topological phases and M"obius band topology through symmetry analysis and defect spectroscopy.

Contribution

It presents a novel heterostructure platform exhibiting higher-order topology, M"obius band features, and a method to distinguish topological phases via magnetic defect spectroscopy.

Findings

Identified topological phases with invariants 0, 1, and 2.

Discovered M"obius band topology in multilayer geometry.

Proposed magnetic defect spectroscopy as a fingerprint for topological phases.

Abstract

We theoretically introduce a quasi-1D magnetic heterostructure of alternating 2D topological and normal insulator strips. Its low-energy physics is governed by a hybrid Hamiltonian intertwining the Su-Schrieffer-Heeger and Shockley models, with spin-momentum locking and local Zeeman splitting. Symmetry analysis places it in class AIII, characterized by chiral symmetry and a $\mathbb{Z}$ topological invariant. Computing the winding number from the block-off-diagonal structure of the Hamiltonian reveals topological phases characterized by invariants $\nu = 0$, $1$, and $2$. Furthermore, a single magnetic defect acts as a sensitive local probe, whose in-gap spectrum provides a spectroscopic fingerprint to distinguish topological phases. Extending the platform to a multilayer geometry uncovers a nonsymmorphic projective symmetry that gives rise to M\"obius band topology, with the Brillouin zone compactifying into a Klein bottle. Our work establishes a platform for higher-order topology via heterostructure design and magnetic patterning.