Higher-order topological corner states induced solely by onsite potentials with mirror symmetry

TL;DR

This paper demonstrates that higher-order topological corner states can be induced solely by mirror-symmetric onsite potentials, providing a simple and experimentally accessible method to realize topological insulators with corner modes.

Contribution

It introduces a new approach to realize higher-order topological phases using only onsite potentials, without the need for tuning tunneling or other complex parameters.

Findings

Corner modes emerge in a 2D model with mirror-symmetric onsite potentials.

Corner states are protected by mirror symmetry and are robust against symmetry-preserving perturbations.

The approach simplifies the realization of higher-order topological insulators in experiments.

Abstract

Higher-order topological insulators have triggered great interests because of exhibitions of non-trivial bulk topology on lower-dimensional boundaries like corners and hinges. While such interesting phases have been investigated in a plethora of systems by tuning staggered tunneling strength or manipulating existing topological phases, here we show that a higher-order topological phase can be driven solely by mirror-symmetric onsite potentials. We first introduce a simple chain model in one dimension that mimics the Su-Schrieffer-Heeger-like model. However, due to the lack of internal symmetries like chiral or particle-hole symmetry, the energies of the topological edge modes are not pinned at zero. Once the model is generalized to two dimensions, we observe the emergence of topological corner modes. These corner modes are intrinsic manifestation of non-trivial bulk band topology protected by mirror symmetry, and thus, they are robust against symmetry-preserved perturbations. Our study provides a concise proposal for realizing a class of higher-order topological insulators, which involves only tuning onsite energies. This can be easily accessible in experiments and provides a different playground for engineering topological corner modes.