Topological Corner States in Bilayer and Trilayer Systems with Vertically Stacked Topological Heterostructures

TL;DR

This paper explores topological corner states in bilayer and trilayer heterostructures, revealing how interlayer coupling influences corner states and proposing multipole chiral numbers as a superior topological invariant.

Contribution

It introduces the concept of topological heterostructures and demonstrates the effectiveness of multipole chiral numbers over Wilson loops for classifying topological phases.

Findings

Interlayer coupling induces topological phase transitions affecting corner states

Multipole chiral numbers accurately classify $ ext{HOTI}$ phases

Corner states can be controlled in multilayer topological systems

Abstract

We investigate bilayer and trilayer systems composed of topologically distinct, vertically stacked layers, forming topological heterostructures based on the Benalcazar-Bernevig-Hughes model. We find that a topological phase transition induced by interlayer coupling significantly alters the number of corner states in these topological structures. Furthermore, we find that traditional nested Wilson loop analysis inaccurately classifies certain phases, leading us to evaluate multipole chiral numbers (MCNs) as a more appropriate topological invariant for this scenario. The MCNs not only enable accurate classification of topological phases but also directly correspond to the number of zero-energy corner states, effectively characterizing $\mathbb{Z}$-class HOTI phases. Our study proposes the novel concept of topological heterostructures, providing critical insights into the control of localized corner states within multilayer systems and expanding potential research directions.