Non-Hermitian Effects in the Su-Schrieffer-Heeger model: Exploring Substrate Coupling and Decoupling Dynamics

TL;DR

This paper explores how substrate interactions induce non-Hermitian effects in the SSH model, affecting topological states and revealing tunable phenomena relevant for quantum and nanodevice applications.

Contribution

It demonstrates the impact of substrate coupling on non-Hermitian physics in the SSH model and introduces scenarios for controlling zero-energy states through coupling tuning.

Findings

Substrate coupling induces amplification or attenuation of zero-energy states.

Decoupling segments of the SSH chain creates localized zero-energy modes.

Tuning coupling strength leads to novel topological phenomena.

Abstract

The substrate-adsorbate interaction can significantly influence the adsorbate's electronic structure, stability, reactivity, and topological properties. In this study, we investigate the emergence of non-Hermitian physics in the Su-Schrieffer-Heeger (SSH) model when coupled to a substrate, focusing on the impact of substrate interaction on the electronic states of the adsorbate. We demonstrate how the coupling between the SSH chain and the underlying substrate induces non-Hermitian effects, which manifest as amplification or attenuation of zero-energy electronic states. Furthermore, inspired by novel experimental techniques such as using a scanning tunneling microscope tip to lift part of the nanomaterial, we present simulations of scenarios where a segment of the SSH chain is decoupled from the substrate. By examining various configurations, including cases with odd or even numbers of sites coupled to the substrate, we demonstrate that tuning the coupling strength induces novel phenomena, such as the emergence of a zero-energy monomode or additional zero-energy states localized at the boundary between on-surface and suspended chain segments. Our results reveal the role of substrate coupling in shaping the topological properties of non-Hermitian SSH chains, offering new insights into tunable non-Hermitian effects and their potential applications in quantum technologies and nanodevices.