The suppression of Finite Size Effect within a Few Lattices

TL;DR

This paper uncovers a special finite size effect in lattice boundary modes that can vanish at specific wave vectors, enabling precise control over mode coupling and potential applications in photonics.

Contribution

It identifies and analytically proves a unique finite size effect that disappears at certain wave vectors, allowing for tunable boundary mode interactions.

Findings

FSE can vanish at specific wave vectors

Number of vanishing wave vectors equals the number of lattice strips

Physical realization demonstrated with plasmonic sphere array

Abstract

Boundary modes localized on the boundaries of a finite-size lattice experience a finite size effect (FSE) that could result in unwanted couplings, crosstalks and formation of gaps even in topological boundary modes. It is commonly believed that the FSE decays exponentially with the size of the system and thus requires many lattices before eventually becoming negligibly small. Here we identify a special type of FSE of some boundary modes that apparently vanishes at some particular wave vectors along the boundary. Meanwhile, the number of wave vectors where the FSE vanishes equals the number of lattices across the strip. We analytically prove this type of FSE in a simple model and prove this peculiar feature. We also provide a physical system consisting of a plasmonic sphere array where this FSE is present. Our work points to the possibility of almost arbitrarily tunning of the FSE, which facilitates unprecedented manipulation of the coupling strength between modes or channels such as the integration of multiple waveguides and photonic non-abelian braiding.