Orbital edge states in a photonic honeycomb lattice

TL;DR

This paper experimentally demonstrates the existence of topologically protected and dispersive edge states in a photonic honeycomb lattice with orbital bands, revealing new phenomena analogous to electronic materials.

Contribution

It introduces the observation of both zero-energy and dispersive edge states in a photonic lattice with orbital bands, expanding understanding of topological photonics.

Findings

Observation of zero-energy edge states with topological origin.

Discovery of dispersive edge states in various edge terminations.

Reproduction of results through tight-binding and analytical models.

Abstract

We experimentally reveal the emergence of edge states in a photonic lattice with orbital bands. We use a two-dimensional honeycomb lattice of coupled micropillars whose bulk spectrum shows four gapless bands arising from the coupling of $p$-like photonic orbitals. We observe zero-energy edge states whose topological origin is similar to that of conventional edge states in graphene. Additionally, we report novel dispersive edge states that emerge not only in zigzag and bearded terminations, but also in armchair edges. The observations are reproduced by tight-binding and analytical calculations. Our work shows the potentiality of coupled micropillars in elucidating some of the electronic properties of emergent 2D materials with orbital bands.