Experimental demonstration of non-adjacent band topology connecting multiple nodal links

TL;DR

This paper experimentally demonstrates a photonic metamaterial system showcasing non-adjacent band topology and multiple nodal links, revealing hidden relations between non-adjacent band pairs through topological characterization.

Contribution

It introduces the concept of non-adjacent band topology in nodal links and experimentally verifies it using a designed metamaterial system.

Findings

Successful design and fabrication of a metamaterial with multiple nodal links

Experimental evidence of non-adjacent band topology

Prediction of higher band nodal lines from lower band nodal chains

Abstract

Nodal links are special configurations of band degeneracies in the momentum space, where nodal line branches encircle each other. In PT symmetric systems, nodal lines can be topologically characterized using the eigenvector frame rotations along an encircling loop and the linking structure can be described with non-Abelian frame charges interacting among adjacent bands. In this paper, we present a photonic multiple nodal links system, where non-adjacent band topology is proposed to characterize the hidden relation between nodal lines from non-adjacent band pairs. Through an orthogonal nodal chain, the nodal line from the lower two bands predicts the existence of nodal lines formed between the higher bands. We designed and fabricated a metamaterial, with which the multiple nodal links and non-adjacent band topology are experimentally demonstrated.