Observation of flat band for terahertz spoof plasmon in metallic kagom\'e lattice

TL;DR

This paper demonstrates the existence of a flat plasmonic band in a metallic kagome lattice metamaterial at terahertz frequencies, confirmed through fabrication and transmission measurements.

Contribution

It provides experimental evidence of a flat band in a metallic kagome lattice, linking topological lattice properties to terahertz plasmonic behavior.

Findings

Observation of a flat band in terahertz regime

Transmission minima depend on incident beam polarization

Resonant frequency nearly independent of incident angle

Abstract

We study the dispersion relation of a metamaterial composed of metallic disks and bars arranged to have kagome symmetry and find that a plasmonic flat band is formed by the topological nature of the kagome lattice. To confirm the flat-band formation, we fabricate the metamaterial and make transmission measurements in the terahertz regime. Two bands formed by transmission minima that depend on the polarization of the incident terahertz beams are observed. One of the bands corresponds to the flat band, as confirmed by the fact that the resonant frequency is almost independent of the incident angle.