Microwave photonic crystals as an experimental realization of a combined honeycomb-kagome lattice

Abstract

In 2015 experiments were performed with superconducting microwave photonic crystals emulating artificial graphene B. Dietz, T. Klaus, M. Miski-Oglu, and A. Richter, Phys. Rev. B 91, 035411 (2015)]. The associated density of states comprises two Dirac points with adjacent bands including van Hove singularities, thus exhibiting the characteristic features originating from the extraordinary electronic band structure of graphene. They are separated by a narrow region of particularly high resonance density corresponding to a nearly flatband in the band structure, which is reminiscent of that of a honome lattice -- a combination of two sublattices: honeycomb and kagome. We demonstrate that, indeed, the density of states, and also the eigenmode properties and the fluctuations in the resonance-frequency spectra are well reproduced by a tight-binding model based on the honome lattice. A good description was achieved by means of the reverse Monte-Carlo approach, thereby confirming our intepretation of the microwave photonic crystal as an experimental realization of a honome lattice and providing an answer to longstanding problem, namely the understanding of the origin of the flatband bordered by two Dirac points, generally observed in microwave photonic crystals of different shapes.