2-dimensional hyperbolic medium for electrons and photons based on the array of tunnel-coupled graphene nanoribbons

TL;DR

This paper investigates a tunnel-coupled graphene nanoribbon array that exhibits hyperbolic electronic and optical properties, enabling tunable hyperbolic metasurfaces with potential applications in photonics and electronics.

Contribution

It introduces a novel 2D hyperbolic medium based on coupled graphene nanoribbons, demonstrating hyperbolic Fermi surfaces and anisotropic optical responses.

Findings

Fermi surface becomes hyperbolic due to edge state coupling

Optical conductivity tensor is uniaxial with principal components of opposite signs

Array functions as a tunable hyperbolic metasurface

Abstract

We study the electronic band structure and optical conductivity of an array of tunnel-coupled array of graphene nanoribbons. We show that due to the coupling of electronic edge states for the zigzag nanoribbon structure, the Fermi surface can become a hyperbola similarly to the case of the layered metal-dielectric structures, where the hyperbolic isofrequency contours originate from the coupling of localized surface plasmon polaritons. Moreover, we show that for both types of the ribbon edge, the optical response of the structure can be characterized by a uniaxial conductivity tensor, having principal components of the different signs. Therefore, the tunnel-coupled nanoribbon array can be regarded as a tunable hyperbolic metasurface.