VO$_2$ as a natural optical metamaterial

TL;DR

This paper explores the optical properties of VO$_2$ as a natural, self-contained metamaterial, demonstrating its potential to serve as hyperbolic metamaterials and support volume plasmon polaritons in the THz-visible spectrum.

Contribution

It provides first principles analysis of VO$_2$'s optical properties, showing how phase coexistence can be used to design natural hyperbolic metamaterials without external dielectrics.

Findings

VO$_2$ exhibits a large change in reflectance and metallicity.

Ordered VO$_2$ junctions can function as hyperbolic metamaterials.

Propagation of volume plasmon polaritons in VO$_2$ metamaterials is possible.

Abstract

VO$_2$ is a unique phase change material with strongly anisotropic electronic properties. Recently, samples have been prepared that present a co-existence of phases and thus form metal-insulator junctions of the same chemical compound. Using first principles calculations, the optical properties of metallic and semiconducting VO$_2$ are here discussed to design self-contained natural optical metamaterials, avoiding coupling with other dielectric media. The analysis of the optical properties complements the experiments in the description of the vast change in reflectance and metallicity for both disordered and planar compounds. The present results also predict the possibility to realize ordered VO$_2$ junctions operating as efficient hyperbolic metamaterials in the THz-visible range, by simply adjusting the ratio between metallic and insulating VO$_2$ content. The possibility to excite propagating {\em volume plasmom polariton} across the metamaterial is finally discussed.