Functional Metamaterials Based on Mesoscale Gold Sponges, Particulate Aggregates, and Their Composites with Dielectric Materials

摘要

The optical properties of some nanoscale composites may deviate from that expected from a simple law of mixture of their individual components. In these cases the resulting structure can be considered to be a type of 'metamaterial'. Here we explore some of the possibilities for nanoscale composite structures comprised of gold and VO{sub}2 - the latter being a functional material that undergoes a reversible insulator to metallic phase transition at 68°C. Two microstructures are examined: aggregates of gold nanoparticles surrounded by VO{sub}2 as the continuous phase, and its geometric inverse, mesoporous gold sponge with discontinuous VO{sub}2 inclusions. A composite, right-angled parallelepiped measuring 40×100×100nm is taken as representative of the mixture, and calculations of the optical properties performed using the discrete dipole approximation code of Draine and Flatau. The VO{sub}2 matrix strongly attenuates the dipole-dipole plasmon resonance of the gold structure, and thermochromic switching of the remaining plasmon resonance occurs.