Magnetic response of nanoscale left-handed metamaterials

TL;DR

This paper uses simulations and an RLC circuit model to analyze the magnetic response of nanoscale left-handed metamaterials, revealing how size reduction affects resonance and permeability, and providing design optimization rules.

Contribution

It introduces an RLC circuit model to explain nanoscale effects in magnetic metamaterials and offers optimization guidelines for improved negative permeability performance.

Findings

Resonance frequency saturates at sub-micron scales.

Permeability resonance weakens with size reduction.

Fishnet design achieves higher resonance frequencies.

Abstract

Using detailed simulations we investigate the magnetic response of metamaterials consisting of pairs of parallel slabs or combinations of slabs with wires (including the fishnet design) as the length-scale of the structures is reduced from mm to nm. We observe the expected saturation of the magnetic resonance frequency when the structure length-scale goes to the sub-micron regime, as well as weakening of the effective permeability resonance and reduction of the spectral width of the negative permeability region. All these results are explained by using an equivalent resistor-inductor-capacitor (RLC) circuit model, taking into account the current-connected kinetic energy of the electrons inside the metallic parts through an equivalent inductance, added to the magnetic field inductance in the unit-cell. Using this model we derive simple optimization rules for achieving optical negative permeability metamaterials of improved performance. Finally, we analyze the magnetic response of the fishnet design and we explain its superior performance regarding the high attainable magnetic resonance frequency, as well as its inferior performance regarding the width of the negative permeability region.