Single Superconducting Split-Ring Resonator Electrodynamics

TL;DR

This study explores the microwave electrodynamics of superconducting split-ring resonators, demonstrating high-Q resonances, negative-index passbands, and the influence of superconducting properties on their behavior.

Contribution

It provides the first detailed analysis of superconducting split-ring resonator electrodynamics, including experimental data and modeling of their permeability and dielectric response.

Findings

High-Q stopband observed in Nb SRRs at 4.2 K

Negative-index passband achieved with SRR arrays

Superconducting kinetic inductance affects resonator features

Abstract

We investigate the microwave electrodynamic properties of a single superconducting thin film split-ring resonator (SRR). The experiments were performed in an all-Nb waveguide, with Nb wires and Nb SRRs. Transmission data showed a high-Q stopband for a single Nb SRR ($Q \sim 4.5\times10^4$ at 4.2 K) below $T_c$, and no such feature for a Cu SRR, or closed Nb loops, of similar dimensions. Adding SRRs increased the bandwidth, but decreased the insertion loss of the features. Placing the Nb SRR into an array of wires produced a single, elementary negative-index passband ($Q \sim 2.26\times10^4$ at 4.2 K). Changes in the features due to the superconducting kinetic inductance were observed. Models for the SRR permeability, and the wire dielectric response, were used to fit the data.