High-Q terahertz metamaterial from superconducting niobium nitride films

TL;DR

This paper demonstrates low-loss, high-Q terahertz metamaterials using superconducting niobium nitride films, achieving significantly higher quality factors than gold-based structures, with potential for advanced THz devices.

Contribution

It introduces superconducting NbN-based metamaterials with high quality factors at THz frequencies, advancing low-loss, high-performance THz device design.

Findings

Quality factor up to 178 at 8 K

High Q factor maintained at higher frequencies

Experimental results explained by BCS theory and circuit models

Abstract

We present in this letter terahertz (THz) metamaterials with low ohmic losses made from low-temperature superconductor niobium nitride (NbN) films. The resonance properties are characterized by THz time-domain spectroscopy. The unloaded quality factor reaches as high as about 178 at 8 K with the resonance frequency at around 0.58 THz, which is about 24 times as many as gold metamaterials with the same structure. The unloaded quality factor also keeps high as the resonance frequency increases, which is about 90 at 1.02 THz that is close the gap frequency of NbN film. All these experimental observations are well understood in the framework of Bardeen-Cooper-Schrieffer theory and equivalent circuit model. Our work offers an efficient way to design and make high-performance THz electronic devices.