Metallic coplanar resonators optimized for low-temperature measurements

TL;DR

This study characterizes low-temperature copper coplanar microwave resonators, demonstrating their high quality factors and stability under magnetic fields, making them suitable for magnetic resonance applications.

Contribution

It provides a detailed analysis of copper coplanar resonators' performance at low temperatures, including effects of geometry and magnetic fields, which was previously underexplored.

Findings

Quality factor up to 470 at 5 K for wider conductors

Weak magnetic field dependence with only 3.5% change at 7 T

Resonators are suitable for electron spin resonance measurements

Abstract

Metallic coplanar microwave resonators are widely employed at room temperature, but their low-temperature performance has received little attention so far. We characterize compact copper coplanar resonators with multiple modes from 2.5 to 20 GHz at temperatures as low as 5 K. We investigate the influence of center conductor width (20 to 100 {\mu}m) and coupling gap size (10 to 50 {\mu}m), and we observe a strong increase of quality factor (Q) for wider center conductors, reaching values up to 470. The magnetic-field dependence of the resonators is weak, with a maximum change in Q of 3.5% for an applied field of 7 T. This makes these metallic resonators well suitable for magnetic resonance studies, as we document with electron spin resonance (ESR) measurements at multiple resonance frequencies.