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.
@article{arxiv.1608.06122,
title = {Metallic coplanar resonators optimized for low-temperature measurements},
author = {Mojtaba Javaheri Rahim and Thomas Lehleiter and Daniel Bothner and Cornelius Krellner and Dieter Koelle and Reinhold Kleiner and Martin Dressel and Marc Scheffler},
journal= {arXiv preprint arXiv:1608.06122},
year = {2016}
}