Metallic coplanar resonators optimized for low-temperature measurements
  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. 
Mojtaba Javaheri Rahim, Thomas Lehleiter, Daniel Bothner, Cornelius   Krellner, Dieter Koelle, Reinhold Kleiner, Martin Dres...
cond-mat.mes-hall