• DOI:10.1063/1.4939299
• Corpus ID: 118583472

Loss mechanisms in superconducting thin film microwave resonators

@article{Goetz2015LossMI,
  title={Loss mechanisms in superconducting thin film microwave resonators},
  author={Jan Goetz and Frank Deppe and Max Haeberlein and Friedrich Wulschner and Christoph W. Zollitsch and Sebastian B. Meier and Michael Fischer and P Eder and Edwar Xie and Kirill G Fedorov and Edwin P. Menzel and Achim Marx and Rudolf Gross},
  journal={arXiv: Superconductivity},
  year={2015}
}

• J. Goetz, F. Deppe, +10 authors R. Gross
• Published 20 October 2015
• Physics
• arXiv: Superconductivity

We present a systematic analysis of the internal losses of superconducting coplanar waveguide microwave resonators based on niobium thin films on silicon substrates. In particular, we investigate losses introduced by Nb/Al interfaces in the center conductor, which is important for experiments where Al based Josephson junctions are integrated into Nb based circuits. We find that these interfaces can be a strong source for two-level state (TLS) losses, when the interfaces are not positioned at current nodes of the resonator. In addition to TLS losses, for resonators including Al, quasiparticle losses become relevant above 200 mK. Finally, we investigate how losses generated by eddy currents in conductive material on the backside of the substrate can be minimized by using thick enough substrates or metals with high conductivity on the substrate backside.