Power and temperature dependence of High Q superconducting resonators

An integrated power and temperature dependent model of resonator quality factor predicts loss contributions from two-level systems and quasiparticles simultaneously. At millikelvin temperatures, in the presence of external power, the weak electron-phonon coupling between the phonons and quasiparticles may lead to quasiparticles thermalizing at a different temperature than phonons.
Here we propose a two temperature power and temperature dependent model to evaluate resonator losses that considers quasiparticle and phonon temperatures to be different. Resonators fabricated from epitaxial molecular beam epitaxy grown aluminum and titanium nitride on float-zone refined silicon are evaluated to have quality factors above 1M. These results are analyzed with the proposed model and the contribution of various loss mechanisms will also be explored.