We demonstrate an increased quasiparticle recombination time in superconducting resonators on a SiNx membrane, compared to identical resonators on a SiNx/Si wafer. An interpretation is given using a thermal model of the membrane. Using an array of tunnel junctions to cool or heat the membrane, we show that the resonators on the membranes are extremely sensitive to small changes of the phonon temperature, which renders them excellent phonon thermometers with a noise level equivalent to 5μK/Hz⎯⎯⎯⎯⎯√. The experimental set-up is in principle an ideal platform to study the interplay of quasiparticles and phonon populations in superconductors.
- aluminium compounds
- membranes, phonons
- superconducting resonators
- superconductor-insulator-superconductor devices
- superconductor-normal-superconductor devices