Orateur
Description
Disordered superconductors offer new impedance regimes for quantum circuits, enable a pathway to protected qubits, and can improve superconducting detectors due to their high kinetic inductance and sheet resistance. Our focus is on kinetic inductance detectors for visible- to near-infrared wavelengths, for exoplanet research.
The performance of these devices is determined by quasiparticles dynamics – recombination, electron-phonon scattering and the electrodynamics. While experiments have shown that disorder affects the relaxation of quasiparticles drastically, the microscopic mechanisms are still not understood. We measure quasiparticle relaxation in a disordered β-Ta film, which we pattern as the inductor of a microwave resonator. We observe that quasiparticle recombination is governed by the phonon scattering time, and that it is not affected by phonon trapping (using a membrane), both in contrast with the same experiments with an ordered superconductor (aluminium). We interpret the results as recombination of localized quasiparticles, induced by disorder, which first delocalize.
We will discuss how this type of measurement, which addresses both the temporal dynamics of the quasiparticle system and its microwave electrodynamics, could experimentally bridge the gap between the observed excess microwave dissipation in disordered supercondcutors and the microscopic interpretation in terms of excess quasiparticles, trapping and recombination.