Thermodynamic effects in superconducting hybrid devices

Investigating thermal transport in hybrid superconducting nanostructures can yield a better understanding of such devices and give access to new and useful phenomena. Sub-gap biased superconducting-insulator-normal metal (SIN) junctions exhibit electron cooling, which is useful for achieving electronic temperatures below the cryostat bath temperature. We have designed an experiment to allow independent monitoring of the electron and phonon populations temperatures. An electronic cooler was studied under out-of-equilibrium conditions, in both cooling and heating regimes. The results are interpreted using a thermal model, which takes into account the electron, phonon and photon heat transfer. The Kapitza and electron-phonon couplings, along with a generalized circuit theory approach for the photon heat transfer, will be discussed.