InAs nanowire superconducting tunnel junctions: Quasiparticle spectroscopy, thermometry, and nanorefrigeration
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We demonstrate an original method based on controlled oxidation for creating high-quality tunnel junctions between superconducting Al reservoirs and InAs semiconductor nanowires (NWs). We show clean tunnel characteristics with a current suppression by >4 orders of magnitude for a junction bias well below the Al gap of Δ0 ≈ 200 μeV. The experimental data agree well with the Bardeen–Cooper–Schrieffer theoretical expectations for a superconducting tunnel junction. The studied devices employ small-scale tunnel contacts functioning as thermometers as well as larger electrodes that provide proof-of-principle active cooling of the electron distribution in the NWs. A peak refrigeration of approximately δT = 10 mK is achieved at a bath temperature of Tbath ≈ 250–350 mK for our prototype devices. This method introduces important perspectives for the investigation of the thermoelectric effects in semiconductor nanostructures and for nanoscale refrigeration.
KeywordsInAs nanowire superconducting tunnel junction thermometry nanorefrigeration
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