Josephson radiation and shot noise of a semiconductor nanowire junction

Abstract

We measured the Josephson radiation emitted by an InSb semiconductor nanowire junction utilizing photon assisted quasiparticle tunneling in an AC-coupled superconducting tunnel junction. We quantify the action of the local microwave environment by evaluating the frequency dependence of the inelastic Cooper-pair tunneling of the nanowire junction and find the zero frequency impedance $Z(0)=492\Omega$ with a cutoff frequency of $f_0=33.1$GHz. We extract a circuit coupling efficiency of $\eta \approx 0.1$ and a detector quantum efficiency approaching unity in the high frequency limit. In addition to the Josephson radiation, we identify a shot-noise contribution with a Fano factor $F\approx 1$, consistently with the presence of single electron states in the nanowire channel.

Raw data and supplementary calculations are available at http://dx.doi.org/10.4121/uuid:2cfc62ff-e15e-4e90-90e1-e6254baecb12