Tunnel spectroscopy of a proximity Josephson junction

Abstract

We present tunnel spectroscopy experiments on the proximity effect in lateral superconductor–normal-metal–superconductor Josephson junctions. Our weak link is embedded into a superconducting ring allowing phase biasing of the Josephson junction by an external magnetic field. We explore the temperature and phase dependence of both the induced minigap and the modification of the density of states in the normal metal. Our results agree with a model based on the quasiclassical theory in the diffusive limit. The device presents an advanced version of the superconducting quantum interference proximity transistor, now reaching flux sensitivities of 3 nA/Φ0, where Φ0 is the flux quantum.