Experimental Study of Nonequilibrium Coherent Electron Transport with Solid-State NIS Interferometers

Experiments on normal metal-insulator-superconductor (NIS) tunnel junctions provide critical insights into electron transport and relaxation mechanisms and may be used to study the phase coherence in metallic and superconducting materials. In this work, we present experimental study of nonequilibrium quasiparticle transport at ultra-low temperatures in NIS tunnel nanostructures representing a solid-state analogue of a double slit optical interferometer. The results demonstrate a non-monotonic, oscillatory behavior of the tunnel current as a function of applied magnetic flux just above superconducting gap ( $$e{{V}_{{{\text{inj}}}}} \geqslant \Delta $$ ), providing qualitative evidence of coherent quasiparticle transport over mesoscopic scales.