Normal Metal–Insulator–Superconductor Aharonov-Bohm Interferometer

When a non-equilibrium excitation (a non-paired electron) is injected into a superconductor, it can travel fairly large distance before forming an equilibrium Copper pair. Here, we fabricated and experimentally studied electron transport in a solid-state analogue of a two-slit optical interferometer: T-shaped normal metal electrode (copper) — dielectric tunnel layer (aluminum oxide) — superconducting fork (aluminum). If the perimeter of the interferometer loop is sufficiently small, the phase of the non-equilibrium quasiparticle wave function is preserved and can be adjusted utilizing the Aharonov-Bohm effect. The coherent contribution manifests itself as non-monotonic dependence of the tunnel current on perpendicular magnetic field.