Supercurrent diode effect in thin film Nb tracks

Abstract

We demonstrate nonreciprocal critical current in 65 nm thick polycrystalline and epitaxial Nb thin films patterned into tracks. The nonreciprocal behavior gives a supercurrent diode effect, where the current passed in one direction is a supercurrent and the other direction is a normal state (resistive) current. We study the variation of the diode effect with temperature, magnetic field, and the width of the Nb tracks from 2-10 µm. For both polycrystalline and epitaxial samples, we find that tracks of width 4 µm provides the largest supercurrent diode efficiency of up to ≈ 30%, with the effect reducing or disappearing in the widest tracks of 10 µm. It is anticipated that the supercurrent diode will become a ubiquitous component of the superconducting computer.