Topological reciprocity in 3D superconducting diodes

Abstract The design of advanced functionality in superconducting devices usually focuses on materials engineering, either in heterostructures or in compounds of unconventional quantum materials. Here we demonstrate a different strategy to bespoke behavior by controlling the 3D shape of superconductors on the micron-scale. As a demonstration, a large superconducting diode effect is engineered solely by 3D shape design of a conventional superconductor, ion-beam deposited tungsten. Its highly efficient diode behavior appears from its triangular cross-section when vortices break time-reversal and all mirror symmetries. Yet reciprocity is observed at special field angles where the lack of symmetry would lead one to expect diode behavior. This can be understood as a topological mechanism that is robust against deformations of the triangle. Geometry and topology induce a rich internal structure due to the high-dimensional tuning parameter space of 3D structures, inaccessible to the conventional 2D design strategies in thin films.