Field-Free Superconducting Diode Enabled by Geometric Asymmetry and Perpendicular Magnetization.

Abstract

The superconducting diode effect (SDE), which manifests as directional, dissipationless supercurrents, is pivotal for realizing energy-efficient superconducting logic and memory technologies. However, achieving high-efficiency SDE without external magnetic fields remains a fundamental challenge. In this study, a strongly enhanced, field-free SDE in Pt/Co/Nb heterostructures are proposed, enabled by the interplay of engineered geometric asymmetry and stray fields from a perpendicularly magnetized Co layer. This configuration promotes directional vortex entry and spatially selective pinning, yielding diode efficiencies that exceed all previously reported field-free values in ferromagnet/superconductor multilayers. Temperature- and field-dependent transport measurements, supported by micromagnetic simulations, reveal that the enhanced nonreciprocity results from three cooperative mechanisms: asymmetric vortex entry, localized magnetic pinning, and Lorentz-force imbalance. These findings establish a CMOS-compatible platform for high-performance superconducting rectifiers, offering new opportunities for cryogenic spintronics and quantum electronics.