Universal Diagnostic Criterion for Intrinsic Superconducting Diode Effect

Abstract: The intrinsic superconducting diode effect (SDE) is distinguished from the Josephson diode effect (JDE) by its manifestation of nonreciprocal critical current phenomena within a monolithic superconductor, typically linked to finite-momentum Cooper pairing. The long-standing assumption that SDE requires co-breaking of time-reversal and inversion symmetries proves to be necessary but not sufficient. In this work, we propose a universal diagnostic criterion. Embodied in two concise inequalities, this criterion enables convenient and intuitive assessment of whether an intrinsic SDE can emerge in a given system without requiring extensive numerical calculations. Furthermore, our universal criterion provides explicit design guidelines for material systems exhibiting intrinsic SDE.