Universal Criterion and Graph-Theoretic Construction of Intrinsic Superconducting Diode Effect

TL;DR

This paper introduces a universal diagnostic criterion for the intrinsic superconducting diode effect, based on inequalities from the Hamiltonian, and presents a graph-theoretic construction for designing nonreciprocal models.

Contribution

It proposes a universal criterion for intrinsic SDE and develops a graph-theoretic method for constructing nonreciprocal superconducting models.

Findings

The criterion is expressed as two inequalities from the Hamiltonian.

The graph-theoretic construction offers new design principles for nonreciprocal models.

The criterion extends beyond superconductivity to broader nonreciprocal systems.

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 for intrinsic SDE, expressed as two inequalities evaluated directly from the bare Hamiltonian. This criterion further reveals a graph-theoretic construction for nonreciprocal models, offering design principles that extend beyond superconductivity.