A Kapitza Pendulum Route to Supercurrent Tunnel Diodes

TL;DR

This paper introduces a novel method to achieve nonreciprocal supercurrent flow in superconducting devices by dynamically modulating the supercurrent amplitude, inspired by the Kapitza pendulum, enabling nonreciprocal transport without magnetic or spin-orbit effects.

Contribution

The authors propose a dynamical approach using parametric driving to break reciprocity in Josephson junctions, creating the concept of a Kapitza supercurrent diode with practical implementation schemes.

Findings

Demonstrated nonreciprocal supercurrent via frequency modulation

Established mathematical analogy with the Kapitza pendulum

Proposed feasible device implementations at GHz frequencies

Abstract

Superconducting diodes that support nonreciprocal supercurrent flow in principle constitute attractive, non-dissipative, circuit elements for superconducting electronics. But their realization faces fundamental challenges, as conventional Josephson tunnel junctions are inherently reciprocal. Existing approaches to break reciprocity typically involve magnetism or spin-orbit coupling, which often increase device complexity and limit reproducibility. Here, we demonstrate an alternative dynamical route to supercurrent nonreciprocity based on parametric driving. By applying a frequency-modulated supercurrent amplitude we show that effective higher-order, nonharmonic terms are generated in the current-phase relation. Leveraging mathematical equivalences with the Kapitza pendulum, we show that these terms dynamically break reciprocity. This establishes the concept of a Kapitza supercurrent diode and demonstrates that nonreciprocal superconducting transport can be engineered by nonequilibrium driving conventional Josephson tunnel junctions. We propose two implementations of the Kapitza supercurrent diode - via gate-controlled superconducting interferometers or flux-driven double-loop SQUIDs - to achieve nonreciprocal supercurrent transport within experimentally accessible frequencies $\omega/2\pi \sim 1$-$10\,\mathrm{GHz}$.