Josephson Junctions Without Pairing?

TL;DR

This paper explores an alternative real-space model of superconductivity that challenges the traditional pairing mechanism, extending it to explain the Josephson effect and predicting deviations at nanoscale dimensions.

Contribution

It introduces a real-space electron model for superconductivity that reproduces Josephson effects and offers new insights into nanoscale superconductor behavior.

Findings

Josephson effect can be derived without Cooper pairing.

Standard BCS formalism can be supported by this microstructure.

Predicted deviations in Josephson behavior for nanoscale SQUIDs.

Abstract

It is well established that superconductivity is based on a coherent quantum state of Cooper pairs with charge 2e, and this is equally true of the Josephson effect. In contrast, Kadin recently presented an alternative real-space model of the superconducting ground state, in which each electron is a localized orbital, on the scale of the coherence length, coupled to a dynamic charge (or spin) density wave. A supercurrent corresponds to collective motion of a dense orthogonal array of such electrons. The present paper extends this analysis to two weakly coupled superconductors, and shows how the Josephson effect (including the ubiquitous factor of h/2e) may be obtained. Furthermore, much of the standard BCS formalism on the macroscale follows from this microstructure. However, major deviations from standard Josephson behavior are predicted for nanoscale SQUIDs much smaller than the coherence length.