Layered superconductors with long-range Josephson couplings

TL;DR

This paper extends layered superconductor models to include long-range Josephson and proximity couplings, analyzing their effects on superconductivity enhancement and linking coupling constants to microscopic interactions and measurable quantities.

Contribution

It introduces a hybrid discrete-continuous model with arbitrary long-range interactions, including proximity effects, and analyzes the K=2 case for the first time.

Findings

Long-range interactions can enhance superconductivity.

The model links coupling constants to microscopic Cooper pair interactions.

Solutions for the K=2 case reveal the role of higher Josephson couplings.

Abstract

The present paper is an extension of 'cond-mat/0312673'. The construction of a hybrid discrete-continuous model of layered superconductors is presented. The model bases on the classic Lawrence-Doniach scenario with admitting, however, long-range interactions between atomic planes. Moreover, apart from Josephson couplings they involve the proximity effects. The range of interactions can, in principle, be arbitrary large. The solutions corresponding to the range K=2 are found. The mechanism of enhancement of superconductivity caused by the proximity effect and the presence of higher Josephson couplings is shown. The physical meaning of coupling constants, with particular attention paid to their sign, is discussed. For the case K=2 the interpretation in terms of microscopic interactions between Cooper pairs in different planes, as well as the relation to experimentally measurable quantities, such as the out-of-plane effective mass and bandwidth, is given.