Interplay of Pairing Correlation and Coulomb Correlation in Boson Exchange Superconductors

TL;DR

This paper develops a theoretical method to analyze how many-body correlations influence BCS superconductivity, revealing the significant impact of Coulomb correlation on the pairing gap and superconducting properties.

Contribution

It introduces a variational scheme using Gutzwiller projection to incorporate many-body correlations into BCS theory, providing a self-consistent gap equation dependent on correlation strength.

Findings

Coulomb correlation significantly affects the pairing gap.

In the zero correlation limit, results recover standard BCS formalism.

The methodology explicitly links many-body correlations with superconducting properties.

Abstract

A theoretical methodology for exploring the conventional Bardeen-Cooper-Schrieffer (BCS) pairing instability for superconductivity from a correlated normal phase for all possible degrees of many-body correlation, has been developed. The Gutzwiller projection scheme with a correlation parameter was made use of in generating the BCS pairing state. A variational scheme was thereafter implemented, leading to a self-consistent equation for superconducting gap function. This equation shows explicit dependence of the gap function on the many body correlation parameter. This `pairing-gap' and the corresponding self-consistent gap equation in zero correlation limit, becomes identical in nature with those of the pure (1-well) BCS formalism, as expected and the Coulomb correlation affects the pairing significantly with the strength of correlation. The detailed consequences are being presented here.