Further evidence for linearly-dispersive Cooper pairs

TL;DR

This paper provides empirical evidence supporting the existence of linearly-dispersive Cooper pairs in various superconductors, by improving BEC model fits to experimental data across different dimensionalities, challenging traditional quadratic dispersion assumptions.

Contribution

It demonstrates that assuming linearly-dispersive Cooper pairs improves BEC model fits to superconducting data across 2D, 3D, and nanotube systems, supporting a revised understanding of pairing.

Findings

Improved fit of penetration-depth data with quasi-2D models

Linearly-dispersive pairs better explain experimental data

Supports BEC scenario with non-quadratic dispersion in superconductors

Abstract

A recent Bose-Einstein condensation (BEC) model of several cuprate superconductors is based on bosonic Cooper pairs (CPs) moving in 3D with a quadratic energy-momentum (dispersion) relation. The 3D BEC condensate-fraction vs. temperature (T/Tc, where Tc is the BEC transition temperature) formula poorly fits penetration-depth data for two cuprates in the range (1/2, 1]. We show how these fits are dramatically improved assuming cuprates to be quasi-2D, and how equally good fits obtain for conventional 3D and quasi-1D nanotube superconducting data, provided the correct CP dispersion is assumed in BEC at their assumed corresponding dimensionalities. This is offered as additional concrete empirical evidence for linearly-dispersive pairs in another recent BEC scenario of superconductors within which a BCS condensate turns out to be a very special case.