Microscopic Bardeen-Cooper-Schrieffer formulation of the critical temperature of multilayer copper-oxide superconductors

TL;DR

This paper develops a microscopic BCS-based model to explain the critical temperature variations in multilayer copper-oxide superconductors, successfully matching experimental data for different layer configurations and intercalating elements.

Contribution

It introduces a detailed microscopic formulation that captures the dependence of Tc on layer number and doping imbalance, aligning with experimental observations.

Findings

Maximum Tc occurs at 3 or 4 CuO2 layers with negative pair tunneling.

The model accurately fits Tc for 1-4 layers across five copper oxide families.

Doping imbalance between layers influences the superconducting transition temperature.

Abstract

We study superconductivity in multilayer copper oxides, in the frame of a realistic microscopic formulation. Solving the full temperature dependent BCS gap equations, we obtain a maximum in the transition temperature Tc for M=3 or 4 CuO2 layers in the unit cell for appropriate values of the interlayer tunneling (negative pair tunneling), and via the consideration of the doping imbalance between the inner and outer layers. This is the ubiquitous experimental result for Ca intercalated copper oxides, as opposed to other intercalating elements. Further, using a restricted set of parameters, we obtain an exact fit of Tc(M=1-4) for five different Ca intercalated homologuous copper oxide families.