The extended Hubbard model applied to phase diagram and the pressure effects in \Bi superconductors

TL;DR

This paper employs an extended Hubbard model with a BCS approach to analyze the phase diagram and pressure effects in ext{Bi} superconductors, providing insights into Cooper pairing and reproducing experimental data.

Contribution

It introduces a novel method using the extended Hubbard Hamiltonian to connect superconducting properties with pressure effects in high-Tc superconductors.

Findings

The model explains the variation of $T_c$ with hole content.

It reproduces the experimental phase diagram $T_c$ vs. $n$.

It predicts how pressure increases the attractive potential and $T_c$.

Abstract

We use the two dimensional extended Hubbard Hamiltonian with the position of the attractive potential as a variable parameter with a BCS type approach to study the interplay between the superconductor transition temperature $T_c$ and hole content for high temperature superconductors. This novel method gives some insight on the range and intensity of the Cooper pair interaction and why different compounds have different values for their measured coherence lengths and it describes well the experimental results of the superconducting phase diagram $T_c \times n$. The calculations may also be used to study the effect of the applied pressure with the assumption that it increases the attractive potential which is accompanied by an increase in the superconductor gap. In this way we obtain a microscopic interpretation for the intrinsic term and a general expansion for $T_c$ in terms of the pressure which reproduces well the experimental measurements on the \Bi superconductors.