Extremely Correlated Superconductors

TL;DR

This paper extends the extremely correlated Fermi liquid theory to study superconductivity in the t-J model, deriving equations for the superconducting gap and estimating the critical temperature near half-filling.

Contribution

It introduces a generalized framework for analyzing superconductivity in strongly correlated systems, providing an approximate formula for T_c applicable to high-T_c materials.

Findings

Superconductivity with T_c around 100K is predicted near half-filling.

Derived an analytical formula for T_c based on a reduced quasiparticle weight.

Identified a narrow electron density range where high-temperature superconductivity occurs.

Abstract

Superconductivity in the t-J model is studied by extending the recently introduced extremely correlated fermi liquid theory. Exact equations for the Greens functions are obtained by generalizing Gor'kov's equations to include extremely strong local repulsion between electrons of opposite spin. These equation are expanded in a parameter $\lambda$ representing the fraction of double occupancy, and the lowest order equations are further simplified near $T_c$, resulting in an approximate integral equation for the superconducting gap. The condition for $T_c$ is studied using a model spectral function embodying a reduced quasiparticle weight $Z$ near half-filling, yielding an approximate analytical formula for $T_c$. This formula is evaluated using parameters representative of single layer High-$T_c$ systems. In a narrow range of electron densities that is necessarily separated from the Mott-Hubbard insulator at half filling, we find superconductivity with a typical $T_c$$\sim$$10^2$K.