Effect of Coulomb repulsion on the London penetration depth in cuprate superconductors

TL;DR

This paper investigates how Coulomb repulsion affects the London penetration depth in cuprate superconductors, showing that including Coulomb interactions improves agreement with experimental data.

Contribution

It demonstrates that accounting for Coulomb interactions within the spin-fermion model enhances the theoretical match to experimental penetration depth data in cuprates.

Findings

Coulomb interactions improve the theoretical fit to experimental data.

Including Hubbard U_p and V_2 interactions aligns calculations with observations.

The model explains the temperature dependence of the penetration depth.

Abstract

We study the effect of Coulomb repulsion between oxygen holes on the London penetration depth $\lambda$ based on the concept of spin-polaron nature of Fermi quasiparticles in cuprates superconductors. It is shown that for the generally accepted values of the parameters of the spin-fermion model, taking into account the Coulomb interaction, both the one-site Hubbard $U_p$ and interaction between the holes on next-nearest-neighbor oxygen ions $V_2$, allows one to achieve a much better agreement of the calculated temperature dependencies of the value $\lambda^{-2}$ with the experimental data in La$_{2-x}$Sr$_{x}$CuO$_4$ in a wide range around optimal doping.