Anisotropic Strong Coupling Calculation of the Local Electromagnetic Response of High-Tc Superconductors

TL;DR

This paper models the electromagnetic response of high-Tc superconductors using anisotropic strong coupling theory, incorporating spin fluctuations and phonons, to better match experimental observations of penetration depth and quasiparticle interactions.

Contribution

It introduces a detailed anisotropic strong coupling calculation for high-Tc superconductors considering momentum-dependent interactions and phonons, improving agreement with experimental data.

Findings

Inclusion of phonons enhances the temperature dependence of the order parameter.

The quasiparticle interaction strength decreases with temperature in the superconducting state.

The model's accuracy depends on the momentum dependence of interactions and Fermi surface details.

Abstract

The electromagnetic response of the CuO2-planes is calculated within a strong coupling theory using model tight binding bands and momentum dependent pairing interactions representing spin fluctuations and phonon exchange. The superconducting state resulting from these interactions has d-wave symmetry. With phonon exchange included the order parameter amplitude grows rapidly below Tc at elevated frequencies which leads to improved agreement with the observed temperature dependence of the penetration depth. Good agreement between theory and experiment can only be achieved if it is assumed that the strength of the quasiparticle interaction decreases with temperature in the superconducting state. The amount of this reduction depends sensitively on the momentum dependence of the interactions, the energy dispersion and the position of the Fermi line.