The boson mediators of high-Tc superconductivity: phonons versus composite bosons from the superconducting phenomenology

TL;DR

This paper investigates whether high-Tc superconductivity is mediated by composite electronic bosons or phonons, concluding that experimental evidence favors phonons, especially considering electron-phonon coupling modulation effects.

Contribution

The study provides evidence against composite bosons as mediators and supports phonons as the primary mechanism in high-Tc superconductivity, incorporating effects of Coulomb correlations.

Findings

Experimental data disfavors composite bosons as mediators.

Phonon-mediated pairing explains observed microwave and NMR phenomena.

Forward scattering electron-phonon coupling modulation accounts for temperature-dependent features.

Abstract

We address the question of whether boson mediators of high-$T_c$ superconductivity are composite (electronic) or independent phonons. For s-wave superconductivity we show from the available experiments that the hypothesis of composite bosons is rather unlikely. Our analysis points naturally towards phonon mediators. In addition we point out that the eventual presence of a peak in the temperature dependence of the microwave conductivity while the Hebel-Slichter peak is absent in the temperature dependence of the NMR relaxation rate, can be understood within a phonon mechanism if one takes into account the modulation of the electron-phonon coupling (predominance of forward scattering) induced by Coulomb correlation of the carriers.