Resonant Raman Study of Superconducting Gap and Electron-Phonon Coupling in YbBa2Cu3O7-delta

TL;DR

This study uses resonant Raman spectroscopy to analyze the superconducting gap and electron-phonon interactions in highly doped YbBa2Cu3O7-delta, revealing how electronic background and phonon coupling change across the superconducting transition.

Contribution

It introduces a model to separate electronic background and phonon contributions, elucidating the energy-dependent electron-phonon coupling in YbBa2Cu3O7-delta.

Findings

Superconducting gap opens below Tc with a 2Delta peak at 320 cm^-1.

Electronic background shows minimal resonance between 1.96 eV and 2.71 eV.

Interband electronic contributions to phonon coupling vanish below Tc at 1.96 eV.

Abstract

We investigate the electronic background as well as the O2-O3 mode at 330 cm^-1 of highly doped YbBa2Cu3O7-delta in B1g symmetry. Above the critical temperature Tc the spectra consist of an almost constant electronic background and superimposed phononic excitations. Below Tc the superconducting gap opens and the electronic background redistributes exhibiting a 2Delta peak at 320 cm^-1. We use a model that allows us to separate the background from the phonon. In this model the phonon intensity is assigned to the coupling of the phonon to inter- and intraband electronic excitations. For excitation energies between 1.96 eV and 2.71 eV the electronic background exhibits hardly any resonance. Accordingly, the intraband contribution to the phonon intensity is not affected. In contrast, the interband contribution vanishes below Tc at 1.96 eV while it remains almost unaffected at 2.71 eV.