Anomalous Self-Energy Effects of the B_1g Phonon in Y_{1-x}(Pr,Ca)_xBa_2Cu_3O_7 Films

TL;DR

This paper investigates how the B_1g phonon in cuprate superconductors is affected by electronic gap features and anomalies, using a model to analyze Raman spectra across different doping levels.

Contribution

It introduces a model that simultaneously studies electronic redistribution and phonon self-energy effects in cuprates, highlighting unexplained anomalies.

Findings

Self-energy effects correlate with 2Δ peak properties.

Anomalies in phonon behavior suggest additional mechanisms.

Model explains some effects but leaves certain anomalies unresolved.

Abstract

In Raman spectra of cuprate superconductors the gap shows up both directly, via a redistribution of the electronic background, the so-called "2Delta peaks", and indirectly, e.g. via the renormalization of phononic excitations. We use a model that allows us to study the redistribution and the related phonon self-energy effects simultaneously. We apply this model to the B_1g phonon of Y_{1-x}(Pr,Ca)_xBa_2Cu_3O_7 films, where Pr or Ca substitution enables us to investigate under- and overdoped samples. While various self-energy effects can be explained by the strength and energy of the 2\Delta peaks, anomalies remain. We discuss possible origins of these anomalies.