Dynamic Jahn-Teller effect and superconducting excitations in Raman spectra

TL;DR

This paper models the Raman spectra of high-Tc superconductors, revealing how superconducting and Jahn-Teller gaps produce distinct peaks and how dynamic Jahn-Teller interactions influence these features.

Contribution

It introduces a theoretical model combining static and dynamic Jahn-Teller effects with superconductivity to predict Raman spectral features in high-Tc materials.

Findings

Two excitation peaks correspond to SC and Jahn-Teller gaps.

Dynamic Jahn-Teller coupling suppresses JT gap and enhances SC gap.

Model predicts evolution of spectral peaks with system parameters.

Abstract

We report a model study of the phonon response on the interplay of the superconducting (SC) gap and both static and dynamic Jahn-Teller distortion and predict the appearance of the SC and Jahn-Teller (JT) distortion gap excitation peaks in the Raman spectra of high-Tc superconductors. The model consists of the Hamiltonian containing static JT interaction and s-wave type SC interaction in the conduction band. Further the phonons are coupled to the density of the conduction electron in the band as well as to the JT split conduction band giving rise to dynamic Jahn-Teller (DJT) interaction. The phonons are considered in a harmonic approximation. The phonon Green's function is calculated by Zubarev's technique and the phonon self-energy arising due to normal electron-phonon (EP) interaction and DJT interaction. The phonon self-energy arising due to this is calculated from the electron response density function in the coexistence phase of the two order parameters. The phonon spectral density predicts two excitation peaks, one due to SC gap and the other due to JT distortion. The DJT coupling suppresses the JT gap while it enhances SC gap as well as SC transition temperature. The evolution of these excitation peaks are investigated by varying different model parameters of the system.