Modified BCS gap equation for Jahn-Teller distorted high temperature superconductors

TL;DR

This paper develops a modified BCS gap equation to explore how electron-phonon interactions, Jahn-Teller distortions, and lattice strain influence high-temperature superconductivity, revealing new effects distinct from static strain alone.

Contribution

It introduces a modified BCS gap equation incorporating Jahn-Teller effects and lattice strain, providing new insights into high-temperature superconductor behavior.

Findings

Modified conduction band energy and order parameter due to Jahn-Teller effects.

Interplay between electron-phonon interaction, Jahn-Teller distortion, and superconductivity.

Distinct effects of Jahn-Teller distortion compared to static lattice strain.

Abstract

In this communication we report the interplay of the normal electron-phonon (EP) interaction, dynamic Jahn-Teller (DJT) distortion and superconductivity in high temperature superconductors in presence of a static lattice strain. This model consists of a degenerate two orbital band separated by Jahn-Teller (JT) energy modified by the DJT interaction in the conduction band. The superconductivity is assumed to be s-wave type present in the same band. The interaction Hamiltonian is solved by Green's function method and a modified BCS gap equation is obtained with a modified conduction band energy $\tilde{\epsilon}_{\alpha k}$ and modified BCS order parameter $\tilde{\Delta}_{\alpha}$ with $\alpha=1, 2$ designating the two orbitals. This interplay displays some new interesting results which are different from the effect of the static lattice strain on superconducting (SC) order parameter. The interplay is studied by varying the normal EP coupling, the DJT coupling, the SC coupling, the phonon vibration frequency, the phonon wave vector and other model parameters of the system.