Coexistence of Band Jahn Teller Distortion and superconductivity in correlated systems

TL;DR

This paper investigates how band Jahn-Teller distortions coexist with superconductivity in correlated systems, revealing that structural distortions suppress superconductivity and limit the critical temperature, with a detailed phase diagram analysis.

Contribution

It introduces a model combining Jahn-Teller effects, superconductivity, and electron correlations to study their interplay and phase diagram in correlated materials.

Findings

Structural distortion suppresses superconductivity.

Superconductivity onset arrests lattice distortion growth.

Maximum $T_c$ limited by structural transition at optimal doping.

Abstract

The co-existence of band Jahn-Teller (BJT) effect with superconductivity (SC) is studied for correlated systems, with orbitally degenerate bands using a simple model. The Hubbard model for a doubly degenerate orbital with the on-site intraorbital Coulomb repulsion treated in the slave boson formalism and the interorbital Coulomb repulsion treated in the Hartree-Fock mean field approximation, describes the correlated system. The model further incorporates the BJT interaction and a pairing term to account for the lattice distortion and superconductivity respectively. It is found that structural distortion tends to suppress superconductivity and when SC sets in at low temperatures, the growth of the lattice distortion is arrested. The phase diagram comprising of the SC and structural transition temperatures $T_c$ and $T_s$ versus the dopant concentration $\delta $ reveals that the highest obtainable $T_c$ for an optimum doping is limited by structural transition. The dependence of the occupation probabilities of the different bands as well as the density of states (DOS) in the distorted-superconducting phase, on electron correlation has been discussed.