Pseudospin-Electron Model in Large Dimensions

TL;DR

This paper investigates the energy spectrum and thermodynamics of the pseudospin-electron model in large dimensions, revealing phase transitions and phase separation phenomena relevant to high-$T_c$ superconductors.

Contribution

It provides an exact analytical solution in the zero electron correlation limit within the dynamical mean field approximation, exploring phase transitions and phase separation.

Findings

First order phase transition with pseudospin jump

Reconstruction of the electron spectrum during transition

Possible phase separation in electron subsystem

Abstract

Energy spectrum and thermodynamics of the pseudospin-electron model introduced at the consideration of the anharmonicity effects in high-$T_c$ superconductors are investigated in the dynamical mean field approximation ($d=\infty$ limit). In the limit of zero electron correlation $U\to 0$ this model is analytically exactly soluble within this approach: in the $\mu=const$ regime the first order phase transition with the jump of the pseudospin mean value $<S^z>$ and reconstruction of the electron spectrum can realize, while in the $n=const$ regime the phase separation in electron subsystem can take place for certain values of the model parameters. On the basis of the obtained results the applicability of the approximate schemes previously used for the investigation of the pseudospin-electron model are discussed.