Eur. Phys. J. B (2014) 87: 154
https://doi.org/10.1140/epjb/e2014-50146-9

Regular Article

Self-trapping phase diagram for the strongly correlated extended Holstein-Hubbard model in two-dimensions

School of Physics, University of Hyderabad, Hyderabad 500046, India

^a e-mail: acsp@uohyd.ernet.in

Received: 4 March 2014
Received in final form: 18 April 2014
Published online: 16 July 2014

Abstract

The two-dimensional extended Holstein-Hubbard model is investigated in the strong correlation regime to study the nature of self-trapping transition and the polaron phase diagram in the absence of superconductivity. Using a series of canonical transformations followed by zero-phonon averaging the extended Holstein-Hubbard model is converted into an effective extended Hubbard model which is subsequently transformed into an effective t-J model in the strong correlation limit. This effective t-J model is finally solved using the mean-field Hartree-Fock approximation to show that the self-trapping transition is continuous in the anti-adiabatic limit while it is discontinuous in the adiabatic limit. The phase diagrams for the localization-delocalization transition, namely the phase line and the phase surface separating the small polaron and large polaron states are also shown.