Molecular crystal approach for pi-conjugated polymers: from PPP Hamiltonian to Holstein model for polaron states

TL;DR

This paper develops a theoretical framework for conjugated polymers starting from the PPP Hamiltonian, deriving a Holstein-like model to study polaron states with improved correlated wave functions.

Contribution

It introduces a new wave function approach for conjugated polymers based on local configurations, connecting the PPP Hamiltonian to a Holstein model for polarons.

Findings

Wave functions of increasing quality for ground states

Connection between PPP Hamiltonian and Holstein model for polarons

Framework for studying doped conjugated polymers

Abstract

Starting from the $\pi$-electron Pariser-Parr-Pople (PPP) Hamiltonian which includes both strong electron-phonon and electron-electron interactions, we propose some strongly correlated wave functions of increasing quality for the ground state of conjugated polymers. These wavefunctions are built by combining different finite sets of local configurations extended at most over two nearest-neighbour monomers. With this picture, the doped case with one additional particle is expressed in terms of quasi-particle. Thus, the polaron formation problem goes back to the study of a Holstein like model.