Neutral-ionic transition and dimerization in organic mixed-stack compounds

Abstract

Using a generalized Hubbard model, we study the neutral-ionic transition and the stability of dimerized phases in mixed-stack compounds by means of the real-space renormalization-group technique. The model includes hybridization between the relevant orbitals of the donor and acceptor molecules, intramolecular Coulomb repulsion which is taken to be infinite to avoid double ionization, and nearest-neighbor electron-electron interactions. We present the phase diagram, the occupation of the donor (acceptor) molecules, and the minimum electron-hole excitation energies for different values of the parameters.