The spatially localized bound states of two electrons in the adiabatic two-dimensional HolsteinHubbard model on a square lattice are investigated both numerically and analytically. The interplay between the electron-phonon coupling g, which tends to form bipolarons and the repulsive Hubbard interaction υ ≥ 0, which tends to break them, generates many different ground-states. There are four doma...

A thermochemical investigation of singlet dication (bipolaron) structures in a set of 3-methyl-thiophene oligomers (up to the length of 24-mers) was carried out. Equlibrium structures and heats of formation were calculated with the semiempirical quantum chemical method RHF/PM3 for the doubly oxidized forms. All-cisoid planar structural variants of the form An1Qn2An3 were considered, where A and...

We use the density matrix renormalization group method to study a one-dimensional chain with Peierls electron-phonon coupling, which describes modulation of electron hopping by lattice distortions. demonstrate that this system is stable against phase separation in dilute limit. only find numerically for large couplings linear approximation coupling becomes invalid; behavior can be stabilized na...

Exciton effects on soliton and bipolaron lattice states are investigated using an electron-lattice Peierls model with long-range Coulomb interactions. The Hartree-Fock (HF) approximation and the single-excitation configurationinteraction (single-CI) method are used to obtain optical absorption spectra. We discuss the following properties: (1) The attraction between the excited electron and the ...

Based on the spin-blockade model for organic magnetoresistance, we present an analytic expression for the polaron-bipolaron transition rate, taking into account the effective nuclear fields on the two sites. We reveal the physics behind the qualitatively different magnetoconductance line shapes observed in experiment, as well as the ultrasmall magnetic field effect (USFE). Since our findings ag...