We show that in anharmonic one-dimensional crystal lattices pairing of electrons or holes in a localized bisolectron state is possible due to the coupling between the charges and the lattice deformation that can overcome the Coulomb repulsion. Such localized states appear as traveling ground singlet states of two extra electrons bound in the potential well created by the local lattice solitonlike deformation. We also find the first excited localized state of two electrons given by a triplet state of two electrons. The results of the analytical study of interacting electrons in a lattice with cubic anharmonicity are compared with the numerical simulations of two electrons in an anharmonic lattice with Morse interactions and taking into account the single-site Hubbard electron-electron repulsion. We find quite a good qualitative agreement between both approaches for a broad range of parameter values. For illustration we give expressions for the bisolectron binding energy with parameter values that are typical for biological macromolecules. We also estimate threshold values of the Coulomb repulsion above which the bisolectron splits into two solectrons.

• Received 1 March 2012

DOI:https://doi.org/10.1103/PhysRevB.85.245105