The one-dimensional (1D) large bipolaron is investigated in the limit of strong electron-phonon coupling. The nonlinear integro-differential equation for the bipolaron wave function is solved numerically, from which we obtained estimates for the main characteristics. An enlargement of the stability region for the bipolaron ground state is found in 1D as compared to the stability regions in 2D and 3D. The energy of the first relaxed excited state (RES) equals the energy of two single polarons and the ground state in the potential generated by the first RES has a slightly lower energy than this RES and is therefore stable. The nonlinearity causes the feature that the combination of the ground state and an excited state of one-particle wave functions could lead to a higher bipolaron energy than the combination of two excited states.

• Received 6 July 1994

DOI:https://doi.org/10.1103/PhysRevB.50.12524