Abstract
We study an undoped model with electron-phonon interaction using the self-consistent Born approximation (SCBA). By neglecting vertex corrections, the SCBA solves a boson-holon model, where a holon couples to phonons and magnons. Comparison with exact diagonalization results for the model suggests that the SCBA describes the electron-phonon interaction fairly accurately over a substantial range of values. Exact diagonalization of the boson-holon model shows that the deviations are mainly due to the neglect of vertex corrections for small and due to the replacement of the model by the boson-holon model for large . For typical values of , the electron-phonon part of the electron self-energy has comparable contributions from the second-order diagram in the electron-phonon interaction and a phonon-induced change of magnon diagrams. A very simple approximation to gives a rather accurate effective mass. Using this approximation, we study the factors influencing the electron-phonon interaction. Typically, we find that the magnons nominally have a stronger coupling to the holon than the phonons. The phonons, nevertheless, drive the formation of small polarons (self-localization) due to important differences between the character of the phonon and magnon couplings.
- Received 14 February 2006
DOI:https://doi.org/10.1103/PhysRevB.73.174521
©2006 American Physical Society