Electronic correlations in Peierls systems

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Abstract
For a general class of correlated electron-phonon systems (1d generalised Peierls-Hubbard models) it is shown that the explicit electron-electron interaction can be eliminated exactly by a unitary transformation, resulting in an effective electron-lattice coupling. The transformed Hamiltonians may serve as a better starting point for analytical and numerical calculations. The properties of the transformations are illustrated in two limiting cases: in a two-site model and in the atomic limit. Furthermore, a variational ansatz for the ground state is proposed.