SU(2)-path integral investigation of Holstein dimer

The SU(2) coherent state path integral is used to investigate the partition function of the Holstein dimer. This approach naturally takes into account the symmetry of the model. The ground-state energy and the number of the phonons are calculated as functions of the parameters of the Hamiltonian. The renormalizations of the phonon frequency and electron orbital energies are considered. The destruction of quasiclassical mean-field solution is discussed.