DYNAMICAL PROPERTIES OF THE 2-DIMENSIONAL HOLSTEIN-HUBBARD MODEL IN THE NORMAL-STATE AT ZERO-TEMPERATURE - A FLUCTUATION-BASED EFFECTIVE CUMULANT APPROACH

The two-dimensional many-body Holstein-Hubbard model in the T=0 normal state is examined within the framework of the self-consistent couplin g of charge fluctuation correlations to the vibrational ones. The para meters of our model are the adiabaticity, the electron concentration, as well as the electron-phonon and the Coulomb interaction strengths; A fluctuation-based effective cumulant approach is introduced to exami ne the T=0 normal-state fluctuations and an analytic approximation to the true dynamical entangled ground state is suggested. Our results fo r the effective charge-transfer amplitude, the ground state energy, th e fluctuations in the phonon population, the phonon softening as well as the coupling constant renormalizations suggest that, the recent num erical calculations of de Mello and Ranninger (Ref. 5), Berger, Valase k, and von der Linden (Ref. 2), and Marsiglio (Refs. 4 and 8) on syste ms with finite degrees of freedom can be qualitatively extended to the systems with large degrees of freedom.