Dynamical properties of the twodimensional HolsteinHubbard model in the normal state at z.pdfVIP

PHYSICAL REVIEW B VOLUME 58, NUMBER 7 15 AUGUST 1998-I Dynamical properties of the two-dimensional Holstein-Hubbard model in the normal state at zero temperature: A fluctuation-based effective cumulant approach ˘ T. Hakioglu Physics Department, Bilkent University, 06533 Ankara, Turkey M. Ye. Zhuravlev N. S. Kurnakov Institute of General and Inorganic Chemistry of the Russian Academy of Sciences, 31 Leninsky Prospect, GSP-1, 117 907 Moscow, Russia Received 23 February 1998 The two-dimensional many-body Holstein-Hubbard model in the T 0 normal state is examined within the framework of the self-consistent coupling of charge fluctuation correlations to the vibrational ones. The pa- rameters 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 examine the T 0 normal-state fluctuations and an analytic approximation to the true dynamical entangled ground state is suggested. Our results for the effective charge-transfer amplitude, the ground state energy, the fluctuations in the phonon population, the phonon softening as well as the coupling constant renormalizations suggest that, the ´ˇ