  Optical conductivity spectra are studied for the Falicov-Kimball model with
correlated hopping on the Bethe lattice. An expression for the current-current
correlation function is derived using dynamical mean field theory. In the
metallic phase with small correlated hopping values, the shape of Drude peak
deviates from the Debye relaxation peak, and an additional wide peak is
observed on the optical conductivity spectra and on Nyquist plot when Fermi
level is in the vicinity of the two particle resonance. At larger values of the
correlated hopping parameter, the density of states contains three bands and
the corresponding optical spectra and Nyquist plots display a more complicated
shape with additional peaks. For strong local correlations, the correlated
hopping reduces the width of the upper Hubbard band resulting in a decrease of
the Drude peak spectral weight for the doped Mott insulator.

Strongly Correlated Electrons