Polaronic signatures in the optical properties of   Nd$_{2-x}$Ce$_x$CuO$_4$
  We investigate the temperature and doping dependence of the optical conductivity $\sigma(\omega)$ of Nd$_{2-x}$Ce$_x$CuO$_4$ in terms of magnetic/lattice polaron formation. We employ dynamical mean-field theory in the context of the Holstein-t-J model where an exact analytical solution is available in the limit of infinite connectivity. We show that the pseudogap features in the optical conductivity of this compound can be associated to the formation of lattice polarons assisted by the magnetic interaction. 
E. Cappelluti, S. Ciuchi, and S. Fratini