The two classical models for the moving vortex, one suggested by Bardeen and Stephen ͑BS͒ and the other by Noziéres and Vinen ͑NV͒, are incompatible regarding the nature of normal core current upon which the dissipation characteristics depend. In order to resolve this ambiguity, we generalize the BS model by including the nonlinear convection term. This nonlinear generalization leads to an additional electric field inside and outside the core which was not accounted for in the BS model. The electric force field in the core is found to be identical to the NV model. Using this field, we determine the normal core current and the rate of energy dissipation in the core. The rate of energy dissipation allows us to determine the drag coefficients proposed by Hagen et al. From these coefficients, we demonstrate the appearance of the negative Hall angle if the effective pinning force is small compared to the Lorentz force.

In order to find the microscopic origin of the components of the paramagnetic current generated in a moving vortex core, we present a perturbation method to solve the Bogoliubov-de Gennes equations for a moving vortex in clean type-II superconductors. The paramagnetic current and its associated dissipation at the moving vortex core are shown to result from intrinsic concommitant effects. From the present perturbation approach involving no presupposition of the Magnus force, the long-standing problem of the validity of the two different classical models is discussed. The components of the derived paramagnetic current are found to be identical to the classical model of Noziéres and Vinen. ͓S0163-1829͑98͒03809-0͔

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Effects of nonmagnetic impurities on optical conductivity in the systems of antiferromagnetically correlated electrons are examined based on the Lanczos exact diagonalization scheme. As a result of resonant scattering a lowfrequency peak in the optical conductivity is predicted to occur in the presence of the nonmagnetic impurities, which is consistent with the observed normalstate optical conductivity of YBa 2 (Cu 1−x Zn x ) 3 O 7−δ . In addition, a relatively high and broad peak is found to occur at a high frequency region as a consequence of the Heisenberg interaction between electrons, in agreement with observation in the peak position.