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 low-frequency peak in the optical conductivity is predicted to occur in the presence of the nonmagnetic impurities, which is consistent with the observed normal-state optical conductivity of ${ \rm YBa_2}({ \rm Cu}_{ 1-x}{ \rm Zn}_x)_3{ \rm O}_{ 7-\delta}$. 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.
Categories: cond-mat.str-el