Impurity Effects in Strongly Correlated Metals: Large Pressure Dependence of Residual Resistivity of Heavy Fermions

It is shown on the basis of the Fermi liquid theory that the s-wave scattering potential due to nonmagnetic impurity is strongly enhanced by the mass enhancement factor $1/z$. As a result the impurity potential with moderate strength, of the order of the bandwidth of conduction electrons, gives scattering in the unitarity limit in strongly correlated metals as heavy fermions. This effect is embodied by large pressure dependence of residual resistivities in heavy fermion systems, since the pressure decreases the degree of correlations, which makes the Kondo temperature increase rapidly. This accounts for the large pressure dependence of the residual resistivity observed in heavy fermion metals, such as CeInCu$_{2}$, CeCu$_{6}$, CeAl$_{3}$.