  Non-magnetic impurities affect the paramagnetic response of superconductors
via the associated spin-orbit interaction which, when the non-magnetic impurity
is close to the unitary limit, must be treated beyond the classical Born
approximation. Here the Zeeman response of two-dimensional s- and d-wave
superconductors is calculated within the self-consistent T-matrix formulation
for both impurity and spin-orbit scatterings. It is shown that at the unitary
limit, for which the spin-orbit scattering is maximum, the spin-up and
spin-down channels becomes decoupled implying full Zeeman splitting of the
quasiparticle excitations. These results could be used to test the unitary
scattering hypothesis in high-Tc superconductors.
