Exchange Interaction as a Source of Real Space Pairing in High Temperature Superconductors and Heavy Fermions: a Brief Overview

We characterize the principal difference between the pairing induced by the kinetic exchange interactions for the Fermi-liquid and spin-liquid phases. In the case of hybridized electrons the Kondo-exchange induced pairing is invoked, whereas for a single narrow-band case kinetic exchange is responsible for the spin singlet pairing. The former interaction is applied to heavy-fermion systems, whereas the latter is employed to the high temperature superconductors. The current situation concerning the applicability of our theoretical models is briefly and critically assessed.