Abstract
The origin of the superexchange interaction is reexamined in order to clarify that it works even in metallic phases. The wellknown kinetic exchange process is nothing but the virtual exchange process of high-energy spin excitations between the lower and upper Hubbard bands. The mechanism for Cooper pairing between Gutzwiller's heavy electrons, whose band lies between the lower and upper Hubbard bands, by the superexchange interaction can be regarded as that by high-energy spin fluctuations. Because it can also be regarded as a kind of an excitonic mechanism using high-energy spin excitations, it is plausible that the superexchange interaction causes high-temperature superconductivity of Gutzwiller's heavy-electron liquids.
