Superconductivity in Kondo Lattices

Abstract

The Fermi liquid theory of Anderson lattices is developed to describe coherent states of Kondo lattices at low temperatures. The origin of heavy electrons is the spin fluctuation nearly confined within each single f site; the situation is similar to that in dilute Kondo alloys. On the basis of the Fermi liquid theory, one can conclude that an attractive interaction between adjacent f electrons is indispensable to realize heavy-electron superconductivity. Consequently the attractive interaction should be of finite range, so that even s-symmetry Cooper pairs can be anisotropic; the energy gap, for example, can vanish along lines on the Fermi surface. It is also discussed that phonon-mediated attractive interaction between adjacent f electrons depends on the lattice structure. For example, it is expected in CsCℓ type lattices, while it should be absent in NaCℓ type lattices. Typical heavy-electron superconductors such as CeCu₂Si₂ and UBe₁₃ can be actually regarded as a kind of CsCℓ type.