On Attractive Interaction between f Electrons in Valence Fluctuating Systems

Abstract

The mutual interaction between f electrons by one-phonon exchange is investigated with a simplified model including the characteristic feature of valence fluctuating compounds; the local dilation of lattice couples with the local density of f electrons. When an angle made by f site-ligand (or f site)-f site is smaller than π⁄2, one-phonon exchange results in an attractive interaction between neighboring f electrons. The following cases are typical examples where an attractive interaction can exist; a pair of f electrons at the next nearest neighbor sitesin the bcc lattice and a pair at the nearest neighbor sites in the fcc lattece. The proposed mechanism of attractive interaction is consistent with the observations that CeCu₂Si₂ and UBe₁₃ are superconductors, while CeAl₃ and CeCu₆ are not.