Possible superconductivity in nearly antiferromagnetic itinerant fermion systems

Abstract

Strong spin fluctuations arising in itinerant fermion systems close to a magnetic instability may induce or inhibit superconductivity depending on the nesting wave vector ${\mathrm{q}}_{0}$ for which the instability occurs. If \ensuremath{\Vert}${\mathrm{q}}_{0}$\ensuremath{\Vert} is small but finite, triplet pairing is favored and singlet pairing is suppressed as efficiently as in nearly ferromagnetic systems (${q}_{0}$=0). If \ensuremath{\Vert}${\mathrm{q}}_{0}$\ensuremath{\Vert} is large, there is a repulsive contribution from backward scattering by which triplet as well as singlet pairings are strongly depressed. The cases of ${\mathrm{UPt}}_{3}$, ${\mathrm{CePb}}_{3}$, and some organic compounds are considered.