Possible high-T c superconductivity mediated by antiferromagnetic spin fluctuations in systems with Fermi surface pockets

Abstract

We propose that if there are two small pocketlike Fermi surfaces, and the spin susceptibility is pronounced around a wave vector $\mathbf{Q}$ that bridges the two pockets, the spin-singlet superconductivity mediated by spin fluctuations may have a high transition temperature. Using the fluctuation exchange approximation, this idea is confirmed for the Hubbard on a lattice with alternating hopping integrals, for which ${T}_{c}$ is estimated to be almost an order of magnitude larger than those for systems with a large connected Fermi surface.