ANISOTROPIC FERMI SURFACES AND KOHN–LUTTINGER SUPERCONDUCTIVITY IN TWO DIMENSIONS

The instabilities induced on a two-dimensional system of correlated electrons by the anisotropies of its Fermi line are analyzed on general grounds. Simple scaling arguments allow to predict the opening of a superconducting gap with a well-defined symmetry prescribed by the geometry of the Fermi line. The same arguments predict a critical dimension of 3/2 for the transition of the two-dimensional system to non-Fermi liquid behavior. The methods are applied to the t–t′ Hubbard model in a wide range of dopings.