Anisotropic renormalization of quasiparticles in cuprate-oxide superconductors

Abstract

The Hubbard model on the simple square lattice in the vicinity of the Mott transition is considered by the 1/ d expansion method, with d being the spatial dimensionality. The superexchange interaction is enhanced by antiferromagnetic spin fluctuations, and its enhanced portion is similar to an interaction due to the so-called spin-fluctuation mechanism. Gutzwiller's heavy electrons are renormalized to be light by the enhanced superexchange interaction, which is responsible for high-temperature superconductivity; the formation of light quasiparticles occurs, in particular, for k s in the vicinity of saddle points in two dimensions. This anisotropic renormalization of quasi-particles can explain not only the anisotropic pseudogap in normal states but also other anomalous normal-state properties such as the large anisotropy of resistivity between the parallel and the perpendicular directions to CuO 2 planes.