We study instabilities occurring in the electron system whose Fermi surface has flat regions on its opposite sides. Such a Fermi surface resembles Fermi surfaces of some high-Tc superconductors. In the framework of the parquet approximation, we classify possible instabilities and derive renormalization-group equations that determine the evolution of corresponding susceptibilities with decreasing temperature. Numerical solutions of the parquet equations are found to be in qualitative agreement with a ladder approximation. For the repulsive Hubbard interaction, the antiferromagnetic (spin-density-wave) instability dominates, but when the Fermi surface is not perfectly flat, the d-wave superconducting instability takes over. 74.25.Dw, 75.30.Fv
ac and dc magnetotransport data in the normal state of YBa2Cu3O7 are analyzed within Fermiliquid and non-Fermi-liquid models. In the Fermi-liquid analysis we use the Fermi surface deduced from band-structure calculations and angular-resolved photoemission experiments and assume that the electron relaxation rate varies over the Fermi surface. The non-Fermi-liquid models are the two-dimensional Luttinger liquid model and the charge-conjugation-symmetry model. We find that the existing experimental data can be adequately fit by any of these models. This work provides a framework for the analysis of experiments that may discriminate among these models. 74.25.Gz, 74.25.Fy,
We develop a systematic theory of the Hall effect in Q1D conductors in both weak and strong magnetic fields for a model where the electron relaxation time varies over the Fermi surface. At high temperatures, the Hall coefficient saturates at the value −β/ecn, where the dimensionless coefficient β is determined by the curvature of the longitudinal dispersion law of electrons, e the electron charge, c is the speed of light, and n is the hole concentration. At low temperatures, where a strong variation of the relaxation rate over the Fermi surface develops in the form of "hot spots", the Hall coefficient becomes temperature-dependent and may change sign for a particular choice of the transverse dispersion law parameters. In our model, the sign changes in a weak, but not in a strong magnetic field.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.