Comparison of experimental data and theoretical calculations for electrical resistivity and Hall coefficient in quasi-one-dimensional organic conductor (TMTSF)2PF6

The temperature dependences of the Hall coefficient and electrical resistivity recently measured by Moser et al. [Phys. Rev. Lett. 84, 2674 (2000)] in the quasi-one-dimensional organic conductor (TMTSF)2PF6 are quantitatively compared with our previous theoretical calculations [Synth. Met. 103, 2202 (1999); Eur. Phys. J. B 11, 385 (1999)]. We find a good agreement, albeit not with a fully consistent set of parameters for the two quantities, without appealing to the Luttinger liquid concept.Comment: 2 pages with 2 figures for ICSM-2000 proceedings. Uses elsart.cls and synmet.cls, which are provided. V.2: one reference update

Anomalous temperature dependence of resistivity in quasi-one-dimensional conductors in a strong magnetic field

We present a heuristic, semiphenomenological model of the anomalous temperature (T) dependence of resistivity Rxx recently observed experimentally in the quasi-one-dimensional (Q1D) organic conductors of the (TMTSF)2X family in moderately strong magnetic fields. We suggest that a Q1D conductor behaves like an insulator (dRxx/dT<0), when its effective dimensionality is one, and like a metal (dRxx/dT>0), when its effective dimensionality is greater than one. Applying a magnetic field reduces the effective dimensionality of the system and switches the temperature dependence of resistivity between the insulating and metallic laws depending on the magnitude and orientation of the magnetic field. We critically analyze whether various microscopic models suggested in literature can produce such a behavior and find that none of the models is fully satisfactory. In particular, we perform detailed analytical and numerical calculations within the scenario of magnetic-field-induced spin-density-wave precursor effect suggested by Gor'kov and find that the theoretical results do not agree with the experimental observations.Comment: RevTeX, 17 pages, 7 figures. v.2: minor corrections; references are added and updated v.3: minor corrections as in the published versio

Magnetoresistance of YBa2Cu3O7 in the "cold spots" model

We calculate the in-plane magnetoresistance $\Delta\rho_{xx}/\rho_{xx}$ of YBa$_2$Cu$_3$O$_7$ in a magnetic field applied perpendicular to the $CuO_2$ planes for the ``cold spots'' model. In this model, the electron relaxation time $\tau_2\propto1/T^2$ at small regions on the Fermi surface near the Brillouin zone diagonals is much longer than the relaxation time $\tau_1\propto1/T$ at the rest of the Fermi surface ($T$ is temperature). In qualitative agreement with the experiment, we find that Kohler's rule is strongly violated, but the ratio $\Delta\rho_{xx}/\rho_{xx}\tan^2\theta_H$, where $\tan\theta_H$ is the Hall angle, is approximately temperature-independent. We find the ratio is about 5.5, which is of the same order of magnitude as in the experiment.Comment: RevTeX, 4 pages, 6 figures. V.2: 2 references adde

Parquet solution for a flat Fermi surface

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-$T_c$ 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.Comment: REVTeX, 36 pages, 20 ps figures inserted via psfig. Submitted to Phys. Rev.