Magnetoresistance of YBa2Cu3O7 in the "cold spots" model

TL;DR

This paper models the in-plane magnetoresistance of YBa2Cu3O7 using a 'cold spots' approach, explaining experimental violations of Kohler's rule and the temperature independence of a specific resistance ratio.

Contribution

It introduces a 'cold spots' model with differing electron relaxation times on the Fermi surface to explain magnetoresistance behavior in YBa2Cu3O7.

Findings

Kohler's rule is strongly violated in the model.

The ratio Δρxx/ρxx tan^2θH is approximately temperature-independent.

The ratio is about 5.5, matching experimental observations.

Abstract

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.