Negative Hopping Magnetoresistance and Dimensional Crossover in Lightly Doped Cuprate Superconductors

TL;DR

This paper demonstrates that weak ferromagnetism in lightly doped cuprate superconductors causes a magnetic field-induced dimensional crossover, significantly increasing localization length and resulting in negative magnetoresistance, explaining experimental observations.

Contribution

It introduces a mechanism linking weak ferromagnetism to dimensional crossover and negative magnetoresistance in cuprates, providing a quantitative explanation for experimental data.

Findings

Magnetic field induces 2D to 3D crossover in La$_{2-x}$Sr$_x$CuO$_4$

Dimensional crossover increases localization length

Explains negative magnetoresistance in the Néel phase

Abstract

We show that, due to the weak ferromagnetism of La$_{2-x}$Sr$_x$CuO$_4$, an external magnetic field leads to a dimensional crossover 2D $\to$ 3D for the in-plane transport. The crossover results in an increase of the hole's localization length and hence in a dramatic negative magnetoresistance in the variable range hopping regime. This mechanism quantitatively explains puzzling experimental data on the negative magnetoresistance in the N\'eel phase of La$_{2-x}$Sr$_x$CuO$_4$.