Large Positive Magnetoresistance of the Lightly Doped La_{2}CuO_{4} Mott Insulator

TL;DR

This study investigates the positive magnetoresistance in lightly doped La_2CuO_4, revealing glassy charge dynamics and Coulomb interactions at low temperatures, with implications for understanding disordered insulators.

Contribution

It reports the observation of positive magnetoresistance and glassy charge behavior in lightly doped La_2CuO_4, highlighting Coulomb interactions as a key factor.

Findings

Positive MR emerges below spin glass transition temperature.

MR shows hysteresis and memory effects.

Scaling behavior suggests Coulomb repulsion influences charge dynamics.

Abstract

The in-plane and out-of-plane magnetoresistance (MR) of single crystals of La_2CuO_4, lightly doped (x=0.03) with either Sr (La_{2-x}Sr_xCuO_4) or Li (La_2Cu_{1-x}Li_xO_4), have been measured in the fields applied parallel and perpendicular to the CuO_2 planes. Both La_{1.97}Sr_{0.03}CuO_4 and La_2Cu_{0.97}Li_{0.03}O_4 exhibit the emergence of a positive MR at temperatures (T) well below the spin glass (SG) transition temperature T_{sg}, where charge dynamics is also glassy. This positive MR grows as T->0 and shows hysteresis and memory. In this regime, the in-plane resistance R_{ab}(T,B) is described by a scaling function, suggesting that short-range Coulomb repulsion between two holes in the same disorder-localized state plays a key role at low T. The results highlight similarities between this magnetic material and a broad class of well-studied, nonmagnetic disordered insulators.