Giant negative magnetoresistance in high-mobility 2D electron systems

TL;DR

This paper reports a giant negative magnetoresistance in high-mobility GaAs/AlGaAs 2D electron systems, showing a strong effect at low magnetic fields and temperatures, which cannot be explained by current theories.

Contribution

It presents the observation of an unusually large negative magnetoresistance in high-mobility 2D electron systems, challenging existing theoretical explanations.

Findings

Maximum effect at B ≈ 1 kG

Resistivity drops below zero-field values at low temperatures

Effect is suppressed by temperature and in-plane magnetic fields

Abstract

We report on a giant negative magnetoresistance in very high mobility GaAs/AlGaAs heterostructures and quantum wells. The effect is the strongest at $B \simeq 1$ kG, where the magnetoresistivity develops a minimum emerging at $T \lesssim 2$ K. Unlike the zero-field resistivity which saturates at $T \simeq 2 $ K, the resistivity at this minimum continues to drop at an accelerated rate to much lower temperatures and becomes several times smaller than the zero-field resistivity. Unexpectedly, we also find that the effect is destroyed not only by increasing temperature but also by modest in-plane magnetic fields. The analysis shows that giant negative magnetoresistance cannot be explained by existing theories considering interaction-induced or disorder-induced corrections.