Negative hopping magnetoresistance of two-dimensional electron gas in a smooth random potential

TL;DR

This paper demonstrates that applying a magnetic field enhances tunnel coupling between localized states in a 2D electron gas with a smooth random potential, leading to negative magnetoresistance at low temperatures.

Contribution

It introduces a model showing how magnetic fields increase tunnel coupling via gauge factor differences, explaining negative magnetoresistance in such systems.

Findings

Magnetic field increases tunnel coupling between localized states.

Enhanced coupling causes negative magnetoresistance at low temperatures.

Characteristic magnetic field depends on the lakes' area in the potential landscape.

Abstract

We show that the tunnel coupling between semiclassical states localized in different minima of a smooth random potential increases when magnetic field is applied. This increase originates from the difference in gauge factors which electron wave functions belonging to different electron ``lakes'' acquire in the presence of the field. We illustrate the increase of coupling by a model calculation of tunneling through a saddle point separating two adjacent lakes. In the common case, when the barrier between two lakes is much narrower than their size, the characteristic magnetic field is determined by the area of the lakes, and thus may be quite small. The effect of the field on coupling constants leads to a negative magnetoresistance in low-temperature conduction.