Negative Magnetoresistance in the Nearest-neighbor Hopping Conduction

TL;DR

This paper explains negative magnetoresistance in granular metal-insulator materials by showing how magnetic fields increase hopping probability between clusters due to level crossing, enhancing electronic state overlap.

Contribution

It introduces a size effect mechanism where magnetic fields enhance hopping probability via level crossing, leading to negative magnetoresistance in granular materials.

Findings

Hopping probability increases with magnetic field.

Level crossing in clusters enhances state overlap.

Negative magnetoresistance observed in specific materials.

Abstract

We propose a size effect which leads to the negative magnetoresistance in granular metal-insulator materials in which the hopping between two nearest neighbor clusters is the main transport mechanism. We show that the hopping probability increases with magnetic field. This is originated from the level crossing in a few-electron cluster. Thus, the overlap of electronic states of two neighboring clusters increases, and the negative magnetoresistance is resulted.