Size Effects in the Magnetoresistance of Graphite: Absence of Magnetoresistance in Micrometer size Samples

TL;DR

This study demonstrates that the magnetoresistance in graphite diminishes with decreasing sample size, highlighting the influence of quantum effects and challenging existing experimental and theoretical assumptions.

Contribution

It reveals a size-dependent magnetoresistance effect in graphite, emphasizing the role of quantum effects in small samples previously overlooked.

Findings

Magnetoresistance decreases with sample size in graphite.

Quantum effects are significant in small graphite samples.

Revises understanding of magnetoresistance in confined graphene samples.

Abstract

We present a study of the magnetoresistance of highly oriented pyrolytic graphite (HOPG) as a function of the sample size. Our results show unequivocally that the magnetoresistance reduces with the sample size even for samples of hundreds of micrometers size. This sample size effect is due the large mean free path and Fermi wavelength of carriers in graphite and may explain the observed practically absence of magnetoresistance in micrometer confined small graphene samples where quantum effects should be at hand. These were not taken into account in the literature yet and ask for a revision of experimental and theoretical work on graphite.