On the low-field Hall coefficient of graphite

TL;DR

This study investigates the temperature and magnetic field dependence of the Hall coefficient in multigraphene samples, revealing that embedded interfaces influence the Hall effect and are linked to superconducting behavior, rather than intrinsic properties of graphite.

Contribution

It demonstrates that the negative low-field Hall coefficient in graphite is due to embedded interfaces, not intrinsic to ideal graphite, highlighting the role of interfaces in electronic transport.

Findings

Hall coefficient is positive at low T and B, turns negative at higher T and B.

Embedded interfaces contribute to superconducting-like behavior.

Negative Hall coefficient is not intrinsic to pure graphite.

Abstract

We have measured the temperature and magnetic field dependence of the Hall coefficient ($R_{\rm H}$) in three, several micrometer long multigraphene samples of thickness between $\sim 9~$to $\sim 30$~nm in the temperature range 0.1 to 200~K and up to 0.2~T field. The temperature dependence of the longitudinal resistance of two of the samples indicates the contribution from embedded interfaces running parallel to the graphene layers. At low enough temperatures and fields $R_{\rm H}$ is positive in all samples, showing a crossover to negative values at high enough fields and/or temperatures in samples with interfaces contribution. The overall results are compatible with the reported superconducting behavior of embedded interfaces in the graphite structure and indicate that the negative low magnetic field Hall coefficient is not intrinsic of the ideal graphite structure.