Negative c-axis magnetoresistance in graphite

TL;DR

This study investigates the negative c-axis magnetoresistance in graphite, revealing tunneling between Landau levels of Dirac fermions, which advances understanding of interlayer electronic transport in layered materials.

Contribution

It provides experimental evidence of negative ILMR in graphite linked to Landau level tunneling of Dirac fermions, connecting to similar phenomena in multilayer Dirac systems.

Findings

Negative magnetoresistance observed above a certain field B_m(T)

B_m reaches 5.4 T at 150 K

ILMR related to tunneling between Landau levels of Dirac fermions

Abstract

We have studied the c-axis interlayer magnetoresistance (ILMR), R_c(B) in graphite. The measurements have been performed on strongly anisotropic highly oriented pyrolytic graphite (HOPG) samples in magnetic field up to B = 9 T applied both parallel and perpendicular to the sample c-axis in the temperature interval 2 K < T < 300 K. We have observed negative magnetoresistance, dR_c/dB < 0, for B || c-axis above a certain field B_m(T) that reaches its minimum value B_m = 5.4 T at T = 150 K. The results can be consistently understood assuming that ILMR is related to a tunneling between zero-energy Landau levels of quasi-two-dimensional Dirac fermions, in a close analogy with the behavior reported for alpha-(BEDT-TTF)2I3 [N. Tajima et al., Phys. Rev. Lett. 102, 176403 (2009)], another multilayer Dirac electron system.