Magnetoresistance of disordered graphene: from low to high temperatures

TL;DR

This study investigates the magnetoresistance behavior of highly doped monolayer graphene across a broad temperature range, revealing the interplay of classical thermal effects and electron-electron interactions influencing MR.

Contribution

It provides a comprehensive analysis of MR in doped graphene from low to high temperatures, highlighting the transition between diffusive and ballistic regimes and the coexistence of disorder types.

Findings

Maximum MR occurs at 120-240 K and 2-6 T magnetic field.

Positive classical MR increases with temperature due to thermal averaging.

Negative MR from EEI indicates coexistence of long and short-range disorder.

Abstract

We present the magnetoresistance (MR) of highly doped monolayer graphene layers grown by chemical vapor deposition on 6H-SiC. The magnetotransport studies are performed on a large temperature range, from $T$ = 1.7 K up to room temperature. The MR exhibits a maximum in the temperature range $120-240$ K. The maximum is observed at intermediate magnetic fields ($B=2-6$ T), in between the weak localization and the Shubnikov-de Haas regimes. It results from the competition of two mechanisms. First, the low field magnetoresistance increases continuously with $T$ and has a purely classical origin. This positive MR is induced by thermal averaging and finds its physical origin in the energy dependence of the mobility around the Fermi energy. Second, the high field negative MR originates from the electron-electron interaction (EEI). The transition from the diffusive to the ballistic regime is observed. The amplitude of the EEI correction points towards the coexistence of both long and short range disorder in these samples.