- Magnetic field driven ambipolar quantum Hall effect in epitaxial graphene close to the charge neutrality point doi link

Auteur(s): Nachawaty A., Yang M., Desrat W., Nanot S., Jabakhanji B., Kazazis D., Yakimova R., Cresti A., Escoffier W., Jouault B.(Corresp.)

(Article) Publié: Physical Review B, vol. 96 p.075442 (2017)

Ref HAL: hal-01584484_v1
DOI: 10.1103/PhysRevB.96.075442
Exporter : BibTex | endNote

We have investigated the disorder of epitaxial graphene close to the charge neutrality point (CNP) by various methods: (i) at room temperature, by analyzing the dependence of the resistivity on the Hall coefficient; (ii) by fitting the temperature dependence of the Hall coefficient down to liquid helium temperature; (iii) by fitting themagnetoresistances at low temperature. All methods converge to give a disorder amplitude of (20±10) meV. Because of this relatively low disorder, close to the CNP, at low temperature, the sample resistivity does not exhibit the standard value~h/4e^2 but diverges. Moreover, themagnetoresistance curves have a unique ambipolar behavior,which has been systematically observed for all studied samples.This is a signature of both asymmetry in the density of states and in-plane charge transfer. The microscopic origin of this behavior cannot be unambiguously determined. However, we propose a model in which the SiC substrate steps qualitatively explain the ambipolar behavior.