The absence of energy gap in graphene at zero magnetic field makes the fabrication of nanostructures difficult using metallic surface gates. In large magnetic fields however, the formation of Landau levels creates gaps in the spectrum, and the conducting edge channels follow the electrostatic potential of the gates. In this regime, quantum point contacts can be realized to control the number of channels transmitted through the device. The graphene flake can also be encapsulated between two boron nitride flakes to boost its electron mobility. In such a heterostructure, the four-fold degeneracy of the Landau levels is lifted, and the fractional quantum Hall effect has been observed.
Recently, we have achieved a precise control of the transmitted current through a quantum point contact in the quantum Hall regime, and more complex and exciting devices are now within reach.
Publications:
- C. Déprez, et al. A tunable Fabry-Pérot quantum Hall interferometer in graphene, Nature Nanotechnology AOP (2021)
- L. Veyrat et al. Helical quantum Hall phase in graphene on SrTiO3 Science 367, 781 (2020)
- L. Veyrat et al. Low Magnetic Field Regime of a Gate-Defined Constriction in High-Mobility Graphene, Nano Letters 19, 635 (2019)
- K. Zimmermann et al. Tunable transmission of quantum Hall edge channels with full degeneracy lifting in split-gated graphene devices, Nature Communications 8:14983 (2017)
- S. Martin, et al. Disorder and screening in decoupled graphene on a metallic substrate, Phys. Rev. B 91, 041406(R) (2015)
- Z. Han, et al. Collapse of superconductivity in a hybrid tin-graphene Josephson junction array, Nature Physics 10, 380 (2014)
- N. Couto, B. Sacépé, A. Morpurgo, Transport through Graphene on SrTiO3, Phys. Rev. Lett. 107, 225501 (2011)
- J. Oostinga, B. Sacépé, M. Craciun and A. Morpurgo, Magnetotransport through graphene nanoribbons, Phys. Rev. B 81, 193408 (2010)
Collaborations: Hermann Sellier (I. Néel), Benjamin Piot (LNCMI-Grenoble), Kenji Watanabe, Takashi Taniguchi (NIMS, Tsukuba), and Vitto Han (Shenyang Univ.)