Vortragstitel:"From Farby-Pérot interferences to Quantum Hall regime in gate-defined Quantum Point-Contact in hBN-encapsulated graphene"
SFB 1170 ToCoTronics
Vortragender:Dr. Louis Veyrat - CNRS, Grenoble, France
Since its discovery a decade ago, graphene has opened the field of 2D materials and been of great importance for fundamental an applied
physics. Recently, a new fabrication method was developed to encapsulate graphene between flakes of hexagonal boron nitride (hBN) . This
so-called van-der-Waals stacking technique allowed to protect graphene from its enviroment, boosting its mobility by several orders of
magnitude, and enabling the observation of ballistic effects on the micron scale, as well as to fully lift the spin and valley degeneracies
in the quantum Hall regime. In this talk I will present the van-der-Waals stacking process we implemented in Grenoble with examples
of state-of-the-art graphene heterostructures. In such devices, using top-gated structures and especially quantum point contacts to influence
and taylor electronic trajectories present a strong interest, for both fundamental studies of intrinsic graphene properties and for
applications . I will present how the transport in top-gated devices evolves when applying a magnetic field, from the ballistic regime,
characterized by Fabry-Pérot interferences below the top-gates, to the quantum Hall regime, where transport is dominated by the constriction.
In this regime, Aharonov-Bohm interferences between edge channels are observed between two quantum point contacts. Moreover, the way the
quantum Hall edge channels behave depends strongly on interactions, and I will further show that this can be evidenced by using a substrate with
high dielectric constant, like STO.
 Wang et al., Science 342.6158 (2013): 614-617.
 Zimmermann et al., Nature communications 8 (2017): 14983.