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    Fakultät für Physik und Astronomie

    SFB Extra Seminar

    Vortragstitel: "From Farby-Pérot interferences to Quantum Hall regime in gate-defined Quantum Point-Contact in hBN-encapsulated graphene"
    Datum: 28.02.2018, 16:00 - 18:00
    Kategorie: Kolloquium
    Ort: Hubland Süd, Geb. P1 , SE 1
    Veranstalter: 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) [1]. 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 [2]. 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.
    
    [1] Wang et al., Science 342.6158 (2013): 614-617.
    [2] Zimmermann et al., Nature communications 8 (2017): 14983.

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