Regensburg 2019 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 14: Graphene

TT 14.8: Hauptvortrag

Montag, 1. April 2019, 17:00–17:30, H22

Gate-defined quantum point contacts and quantum dots in bilayer graphene — •Christoph Stampfer — JARA-FIT and 2nd Institute of Physics, RWTH Aachen University — Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich GmbH

Graphene and bilayer graphene (BLG) are attractive platforms for spin qubits, thanks to their weak spin-orbit and hyperfine interaction, promising long spin-coherence times. This has motivated substantial efforts in studying quantum dot (QD) devices based on graphene and BLG. The problem of edge disorder in etched graphene can be completely circumvented in BLG, thanks to a tunable band-gap in the presence of a perpendicularly applied electric field, a feature that allows introducing electrostatic confinement in BLG. However, until very recently, essentially all devices were limited by leakage currents due to shortcomings in opening a clean and homogeneous band gap. A very recent breakthrough in this field has been the introduction of graphite back-gates. Together with the technology of encapsulating BLG in hexagonal boron nitride (hBN), giving rise to high quality hBN-BLG-hBN heterostructures, the use of a graphite back gate allows for a homogeneous and gate tunable band gap in BLG. We will show that this technological improvement allows for an unprecedented quality of quantized conductance measurements and most importantly, allows realizing complete electrostatic current pinch-off. The latter finally offers the possibility of electrostatically confining carriers in BLG and allows implementing quantum dots with a high level of control and low disorder.