Christoph Stampfer: Bilayer graphene – a tunable 2D semiconductor for quantum electronics

CARBONHAGEN 2021 (www.carbonhagen.com)

Christoph Stampfer (2021 - March 22 - 16:00 CET, GMT+1)

JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074 Aachen, Germany

Graphene and bilayer graphene (BLG) are attractive platforms for quantum circuits. This has motivated substantial efforts in studying quantum dot (QD) devices based on graphene and BLG. The major challenge in this context is the missing band-gap in graphene, which does not allow to confine electrons by means of electrostatics. A widely used approach to tackle this problem was to introduce a hard-wall confinement by etching the graphene sheet. However, the influence of edge disorder, turned out to be a roadblock for obtaining clean quantum devices. The problem of edge disorder can be circumvented in clean BLG, thanks to the fact that this material offers a tunable band-gap (up to 150 meV) in the presence of a perpendicularly applied electric field, a feature that allows introducing electrostatic soft confinement in BLG.Here we present gate-controlled single, double, and triple dot operation in electrostatically gapped BLG. We show a remarkable degree of control of our devices, which allows the implementation of gate-defined electron-hole and electron-electron double-dot systems, where single-electron occupation becomes possible. Also in the single dot regime, we reach the very few electron/hole regime, extract excited state energies and investigate their evolution in a parallel and perpendicular magnetic field. Finally, we will show data on ultra-clean BLG quantum dots allowing investigating the spin-valley coupling in bilayer graphene.