(2021) Christoph Stampfer: Bilayer graphene – a tunable 2D semiconductor for quantum electronics

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. Christoph Stampfer is Professor of Experimental Solid State Physics at the RWTH Aachen University and researcher at the Forschungszentrum Jülich. His primary interests include graphene and 2D materials research, quantum transport, and micro electromechanical systems. He holds a Dipl.-Ing. Degree in Technical Physics from the TU Vienna (Austria) and a Ph.D. in Mechanical Engineering from the ETH Zurich (Switzerland). He was a staff member at the Institute for Micro and Nano Systems of the ETH Zurich from 2003 to 2007 and staff member of the Solid State Laboratory (Ensslin-Group at ETH Zurich) from 2007 to 2009. From 2009 till 2013 he was JARA-FIT Junior Professor at the RWTH Aachen and the Forschungszentrum Jülich. He has been awarded with an ERC Starting Grant to work on "Graphene Quantum Electromechanical Systems" in 2011, was a member of the Young Scientist community of the World Economic Forum and received in 2018 an ERC Consolidator Grant to work on “2D Materials for Quantum Technologies”. YouTube Video