Electron–Hole Crossover in Gate-Controlled Bilayer Graphene Quantum Dots

Nano Letters, vol. 20, pp. 7709–7715

Abstract

Abstract Electron and hole Bloch states in bilayer graphene exhibit topological orbital magnetic moments with opposite signs, which allows for tunable valley-polarization in an out-of-plane magnetic field. This property makes electron and hole quantum dots (QDs) in bilayer graphene interesting for valley and spin-valley qubits. Here, we show measurements of the electron–hole crossover in a bilayer graphene QD, demonstrating opposite signs of the magnetic moments associated with the Berry curvature. Using three layers of top gates, we independently control the tunneling barriers while tuning the occupation from the few-hole regime to the few-electron regime, crossing the displacement-field-controlled band gap. The band gap is around 25 meV, while the charging energies of the electron and hole dots are between 3 and 5 meV. The extracted valley g-factor is around 17 and leads to opposite valley polarization for electrons and holes at moderate B-fields. Our measurements agree well with tight-binding calculations for our device.

Authors 13

1. Luca Banszerus corresponding Aachen JARA-FIT and 2nd Institute of Physics

   Forschungszentrum Jülich · RWTH Aachen University

   Affiliation as printed

   Forschungszentrum Jülich , , , , E.U

   RWTH Aachen University , , , , E.U

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

   Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425 Jülich, Germany, E.U

2. Alexander Rothstein Aachen JARA-FIT and 2nd Institute of Physics

   RWTH Aachen University

   Affiliation as printed

   RWTH Aachen University , , , , E.U

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

3. Thomas Z. Fabian

   TU Wien

   Affiliation as printed

   TU Wien , , , , E.U

   Institute for Theoretical Physics, TU Wien, 1040 Vienna, Austria, E.U

4. S. Möller Aachen JARA-FIT and 2nd Institute of Physics

   Forschungszentrum Jülich · RWTH Aachen University

   Affiliation as printed

   Forschungszentrum Jülich , , , , E.U

   RWTH Aachen University , , , , E.U

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

   Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425 Jülich, Germany, E.U

5. Eike Icking Aachen JARA-FIT and 2nd Institute of Physics

   Forschungszentrum Jülich · RWTH Aachen University

   Affiliation as printed

   Forschungszentrum Jülich , , , , E.U

   RWTH Aachen University , , , , E.U

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

   Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425 Jülich, Germany, E.U

6. Stefan Trellenkamp

   Forschungszentrum Jülich

   Affiliation as printed

   Forschungszentrum Jülich , , ,

   Helmholtz Nano Facility, Forschungszentrum Jülich, 52425 Jülich, Germany

7. Florian Lentz

   Forschungszentrum Jülich

   Affiliation as printed

   Forschungszentrum Jülich , , ,

   Helmholtz Nano Facility, Forschungszentrum Jülich, 52425 Jülich, Germany

8. Daniel Neumaier Aachen AMO GmbH

   University of Wuppertal · AMO (Germany)

   Affiliation as printed

   AMO GmbH , , , , E.U

   University of Wuppertal , , , E.U

   AMO GmbH, Gesellschaft für Angewandte Mikro- und Optoelektronik, 52074 Aachen, Germany, E.U

   University of Wuppertal, 42285 Wuppertal, Germany, E.U

9. Kenji Watanabe

   National Institute for Materials Science

   Affiliation as printed

   National Institute for Materials Science , , 1-1 Namiki , ,

   Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan

10. Takashi Taniguchi

    National Institute for Materials Science

    Affiliation as printed

    National Institute for Materials Science , , 1-1 Namiki , ,

    International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan

11. Florian Libisch

    TU Wien

    Affiliation as printed

    TU Wien , , , , E.U

    Institute for Theoretical Physics, TU Wien, 1040 Vienna, Austria, E.U

12. Christian Volk Aachen JARA-FIT and 2nd Institute of Physics

    Forschungszentrum Jülich · RWTH Aachen University

    Affiliation as printed

    Forschungszentrum Jülich , , , , E.U

    RWTH Aachen University , , , , E.U

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

    Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425 Jülich, Germany, E.U

13. Christoph Stampfer Aachen JARA-FIT and 2nd Institute of Physics

    Forschungszentrum Jülich · RWTH Aachen University

    Affiliation as printed

    Forschungszentrum Jülich , , , , E.U

    RWTH Aachen University , , , , E.U

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

    Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425 Jülich, Germany, E.U