Probing proximity-induced superconductivity in bilayer graphene using gate-defined quantum dots

arXiv (Cornell University)

Abstract

Van der Waals heterostructures offer a direct way of combining two-dimensional (2D) materials with different electronic properties, such as 2D semiconductors, metals, and superconductors, in a single device. Bilayer graphene (BLG) is particularly attractive in this context, as its electrically tunable band gap enables local control of tunnel barriers and quantum dots. Here, we realize an all-2D hybrid platform based on BLG proximitized by superconducting NbSe$_2$. Using local electrostatic gates, we define tunnel barriers and quantum dots at different distances from the lateral superconductor-semiconductor interface. The quantum dots serve as local spectroscopic probes of the proximitized BLG channel segment, forming tunable superconductor-quantum dot-normal conductor junction devices. Coulomb blockade and finite-bias spectroscopy reveal a proximity-induced superconducting gap of up to $80\,\mathrm{μeV}$ and allow to track its evolution with increasing distance from the NbSe$_2$ contact. We find that the local density of states remains suppressed over distances exceeding 1 $μ$m, consistent with superconducting proximity through a highly ballistic BLG channel. Our results show that BLG-superconductor hybrids offer a controllable platform where quantum dots and quantum point contacts can be well combined with superconductivity.

Authors 11

1. Philipp Schmidt Aachen JARA-FIT and 2nd Institute of Physics

   Forschungszentrum Jülich · RWTH Aachen University

   Affiliation as printed

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

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

2. Mathies Funke Aachen JARA-FIT and 2nd Institute of Physics

   RWTH Aachen University

   Affiliation as printed

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

3. Till Tenger Aachen JARA-FIT and 2nd Institute of Physics

   RWTH Aachen University

   Affiliation as printed

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

4. Katarina Stanojević Aachen JARA-FIT and 2nd Institute of Physics

   RWTH Aachen University

   Affiliation as printed

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

5. H. Dulisch Aachen JARA-FIT and 2nd Institute of Physics

   Forschungszentrum Jülich · RWTH Aachen University

   Affiliation as printed

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

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

6. Kenji Watanabe

   National Institute for Materials Science

   Affiliation as printed

   Research Center for Electronic and Optical Materials , National Institute for Materials Science , 1-1 Namiki , Tsukuba 305-0044 , Japan

7. Takashi Taniguchi

   National Institute for Materials Science

   Affiliation as printed

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

8. Fabian Hassler Aachen Institute for Quantum Information

   RWTH Aachen University

   Affiliation as printed

   Institute for Quantum Information , RWTH Aachen University , 52056 Aachen , Germany

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

   Forschungszentrum Jülich · RWTH Aachen University

   Affiliation as printed

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

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

10. Szabolcs Csonka

    Budapest University of Technology and Economics

    Affiliation as printed

    Department of Physics , Institute of Physics , Budapest University of Technology and Economics , Müegyetem rkp. 3. , H-1111 Budapest , Hungary

    MTA-BME Superconducting Nanoelectronics Momentum Research Group , Müegyetem rkp. 3. , H-1111 Budapest , Hungary

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

    Forschungszentrum Jülich · RWTH Aachen University

    Affiliation as printed

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

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