Optimizing Dirac fermions quasi-confinement by potential smoothness engineering

2D Materials, vol. 7, pp. 025037

Abstract

Abstract With the advent of high mobility encapsulated graphene devices, new electronic components ruled by Dirac fermions optics have been envisioned and realized. The main building blocks of electron-optics devices are gate-defined p–n junctions, which guide, transmit and refract graphene charge carriers, just like prisms and lenses in optics. The reflection and transmission are governed by the p–n junction smoothness, a parameter difficult to tune in conventional devices. Here we create p–n junctions in graphene, using the polarized tip of a scanning gate microscope, yielding Fabry–Pérot interference fringes in the device resistance. We control the p–n junctions smoothness using the tip-to-graphene distance, and show increased interference contrast using smoother potential barriers. Extensive tight-binding simulations reveal that smooth potential barriers induce a pronounced quasi-confinement of Dirac fermions below the tip, yielding enhanced interference contrast. On the opposite, sharp barriers are excellent Dirac fermions transmitters and lead to poorly contrasted interferences. Our work emphasizes the importance of junction smoothness for relativistic electron optics devices engineering.

Authors 9

1. Boris Brun

   UCLouvain

   Affiliation as printed

   IMCN, Université Catholique de Louvain (UCLouvain), Chemin du Cyclotron,2, Louvain-la-Neuve, 1348, BELGIUM

2. Nicolas Moreau

   UCLouvain

   Affiliation as printed

   IMCN/NAPS & MODL, Université catholique de Louvain (UCLouvain), B-1348 Louvain-la-Neuve (Belgium)

3. Sowmya Somanchi Aachen JARA-FIT and 2nd Institute of Physics

   Jülich Aachen Research Alliance · RWTH Aachen University

   Affiliation as printed

   JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52056 Aachen, Germany

4. Việt Hùng Nguyễn

   UCLouvain

   Affiliation as printed

   Institute of Condensed Matter and Nanosciences, Université catholique de Louvain, Chemin des étoiles 8, Louvain-la-Neuve, B-1348, BELGIUM

5. Alina Mreńca-Kolasińska

   AGH University of Krakow

   Affiliation as printed

   AGH University of Science and Technology, Faculty of Physics and Applied Computer Science, al. Mickiewicza 30,30-059 Kraków, Poland

6. Kenji Watanabe

   National Institute for Materials Science

   Affiliation as printed

   National Institute for Materials Science, Namiki, Tsukuba, Japan

7. Takashi Taniguchi

   National Institute for Materials Science

   Affiliation as printed

   National Institute for Materials Science, Namiki, Tsukuba, Japan

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

   Jülich Aachen Research Alliance · RWTH Aachen University

   Affiliation as printed

   JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52056 Aachen, Germany

9. Benoit Hackens

   UCLouvain

   Affiliation as printed

   IMCN/NAPS & MODL, Université catholique de Louvain (UCLouvain), B-1348 Louvain-la-Neuve (Belgium)