Scanning gate imaging and tuning of quantum electronic transport in graphene
(2022)
Files
THESIS_Nicolas_Moreau_Impression.pdf
Open Access - Adobe PDF
- 31.55 MB
Details
- Authors
- Supervisors
- Hackens, Benoit
- Abstract
- In graphene, charge carriers behave as massless (Dirac) fermions, yielding unprecedented electrical properties. In this thesis, the electronic transport of Dirac fermions is studied in graphene quantum point contacts thanks to low-temperature scanning gate microscopy (SGM), a technique consisting in recording the sample resistance while changing locally the charge carrier density with a biased metallic tip. The focus has been put on backscattering mechanisms and three main directions are explored. First, real space signatures of Klein tunneling, preventing the backscattering of Dirac fermions, are investigated by creating a movable pn junction with the SGM movable top gate. The experimental results are discussed in the light of simulations, revealing that the SGM conductance maps yield an image of the current density around and through the lens, with a direct evidence of Klein tunneling. Second, SGM characterizations are reported under a large magnetic field, in the quantum Hall regime where charge carriers flow in topologically protected quantum Hall edge channels (QHECs). The recorded SGM signatures indicate that counterpropagating QHECs, separated by a few hundreds of nanometers, exist along the same edges in graphene and that charge carriers backscattering is achieved by coupling these QHECs through the localized states of antidots located between them. Third, these antidots are shown to act as nano-sized Fabry-Perot interferometers. A simple model is used to reproduce the experimental results, showing that the signatures associated to two distinct regimes, namely the Aharonov-Bohm and Coulomb dominated regimes, can be explained in a single framework ignoring the Coulomb interactions.
- Affiliations
Citations
Moreau, N. (2022). Scanning gate imaging and tuning of quantum electronic transport in graphene. https://hdl.handle.net/2078.5/104401