Regensburg 2025 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 29: Poster II

HL 29.69: Poster

Tuesday, March 18, 2025, 18:00–20:00, P1

Effects of vacancies in a bilayer graphene quantum dot — •Ivan Verstraeten, Robin Smeyers, François Peeters, and Lucian Covaci — University of Antwerp, Antwerp, Belgium

Confining the motion of an electron to the nanoscale in all three dimensions, i.e. a quantum dot (QD), sees the emergence of interesting physics and useful applications, such as single electron control or qubits. Bilayer graphene in particular, is a suitable and promising material for quantum dots owing to the many exotic properties of graphene, as well as the possibility to create and tune electronic confinement simply by applying a (position dependent) perpendicular electric field. In this work, the electronic spectrum of an electrostatically defined QD in a finite bilayer graphene flake is numerically calculated using the tight-binding model, which is compared to existing results in the literature where a low-energy continuum theory was used. The tight-binding approach allows for a straightforward implementation of vacancies in the lattice, of which the effects on the spectrum and its valley character are studied. The results show a generally good agreement between the continuum and tight-binding theory, with some interesting discrepancies. We find that vacancies enhance the inter-valley scattering, as in the magnetic field dependence of the spectrum we observe a widening of the avoided crossings between energy levels of a different valley character. Furthermore, vacancies are found to be able to significantly shift energy levels, alter the shape of the wavefunction density and make a state retain its valley mixed character even in the presence of perpendicular magnetic field

Keywords: Graphene; Theory; Electrostatic quantum dot; Vacancies; Valley quantum number