Einladung zum Promotionsvortrag von Herrn Nicolas Ray:
„Phonon-induced electron scattering and electric conductivity in twisted bilayer graphene“
The possibility of stacking various two-dimensional allotropes (e.g. graphene) to create van-der-Waals coupled few-layer systems has been discussed in the literature recently. These multilayers are promising for future technological applications due to their remarkable electronic properties. However, the theoretical treatment of arbitrarily stacked multilayers presents a significant challenge. We describe an effective electronic structure theory, based on a general mapping of the Slater-Koster tight-binding Hamiltonian to an effective continuum Hamiltonian H(r,p), that we show can successfully treat such systems.
Subsequently, we focus on the electronic structure of twisted bilayer graphene. For a large twist angle of the layers we find that the two Dirac cones of each layer are preserved. In contrast, the strong coupling low angle regime possesses a remarkably baroque Fermiology. Finally, we consider the scattering of electrons due to phonons within the Boltzmann transport formalism and calculate the resulting in-plane electric conductivity as a function of rotation angle, doping, and temperature. We find that the conductivity depends sensitively on the twist angle of the layers. At large angles the conductivity is almost independent of doping. In the small angle regime the conductivity is reduced by two orders of magnitude and varies significantly with doping. (Vortrag auf Englisch)
Dem Vortrag schließt sich eine Diskussion von 15 Minuten an. Vortrag und Diskussion sind öffentlich. Diesen Verfahrensteilen folgt ein nicht öffentliches Rigorosum von 45 Minuten.