Berlin 2015 – wissenschaftliches Programm
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DY: Fachverband Dynamik und Statistische Physik
DY 19: Transport: Graphene (joint session TT/ CPP/ DS/ DY/ HL/ MA/ O)
DY 19.10: Vortrag
Dienstag, 17. März 2015, 12:00–12:15, A 053
Merging of the Dirac points in electronic artificial graphene — •Juraj Feilhauer1,2, Walter Apel1, and Ludwig Schweitzer1 — 1Physikalisch-Technische Bundesanstalt (PTB), Braunschweig, Germany — 2Institute of Electrical Engineering, Slovak Academy of Sciences, Bratislava, Slovakia
Artificial graphene (AG) is a man-made electron system which has a similar bandstructure as normal graphene, i.e. in the low-energy part of the electronic spectrum, two bands touch and form a pair of Dirac cones. We study analytically and numerically the bandstructure of electronic AG under uniaxial strain. Here, AG is created from the two-dimensional electron gas by applying a repulsive triangular potential and the effect of strain is modeled by tuning the distance between the repulsive potentials along the armchair direction. In normal graphene, the theory based on nearest-neighbour tight-binding approximation predicts that due to the change of the hopping integrals by applying uniaxial strain, both Dirac cones are shifted away from the corners of the Brillouin zone and also becomes elliptical instead of circular. With increasing compressive strain, the Dirac cones move along the edge of Brillouin zone towards each other until they merge. We show that such a merging of the Dirac cones also exists in uniaxially compressed AG. With applied strain, we find the Dirac cones are also tilted and that can be simulated by the presence of a next-nearest-neighbour hopping in the tight-binding hamiltonian. We discuss a possible realization of our theoretical results in a recent experiment with molecular graphene.