Berlin 2012 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 102: Transport: Graphene 2 (jointly with TT, MA, DY, DS, O)

HL 102.5: Talk

Friday, March 30, 2012, 10:30–10:45, BH 334

Dirac boundary condition at the reconstructed zigzag edge of graphene — Jan van Ostaa, Anton Akhmerov, Carlo Beenakker, and •Michael Wimmer — Instituut-Lorentz, Universiteit Leiden, The Netherlands

Edge reconstruction modifies the electronic properties of finite graphene samples. We formulate a low-energy theory of the reconstructed zigzag edge by deriving the modified boundary condition to the Dirac equation. If the unit cell size of the reconstructed edge is not a multiple of three with respect to the zigzag unit cell, valleys remain uncoupled and the edge reconstruction is accounted for by a single angular parameter ϑ. Dispersive edge states exist generically, unless |ϑ| = π/2. We compute ϑ from a microscopic model for the "reczag" reconstruction (conversion of two hexagons into a pentagon-heptagon pair) and show that it can be measured via the local density of states. In a magnetic field there appear three distinct edge modes in the lowest Landau level, two of which are counterpropagating.