Dresden 2009 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 22: Brownian motion and transport II

DY 22.7: Vortrag

Donnerstag, 26. März 2009, 12:00–12:15, ZEU 118

Suppression of size-quantization steps in disordered graphene nanoribbon — •Florian Libisch, Stefan Rotter, and Joachim Burgdörfer — Inst.f.theoretische Physik, TU Wien, Österreich

We numerically study impurity scattering in graphene nanoribbons as a function of impurity density and ribbon length. For long ribbons (ribbon length up to 3 micrometers) we observe exponential (Anderson) localization of the wave function over eight orders of magnitude. To contrast the role of AB and K-K' scattering, we compare impurities that either break or conserve pseudo-spin. By calculating the scattering wave function on the A and B sublattice, we can directly visualize broken pseudo-spin conservation. Using a Fourier transformation allows us to quantitatively assess, for different impurity types, the amount of AB and K-K' scattering. For perfect ribbons, the conductance features size quantization steps due to the transverse confinement. We find that these steps are strongly suppressed in disordered ribbons for impurities that break the AB-symmetry. In contrast, short-range impurities that conserve pseudo-spin result in K-K' scattering and preserve size quantization steps. Comparison of our results with recent experimental data suggests that broken AB symmetry plays an important role in realistic graphene devices.