Berlin 2015 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 29: Transport: Graphene (TT with CPP/DS/DY/HL/O)
HL 29.4: Vortrag
Dienstag, 17. März 2015, 10:15–10:30, A 053
Ab-initio simulations of local current flows in functionalized graphene flakes and ribbons — •Michael Walz1, Jan Wilhelm2, Alexei Bagrets1, and Ferdinand Evers3 — 1Institute of Nanotechnology, Karlsruhe Institute of Technology, D-76131 Karlsruhe, Germany — 2Institute of Physical Chemistry, University of Zürich, CH-8057 Zürich, Switzerland — 3Institute for Theoretical Physics, University of Regensburg, D-93040 Regensburg, Germany
Using our DFT-based transport framework AITRANSS [1], we calculate the transmission and the local current density in graphene flakes functionalized by adsorbed atoms, such as nitrogen or hydrogen. We find that even a single nitrogen atom can almost completely suppress the conductance of a (gated) graphene armchair nano-ribbon. In this situation local ring currents emerge that result in local (orbital) magnetic moments.
In addition, the current flow shows a highly inhomogeneous structure. In the absence of any scatters, the current flows along parallel streamlines that exhibit a strong lateral modulation [2]. In the presence of scattering centers, such as 20% hydrogen absorbants, we observe a filamentary pattern of streamlines. It exhibits local ring currents (“eddies”) that go along with sizeable local magnetic fields, B(r). [3]
In the future, we plan to study the statistics of local currents of such large flakes and its dependency on the impurity concentration.
[1] A. Arnold, F. Weigend, F. Evers, J. Chem. Phys. 126 (2007)
[2] J. Wilhelm, M. Walz, F. Evers, Phys. Rev. B 89 (2014)
[3] M. Walz, J. Wilhelm, F. Evers, Phys. Rev. Lett. 113 (2014)