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F. Libisch, L. Walzek, L. Linhart, L. Chizhova, J. Burgdörfer:
"Electron optics in graphene nanostructures";
Poster: International Winter School of Properties of Novel Materials 2016, Kirchberg in Tirol; 13.02.2016 - 20.02.2016.

We simulate electron transport through large-scale graphene nanostructures featuring
spatially varying potentials, such as p-n junctions patterned by electrostatic gates.
While for a sharp interface the p-n junction acts as a focusing lens for an incident
divergent electron beam (Veselago lens), for a smooth transition region the p-n junc-
tion acts as a shaper of a narrow beam with near-zero divergence, providing the basis
for electron-optics in graphene nanostructures. We quantitatively show that these
95Tuesday, February 16th
Poster session
effects are robust in presence of interface roughness and disorder, and provide upper
bounds for their experimental realizations.
Eigenstates of the Wigner-Eisenbud-Smith time delay operator yield a measure for
the electron dwell time inside the structure, and associated particle-like eigenstates
corresponding to classical paths through the sample. Comparing linear (graphene-
like) and parabolic dispersion relations yields valuable insights into the properties
of bandstructure and resonances. We propose a protocol to extract information
on classical paths from conductance measurements, using transport through a wide
graphene ribbon gated by an STM tip.

Graphene, Quantum dots, Valleytronics