Hannover 2016 – wissenschaftliches Programm
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Q: Fachverband Quantenoptik und Photonik
Q 64: Nano-Optics III
Q 64.6: Vortrag
Freitag, 4. März 2016, 12:15–12:30, f342
Hyperbolic plasmons and Dyakonov waves in the topological insulator Bi2Se3 unravelled by swift electrons — •Nahid Talebi1, Cigdem Özsoy Keskinbora1, Hadj Mohamed Benia1, Christoph T. Koch2, and Peter A. van Aken1 — 1Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart, Germany — 2Institut für Experimentelle Physik Universität Ulm Albert-Einstein-Allee 11, D-89081 Ulm
Materials crystallizing in tetradymite structure are fascinating, since at their bandgap just near to the Fermi level they sustain time-reversal-invariant topological effects. Another characteristic of tetradymites is caused by the huge uniaxial electric anisotropic behaviour of the material. Due to the interplay between the metallic and dielectric response, Bi2Se3 can be a proper case for studying the plasmonic excitations in hyperbolic materials with different bulk dispersion characteristics.
Here, utilizing electron energy-loss spectroscopy, we experimentally investigate plasmonic modes of Bi2Se3 nanostructures. Very interesting observations are the high intensities for the EELS signal almost all energies ranging from 0.8 eV up to 4 eV, while at higher energies the contribution of surface plasmon modes is more evident. Interestingly, even at the energy loss of E=0.8 eV in which the material is totally dielectric, the excitation of an edge mode is apparent, and can be explained by the excitation of Dyakonov waves. We furthermore investigate the surface waves and edge plasmon dispersions, both analytically and numerically, in order to obtain an improved understanding of our experimental observations.