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Nanoscience Seminar: Image states and energy dissipation on Bi2Te3 surface
Date : May 23, 2017 13:30 〜 Place : Seminar Room 5 (A615), 6th Floor, ISSP Lecturer : Ms. Dilek Yildiz Affiliation : University of Basel, Switzerland

Topological insulators (TIs), belonging into the family of intercalated compounds, have a bandgap in the bulk that makes the crystal insulator, whereas their surfaces (or edges) are conducting. While protected topological states might offer promising playground to observe exotic physical phenomena like Majorana fermion bounded state [1] or magnetic monopoles [2], the effect of friction on topologically protected surface is yet to be reported.

Here we study energy dissipation onto Bi2Te3 surface by means of pendulum geometry oscillating cantilever of combined AFM/STM [3]. While STM shows well understood image potential states, AFM reports on huge dissipation peaks occur due to charging/discharging of those states by the oscillating tip. Huge dissipation peaks occur few nm above the surface and are localized at relatively large voltages as expected for image states. Moreover the energy dissipation depends on the local defect density.In order to understand the frictional response of Bi2Te3 in TI phase as well as its frictional response when the TI phase is partially or fully suppressed, we probe surfaces with different defect density and under external magnetic field. The results show extremely strong dependence of dissipation on external magnetic field since the peaks are shifted to lower energies as the magnetic field increases.

[1] R. Pawlak, et al., Probing atomic structure and majorana wavefunctions in mono-atomic Fe-chains on superconducting Pb-surface, npj Quantum Info 2, 16035 (2016)
[2] M. Z. Hasan and C. L. Kane, Topological insulators, Rev. Mod. Phys. 82, 3045 (2010).
[3] M. Kisiel, et al., Suppression of electronic friction on Nb films in the superconducting state, Nature Materials 10, 119 (2011).

Lecture Language: English


(Published on: Friday May 19th, 2017)