Surface diffusion and dynamics on Dirac materials. (Please notice the unusual time!)
DIPC Seminars
- Speaker
-
Dr. Anton Tamtögl, Institute of Experimental Physics, Graz University of Technology, Graz, Austria
- When
-
2017/10/11
18:00 - Place
- Donostia International Physics Center
- Add to calendar
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We have studied the diffusion of water on the surfaces of Dirac materials
(graphene and the topological insulator Bi2Te3) using helium-3 spin-echo
spectroscopy[1]. While water is ubiquitous in everyday life, the simplest
mechanisms controlling its molecular motion at a surface have yet to be
revealed by experiment[2-4]. Our experimental results provide a detailed
insight into the behaviour of H2O molecules on the surfaces of Dirac
materials.
Diffusion occurs by an activated hopping motion where in particular in the
case of graphene a strong signature for cooperative behaviour due to repulsive
forces between the molecules appears. The diffusion of water on Bi2Te3 is
governed by a large atomic-scale friction between the adsorbate and the
substrate.
I will also present some details on the surface dynamics of pristine
topological insulator surfaces. The atom-surface scattering probabilities can
be used to extract the electron-phonon coupling of topological insulator
surfaces[5] and inelastic helium atom scattering measurements are able to
resolve the acoustic surface phonon modes of Bi2Te3. Here the low energy
region of the lattice vibrations is mainly dominated by the Rayleigh mode
which has been claimed to be absent in previous experimental studies.
[1] A. Jardine _et al._ , Prog. Surf. Sci. 84, 323 (2009).
[2] A. Hodgson _et al._ , Surf. Sci. Rep. 64, 381 (2009).
[3] S.-C. Heidorn _et al._ ACS Nano 9, 3572 (2015).
[4] J. Carrasco _et al._ , Nat. Mater. 11, 667 (2012).
[5] A. Tamtögl _et al._ , Phys. Rev. B. 95. 195401 (2017).