Energy dissipation on Dirac and semimetal surfaces: Understanding surface dynamics on the nano-scale
Anton Tamtögl
Institut für Experimentalphysik; TU Graz
16:00 - 16:40 Tuesday 17 December 2019 TUG P2 We have been studying various promising material surfaces, so-called Dirac materials, experimentally and theoretically. Among these, three-dimensional topological insulators such as Bi2Te3 exhibit an insulating gap in the bulk while the surface is electrically conducting[1]. However, in real samples and at finite temperatures, their ideal zero-Kelvin behaviour is perturbed and scattering processes via electron-phonon (e-ph) coupling can give rise to energy losses. In this context atom-surface scattering has been demonstrated to be a sensitive probe to determine the surface phonon dispersion and the e-ph interaction parameter and I will show examples of the phonon dispersion and the e-ph coupling on these materials[1-3].
In the second part I will illustrate how the lineshape broadening upon inelastic scattering from surfaces can be used to determine the characteristics of energy dissipation upon the motion of atoms and molecules[4,5]. The motion of an adsorbed molecule arises from the rate of energy transfer between the molecule and the surface, which is acting as a heat bath. Due to the low energy of the probing particle beam, we are able to study the motion of delicate adsorbates such as water[6].
In general, the study of these surface dynamical processes is a unique and challenging problem for experiments, as it requires both sub-nanometre spatial resolution and fast (picosecond to nanosecond) temporal resolution. I will show that by combining reciprocal space with real space techniques, surface dynamical processes can be measured over more than 14 orders of magnitude, thus providing experimental data for the rate description of dynamics. The latter is crucial for an understanding of the underlying principles of chemical reactions where the rate prediction upon accurate computational calculations often suffers from the lack of experimental data.
[1] A. Tamtögl et al., Phys. Rev. B. 95, 195401 (2017).
[2] A. Tamtögl et al., Nanoscale, 10, 14627 (2018).
[3] A. Tamtögl et al., npj Quantum Mater. 4, 28 (2019).
[4] I. Calvo-Almazán et al., J. Phys. Chem. Lett. 7, 5285 (2016).
[5] A. Tamtögl et al. Carbon 126, 23 (2018).
[6] A. Tamtögl et al., Nat. commun., accepted, (2019).
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