FWF - Oberflächen - Exotic Surfaces

Project: Research project

Description

The present application seeks to understand the properties of novel and unusual surfaces, for which few dynamical
measurements exist. The applicant plans to spend a research period of 24 months at the University of Cambridge in
the Surface Physics Group under the supervision of Dr. William Allison. The research group of Dr. William
Allison is the world's only group that operates a helium-3 spin-echo spectrometer which can resolve energy
changes as small as 20 neV. Spin-echo measurements on the semimetal Bi(111) and the topological insulator
PbBi2Te4(111) will provide new benchmark data that will assist in the development of theoretical approaches to
understand the fundamental atom-surface interaction on semimetal and topological insulator surfaces. In particular
the spin-echo technique is the only method that can provide data with sufficient experimental resolution for direct
measurements of the mode-selected electron-phonon interaction. Furthermore, the possible investigation of acoustic
surface plasmons in a spectral region inaccessible to any other technique, is an extremely attractive aspect not yet
explored. Based on the analysis of the spin-echo measurements a theoretical concept for the He-Bi(111) interaction
will be developed which may also be adapted for other semimetals.
In an additional return phase of 12 months at the Institute of Experimental Physics (Graz University of
Technology) the knowledge obtained in the group in Cambridge and the first application of this concept for the
He-Bi(111) system will be further developed. This includes the interpretation of the He-PbBi2Te4(111) data
measured in Cambridge. The data will be used to find an appropriate atom-surface interaction model for
topological insulator surfaces. Finally the influence of adsorbed atomic hydrogen onto the Bi(111) surface with the
heading phrase "the lightest on the heaviest" will be investigated experimentally.
While an understanding of the model semimetal bismuth is of great interest for topological insulators and
spintronics, topological insulators themselves are promising candidates for potential applications ranging from
spintronics to quantum computation. Despite their great importance, especially in the case of topological insulators,
semimetals have never been approached with helium atom scattering due to their intrinsic complexity of being
surface conductors (even superconductors) and strongly corrugated at the same time. The applicant's expertise in
helium scattering on these surface systems combined with the world-leading experimental facilities available in
Cambridge will generate new understanding at a fundamental level to these promising materials. Ongoing
cooperation with the University of Cambridge will provide continuous exchange of knowledge and the realization
of joint experiments.
StatusFinished
Effective start/end date15/11/1314/01/17