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The 15th International Conference on

Vibrations at Surfaces

June 22-26, 2015 ▪ Donostia-San Sebastián, Spain

Donostia Igeldotik

Program

Overview ▪ Monday ▪ Tuesday ▪ Wednesday ▪ Thursday ▪ Friday

Wednesday June 24

09:00-10:40 We1: E-ph coupling in novel 2D materials (I)
10:40-11:20 Coffee break
11:20-13:00 We2: E-ph coupling in novel 2D materials (II)
13:00-15:30 Poster session B
Afternoon off - some suggested activities can be found here
19:30-20:30 Public lecture by Polanyi in Kutxa Sala Andia (city center)

We1: E-ph coupling in novel 2D materials (I)

Chair: P. Saalfrank, Potsdam, Germany

09:00-09:30 M. El-Batanouny, Boston, USA
Measuring, interpreting, and translating electron quasiparticle – phonon interactions on the surfaces of the topological insulators
09:30-10:00 S. O. Valenzuela, Barcelona, Spain
Inelastic electronic transport in single-layer graphene and at the surface of topological insulator Bi2Se3
10:00-10:20 F. O. Schumann, Halle, Germany
Surface phonons of BaTiO3(001) and BaTiO3 ultrathin films on Pt(001) and Au(001)
10:20-10:40 M. Herzog, Berlin, Germany
Coherent phonon dynamics across the phase transition of quasi-1D Ta2NiSe5

Contributed talk

Surface phonons of BaTiO3(001) and BaTiO3 ultrathin films on Pt(001) and Au(001)

F. O. Schumann1, K. Meinel1, A. Trützschler1, and W. Widdra1,2

1Institute of Physics, Martin-Luther-Universität Halle-Wittenberg, Halle, Germany

2Max-Planck-Institut für Mikrostrukturphysik, Halle, Germany

Phonons and their softening are key elements for the understanding of the long-range coupling in ferroelectric and multiferroic materials that causes, e.g., the paraelectric to ferroelectric phase transition. In thin films, these ferroelectric properties are often controlled by strain from the underlying substrate or the heterostructures environment.

Here we study the surface phonons of BaTiO3(001) ultrathin films in comparison to BaTiO3 single-crystals by high-resolution electron energy loss spectroscopy (HREELS). In all cases, the HREELS spectra are dominated by three well-developed phonon peaks at about 220, 460, and 660 cm-1. Calculations of the full loss spectra within a semi-classical approach allow to identify the modes as the three A(TO)-derived surface phonon-polaritons (Fuchs-Kliewer modes). In comparison to the single crystal, the surface phonons for the thin films on Pt(001) and on Au(001) are shifted due to the lattice misfit of +2% and -2% for the two different substrates, respectively. Additionally, the surface phonons show a thickness-dependent red shift due to a dielectric coupling to the metallic substrate. Calculations for the BaTiO3(001) thin films which include the response of the substrate can explain the observed shifts.

Schumann.png

Figure 1: HREELS spectra of a BaTiO3 single-crystal.