Public Physic Colloquium in the Summer Terms 2012 in Münster
Place:     Germany, 48149 Münster, Wilhelm-Klemm-Str. 10, IG I, HS 2
Time:     Thursday, 03.05.2012  16:00 h c.t.
Colloquium Coffee at 15:45 h  at the Lecture Hall

Glimpsing Behind the Mirror: How much can Surface Science tell us about the bulk?
Prof. Dr. Erminald Bertel, Universität Innsbruck, Institut für Physikalische Chemie

The physics of correlated systems opens a multitude of pathways towards constructing materials with unconventional properties, such as high-Tc superconductivity or multiferroic behavior. Quite often these materials are inhomogeneous for generic reasons. To avoid averaging over nanoscale inhomogeneities locally resolving probes such as scanning tunneling microscopy and spectroscopy (STM, STS) are desirable. In general, however, imaging probes are surface sensitive and may be grossly misleading with respect to the physics in the bulk. Here, an approach is demonstrated, which uses the study of surface phase transitions to unravel underlying bulk properties. Halogen phases on Pt(110) are used as a comparatively simple model system. STM and low-energy electron diffraction (LEED) reveal highly unusual phase transitions. Surprisingly, the same type of phase transitions appears on Fe-based superconductors. The observations are rationalized by an extended Landau theory of phase transitions. The model indicates the presence of charge density fluctuations in the substrate in addition to the spin density fluctuations which are presently believed to be responsible for the Cooper pair bonding.

Invited from: Prof. Dr. M. Donath

By Order of the Professors of the Department of Physics

Prof. Dr. Sergej Demokritov