CPT

Calendar of Physics Talks Vienna

Two-dimensional electronic spectroscopy: coherence, entanglement and photosynthesis
Speaker:Graham R. Fleming (Department of Chemistry, University of California Berkeley and Physical Biosciences Division, Lawrence Berkeley National Laboratory)
Abstract:Two-dimensional (2D) electronic spectra contain information about the combined spatial, energetic and temporal landscapes of condensed phase systems. Because they are recorded at the amplitude level, they are directly sensitive to the presence of quantum coherence. In addition, differing sequences of polarizations of the four fields involved can suppress or enhance specific features in the spectra. An example is given by a sequence which reveals only peaks that have arisen through coherence transfer as opposed to population transfer. In this talk these ideas will be applied to natural photosynthetic light harvesting systems. These pigment-protein complexes contain chlorophyll molecules at very high spatial density, leading to delocalized excited states. The experiments reveal long-lived quantum electronic coherence and substantial coherence transfer leading to speculations about the physiological consequences of quantum effects, and the potential applications in quantum theory. New theoretical methods are required to address these questions and a formally exact, reduced hierarchy approach will be used to describe the experiments and explore more subtle quantum mechanical questions such as the presence of entanglement in natural systems.
Date: Mon, 19.10.2009
Time: 17:30
Location:Universität Wien, Lise Meitner Hörsaal, Strudlhofg. 4, 1090 Wien
Contact:Prof. J. Schmiedmayer

Two-dimensional electronic spectroscopy: Coherence, entanglement and photosynthesis
Speaker:Prof. Dr. Graham Fleming (Department of Chemistry, University of California, Berkeley)
Date: Mon, 19.10.2009
Time: 17:30
Duration: 60 min
Location:Lise-Meitner-Hörsaal, Strudlhofgasse 4, 1st floor, 1090 Wien
Contact:Markus Arndt

Graphene: two-dimensional massless Dirac Fermions
Speaker:Florian Libisch (TU Wien )
Abstract:Graphene, a honeycomb-lattice of carbon atoms, has attracted considerable attention since its first experimental realization in 2004. In particular, the linear dispersion relation near the Fermi energy connects the dynamics of electrons in graphene to the ultrarelativistic Dirac equation. We discuss the implications and limitations of this analogy: we compare predictions based on the Dirac picture (e.g. Klein tunneling or suppressed backscattering) to a tight-binding simulation of realistic graphene quantum dots. In particular we study the influence of confinement and lattice defects on the electronic structure of graphene-based nanodevices. We find that the Dirac properties of graphene are very sensitive to breaking of the sublattice symmetry, in particular at the edges of the sample. Experimental realizations of Dirac physics in graphene nanoelectronics will thus depends on a smooth edge confinement. Lunch Club Overview
Date: Tue, 20.10.2009
Time: 12:30
Duration: 60 min
Location:TU Vienna, Inst. f. Theoretical Physics, Freihaus, Wiedner Hauptstr. 8-10, 10. OG, SEM136
Contact:Max Attems, David Burke, Marcus Huber

Das klassische Klein-Gordon Feld auf gekrümmten Raumzeiten
Speaker:Jakob Yngvason (Univ. Wien) (Fakultät für Physik)
Abstract:im Rahmen des Seminars für Mathematische Physik
Date: Tue, 20.10.2009
Time: 14:30
Duration: 60 min
Location:Erwin Schrödinger-Hörsaal, Boltzmanngasse 5, 5. Stock
Contact:J. Yngvason

Theory of magnetostrictions in Invar materials
Speaker:Dr. Sergii Khmelevskyi (Technische Universität Wien, Institut für Angewandte Physik)
Abstract:The origin of the large value of the spontaneous volume magnetostriction in Invar materials is investigated using first-principle methods of electronic structure calculations. It is shown a common nature of the Invar effect in various sistems such as Fe-based alloys, including classical Invars Fe-Ni and Fe-Pt, and Rare-Earth intermetallics. The origin of existance of various competing theories of Invar effect is analized with particular emphasis on the Fe-Ni alloys and comparison of them to the Laves Phase (Zr,Nb)Fe2 Invar-type alloys.
Date: Tue, 20.10.2009
Time: 16:00
Location:Technische Universität Wien, Institut für Angewandte Physik, Seminarraum 134A, Turm B (gelbe Leitfarbe), 5. OG, 1040 Wien, Wiedner Hauptstraße 8-10
Contact:Ao.Univ.Prof. Dr. Peter Mohn

Holomorphic properties of form factors
Speaker:Jürg Gasser (Univ. Bern) (Fakultät für Physik)
Abstract:2. Vorlesung im Rahmen der Schrödinger-Gastprofessur 2009
Date: Tue, 20.10.2009
Time: 16:15
Duration: 60 min
Location:Erwin Schrödinger-Hörsaal, Boltzmanngasse 5, 5. Stock, 1090 Wien
Contact:H. Neufeld

Vortrag im Rahmen der Chemisch-Physikalischen Gesellschaft: Mysterious Water
Speaker:Thomas Loerting (Universität Innsbruck)
Abstract:Water shows many anomalous properties, which includes its rich polymorphism and its "amorphous polymorphism". In this talk I will introduce the sixteen crystalline and three amorphous phases of ice. I will discuss how we prepare them in the laboratory, what their molecular structure is, where they can be found in nature and how one amorphous and three crystalline phases were discovered in Innsbruck in the last few years. I will discuss our experiments on the highly disputed question whether or not the amorphous phases are glasses in the sense of vitrified liquids. If they are indeed glasses, which our research suggests, the consequence is that water can be separated into three liquids in the deeply supercooled state (of composition H2O and densities of 0.92, 1.15 and 1.26 g/cm3). In fact, we recently achieved to observe coexistence of two glassy water phases differing by 25% in density, which suggests that indeed a first order liquid-liquid phase transition may be at the origin of the thermodynamic anomalies of water in the supercooled region.
Date: Tue, 20.10.2009
Time: 17:00
Location:Lise-Meitner-Hörsaal (ehem. Großer Hörsaal der Experimentalphysik), Fakultät für Physik, Universität Wien, 1090 Wien, Strudlhofgasse 4/Boltzmanngasse 5, 1. Stock
Contact:Christl Langstadlinger

Plasma oscillations and the generation and detection of THz radiation
Speaker:Prof. Dr. Hartmut Roskos, Johann Wolfgang Goethe-Universität Frankfurt (ADLIS Seminar)
Date: Fri, 23.10.2009
Time: 14:00
Duration: 60 min
Location:Seminarraum CBEG02, Institut f. Photonik, Gußhausstr. 27
Contact:Heike Höller, SFB ADLIS Sekretariat, Tel: 58801 13625