Calendar of Physics Talks Vienna

Two-dimensional semiconducting alternative to graphene: Single-layer MoS2
Speaker:Andras KIS (Ecole Polytechnique Federale de Lausanne, EPFL, Lausanne, Switzerland)
Abstract:After quantum dots, nanotubes and nanowires, two-dimensional materials in the shape of sheets with atomic-scale thickness represent the newest addition to the diverse family of nanoscale materials. The most widely studied two-dimensional material to date is graphene because of its rich physics, high-mobility and wide variety of potential applications. Pristine graphene is however not a semiconductor and the lack of band gap is a serious problem in many applications, for example in electronics. I will present here our work on a material similar to graphene – single layer MoS2, a direct-gap semiconductor. We have exfoliated single layers 6.5 Å thick from bulk crystals of semiconducting MoS2, using the micromechanical cleavage technique commonly used for the production of graphene. Our nanolayers are mechanically and chemically stable under ambient conditions. We have fabricated transistors based on single-layer MoS2 which demonstrate that this material has several advantages over silicon or graphene for potential applications in electronics. Free-standing MoS2 membranes have also been prepared, allowing us to observe ripples arising from thermodynamic fluctuations, previously seen only in graphene. Mechanical measurements on MoS2 membranes show that this new material also has interesting mechanical properties with stiffness higher than stainless steel, mechanical strength at the theoretical limit and 30x higher than steel. References: 1. M.M. Benameur, B. Radisavljevic, J.S. Heron, S. Sahoo, H. Berger, and A. Kis. Visibility of dichalcogenide nanolayers. Nanotechnology 22, 125706, 2011. 2. B. Radisavljevic, A. Radenovic, J. Brivio, V. Giacometti, and A. Kis. Single-layer MoS2 transistors. Nature Nanotechnology 6, 147, 2011. 3. B. Radisavljevic, M.B. Whitwick, and A. Kis. Integrated circuits and logic operations based on single-layer MoS2. ACS Nano 5, 9934, 2011. 4. J. Brivio, D.T.L. Alexander, and A. Kis. Ripples and Layers in Ultrathin MoS2 Membranes. Nano Letters 11, 5148, 2011. 5. S. Bertolazzi, J. Brivio, and A. Kis. Stretching and Breaking of Ultrathin MoS2. ACS Nano 5, 9703, 2011.
Date: Mon, 15.10.2012
Time: 17:30
Location:Universität Wien, Fakultät für Physik, Lise-Meitner-Hörsaal, Strudlhofg. 4, 1090 Wien
Contact:Wiener Physikalisches Kolloquium

Perturbative algebraic quantum field theory and the quantization of submanifold embeddings
Speaker:Dr. Jochen Zahn (Univ. Vienna)
Abstract:Im Rahmen des Vienna Theory Lunch Seminars. Abstract: We review the framework of perturbative algebraic quantum field theory, which provides a mathematically rigorous formulation of perturbative quantum field theories and allows for a generalization to curved spacetimes. We present a recent application of the framework, namely the perturbative quantization of embeddings of d-dimensional submanifolds into n-dimensional Minkowski space, based on the Nambu-Goto action. The model has the status of an effective field theory. We show the absence of anomalies for any dimensions d and n, so in particular, there is no critical dimension n for the case of string theory (d=2).
Date: Tue, 16.10.2012
Time: 12:30
Location:TU Vienna, Wiedner Hauptstr. 8-10, yellow area, 10th floor, seminar room E136
Contact:F. Brünner, S. Frank, P. Köhler, A. G. Passegger, S. Stetina

Integrable Modelle in zweidimensionaler Quantenfeldtheorie
Speaker:Sabina Alazzawi (Univ.Wien)
Abstract:im Rahmen des Seminars für Mathematische Physik
Date: Tue, 16.10.2012
Time: 14:15
Location:Fakultät für Physik, Erwin Schrödinger-Hörsaal, Boltzmanngasse 5, 5. Stock
Contact:J. Yngvason

Interaction of Gas Phase Molecules with Nanostructured Model Supported Catalysts: Thermodynamics and Kinetics
Speaker:Ph Dr. Swetlana Schauermann (Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin/D)
Abstract:Our research activities are focused on atomistic-level understanding of kinetics and thermodynamics of heterogeneously catalyzed reactions and adsorption processes on model supported catalysts. By employing pulsed mutli-molecular beam techniques, IRAS and synchrotron-based spectroscopies, we investigate the mechanistic details and kinetics of complex multi-pathway surface reactions, such as hydrocarbon transformation in presence of hydrogen or selective hydrogenation of multi-unsaturated hydrocarbons, to obtain the correlations between the reactivity and the particular structure of the catalytic surface and it’s chemical state under the reactions conditions. Complementary, we investigated the particles size effects on adsorption energies with single crystal adsorption calorimetry.
Date: Tue, 16.10.2012
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:Univ.Prof. Dr. Ulrike Diebold

Emergent Space and the Example of AdS_5 x S^5
Speaker:Frank Ferrari (Brussels University)
Abstract:After a brief general introduction to the idea of emergent space, I will discuss a precise framework in which it is possible to build explicit models. I will then present the details in the simplest case, corresponding to the famous AdS_5XS^5 background in type IIB string theory, and also sketch some of the many possible generalizations.
Date: Tue, 16.10.2012
Time: 16:15
Duration: 60 min
Location:Erwin Schrödinger Hörsaal Universität Wien Boltzmanngasse 5 5. Stock
Contact:Harold Steinacker

The Remarkable Parallels between Atomic and Hadronic Physics
Speaker:Stanley Brodsky (SLAC National Accelerator Laboratory, Stanford)
Abstract:1. Vorlesung im Rahmen der Schrödinger-Gastprofessur 2012
Date: Thu, 18.10.2012
Time: 14:15
Duration: 90 min
Location:Fakultät für Physik, Erwin Schrödinger-Hörsaal, Boltzmanngasse 5, 5. Stock
Contact:A. Hoang, H. Neufeld

The physics of information: from Maxwell's demon to Landauer
Speaker:Eric LUTZ (Dahlem Center for Complex Quantum Systems, Freie Universität Berlin)
Abstract:We review the intimate connection existing between information theory and thermodynamics. We focus on two complementary aspects: 1) the gain of information with Maxwell's famous demon and 2) the erasure of information with Landauer's principle. We finally discus recent experiments that for the first time demonstrated the equivalence between information and thermodynamics.
Date: Fri, 19.10.2012
Time: 15:30
Location:Hörsaal Atominstitut, Stadionallee 2, 1020 Wien
Contact:J. Schmiedmayer