Calendar of Physics Talks Vienna

Searching for top-quark pair resonances in the all-hadronic final state with ATLAS
Speaker:Dr. Gregor Kasieczka (Uni Heidelberg)
Abstract:A search for heavy resonances that decay into top-quark pairs producing two massive jets with high transverse momentum is presented. Data collected with the ATLAS detector during the proton–proton collision run at a centre-of-mass energy of 7 TeV in 2011 is analysed. The substructure-based HEPTopTagger algorithm is used to separate top-quark jets from those arising from light quarks and gluons. Top-quark candidates are also required to have evidence of an associated bottom-quark decay. The contributions from Standard Model background processes, such as top-quark pair production and multijet production, are estimated using data-driven techniques. No significant ... For more information visit here
Date: Mon, 07.10.2013
Time: 17:00
Duration: 60 min
Location:Institute for High Energy Physics ( Library, 1st Floor ) Nikolsdorfer Gasse 18, 1050, Wien
Contact:Ken Suzuki

HgTe as a topological insulator
Speaker:Laurens W. MOLENKAMP (Universität Würzburg)
Abstract:HgTe is a zincblende-type semiconductor with an inverted band structure. While the bulk material is a semimetal, lowering the crystalline symmetry opens up a gap, turning the compound into a topological insulator. The most straightforward way to do so is by growing a quantum well with (Hg,Cd)Te barriers. Such structures exhibit the quantum spin Hall effect, where a pair of spin polarized helical edge channels develops when the bulk of the material is insulating. Our transport data [1-3] provide very direct evidence for the existence of this third quantum Hall effect, which now is seen as the prime manifestation of a 2-dimensional topological insulator. To turn the material into a 3-dimensional topological insulator, we utilize growth induced strain in relatively thick (ca. 100 nm) HgTe epitaxial layers. The high electronic quality of such layers allows a direct observation of the quantum Hall effect of the 2-dimensional topological surface states [4]. Moreover, on contacting these structures with Nb electrodes, a supercurrent is induced in the surface states. References [1] M. König, et al., Science, 318, 766 (2007). [2] A. Roth, et al., Science, 325, 294 (2009). [3] C. Brüne, et al., Nature Physics, 8, 486 (2012). [4] C. Brüne, et al., Phys. Rev. Lett., 106, 126803 (2011).
Date: Mon, 07.10.2013
Time: 17:30
Location:TU Wien Freihaus Hörsaal 5, Wiedner Hauptstr. 8, 1040 Wien
Contact:K. Unterrainer

Defect States at c-Si/a-Si3NxHy Interfaces
Speaker:Leif Eric Hintzsche (University of Vienna)
Abstract:Amorphous silicon nitrides are deposited on crystalline silicon as antireflection and passivating coatings. Up to date detailed knowledge about the interfaces is largely lacking. We have investigated the electronic and structural properties of c-Si/a-Si3NxHy interfaces obtained by large scale ab initio molecular dynamics simulations. Over 500 independent samples have been generated for each considered stoichiometry to perform a reliable defect analysis. While the classes of dominant defect states coincided with previous bulk calculations, we found a considerably increased defect density at the interface. By applying an energy and spatially resolved defect analysis, we observed that most of the defect states originate from the first silicon nitride layer at the interface.
Date: Tue, 08.10.2013
Time: 12:30
Duration: 60 min
Location:Univ. of Vienna, Faculty of Physics, Boltzmanngasse 5, 5th floor, Erwin Schrödinger Lecture Hall
Contact:Albert Georg Passegger, Peter Poier - www.univie.ac.at/lunch-seminar

The excitation spectrum of rotating Nambu-Goto strings
Speaker:Jochen Zahn (Univ. Wien)
Abstract:im Rahmen des Seminars für Mathematische Physik
Date: Tue, 08.10.2013
Time: 14:15
Duration: 60 min
Location:Fakultät für Physik, Erwin-Schrödinger-Hörsaal, Boltzmanngasse 5, 5. Stock
Contact:J. Yngvason

Atomic-scale observation of multi-conformational binding and energy level alignment of ruthenium-based photosensitizers on TiO2 anatase
Speaker:Christopher Kley (Max-Planck-Institute for Solid State Research, Stuttgart/D)
Abstract: Dye-sensitized solar cells (DSSCs) constitute a promising approach to sustainable and low-cost solar energy conversion. Their overall efficiency crucially depends on the effective coupling of the photosensitizers to the photoelectrode and the details of the dye’s energy levels at the interface. Despite great efforts, the specific binding of prototypical ruthenium-based dyes to TiO2, their potential supramolecular interaction, and the interrelation between adsorption geometry and electron injection efficiency lack experimental evidence. In this talk, I will present our latest results on the observation of multi-conformational adsorption and energy level alignment of single N3 dyes (cisbis(isothiocyanato)bis(2,2’-bipyridyl-4,4’-dicarboxylato)-ruthenium(II)) on TiO2 anatase (101). In situ electrospray ionization deposition combined with scanning tunnelling microscopy and spectroscopy studi
Date: Tue, 08.10.2013
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

Marginally outer trapped surfaces in 5 dimensions
Speaker:Walter Simon (Univ. Wien)
Abstract:im Rahmen des Literaturseminars über Gravitationsphysik
Date: Thu, 10.10.2013
Time: 14:15
Duration: 60 min
Location:Seminarraum Physik, Sensengasse 8 (Erdgeschoß)
Contact:H. Rumpf

Residual Symmetries in the Lepton Mass Matrices
Speaker:Walter Grimus (Univ. Wien)
Abstract:im Rahmen des Teilchenphysikseminars
Date: Thu, 10.10.2013
Time: 14:15
Duration: 60 min
Location:Fakultät für Physik, Erwin Schrödinger-Hörsaal, Boltzmanngasse 5, 5. Stock
Contact:H. Neufeld

Exploring Extensions to the Standard Model of Particle Physics with Semileptonic and Leptonic B Meson Decays
Speaker:Christoph Schwanda (HEPHY)
Date: Fri, 11.10.2013
Time: 13:30
Location:TU Wien, Freihaus, Wiedner Hauptstr., HS 2 (2nd floor=
Contact:Anton Rebhan

Analog Hawking radiation from acoustic black holes in superfluids of atoms and of light
Speaker:Iacopo CARUSOTTO (INO-CNR BEC Center, Trento, Italy)
Abstract:In this talk, I will review my present understanding of the Hawking emission of Bogoliubov phonons from a sonic horizon in flowing one-dimensional Bose-Einstein condensates. Hawking processes are visible in the scattering of phonon wavepackets off the horizon and in the appearance of long-range correlations in the density fluctuations in the gas. A physical interpretation of Hawking processes in terms of parametric emission of Bogoliubov excitations is put forward and the quantum features of this process are emphasized. Advantages and disadvantages of atomic superfluids vs. luminous superfluids of exciton-polaritons in semiconductor microcavities are critically discussed with an eye to on-going experiments.
Date: Fri, 11.10.2013
Time: 15:30
Location:TU Wien Atominstitut, Seminarraum, Stadionallee 2, 1020 Wien
Contact:J. Schmiedmayer