Calendar of Physics Talks Vienna

Numerical Gravity - A Tool for High Energy Nuclear Physics?
Speaker:Paul Romatschke (INT, University of Washington, Seattle)
Date: Mon, 01.12.2008
Time: 15:00
Location:ITP, TU Wien, Wiedner Haupstr. 8-10, 1040, SEM136, 10. OG
Contact:rebhana ät tph.tuwien.ac.at

Manipulating single electron and nuclear spin in diamond
Speaker:Dr. Fedor Jelezko (University of Stuttgart)
Abstract:Diamond is famous for its exceptional properties like extreme hardness, high refractive index, and record thermal conductivity. That’s why applications of diamond cover a huge and ever growing field. In this talk I will focus on exceptional optical and spin properties associated with single impurity atoms in diamond crystal. Such defects have been identified as a prominent candidate for quantum information processing and quantum cryptography a few years ago, but technology for controlling single spins was developed only recently. In particular, now it becomes possible to place single impurity atoms into diamond lattice with high degree of control. Having single atom doping process at hand, we are able to explore single atoms for quantum applications. Usually single nuclear spin are difficult to control and read-out. This however is not the case for nuclei in the diamond lattice coupled to color centers. We demonstrate the generation and precise tomography of bi- and tripartite nuclear and electron nuclear spin entanglement. It proves that the quality of entanglement is excellent fostering their potential use in quantum applications like quantum teleportation protocols. Recent experiments related to applications of single spin ESR for magnetometry with atomic spatial resolution will be presented. References Balasubramanian et al. Nanoscale imaging magnetometry with diamond spins under ambient conditions. Nature 2008 Neumann, et al. Multipartite entanglement among single spins in diamond. Science ,2008
Date: Mon, 01.12.2008
Time: 17:30
Duration: 60 min
Location:TU Wien, Elektrot.Institutsg., EI 8 Pötzl HS Gußhausstr. 25-29, A 1040 Wien, Stiege 1, EG,
Contact:Prof. Jörg Schmiedmayer, ATI

Vienna Theory Lunch Club - Coherent scattering of fast atoms at surfaces
Speaker:Florian Aigner (TU Wien)
Abstract:Diffraction of particles scattered at surfaces was among the key experiments establishing the quantum wave nature of matter. Atoms being diffracted at crystal surfaces exhibit intriguing diffraction patterns, closely related to those visible in double-slit experiments, which have been carried out using particles as heavy as fullerenes. Scattering of keV atoms at surfaces has recently been shown to be a powerful tool to investigate the structure of surfaces. Even in environments which would strongly suggest the dominance of decohering effects (hot surfaces, phonon vibrations) quantum coherent scattering patterns remain visible. This is especially remarkable, as the de Broglie wavelength of scattered atoms in the keV range is as low as a few picometers.
Overview Vienna Theory Lunch Club
Date: Tue, 02.12.2008
Time: 12:30
Duration: 60 min
Location: TU Vienna, Inst. f. Theoretical Physics, Freihaus, Wiedner Hauptstr. 8-10, 10. OG, SEM136
Contact:Max Attems, Daniel Grumiller, Beatrix Hiesmayr

Chiral expansion of the pi-0 lifetime
Speaker:Karol Kampf (Paul Scherrer Inst., Villigen) (Fakutät für Physik)
Abstract:im Rahmen des Teilchenphysikseminars
Date: Tue, 02.12.2008
Time: 16:15
Duration: 60 min
Location:Großer Seminarraum, Boltzmanngasse 5, 5. Stock
Contact:H. Neufeld

Exchange-coupled Magnets: Challenges and limits
Speaker:Univ.Prof. Dr. Josef Fidler (Institut für Festkörperphysik der Technischen Universität Wien)
Abstract:The magnetic hysteresis properties of modern hard magnetic materials are primarily controlled by the microstructure which is defined by the type, the structure and the number of phases, by the size, shape and the topological arrangement of the individual phase regions and their interfaces, and by the type, structure and geometry of lattice defects. Exchange interactions between neighbouring soft and hard grains lead to remanence enhancement of isotropically oriented grains in nanocrystalline composite magnets. Hard magnetic thin films as magnetic data storage media layer are based on hard magnetic CoPt, FePt, CoPd alloys with a high magnetocrystalline anisotropy. Hard disk drives for ultra-high storage densities require grain sizes in the order of several nanometres to fulfil the requirements for high signal to noise ratios. In order to avoid the superparamagnetic effect of the spontaneous switching of the magnetization the anisotropy value has to be increased considerably. Such a high anisotropy will ensure thermal stability at small grain sizes leading to an areal density in the Tbit/in2 regime. However, conventional recording systems based on highly coercive grains require a write field that is higher than the field provided by conventional single pole heads. In order to overcome the problem of the insufficient write field new concepts based on exchange spring media, consisting of a hard layer and one or several soft layers have been developed. The theory predicts a coercive field of a bilayer system consisting of a hard layer which is exchange coupled to a soft layer, in the order of 1/4 of the anisotropy field of the hard layer. For multilayer structures (graded media) with gradually decreasing anisotropy in each layer the coercive field can be decreased even further. Besides the reduction of coercive field the energy barrier for thermal switching is close to the value which is determined by the anisotropy of the hard layer. On the basis of numerical micromagnetics the optimization and the limits of the switching properties on nm and ns length and time scales, respectively, will be shown.
Date: Tue, 02.12.2008
Time: 17:30
Location:1090 Wien, Strudlhofgasse 4 / Boltzmanngasse5; grosser Hörsaal der Experimentalphysik der Universität Wien

Supersymmetry and noncommutative quantum field theory
Speaker:Workshop in Memoriam Julius Wess
Date: Thu, 04.12.2008
Time: 09:20
Location:ESI Boltzmann lecture hall

CP Violation, Lattice Matrix Elements and Clues for TeV Scale New Physics
Speaker:Amarjit Soni (Brookhaven National Laboratory, Upton, New York) (Fakultät für Physik)
Abstract:im Rahmen des Teilchenphysikseminars
Date: Fri, 05.12.2008
Time: 11:00
Duration: 60 min
Location:Kleiner Seminarraum, Boltzmanngasse 5, 5. Stock
Contact:H. Neufeld

High-harmonic generation in molecules
Speaker:Prof. Manfred Lein, Universität Kassel (SFB ADLIS)
Date: Fri, 05.12.2008
Time: 14:00
Duration: 60 min
Location:Seminarraum CBEG02, Institut f. Photonik, Gußhausstr. 27
Contact:Heike Höller, SFB ADLIS Sekretariat, Tel: 58801 13625