11.01.2012

 Prof. Dr. Philipp Gegenwart
Georg-August-Universität Göttingen, Physikalisches Institut

 Quantenphasenübergänge                                                                                            

Atomare Teilchen bleiben als Folge der Heisenberg’schen Unschärferelation selbst am absoluten Temperaturnullpunkt beweglich. Diese Quantenfluktuationen können ebenso wie die üblichen thermischen Fluktuationen zu Transformationen zwischen verschiedenen Materiezuständen führen. Da bei T=0 keine thermischen Fluktuationen auftreten, werden Übergänge zwischen verschiedenen Grundzuständen alleine durch Quantenfluktuationen getrieben. In den letzten Jahren wurden Quantenphasenübergänge in verschiedenen Materialklassen untersucht, mit oft überraschenden Beobachtungen wie dem Zusammenbruch von Landaus Fermiflüssigkeitstheorie oder dem Auftreten von unkonventioneller Supraleitung. Im Vortrag werden neuartige Zustände in metallischen Systemen vorgestellt, welche in der Nähe von Quantenphasenübergängen auftreten.

18.01.2012

Prof. Dr. Anke-Susanne Müller
Karlsruher Institut für Technologie (KIT)

Coherent Synchrotron Radiation in the ANKA Storage Ring                                                                                           

Over the past few years highly intense radiation in the THz spectral range has become an important research tool. One possibility to generate intense coherent THz radiation with high repetition rates is the generation from ultra-short bunches in electron storage rings with quasi-isochronous lattices.

The power of the emitted coherent radiation scales with the number of electrons squared and with the form factor of the charge distribution. 

It is therefore extremely sensitive to even tiny changes of the longitudinal bunch profile. Such deformations can be caused for example by the strong coherent radiation field or by wake fields due to the ring’s geometric impedance. The investigation of the emitted coherent THz radiation therefore opens a new access window to longitudinal beam dynamics.

This talk will introduce the special requirements for the generation of coherent THz radiation in a storage ring and discuss the observations and experiences at ANKA.

25.01.2012

Dr. Matthias Schott
CERN European Organization for Nuclear Research, Genf, Schweiz

Search for Axions and Axion Like Particles

This talk focuses on the search for the axion, a hypothetical elementary particle which historically appeared in the solution to the Strong-CP problem in Quantum Chromo Dynamics.

Axions are currently the only good Cold Dark Matter candidate apart from supersymmetric particles. Although axions are expected to have only very small couplings to matter and radiation, several searches are underway.

In this talk, the state of experiments searching for the axion through its coupling to photons is reviewed. Special emphasis is drawn to light shining through wall type of experiments.

1.2.21012

Prof. Dr. Dominik Marx

Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum

Molecular Nano (Newton) Mechanics                                                                                            

The manipulation of covalent bonds in molecular systems using mechanical forces became possible only during the last decade. Several experimental advances made possible the site-specific application of forces in the nano-Newton range required to break or make chemical bonds. Much in parallel with experimental advances, theoretical approaches were developed which pave the way to understanding these phenomena. My lecture will give an overview of our efforts to unveiling the nanomechanical properties of molecule/metal junctions and of force-induced reactions in the condensed phase.

8.2.2012

Prof. Dr. Matthias Kling

Max-Planck Institut für Quantenoptik, Garching

Attosecond electron dynamicsin nanoparticles in strong laser fields

 Collective electron motion can unfold on attosecond time scales in nanoplasmonic systems, as defined by the inverse spectral bandwidth of the plasmonic resonant region [1]. Similarly, in dielectrics or semiconductors, the laser-driven collective motion of electrons can occur on this characteristic time scale [2]. The realization of electronics operating at Petahertz frequencies may be feasible by applying waveform controlled laser fields to nanoscale systems, where the nanolocalized near-fields enable for ultimate temporal and spatial control of the relevant electron transport processes. We have recently demonstrated the emission and directional control of highly energetic electrons from isolated nanoparticles in few-cycle laser fields [3]. Comparison of the experimental results to quasi-classical simulations reveals that the electron acceleration mechanism is based on rescattering in the enhanced near-field of the nanoparticles. Experiments, where such enhanced near-fields in plasmonic waveguides were utilized to generate high-order harmonics from a Ti:sapphire oscillator, comprising the most compact extreme ultraviolet light source [4], will be highlighted. Our aim is to measure the collective electron motion in nanostructures in strong laser fields in real-time. Theoretical [1,5] and experimental progress in this direction will be presented.