Dr. Saskia Hekker, Leiterin einer Max-Planck- Forschungsgruppe und ERC Starting Grant: "Das Alter von Sternen und galaktische Entwicklung" am Max-Planck-Institut für Sonnensystemforschung, Göttingen

Stars are opaque bodies and one may wonder how we can ever obtain knowledge of that which is hidden behind these substantial barriers (Arthur Eddington 1922). The answer to this is asteroseismology, a quasi-direct way to peer inside stars through their global oscillations. These global oscillations have provided essential insights into the internal structures of the Sun (helioseismology) and many other stars. Results based on state of the art (space) telescopes and the potential of asteroseismology for the near future, will be discussed during this talk.

 

 

 

Dipl.-Phys. Ulrike Böhm, Abteilung NanoBiophotonik, Max-Planck-Institut für Biophysikalische Chemie, Göttingen

Throughout the 20th century it has been widely accepted that, at the end of the day, a light microscope relying on conventional lenses (far-field optics) cannot discern details that are finer than about half the wavelength of light (> 200 nm). However, in the 1990s, it was discovered that overcoming the diffraction barrier is realistic and that fluorescent samples can be resolved virtually down to molecular dimensions.

Here I discuss the simple yet powerful principles that allow neutralizing the resolution-limiting role of far-field optical diffraction. In a nutshell, features residing closer than the diffraction barrier are prepared in different molecular (quantum) states so that they are distinguishable for a brief detection period. As a result, the resolution-limiting role of diffraction is overcome, and the interior of transparent samples, such as living cells and tissues can now be imaged non-invasively at the nanoscale using focused light in 3D.

Besides discussing basic principles, I will show most recent advancements. In particular, I demonstrate massive parallelization of RESOLFT and STED recording using simple pattern of light, by more than 100,000 fold. Likewise, I demonstrate the relevance of emerging ’far-field optical nanoscopy’ to various areas especially to the life and the material sciences.

Prof. Dr. Angela Rizzi, IV. Physikalisches Institut-Festkörper und Nanostrukturen, Georg-August-Universität Göttingen

In the International Year of Light and Light-based Technologies - a global iniiative for 2015 that has been adopted by the United Nations to celebrate light and optical technologies - it is worth talking about solid-state lighting (SSL). Artificial lighting uses up about 20 % of global electricity consumption, similar to the amount of electricity generated by nuclear power. Through optimal use of Light-Emitting-Diode (LED) lighting this consumption can be considerably reduced.
The invention of efficient blue-light emitting diodes mid 1990s has opened the way to the realization and commercialization of bright and energy-saving white light sources for illumination (Nobel Prize
in Physics 2014). In this talk we will review the LED basics, the breakthroughs towards high-brightness blue-LEDs as well as the white LED-technology from the perspective of a physicist and material scientist.

 

 

Lichtstrukturen - mit Licht Materie strukturieren

Dr. Saša Bajt, Deutsches Elektronen-Synchrotron, Hamburg

A lot of what we know about the structure of materials we gained either from transmission electron microscopy or x-ray crystallography. X-rays have been used to study the structure of materials on the atomic and molecular level almost since their discovery. With recent development of highly intense X-ray free electron lasers we can now also study the dynamics of reactions and processes and obtain high-resolution images of biological samples before the onset structural degradation due to the radiation itself. This presentation will cover some of the newest developments in controlling x-rays and x-ray pulses using novel x-ray optics.

 

 

Dr. A. Julia Stähler, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin

Light absorption in a semiconductor creates non-equilibrium conditions that relax by a multitude of pathways involving electron dynamics on femto- and picosecond timescales. These can be monitored in real time using time-resolved one- and two-photon photoelectron spectroscopy of the occupied and unoccupied electronic structure, respectively. On ZnO(1010), hydrogen adsorption causes the formation of a charge accumulation layer through downward surface band bending. Despite this metallicity, highly stable sub surface-bound excitons form within only 200 fs after above band gap photoexcitation. Strong excitation close to the Mott limit enhances the screening of the Coulomb interaction (CIA) and reduces the exciton formation probability [1]. On the other hand, in the case of the strongly correlated electron material VO2 , strong photoexcitation even leads to an instantaneous collapse of the band gap, followed by hot carrier relaxation within 200 fs. In conjunction with many body perturbation theory, these results show that the photoinduced semiconductor-to-metal transition is caused by photohole doping at the top of the VO2 valence band: The significantly enhanced screening of the CIA through low-energy intraband transitions causes the drastic band gap renormalization [2].
[1] J.-C. Deinert et al., Phys. Rev. Lett. 113, 057602 (2014)
[2] D. Wegkamp, M. Herzog et al., Phys. Rev. Lett. 113, 216401(2014)

 

 

Prof. Dr. Caren Hagner, Forschungsgruppe Neutrinophysik, University of Hamburg

Die Neutrinophysik hat in den letzten Jahren eindrucksvolle Entdeckungen gemacht. Aus der Beobachtung von Neu trinooszillationen wissen wir nun, dass das Standardmodell der Teilchenphysik erweitert werden
muss. Welche neue Physik dahinter steckt ist die große Frage. Im Vortrag werde ich am Beispiel des Opera Experimentes zeigen, wie Neutrino Wechselwirkungen sichtbar gemacht werden können und welches Bild der Welt der Elementarteilchen sich aktuell daraus ergibt. Im zweiten Teil des Vortrags möchte ich das Borexino Experiment vorstellen. Durch aufwendige Abschirmung und neu entwickelte Reinigungsverfahren gelang es hier erstmals ein großes Detektorvolumen mit extrem geringem radioaktivem Untergrund zu schaffen. Dies erlaubt es uns Neutrinos als Botschafter aus dem Inneren der Sonne und dem Inneren der Erde zu beobachten, um faszinierende Einblicke in die dort ablaufenden Kernprozesse zu gewinnen.

 

 

Dr. Carolina von Essen, Department of Physics and Astronomy - Stellar Astrophysics Centre, SAC Aarhus (DK)

When the orbital configuration is such that an extrasolar planet happens to eclipse the star as seen from the Earth, the observed brightness of the star drops a small amount. The analysis of this variability is the foundation of the transit method. In the simplified case where the transiting system is conformed by a central body (the star) and one secondary body (the planet), the movement of the latter around its host will occur exactly periodically. However, if further bodies are present in the system, due to mutual gravitational interactions their orbits will speed up and slow down by small amounts that will lead to deviations from exact periodicity. This timing shifts, in principle measurable from the ground, provide the basis of the transit timing variation method. During this talk I will show you results from KOINet, a network of telescopes I build up located between the United States and China organized to fulfil a common goal: the follow-up of  ̃60 Kepler Objects of Interest to characterize their masses and, in some cases, to validate them as exoplanets.

 

 

Prof. Dr. Ana‐Sunčana Smith, Theoretische Physik/Cluster of Excellence “Engineering of Advanced Materials”, Universität Nürnberg-Erlangen

While it is well established that mechano-sensitivity determines the structure of the cytoskeleton and the protein expression in single cells, the coupling between mechanical and biochemical signals in tissues is poorly understood. Therefore, our aim is to identify the physical principles that govern the growth and stability of epithelial tissues, which we grow from a single cell to macroscopic dimensions. During this process we monitor the distribution, the structure, and motions of cells as the tissues spontaneouly compartmentalizes, and enters a contact inhibited steady state. We analyze this state using tools of statistical physics and model the dynamics of
growth to show that the emergent structure is a result of a volumentric growth induced by cell divisions and the generation of forces of cells at the edge of the colony.

 

 

Dr. Marion Esch,  Stiftung für MINT-Entertainment-Education-Excellence, Berlin

Der Beitrag zeigt Forschungbefunde zum Potenzial von Spielfilmen und Serien für die MINT-Wissenschaftskommunikation und Nachwuchswerbung auf. Eigene Programmanalysen der reichweitenstärksten deutschen Sen-
der machen deutlich, dass diese Potenziale in Deutschland kaum genutzt werden: Anders als in amerikanischen Quality-TV-Formaten sind in deutschen Eigenproduktionen MINT-Role-Models
kaum zu finden. Warum das so ist und welche Ansatzpunkte zur Ver ̈anderung sich bieten, wird abschließend vorgestellt und diskutiert.

 

Dr. Ilaria Zardo, Photonics and Semiconductor Nanophysics, Technische Universiteit Eindhoven, Hertha-Sponer-Preisträgerin 2015

The interest in low dimensional systems has been steadily growing over the last decades. A particularly interesting system is provided by nanowires (NWs). The functional properties of NWs can be manipulated by tuning the crystal structure, and by the fabrication of 3-dimensional complex novel architectures. These unique material design features can be exploited to investigate and manipulate latticdynamics and phonon transport at nanoscale level. Apart from the fundamental interest, these studies can provide new pathways and systems to boost thermoelectricity.

The talk will focus on showing the understanding of the modifications of the lattice dynamic and optoelectronic properties of semiconductor NWs with respect to the bulk counterpart due to the different crystal phases [1-3]. Furthermore, we report on our investigations of the thermoelectric properties of semiconductor NWs.
[1] S. Assali et al., Nano Lett., 13, 1559, (2013).

[2] S. Funk et al., ACS Nano, 7, 1400, (2013).

[3] I. Zardo et al., Nano Lett., 13, 3011, (2013)