© Uni MS
  • 11.04.2024            Prof. Stefan Karpitschka


    Viscoelastic Contact Dynamics in Soft and Living Matter

    The contact dynamics of soft and living materials ubiquitously determine their mechanical interactions experienced in everyday life or technological applications. In this talk, I will present our recent progress on two types of dynamical contact mechanics problems: (i) Dynamical wetting of soft materials, which has recently gained significant interest in the soft matter community, allows to probe the response of soft solids to virtually infinitely sharp line tractions. It turns out that, on such small scales, solid surface tension and poroelastic phenomena cannot be ignored, leading to an intricate coupling of elastic, osmotic, and capillary forces. (ii) Gliding motility of filamentous cyanobacteria, for which no comprehensive explanation exists to date, relies on direct contact of the bacteria with solid surfaces. Harnessing mechanical instabilities, we could measure the forces involved in gliding motility on the scale of individual filaments and show that this type of motility requires adhesion. We expect these findings to be relevant far beyond cell motility research as these organisms belong to the oldest known forms of life on earth and played a key role in the oxygenation of our atmosphere, and today their giant blooms pose major ecological and economical challenges.
  • 18.04.2024            Prof. Pratika Dayal


    The emergence of galaxies in the first billion years: implications for reionization, cosmology and gravitational wave astronomy

    Galaxy formation in the first billion years marks a time of great upheaval in our cosmic history: the first sources of light in the Universe, these galaxies ended the 'cosmic dark ages' and produced the first photons that could break apart the hydrogen atoms suffusing all of space starting the process of 'cosmic reionization'. The past few years have seen cutting-edge instruments such as the James Webb Space Telescope (JWST) provide tantalising glimpses of such galaxies assembling in an infant Universe. Puzzlingly, these observations are also yielding a sample of unexpectedly numerous and large black holes (up to a 100 million solar masses) within the first 600 million years, posing an enormous challenge for galaxy formation models. I will show how this data is providing an unprecedented opportunity to pin down the reionization state of the Universe in addition to providing an unrivalled resource for understanding the reionization topology in the forthcoming era of 21cm cosmology. I will also show how these early systems provide a powerful testbed for Dark Matter models beyond "Cold Dark Matter". Finally, I will try to give a flavour of the gravitational wave event rates expected from such early black holes in the Laser Interferometer Space Antenna Array (LISA) era.
  • 25.04.2024            Prof. Reinhard Kienberger


    Attosecond science – from the beginning to measuring electron dynamics in molecules, solids and layered systems

    The generation and measurement of single isolated attosecond pulses in the extreme ultraviolet (XUV) at the beginning of this century has recently been awarded with the Nobel Prize in Physics [1]. This talk will give a historic review since the beginning of attosecond science and its impact on the understanding of electronic processes on the attosecond timescale.
    A pump/probe technique, “attosecond streaking” [2], was used to investigate electron dynamics on surfaces and layered systems with unprecedented resolution. Photoelectrons generated by laser based attosecond extreme ultraviolet pulses (XUV), are exposed to a dressing electric field from well synchronized few-cycle infrared (IR) laser pulses. The energy shift experienced by the photoelectrons by the dressing field is dependent on the delay between the XUV pulse and the dressing field and makes it possible to measure the respective delay in photoemission between electrons of different type (core electrons vs. conduction band electrons). The information gained in such experiments on tungsten [3] triggered many theoretical activities leading to different explanations on the physical reason of the delay. Attosecond streaking experiments have been performed on different solids [4,5], layered structures and liquids, resulting in different delays – also depending on the excitation photon energy. These measurements lead to a stepwise increase of the understanding of different physical effects contributing to the timing of photoemission. In this presentation, an overview on the different physical contributions to attosecond time delays in photoemission will be given. The “absolute” time delay, i.e. the delay between the instant of ionization and the emission of a photoelectron will be discussed and latest measurements will be presented.

    [1] M. Hentschel*, R. Kienberger* et al., Nature, 414, (2001)

    [2] R. Kienberger et al., Nature 427, 817 (2004)

    [3] A. Cavalieri et al., Nature 449, 1029 (2009)

    [4] S. Neppl et al., Nature 517, 342 (2015)

    [5] M. Ossiander et al., Nature 561, 374 (2018)

  • 16.05.2024            Prof. Eva Blasco / Prof. Regina Dittmann

    CRC 1459 Colloquium Poster 16.05.2024

    Bitte beachten: Dieses besondere Kolloquium wird vom CRC Intelligent Matter organisiert, deshalb findet es zu ungewohnter Zeit ( 15 Uhr s.t.) und an einem unüblichen Ort (Center for Soft Nano Science SON) statt.

    Link zur Vortragsankündigung auf der Webside des CRC 1459 Intelligent Matter

    Prof. Eva Blasco  Designing Intelligent Materials for 4D (Micro)Printing

    Prof. Regina Dittmann  From Nanoionic Processes to Neuromorphic Sensing

  • 06.06.2024            Prof. Thomas Gehrmann


    Precision theory predictions for high energy collider physics

    Modern particle collider experiments allow to measure scattering cross sections and particle production rates to high accuracy. These measurements provide in-depth information on the underlying particle dynamics, and they can be used for precision determinations of Standard Model parameters and in indirect searches for new physics effects. To match the quality of the experimental data, equally precise theory predictions are needed, which are obtained by going to high orders in perturbation theory. We describe techniques and recent results for precision calculations and discuss their impact for particle phenomenology on selected examples.

  • 13.06.2024            Prof. David Mapaung


    Brillouin Optomechanics in Photonic Integrated Circuits

    Stimulated Brillouin scattering (SBS) is a coherent optomechanical interaction between light and gigahertz acoustic waves that can unlock promising technologies including narrow-linewidth lasers, microwave photonic signal processing, and on-chip nonreciprocal light propagation. Recently, SBS has extensively been studied in integrated waveguides. However, many implementations rely on complicated fabrication schemes, using suspended waveguides, or non-standard materials. The absence of SBS in standard and mature fabrication platforms prevents large-scale circuit integration and severely limits the potential of this technology. In this talk, I will focus on our recent results on enhancement of SBS in scalable integration platform including silicon nitride [1-3] and thin-film lithium niobate [4] and I will discuss the potential applications of this technology.

    [1] R. Boter, K. Ye, Y. Klaver, R. Suryadharma, O. Daulay, G. Liu, J. van den Hoogen, L. Kanger, P. van der Slot, E. Klein, M. Hoekman, C. Roeloffzen, Y. Liu, and D. Marpaung
    Guided-acoustic simulated Brillouin scatering in silicon nitride photonic circuits
    Science Advances, vol. 8, no. 40, p. 2196, Oct. 2022

    [2] R. Boter, Y. Klaver, R. te Morsche, B. L. Segat Frare, B. Hashemi, K. Ye, A. Mishra, R. B. G. Braamhaar, J. D. B. Bradley, and D. Marpaung
    Simulated Brillouin scatering in tellurite-covered silicon nitride waveguides
    arXiv:2307.12814, Jul. 2023

    [3] K. Ye, Y. Klaver, O. A. Jimenez Gordillo, R. Boter, O. Daulay, F. Moriche, A. Melloni, and D. Marpaung
    Brillouin and Kerr nonlinearities of a low-index silicon oxynitride platform
    APL Photonics, vol. 8, no. 5, p. 51302, May 2023

    [4] Ye, Kaixuan, H. Feng, Y. Klaver, A. Keloth, A. Mishra, C. Wang, and D. Marpaung
    Surface acoustic wave Brillouin scatering in thin-film lithium niobate waveguides
    Optica Open. Preprint

    David Marpaung is a full professor leading the Nonlinear Nanophotonics group at the University of Twente, the Netherlands. He is a fellow of Optica (formerly OSA). He was the recipient of the 2015 Discovery Early Career Research Award (DECRA) from the Australian Research Council, the 2017 Vidi award and the 2019 START UP grant from the Netherlands Organisation for Scientific Research (NWO). In 2022 he was awarded the ERC Consolidator grant on the topic of 3D photonic circuits for Brillouin scatering. His research interests include integrated photonics, nonlinear optics, and microwave photonics.
  • 20.06.2024            Prof. Jörg Kröger


    Exploring quantum excitations and interactions with scanning probe methods

    The scanning tunneling and atomic force microscope represent suitable tools for the manipulation of matter at the atomic scale, which relies on the interaction between the microscope probe and the manipulated object. The colloquium presents the electrical-field control of the chemical-bond strength in a two-atom contact, the force involved in a single-molecule metalation reaction and the identification of chemically reactive sites. Besides mastering matter atom by atom, spatially resolved spectroscopy is a fascinating capability of scanning probe methods. The talk shows how inelastic electron tunneling is used to excite and measure quantum vibrations of tautomerized isomers as well as phonons of a two-dimensional lattice. The combination of experimental and simulated data highlights the role of matching orbital and vibrational symmetries as well as the importance of electronic resonances for effective quantum excitation.
  • 27.06.2024            Prof. Christian Schneider


    Controlling Excitons in van der Waals heterostructures with tunable optical cavities

    Monolayer transition metal dichalcogenides (TMDC) have emerged as a new and interesting platform for studies of tightly bound exciton in ultimately thin materials. Their giant dipole coupling to optical fields makes them very appealing for implementing novel photonic devices, and for fundamental, as well as quantum photonic investigations in the framework of cavity quantum electrodynamics [1]. For those investigations and applications, flexible, tunable, and user-friendly optical microresonators are key!
    I will discuss a technologically advanced implementation of a spectrally tunable, open optical cavity, which can be operated under cryogenic conditions in liquid helium free, magnetic optical cryostats [2], as well as at ambient conditions. It is ideally suited for the study the coherent interaction of light and matter, such as emergent exciton-polaritons in atomically thin materials and van der Waals heterostructures. I will discuss selected experiments, which outline the potential of our developed technology.
  • 04.07.2024             Verleihung des Lehrpreises / Prof. Beate Heinemann


    How Did Our Universe Begin and Why Do We Exist?

    Over the past 100 years, significant insights have been gained about the early stages of the universe, especially the first three minutes. These insights were gained through enormous progress in our scientific understanding in cosmology, astrophysics, particle and nuclear physics and theoretical physics. Following the "Big Bang," the universe, initially extremely hot and incredibly small, expanded rapidly and cooled down. It went through various phases that critically shaped our universe, making the existence of matter, galaxies, the Earth, and ultimately, human beings possible. I will discuss what we have learned, and in particular how particle accelerators have contributed to this understanding and what open questions remain to be answered hopefully in the not too distant future.
  • 18.07.2024            Prof. Roman Engel-Herbert


    Synthesis of Strongly Correlated Electron Systems in the Ultraclean Limit by Molecular Beam Epitaxy

    Maturing the thin film growth of emerging materials to reduce the level of defects is a mandatory prerequisite to study their intrinsic physics and to innovate new device functionalities. While this has been done with remarkable success in various traditional semiconductor materials using molecular beam epitaxy, ranging from monoelemental Group IV, to Group III-V all the way to Group II-VI compound semiconductors, it has been found challenging to expand beyond binary oxides, such as ZnO or MgO. In particular, in complex oxide materials containing two or more cations, which include functional oxides with perovskite structure, have been proved notoriously difficult to minimize point defect concentration. This provokes the question:

    Can we even achieve semiconductor-grade quality perovskite oxide thin films?

    In this talk I will introduce the fundamental challenges utilizing a conventional molecular beam epitaxy approach for the growth of complex oxides and present an alternative – a hybrid synthesis approach – as a potential way out to overcome existing challenges. Promising results obtained by hybrid oxide MBE will be presented and it is shown how peculiar transport phenomena emerge in the ultraclean limit of the material. The application potential of correlated oxides as alternative to replace conventional transparent conductor materials will be highlighted.