FACHBEREICHSKOLLOQUIUM
© Uni MS
  • 11.04.2024            Prof. Stefan Karpitschka

    Vortragsankündigung

    tba

  • 18.04.2024            Prof. Pratika Dayal

    Vortragsankündigung

    tba

  • 25.04.2024            Prof. Reinhard Kienberger

    Vortragsankündigung

    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)

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

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

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

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

  • 02.05.2024            Prof. Hendrik Bentmann

    Vortragsankündigung

    Tracing topological states in 2D and 3D quantum materials

    Similar to knots in a rope, the electron wave functions in a crystal can be characterized by mathematical tools of topology. The classification of electronic phases of matter via topological invariants now complements the established paradigm of spontaneously broken symmetries. In this colloquium, I will present our efforts to uncover novel topological phases based on angle-resolved photoelectron spectroscopy (ARPES).  The first part of the talk will focus on the combination of electronic topology and magnetism in the van der Waals (vdW) magnet MnBi2Te4. I will concentrate, especially, on the two-dimensional (2D) limit of a single MnBi2Te4 vdW layer, interfaced with a non-magnetic topological insulator, Bi2Te3. In the second part of the presentation, I will discuss how dichroism in ARPES can enable direct imaging of wave-function topology, focusing on nodal points and lines in the band structure of topological semimetals.
  • 16.05.2024            CRC1459    

    Vortragsankündigung

    tba

  • 06.06.2024            Prof. Thomas Gehrmann

    Vortragsankündigung

    tba

  • 13.06.2024            Prof. David Mapaung

    Vortragsankündigung

    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

    Vortragsankündigung

    tba

     
  • 27.06.2024            Prof. Christian Schneider

    Vortragsankündigung

    tba

  • 04.07.2024             Verleihung des Lehrpreises / Prof. Beate Heinemann

    Vortragsankündigung

    tba

  • 18.07.2024            Prof. Roman Engel-Herbert

    Vortragsankündigung

    tba