Physics Colloquium -- Wintersemester 2021 / 2022

Time: Tuesdays 16.15

Location: Geiger Lecture Hall (Leibnizstrasse 15). The event will be held in a hybrid format and streamed as a videoconference.

Organizer: Prof. Fabio Caruso





ZOOM Meeting ID: 678 9814 9924
Passcode: 386752


  • 26. Okt. 2021

  • 2. Nov. 2021: Prof. Ulrich Hohenester (Graz)
    Light at the nanoscale: How can we measure it and what can we do with it?
    Ulrich Hohenester

    Nano-Optics is concerned with the manipulation of light at or beyond the diffraction limit. Light confinement in subwavelength volumes is achieved by binding light to plasmonic or phononic resonances of nanoparticles.

    In this talk, I will first report on our efforts to measure and reconstruct the three-dimensional vectorial fields in nanophotonic environments, using electron energy loss spectroscopy (EELS), a technique based on electron microscopy, together with plasmon field tomography [1]. With the newest generation of electron microscopes, the energy resolution can be further pushed to the meV range and it becomes possible to image the surface and bulk phonon polariton fields in ionic nano­structures [2]. Recently, we have reconstructed the three-dimensional vectorial fields of such phononic nanostructures from a series of tilted EELS images [3].

    In the second part of this talk, I will report on an unrelated subject of real-time nanoparticle characterization using optical forces and torques exerted by a focused Laguerre-Gaussian laser beam with an orbital angular momentum [4]. With this setup we demonstrate real-time optical counting of nanoparticles in a microfluidic channel with single-particle sensitivity, high through­put, and for particle sizes ranging from tens of nanometers to several micrometers. Such nanoparticle counting is crucial for numerous pharmaceutical and technological applications, as well as for medical diagnostics.

    [1] O. Nicoletti et al., Nature 502, 80 (2013); A. Hörl et al., Nat. Commun. 8, 37 (2017).
    [2] M. J. Lagos, A. Trügler, U. Hohenester, P. E. Batson, Nature 543, 533 (2017).
    [3] Xiaoyan Li, G. Haberfehlner, U. Hohenester, O. Stéphan, G. Kothleitner, M. Kociak, Science 371, 1364 (2021).
    [4] M. Simic et al., submitted (2021).

    Einladende: Nahid Talebi

  • 9. Nov. 2021: Prof. Stan Williams (KINSIS)
    Online only event
    Diels-Planck Price Lecture

  • 16. Nov. 2021: Prof. Ronny Brandenburg

    Einladender: Jan Benedikt

  • 23. Nov. 2021: Prof. Ursula Wurstbauer (University of Münster)
    Light matter interaction in 2D quantum materials
    Prof. Dr. Ursula Wurstbauer (Copyright „WWU - Peter Leßmann“)

    Quantum materials are of increasing interest and relevance for technological applications as well as in fundamental sciences. Quantum materials host controllable quantum states and emerging phases driven by various interactions. 2D quantum materials can be precisely tailored on the atomistic level and integrated in opto-electronic circuits towards applications in the fields of quantum computation, sensing, information and cryptography. Interactions in 2D quantum systems can be engineered by stacking, precise twisting or by selectively inducing defects. In-situ control can be realized by external stimuli such as electric or magnetic field and charge doping in field effect structures.

    We demonstrate strong exciton dominated light-matter interaction in semiconducting transition metal dichalcogenides (SC-TMDCs) monolayers, van der Waals hybrid-structures and defect engineered quantum emitter structures. We will discuss recent developments in the area of electric field controlled multi-valley physics and condensation signatures in TMDC hetero-bilayers. Furthermore, we will introduce a rather new class of 2D materials, 2D polar metals and focus on their linear optical response measured by spectroscopic ellipsometry.

    We acknowledge funding by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany´s Excellence Strategy – EXC 2089/1 – 390776260 and projects Wu 637/4- 1, 4 – 2, 7-1 and SPP 2244. Copyright for the picture is "WWU - Peter Leßmann".

    Einladender: Michael Bauer

  • 30. Nov. 2021: Prof. Tim Wehling

    Einladender: Fabio Caruso

  • 7. Dez. 2021: Dr. Tobias Dornheim (Helmholtz-Zentrum Dresden-Rossendorf)

    Einladender: Michael Bonitz

  • 14. Dez. 2021

  • 21. Dez. 2021: Dr. Ulf Zastrau (European XFEL)

    Einladender: Michael Bonitz

  • 11. Jan. 2021

  • 18. Jan. 2021: Prof. Peter Hommelhoff (Universität Erlangen)

    Einladender: M. Bauer

  • 25. Jan. 2021

  • 1. Feb. 2021

  • 8. Feb. 2021

  • 15. Feb. 2021