GRK 2905 - Ultrafast Nanoscopy

RTG Colloquium:Franz Giessibl & Sabine Maier
2025-06-06 14:00 - 16:00 (Europe/Berlin)
Venue: Run auditorium2 pmAtomic Force Microscopy (AFM)This tutorial presentation builds on Jascha Repp’s introduction to scanning tunneling microscopy (STM) six months ago. STM relies on the monotonic exponential decay of the tunneling current with distance. This decay at a factor of ten per Angstrom distance reduction ensures a high spatial resolution and a relatively simple implementation of STM. AFM is harder, as the forces between a sharp tip and a sample often have strong long-range van-der-Waals compo-nents, the forces are non-monotonic and the experimental measurement of small forces measurements (nN and below) is more difficult than the measurement of tunnling currents (nA and below). Frequency modulation AFM with stiff self-sensing cantilevers (qPlus sensors) provides a powerful solution that even obtains higher spatial resolution than STM.

Prof. Dr. Franz J. GießiblUniversity of Regensburg

3 pmBottom-up fabrication and electronic structure of atomically precise low-dimensional materialsThe ability to engineer atomically precise low-dimensional structures with tailored electronic properties is essential for the development of future electronic and quantum materials. This presentation focuses on molecular architectures constructed through bottom-up surface reactions. By combining scanning probe microscopy with density-functional theory, we investigate their atomic-scale structure and electronic characteristics. Recent advances in the synthesis and characterization of surface-supported 2D polymers and nanographenes illustrate how structural precision enables electronic property control. These studies offer fundamental insights into the design and functionality of low-dimensional materials.

Prof. Dr. Sabine MaierFAU Erlangen-Nürnberg

RTG Colloquium:Jan Vogelsang & Gerti Beliu
2025-07-04 14:00 - 16:00
2 pmFrom single‐molecule fluorescence spectroscopy to (fast) super‐resolution microscopySuper‐resolution (SR) microscopy has revolutionized far‐field fluorescence imaging by overcoming the diffraction limit of light. The technique relies fundamentally on the ability to detect single fluorescent molecules, and the first part will focus on achieving this, which requires carefully optimized technical and photophysical needs, including the manipulation of fluorophore behavior through photoinduced redox reactions. The second part will focus on a novel approach using DNA origami nanoantennas to dramatically enhance fluorescencesignals in single‐molecule experiments. Such nanoantennas can increase the fluorescence of single molecules by an order of magnitude, which increases the time resolution and facilitates the observation of ultrafast processes such as thediffusive barrier crossing events between two potential energy minima in disordered proteins.

Dr. Jan VogelsangUniversity of RegensburgInstitute of Experimental and Applied Physics

3 pmClick. Tag. Image –A Hitchhiker’s Guide to Molecular BioimagingSuper‐resolution microscopy holds the promise of visualizing molecular processes in cells with nanometer precision. However, realizing this potential requires labeling strategies that are not only bright and site‐specific, but also biologically orthogonal. Many commonly used labeling approaches interfere with protein function or fail to access conformationally restricted or sterically masked epitopes in live‐cell environments. In our work, we develop and apply biochemical labeling strategies that combine genetic code expansion, bioorthogonal click chemistry, and fluorogenic dyes to overcome these limitations. By minimizing linkage errors and enabling stoichiometric labeling under native conditions, we aim to push the limits of resolution, specificity, and functional integrity in molecular imaging. This talk will provide an overview of our toolbox, recent applications, and future directions for nanoscale imaging of proteins in living systems.Venue: RUN auditorium

Prof. Dr. Gerti BeliuUniversity of RegensburgInstitute of Pharmacy

RTG Colloquium:Ulrich Höfer
2025-07-11 14:00 - 16:00
Formation of Floquet-Bloch bands in solidsPeriodic driving of electrons in solids by strong light fields can lead to the formation of Floquet- Bloch bands, i.e., sidebands separated by multiples of the driving frequency. The induced change of the electronic structure is one route to materials design by light. In 2009, Oka proposed that circularly polarized light can turn the semimetal graphene into a Chern insulator in this way. While transport experiments could so far not provide compelling evidence for the predicted anomalous Hall effect, time-resolved photoemission has clearly demonstrated the formation of Floquet-Bloch bands for several materials, including graphene. Moreover, with subcycle resolution, it has become possible to reveal their ultrafast build-up. These experiments show that Floquet sidebands emerge after a single optical cycle, concurrently with intraband acceleration of the electrons.Venue: RUN auditorium

RTG Colloquium:Prof. Dr. Miriam Vitiello
2025-11-21 14:00 - 15:00
Detector-less near-field quantum nanoscopy in the far-infraredNEST, CNR – Istituto Nanoscienze and Scuola Normale Superiore, Pisa, Italy

Near-field nanoscopy at terahertz (THz) frequencies (wavelength range, 3 mm – 3 µm) enables studies of objects over a large span of scales – from 300 µm to the nanometer scale – and disciplines, from physics to biological science. The talk will show the potential of a series of near-field nanoimaging approaches that, while exploiting the same core building block (a detector-less QCL-based nanoscope), rely on different physical mechanism for imaging reconstruction. I will also highlight their potential for tracing the realspace propagation of THz-frequency polaritons in isotropic and anisotropic nanomaterials and meta-elements.

Venue: RUN Auditorium

RTG Colloquium:Prof. Dr. Jim Freericks
2025-12-02 14:15 - 15:15
How to describe pump-probe experiments in quantum materialsGeorgetown University, Washington, USA

I will describe both the challenges, and how to address them, when theoretically modelling ultrafast pump-probe experiments in strongly correlated materials and in materials with strong electron-phonon coupling. After providing an introduction, I will focus on three case studies: (i) examining the response at picosecond times of charge-density waves with ultrashort pulses that drive the electrons; (ii) examining the response on femtosecond times for nonresonant electronic Raman scattering; and (iii) examining how one can measure correlated charge dynamics in f-electronsystems using x-ray photoemission spectroscopy and x-ray absorption spectroscopy.

Venue: H34

RTG Colloquium: Prof. Dr. Rudolf Bratschitsch
2026-01-16 14:00 - 15:00
Title: Magnonic waveguide networks

Ultrafast solid-state quantum optics and nanophotonics, Physical Institute, University of Münster, Münster, Germany

Spin waves (magnons) have emerged as a promising platform for next-generation physical computing. However, current experimental realizations of magnonic waveguides suffer from limited spin-wave propagation lengths and inefficient dispersion tuning capabilities. In my talk, I will present low-loss magnonic waveguides in a thin magnetic insulator film, fabricated with a new maskless silicon ion implantation technique. We demonstrate a large-scale magnonic network, paving the way for wafer-scale magnonic integrated circuits.

Venue: RUN Auditorium

RTG Colloquium:Dr. Anna Rosławska
2026-01-23 14:00 - 15:00
Single-molecule optics with atomic precision

Atomic Scale Optics, Max Planck Institute for Solid State Research, Stuttgart, Germany

Luminescence, photosynthesis, and energy harvesting rely on processes originating at the spatial scale of individual molecules. Investigating the details of these mechanisms requires reaching subnm precision in optics, which becomes possible by combining optical spectroscopy with scanningprobe microscopy. In my talk, I will discuss how atomic-scale optics can be used to study the optical properties of single molecules and to drive photochemistry with sub-nm precision.

Venue: RUN Auditorium

RTG Colloquium:Prof. Dr. Renske van der Veen
2026-01-30 14:00 - 15:00
Fast electrons and hard X-rays for unraveling atomic-scale dynamics in light-energy conversion

Department Atomic-Scale Dynamics in Light-Energy Conversion, Helmholtz Zentrum Berlin

The increasing demand for renewable and low-cost energy motivates intensive research aimed at characterizing and optimizing materials that can efficiently convert (sun) light into usable energy in the form of electricity or chemical fuels. Conventional characterization techniques either lack the spatial resolution necessary to resolve individual atoms, or they lack the temporal resolution required to capture structural rearrangements as they evolve. Our group develops complementary X-ray and electron-based tools to visualize light-induced processes in materials on atomic length and time scales. In this talk I will introduce you to the techniques of ultrafast/time-resolved X-ray spectroscopy and transmission electron microscopy and provide several examples of how these techniques can be used in the fields of solar energy and catalysis.

Venue: RUN Auditorium

RTG Colloquium jointly held with the Physics Colloquium: Oliver Graydon
2026-04-20 16:00 - 17:00
The role of AI in scientific publishing

Chief Editor Nature PhotonicsSpringer Nature, UK

Artificial intelligence (AI) is set to bring profound transformations in how science is conducted and communicated. This talk with discuss the trends, opportunities, risks and challenges associated with AI from the viewpoint of scientific publishing with a focus on clarifying the present policies and principles at Nature journals and Springer-Nature.

Venue: H34

RTG Colloquium: Zhiyang Zeng
2026-04-24 14:00 - 15:00
Dynamical control of structural order

Condensed Matter Dynamics DepartmentMPI for the Structure and Dynamics of Matter, Hamburg

Coherent excitation of lattice vibrations has emerged as a powerful approach to dynamicallycontrol functional material properties. In this talk, I will present our recent work on using nonlinearphononics—a mechanism that enables the selective displacement of specific lattice vibrations—tomanipulate structural functionalities with light [1,2]. In particular, I will discuss how this approachenables the ultrafast control of chirality [3] and ferroaxial order [4], offering new pathways to tailorsymmetry and drive phase transitions in solids on demand.

[1] Först, et al. Nature Physics 7 (2011): 854-856.[2] Disa, et al. Nature Physics 17 (2021): 611-618.[3] Zeng, et al. Science 387.6732 (2025): 431-436.[4] Zeng, et al. Science 390.6769 (2025): 195-198.

Venue: RUN Auditorium

RTG Colloquium: Thomas Taubner
2026-05-22 14:00 - 15:30
Infrared near-field spectroscopy of few-layer graphene

RWTH Aachen, Germany

Infrared scattering-type scanning-near-field optical microscopy (s-SNOM) enables the imaging of nanostructures with sub-diffraction resolution by elastic light scattering at a sharp tip. s-SNOM also boosted the field of 2D materials by enabling real-space imaging of plasmon- or phonon polaritons, e.g., in graphene and hexagonal Boron Nitride (hBN), respectively. Polariton imaging with s-SNOM has allowed for indirectly mapping (grain) boundaries and (stacking) defects in fewlayer Graphene (FLG) via polariton reflection.Here, I will present how spectroscopic IR s-SNOM is able to determine the local stacking order at nanoscale resolution not only of bare few-layer graphene, but also when it is encapsulated below hBN layers. I will explain the contrast mechanisms, mainly based on the characteristic and stacking-dependent interband transitions of FLG, for bilayer graphene, trilayer (TLG) graphene and tetralayer graphene (4LG). We retrieve and reconstruct these characteristic complex optical conductivity resonances from the amplitude and phase of the scattered light, which e.g. allow for the unambiguous assignment of previously undetected ABCB domains in 4LG.Coupling the (stacking-dependent) FLG with phonon polaritons in a hBN TLG heterostructure also leads to coupled polaritons (hyperbolic phonon plasmon polaritons). We explore how they allow for super-resolution imaging of subdiffraction-sized defects in graphene through the hBN cover layer via the so-called hyperlensing effect. Furthermore, we show how resonators for polaritons in 2D materials like hBN can be easily fabricated and optically reconfigured using Phase-Change Materials.

Venue: RUN Auditorium

RTG Colloquium: Gabriele Kaminski Schierle & Clemens Kaminski
2026-06-11 14:00 - 16:00
Biological imaging at the nanoscale

Clemens F. Kaminski, University of CambridgeThe advent of optical super‑resolution imaging together with the ability to label specific cellular components with fluorescent markers has ushered in a revolution in our mechanistic understanding of biological processes. In this presentation, I will provide an overview of current methods used to obtain nanoscale insights into the molecular machinery that supports life at the subcellular level. I will present approaches for tracking protein interactions, using single‑molecule localisation microscopy as well as indirect techniques such as fluorescence lifetime imaging microscopy. I will then discuss methods based on structured illumination microscopy, which enable dynamic interrogation of cellular machinery including lysosomes and the endoplasmic reticulum. Finally, I will offer an outlook on emerging trends and how machine learning is transforming our field.

Coffee break & discussion

Beyond Alzheimer’s: conserved lysosomal dyshomeostasis as a driver of synaptic dysfunction across neurodegenerative proteopathies

Gabriele S. Kaminski Schierle, University of Cambridge

While scientists know that in Alzheimer’s disease, lysosomes (the cell’s “trash cans”) clump together and lose their acidity, they didn’t know if this happens in all neurodegenerative diseases.This study found that this “trash can” breakdown actually happens across many diseases, including ALS, Parkinson’s, and Frontotemporal Dementia. Instead of being spread out normally to clean the whole cell, the lysosomes clump tightly around the cell’s centre.By tracking cell electricity and layout, the researchers discovered that this clumping severely damages brain signalling. Because the lysosomes are stuck in the centre, they can’t reach the distant outer branches of the brain cells to clear out old, broken proteins. This causes waste to build up and shorts out communication between neurons.Ultimately, this suggests that fixing where lysosomes sit and restoring their acidity could act as a single, powerful treatment for multiple brain diseases.

Venue: RUN Auditorium

RTG Colloquium: Alice Kunin
2026-06-19 14:00 - 15:00
High-performance time-resolved photoemission experiments of quantum materials

Princeton University

I will discuss our work coupling MHz, kW light sources with momentum microscopy to enable efficient time- and angle-resolved photoemission (tr-ARPES) studies. I will first examine the dynamics of intra- and interlayer excitons in twisted van der Waals heterobilayers. I will then discuss our current work on a new spectrometer to probe ultrafast surface photochemistry in situ with the extension of tr-ARPES beyond ultrahigh vacuum towards more realistic chemical environments.

Venue: RUN Auditorium

RTG Colloquium: Bruno Schuler
2026-07-03 14:00 - 15:00
Probing atomic defects in 2D semiconductors with light-coupled STM

Empa, Switzerland

Two-dimensional (2D) semiconductors provide an exciting platform to engineer atomic quantum systems in a robust, yet tunable solid-state system. This talk explores the intriguing physics of single point defects in transition metal dichalcogenide (TMD) monolayers, investigated through atomically resolved scanning probe microscopy.

We demonstrate electrically induced exciton emission from both pristine MoS₂ and individual charged defects using scanning tunnelling microscope luminescence (STML) on ultrathin hBN decoupling layers [1]. Furthermore, I will present our recent advances in time-resolved THz-STM using QEV maps to achieve state-selective ultrafast charge injection [2]. This approach enables the investigation of charge [3] and exciton dynamics [4] with atomic spatial, millielectronvolt energy, and picosecond temporal resolution.

By combining the structural and electronic properties accessible by conventional scanning probe microscopy with the optical fingerprint from STML and the excited-state dynamics revealed through pump-probe THz-STM, we gain a comprehensive microscopic understanding of localized quantum states in low-dimensional materials.

[1] L. Huberich et al. arxiv: 2510.15676 (2025)[2] L. Bobzien et al. APL Mater. 12, 051110 (2024)[3] J. Allerbeck et al. Nat. Commun. 16, 10806 (2025)[4] L. Bobzien et al. (in preparation)

Venue: RUN Auditorium
