RTG Colloquium: Thomas Taubner
2026-05-22 14:00 - 15:30 (Europe/Berlin)
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 Seminar: Prasana Kumar Sahoo
2026-06-18 14:00 - 15:00
Engineering excitons in 2D lateral heterostructures for reconfigurable devices

Quantum Materials & Device Research Lab (QMDrL), Materials Science Centre,Indian Institute of Technology Kharagpur, India

Two-dimensional semiconductor lateral hetero-structures (LHS) provide atomically sharp 1D interfaces for controlling charge carriers, excitons, and light. I will present scalable growth of seamless TMD LHS, exhibiting tunable PN junctions, electroluminescence, excitonic transistor operation, and reversible photoconductivity. These materials offer a versatile platform for quantum photonics, exciton-based devices, and low-dimensional quantum systems.

Venue: RUN 0.34

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

Workshop: Drama and the Scientist
2026-07-16 08:00 - 17:00
One-day in person workshop with Julie Stearns (professional theater director & artistic director) for RTG 2905 students.

Theater training for effective communication

Julie Stearns, impuls plus

“Scientists often try to avoid dramatization – but on the stage, the dramaturgy of a performance is the result of techniques that can be learned and applied. This workshop prepares participants for the challenges of interaction in academic and research settings, especially when the goal is to engage and persuade an audience. Through exercises in physical presence and voice, participants develop a new awareness of how to shape their own performance, while also gaining confidence in improvisation.” [J. Stearns, impuls plus]

Venue: RUN Auditorium
