We are interested in the spatio-temporal response of solid state surfaces, quantum materials, and nanostructures following ultrafast optical or electronic excitation. Our goal is to obtain an atomistic understanding of photoinduced processes on (sub-) nanometer length and femtosecond time scales by employing novel pump-probe schemes for ultrafast scanning probe microscopy (SPM). We envision to study, drive and control solid state matter in highly non-equilibrium states and probe its dynamics locally at atomic scales.

To achieve this goal, we are putting efforts into the development of ultrafast scanning probe methods, with a focus on broadband THz-gated STM combined with femtosecond optical excitation and optical photon-assisted femtosecond STM. Besides detecting the localized tunneling signals, we complement our methodological approach by local light detection and optical near-field techniques. For detailed information and updates, please follow our news below.

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We are happy to announce that our collaborative work on the development of s-SNOM based on nc-AFM – utilizing ultralow tip oscillation amplitudes and detecting the elastic light scattering from ultraconfined fields localized at the 1-nm-scale – is now published in Science Advances. Using a silver tip under visible laser illumination with a constant 1-nm amplitude oscillation, we obtain a material-contrast image of silicon islands on a silver surface with 1 nm lateral resolution, surpassing the conventional limits of s-SNOM. These achievements pave the way for the acquisition of optical information from atomic-scale structures, such as single photo-active defects and molecules. You find the paper here: Sci. Adv. 11, eadu1415 (2025)

We are very happy to welcome Andrea to the ultrafast STM team as of 1st March! During his postdoc, Andrea will set up a broadband MIR light source and couple it to low-temperature STM to study MIR-driven tunneling phenomena and ultrafast processes in quantum materials. The new source complements our selection of ultrafast pulses that we can couple to the STM, and broadens the range of ultrafast phenomena that we expect to explore. Welcome Andrea!

You are interested in photoexciting an STM junction without directly illuminating it by a laser beam? Then check out our new paper on using plasmonic nanofocusing for the efficient and broadband generation of a localized surface plasmons (LSP) in low-temperature STM! In close collaboration with Chenfang Lin and Takashi Kumagai, we use plasmon-assisted field emission resonance tunneling to characterize the LSP excited remotely via adiabatic nanofocusing of surface plasmon polaritons on a tapered gold STM tip. The results are published in: Nanoscale, 2025, Advance Article

Check out our new paper on plasmonic light emission from ultrathin ZnO/Ag(111) embedded in a plasmonic nanocavity! Using STM luminescence, we show that inelastic charge transport across the interface between hexgonal few-layer ZnO and Ag(111)generates broadband plasmonic luminescence from the biased Ag – ZnO/Ag(111) nanocavity. This emission is spectrally low-pass filtered compared to the bare Ag nanocavity. Our results show that electron injection into the ZnO conduction band gives leads to this filtered plasmonic luminescence, with the “filter onset” dictated by the local electronic structure of the ZnO/Ag(111) heterostructure at the nanoscale. For more details, check out: H. Wiedenhaupt, Nano Lett. 25, 7, 2870–2877 (2025)