THz Structural Dynamics
THz Structural Dynamics
Research Group Sebastian Maehrlein
Research Group Sebastian Maehrlein


Welcome to the THz Structural Dynamics group …

    We, the team of the new THz structural dynamics group, are obviously fascinated about structural dynamics. Why that? Material properties and chemical reactions are fundamentally determined by the spatial arrangement of atoms, ions or molecules. If we can modulate or change this spatial structure on ultrafast time scales, we can control properties on demand or even discover new material features. For this, we generate highly intense and phase stable laser pulses in the THz and midinfrared spectral range, which enable us to coherently drive specific structural dynamics on their fundamental time and energy scales. Furthermore, we want to explore tailored lattice trajectories, which may help to steer solids into hidden states. Currently, we are focusing on phonon anharmonicities, molecular orientations in solids and dynamically disordered systems.

    Feel free to roam through our fields of research, follow us @sfmaehrlein or contact us any time.

    Latest news …

    New group member - Joanna
    Apr 2022
    Our group is now approaching a real dream team: Welcoming Joanna Urban as our new Postdoc adds one of the last missing puzzle pieces! From her previous research positions in France, Joanna brings exceptional expertise in spectroscopy and physics of layered materials for a variety of methods.

    What a pleasure to have you with us, Joanna!

    Joanna’s fun fact: She is clearly our group’s language guru; try to speak a number of European languages with her!
    New Publication - First 2D-HYPE Publication
    Mar 2022
    Congratulations to our PhD student Marie Cherasse for her first first-author publication. In the labs of Luca Perfetti she discovered via time resolved two-photon photoemission (2PPE) that the surface charge regions of hybrid organic-inorganic lead halide perovskites serve as a perfect test ground to probe the screening capabilities of their organic cations. We found strikingly different dynamics depending on the orientational degrees of freedom of the A-site cation in different crystallographic phases.

    M. Cherasse et. al., “Electron Dynamics in Hybrid Perovskites Reveal the Role of Organic Cations on the Screening of Local Charges”, ACS Nano Lett. (2022)
    New group member - Dorothée
    Feb 2022
    We are more than happy to welcome our newest group Member Dorothée Mader, who will be a joint PhD student together with the Lattice Dynamics group. Within the Max Planck-Radboud Center for IR-FEL spectroscopy she will work on phonon-driven switching of ferroic states. Welkom, Dory!

    Dorothée’s fun fact: She not only masters chiral distortions on the macroscopic, but also on the human length scale.
    Start of our ANR-DFG research consortium "2D-HYPE"
    Jan 2022
    We are extremely excited that our French-German research project on “Correlated electron and structural dynamics in quasi-2D HYbrid PErovskites” (2D-HYPE) got funded by ANR and DFG. Together with our French partners Luca Perfetti and Emmanuelle Deleporte, we will use complementary tools of time-resolved ARPES and nonlinear THz spectroscopy to investigate the crucial interplay of lattice, ionic and electronic degrees of freedom in this emerging class two-dimensional lead halide perovskite semiconductors.

    Dynamique des électrons et du réseaux dans les perovskites hybrides et quasi-2D ? …stay tuned
    New group member - Michael
    Aug 2021
    Very warm welcome to Michael Spencer, who joined our group as a PostDoc! Coming all the way from New York City, Michael brings his expertise in cavity polaritons, lasing of perovskites, and polarization resolved photoluminescence. What a catch!

    We are happy to have you with us, Michael!   

    Michael’s fun fact: Michael belongs to a unique species of scientists, perfectly fit to both urban and rural habitats.
    Part of the new the Max Planck Center
    Jul 2021
    We are excited to be part of the newly founded Max Planck-Radboud University Research Center for Infrared Free Electron Laser Spectroscopy! The Center enhances the joint research capabilities of the Max Planck Society and Radboud University (Nijmegen, NL) based on their unique Free Electron Laser instrumentation. We are proud to contribute with our complementary tabletop high-field THz/MIR lab in a joint project to seek for ultrafast, but permanent, switching of material properties via phonons. Join for a PhD position!
    New Publication - JPCL Cover
    Jun 2021
    Already 2nd cover story this year with our collaborators at Columbia University. Feifan Wang used our novel 2D-OKE technique to demonstrate how optical anisotropy and phase transitions can be tuned in alloyed CsxMA1−xPbBr3 lead halide perovskites.

    F. Wang, L. Huber, S.F. Maehrlein, and X.-Y. Zhu “Optical Anisotropy and Phase Transitions in Lead Halide Perovskites”, J. Phys. Chem. Lett. 12, 20, 5016–5022 (2021)
    Outreach – Documentary filming in our lab
    May 2021
    We are always enthusiastic to support and gain visibility for women in science. This time, we were especially proud to simultaneously support a young female filmmaker:
    Our PhD student Marie Cherasse was followed during her lab work by the director Hannah Kugel for a French documentary about independent women. The documentary will be submitted to an ARTE competition. Fingers crossed, Marie and Hannah!
    New publication - Ultrafast Kerr effect in anisotropic and dispersive media
    Mar 2021
    The interpretation of ultrafast pump-probe spectroscopy in solids can be extremely challenging or even misleading if anistropic and dispersive light propagation is overlooked. Here we joined forces with L. Huber et al. from Columbia University to give a comprehensive four-wave mixing model for these phenomena; relevant to all types of time- and polarization-resolved methods, such as OKE, MOKE and Faraday effect. With this general model, the observed features can be used to quantitatively determine the anisotropic refractive index and group index dispersion. J. Chem. Phys.: [more...]
    New publication - Two Dimensional Optical Kerr effect in Hybrid Semiconductors
    Feb 2021
    Optoelectronic devices, such as photovoltaics or light-emitting diodes, are based on the interaction of light with charges in the active material. Lead halide perovskites (LHPs) have emerged as excellent materials for optoelectronics, but mysteries remain as to how these materials interact with light. In the X.-Y. Zhu group at Columbia University, S. Maehrlein and coworkers developed a multidimensional spectroscopic method (2D-OKE) to observe the nearly instantaneous responses of LHPs to propagating light fields. This novel method has allowed us to precisely trace a nonlinear material response resulting from the mixing of different light components overtaking each other during [more...]