P4: Disentangling electronic and lattice dynamics in kagome metals

• Applicant: Professorin Dr. Hélène Seiler
• Subject Area: Experimental Condensed Matter Physics
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 531215165

A central goal of OPTIMAL is the optical control of quantum materials via impulsive excitation. Achieving this goal goes hand in hand with a deep understanding of the microscopic interactions between electrons and phonons. In project P4 we aim to disentangle electronic and lattice contributions and their mutual interactions in kagome metals. We will employ ultrafast electron diffraction as a direct probe of coherent and incoherent lattice dynamics in momentum space. We will employ coherent two-dimensional spectroscopy at optical frequencies to probe nonthermal electron distributions, coherences, and to implement optical control schemes based on pulse shaping. Combining these two state-of-the-art techniques, we will tackle research questions such as: What are the dissipation pathways in photoexcited kagome metals? What is the role of the lattice in establishing emerging ordered phases? To what extent are there nonthermal hidden phases of the crystal lattice? To what extent can we exploit pulse shaping technology for coherent control schemes? What is the role of out-of-plane lattice dynamics in establishing the CDW phase? The project is strongly connected to a project, which employs the complementary method of time- and angle-resolved photoemission spectroscopy (trARPES) to resolve the electronic dynamics in kagome metals in momentum space. Strong synergies also exist with, where trARPES and phonon pumping will be employed for band structure engineering. The information gained about the dissipation pathways as well as coherent lattice motions in kagome metals will be crucial. For the same reasons, it is closely connected to a project, which aims to employ collective modes in micro-structured cavities. Our project also features a strong connection to Schlawin, with whom we aim to push the field of 2D spectroscopy of quantum materials forward with a combination of experiments and simulations. We envision potential collaboration with PI Eckstein on the theoretical modelling of driven ordered states. Last but not least, the time-resolved inelastic x-ray experiments on kagome metals planned by Mercator fellow Matteo Mitrano directly complement the ultrafast electron diffraction studies.

• DFG Programme: Research Units
• Subproject of: FOR 5750: Optical Control of Quantum Materials (OPTIMAL)