Dynamics of Correlated Materials
Dynamics of Correlated Materials
Emmy Noether Group Laurenz Rettig
Emmy Noether Group Laurenz Rettig


Welcome to the Dynamics of Correlated Materials group!

    We are an experimental research group focusing on the investigation of ultrafast processes in strongly correlated materials. Our goal is the understanding of the fundamental interactions at play on the microscopic level in such materials, leading to complex behavior. We develop and employ complementary ultrafast techniques such as time- and angle-resolved photoelectron spectroscopy (trARPES) and time-resolved diffraction techniques to study those elementary interaction processes and couplings across ultrafast phase transitions.




    Paper published: Robust magnetic order upon ultrafast excitation of an antiferromagnet
    Nov 2022
    Understanding the microscopic mechanisms behind ultrafast magnetization dynamics remains an important issue in solid state physics. Numerous studies have successfully applied variations of three-temperature models to describe experimental ultrafast magnetization dynamics. By introducing effective temperatures for the transient electronic, lattice and spin degrees of freedom (see figure), the 3TM provides an intuitive, phenomenological approach for the quantitative analysis of ultrafast magnetization dynamics using three coupled differential equations to describe the mutual energy transfer between the subsystems. However, comparison of model predictions are often only made with one of the subsystems.
    In our study (Adv. Mater. Interfaces 2201340 (2022)), we investigate the femtosecond dynamics of electronic temperature, sub-surface ferromagnetic ordering [more...]
    Paper published: Ultrafast Momentum-Resolved Hot Electron Dynamics in the Two-Dimensional Topological Insulator Bismuthene
    Jun 2022
    In the quest to continue Moore´s law, utilizing the electron´s spin degree of freedom poses a promising approach. A material class that intrinsically enables efficient spintronic applications are quantum spin Hall (QSH) insulators, also termed 2D topological insulators, as they allow for dissipationless spin-currents in their edges. However, exploiting the transport properties of such edge states is so far restricted to cryogenic temperatures, as only a few QSH materials with small bulk band gaps are available. Here, graphene-like 2D structures of heavy atoms, most notably bismuthene, i.e., a honeycomb lattice of Bi atoms on a semiconductor substrate, offer a route to QSH conductivity far beyond room-temperature due to their large spin-orbit coupling.
    In our recent study [Maklar et al., Nano Letters (2022)], we present a detailed investigation of the ultrafast [more...]
    New Preprint: Coherent Light Control of a Metastable Hidden Phase
    Jun 2022
    Active control over macroscopic properties of solids is highly desirable for a broad range of applications. A promising pathway to on-demand material properties are metastable hidden states, which are nonequilibrium phases that can only be reached after a quench by ultrashort optical or electrical pulses. As hidden states often host new emergent properties and can be switched on ultrafast timescales through non-thermal reaction pathways, they offer exciting novel functionalities for solid-state quantum devices. Yet, the fundamental processes that govern the dynamical pathway to hidden phases remain a largely open subject. Thus, switching is mostly based on empirical protocols, resulting in low efficiencies and limited control over stability.
    In our recent study (arXiv link), we investigate the dynamical pathway to the metastable hidden quantum [more...]
    Paper published: Coherent Modulation of Quasiparticle Scattering Rates in a Photoexcited Charge-Density-Wave System
    Jan 2022
    In our recent combined experimental and theoretical study [Maklar et al., Phys. Rev. Lett. 128, 026406 (2022)], we investigate how a dynamical insulator-to-metal transition affects fundamental interactions, such as electron-electron and electron-phonon scattering. We utilize optical excitation to transiently alter the energy gap of a charge-density-wave compound and observe a concurrent, highly unusual modulation of the relaxation rate of hot quasiparticles. State-of-the-art calculations based on non-equilibrium Green’s functions provide a microscopic view onto the interplay of quasiparticle scattering and the transiently modified electronic band structure, highlighting the critical role of the phase space of electron-electron interaction. Our results vividly demonstrate the possibility of controlling quasiparticle relaxation rates [more...]
    New preprint: Exchange scaling of ultrafast angular momentum transfer in 4f antiferromagnets
    Sep 2021
    When photoexcited by an ultrafast laser pulse, antiferromagnets allow direct angular momentum transfer between opposing spins, promising faster functionality than ferromagnets, which are intrinsically limited because their net angular momentum must dissipate to the lattice. The process of angular momentum transfer is closely linked to the nature of magnetic coupling in the system. In lanthanides, 4f magnetic exchange is mediated indirectly through the conduction electrons (the Ruderman–Kittel–Kasuya–Yosida interaction, RKKY), and the effect of such conditions on the antiferromagnetic direct spin transfer is largely unexplored.
    In our study we used resonant ultrafast X-ray diffraction to study ultrafast magnetization dynamics in a series of 4f antiferromagnets, and systematically varied the 4f [more...]