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




    New paper: Ultrafast modulation of a material's Fermi surface topology
    Apr 2021
    The transport of electrons is governed by the shape of the Fermi surface. We found that the topology of the Fermi surface of a semimetal can be manipulated on ultrafast timescales through optical excitation. A change in the Fermi surface topology, also called Lifshitz transition, can lead to the emergence of fascinating phenomena like colossal magnetoresistance and superconductivity. Combining time-resolved multidimensional photoemission spectroscopy and TDDFT+U simulations, we introduce a scheme for driving an ultrafast Lifshitz transition in the correlated type-II Weyl semimetal Td-MoTe2. We show that this non-equilibrium topological transition finds its microscopic origin in the dynamical modification of the electronic correlations.
    Beaulieu et al., Science Advances 7, eabd9275 (2021). Link [more...]
    A link between exchange striction and nonthermal Lattice Dynamics
    Apr 2021
    Our recent study of ultrafast lattice dynamics in NiO has demonstrated the existance of a nonthermal phonon population, and that this is directly linked to change in the antiferromagnetically-induced lattice distortion, known as “exchange striction”. The study was enabled by combining unique capabilities of two institutions: growth of a 20nm-thick free-standing NiO single crystal at the university of Halle, and state-of-the-art femtosecond electron diffraction at the Fritz Haber Instititue. The study open a new avenue towards ultrafast control of antiferromagnets via the crystal lattice.
    Windsor et al, Phys. Rev. Lett. 126, 147202 (2021)
    New preprint: Bloch Wavefunction Reconstruction using Multidimensional Photoemission Spectroscopy
    Mar 2021
    The most advanced experimental technique to measure the electronic band structure of solids is angle-resolved photoemission spectroscopy (ARPES). While ARPES directly maps the momentum-resolved electronic eigenvalues (energy bands), topological properties are often hidden in the complex-valued Bloch wavefunction, which is not directly accessible in standard photoemission experiments. In a recent joint experimental and theoretical work in collaboration with Dr. Michael Schüler and Prof. Thomas Devereaux from Stanford University, we have found a novel approach to reconstruct the Bloch wavefunction of WSe2 from polarization-modulated ARPES, with minimal theory input (arXiv:2103.17168).
    New group member: Ashutosh Rathi
    Jan 2021
    We are happy to welcome our new Postdoc Ashutosh Rathi to the group!
    A quantitative comparison of time-of-flight momentum microscopes and hemispherical analyzers for time-resolved ARPES experiments
    Dec 2020
    Recent advancements in time-of-flight-based momentum microscope development have led to a growing presence of this novel detection scheme in photoemission studies, as it enables highly parallelized and simultaneous acquisition of the full 3-dimensional momentum- and energy-resolved photoelectron distribution. Combining such instruments with modern high-repetition-rate extreme ultraviolet (XUV) laser sources for ultrafast pump-probe photoemission experiments seems like an ideal match, and is followed by several groups worldwide. However, particularly important for time-resolved studies, several factors such as space-charge effects need to be considered and depend on the chosen analyzer type.
    In our study (Rev. Sci. Instr. 91, 123112 (2020)) we present a first benchmark comparison of the momentum microscope and the current standard [more...]