TeraDynamics Group
Many quasiparticles and excited states in quantum materials, which will form the material basis of the next revolution in computing efficiency, have excitation energies in the THz frequency band. Examples are phonons, magnons, charge-density waves, electromagnons, heavy-fermion coherence gaps, superconductor Higgs modes, Majorana fermions, and topological edge states. The TeraDynamics group investigates the material properties that emerge as a result of the underlying interactions between these quantum mechanical phenomena. This is done by combining resonant high-field terahertz (THz) spectroscopy with a suite of complementary experimental techniques, such as ultrafast second-harmonic generation (SHG) microscopy. By utilizing resonant THz excitation, we avoid incoherent scattering processes and prevent energy-loss due to parasitic heating. Our aim is to not only investigate but actively control and steer these quantum-mechanical excitations and lay the foundations for new quantum technologies and next‑generation materials science.
We use techniques such as THz time-domain spectroscopy, 2D-THz spectroscopy, X-ray diffraction, SHG microscopy and polarimetry and THz-pump SHG-probe microscopy at temperatures down to 2 Kelvin and magnetic fields up to 10 Tesla. These unique combinations of complementary methods allows us to study the whole range of quantum materials, rather than any specific subset. Quantum materials of particular recent interest are:
- Kitaev quantum spin liquids
- Weyl and Dirac semimetals
- Quantum-critical heavy-Fermion systems
- Topological Kondo insulators
- Optically switchable ferroelectrics
The Team
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Dr. Erik de Vos (Group Leader) -
Debankit Priyadarshi (PhD student) -
Zekai Chen (PhD Student)
Recent publications
16. Discovery of an intrinsic non-Hermitian phase transition in a bulk condensed-matter system, Jingwen Li, Michael Turaev, Masakazu Matsubara, Kristin Kliemt, Cornelius Krellner, Shovon Pal, Manfred Fiebig and Johann Kroha, external page Science (2026)
15. Missing spectral weight in a heavy-fermion system far above the Néel temperature, Jingwen Li, Debankit Priyadarshi, Chia-Jung Yang, Ulli Pohl, Oliver Stockert, Hilbert von Löhneysen, Shovon Pal, Manfred Fiebig and Johann Kroha, external page Physical Review B (2025)
14. Critical slowing down near a magnetic quantum phase transition with fermionic breakdown, Chia-Jung Yang, Kristin Kliemt, Cornelius Krellner, Johann Kroha, Manfred Fiebig, and Shovon Pal, external page Nature Physics (2023).
13. Terahertz control of many-body dynamics in quantum materials, Chia-Jung Yang, Jingwen Li, Manfred Fiebig, and Shovon Pal, external page Nature Reviews Materials (2023).
12. A perspective on nonlinearities in coherent magnetization dynamics, Jingwen Li, Chia-Jung Yang, Ritwik Mondal, Christian Tzschaschel and Shovon Pal, external page Applied Physics Letters 120, 050501 (2022).
11. Birefringence of orthorhombic DyScO3: Toward a terahertz quarter-wave plate, Chia-Jung Yang, Jingwen Li, Jannis Lehmann, Nives Strkalj, Morgan Trassin, Manfred Fiebig, and Shovon Pal, external page Applied Physics Letters 118, 223506 (2021).
10. Origin of Terahertz Soft-Mode Nonlinearities in Ferroelectric Perovskites, Shovon Pal, Nives Strkalj, Chia-Jung Yang, Mads C. Weber, Morgan Trassin, Michael Woerner, and Manfred Fiebig, external page Physical Review X 11, 021023 (2021).
9. Two-dimensional spectroscopy on a THz quantum cascade structure, Sergej Markmann, Martin Frankié, Shovon Pal, David Stark, Mattias Beck, Manfred Fiebig, Giacomo Scalari, and Jérôme Faist, external page Nanophotonics 10, 171 (2021).
8. Terahertz Conductivity of Heavy-fermion Systems from Time-resolved Spectroscopy, Chia-Jung Yang, Shovon Pal, Farzaneh Zamani, Kristin Kliemt, Cornelius Krellner, Oliver Stockert, Hilbert v Löhneysen, Johann Kroha, and Manfred Fiebig, external page Physical Review Research 2, 033296 (2020).
7. Efficient spin excitation via ultrafast damping-like torques in antiferromagnets, Christian Tzschaschel, Takuya Satoh, and Manfred Fiebig, external page Nature Communications 11, 6142 (2020).
6. Depolarizing-Field Effects in Epitaxial Capacitor Heterostructures, Nives Strkalj, Gabriele De Luca, Marco Campanini, Shovon Pal, Jakob Schaab, Chiara Gattinoni, Nicola A. Spaldin, Marta D. Rossell, Manfred Fiebig, and Morgan Trassin, external page Physical Review Letters 123, 147601 (2019).
5. Tracking the ultrafast motion of an antiferromagnetic order parameter, Christian Tzschaschel, Takuya Satoh, and Manfred Fiebig, external page Nature Communications 10, 3995 (2019).
4. Fermi Volume Evolution and Crystal-Field Excitations in Heavy-Fermion Compounds Probed by Time-Domain Terahertz Spectroscopy, Shovon Pal, Christoph Wetli, Farzaneh Zamani, Oliver Stockert, Hilbert v. Loehneysen, Manfred Fiebig, and Johann Kroha, external page Physical Review Letters 122, 096401 (2019).
3. Time-resolved collapse and revival of the Kondo state near a quantum phase transition, Christoph Wetli, Shovon Pal, Johann Kroha, Kristin Kliemt, Cornelius Krellner, Oliver Stockert, Hilbert v. Loehneysen, and Manfred Fiebig, external page Nature Physics 14, 1103 (2018).
2. Ultrafast optical excitation of coherent magnons in antiferromagnetic NiO, Christian Tzschaschel, Kensuke Otani, Ryugo Iida, Tsutomu Shimura, Hiroaki Ueda, Stefan Günther, Manfred Fiebig, and Takuya Satoh, external page Physical Review B 95, 174407 (2017).
1. Two-dimensional coherent spectroscopy of a THz quantum cascade laser: observation of multiple harmonics, Sergej Markmann, Hanond Nong, Shovon Pal, Tobias Fobbe, Negar Hekmat, Reshma A. Mohandas, Paul Dean, Lianhe Li, Edmund H. Linfield, A. Giles Davies, Andreas D. Wieck, and Nathan Jukam, external page Optics Express 25, 21753 (2017).