Regensburg 2025 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 99: Ultrafast Electron Dynamics IV
O 99.1: Vortrag
Freitag, 21. März 2025, 10:30–10:45, H11
Large-amplitude coherent phonon dynamics in a van der Waals ferroelectric — •Jan Gerrit Horstmann1, Quintin Meier2, Thomas Lottermoser1, and Manfred Fiebig1 — 1Dept. of Materials, ETH Zurich, Switzerland — 2Institut Néel, CNRS UPR2940, Grenoble, France
We explore the all-optical control of coherent phonon dynamics in the van der Waals ferroelectric WTe2. Double-pulse optical excitation is harnessed to enhance the amplitude of the prominent interlayer shear mode beyond the limit of single-pulse excitation, with the resulting structural dynamics monitored via time-resolved second harmonic generation. A strong correlation between shear phonon amplitude and damping suggests higher-order coupling to lower-lying modes. At largest initial phonon amplitudes, Fourier transforms of the delay-dependent SHG traces reveal a frequency contribution at twice the shear-mode frequency. We discuss second-harmonic phonon generation and ultrafast phononic modulation of the nonlinear susceptibility as potential underlying mechanisms. Coherent vibrational control over relaxation pathways and electronic properties of ferroic van der Waals materials could enable novel types of devices for energy-efficient electronics.
Keywords: Ultrafast structural dynamics; Ferroics; Van der Waals material; Coherent phonon; Second harmonic generation