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MA: Fachverband Magnetismus
MA 10: Focus Session: Magnetic Phenomena from Phonon Chirality and Angular Momentum II (joint session MA/TT)
MA 10.7: Talk
Tuesday, March 18, 2025, 11:15–11:30, H16
Modeling of the preparation and conservation of coherent phonon (pseudo) angular momentum — •Olga Minakova1, Maximilian Frenzel1, Carolina Paiva2, Joanna M. Urban1, Michael S. Spencer1, Martin Wolf1, Dominik M. Juraschek2,3, and Sebastian F. Maehrlein1,4,5 — 1FHI Berlin — 2Tel Aviv University — 3Eindhoven University of Technology — 4HZDR — 5TU Dresden
The angular momentum of lattice vibrations - phonon angular momentum - is an underexplored degree of freedom in solid-state systems. Recent experiments have shown that circularly-polarized THz pulses can coherently excite degenerate phonon modes, enabling the preparation of phonon angular momentum states. THz-Kerr effect spectroscopy provides a means to monitor these states by directly measuring vectorial phonon trajectories. To interpret such experiments, it is essential to understand the symmetry properties of the phonon modes that influence the driving and probing processes, as well as the conservation of angular momentum in the crystal lattice. Here, we model the generation and detection of coherent phonon angular momentum, revealing how crystal symmetry dictates the selection rules in the lattice. We show that the form of the Raman tensors associated with the phonon explains the phonon helicity observed in experiments, linking the discrete rotational symmetry of the material to the conservation of pseudo angular momentum in lattice vibrations.
Keywords: Phonon angular momentum; Raman tensor; THz; Symmetry