Dresden 2026 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 25: Focus Session: Chiral phonons and crystals coupled to magnetic order I
MA 25.3: Vortrag
Mittwoch, 11. März 2026, 10:30–10:45, HSZ/0002
Coherent Transfer of Pseudo- and Real Angular Momentum via Lattice Anharmonicity — •Olga Minakova1, Carolina Paiva2, Maximilian Frenzel1, Michael Spencer1, Joanna Urban1, Martin Wolf1, Dominik Juraschek2,3, and Sebastian Maehrlein1,4,5 — 1FHI Berlin — 2Tel Aviv U. — 3TU Eindhoven — 4HZDR — 5TU Dresden
Rotational symmetry in crystals enforces conservation of phonon pseudo-angular momentum. However, direct evidence for angular momentum transfer between phonon modes has been lacking. We demonstrate coherent angular momentum transfer between doubly degenerate phonons through a resonant three-phonon interaction [1]. Circularly polarized THz pulses drive an IR-active phonon in Bi2Se3, imprinting the helicity of the field and generating ionic loops possessing real angular momentum. Anharmonic coupling then upconverts two such IR phonons into a Raman-active phonon at twice the frequency, transferring energy, linear momentum, and angular momentum. The THz-driven Kerr effect directly resolves the Raman phonon trajectory, revealing a helicity reversal, which perfectly fulfills pseudo-angular momentum conservation in the discrete C3 rotational symmetry of the lattice. Group theory analysis and DFT confirm this helicity flip and simultaneously reveal transfer of real angular momentum as circular ionic motion. These results constitute the first direct experimental evidence of angular momentum conservation in phonon-phonon interactions.
[1] O. Minakova et. al., arXiv:2503.11626 (2025)
Keywords: Angular momentum; Lattice anharmonicity; THz spectroscopy