Berlin 2024 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 50: Focus Session: Emerging Magnetic Phenomena from Chiral Phonons II (joint session MA/TT)

MA 50.4: Vortrag

Freitag, 22. März 2024, 10:15–10:30, H 1058

Creating and observing elliptically polarized coherent optical shear phonons in graphite — Arne Ungeheuer, Mashood T. Mir, Ahmed S. Hassanien, Lukas Nöding, Thomas Baumert, and •Arne Senftleben — Institut für Physik, Universität Kassel

We present a scheme to create circularly or elliptically polarized coherent phonons of the degenerate inter-layer shear mode in graphite. The approach utilizes the time-delayed excitation of two coherent phonons linearly polarized in perpendicular directions by femtosecond laser pulses. We observe the resulting elliptically polarized coherent phonon using ultrafast electron diffraction [1], where they create a unique signature that allows us to determine the phonon’s ellipticity and sense of rotation. Analyzing the atomic motion in the crystal, we find that the atoms in adjacent layers circulate in the same direction in a Hula hoop fashion. In magnetic materials, such elliptically polarized phonons can create a transient magnetization in an atomistic version of the Barnett effect [2].

[1] C. Gerbig, et al. New J. Phys. 17, 043050 (2015).
[2] T. F. Nova, et al. Nature Phys. 13, 132–136 (2017).

Keywords: chiral phonons; coherent phonons; ultrafast electron diffraction; graphite