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TT: Fachverband Tiefe Temperaturen

TT 1: Focus Session: Magnetic Phenomena from Phonon Chirality and Angular Momentum I (joint session MA/TT)

TT 1.8: Vortrag

Montag, 17. März 2025, 12:45–13:00, H20

Elliptically polarized coherent phonons in a degenerate mode — Arne Ungeheuer, Mashood T. Mir, Ahmed Hassanien, Lukas Nöding, Thomas Baumert, and •Arne Senftleben — Institut für Physik, Universität Kassel

Controlled excitation of phonons in crystalline solids is an emerging way to alter the property of a material to create phenomena such as transient magnetic polarization [1,2]. Here, we want to focus on controlling the polarization properties of coherent optical phonons that can be launched by ultrashort laser pulses. we demonstrate the excitation of elliptically polarized coherent optical phonons of the E_2g shearing mode in graphite. This is achieved by exciting the superposition of two orthogonally polarized phonon modes using a tailored pair of time-delayed optical pulses with tilted polarization. The elliptically polarized coherent phonons are detected by ultrafast electron diffraction [3], where we determine the amount of ellipticity and the sense of rotation.
[1] D. M. Juraschek, et al. Phys. Rev. Lett. 118, 054101 (2017).
[2] A. S. Disa, et al. Nature Phys. 16, 937–941 (2018).
[3] C. Gerbig, et al. New J. Phys. 17, 043050 (2015).

Keywords: chiral phonons; graphite; ultrafast electron diffraction