Physikalische Chemie - Direktor: Prof. Dr. Martin Wolf
Department Seminar
Host: Sebastian Mährlein

Monday, April 15, 2024, 11:00 am
All are invited to meet around 10:40 am for a chat with coffee & cookies.
PC Seminar Room, G 2.06, Faradayweg 4
Dr. Arne Senftleben
Universität Kassel
Controlling and Observing Coherent Phonons in Thin van der Waals Materials
Ultrashort laser pulses can induce coherent phonons, where all atoms in the crystal oscillate in phase. Using ultrafast electron diffraction, we can directly image this joint atomic motion in the time domain. In my talk, I will cover recent experimental observations on coherent acoustic and optical phonons. We observe coherent acoustic phonons in the breathing mode of layered van der Waals materials such as graphite. There, we introduced a control scheme to selectively excite harmonic frequencies of this mode. In addition, I will show coherent breathing mode phonons in a heterostructure composed of graphite and hexagonal boron nitride. For the coherent optical phonons, I will focus on the shear mode of graphite. We have investigated how linearly polarized laser pulses induce an effective polarization in the degenerate phonon mode. With this knowledge, we could create and observe elliptically polarized coherent shear phonons with a double-pulse excitation scheme. This scheme should generally apply to induce elliptically or circularly polarized coherent phonons in various crystals.