Regensburg 2025 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 13: Focus Session: Magnetic Phenomena from Phonon Chirality and Angular Momentum II (joint session MA/TT)

TT 13.9: Talk

Tuesday, March 18, 2025, 11:45–12:00, H16

Ultrafast generation of multicolor chiral phonons in magnetic and ferroelectric materials — •Omer Yaniv¹ and Dominik M. Juraschek² — ¹Tel Aviv University, Tel Aviv, Israel — ²Eindhoven University of Technology, Eindhoven, Netherlands

Terahertz pulses are powerful tools capable of initiating coherent vibrational motions in solids. Circularly polarized pulses can further excite chiral phonons. Such phonons carry an angular momentum and are able to generate magnetic moments leading to a varying range of phenomena, including the phonon Hall, phonon Zeeman, and phonon inverse Faraday effects. Our study investigates the coherent driving of phonons using multicolor laser pulses, leading to Lissajous trajectories of the atoms. We demonstrate the generation of such multicolor chiral phonons in BaTiO3, a task that presents significant challenges due to the requirement of an exact 1:2 phonon frequency ratio. Achieving this precise ratio is crucial for the generation of closed atomic Lissajous loops. However, we overcome this challenge by creating phonon polaritons with shifted frequencies through the use of optical cavities. This approach allows us to surpass the limitations imposed by the strict phonon frequency ratio. By carefully tuning the cavity parameters, we demonstrate a new pathway for controlling lattice vibrations at ultrafast timescales. We also explore how multicolor phonons tune magnetic properties in monolayer CrI3, a 2D material with strong spin-orbit coupling and ferromagnetism. By manipulating phonon dynamics, we examine the interaction between lattice vibrations and magnetic order.