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TT: Fachverband Tiefe Temperaturen

TT 84: Focus Session: Emerging Magnetic Phenomena from Chiral Phonons II (joint session MA/TT)

TT 84.6: Vortrag

Freitag, 22. März 2024, 10:45–11:00, H 1058

Ultrafast symmetry breaking with multicolor chiral phonons — •Omer Yaniv and Dominik Juraschek — Tel Aviv University, Tel Aviv, Israel

In the field of ultrafast dynamics, terahertz pulses stand out as powerful tools capable of initiating coherent vibrational motions in crystal lattices. Circularly or elliptically polarized pulses can excite chiral phonons, which are the collective vibrational patterns of circular or elliptical orbital motions of atoms around their equilibrium lattice positions. Such phonons carry angular momentum and are able to generate magnetic fields leading to a varying range of phenomena. Our study explores the coherent driving of chiral phonons using multicolor laser pulses. Such driving allows us to generate different types of magnetic patterns. We focus on IR-active optical degenerate phonons in CsPbF3 with frequencies at 1.8 THz and 3.6 THz and look at three different features of this multicolor phonon driving. We dynamically induce inversion symmetry breaking in the centrosymmetric lattice structure. This can give rise to nonlinear phenomena, such as second harmonic generation (SHG). Additionally, we show the generation of atomic eight-curve motion, which leads to the generation of spatially distinct alternating phononic angular momentum. This gives rise to an antiferromagnetic pattern of the dynamical phonon magnetic moment. Furthermore, our findings indicate that coherent excitation can lead to the formation of new symmetries, such as a 3-fold rotation, arising from atomic cloverleaf motion. We expect our predictions to be realizable with state-of-the-art pulse shaping techniques.