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TT: Fachverband Tiefe Temperaturen
TT 84: Focus Session: Emerging Magnetic Phenomena from Chiral Phonons II (joint session MA/TT)
TT 84.3: Talk
Friday, March 22, 2024, 10:00–10:15, H 1058
Phonon inverse Faraday effect — •Natalia Shabala and R. Matthias Geilhufe — Department of Physics, Chalmers University of Technology, 412 96 Göteborg, Sweden
Dynamical multiferroicity refers to magnetization of a material caused by a temporally varying polarization [1]. Such phenomena can be light-induced. For example, Kerr-effect measurements on THz-pumped SrTiO3 (STO) reveal significant magnetic moments in the sample of about 0.1 Bohr magneton per unit cell, while SrTiO3 itself is nonmagnetic [2]. Moreover, this value is significantly larger than the one expected from a circularly moving charge argument. We attempt to understand this discrepancy by finding a connection between magnetization resulting from optically driven chiral phonons and Berry connection. By extending the formalism of inverse Faraday effect to phonons and applying modern theory of polarization, we hope to develop a better understanding of the large difference between theoretical and experimental values of light induced magnetization. In the prospect of “phonon-enabled technology”, we apply our formalism to investigate a Hall effect in graphene/STO, mediated by light-induced chiral phonons in the STO substrate. We find that a laser field strength of 0.1 MV/m and a current of 1 mA will cause a transverse electric field of about 40 nV, which can be measured in state-of-the-art experiments.
[1] D. M. Juraschek et al., ”Dynamical multiferroicity”, Phys. Rev. Mater., 1.1 (2017): 014401
[2] M. Basini et al., ”Terahertz electric-field driven dynamical multiferroicity in SrTiO3”, arXiv preprint arXiv:2210.01690 (2022)