Dresden 2026 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 54: 2D Materials IX – Photonic properties and devices
HL 54.2: Vortrag
Freitag, 13. März 2026, 09:45–10:00, POT/0081
Measurement of optically induced broken time-reversal symmetry in atomically thin crystals — •Florentine Friedrich1, Paul Herrmann1, Shridhar Shanbhag2, Sebastian Klimmer1, Jan Wilhelm2, and Giancarlo Soavi1 — 1Institute of Solid State Physics, University of Jena, Germany — 2Institute of Theoretical Physics and Regensburg Center for Ultrafast Nanoscopy (RUN), University of Regensburg, Germany
Time-reversal symmetry (TRS) and space-inversion symmetry (SIS) are fundamental properties underlying phenomena like magnetism and non-trivial spin textures in crystals. Transition Metal Dichalcogenides (TMDs) offer a tunable platform to study the interplay of these symmetries, which can be engineered by tuning the number of layers and via all-optical bandgap modulation.
We propose a powerful, all-optical approach using third harmonic (TH) Faraday rotation to probe broken TRS, regardless of the SIS [1]. By exciting mono- and bilayer TMDs with elliptically polarized light, we achieve spin-selective bandgap modulation, consequently breaking TRS. This symmetry reduction modifies the nonlinear susceptibility tensor, causing a measurable rotation of the emitted TH polarization. Our experimental results are supported by analytical theory for both mono- and bilayer TMDs and provide a unique tool to investigate spin, valley, and layer coupling in atomically thin semiconductors, thereby contributing to the understanding of the relation between crystal symmetries and the nonlinear optical response of a material.
[1] Friedrich et al., Nat. Photon., 10.1038/s41566-025-01801-2 (2025).
Keywords: Symmetry Breaking; Transition Metal Dichalcogenide; Nonlinear Optics