Year: 2025
Type: article
Abstract: Time-reversal and space-inversion symmetries are fundamental properties of crystals and play a role in underlying phenomena such as magnetism, topology and non-trivial spin textures. Transition metal dichalcogenides (TMDs) represent an excellent tunable model system to explore the interplay between these symmetries as they can be engineered on demand by tuning the number of layers and via all-optical bandgap modulation. In this work, we modulate and study time-reversal symmetry in mono- and bilayer TMDs with all-optical methods using third-harmonic Faraday rotation. We excite the samples using elliptically polarized light, achieve spin-selective bandgap modulation and consequent breaking of time-reversal symmetry. The reduced symmetry modifies the nonlinear susceptibility tensor, causing a rotation of the emitted third-harmonic polarization. With this method, we probe broken time-reversal symmetry in both non-centrosymmetric (monolayer) and centrosymmetric (bilayer) WS 2 crystals. Furthermore, we discuss how the detected third-harmonic rotation angle directly links to spin-valley locking in monolayer TMDs and spin-valley-layer locking in bilayer TMDs. Our results show a powerful approach to study broken time-reversal symmetry in crystals regardless of space-inversion symmetry, and shed light on the spin, valley and layer coupling of atomically thin semiconductors.
Source: Nature Photonics
Authors: Florentine Friedrich, Paul Herrmann, Shridhar Sanjay Shanbhag, Sebastian Klimmer, Jan Wilhelm, Giancarlo Soavi
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $12,690
Awards: GRK 2675: Maßgeschneiderte Metaoberflächen – Erzeugung, Programmierung und Detektion von Licht, SFB 1375: Nichtlineare Optik bis hin zu atomaren Skalen, G2280780808, G3281482588, G3392515402, G3420992565, G3573082562, G390482800, Quantensimulationen ultraschneller Exzitonendynamik mit atomarer Auflösung, G7829377431, Verbundprojekt: Silizium-/Siliziumnitridintegrierte verschränkte Strahlungsquellen - SINNER -, SFB 1277: Emergente relativistische Effekte in der Kondensierten Materie: Von grundlegenden Aspekten zu elektronischer Funktionalität, GRK 2905: Ultraschnelle Nanoskopie: von EinteilchenDynamik zu kooperativen Prozessen
OpenAlex ID: W4416230831