Controlling Magneto-Optical Properties in Layered Crystals via Voltage-Controlled Molecular Intercalation

• Applicant: Dr. Kevin Synnatschke
• Subject Area: Physical Chemistry of Solids and Surfaces, Material Characterisation
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 566939844

The proposed research project investigates new, fundamental aspects of cathodic intercalation chemistry in micromechanically exfoliated van der Waals (vdW) materials. The aim is to precisely control their electronic, optical, and magnetic properties by intercalating organic molecules (cations) into the vdW gaps of designated model materials. This approach systematically weakens interlayer interactions, enabling the structural, electronic, and optical properties of these materials to be tailored without compromising their integrity. The project initially focuses on tungsten-based transition metal dichalcogenides (TMDs) such as WS₂, WSe₂, and WTe₂, which represent an ideal model platform due to their strong spin-orbit coupling, chemical versatility, and structural stability. Mulilayered micromechanically cleaved nanomaterials will be used as starting materials, as they allow for the precise study of intercalation processes on a single flake basis. The goal is to investigate effects such as electronic decoupling, chemically induced quantum effects, and intercalation-driven symmetry changes and to systematically adjust these through chemical modifications of the intercalated guest molecules. In addition, the optical properties of these materials will be studied and tailored by intercalating optically active molecules, such as perylene-based or dynamically isomerizable compounds. This includes the modulation of photoluminescence, the investigation of exciton dynamics, and light-matter coupling. Following comprehension of intercalation chemistry in TMDs, experiments will be extended to antiferromagnetic vdW materials, including metal thiophosphates (FePS₃, NiPS₃, MnPS₃) and CrSBr. This material platform is particularly suitable for manipulating magnetic phases, such as antiferromagnetic and ferromagnetic couplings, via intercalation. CrSBr is of special interest due to its unique combination of optical and magnetic transitions, which can potentially be significantly influenced through intercalation. Finally, more complex heterostructures combining TMDs with magnetic vdW materials will be studied. These systems enable the analysis and targeted modification of coupled optical and magnetic properties via intercalation. Exploring systems of increasing complexity, including combinations of TMDs with thiophosphates or CrSBr, forms a promising basis for designing future functional materials. The project integrates advanced nanomaterial synthesis, precise electrochemical techniques, and modern characterization methods such as Raman spectroscopy, magneto-optics, and electron microscopy. The aim is to develop a deep understanding of intercalation chemistry and its impact on symmetry changes, with a focus on dynamically tunable properties to fabricate novel functional materials for applications in optoelectronics, spintronics, and quantum technologies.

• DFG Programme: Emmy Noether Independent Junior Research Groups