Flavio Garcia : Geometry as a Control Knob: From Spin-to-Charge Conversion in 2D Materials to Skyrmions in Curved Nanomagnets

At reduced dimensions, geometry can become an active parameter for controlling spin transport and magnetic textures. In this seminar, I will discuss two research lines developed around this idea. The first concerns spin-to-charge conversion in heterostructures combining yttrium iron garnet (YIG) with two-dimensional transition-metal dichalcogenides. Starting from the reproducible growth of low-damping YIG films and the development of an automated mechanical exfoliation method, I will show how experiments on triangular monolayer MoS₂ flakes reveal competing contributions from semiconducting interior states and metallic zigzag-edge states. Their relative weights can be disentangled through the area-to-perimeter ratio and controlled by optical excitation, enabling the conversion signal to be enhanced, attenuated, or switched off. The second research line follows the development of curved magnetic nanostructures, from vortex states in three-dimensional nanocaps to curved Pt/Co/Pt nanomagnets. In these systems, curvature breaks structural symmetry and induces an interfacial Dzyaloshinskii–Moriya interaction. Density-functional calculations, micromagnetic simulations, magnetic force microscopy, and electron holography demonstrate the stabilization of skyrmions and skyrmioniums at room temperature and zero applied magnetic field. Together, these results establish geometry—from monolayer boundaries to magnetic-film curvature—as a versatile tool for engineering angular-momentum conversion and topological magnetic textures.