Nonreciprocity and High-Frequency Dynamics in Curved and Chiral Superconducting and Ferromagnetic Nanostructures

Lifting nanodevices from planar to three-dimensional architectures enables new functionalities by breaking symmetries and increasing device density. Two promising material classes for beyond-CMOS nanoscale technologies are superconductors and ferromagnets. Superconductors exhibit macroscopic quantum coherence, enabling dissipationless currents and making them attractive for ultrasensitive sensors and quantum computing. In ferromagnets, low-energy spin excitations, known as spin waves or magnons, propagate without Joule heating at GHz frequencies, making them promising information carriers. In this thesis, we employ three-dimensional time-dependent Ginzburg-Landau (TDGL) and micromagnetic simulations to investigate how curvature, chirality, and topology in three-dimensional nanostructures influence superconducting and magnonic excitations. First, we investigate curved tubular type-II superconductors with a constriction. 3D TDGL simulations show that, under a magnetic field along the tube axis, this geometry stabilizes rows of vortices and anti-vortices separated by the constriction. Under a dc transport current, these vortices move azimuthally. For sufficiently large currents, periodic phase slips are stabilized at the constriction, generating voltage pulses at GHz frequencies. We further show that adding a GHz ac modulation to the transport current induces frequency mixing between the phase-slip oscillation and the modulation frequency, resulting in a superconducting frequency comb. Second, we study the influence of a normal-metal coating on vortex statics and dynamics in superconductors with tilted interfaces. By modifying the TDGL equation to model proximity-induced superconductivity in the adjacent normal metal, we show that differences in material properties bend vortices at the interface, with an angular dependency analogous to optical refraction. We derive the corresponding refraction law and verify it numerically. Furthermore, the interface can partially trap vortices due to an energy barrier. The weakening of superconductivity induced by the normal-metal coating lowers the vortex-entry barrier and, under transport current, leads to increased vortex velocities. Third, we investigate the superconducting diode effect, i.e., different critical currents for opposite polarities, in a helical superconducting tube using 3D TDGL simulations. We demonstrate that this effect originates from an inhomogeneous distribution of field-induced screening supercurrents arising from the chiral geometry. The sign of the diode efficiency reverses upon reversing either the magnetic-field direction or the structural chirality, confirming the magnetochiral origin of the effect. We provide guidelines for optimizing the diode efficiency. Finally, we use semi-analytical theory and micromagnetic simulations to study a novel class of materials-by-design ferromagnets, which we term artificial chiral magnets: ferromagnetic nanotubes with imprinted helical surface topogra