Coherent control of collective nuclear quantum states via transient magnons

Ultrafast and precise control of quantum systems at x-ray energies involves photons with oscillation periods below 1 as. Coherent dynamic control of quantum systems at these energies is one of the major challenges in hard x-ray quantum optics. Here, we demonstrate that the phase of a quantum system embedded in a solid can be coherently controlled via a quasi-particle with subattosecond accuracy. In particular, we tune the quantum phase of a collectively excited nuclear state via transient magnons with a precision of 1 zs and a timing stability below 50 ys. These small temporal shifts are monitored interferometrically via quantum beats between different hyperfine-split levels. The experiment demonstrates zeptosecond interferometry and shows that transient quasi-particles enable accurate control of quantum systems embedded in condensed matter environments

Simultaneous control of magnetic topologies for reconfigurable vortex arrays

The topological spin textures in magnetic vortices in confined magnetic elements offer a platform for understanding the fundamental physics of nanoscale spin behavior and the potential of harnessing their unique spin structures for advanced magnetic technologies. For magnetic vortices to be practical, an effective reconfigurability of the two topologies of magnetic vortices, that is, the circularity and the polarity, is an essential prerequisite. The reconfiguration issue is highly relevant to the question of whether both circularity and polarity are reliably and efficiently controllable. In this work, we report the first direct observation of simultaneous control of both circularity and polarity by the sole application of an in-plane magnetic field to arrays of asymmetrically shaped permalloy disks. Our investigation demonstrates that a high degree of reliability for control of both topologies can be achieved by tailoring the geometry of the disk arrays. We also propose a new approach to control the vortex structures by manipulating the effect of the stray field on the dynamics of vortex creation. The current study is expected to facilitate complete and effective reconfiguration of magnetic vortex structures, thereby enhancing the prospects for technological applications of magnetic vortices.ope

Bail-In from an Insolvency Law Perspective

Coherent privaatrech

Magnetic Vortices

Magnetic vortices are topological objects found in magnetic thin films and microstructures. The study of vortices has attracted much attention for their fundamental beauty and because vortices could be constituents of non-volatile storage and sensing devices as well as of radiofrequency and neuro-inspired devices. Many important experimental, theoretical, and simulational contributions have been made to understand the intricate details of the statics and dynamics of magnetic vortices. In this chapter we start from first experimental observations and proceed to the occurence of vortices, their static properties as well as their topology. The polarization of vortex cores and the circularity of their in-plane magnetization are introduced. The minimization of micromagnetic energy contributions that lead to an out-of-plane core region and an in-plane circulation of magnetization are discussed, along with geometries for confinement and their response in static external magnetic fields. We analyze stray fields in the vicinity of a vortex, their hysteresis as well as their thermal stability before we address dynamic properties. The relation between handedness and sense of gyration are described and the harmonic oscillator model for small excitations is introduced. Then modifications of the oscillator model for strong excitations including nonlinearities are mentioned. We proceed to the core switching process that includes the creation, annihilation, and fusion of vortices and their topological counterpart the antivortex. Harmonic and pulsed excitations with fields and currents are discussed as well as the interaction of coupled vortices, where a vortex can be considered as a building block, for linear chains, vortex molecules and magnonic vortex crystals. The chapter concludes with current perspectives and challenges in the field of magnetic vortices

Band structure engineering of two dimensional magnonic vortex crystals

Magnonic vortex crystals are studied via scanning transmission x-ray microscopy and ferromagnetic-resonance spectroscopy. We investigate a two-dimensional vortex crystal by imprinting waves with tunable wave vectors. The dispersion relation ω(k) is determined via ferromagnetic-resonance spectroscopy with a tunable frequency and wave vector for two vortex core polarization patterns that are adjusted by self-organized state formation prior to the measurement. We demonstrate that the band structure of the crystal is reprogrammed by tuning the vortex polarizations

Incoherent Nuclear Resonant Scattering from a Standing Spin Wave

We introduce a method to study the spatial profiles of standing spin waves in ferromagnetic microstructures. The method relies on Nuclear Resonant Scattering of 57Fe using a microfocused beam of synchrotron radiation, the transverse coherence length of which is smaller than the length scale of lateral variations in the magnetization dynamics. Using this experimental method, the nuclear resonant scattering signal due to a confined spin wave is determined on the basis of an incoherent superposition model. From the fits of the Nuclear Resonant Scattering time spectra, the precessional amplitude profile across the stripe predicted by an analytical model is reconstructed. Our results pave the way for studying non-homogeneous dynamic spin configurations in microstructured magnetic systems using nuclear resonant scattering of synchrotron light