Strongly enhanced shift current at exciton resonances in a noncentrosymmetric wide-gap semiconductor.

Excitons are fundamental quasiparticles that are ubiquitous in photoexcited semiconductors and insulators. Despite causing a sharp and strong photoabsorption near the interband absorption edge, charge-neutral excitons do not yield photocurrent in conventional photovoltaic processes unless dissociated into free charge carriers. Here, we experimentally demonstrate that excitons can directly contribute to photocurrent generation through a nonlinear light-matter interaction in a noncentrosymmetric semiconductor CuI.

Confined antiskyrmion motion driven by electric current excitations.

Current-driven dynamics of topological spin textures, such as skyrmions and antiskyrmions, have garnered considerable attention in condensed matter physics and spintronics. As compared with skyrmions, the current-driven dynamics of their antiparticles - antiskyrmions - remain less explored due to the increased complexity of antiskyrmions. Here, we design and employ fabricated microdevices of a prototypical antiskyrmion host, (FeNiPd)P, to allow in situ current application with Lorentz transmission electron microscopy observations.

Influence of Magnetic Sublattice Ordering on Skyrmion Bubble Stability in 2D Magnet FeGeTe.

The realization of above room-temperature ferromagnetism in the two-dimensional (2D) magnet FeGeTe represents a major advance for the use of van der Waals (vdW) materials in practical spintronic applications. In particular, observations of magnetic skyrmions and related states within exfoliated flakes of this material provide a pathway to the fine-tuning of topological spin textures via 2D material heterostructure engineering. However, there are conflicting reports as to the nature of the magnetic structures in FeGeTe.

Electron holography observation of individual ferrimagnetic lattice planes.

Atomic-scale observations of a specific local area would be considerably beneficial when exploring new fundamental materials and devices. The development of hardware-type aberration correction in electron microscopy has enabled local structural observations with atomic resolution as well as chemical and vibration analysis. In magnetic imaging, however, atomic-level spin configurations are analysed by electron energy-loss spectroscopy by placing samples in strong magnetic fields, which destroy the nature of the magnetic ordering in the samples.

Enhanced emergent electromagnetic inductance in TbSb due to highly disordered helimagnetism.

In helimagnetic metals, ac current-driven spin motions can generate emergent electric fields acting on conduction electrons, leading to emergent electromagnetic induction (EEMI). Recent experiments reveal the EEMI signal generally shows a strongly current-nonlinear response. In this study, we investigate the EEMI of TbSb, a short-period helimagnet.

Bloch Point Quadrupole Constituting Hybrid Topological Strings Revealed with Electron Holographic Vector Field Tomography.

Topological magnetic (anti)skyrmions are robust string-like objects heralded as potential components in next-generation topological spintronics devices due to their low-energy manipulability via stimuli such as magnetic fields, heat, and electric/thermal current. While these 2D topological objects are widely studied, intrinsically 3D electron-spin real-space topology remains less explored despite its prevalence in bulky magnets. 2D-imaging studies reveal peculiar vortex-like contrast in the core regions of spin textures present in antiskyrmion-hosting thin plate magnets with S crystal symmetry, suggesting a more complex 3D real-space structure than the 2D model suggests.

Heat current-driven topological spin texture transformations and helical q-vector switching.

The use of magnetic states in memory devices has a history dating back decades, and the experimental discovery of magnetic skyrmions and subsequent demonstrations of their control via magnetic fields, heat, and electric/thermal currents have ushered in a new era for spintronics research and development. Recent studies have experimentally discovered the antiskyrmion, the skyrmion's antiparticle, and while several host materials have been identified, control via thermal current remains elusive. In this work, we use thermal current to drive the transformation between skyrmions, antiskyrmions and non-topological bubbles, as well as the switching of helical states in the antiskyrmion-hosting ferromagnet (FeNiPd)P at room temperature.

Spontaneous Vortex-Antivortex Pairs and Their Topological Transitions in a Chiral-Lattice Magnet.

The spontaneous formation and topological transitions of vortex-antivortex pairs have implications for a broad range of emergent phenomena, for example, from superconductivity to quantum computing. Unlike magnets exhibiting collinear spin textures, helimagnets with noncollinear spin textures provide unique opportunities to manipulate topological forms such as (anti)merons and (anti)skyrmions. However, it is challenging to achieve multiple topological states and their interconversion in a single helimagnet due to the topological protection for each state.

Realization and Current-Driven Dynamics of Fractional Hopfions and Their Ensembles in a Helimagnet FeGe.

3D topological spin textures-hopfions-are predicted in helimagnetic systems but are not experimentally confirmed thus far. By utilizing an external magnetic field and electric current in the present study, 3D topological spin textures are realized, including fractional hopfions with nonzero topological index, in a skyrmion-hosting helimagnet FeGe. Microsecond current pulses are employed to control the dynamics of the expansion and contraction of a bundle composed of a skyrmion and a fractional hopfion, as well as its current-driven Hall motion.

Seeding and Emergence of Composite Skyrmions in a van der Waals Magnet.

Topological charge plays a significant role in a range of physical systems. In particular, observations of real-space topological objects in magnetic materials have been largely limited to skyrmions - states with a unitary topological charge. Recently, more exotic states with varying topology, such as antiskyrmions, merons, or bimerons and 3D states such as skyrmion strings, chiral bobbers, and hopfions, have been experimentally reported.

Real-Space Observations of Three-Dimensional Antiskyrmions and Skyrmion Strings.

Nanometric topological spin textures, such as skyrmions (Sks) and antiskyrmions (antiSks), have attracted much attention recently. However, most studies have focused on two-dimensional spin textures in films with inherent or synthetic antisymmetric spin-exchange interaction, termed Dzyaloshinskii-Moriya interaction, although three-dimensional (3D) topological spin textures, such as antiSks composed of alternating Bloch- and Néel-type spin spirals, chiral bobbers carrying emergent magnetic monopoles, and deformed Sk strings, are ubiquitous. To elucidate these textures, we have developed a 3D nanometric magnetic imaging technique, tomographic Lorentz transmission electron microscopy (TEM).

Real-space determination of the isolated magnetic skyrmion deformation under electric current flow.

The manipulation and control of electron spins, the fundamental building blocks of magnetic domains and spin textures, are at the core of spintronics. Of particular interest is the effect of the electric current on topological magnetic skyrmions, such as the current-induced deformation of isolated skyrmions. The deformation has consequences ranging from perturbed dynamics to modified packing configurations.

Formation and Control of Zero-Field Antiskyrmions in Confining Geometries.

Magnetic skyrmions and antiskyrmions have attracted much interest owing to their topological features and spintronic functionalities. In contrast to skyrmions, the generation of antiskyrmions relies on tunning both the magnitude and direction of the external magnetic field. Here, it is reported that antiskyrmions can be efficiently created via quenching and robustly persist at zero field in the Fe Ni Pd P magnet with the S -symmetry.

Geometrically stabilized skyrmionic vortex in FeGe tetrahedral nanoparticles.

The concept of topology has dramatically expanded the research landscape of magnetism, leading to the discovery of numerous magnetic textures with intriguing topological properties. A magnetic skyrmion is an emergent topological magnetic texture with a string-like structure in three dimensions and a disk-like structure in one and two dimensions. Skyrmions in zero dimensions have remained elusive due to challenges from many competing orders.

Doping Control of Magnetic Anisotropy for Stable Antiskyrmion Formation in Schreibersite (Fe,Ni) P with S symmetry.

Magnetic skyrmions, vortex-like topological spin textures, have attracted much interest in a wide range of research fields from fundamental physics to spintronics applications. Recently, growing attention is also paid to antiskyrmions emerging with opposite topological charge in non-centrosymmetric magnets with D or S symmetry. In these magnets, complex interplay among anisotropic Dzyaloshinskii-Moriya interaction, uniaxial magnetic anisotropy, and magnetic dipolar interactions generates various magnetic textures.

Dynamic transition of current-driven single-skyrmion motion in a room-temperature chiral-lattice magnet.

Driving and controlling single-skyrmion motion promises skyrmion-based spintronic applications. Recently progress has been made in moving skyrmionic bubbles in thin-film heterostructures and low-temperature chiral skyrmions in the FeGe helimagnet by electric current. Here, we report the motion tracking and control of a single skyrmion at room temperature in the chiral-lattice magnet CoZnMn using nanosecond current pulses.

Real-space observations of 60-nm skyrmion dynamics in an insulating magnet under low heat flow.

Thermal-current induced electron and spin dynamics in solids -dubbed "caloritronics"- have generated widespread interest in both fundamental physics and spintronics applications. Here, we examine the dynamics of nanometric topological spin textures, skyrmions driven by a temperature gradient ∇T or heat flow, that are evaluated through in-situ real-space observations in an insulating helimagnet CuOSeO. We observe increases of the skyrmion velocity and the Hall angle with increasing ∇T above a critical value of ~ 13 mK/mm, which is two orders of magnitude lower than the ∇T required to drive ferromagnetic domain walls.

Application effect of tirofiban on percutaneous coronary intervention in patients with acute coronary syndrome and its postoperative effect on C-X-C motif chemokine ligand 16 level and myocardial perfusion.

This study aimed to investigate the application effect of tirofiban on percutaneous coronary intervention (PCI) in patients with acute coronary syndrome (ACS) and its postoperative effect on C-X-C motif chemokine ligand 16 (CXCL16) level and myocardial perfusion. A total of 50 cases of patients diagnosed with acute coronary syndrome and treated in Sunshine Union Hospital (Weifang, China) were included in group A and 30 cases of healthy subjects underwent physical examination in our hospital during the same period were enrolled in group B. Tirofiban was used in group A patients during PCI.

Nano-to-micro spatiotemporal imaging of magnetic skyrmion's life cycle.

Magnetic skyrmions are self-organized topological spin textures that behave like particles. Because of their fast creation and typically long lifetime, experimental verification of skyrmion's creation/annihilation processes has been challenging. Here, we successfully track skyrmion dynamics in defect-introduced CoZnMn by using pump-probe Lorentz transmission electron microscope.

Room-temperature antiskyrmions and sawtooth surface textures in a non-centrosymmetric magnet with S symmetry.

Topological spin textures have attracted much attention both for fundamental physics and spintronics applications. Among them, antiskyrmions possess a unique spin configuration with Bloch-type and Néel-type domain walls owing to anisotropic Dzyaloshinskii-Moriya interaction in the non-centrosymmetric crystal structure. However, antiskyrmions have thus far only been observed in a few Heusler compounds with D symmetry.

Giant anomalous Hall effect from spin-chirality scattering in a chiral magnet.

The electrical Hall effect can be significantly enhanced through the interplay of the conduction electrons with magnetism, which is known as the anomalous Hall effect (AHE). Whereas the mechanism related to band topology has been intensively studied towards energy efficient electronics, those related to electron scattering have received limited attention. Here we report the observation of giant AHE of electron-scattering origin in a chiral magnet MnGe thin film.

Bloch Lines Constituting Antiskyrmions Captured via Differential Phase Contrast.

Much scientific capital has been directed toward exotic magnetic spin textures called Bloch lines, that is, Néel-type line boundaries within domain walls, because their geometry promises high-density magnetic storage. While predicted to arise in high-anisotropy magnets, bulk soft magnets, and thin films with in-plane magnetization, Bloch lines also constitute magnetic antiskyrmions, that is, topological antiparticles of skyrmions. Most domain walls occur as Bloch-type or Néel-type, in which the magnetization rotates parallel or perpendicular to the domain wall across its profile, respectively.

Real-Space Observation of Topological Defects in Extended Skyrmion-Strings.

Exotic topological spin textures such as emergent magnetic monopole/anti-monopoles (hedgehog/anti-hedgehog) in the metastable extended skyrmion-strings attract much attention to the fundamental physics owing to their novel electromagnetic properties. However, the direct imaging of such spin textures is lacking. Here, we report the real-space observation of emergent magnetic monopoles involved in extended skyrmion-strings by Lorentz transmission electron microscopy (TEM) in combination with micromagnetic simulations.

Nanometric square skyrmion lattice in a centrosymmetric tetragonal magnet.

Magnetic skyrmions are topologically stable spin swirls with a particle-like character and are potentially suitable for the design of high-density information bits. Although most known skyrmion systems arise in non-centrosymmetric systems with a Dzyaloshinskii-Moriya interaction, centrosymmetric magnets with a triangular lattice can also give rise to skyrmion formation, with a geometrically frustrated lattice being considered essential in this case. Until now, it remains an open question if skyrmions can also exist in the absence of both geometrically frustrated lattice and inversion symmetry breaking.

Controlled transformation of skyrmions and antiskyrmions in a non-centrosymmetric magnet.

Control of topological spin textures in magnetic systems may enable future spintronic applications. Magnetic field pulses can switch the vortex polarity or the winding number of magnetic bubbles. Thermal energy can reverse the helicity of skyrmions and induce the transformation between meron and skyrmion by modifying the in-plane anisotropy.