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An asymmetric plasmonic nanoantenna featuring a double resonant mode that overlaps with both the excitation fundamental wavelength and the second harmonic emission displays a remarkably large nonlinear coefficient for second harmonic generation. Boosting nonlinear frequency conversion in extremely confined volumes remains a challenge in nano-optics research 1 , but can enable applications in nanomedicine 2 , photocatalysis 3 and background-free biosensing 4 . To obtain brighter nonlinear nanoscale sources, approaches that enhance the electromagnetic field intensity and counter the lack of phase matching in nanoplasmonic systems are often employed 5 , 6 , 7 , 8 . However, the high degree of symmetry in the crystalline structure of plasmonic materials (metals in particular) and in nanoantenna designs strongly quenches second harmonic generation 5 . Here, we describe doubly-resonant single-crystalline gold nanostructures with no axial symmetry 9 displaying spatial mode overlap at both the excitation and second harmonic wavelengths. The combination of these features allows the attainment of a nonlinear coefficient for second harmonic generation of ∼5 × 10 –10  W –1 , enabling a second harmonic photon yield higher than 3 × 10 6 photons per second. Theoretical estimations point toward the use of our nonlinear plasmonic nanoantennas as efficient platforms for label-free molecular sensing.

Magnetic skyrmions are chiral spin structures with a whirling configuration. Their topological properties, nanometre size and the fact that they can be moved by small current densities have opened a new paradigm for the manipulation of magnetization at the nanoscale. Chiral skyrmion structures have so far been experimentally demonstrated only in bulk materials and in epitaxial ultrathin films, and under an external magnetic field or at low temperature. Here, we report on the observation of stable skyrmions in sputtered ultrathin Pt/Co/MgO nanostructures at room temperature and zero external magnetic field. We use high lateral resolution X-ray magnetic circular dichroism microscopy to image their chiral Néel internal structure, which we explain as due to the large strength of the Dzyaloshinskii–Moriya interaction as revealed by spin wave spectroscopy measurements. Our results are substantiated by micromagnetic simulations and numerical models, which allow the identification of the physical mechanisms governing the size and stability of the skyrmions. Stable, single magnetic skyrmions are demonstrated at room temperature in ultrathin cobalt nanostructures.

Bats possess extraordinary adaptations, including flight, echolocation, extreme longevity and unique immunity. High-quality genomes are crucial for understanding the molecular basis and evolution of these traits. Here we incorporated long-read sequencing and state-of-the-art scaffolding protocols 1 to generate, to our knowledge, the first reference-quality genomes of six bat species ( Rhinolophus ferrumequinum , Rousettus aegyptiacus , Phyllostomus discolor , Myotis myotis , Pipistrellus kuhlii and Molossus molossus ). We integrated gene projections from our ‘Tool to infer Orthologs from Genome Alignments’ (TOGA) software with de novo and homology gene predictions as well as short- and long-read transcriptomics to generate highly complete gene annotations. To resolve the phylogenetic position of bats within Laurasiatheria, we applied several phylogenetic methods to comprehensive sets of orthologous protein-coding and noncoding regions of the genome, and identified a basal origin for bats within Scrotifera. Our genome-wide screens revealed positive selection on hearing-related genes in the ancestral branch of bats, which is indicative of laryngeal echolocation being an ancestral trait in this clade. We found selection and loss of immunity-related genes (including pro-inflammatory NF-κB regulators) and expansions of anti-viral APOBEC3 genes, which highlights molecular mechanisms that may contribute to the exceptional immunity of bats. Genomic integrations of diverse viruses provide a genomic record of historical tolerance to viral infection in bats. Finally, we found and experimentally validated bat-specific variation in microRNAs, which may regulate bat-specific gene-expression programs. Our reference-quality bat genomes provide the resources required to uncover and validate the genomic basis of adaptations of bats, and stimulate new avenues of research that are directly relevant to human health and disease 1 . Reference-quality genomes for six bat species shed light on the phylogenetic position of Chiroptera, and provide insight into the genetic underpinnings of the unique adaptations of this clade.

Geometrical frustration in magnetic materials often gives rise to exotic, low-temperature states of matter, such as the ones observed in spin ices. Here we report the imaging of the magnetic states of a thermally active artificial magnetic ice that reveal the fingerprints of a spin fragmentation process. This fragmentation corresponds to a splitting of the magnetic degree of freedom into two channels and is evidenced in both real and reciprocal space. Furthermore, the internal organization of both channels is interpreted within the framework of a hybrid spin–charge model that directly emerges from the parent spin model of the kagome dipolar spin ice. Our experimental and theoretical results provide insights into the physics of frustrated magnets and deepen our understanding of emergent fields through the use of tailor-made magnetism. By nanofabricating arrays of dipolar-coupled bistable single-domain nanomagnets, artificial model systems exhibiting collective ordering may be realized. Here, the authors present signatures of spin fragmentation in low-energy states of an artificial kagome ice.

We propose a new sensing device based on all-optical nano-objects placed in a suspended periodic array. We demonstrate that the intensity-based sensing mechanism can measure environment refractive index change of the order of 1.8×10−6, which is close to record efficiencies in plasmonic devices.

We studied the symmetry of magnetic properties and the resulting magnetic textures in ultra-thin epitaxial Au0.67Pt0.33/Co/W(110), a model system exhibiting perpendicular magnetic anisotropy and interface Dzyaloshinskii–Moriya interaction (DMI). As a peculiar feature, the C2v crystal symmetry induced by the Co/W interface results in an additional uniaxial in-plane magnetic anisotropy in the cobalt layer. Photo-emission electron microscopy with magnetic sensitivity reveals the formation of self-organised magnetic stripe domains oriented parallel to the hard in-plane magnetisation axis. We attribute this behavior to the lower domain wall energy when oriented along this axis, where both the DMI and the in-plane magnetic anisotropy favor a Néel domain wall configuration. The anisotropic domain wall energy also leads to the formation of elliptical skyrmion bubbles under a weak out-of-plane magnetic field.

Photoemission Electron Microscopy (PEEM) is a powerful and versatile full-field imaging technique based on the cathode lens, achieving lateral resolution down to ten nanometre range at the state of the art. In modern times, it has flourished at synchrotrons, where it has become one of the most sought-after microscopy tools, often referred to as XPEEM. By employing high-intensity, tunable sources of polarised soft X-ray radiation, PEEM enables absorption and photoemission spectroscopy at high lateral and elemental resolution, while also offering sensitivity to the local chemical, electronic, and magnetic structure. To date, surface and thin film magnetism has been one of the most prominent applications of synchrotron PEEM, with current research focusing on domain morphology in nanowires and nanostructures, exotic spin configurations, as well as spin manipulation and transport. On the other hand, the area where this technique has made the most remarkable progress is that of two-dimensional materials, beginning with graphene and rapidly expanding to the broader class of transition metal dichalcogenides. A rich variety of XPEEM applications is reviewed here, emphasising the usefulness of a multimodal experimental approach involving its parent technique, low-energy electron microscopy. XPEEM's ability to perform angle- and spin-resolved photoemission is highlighted as key to providing direct access to the electronic structure, with significant potential for studying a wide range of materials exhibiting quantum or topological properties. Finally, photoemission orbital tomography is introduced, with a focus on its capability to access the electronic structure of complex molecular interfaces at surfaces.

The recent proliferation of studies on terrorism has brought scholars from different fields and approaches to converge on this phenomenon. As a result, economists, social and political scientists have developed theories, evidence and, in a sense, even a peculiar jargon of their own. Starting from this assumption, the book aims to bring scholars with different expertise and background around the same table, showing how their individual perspectives can contribute to a broader understanding of the issue at stake. In other words, the aim that inspires the book is that the multi-disciplinary nature of terrorism requires a concerted effort by social sciences - in particular, economics and political science. The book deals with a number of issues - from the definition and forms of terrorism, to its economic determinants, from the distribution and forecast of terror attacks to the measurement of their impact on societies.

Graphene/ferromagnet interfaces have widely demonstrated the capability to host peculiar magnetic and electronic properties relevant for spintronic devices. In principle, besides strengthening perpendicular magnetic anisotropy (PMA) and sizable Dzyaloshinskii–Moriya interaction (DMI), graphene provides an additional advantage by acting as a protective layer against oxidation of the underlying metal film. However, the structural imperfections of graphene, often resulting from its growth conditions, can facilitate intercalation, which can compromise the underlying ferromagnetic layer. To address this issue, here, the use of a titania capping layer as a protective barrier for a heterostructure consisting of monolayer graphene grown on a thin cobalt film is proposed. The results demonstrate that the titanium oxide layer does not alter the properties of the interface, as confirmed by X‐ray photoemission spectroscopy (XPS) and X‐ray magnetic circular dichroism (XMCD) imaging. Furthermore, magneto‐optic Kerr effect (MOKE) measurements reveal that the interface's magnetic properties remain stable after prolonged exposure to ambient conditions. Absorption profile simulations show that the capping layer is transparent to visible wavelengths, demonstrating its capability to enable optical studies of atomic interfacial effects without the need for an ultra‐high vacuum (UHV) environment. These findings position titanium oxide as a robust, non‐invasive capping material for graphene‐based spintronic heterostructures. This study shows that a titanium oxide capping layer effectively preserves the chemical and magnetic integrity of graphene/cobalt heterostructures. The protective layer maintains perpendicular magnetic anisotropy and ensures stability under ambient conditions, while remaining transparent to visible light, thus enabling optical investigations of spintronic interfaces without the need for ultra‐high vacuum environments.

The terahertz (THz) region of the electromagnetic spectrum, spanning from 0.1 to 30 THz, represents a prospering area in photonics, with transformative applications in imaging, communications, and material analysis. However, the development of efficient and compact THz sources has long been hampered by intrinsic material limitations, inefficient conversion processes, and complex phase-matching requirements. Recent breakthroughs in nonlinear optical mechanisms, resonant metasurface engineering, and advances in the fabrication processes for materials such as lithium niobate (LN) and aluminum gallium arsenide (AlGaAs) have paved the way for innovative THz generation techniques. This review article explores the latest theoretical advances, together with key experimental results and outlines perspectives for future developments.