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The layered metamagnet CrSBr offers a rich interplay between magnetic, optical and electrical properties that can be extended down to the two-dimensional (2D) limit. Despite the extensive research regarding the long-range magnetic order in magnetic van der Waals materials, short-range correlations have been loosely investigated. By using Small-Angle Neutron Scattering (SANS) we show the formation of short-range magnetic regions in CrSBr with correlation lengths that increase upon cooling up to ca. 3 nm at the antiferromagnetic ordering temperature (TN ~ 140 K). Interestingly, these ferromagnetic correlations start developing below 200 K, i.e., well above TN. Below TN, these correlations rapidly decrease and are negligible at low-temperatures. The experimental results are well-reproduced by an effective spin Hamiltonian, which pinpoints that the short-range correlations in CrSBr are intrinsic to the monolayer limit, and discard the appearance of any frustrated phase in CrSBr at low-temperatures within our experimental window between 2 and 200 nm. Overall, our results are compatible with a spin freezing scenario of the magnetic fluctuations in CrSBr and highlight SANS as a powerful t

Magnomechanical systems provide a promising route for exploring coherent hybrid magnon-phonon interactions and hybrid information processing, but their realization has so far been limited by weak magnon-phonon coupling in conventional bulk platforms. We show that a suspended membrane of a two-dimensional van der Waals ferromagnet with in-plane magnetization and out-of-plane mechanical oscillations exhibits large magnomechanical coupling dominated by magnetoelastic interactions. The parametric single magnon-phonon coupling rate scales linearly with pre-strain and can reach hundreds of Hertz to low kiloHertz in suspended membranes of van der Waals ferromagnets such as CrGeTe_3 under experimentally realistic conditions. This rate exceeds typical values reported for YIG spheres by more than three orders of magnitude. Our results demonstrate that suspended membranes of van der Waals magnets provide a robust and highly tunable platform for magnomechanics.

Charged domain walls (CDW) in ferroelectrics are emerging as functional interfaces with potential applications in nonvolatile memory, logic, and neuromorphic computing. However, CDWs in conventional ferroelectrics are vertical, buried, or electrically inaccessible interfaces that prevent their use in functional devices. Here, we overcome these challenges by stacking two opposite polar domains of van der Waals ferroelectric $α$-In$_2$Se$_3$ to generate artificial head-head (H-H) CDWs and use edge contact to fabricate charged domain wall-based field-effect transistors (CDW-FET). We relate the atomic structure to the temperature-dependent electrical and magneto-transport of the CDW-FET. CDW-FETs exhibit a metal-to-insulator transition with decreasing temperature and enhanced conductance and field-effect mobility compared to single domain $α$-In$_2$Se$_3$. We identify two regimes of transport: variable range hopping due to disorder in the band edge below 70 K and thermally activated interfacial trap-assisted transport above 70 K. The CDW-FETs show room-temperature resistance down to 3.1 k$Ω$ which is 2-9 orders of magnitude smaller than the single CDW in thin-film ferroelectrics. These

For the development of nanoscale electronics and photonics using atomically thin two-dimensional (2D) materials, it is important to realize van der Waals (vdW) interfaces with low thermal resistance, to minimize performance reduction caused by heat accumulation. However, characterizing the thermal interface resistance between vdW materials is still a challenge. Here, we introduce a novel optomechanical methodology to characterize the thermal transport across interfaces in 2D heterostructures. We first determine the specific heat and thermal conductivity as the function of temperature for the upper and lower material layers separately and then extract the thermal boundary conductance (TBC) of the heterostructure from its thermal time constant. We obtain a TBC of $2.41 \pm 1.03$ and $4.14 \pm 1.74$~\si{MW m^{2} K^{-1}} for FePS$_3$/WSe$_2$ and MoS$_2$/FePS$_3$ interfaces, respectively, which are comparable to values reported in the literature. Moreover, they agree with a Debye model including the acoustic impedance mismatch of flexural phonons. This work enables efficient thermal management down to the nanoscale and offers new insights into energy dissipation in vdW heterostructures.

Van der Waals materials provide a versatile toolbox for the emergence of new quantum phenomena and the fabrication of functional heterostructures. Among them, the trihalide VI3 stands out for its unique magnetic and structural landscape. Here we investigate the spin and orbital magnetic degrees of freedom in the layered ferromagnet VI3 by means of temperature-dependent x-ray absorption spectroscopy and x-ray magnetic circular and linear dichroism. We detect localized electronic states and reduced magnetic dimensionality, due to electronic correlations. We furthermore provide experimental evidence of (a) an unquenched orbital magnetic moment (up to 0.66(7)) in the ferromagnetic state, and (b) an instability of the orbital moment in proximity of the spin reorientation transition. Our results support a coherent picture where electronic correlations give rise to a strong magnetic anisotropy and a large orbital moment, and establish VI3 as a prime candidate for the study of orbital quantum effects.

Polarization dependent x-ray absorption spectroscopy was used to study the magnetic ground state and the orbital occupation in bulk-phase VI$_3$ van der Waals crystals below and above the ferromagnetic and structural transitions. X-ray natural linear dichroism and X-ray magnetic circular dichroism spectra acquired at the V $L_{2,3}$ edges are compared against multiplet cluster calculations within the frame of the ligand field theory to quantify the intra-atomic electronic interactions at play and evaluate the effects of symmetry reduction occurring in a trigonally distorted VI$_6$ unit. We observed a non zero linear dichroism proving the presence of an anisotropic charge density distribution around the V$^{3+}$ ion due to the unbalanced hybridization between the Vanadium and the ligand states. Such hybridization acts as an effective trigonal crystal field, slightly lifting the degeneracy of the $t_{2g}^2$ ground state. However, the energy splitting associated to the distortion underestimates the experimental band gap, suggesting that the insulating ground state is stabilized by Mott correlation effects rather than via a Jahn-Teller mechanism. Our results clarify the role of the dis

We combine polarized infrared magneto-transmission and Faraday angle rotation measurements to map the collective excitations of the van der Waals antiferromagnet FePS$_3$. Below the Néel temperature ($T_\mathrm{N} \approx 118$ K), the phonon spectrum becomes strongly anisotropic, while a prominent excitation at 122 cm$^{-1}$ (15 meV) hardens on cooling and splits linearly with magnetic field,identifying its magnetic origin. From absolute transmission and Faraday angle measurements, we reconstruct the circular optical conductivities, revealing a pronounced dichroism of the field-split excitations. The upper branch near 129 cm$^{-1}$ shows an anomalously reduced dichroism, consistent with spin-phonon hybridization with a nearby infrared phonon. Several phonons exhibit sizable Faraday rotation, and Raman-active modes appear in the infrared spectra. Together with a broad mid-infrared band near 900 cm$^{-1}$ emerging only below $T_\mathrm{N}$, these observations point to inversion-symmetry breaking in the magnetic state. A weak Faraday feature near 320 cm$^{-1}$ ($\sim 40$ meV) further supports the presence of a higher-energy magnetic excitation. These findings underscore the intricate

Here, we use atomic resolution scanning transmission electron microscopy (STEM) and first principles calculations to study the atomic and electronic structure of strongly charged domain walls in $α$-In$_2$Se$_3$. STEM imaging and density functional theory (DFT) show that head-to-head (HH) domain walls contain a layer of nonpolar $β$-In$_2$Se$_3$, whereas tail-to-tail (TT) domain walls are atomically abrupt. We apply 4D STEM and multislice electron ptychography to map ferroelectric domains in 2D and 3D, showing that nearly $180^\circ$ domain walls exhibit complex, curved 3D structures that differ from ideal $180^\circ$ structures. Band structure calculations show localized conducting states within a $\sim$ 1 nm thick layer at both HH and TT domain walls, such as a midgap state at the $β$ layer of the HH domain wall. These properties make strongly charged domain walls in $α$-In$_2$Se$_3$ excellent candidates for realizing 2D electron or hole gases and domain wall engineering in van der Waals ferroelectrics.

The Fréchet distance is a distance measure between trajectories in $\Bbb{R}^d$ or walks in a graph $G$. Given constant-time shortest path queries, the Discrete Fréchet distance $D_G(P, Q)$ between two walks $P$ and $Q$ can be computed in $O(|P| \cdot |Q|)$ time using a dynamic program. Driemel, van der Hoog, and Rotenberg [SoCG'22] show that for weighted planar graphs this approach is likely tight, as there can be no strongly-subquadratic algorithm to compute a $1.01$-approximation of $D_G(P, Q)$ unless the Orthogonal Vector Hypothesis (OVH) fails. Such quadratic-time conditional lower bounds are common to many Fréchet distance variants. However, they can be circumvented by assuming that the input comes from some well-behaved class: There exist $(1+\varepsilon)$-approximations, both in weighted graphs and in $\Bbb{R}^d$, that take near-linear time for $c$-packed or $κ$-straight walks in the graph. In $\Bbb{R}^d$ there also exists a near-linear time algorithm to compute the Fréchet distance whenever all input edges are long compared to the distance. We consider computing the Fréchet distance in unweighted planar graphs. We show that there exist no strongly-subquadratic $1.25$-approx

Magnetic van der Waals materials provide an ideal playground for exploring the fundamentals of low-dimensional magnetism and open new opportunities for ultrathin spin processing devices. The Mermin-Wagner theorem dictates that as in reduced dimensions isotropic spin interactions cannot retain long-range correlations; the order is stabilized by magnetic anisotropy. Here, using ultrashort pulses of light, we demonstrate all-optical control of magnetic anisotropy in the two-dimensional van der Waals antiferromagnet NiPS$_3$. Tuning the photon energy in resonance with an orbital transition between crystal-field split levels of the nickel ions, we demonstrate the selective activation of a sub-THz two-dimensional magnon mode. The pump polarization control of the magnon amplitude confirms that the activation is governed by the instantaneous magnetic anisotropy axis emergent in response to photoexcitation of orbital states with a lowered symmetry. Our results establish pumping of orbital resonances as a universal route for manipulating magnetic order in low-dimensional (anti)ferromagnets.

The fabrication of van der Waals heterostructures, artificial materials assembled by individually stacking atomically thin (2D) materials, is one of the most promising directions in 2D materials research. Until now, the most widespread approach to stack 2D layers relies on deterministic placement methods which are cumbersome when fabricating multilayered stacks. Moreover, they tend to suffer from poor control over the lattice orientations and the presence of unwanted adsorbates between the stacked layers. Here, we present a different approach to fabricate ultrathin heterostructures by exfoliation of bulk franckeite which is a naturally occurring and air stable van der Waals heterostructure (composed of alternating SnS2-like and PbS-like layers stacked on top of each other). Presenting both an attractive narrow bandgap (<0.7 eV) and p-type doping, we find that the material can be exfoliated both mechanically and chemically down to few-layer thicknesses. We present extensive theoretical and experimental characterizations of the material's electronic properties and crystal structure, and explore applications for near-infrared photodetectors (exploiting its narrow bandgap) and for p

Initially, we make a detailed historical survey of van der Waals forces, collecting the main references on the subject. Then, we review a method recently proposed by Eberlein and Zietal to compute the dispersion van der Waals interaction between a neutral but polarizable atom and a perfectly conducting surface of arbitrary shape. This method has the advantage of relating the quantum problem to a corresponding classical one in electrostatics so that all one needs is to compute an appropriate Green function. We show how the image method of electrostatics can be conveniently used together with the Eberlein and Zietal mehtod (when the problem admits an image solution). We then illustrate this method in a couple of simple but important cases, including the atom-sphere system. Particularly, in our last example, we present an original result, namely, the van der Waals force between an atom and a boss hat made of a grounded conducting material.

In the rapidly expanding field of two-dimensional materials, magnetic monolayers show great promise for the future applications in nanoelectronics, data storage, and sensing. The research in intrinsically magnetic two-dimensional materials mainly focuses on synthetic iodide and telluride based compounds, which inherently suffer from the lack of ambient stability. So far, naturally occurring layered magnetic materials have been vastly overlooked. These minerals offer a unique opportunity to explore air-stable complex layered systems with high concentration of local moment bearing ions. We demonstrate magnetic ordering in iron-rich two-dimensional phyllosilicates, focusing on mineral species of minnesotaite, annite, and biotite. These are naturally occurring van der Waals magnetic materials which integrate local moment baring ions of iron via magnesium/aluminium substitution in their octahedral sites. Due to self-inherent capping by silicate/aluminate tetrahedral groups, ultra-thin layers are air-stable. Chemical characterization, quantitative elemental analysis, and iron oxidation states were determined via Raman spectroscopy, wavelength disperse X-ray spectroscopy, X-ray absorption

A sufficient level of data sovereignty is extremely difficult for consumers in practice. The EU General Data Protection Regulation guarantees comprehensive data subject rights, which must be implemented by responsible controllers through technical and organizational measures. Traditional approaches, such as the provision of lengthy data protection declarations or the downloading of raw personal data without further assistance, do not meet the requirements of informational self-determination. The new technical approaches outlined below, in particular AI-based transparency and access modalities, demonstrate the practicability of effective and versatile mechanisms. For this purpose, the relevant transparency information is extracted in a semi-automated way, represented in a machine-readable format, and then played out via diverse channels such as virtual assistants or the enrichment of search results. --- Hinreichende Datensouveränität gestaltet sich für Verbraucher:innen in der Praxis als äußerst schwierig. Die Europäische Datenschutzgrundverordnung garantiert umfassende Betroffenenrechte, die von verantwortlichen Stellen durch technisch-organisatorische Maßnahmen umzusetzen sind. Tr

Paper has the potential to dramatically reduce the cost of electronic components. In fact, paper is 10 000 times cheaper than crystalline silicon, motivating the research to integrate electronic materials on paper substrates. Among the different electronic materials, van der Waals materials are attracting the interest of the scientific community working on paper-based electronics because of the combination of high electrical performance and mechanical flexibility. Up to now, different methods have been developed to pattern conducting, semiconducting and insulating van der Waals materials on paper but the integration of superconductors remains elusive. Here, the deposition of NbSe2, an illustrative van der Waals superconductor, on standard copy paper is demonstrated. The deposited NbSe2 films on paper display superconducting properties (e.g. observation of Meissner effect and resistance drop to zero-resistance state when cooled down below its critical temperature) similar to those of bulk NbSe2.

We report on the large-scale synthesis of highly oriented ultrathin MoO3 layers using a simple and low-cost atmospheric pressure by van der Waals epitaxy growth on muscovite mica substrates. By this method we are able to synthetize high quality centimeter-scale MoO3 crystals with thicknesses ranging from 1.4 nm (two layers) up to a few nanometers. The crystals can be easily transferred to an arbitrary substrate (such as SiO2) by a deterministic transfer method and extensively characterized to demonstrate the high quality of the resulting crystal. We also study the electronic band structure of the material by density functional theory calculations. Interestingly, the calculations demonstrate that bulk MoO3 has a rather weak electronic interlayer interaction and thus it presents a monolayer-like band structure. Finally, we demonstrate the potential of this synthesis method for optoelectronic applications by fabricating large-area field-effect devices (10 micrometers by 110 micrometers in lateral dimensions), finding responsivities of 30 mA/W for a laser power density of 13 mW/cm2 in the UV region of the spectrum and also as an electron acceptor in a MoS2-based field-effect transistor

The correct detection of dense article layout and the recognition of characters in historical newspaper pages remains a challenging requirement for Natural Language Processing (NLP) and machine learning applications on historical newspapers in the field of digital history. Digital newspaper portals for historic Germany typically provide Optical Character Recognition (OCR) text, albeit of varying quality. Unfortunately, layout information is often missing, limiting this rich source's scope. Our dataset is designed to enable the training of layout and OCR modells for historic German-language newspapers. The Chronicling Germany dataset contains 693 annotated historical newspaper pages from the time period between 1852 and 1924. The paper presents a processing pipeline and establishes baseline results on in- and out-of-domain test data using this pipeline. Both our dataset and the corresponding baseline code are freely available online. This work creates a starting point for future research in the field of digital history and historic German language newspaper processing. Furthermore, it provides the opportunity to study a low-resource task in computer vision

Spintronics is concerned with replacing charge current with current of spin, the electron's intrinsic angular momentum. In magnetic insulators, spin currents are carried by magnons, the quanta of spin-wave excitations on top of the magnetically ordered state. Magnon spin currents are especially promising for information technology due to their low intrinsic damping, non-reciprocal transport, micrometer wavelengths at microwave frequencies, and strong interactions that enable signal transduction. In this perspective, we give our view on the progress and challenges towards realizing magnon spintronics based on atomically thin Van der Waals magnets, a recently discovered class of magnetic materials of which the tunability and versatility has attracted a great deal of ongoing research.

The WiggleZ Dark Energy Survey is a large-scale structure survey of intermediate-redshift UV-selected emission-line galaxies scheduled to cover 1000 sq deg, spanning a broad redshift range 0.2 < z < 1.0. The main scientific goal of the survey is the measurement of baryon acoustic oscillations (BAO) in the galaxy clustering pattern at a significantly higher redshift than previous studies. The BAO may be applied as a standard cosmological ruler to constrain dark energy models. Based on the first 20% of the dataset, we present initial results concerning the small-scale clustering of the WiggleZ targets, together with survey forecasts. The WiggleZ galaxy population possesses a clustering length r_0 = 4.40 +/- 0.12 Mpc/h, which is significantly larger than z=0 UV-selected samples, with a slope gamma = 1.92 +/- 0.08. This clustering length is comparable to z=3 Lyman Break Galaxies with similar UV luminosities. The full survey, scheduled for completion in 2010, will map an effective volume V_eff ~ 1 Gpc^3 (evaluated at a scale k = 0.15 h/Mpc) and will measure the angular-diameter distance and Hubble expansion rates in three redshift bins with accuracies ~ 5%. We will determine the v