Unconventional Anomalous Hall Effect Driven by Self-Intercalation in Covalent 2D Magnet CrTe.

Covalent 2D magnets such as CrTe, which feature self-intercalated magnetic cations located between monolayers of transition-metal dichalcogenide material, offer a unique platform for controlling magnetic order and spin texture, enabling new potential applications for spintronic devices. Here, it is demonstrated that the unconventional anomalous Hall effect (AHE) in CrTe, characterized by additional humps and dips near the coercive field in AHE hysteresis, originates from an intrinsic mechanism dictated by the self-intercalation. This mechanism is distinctly different from previously proposed mechanisms such as topological Hall effect, or two-channel AHE arising from spatial inhomogeneities.

Comparing transmission- and epi-BCARS: a round robin on solid-state materials.

Broadband coherent anti-Stokes Raman scattering (BCARS) is a powerful spectroscopy method combining high signal intensity with spectral sensitivity, enabling rapid imaging of heterogeneous samples in biomedical research and, more recently, in crystalline materials. However, BCARS encounters spectral distortion due to a setup-dependent non-resonant background (NRB). This study assesses BCARS reproducibility through a round robin experiment using two distinct BCARS setups and crystalline materials with varying structural complexity, including diamond, 6H-SiC, KDP, and KTP.

Terahertz Twistoptics-Engineering Canalized Phonon Polaritons.

The terahertz (THz) frequency range is key to studying collective excitations in many crystals and organic molecules. However, due to the large wavelength of THz radiation, the local probing of these excitations in smaller crystalline structures or few-molecule arrangements requires sophisticated methods to confine THz light down to the nanometer length scale, as well as to manipulate such a confined radiation. For this purpose, in recent years, taking advantage of hyperbolic phonon polaritons (HPhPs) in highly anisotropic van der Waals (vdW) materials has emerged as a promising approach, offering a multitude of manipulation options, such as control over the wavefront shape and propagation direction.

Néel Skyrmion Bubbles in LaSrMnRuO Multilayers.

Ferromagnetic LaSrMnRuO epitaxial multilayers with controlled variation of the Ru/Mn content were synthesized to engineer canted magnetic anisotropy and variable exchange interactions, and to explore the possibility of generating a Dzyaloshinskii-Moriya interaction. The ultimate aim of the multilayer design is to provide the conditions for the formation of domains with nontrivial magnetic topology in an oxide thin film system. Employing magnetic force microscopy and Lorentz transmission electron microscopy in varying perpendicular magnetic fields, magnetic stripe domains separated by Néel-type domain walls as well as Néel skyrmions smaller than 100 nm in diameter were observed.

Impact of 3D Curvature on the Polarization Orientation in Non-Ising Domain Walls.

Ferroelectric domain boundaries are quasi-two-dimensional functional interfaces with high prospects for nanoelectronic applications. Despite their reduced dimensionality, they can exhibit complex non-Ising polarization configurations and unexpected physical properties. Here, the impact of the three-dimensional (3D) curvature on the polarization profile of nominally uncharged 180° domain walls in LiNbO is studied using second-harmonic generation microscopy and 3D polarimetry analysis.

Germanium Monosulfide as a Natural Platform for Highly Anisotropic THz Polaritons.

Terahertz (THz) electromagnetic radiation is key to access collective excitations such as magnons (spins), plasmons (electrons), or phonons (atomic vibrations), thus bridging topics between optics and solid-state physics. Confinement of THz light to the nanometer length scale is desirable for local probing of such excitations in low-dimensional systems, thereby circumventing the large footprint and inherently low spectral power density of far-field THz radiation. For that purpose, phonon polaritons (PhPs) in anisotropic van der Waals (vdW) materials have recently emerged as a promising platform for THz nanooptics.

Brillouin and Raman imaging of domain walls in periodically-poled 5%-MgO:LiNbO3.

Recently, ferroelectric domain walls (DWs) have attracted considerable attention due to their intrinsic topological effects and their huge potential for optoelectronic applications. In contrast, many of the underlying physical properties and phenomena are not well characterized. In this regard, analyzing the vibrational properties, e.

Quantifying the refractive index of ferroelectric domain walls in periodically poled LiNbO single crystals by polarization-sensitive optical coherence tomography.

Domain walls (DWs) in ferroelectric (FE) and multiferroic materials possess an ever-growing potential as integrated functional elements, for instance in optoelectronic nanodevices. Mandatory, however, is the profound knowledge of the local-scale electronic and optical properties, especially at DWs that are still incompletely characterized to date. Here, we quantify the refractive index of individual FE DWs in periodically-poled LiNbO (PPLN) single crystals.

Electric field-induced crystallization of ferroelectric hafnium zirconium oxide.

Ferroelectricity in crystalline hafnium oxide thin films is strongly investigated for the application in non-volatile memories, sensors and other applications. Especially for back-end-of-line (BEoL) integration the decrease of crystallization temperature is of major importance. However, an alternative method for inducing ferroelectricity in amorphous or semi-crystalline hafnium zirconium oxide films is presented here, using the newly discovered effect of electric field-induced crystallization in hafnium oxide films.

Far-Infrared Near-Field Optical Imaging and Kelvin Probe Force Microscopy of Laser-Crystallized and -Amorphized Phase Change Material GeSbTe.

Chalcogenide phase change materials reversibly switch between non-volatile states with vastly different optical properties, enabling novel active nanophotonic devices. However, a fundamental understanding of their laser-switching behavior is lacking and the resulting local optical properties are unclear at the nanoscale. Here, we combine infrared scattering-type scanning near-field optical microscopy (SNOM) and Kelvin probe force microscopy (KPFM) to investigate four states of laser-switched GeSbTe (as-deposited amorphous, crystallized, reamorphized, and recrystallized) with nanometer lateral resolution.

Potassium Ion Conductivity in the Cubic Labyrinth of a Piezoelectric, Antiferromagnetic Oxoferrate(III) Tellurate(VI).

Orange-colored crystals of the oxoferrate tellurate K Fe Te O [x=0.222(4)] were synthesized in a potassium hydroxide hydroflux with a molar water-base ratio n(H O)/n(KOH) of 1.5 starting from Fe(NO )  ⋅ 9H O, TeO and H O at about 200 °C.

A FeFET with a novel MFMFIS gate stack: towards energy-efficient and ultrafast NVMs for neuromorphic computing.

The discovery of ferroelectricity in the fluorite structure based hafnium oxide (HfO) material sparked major efforts for reviving the ferroelectric field effect transistor (FeFET) memory concept. A Novel metal-ferroelectric-metal-ferroelectric-insulator-semiconductor (MFMFIS) FeFET memory is reported based on dual ferroelectric integration as an MFM and MFIS in a single gate stack using Si-doped Hafnium oxide (HSO) ferroelectric (FE) material. The MFMFIS top and bottom electrode contacts, dual HSO based ferroelectric layers, and tailored MFM to MFIS area ratio (AR-TB) provide a flexible stack structure tuning for improving the FeFET performance.

Probing subwavelength in-plane anisotropy with antenna-assisted infrared nano-spectroscopy.

Infrared nano-spectroscopy based on scattering-type scanning near-field optical microscopy (s-SNOM) is commonly employed to probe the vibrational fingerprints of materials at the nanometer length scale. However, due to the elongated and axisymmetric tip shank, s-SNOM is less sensitive to the in-plane sample anisotropy in general. In this article, we report an easy-to-implement method to probe the in-plane dielectric responses of materials with the assistance of a metallic disk micro-antenna.

Tricyanidoferrates(-IV) and Ruthenates(-IV) with Non-Innocent Cyanido Ligands.

Exceptionally electron-rich, nearly trigonal-planar tricyanidometalate anions [Fe(CN) ] and [Ru(CN) ] were stabilized in LiSr [Fe(CN) ] and AE [M(CN) ] (AE=Sr, Ba; M=Fe, Ru). They are the first examples of group 8 elements with the oxidation state of -IV. Microcrystalline powders were obtained by a solid-state route, single crystals from alkali metal flux.

Sub-diffractional cavity modes of terahertz hyperbolic phonon polaritons in tin oxide.

Hyperbolic phonon polaritons have recently attracted considerable attention in nanophotonics mostly due to their intrinsic strong electromagnetic field confinement, ultraslow polariton group velocities, and long lifetimes. Here we introduce tin oxide (SnO) nanobelts as a photonic platform for the transport of surface and volume phonon polaritons in the mid- to far-infrared frequency range. This report brings a comprehensive description of the polaritonic properties of SnO as a nanometer-sized dielectric and also as an engineered material in the form of a waveguide.

Hypergravity affects cell traction forces of fibroblasts.

Cells sense and react on changes of the mechanical properties of their environment and, likewise, respond to external mechanical stress applied to them. However, whether the gravitational field as overall body force modulates cellular behavior is unclear. Different studies demonstrated that micro- and hypergravity influences the shape and elasticity of cells, initiate cytoskeleton reorganization, and influence cell motility.

Nanoscale-Confined Terahertz Polaritons in a van der Waals Crystal.

Electromagnetic field confinement is crucial for nanophotonic technologies, since it allows for enhancing light-matter interactions, thus enabling light manipulation in deep sub-wavelength scales. In the terahertz (THz) spectral range, radiation confinement is conventionally achieved with specially designed metallic structures-such as antennas or nanoslits-with large footprints due to the rather long wavelengths of THz radiation. In this context, phonon polaritons-light coupled to lattice vibrations-in van der Waals (vdW) crystals have emerged as a promising solution for controlling light beyond the diffraction limit, as they feature extreme field confinements and low optical losses.

Optical-field driven charge-transfer modulations near composite nanostructures.

Optical activation of material properties illustrates the potentials held by tuning light-matter interactions with impacts ranging from basic science to technological applications. Here, we demonstrate for the first time that composite nanostructures providing nonlocal environments can be engineered to optically trigger photoinduced charge-transfer-dynamic modulations in the solid state. The nanostructures explored herein lead to out-of-phase behavior between charge separation and recombination dynamics, along with linear charge-transfer-dynamic variations with the optical-field intensity.

Spatially confined vector fields at material-induced resonances in near-field-coupled systems.

Local electric fields play the key role in near-field optical examinations and are especially appealing when exploring heterogeneous or even anisotropic nano-systems. Scattering-type near-field optical microscopy (s-SNOM) is the most commonly used method applied to explore and quantify such confined electric fields at the nanometer length scale: while most works so far did focus on analyzing the z-component oriented perpendicular to the sample surface under p-polarized tip/sample illumination only, recent experimental efforts in s-SNOM report that material resonant excitation might equally allow to probe in-plane electric field components. We thus explore this local vector-field behavior for a simple particle-tip/substrate system by comparing our parametric simulations based on finite element modelling at mid-IR wavelengths, to the standard analytical tip-dipole model.

Direct nanoscopic observation of plasma waves in the channel of a graphene field-effect transistor.

Plasma waves play an important role in many solid-state phenomena and devices. They also become significant in electronic device structures as the operation frequencies of these devices increase. A prominent example is field-effect transistors (FETs), that witness increased attention for application as rectifying detectors and mixers of electromagnetic waves at gigahertz and terahertz frequencies, where they exhibit very good sensitivity even high above the cut-off frequency defined by the carrier transit time.

Resource-Efficient Low-Temperature Synthesis of Microcrystalline Pb B O X (X = Cl, Br) for Surfaces Studies by Optical Second Harmonic Generation.

Optically nonlinear Pb B O X (X = Cl, Br) borate halides are an important group of materials for second harmonic generation (SHG). Additionally, they also possess excellent photocatalytic activity and stability in the process of dechlorination of chlorophenols, which are typical persistent organic pollutants. It would be of great interest to conduct in situ (photo-) catalysis investigations during the whole photocatalytic process by SHG when considering them as photocatalytic materials.

Nonlinear plasmonic response of doped nanowires observed by infrared nanospectroscopy.

We report a strong shift of the plasma resonance in highly-doped GaAs/InGaAs core/shell nanowires (NWs) for intense infrared excitation observed by scattering-type scanning near-field infrared microscopy. The studied NWs show a sharp plasma resonance at a photon energy of about 125 meV in the case of continuous wave excitation by a CO laser. Probing the same NWs with the pulsed free-electron laser with peak electric field strengths up to several 10 kV cm reveals a power-dependent redshift to about 95 meV and broadening of the plasmonic resonance.

Designing a Robust Kelvin Probe Setup Optimized for Long-Term Surface Photovoltage Acquisition.

We introduce a robust low-budget Kelvin probe design that is optimized for the long-term acquisition of surface photovoltage (SPV) data, especially developed for highly resistive systems, which exhibit-in contrast to conventional semiconductors-very slow photoinduced charge relaxation processes in the range of hours and days. The device provides convenient optical access to the sample, as well as high mechanical and electrical stability due to off-resonance operation, showing a noise band as narrow as 1 mV. Furthermore, the acquisition of temperature-dependent SPV transients necessary for SPV-based deep-level transient spectroscopy becomes easily possible.