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Encapsulating few-layer graphene (FLG) in hexagonal boron nitride (hBN) can cause nanoscale inhomogeneities in the FLG, including changes in stacking domains and topographic defects. Due to the diffraction limit, characterizing these inhomogeneities is challenging. Recently, the visualization of stacking domains in encapsulated four-layer graphene (4LG) has been demonstrated with phonon polariton (PhP)-assisted near-field imaging. However, the underlying coupling mechanism and ability to image subdiffractional-sized inhomogeneities remain unknown. Here, direct replicas and magnified images of subdiffractional-sized inhomogeneities in hBN-covered trilayer graphene (TLG) and encapsulated 4LG, enabled by the hyperlensing effect, are retrieved. This hyperlensing effect is mediated by hBN's hyperbolic PhP that couple to the FLG's plasmon polaritons. Using near-field microscopy, the coupling is identified by determining the polariton dispersion in hBN-covered TLG to be stacking-dependent. This work demonstrates super-resolution and magnified imaging of inhomogeneities, paving the way for the realization of homogeneous encapsulated FLG transport samples to study correlated physics., (© 2025 The Author(s). Advanced Science published by Wiley‐VCH GmbH.)

The dipole ordering in Sn (Pb) 2 P 2 S (Se) 6 materials may be tuned by chemical substitution realizing a ferroelectric quantum phase transition and quantum glassy or relaxor type phenomena on different parts of the phase diagram. The introduction of Ge impurity increases the temperature of the phase transitions and initiates a more pronounced Ising type critical anomaly in the Sn 2 P 2 S 6 crystal, does not shift the coordinate of the Lifshitz point x LP in Sn 2 P 2 (Se x S 1 − x) 6 mixed crystals, and induces the appearance of a ferroelectric phase transition in quantum paraelectrics Pb 2 P 2 S 6 and inhomogeneous polar ordering in (Pb 0.7 Sn 0.3) 2 P 2 S (Se) 6 crystals. For the Pb 2 P 2 S 6 crystal, the real part of the dielectric permittivity in the quantum critical regime varies as 1 / T 2 instead of the expected 1 / T 3 behavior for uniaxial materials. Such an observation can be partially explained by a screening phenomenon in the semiconductor materials of the Sn (Pb) 2 P 2 S (Se) 6 system, which weakens the long-range electric dipole interactions, and also provides, at high temperatures, a critical behavior near the Lifshitz point (studied by thermal diffusivity) similar to the one predicted in the case of systems with short-range interactions. At low temperatures, a quantum critical behavior in the Pb 2 P 2 S 6 crystal can be established by a small amplitude of electric dipoles together with the nonlinear coupling between polar and antipolar fluctuations. An increase in thermal conductivity is induced by Ge impurity in the Pb 2 P 2 S 6 crystal, which is explained by the weakening of the acoustic phonons resonance scattering by soft optic phonons because of the appearance of ferroelectric phase polar clusters. [ABSTRACT FROM AUTHOR]

A contactless technique for direct time-resolved measurements of the full dynamics of the adiabatic temperature change in electrocaloric materials is introduced. The infrared radiation emitted by the electrocaloric sample is sensitively detected with μs time resolution and mK temperature resolution. We present time-resolved measurements of the electrocaloric effect up to kHz frequencies of the driving electric field and down to small field strengths. The simultaneous recording of transients for applied electric field and induced polarization gives a comprehensive view of the correlation of electrocaloric and ferroelectric properties. The technique can further be applied to the continuous measurement of fatigue for > 1 0 6 electric field cycles. [ABSTRACT FROM AUTHOR]

Nanocomposite materials consist of nanometer-sized quantum objects such as atoms, molecules, voids or nanoparticles embedded in a host material. These quantum objects can be exploited as a super-structure, which can be designed to create material properties targeted for specific applications. For electromagnetism, such targeted properties include field enhancements around the bandgap of a semiconductor used for solar cells, directional decay in topological insulators, high kinetic inductance in superconducting circuits, and many more. Despite very different application areas, all of these properties are united by the common aim of exploiting collective interaction effects between quantum objects. The literature on the topic spreads over very many different disciplines and scientific communities. In this review, we present a cross-disciplinary overview of different approaches for the creation, analysis and theoretical description of nanocomposites with applications related to electromagnetic properties. [ABSTRACT FROM AUTHOR]

Infrared fingerprint spectra can reveal the chemical nature of materials down to 20-nm detail, far below the diffraction limit, when probed by scattering-type scanning near-field optical microscopy (s-SNOM). But this was impossible with living cells or aqueous processes as in corrosion, due to water-related absorption and tip contamination. Here, we demonstrate infrared s-SNOM of water-suspended objects by probing them through a 10-nm thick SiN membrane. This separator stretches freely over up to 250 µm, providing an upper, stable surface to the scanning tip, while its lower surface is in contact with the liquid and localises adhering objects. We present its proof-of-principle applicability in biology by observing simply drop-casted, living E. coli in nutrient medium, as well as living A549 cancer cells, as they divide, move and develop rich sub-cellular morphology and adhesion patterns, at 150 nm resolution. Their infrared spectra reveal the local abundances of water, proteins, and lipids within a depth of ca. 100 nm below the SiN membrane, as we verify by analysing well-defined, suspended polymer spheres and through model calculations. SiN-membrane based s-SNOM thus establishes a novel tool of live cell nano-imaging that returns structure, dynamics and chemical composition. This method should benefit the nanoscale analysis of any aqueous system, from physics to medicine. [ABSTRACT FROM AUTHOR]

Recent progress in laser-based high-repetition rate extreme ultraviolet (EUV) light sources and multidimensional photoelectron spectroscopy enables the build-up of a new generation of time-resolved photoemission experiments. Here, we present a setup for time-resolved momentum microscopy driven by a 1 MHz fs EUV table-top light source optimized for the generation of 26.5 eV photons. The setup provides simultaneous access to the temporal evolution of the photoelectron's kinetic energy and in-plane momentum. We discuss opportunities and limitations of our new experiment based on a series of static and time-resolved measurements on graphene. [ABSTRACT FROM AUTHOR]

Zn1-xMnxO (x = 0:00, 0.01, and 0.05, respectively) was synthesized by using solid state reaction method. The structural properties were characterized by using X-ray diffraction and scanning electron microscopy. Optical properties were investigated by UV-visible spectroscopy. X-ray diffraction patterns indicate that all samples have hexagonal wurtzite structure without any impurity phases. The diffraction intensity increases and the peak position shifts to a lower 2θ angle with Mn concentration. The lattice parameters a and c, the volume of unit cell increase with Mn content indicating that Mn2+ ions go to Zn2+ ions in ZnO lattice. The grain size increases with Mn doping while the microstrain and dislocation density decrease. UV-vis spectra of the samples show that undoped ZnO sample has an energy band gap Eg of 3.34 eV. The optical study indicates a red shift in the absorbance spectra and a decrease in the band gap Eg with Mn content. This decrease of band gap may be attributed to the influence of dopant ions. The morphology and grain distribution of ZnO samples were analysed by scanning electron microscopy. The particle sizes are higher in doped samples when compared to the undoped sample and the surface roughness increases with Mn content. The grains are closely, densely packed and pores/voids between the grains increase with Mn content. [ABSTRACT FROM AUTHOR]

In this study, we have prepared Mn-doped zinc sulfide diluted magnetic semiconductors with varying manganese concentrations ( x = 0.00, 0.02, 0.04, 0.06, 0.08, 0.10 mol%) using co-precipitation method. The single-phase nano-crystalline ZnMnS powders have been confirmed with X-ray diffraction. The residual strains also have been calculated, and have been observed to affect the lattice constants. The surface morphology is investigated with scanning electron microscopy, which illustrates the presence of smaller grains, which coalescence to form larger grains. The presence of the ferromagnetism at room temperature has been observed; however, significant paramagnetic contribution is also present. The observed weak ferromagnetism might be due to the structural and surface imperfections. The single-phase ZnMnS exhibiting magnetism at room temperature evidences the potential spintronic applications. [ABSTRACT FROM AUTHOR]

It has been ten years since the discovery of the giant electrocaloric effect in ferroelectric materials showed that it is possible to employ this effect for substantial cooling applications. This last decade has been marked by increasing research interest, especially in characterizing and measuring the electrocaloric effect using both the so-called indirect and direct approaches. In this context, a comprehensive summary and careful reexamination of these approaches are very timely and of great importance to justify the assumptions used in different measurement techniques. This review is therefore dedicated to cover recent important and rapid advances from both the indirect and direct measurements and provides critical insights relevant for quantifying the electrocaloric effect. It involves electrocaloric materials from normal ferroelectrics, antiferroelectrics, and relaxors, and it fundamentally focuses on how the electrocaloric entropy changes in response to electric field in these typical electrocalorics. The article addresses recent developments, especially during the past three years, such as technical selection of proper polarization-electric field loops, negative electrocaloric effect in antiferroelectrics and relaxors, the controversial debate on the indirect method in relaxors, the important role of field dependence of specific heat, kinetic factors, and so on. Moreover, this review also is concerned with extracting reliable data by direct measurements. Four typical techniques and devices used recently, such as thermocouples, differential scanning calorimeters, specifically designed calorimeters, and scanning thermal microscopy, are briefly reviewed, while infrared cameras are emphasized. We hope that our review will not only provide a useful background to understand fundamentally the electrocaloric effect and what one really measures but also may act as a practical guide to exploit and develop electrocalorics towards the design of suitable devices. [ABSTRACT FROM AUTHOR]

Many important breakthroughs and significant engineering developments have been achieved during the past two decades in the field of caloric materials. In this review, we address ferroelectrics emerging as ideal materials which permit both giant elastocaloric and/or electrocaloric responses near room temperature. We summarize recent strategies for improving caloric responses using geometrical optimization, maximizing the number of coexisting phases, combining positive and negative caloric responses, introducing extra degree of freedom like mechanical stress/pressure, and multicaloric effect driven by either single stimulus or multiple stimuli. This review highlights the promising perspective of ferroelectrics for developing next-generation solid-state refrigeration. [ABSTRACT FROM AUTHOR]

Ferroelectrics are attractive candidate materials for environmentally friendly solid state refrigeration free of greenhouse gases. Their thermal response upon variations of external electric fields is largest in the vicinity of their phase transitions, which may occur near room temperature. The magnitude of the effect, however, is too small for useful cooling applications even when they are driven close to dielectric breakdown. Insight from microscopic theory is therefore needed to characterize materials and provide guiding principles to search for new ones with enhanced electrocaloric performance. Here, we derive from well-known microscopic models of ferroelectricity meaningful figures of merit for a wide class of ferroelectric materials. Such figures of merit provide insight into the relation between the strength of the effect and the characteristic interactions of ferroelectrics such as dipolar forces. We find that the long range nature of these interactions results in a small effect. A strategy is proposed to make it larger by shortening the correlation lengths of fluctuations of polarization. In addition, we bring into question other widely used but empirical figures of merit and facilitate understanding of the recently observed secondary broad peak in the electrocalorics of relaxor ferroelectrics. [ABSTRACT FROM AUTHOR]

During the last few years, the increasing demand of energy for refrigeration applications has relived the interest of the scientific community in the study of alternative methods to the traditional gas-based refrigeration. Within this framework, the use of solid state refrigeration based on the electrocaloric effect reveals itself as one of the most promising technologies. In this work, we analyze how the temperature change associated with the electrocaloric effect shows a correlation with the electrical properties of a commercial multilayer capacitor. In that sense, we established a clear relation between the adsorption currents and the temperature change produced by the electrocaloric effect. Additionally, intrinsic leakage currents are responsible for the sample heating due to the Joule effect. These well distinguished contributions can be useful during the design of solid state refrigeration devices based on the electrocaloric effect. [ABSTRACT FROM AUTHOR]

The magnetism sources and magnetic mechanism of Ni-doped ZnO remain unknown to date. In this study, the plane-wave ultrasoft pseudopotential technology of generalized gradient approximation +U based on spin-density-functional theory was used to investigate the magnetism sources and magnetic mechanism of Ni-doped ZnO. Results showed that the total magnetic moment of the ZnO system with Ni doping and O vacancy was similar to that of Ni-doped ZnO. Compared with the ZnO system with Ni doping and O vacancy, the doping system with Ni doping and Zn vacancy exhibited a larger magnetic moment, smaller formation energy, and better stability, and it was easier to dope. The magnetism of the Zn14NiO16 system mainly resulted from the hybrid coupling electron exchange effect among the O-2p (nearest to the Zn vacancy and Ni atom), Ni-3d, and Zn-4s orbits. This effect was based on the hole carriers in the complex as the medium. In the ZnO system with Ni doping and Zn vacancy, the magnetic moment slightly decreased with increasing doping amount. Results showed that the system with Ni doping and Zn vacancy was ferromagnetic. In addition, the Curie temperature of the doping system was at room temperature. [ABSTRACT FROM AUTHOR]