Advanced Physics Research最新文献

The pressure-driven Mott-transition in Chromium doped V₂O₃ films is investigated by direct electrical measurements on polycrystalline films with thicknesses down to 10 nm, and doping concentrations of 2%, 5%, and 15%. A change in resistivity of nearly two orders of magnitude is found for 2% doping. A simulation model based on a scaling law description of the phase transition and percolative behavior in a resistor lattice is developed. This is used to show that despite significant deviations in the film structure from single crystals, the transition behavior is very similar. Finally, the influence of the variability between grains on the characteristics of scaled devices is investigated and found to allow for scaling down to at least 50 nm device width.

This study provides analytic solutions for the magnetic field of coils and magnets that have a non-axisymmetric cylindrical geometry with a rectangular cross-section. New analytic solutions are provided for radially magnetized permanent magnet arcs, thin coil disc sectors, and thick coil sectors. If components of the 3D field are not representable in closed-form or as canonical Legendre elliptic integrals, the exact solution is given in terms of a series of regularized beta functions. The limit and hence spatial convergence is found to these series, giving a well-defined and fast solving algorithm for computation. The equations can be readily applied to find the magnetostatic field in linear or non-linear systems that contain a large set of elements. Example applications are provided to demonstrate how the field can be used to calculate forces and benchmark computational efficiency of the equations. A thorough review of the preceding literature and background theory is provided before a detailed methodology obtaining the analytic solutions contained in this compendium, and further related geometries in cylindrical or spherical coordinates. This is the first study to comprehensively solve the field equations for this collection of electromagnetic geometries.

Quantum dots (QDs) are essential luminescent materials with applications in wide-color-gamut displays requiring exceptional color reproducibility. Multinary semiconductor QDs composed of groups I, III and VI elements are expected to serve as eco-friendly materials to replace conventional QDs owing to the potential narrow spectral widths and tunable bandgaps of the former. Although optimized Ag–In–Ga–S/Ga–S core/shell QDs (AIGS QDs) have exhibited vibrant green emissions, electroluminescence from QD-based light-emitting diodes (QLEDs) incorporating these AIGS QDs is reduced as a consequence of the effects of defect sites. The present work therefore examines the incorporation of electron transport materials (ETMs) into AIGS QD emitting layers. A device incorporating emitting layers composed of AIGS QDs and 2,4,6-tris(3-(3-pyridyl)phenyl)-1,3,5-triazine (TmPPyTz), with the latter acting as a highly conductive ETM, exhibits a low driving voltage and high efficiency. Furthermore, the addition of two ETMs — TmPPyTz and tris(2,4,6-trimethyl-3-(pyridin-3-yl)phenyl)borane — is found to provide enhanced luminescence properties because these materials are deposited in the emitting layer in different forms and hence has varying effects in terms of improving conductivity and charge balance. The resulting QLEDs have a sharp spectral width of 30 nm, suggesting a level of color purity suitable for wide-color-gamut displays.

Gain-dissipative Ising machines (GIMs) are annealers inspired by physical systems such as Ising spin glasses to solve combinatorial optimization problems. Compared to traditional quantum annealers, GIM is relatively easier to scale and can save on additional power consumption caused by low-temperature cooling. However, traditional GIMs have a limited noise margin. Specifically, their normal operation requires ensuring that the noise intensity is lower than their saturation fixed point amplitude, which may result in increased power consumption to suppress noise-induced spin state switching. To enhance the noise robustness of GIM, in this study a GIM based on a topologically defective lattice potential (TDLP) is proposed. Numerical simulations demonstrate that the TDLP-based GIM can accurately simulate the bifurcation spin evolution in the Ising model. Furthermore, through the MAXCUT benchmark based on G-set graphs, the optimal performance of TDLP-based GIM is shown to surpass that of traditional GIMs. Additionally, the proposed TDLP-based GIM successfully solves the MAXCUT benchmark and domain clustering dynamics benchmark based on G-set graphs when the noise intensity exceeds its saturation fixed-point amplitude. This indicates that the proposed system provides a promising architecture for breaking the small noise constraints required by traditional GIMs.

Transient electrical pulsing is used to investigate the slowed charge density wave (CDW) kinetics of 1T-TaS₂. These measurements distinguish a fast response of the material, consistent with the onset of self-heating, from much slower transients that occur on timescales orders of magnitude longer than this. The latter variations appear consistent with slow configurational changes in the CDW, which, due to the thin nature of the 1T-TaS₂, can be distinguished from the much faster dynamics of Joule heating. Experiments in which the cooling of the material is interrupted, demonstrate the possibility of “programming” it in different, strongly nonequilibrium, CDW phases. Collectively, the results point to the existence of a complex free-energy space for the thinned material, whose multi-valley structure and hidden metastable states govern the resulting thermal and field-driven dynamics. Crucially, this work demonstrates that while the CDW dynamics in this material may have a thermal character, the timescales associated with these motions can be very different from those on which self-heating occurs. This discovery will be important for efforts to implement active devices that utilize the CDW states of thinned 1T-TaS₂.

Block polymers remain an extensively studied class of macromolecules due to their ability to self-organize spontaneously as a result of microphase separation into a variety of ordered nanostructures, depending on the number of contiguous sequences (“blocks”) present and their sequential arrangement. These polymers are classified as multifunctional since they exhibit two or more different property sets during application. In this work, the focus is on bicomponent block copolymers composed of soft and hard segments arranged as linear triblock or higher-order multiblock copolymers and possessing the properties of a thermoplastic elastomer (TPE). Of particular interest are selectively-solvated TPEs, designated as TPE gels (TPEGs), with precisely- and composition-tunable properties. An important aspect of TPEs and their TPEG analogs is their elasticity, which reflects the ability of the soft block(s) to form a contiguous molecular network connected by dispersed microdomains composed of the hard block. Here, the origins of microphase separation and network formation in styrenic TPEs and TPEGs are explored, and experimental, theoretical, and simulation results are examined to elucidate chemistry-structure-property-processing (CSPP) relationships in these self-networking materials. Once such relationships are established, several unconventional technologies that can directly benefit from TPEGs, along with TPEGs fabricated from TPEs possessing different chemical moieties, are likewise considered.

Phase transition is a fundamental phenomenon in condensed matter physics, in which states of matter transform to each other with various critical behaviors under different conditions. The magnetic martensitic transformation features significant multi-caloric effects that benefit the solid-state cooling or heat pumping. Meanwhile, the electronic topological transition (ETT) driven by pressure has been rarely reported in martensitic systems. Here, the modulation effects of hydrostatic pressure on phase transitions in a magnetic martensitic alloy are reported. Owing to the huge volume expansion during the transition, the martensitic transition temperature is driven from 339 to 273 K by pressure within 1 GPa, resulting in highly tunable giant baro- and magneto-caloric effects (BCE and MCE) in a wide working temperature range. Interestingly, an ETT is further induced by pressure in the martensite phase, with a sudden drop of the measured saturation magnetization around 0.6 GPa. First-principles calculations reveal a sharp change in the density of states (DOS) due to the orbit shift around the Fermi level at the same pressure and reproduce the experimental observation of magnetization. Besides, the ETT is accompanied by remarkable changes in the lattice parameters and the unit-cell orthorhombicity. The study provides insight into pressure-modulated exotic phase-transition phenomena in magnetic martensitic systems.

The NaZn₁₃ type itinerant magnet LaFe_13−xSi_x has seen considerable interest due to its unique combination of large magnetocaloric effect and low hysteresis. Here, this alloy with a combination of magnetometry, bespoke microcalorimetry, and inelastic neutron scattering is investigated. Inelastic neutron scattering reveals the presence of broad quasielastic scattering that persists across the magnetic transition, which is attributed to spin fluctuations. In addition, a quasielastic peak is observed at Q = 0.52 Å⁻¹ for x = 1.2 that exists only in the paramagnetic state in proximity to the itinerant metamagnetic transition and argue that this indicates emergence of a hidden mag the netic phase that drives the first-order phase transition in this system.

Surface Interactions

The parallel use of different spectroscopic techniques demonstrates that the spin and electronic properties of vanadyl tetraphenylporphyrin molecular qubits are preserved when they form a monolayer on the Ag(100) surface. In article number 2300121, Lorenzo Poggini, Gianlorenzo Bussetti, Matteo Mannini and co-workers reveal how the molecules adhere to the surface with their porphyrin ring macrocycle aligned parallel to it, while the vanadyl group may point either upwards or downwards, resulting in differing levels of interaction strength with the surface. Artwork by Andrea Luigi Sorrentino, Università degli Studi di Firenze.