Advanced Physics Research最新文献

In article number 2300125, Zhiwei Guo, Hong Chen, and co-workers review the research into split-ring resonators (SRRs) and explore devices made from them. As a powerful platform to demonstrate abundant low-dimensional topology, SRRs can support novel functional photonic applications, including wireless power transfer, sensing, and switching. Finally, they provide an outlook on the potential challenges and opportunities of SRR-based devices combined with gauge field, non-Hermitian, and nonlinear physics.

Soft materials that convert light into mechanical energy can create new untethered strategies for actuating soft robotics. Yet, the available light-driven materials are often incompatible with standard fabrication in soft robotics and restricted to shapes (e.g., sheets) that have limited capability for 3D deformation; often laser or focused light is required for actuation. Here, to address these challenges, a straightforward method for synthesizing sunlight-responsive fluidic actuators from off-the-shelf silicone precursors capable of expanding in 3D is developed. A liquid phase and activated carbon as photothermal elements are constrained in the elastomer. Solar spectral light triggers a liquid–gas phase transition creating sufficient pressure to overcome the internal elastic stress and actuate the material. The fluidic actuation is characterized under varying light conditions reaching expansion cycle times between ≈20–500 s, strains of 28%, and actuation stress of ≈1.3 MPa in different experiments. The materials were then used to exemplarily drive a mechanical switch, a liquid dispensing soft pump, a valve, and a bending actuator. As the described materials are easy to produce in a 5 min synthesis by standard molding techniques, it is believed that they are a promising opportunity for embodied energy converters in environmentally powered soft robots that respond to sunlight.

The dimensionality of dynamic interfaces—domain walls (DWs) —is greatly influenced by symmetry and physical dimensions, irrespective of the microscopic details of the system. To address this fundamental question for the ferroelectric model system, the DW scaling criticality and dimensionality is investigated in ultrathin films of varied ferroelectric materials, compositions, and electrode–ferroelectric interfaces, grown on nominally flat and vicinal substrates. In spite of significant variations among ferroelectric systems, the observed prevalence of 1D DWs is consistent with a random bond disorder, elucidated through a scenario of 2D nucleation and growth-driven DW creep. These findings highlight the thickness size-dominated universal behavior of ferroelectric DWs, uncovering fascinating prospects for dimensionally engineered DW-based nanoelectronics.

With the giant magnetoresistance (GMR) effect serving as a vital component in modern spintronic technologies, researchers are dedicating significant efforts to improve the performance of GMR devices through material exploration and design optimization. However, traditional GMR measurement approaches are inefficient for comprehensive material and device optimization. This study proposes a high-throughput current-in-plane GMR measurement technique based on thermal imaging of Joule heating utilizing lock-in thermography (LIT). This LIT-based technique is advantageous for efficiently evaluating films with varying compositions and thickness gradients, which is crucial for ongoing material exploration and design optimization to enhance the GMR ratio. First, it is demonstrated that using CoFe/Cu multilayers, the simple Joule heating measurement based on LIT enables quantitative estimation of the GMR ratio. Then, to confirm the usefulness of the proposed method in high-throughput material screening, a case study is shown to investigate the GMR of CoCu-based granular films with a composition gradient. These techniques allow to determine the optimum composition with maximum GMR ratio using the single composition-gradient film and reveal Co₂₂Cu₇₈ as the optimal composition, yielding the largest GMR ratio among the reported polycrystalline CoCu-based granular films. This demonstration accelerates the material and structural optimization of GMR devices.

A 2 × 2 thermo-optic (TO) switch using dual topological photonic crystal nanobeam (PCN) cavities on the silicon-on-insulator (SOI) platform is proposed and experimentally demonstrated. A Fano resonance is observed due to the interference between the topological interface state of the 1D topological PCN cavity and the Fabry-Perot (F-P) cavity mode formed between the two facets of the finitely long nanobeam waveguide. Thanks to the sharp rising edge of the spectral response of the Fano resonance and the high confinement of light in the topological PCN cavities, a 2 × 2 TO switch is realized with short switching time and low power consumption. The measured switching power is only 1.55 mW, and the rising time and the falling time are 3 and 5.6 µs, respectively in the on-off switching experiments. To the best of the knowledge, this is the first time that a dual topological PCN structure is utilized to realize a high-speed and low-power TO switch, revealing the possibility of designing high-performance reconfigurable optical devices and networks using topological photonics.

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.

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.