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Abstract Photoacoustic imaging is a promising non-invasive functional imaging modality for fundamental research and clinical diagnosis. However, achieving capillary-level resolution, wide field-of-view, and high frame rates remains challenging. To address this, we propose a transparent ultrasonic transducer design using our developed transparent Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 crystals. Our fabrication technique incorporates quartz-glass-and-epoxy matching layers with low-resistance indium-tin-oxide electrodes through a brass-ring based structure, enabling a high frequency (28.5 MHz), wide bandwidth (78%), and enhanced pulse-echo sensitivity (2.5 V under 2-μJ pulse excitation). Our Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3-based transparent ultrasonic transducer demonstrates a four-fold enhancement in photoacoustic detection sensitivity when compared to the LiNbO3-based counterpart, leading to a 13 dB improvement of signal-to-noise ratio in microvascular photoacoustic imaging. This enables dynamic monitoring of mouse cerebral cortex microvasculature during seizures at 0.8 Hz frame rates over a 1.5 × 1.5 mm2 field-of-view. Our work paves the way for high-performance and compact photoacoustic imaging systems using advanced piezoelectric materials.

Abstract Re-poling of unexpected partially depoled piezoelectric materials conventionally needs to be first fully depoled through annealing above their Curie temperature to revive piezoelectric performances. Here, we investigated de-poling and re-poling of Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals under electric fields at room temperature. We found that alternating current electric fields with amplitudes near the coercive field at low frequencies (

Abstract Dielectric capacitors offer great potential for advanced electronics due to their high power densities, but their energy density still needs to be further improved. High-entropy strategy has emerged as an effective method for improving energy storage performance, however, discovering new high-entropy systems within a high-dimensional composition space is a daunting challenge for traditional trial-and-error experiments. Here, based on phase-field simulations and limited experimental data, we propose a generative learning approach to accelerate the discovery of high-entropy dielectrics in a practically infinite exploration space of over 1011 combinations. By encoding-decoding latent space regularities to facilitate data sampling and forward inference, we employ inverse design to screen out the most promising combinations via a ranking strategy. Through only 5 sets of targeted experiments, we successfully obtain a Bi(Mg0.5Ti0.5)O3-based high-entropy dielectric film with a significantly improved energy density of 156 J cm−3 at an electric field of 5104 kV cm−1, surpassing the pristine film by more than eight-fold. This work introduces an effective and innovative avenue for designing high-entropy dielectrics with drastically reduced experimental cycles, which could be also extended to expedite the design of other multicomponent material systems with desired properties.

Abstract Optical second harmonic generation (SHG) is a nonlinear optical effect widely used for nonlinear optical microscopy and laser frequency conversion. Closed-form analytical solution of the nonlinear optical responses is essential for evaluating materials whose optical properties are unknown a priori. A recent open-source code, ♯SHAARP.si, can provide such closed form solutions for crystals with arbitrary symmetries, orientations, and anisotropic properties at a single interface. However, optical components are often in the form of slabs, thin films on substrates, and multilayer heterostructures with multiple reflections of both the fundamental and up to ten different SHG waves at each interface, adding significant complexity. Many approximations have therefore been employed in the existing analytical approaches, such as slowly varying approximation, weak reflection of the nonlinear polarization, transparent medium, high crystallographic symmetry, Kleinman symmetry, easy crystal orientation along a high-symmetry direction, phase matching conditions and negligible interference among nonlinear waves, which may lead to large errors in the reported material properties. To avoid these approximations, we have developed an open-source package named Second Harmonic Analysis of Anisotropic Rotational Polarimetry in Multilayers (♯SHAARP.ml). The reliability and accuracy are established by experimentally benchmarking with both the SHG polarimetry and Maker fringes using standard and commonly used nonlinear optical materials as well as twisted 2-dimensional heterostructures.

Abstract There is tremendous interest in employing collective excitations of the lattice, spin, charge, and orbitals to tune strongly correlated electronic phenomena. We report such an effect in a ruthenate, Ca3Ru2O7, where two phonons with strong electron-phonon coupling modulate the electronic pseudogap as well as mediate charge and spin density wave fluctuations. Combining temperature-dependent Raman spectroscopy with density functional theory reveals two phonons, B 2 P and B 2 M, that are strongly coupled to electrons and whose scattering intensities respectively dominate in the pseudogap versus the metallic phases. The B 2 P squeezes the octahedra along the out of plane c-axis, while the B 2 M elongates it, thus modulating the Ru 4d orbital splitting and the bandwidth of the in-plane electron hopping; Thus, B 2 P opens the pseudogap, while B 2 M closes it. Moreover, the B 2 phonons mediate incoherent charge and spin density wave fluctuations, as evidenced by changes in the background electronic Raman scattering that exhibit unique symmetry signatures. The polar order breaks inversion symmetry, enabling infrared activity of these phonons, paving the way for coherent light-driven control of electronic transport.

Abstract Solomon rings, upholding the symbol of wisdom with profound historical roots, were widely used as decorations in ancient architecture and clothing. However, it was only recently discovered that such topological structures can be formed by self-organization in biological/chemical molecules, liquid crystals, etc. Here, we report the observation of polar Solomon rings in a ferroelectric nanocrystal, which consist of two intertwined vortices and are mathematically equivalent to a $${4}_{1}^{2}$$ 4 1 2 link in topology. By combining piezoresponse force microscopy observations and phase-field simulations, we demonstrate the reversible switching between polar Solomon rings and vertex textures by an electric field. The two types of topological polar textures exhibit distinct absorption of terahertz infrared waves, which can be exploited in infrared displays with a nanoscale resolution. Our study establishes, both experimentally and computationally, the existence and electrical manipulation of polar Solomon rings, a new form of topological polar structures that may provide a simple way for fast, robust, and high-resolution optoelectronic devices.

Polar skyrmions are particle-like objects consisted of swirling electric dipoles that hold promise for next generation nanodevices. Here, the authors explore the strain-induced transition from skyrmions to merons using electron imaging methods.

Understanding high piezoelectricity in relaxors is challenging due to the heterogeneous structures. Here, the authors demonstrate that the competing local polar order-disorder state with balanced length and direction randomness is the key.

Abstract Multifunctionality as a paradigm requires materials exhibiting multiple superior properties. Integrating second‐order optical nonlinearity and large bandgap with piezoelectricity can, for example, enable broadband, strain‐tunable photonics. Though very different phenomena at distinct frequencies, both second‐order optical nonlinearity and piezoelectricity are third‐rank polar tensors present only in acentric crystal structures. However, simultaneously enhancing both phenomena is highly challenging since it involves competing effects with tradeoffs. Recently, a large switchable ferroelectric polarization of ≈80 μC cm−2 was reported in Zn1‐xMgxO films. Here, ferroelectric Zn1‐xMgxO is demonstrated to be a platform that hosts simultaneously a 30% increase in the electronic bandgap, a 50% enhancement in the second harmonic generation (SHG) coefficients, and a near 200% improvement in the piezoelectric coefficients over pure ZnO. These enhancements are shown to be due to a 400% increase in the electronic anharmonicity and a ≈200% decrease in the ionic anharmonicity with Mg substitution. Precisely controllable periodic ferroelectric domain gratings are demonstrated down to 800 nm domain width, enabling ultraviolet quasi‐phase‐matched optical harmonic generation as well as domain‐engineered piezoelectric devices.

Abstract Electric-dipole optical second harmonic generation (SHG) is a second-order nonlinear process that is widely used as a sensitive probe to detect broken inversion symmetry and local polar order. Analytical modeling of the SHG polarimetry of a nonlinear optical material is essential to extract its point group symmetry and the absolute nonlinear susceptibilities. Current literature on SHG analysis involves numerous approximations and a wide range of (in)accuracies. We have developed an open-source package called the Second Harmonic Analysis of Anisotropic Rotational Polarimetry (♯SHAARP.si) which derives analytical and numerical solutions of reflection SHG polarimetry from a single interface (.si) for bulk homogeneous crystals with arbitrary symmetry group, arbitrary crystal orientation, complex and anisotropic linear dielectric tensor with frequency dispersion, a general SHG tensor and arbitrary light polarization. ♯SHAARP.si enables accurate modeling of polarimetry measurements in reflection geometry from highly absorbing crystals or wedge-shaped transparent crystals. The package is extendable to multiple interfaces.

Abstract Reproducible wafer-scale growth of two-dimensional (2D) materials using the Chemical Vapor Deposition (CVD) process with precise control over their properties is challenging due to a lack of understanding of the growth mechanisms spanning over several length scales and sensitivity of the synthesis to subtle changes in growth conditions. A multiscale computational framework coupling Computational Fluid Dynamics (CFD), Phase-Field (PF), and reactive Molecular Dynamics (MD) was developed – called the CPM model – and experimentally verified. Correlation between theoretical predictions and thorough experimental measurements for a Metal-Organic CVD (MOCVD)-grown WSe2 model material revealed the full power of this computational approach. Large-area uniform 2D materials are synthesized via MOCVD, guided by computational analyses. The developed computational framework provides the foundation for guiding the synthesis of wafer-scale 2D materials with precise control over the coverage, morphology, and properties, a critical capability for fabricating electronic, optoelectronic, and quantum computing devices.

Despite various known topological polar structures, the dynamic property of isolated ones is still poorly understood. Here, the authors show the controlled nucleation and ability to move of isolated three-fold vertices under an applied electric field.

The piezoelectricity of PVDF composites is mainly determined by the crystalline phases and spontaneous polarization. Here, the authors propose a Ti3C2Tx anchoring method to modulate the molecular interactions and conformation of polymer matrix.

A central paradigm of nonequilibrium physics concerns the dynamics of heterogeneity and disorder, impacting processes ranging from the behavior of glasses to the emergent functionality of active matter. Understanding these complex mesoscopic systems requires probing the microscopic trajectories associated with irreversible processes, the role of fluctuations and entropy growth, and the timescales on which nonequilibrium responses are ultimately maintained. Approaches that illuminate these processes in model systems may enable a more general understanding of other heterogeneous nonequilibrium phenomena, and potentially define ultimate speed and energy cost limits for information processing technologies. Here, we apply ultrafast single-shot X-ray photon correlation spectroscopy to resolve the nonequilibrium, heterogeneous, and irreversible mesoscale dynamics during a light-induced phase transition in a (PbTiO3)16/(SrTiO3)16 superlattice. Such ferroelectric superlattice systems are a useful platform to study phase transitions and topological dynamics due to their high degree of tunability. This provides an approach for capturing the nucleation of the light-induced phase, the formation of transient mesoscale defects at the boundaries of the nuclei, and the eventual annihilation of these defects, even in systems with complex polarization topologies. We identify a nonequilibrium correlation response spanning >10 orders of magnitude in timescales, with multistep behavior similar to the plateaus observed in supercooled liquids and glasses. We further show how the observed time-dependent long-time correlations can be understood in terms of stochastic and non-Markovian dynamics of domain walls, encoded in waiting-time distributions with power-law tails. This work defines possibilities for probing the nonequilibrium and correlated dynamics of disordered and heterogeneous media. [ABSTRACT FROM AUTHOR]

Ferroelectric domain walls have been extensively explored for nanoelectronics, but the logic devices are still challenging. Here, the authors propose programmable logic gates and circuits based on electric-field controllable conductive domain walls.

Abstract Many functional and quantum materials derive their functionality from the responses of both their electronic and lattice subsystems to thermal, electric, and mechanical stimuli or light. Here we propose a dynamical phase-field model for predicting and modeling the dynamics of simultaneous electronic and structural processes and the accompanying mesoscale pattern evolution under static or ultrafast external stimuli. As an illustrative example of application, we study the transient dynamic response of ferroelectric domain walls excited by an ultrafast above-bandgap light pulse. We discover a two-stage relaxational electronic carrier evolution and a structural evolution containing multiple oscillational and relaxational components across picosecond to nanosecond timescales. The phase-field model offers a general theoretical framework which can be applied to a wide range of functional and quantum materials with interactive electronic and lattice orders and phase transitions to understand, predict, and manipulate their ultrafast dynamics and rich mesoscale evolution dynamics of domains, domain walls, and charges.

Abstract With its extremely strong capability of data analysis, machine learning has shown versatile potential in the revolution of the materials research paradigm. Here, taking dielectric capacitors and lithium‐ion batteries as two representative examples, we review substantial advances of machine learning in the research and development of energy storage materials. First, a thorough discussion of the machine learning framework in materials science is presented. Then, we summarize the applications of machine learning from three aspects, including discovering and designing novel materials, enriching theoretical simulations, and assisting experimentation and characterization. Finally, a brief outlook is highlighted to spark more insights on the innovative implementation of machine learning in materials science.

Abstract Understanding the electromechanical breakdown mechanisms of polycrystalline ceramics is critical to texture engineering for high‐energy‐density dielectric ceramics. Here, an electromechanical breakdown model is developed to fundamentally understand the electrostrictive effect on the breakdown behavior of textured ceramics. Taking the Na0.5Bi0.5TiO3‐Sr0.7Bi0.2TiO3 ceramic as an example, it is found that the breakdown process significantly depends on the local electric/strain energy distributions in polycrystalline ceramics, and reasonable texture design could greatly alleviate electromechanical breakdown. Then, high‐throughput simulations are performed to establish the mapping relationship between the breakdown strength and different intrinsic/extrinsic variables. Finally, machine learning is conducted on the database from the high‐throughput simulations to obtain the mathematical expression for semi‐quantitatively predicting the breakdown strength, based on which some basic principles of texture design are proposed. The present work provides a computational understanding of the electromechanical breakdown behavior in textured ceramics and is expected to stimulate more theoretical and experimental efforts in designing textured ceramics with reliable electromechanical performances.

In ferroelectric heterostructures, the interaction between intrinsic polarization and the electric field generates a rich set of localized electrical properties. The local electric field is determined by several connected factors, including the charge distribution of individual unit cells, the interfacial electromechanical boundary conditions, and chemical composition of the interfaces. However, especially in ferroelectric perovskites, a complete description of the local electric field across micro-, nano-, and atomic-length scales is missing. Here, by applying four-dimensional scanning transmission electron microscopy (4D STEM) with multiple probe sizes matching the size of structural features, we directly image the electric field of polarization vortices in (PbTiO3)16/(SrTiO3)16 superlattices and reveal different electric field configurations corresponding to the atomic scale electronic ordering and the nanoscale boundary conditions. The separability of two different fields probed by 4D STEM offers the possibility to reveal how each contributes to the electronic properties of the film.

Reducing the switching energy of ferroelectric films remains an important goal. Here, the authors elucidate the fundamental role of lattice dynamics in ferroelectric switching on both freestanding BiFeO3 membranes and films clamped to a substrate.

Abstract Although multiple oxide-based solid electrolyte materials with intrinsically high ionic conductivities have emerged, practical processing and synthesis routes introduce grain boundaries and other interfaces that can perturb primary conduction channels. To directly probe these effects, we demonstrate an efficient and general mesoscopic computational method capable of predicting effective ionic conductivity through a complex polycrystalline oxide-based solid electrolyte microstructure without relying on simplified equivalent circuit description. We parameterize the framework for Li7-x La3Zr2O12 (LLZO) garnet solid electrolyte by combining synthetic microstructures from phase-field simulations with diffusivities from molecular dynamics simulations of ordered and disordered systems. Systematically designed simulations reveal an interdependence between atomistic and mesoscopic microstructural impacts on the effective ionic conductivity of polycrystalline LLZO, quantified by newly defined metrics that characterize the complex ionic transport mechanism. Our results provide fundamental understanding of the physical origins of the reported variability in ionic conductivities based on an extensive analysis of literature data, while simultaneously outlining practical design guidance for achieving desired ionic transport properties based on conditions for which sensitivity to microstructural features is highest. Additional implications of our results are discussed, including a possible connection between ion conduction behavior and dendrite formation.

Abstract Solid-state refrigeration which is environmentally benign has attracted considerable attention. Mechanocaloric (mC) materials, in which the phase transitions can be induced by mechanical stresses, represent one of the most promising types of solid-state caloric materials. Herein, we have developed a thermodynamic phenomenological model and predicted extraordinarily large elastocaloric (eC) strengths for the (111)-oriented metal-free perovskite ferroelectric [MDABCO](NH4)I3 thin-films. The predicted room temperature isothermal eC ΔS eC/Δσ (eC entropy change under unit stress change) and adiabatic eC ΔT eC/Δσ (eC temperature change under unit stress change) for [MDABCO](NH4)I3 are −60.0 J K−1 kg−1 GPa−1 and 17.9 K GPa−1, respectively, which are 20 times higher than the traditional ferroelectric oxides such as BaTiO3 thin films. We have also demonstrated that the eC performance can be improved by reducing the Young’s modulus or enhancing the thermal expansion coefficient (which could be realized through chemical doping, etc.). We expect these discoveries to spur further interest in the potential applications of metal-free organic ferroelectrics materials towards next-generation eC refrigeration devices.

Abstract Addressing microstructure-property relations of polymer nanocomposites is vital for designing advanced dielectrics for electrostatic energy storage. Here, we develop an integrated phase-field model to simulate the dielectric response, charge transport, and breakdown process of polymer nanocomposites. Subsequently, based on 6615 high-throughput calculation results, a machine learning strategy is schemed to evaluate the capability of energy storage. We find that parallel perovskite nanosheets prefer to block and then drive charges to migrate along with the interfaces in x-y plane, which could significantly improve the breakdown strength of polymer nanocomposites. To verify our predictions, we fabricate a polymer nanocomposite P(VDF-HFP)/Ca2Nb3O10, whose highest discharged energy density almost doubles to 35.9 J cm−3 compared with the pristine polymer, mainly benefit from the improved breakdown strength of 853 MV m−1. This work opens a horizon to exploit the great potential of 2D perovskite nanosheets for a wide range of applications of flexible dielectrics with the requirement of high voltage endurance.

Ferroelectric topological defects show emerging exotic physical properties, which are important for future nanoelectronic devices. Here, the authors demonstrate conductive metallic conduction channels in two types of topological defects, namely vortex and center cores.

Abstract Metal oxide-based Resistive Random-Access Memory (RRAM) exhibits multiple resistance states, arising from the activation/deactivation of a conductive filament (CF) inside a switching layer. Understanding CF formation kinetics is critical to achieving optimal functionality of RRAM. Here a phase-field model is developed, based on materials properties determined by ab initio calculations, to investigate the role of electrical bias, heat transport and defect-induced Vegard strain in the resistive switching behavior, using MO2−x systems such as HfO2−x as a prototypical model system. It successfully captures the CF formation and resultant bipolar resistive switching characteristics. High-throughput simulations are performed for RRAMs with different material parameters to establish a dataset, based on which a compressed-sensing machine learning is conducted to derive interpretable analytical models for device performance (current on/off ratio and switching time) metrics in terms of key material parameters (electrical and thermal conductivities, Vegard strain coefficients). These analytical models reveal that optimal performance (i.e., high current on/off ratio and low switching time) can be achieved in materials with a low Lorenz number, a fundamental material constant. This work provides a fundamental understanding to the resistive switching in RRAM and demonstrates a computational data-driven methodology of materials selection for improved RRAM performance, which can also be applied to other electro-thermo-mechanical systems.

Understanding the interface effect in dielectric nanocomposites is crucial to the enhancement of their performance. In this work, a data-driven interface design strategy based on high-throughput phase-field simulations is developed to study the interface effect and then optimize the permittivity and breakdown strength of nanocomposites. Here, we use two microscopic features that are closely related to the macroscopic dielectric properties, the thickness and permittivity of the interface phases, to evaluate the role of interfaces in experimental configuration, and thus provide quantitative design schemes for the interfacial phases. Taking the polyvinyl difluoride (PVDF)BaTiO3 nanocomposite as an example, the calculation results demonstrate that the interfacial polarization could account for up to 83.6% of the increase in the experimentally measured effective permittivity of the nanocomposite. Based on the interface optimized strategy, a maximum enhancement of ∼156% in the energy density could be achieved by introducing an interface phase with d/r = 0.55 and εinterface/εfiller=0.036, compared to the pristine nanocomposite. Overall, the present work not only provides fundamental understanding of the interface effect in dielectric nanocomposites, but also establishes a powerful data-driven interface design framework for such materials that could also be easily generalized and applied to study interface issues in other functional nanocomposites, such as solid electrolytes and thermoelectrics.

Manipulating the electric state of large band gap dielectrics without any damage is quite challenging. Here, the authors demonstrate by mechanically introducing strain gradients that large electric fields are generated via flexoelectric interactions, resulting in a reversible Zener breakdown in SrTiO3, changing the resistivity by 108.

Abstract Piezoelectric nanocomposites with oxide fillers in a polymer matrix combine the merit of high piezoelectric response of the oxides and flexibility as well as biocompatibility of the polymers. Understanding the role of the choice of materials and the filler‐matrix architecture is critical to achieving desired functionality of a composite towards applications in flexible electronics and energy harvest devices. Herein, a high‐throughput phase‐field simulation is conducted to systematically reveal the influence of morphology and spatial orientation of an oxide filler on the piezoelectric, mechanical, and dielectric properties of the piezoelectric nanocomposites. It is discovered that with a constant filler volume fraction, a composite composed of vertical pillars exhibits superior piezoelectric response and electromechanical coupling coefficient as compared to the other geometric configurations. An analytical regression is established from a linear regression‐based machine learning model, which can be employed to predict the performance of nanocomposites filled with oxides with a given set of piezoelectric coefficient, dielectric permittivity, and stiffness. This work not only sheds light on the fundamental mechanism of piezoelectric nanocomposites, but also offers a promising material design strategy for developing high‐performance polymer/inorganic oxide composite‐based wearable electronics.

The influence of interfacial energy anisotropy on dendrite morphology is still not well understood. We investigated the dendrite morphology and solute segregation in Al-Zn alloys using the phase-field method. We observed typical and atypical dendrite orientation transition and three types of dendrite morphology “Christmas tree dendrite”, “seaweed dendrite” and “butterfly dendrite” depending on the anisotropic interfacial energy. Two types of dendrite may undergo the so called-“smooth dendrite orientation transition”, which produces a large amount of solute segregation holes in 〈100〉 dendrites, and liquid grooves in 〈110〉 seaweed and butterfly patterns, thus may significantly impact the mechanical properties of castings. We identified a strong correlation between supersaturation and the formation of liquid holes and liquid grooves as well as the degree of solute segregation. We also proposed that the interfacial energy anisotropy can be related with Zn content by discussing the anisotropic Young’s modulus and experimental pattern of Al-Zn alloys. The inducement of anisotropy and the quantitative relationship between interfacial energy anisotropy, Zn concentration, elastic anisotropy and dendrite orientation deserves attention.

Chimonanthus of Calycanthaceae is a small endemic genus in China, with unusual winter-blooming sweet flowers widely cultivated for ornamentals and medicinal uses. The evolution of Chimonanthus plastomes and its phylogenetic relationships remain unresolved due to limited availability of genetic resources. Here, we report fully assembled and annotated chloroplast genomes of five Chimonanthus species. The chloroplast genomes of the genus (size range 153,010 – 153,299 bp) reveal high similarities in gene content, gene order, GC content, codon usage, amino acid frequency, simple sequence repeats, oligonucleotide repeats, synonymous and non-synonymous substitutions, and transition and transversion substitutions. Signatures of positive selection are detected in atpF and rpoB genes in C. campanulatus. The correlations among substitutions, InDels, and oligonucleotide repeats reveal weak to strong correlations in distantly related species at the intergeneric levels, and very weak to weak correlations among closely related Chimonanthus species. Chloroplast genomes are used to reconstruct a well-resolved phylogenetic tree, which supports the monophyly of Chimonanthus. Within Chimonanthus, C. praecox and C. campanulatus form one clade, while C. grammatus, C. salicifolius, C. zhejiangensis, and C. nitens constitute another clade. Chimonanthus nitens appears paraphyletic and is closely related to C. salicifolius and C. zhejiangensis, suggesting the need to reevaluate the species delimitation of C. nitens. Chimonanthus and Calycanthus diverged in mid-Oligocene; the radiation of extant Chimonanthus species was dated to the mid-Miocene, while C. grammatus diverged from other Chimonanthus species in the late Miocene. C. salicifolius, C. nitens(a), and C. zhejiangensis are inferred to have diverged in the Pleistocene of the Quaternary period, suggesting recent speciation of a relict lineage in the subtropical forest regions in eastern China. This study provides important insights into the chloroplast genome features and evolutionary history of Chimonanthus and family Calycanthaceae.

The fundamental plane of black hole activity is a very important tool to study accretion and jets. However, we found that the SEDs of AGNs and XRBs are different in the 2–10 keV energy band, and it seems inappropriate to use 2–10 keV X-ray luminosities to study the fundamental plane. In this work, we use the luminosity near the peak of the blackbody radiation of the active galactic nuclei and black hole binaries to replace the 2–10 keV luminosity. We re-explore the fundamental plane of black hole activity by using the 2500 A ˚ luminosity as the peak luminosity of the blackbody radiation of AGNs and 1 keV luminosity as the peak luminosity of the blackbody radiation of XRBs. We compile samples of black hole binaries and active galactic nuclei with luminosity near the peak luminosity of blackbody radiation and study the fundamental plane between radio luminosity ( L R ), the peak luminosity of blackbody radiation ( L peak ), and black hole mass ( M BH ). We find that the radio–peak luminosity correlations are L 5 GHz / L Edd ∝ (L 2500 A ˚ / L Edd) 1.55 and L 5 GHz / L Edd ∝ (L 1 keV / L Edd) 1.53 for AGN and XRB, respectively, in the radiatively efficient sample, and L 5 GHz / L Edd ∝ (L 2500 A ˚ / L Edd) 0.48 and L 5 GHz / L Edd ∝ (L 1 keV / L Edd) 0.53 in the radiatively inefficient sample, respectively. Based on the similarities in radio–peak correlations, we further propose a fundamental plane in radio luminosity, the peak luminosity of blackbody radiation, and black hole mass, which is radiatively efficient: log L 5 GHz = 1. 57 − 0.01 + 0.01 log L peak − 0. 32 − 0.16 + 0.16 log M BH − 27. 73 − 0.34 + 0.34 with a scatter of σ R = 0.48 dex, and radiatively inefficient: log L 5 GHz = 0. 45 − 0.01 + 0.01 log L peak + 0. 91 − 0.10 + 0.12 log M BH + 12. 58 − 0.38 + 0.38 with a scatter of σ R = 0.63 dex. Our results are similar to those of previous studies on the fundamental plane for radiatively efficient and radiatively inefficient black hole activity. However, our results exhibit a smaller scatter, so when using the same part of blackbody radiation (i.e., the peak luminosity of the blackbody radiation), the fundamental plane becomes a little bit tighter. [ABSTRACT FROM AUTHOR]

The scale and dimensionality of imaging data means information is commonly overlooked. Here, using recurrent neural networks we understand temporal dependencies in hyperspectral imagery, enabling the observation of differences in ferroelectric switching mechanisms in PbZr0.2Ti0.8O3 thin films due to formation of charged domain walls.

Clamping effects in ferroelestastic thin films limits their usefulness for applications such as sensitive mechanical sensors. Here, the authors report on non-local mechanical force induced switching in PbTiO3 thin films by tuning the material to a state of nearly energetically degenerate co-existing domains.

Abstract Background Apogamy is a unique asexual reproduction in the ferns, in which somatic cells of gametophytes go through dedifferentiation and then differentiate into haploid sporophytes bypassing fertilization. Restricted to the lack of genomic information, molecular mechanisms of apogamy have remained unclear. Comparative transcriptome analysis was conducted at six stages between sexual reproduction and apogamy in the fern Adiantum reniforme var. sinense, in an effort to identify genes and pathways that might initiate the asexual reproduction. Results Approximately 928 million high-quality clean reads were assembled into 264,791 unigenes with an average length of 615 bp. A total of 147,865 (55.84%) unigenes were successfully annotated. Differential genes expression analysis indicated that transcriptional regulation was more active in the early stage of apogamy compared to sexual reproduction. Further comparative analysis of the enriched pathways between the early stages of the two reproductive modes demonstrated that starch and sucrose metabolism pathway responsible for cell wall was only significantly enriched in asexual embryonic cell initiation. Furthermore, regulation of plant hormone related genes was more vigorous in apogamy initiation. Conclusion These findings would be useful for revealing the initiation of apogamy and further understanding of the mechanisms related to asexual reproduction.

Polymer dielectrics are promising for high-density energy storage but dielectric breakdown is poorly understood. Here, a phase-field model is developed to investigate electric, thermal, and mechanical effects in the breakdown process for a range of polymer dielectrics, and analytical expression for breakdown strength is provided by machine learning.

Abstract Flexoelectricity is an electromechanical coupling effect in which electric polarization is generated by a strain gradient. In this investigation, a potassium sodium niobite/poly(vinylidene fluoride‐trifluoroethylene) (KNN/PVDF‐TrFE)‐based nanocomposite is fabricated, and the flexoelectric effect is used to enhance the photovoltaic current (Ipv) in the nanocomposite. It is found that both a pyroelectric current and photovoltaic current can be generated simultaneously in a light illumination process. However, the photovoltaic current (Ipv) in this process contributes ≈85% of the total current. When assessing the effect of flexoelectricity with a curvature of 1/20, the Ipv of the curved KNN/PVDF‐TrFE (20%) (K/P‐20) composite increased by ≈13.9% compared to that of the flat K/P‐20 nanocomposite. Similarly, at a curvature of 1/20, the Ipv of the K/P‐20 nanocomposite is 71.6% higher than that of the PVDF‐TrFE film. However, the photovoltaic effect induced by flexoelectricity is much higher than the increased polarization from flexoelectricity, so this effect is called as the flexophotovoltaic effect. Furthermore, the calculated energy conversion efficiency of the K/P‐20 film is 0.017%, which is comparable to the previous research result. This investigation shows great promise for PVDF‐based nanocomposites in ferroelectric memory device applications.

Flexoelectricity exists in every dielectric material exposed to a strain gradient and is enhanced at the nanoscale. However, precisely determining flexoelectric coupling parameters at the nanoscale is challenging, but has been overcome here by measuring the current across a tunnel junction.

Deterministic switching of a magnetic vortex with an electric field is challenging because electric fields cannot break time-reversal symmetry. Here we demonstrate, using phase-field simulations, a deterministic switching of the vortex chirality in a triangle-shaped nanomagnet by applying an electric field to its underlying ferroelectric layer. The nanomagnet is juxtaposed with an overlying antiferromagnetic layer to acquire an exchange bias from their interface. The simulations show that such deterministic electrically-driven magnetic vortex chirality switching is enabled by a synergistic effect of the electric-field-induced strain from the ferroelectric, the three-fold in-plane shape anisotropy of the nanomagnet, and the exchange-bias field.

Controlling ferroelectric polarization is conventionally achieved by applying electric fields, mechanical force or similar. Here reversible switching of the bulk polarization of a BiFeO3 thin film is demonstrated by pattering aqueous solution on to the surface enabling large-scale switching.

The relationship between Li-ion concentration and Li deposition remains an issue to be addressed. Here the authors show that stimulated Raman scattering microscopy offers insight into the concentration evolution and its impact on the dendrite growth, which is not possible by existing techniques.