Tunable Magnetism in Atomically Thin Itinerant Antiferromagnet with Room-Temperature Ferromagnetic Order.

Addressing the need for modulated spin configurations is crucial, as they serve as the foundational building blocks for next-generation spintronics, particularly in atomically thin structures and at room temperature. In this work, we realize intrinsic ferromagnetism in monolayer flakes and tunable ferro-/antiferromagnetism in (Fe0.56Co0.44)5GeTe2 antiferromagnets. Remarkably, the ferromagnetic ordering (≥1 L) and antiferromagnetic ordering (≥4 L) remain discernible up to room temperature. The TC (∼310 K) of the monolayer flakes sets a record high for known exfoliated monolayer van der Waals magnets. Within the framework of A-type antiferromagnetism, a notable odd-even layer-number effect at elevated temperatures (T = 150 K) is observed. Of particular interest is the strong ferromagnetic order in even-layer flakes at low temperatures. The intricate interplay among magnetic field strength, layer number, and temperature gives rise to a diverse array of phenomena, holding promise not only for new physics but also for practical applications.

The Coexistence of Superconductivity and Topological Order in Van der Waals InNbS2.

The research on systems with coexistence of superconductivity and nontrivial band topology has attracted widespread attention. However, the limited availability of material platforms severely hinders the research progress. Here, it reports the first experimental synthesis and measurement of high-quality single crystal van der Waals transition-metal dichalcogenide InNbS2 , revealing it as a topological nodal line semimetal with coexisting superconductivity. The temperature-dependent measurements of magnetization susceptibility and electrical transport show that InNbS2 is a type-II superconductor with a transition temperature Tc of 6 K. First-principles calculations predict multiple topological nodal ring states close to the Fermi level in the presence of spin-orbit coupling. Similar features are also observed in the as-synthesized BiNbS2 and PbNbS2 samples. This work provides new material platforms ANbS2 (A = In, Bi, and Pb) and uncovers their intriguing potential for exploring the interplay between superconductivity and band topology.

Unconventional Magnetic and Magneto-Transport Properties in Quasi-2D Ni0.28TaSeS Single Crystal.

Van der Waals (vdW) magnetic materials have broad application prospects in next-generation spintronics. Inserting magnetic elements into nonmagnetic vdW materials can introduce magnetism and enhance various transport properties. Herein, the unconventional magnetic and magneto-transport phenomena is reported in Ni0.28TaSeS crystal by intercalating Ni atoms into nonmagnetic 2H-TaSeS matrix. Magnetic characterization reveals a canted magnetic structure in Ni0.28TaSeS, which results in an antiferromagnetic (AFM) order along the c-axis and a ferromagnetic (FM) moment in the ab-plane. The presence of spin-flop (SF) behavior can also be attributed to the canted magnetic structure. Temperature-dependent resistivity exhibits a metallic behavior with an abrupt decrease corresponding to the magnetic transition. Magneto-transport measurements demonstrate a positive magnetoresistance (MR) with a plateau that is different from conventional magnetic materials. The field-dependent Hall signal exhibits nonlinear field dependence when the material is in magnetically ordered state. These unconventional magneto-transport behaviors are attributed to the field-induced formation of a complex spin texture in Ni0.28TaSeS. In addition, it further investigated the angle dependence of MR and observed an unusual fourfold anisotropic magnetoresistance (AMR) effect. This work inspires future research on spintronic devices utilizing magnetic atom-intercalated quasi-2D materials.

Enhanced ferromagnetic properties achieved by F-doping in BaFe1-xMnxO3-δ.

Tailoring the crystal structure, spin, and charge state of perovskite oxides through fluorine ion doping is an attractive and effective strategy, which could significantly modify the physical and chemical properties of base oxides. Here, BaFe1-xMnxO3-δ (x = 0, 0.1, 0.2, 0.3) and BaFe1-xMnxO2.9-δF0.1 (x = 0.1, 0.2, 0.3), belonging to 6H-type BaFeO3-δ, are prepared and investigated to evaluate the impact of F- doping. The distortion of crystal structure and the reduced average valence of Mn and Fe confirm the preference for F- substitution in the hexagonal layer, which are found as the key factors for the improved magnetic properties, including ferromagnetic ordering temperature, coercive force, and remanent magnetization. Moreover, the valence reduction of B-site ions and the increased resistance distinctly indicate the expense of electron hole via fluorine doping. This work describes the adjustment of crystal structure, electronic configuration, and ferromagnetic performance by simple F- doping, which provides a prospect for practical magnetic materials.

MiR-124 synergism with ELAVL3 enhances target gene expression to promote neuronal maturity.

Neuron-enriched microRNAs (miRNAs), miR-9/9* and miR-124 (miR-9/9*-124), direct cell fate switching of human fibroblasts to neurons when ectopically expressed by repressing antineurogenic genes. How these miRNAs function after the repression of fibroblast genes for neuronal fate remains unclear. Here, we identified targets of miR-9/9*-124 as reprogramming cells activate the neuronal program and reveal the role of miR-124 that directly promotes the expression of its target genes associated with neuronal development and function. The mode of miR-124 as a positive regulator is determined by the binding of both AGO and a neuron-enriched RNA-binding protein, ELAVL3, to target transcripts. Although existing literature indicates that miRNA-ELAVL family protein interaction can result in either target gene up-regulation or down-regulation in a context-dependent manner, we specifically identified neuronal ELAVL3 as the driver for miR-124 target gene up-regulation in neurons. In primary human neurons, repressing miR-124 and ELAVL3 led to the down-regulation of genes involved in neuronal function and process outgrowth and cellular phenotypes of reduced inward currents and neurite outgrowth. Our results highlight the synergistic role between miR-124 and RNA-binding proteins to promote target gene regulation and neuronal function.

Ferromagnetism above Room Temperature in Two Intrinsic van der Waals Magnets with Large Coercivity.

The emergence of two-dimensional (2D) van der Waals (vdW) magnets provides a broad platform for studying the magnetic properties of low-dimensional materials in condensed matter physics. However, the intrinsic ferromagnetism of 2D materials is mostly observed below room temperature, and most of them are soft ferromagnetic materials. Here, we report two intrinsic ferromagnetic vdW materials with Curie temperatures (TC) above room temperature, MnSiTe3 (TC ∼ 378 K) and MnGeTe3 (TC ∼ 349 K). Moreover, MnSiTe3 exhibits a large coercivity (HC) at room temperature with an unprecedented HC of 1450 Oe, which is an increase of nearly 500% compared to the reported room-temperature vdW ferromagnets. The discovery of these two materials fills the gap of vdW room-temperature hard ferromagnets, providing a broad platform and possibilities for future research on low-dimensional spin electronic device applications.

Cascade bunch focusing on chip using terahertz pulses to drive prism arrays.

The dielectric laser accelerator (DLA) is a promising candidate for next-generation table-top and even on-chip particle accelerators. Long-range focusing of a tiny-size electron bunch on chip is crucial for the practical applications of DLA, which has been a challenge. Here we propose a bunch focusing scheme, which uses a pair of readily available few-cycle terahertz (THz) pulses to drive an array of millimeter-scale prisms via the inverse Cherenkov effect. The THz pulses are reflected and refracted multiple times through the prism arrays, synchronizing with and periodically focusing the electron bunch along the bunch channel. Cascade bunch-focusing is realized by making the electromagnetic field phase experienced by electrons in each stage of the array, that is, the synchronous phase, in the focusing phase region. The focusing strength can be adjusted via changing the synchronous phase and THz field intensity, optimization of which will sustain the stable bunch transportation in a tiny-size bunch channel on chip. This bunch-focusing scheme sets a base for developing a long-acceleration-range and high-gain DLA.

Few-Layer Fullerene Network for Photocatalytic Pure Water Splitting into H2 and H2 O2.

A few-layer fullerene network possesses several advantageous characteristics, including a large surface area, abundant active sites, high charge mobility, and an appropriate band gap and band edge for solar water splitting. Herein, we report for the first time that the few-layer fullerene network shows interesting photocatalytic performance in pure water splitting into H2 and H2 O2 in the absence of any sacrificial reagents. Under optimal conditions, the H2 and H2 O2 evolution rates can reach 91 and 116 µmol g-1 h-1 , respectively, with good stability. This work demonstrates the novel application of the few-layer fullerene network in the field of energy conversion.

Surface Self-Assembly Protonation Triggering Triple-Conductive Heterostructure with Highly Enhanced Oxygen Reduction for Protonic Ceramic Fuel Cells.

Triple-conducting (H+ /O2- /e- ) cathodes are a vital constituent of practical protonic ceramic fuel cells. However, seeking new candidates has remained a grand challenge on account of the limited material system. Though triple conduction can be achieved by mechanically mixing powders uniformly consisting of oxygen ion-electron and proton conductors, the catalytic activity and durability are still restricted. By leveraging this fact, a highly efficient strategy to construct a triple-conductive region through surface self-assembly protonation based on the robust double-perovskite PrBaCo1.92 Zr0.08 O5+δ , is proposed. In situ exsolution of BaZrO3 -based nanoparticles growing from the host oxide under oxidizing atmosphere by liberating Ba/Zr cations from A/B-sites readily forms proton transfer channels. The surface reconstructing heterostructures improve the structural stability, reduce the thermal expansion, and accelerate the oxygen reduction catalytic activity of such nanocomposite cathodes. This design route significantly boosts electrochemical performance with maximum peak power densities of 1453 and 992 mW cm-2 at 700 and 650 °C, respectively, 86% higher than the parent PrBaCo2 O5+δ cathode, accompanied by a much improved operational durability of 140 h at 600 °C.

Arbitrary active control of the Pancharatnam-Berry phase in a terahertz metasurface.

Active phase-control metasurfaces show outstanding capability in the active manipulation of light propagation, while the previous active phase control methods have many constraints in the cost of simulation or the phase modulation range. In this paper, we design and demonstrate a phase controlled metastructure based on two circular split ring resonators (CSRRs) composed of silicon and Au with different widths, which can continuously achieve an arbitrary Pancharatnam-Berry (PB) phase between -π and π before or after active control. The PB phase of such a metasurface before active control is determined by the rotation angle of the Au-composed CSRR, while the PB phase after active control is determined by the rotation angle of the silicon-composed CSRR. And active control of the PB phase is realized by varying conductivity of silicon under an external optical pump. Based on this metastructure, active control of light deflection, metalens with arbitrary reconfigurable focal points and achromatic metalens under selective frequencies are designed and simulated. Moreover, the experimental results demonstrate that focal spots of metalens can be actively controlled by the optical pump, in accord with the simulated ones. Our metastructure implements a plethora of metasurfaces' active phase modulation and provides applications in active light manipulation.

Zonal model for predicting contaminant distribution in stratum ventilated rooms.

Accurate prediction of the non-uniform contaminant distribution under stratum ventilation (SV) is crucial for optimal design for reducing contaminant exposure risks. Compared with experiments and computational fluid dynamics, zonal models are convenient to implement. This study proposes a zonal model for predicting dynamic non-uniform contaminant distribution in the stratum ventilated room. The zoning method is based on the unique airflow pattern under SV, and the room is divided into the jet zone, entrainment zone, and the mixing zone. The interzonal airflow rate is derived from the profile of the supply air jet. The results show that the proposed zonal model can predict the dynamic contaminant distribution in the stratum ventilated room. Compared with the experimental measurement, the predictions show good accuracy with the mean absolute error (MAE) at 0.51-2.36 ppm and root mean squared error (RMSE) at 0.64-2.53 ppm. The error of the proposed zonal model is influenced by the degree of mixing in each subzone. The proposed zonal model shows better accuracy for non-uniform air distribution under stratum ventilation compared with the existing zonal model.

Zn-doped NiSe2@Ni(OH)2 nanocomposites as binder-free electrodes for asymmetric supercapacitors with impressive performance.

The low stability and poor activities of transition metal selenides (TMSs) in alkaline electrolyte limit their application in supercapacitors. Metal doping and hybridization of various electroactive materials with different properties are utilized to enhance the electrochemical performance of TMSs by optimizing their electronic structure and providing rich electrochemical active sites. Herein, we report a simple two-step hydrothermal method for the growth of Zn-doped NiSe2 and Ni(OH)2 nanocomposites on Ni foam [Zn-NiSe2/Ni(OH)2]. The resulting material delivers high specific capacity (1525.8 C g-1/564.7 mA h g-1 at 6 A g-1 and 1220 C g-1 at 10 A g-1) in a three-electrode system. A Zn-NiSe2/Ni(OH)2//porous carbon (PC) aqueous asymmetric supercapacitor (ASC) was built by utilizing Zn-NiSe2/Ni(OH)2 as the positive electrode and PC as the negative electrode. This Zn-NiSe2/Ni(OH)2//PC ASC shows an energy density of 75.8 W h kg-1 at a power density of 916.1 W kg-1 and achieves a specific capacity retention of 100% after 25 000 cycles at 10 A g-1. These results reveal that the Zn doping and the hybridization of NiSe2 with Ni(OH)2 can obtain impressive electrochemical properties in ASCs.

Possible Topological Hall Effect above Room Temperature in Layered Cr1.2Te2 Ferromagnet.

Topological Hall effect (THE) has been used as a powerful tool to unlock spin chirality in novel magnetic materials. Recent focus has been widely paid to THE and possible chiral spin textures in two-dimensional (2D) layered magnetic materials. However, the room-temperature THE has been barely reported in 2D materials, which hinders its practical applications in 2D spintronics. In this paper, we report a possible THE signal featuring antisymmetric peaks in a wide temperature window up to 320 K in Cr1.2Te2, a new quasi-2D ferromagnetic material. The temperature, thickness, and magnetic field dependences of the THE lead to potential spin chirality origin that is associated with the spin canting under external magnetic fields. Our work holds promise for practical applications in future chiral spin-based vdW spintronic devices.

Ventilation indices for evaluation of airborne infection risk control performance of air distribution.

Air distribution is an effective engineering measure to fight against respiratory infectious diseases like COVID-19. Ventilation indices are widely used to indicate the airborne infection risk of respiratory infectious diseases due to the practical convenience. This study investigates the relationships between the ventilation indices and airborne infection risk to suggest the proper ventilation indices for the evaluation of airborne infection risk control performance of air distribution. Besides the commonly used ventilation indices of the age of air (AoA), air change effectiveness (ACE), and contaminant removal effectiveness (CRE), this study introduces two ventilation indices, i.e., the air utilization effectiveness (AUE) and contaminant dispersion index (CDI). CFD simulations of a hospital ward and a classroom served by different air distributions, including mixing ventilation, displacement ventilation, stratum ventilation and downward ventilation, are validated to calculate the ventilation indices and airborne infection risk. A three-step correlation analysis based on Spearman's rank correlation coefficient, Pearson correlation coefficient, and goodness of fit and a min-max normalization-based error analysis are developed to qualitatively and quantitatively test the validity of ventilation indices respectively. The results recommend the integrated index of AUE and CDI to indicate the overall airborne infection risk, and CDI to indicate the local airborne infection risk respectively regardless of the effects of air distribution, supply airflow rate, infectivity intensity, room configuration and occupant distribution. This study contributes to airborne transmission control of infectious respiratory diseases with air distribution.

Properties of diamane anchored with different groups.

The two-dimensional counterpart of diamond, diamane, has attracted increasing interest due to its potentially distinctive properties. In this paper, diamanes anchored with different anion groups have been systematically studied with density functional theory (DFT) for the first time. Among them 12 conformers are confirmed to be stable and present direct semiconductor features with bandgaps ranging from 2.527 eV to 4.153 eV, and the in-plane stiffness is larger than that of graphene. Moreover, the electron carrier mobility of chair2-F is exceptionally high at 16546.713 cm2 V-1 s-1 along the y-direction, which is remarkably larger than that of diamond; and N-, B-doped boat2-H can be doped to have n-, p-type conductivity with a moderate activation energy of 0.34 and 0.37 eV, respectively. This work suggests that functionalized diamanes are promising for electronic devices and engineering materials.

Strain-induced high-temperature perovskite ferromagnetic insulator.

Ferromagnetic insulators are required for many new magnetic devices, such as dissipationless quantum-spintronic devices, magnetic tunneling junctions, etc. Ferromagnetic insulators with a high Curie temperature and a high-symmetry structure are critical integration with common single-crystalline oxide films or substrates. So far, the commonly used ferromagnetic insulators mostly possess low-symmetry structures associated with a poor growth quality and widespread properties. The few known high-symmetry materials either have extremely low Curie temperatures (≤16 K), or require chemical doping of an otherwise antiferromagnetic matrix. Here we present compelling evidence that the LaCoO3 single-crystalline thin film under tensile strain is a rare undoped perovskite ferromagnetic insulator with a remarkably high TC of up to 90 K. Both experiments and first-principles calculations demonstrate tensile-strain-induced ferromagnetism which does not exist in bulk LaCoO3 The ferromagnetism is strongest within a nearly stoichiometric structure, disappearing when the Co2+ defect concentration reaches about 10%. Significant impact of the research includes demonstration of a strain-induced high-temperature ferromagnetic insulator, successful elevation of the transition over the liquid-nitrogen temperature, and high potential for integration into large-area device fabrication processes.

Revealing Isolated M-N3 C1 Active Sites for Efficient Collaborative Oxygen Reduction Catalysis.

Single atom catalysts (SACs) are of great importance for oxygen reduction, a critical process in renewable energy technologies. The catalytic performance of SACs largely depends on the structure of their active sites, but explorations of highly active structures for SAC active sites are still limited. Herein, we demonstrate a combined experimental and theoretical study of oxygen reduction catalysis on SACs, which incorporate M-N3 C1 site structure, composed of atomically dispersed transition metals (e.g., Fe, Co, and Cu) in nitrogenated carbon nanosheets. The resulting SACs with M-N3 C1 sites exhibited prominent oxygen reduction catalytic activities in both acidic and alkaline media, following the trend Fe-N3 C1 > Co-N3 C1 > Cu-N3 C1 . Theoretical calculations suggest the C atoms in these structures behave as collaborative adsorption sites to M atoms, thanks to interactions between the d/p orbitals of the M/C atoms in the M-N3 C1 sites, enabling dual site oxygen reduction.

Optimized Electronic Configuration to Improve the Surface Absorption and Bulk Conductivity for Enhanced Oxygen Evolution Reaction.

The composition and structure are crucial for stabilizing an appropriate electronic configuration (unit eg electron for example) in high-efficiency electrocatalysts for the oxygen evolution reaction (OER). Here, an excellent platform to investigate the roles of the composition and structure in tuning the electron configuration for higher OER efficiency is provided by layered perovskite oxides with subtle variations of composition and structure (doping with 0%, 50%, and 100% cobalt in the Bi7Fe3Ti3O21). The crystal structures were analyzed by X-ray diffraction refinement, and the electronic structures were calculated based on X-ray absorption spectroscopy and magnetization vs temperature plots according to the Curie-Weiss law. The results indicate that the elongation of oxygen octahedra along the c-axis in layered perovskite could stabilize Co ions in the intermediate spin (IS) ( t2g)5( eg)1 state, resulting in dramatically enhanced electronic conductivity and absorption capacity. Subsequently, the OER efficiency of sample with 100% Co was found to be (incredibly) 100 times higher than that of the sample with 0% Co, with the current density increased from 0.13 to 43 mA/cm2 (1.8 V vs reversible hydrogen electrode); the Tafel slope was reduced from 656 to 87 mV/dec; and double-layer capacity enhanced from 174 to 4193 µF/cm2. This work reveals that both the composition and structure should be taken into account to stabilize a suitable electronic structure such as IS Co ions with moderate absorption and benign electronic conductivity for high-efficiency catalysis of the OER.

All-dielectric metamaterial analogue of electromagnetically induced transparency and its sensing application in terahertz range.

A novel electromagnetically induced transparency (EIT) all-dielectric metamaterial is proposed, fabricated, and characterized. The unit cell of the proposed metamaterial comprises of two asymmetric split ring resonators (a-SRRs) positioned with a mirror symmetry. The asymmetric nature of a-SRRs results from the length difference of two arcs. Optical properties of the fabricated metamaterial are investigated numerically using finite difference method, as well as experimentally using a terahertz time-domain spectroscopy. The results confirm that the proposed metamaterial exhibits an EIT transparent window in the frequency range around 0.78THz with a Q-factor of ~75.7 and a time-delay up to ~28.9ps. Theoretical investigations show that EIT effects in our metamaterial are achieved by hybridizing two bright modes in the same unit cell, which are aroused by the excitation of magnetic moments. We also confirm that the proposed metamaterial has great potential for sensing applications with high sensitivity and high figure of merit (FOM), which guarantees potential applications in in situ chemical and biological sensing.

Dual band and tunable perfect absorber based on dual gratings-coupled graphene-dielectric multilayer structures.

In this paper, a mid-infrared perfect absorber based on the dual gratings-coupled graphene-dielectric multilayer structures (DGC-GDM) is proposed, in which GDM is sandwiched between two Au gratings. The DGC-GDM absorber shows advantages of dual-band and tunable absorption, insensitive to polarization, ultrathin thickness and wide angle range absorption. Two kinds of SPPs in the GDM layer can be excited by the upper and lower Au gratings, respectively, which confine the incident light into the GDM and thus contribute to the dual-band absorption. The wavelength of the absorption peak can be effectively changed by varying the Fermi level of graphene. Most importantly, an analytic formulas describing the relationships between the parameters of the absorber and the absorption spectra is derived. And the accuracy of the theoretical formulas is verified by comparing the simulation results with the theoretically calculated ones. Therefore, the exact values of parameters of the structure for an absorption peak as required can be obtained. The proposed structure can be applied to absorbers that are working at other frequencies.