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Continuous topological charge manipulation with radially varying polarizations
Topological charge (m), a fundamental quantity characterizing optical orbital angular momentum (OAM), has been intensively studied primarily as a discrete integer. However, realizing topological charges with arbitrary, continuous values remains a significant challenge in structured light fields. In this work, we demonstrate that continuous tuning of the effective topological charge (meff) can be achieved by designing a radially varying state of polarization (SOP) in a perfect vector vortex beam. Our approach utilizes the synergistic coupling between the beam's azimuthal phase and the engineered radial polarization gradient. Both theoretical calculations and experimental results show that the magnitude and sign of meff are precisely determined by two key parameters: a phase-dependent parameter controlling the local SOP and the beam's waist radius. The high precision of this control is validated through optical tweezer experiments, where the angular velocities of trapped particles are shown to scale linearly with the continuously adjustable meff. This work not only breaks the conventional discreteness barriers of OAM but also offers a highly versatile platform for advanced applications in light field manipulation and dynamical microparticle control.
Molecularly Tailored Dual‐Function Deep Eutectic Solvent Enhances Spent Lithium‐Ion Battery Cathode Delamination and Regeneration
ABSTRACT Deep eutectic solvents (DES) are efficient for separating cathode materials and current collectors from spent lithium‐ion batteries due to their high solubility and tunable properties. However, they suffer from slow reaction kinetics (>30 min) and high‐temperature requirement (>120°C). Herein, a dual‐function DES composed of diethyl (hydroxymethyl) phosphonate (DHP) and malonic acid (MA) with low temperature and faster kinetics was designed. The nucleophilic groups (─OH and alkoxy) on DHP and MA created extensive negative electrostatic potential regions, facilitating the degradation of polyvinylidene fluoride (PVDF) binder at low temperatures. Concurrently, the formed hydrogen‐bonding network weakened intermolecular interactions, reducing viscosity and enhancing mass transfer. For LiCoO 2 , a separation efficiency of >99% was achieved within 15 min at 60°C. Separation mechanism confirmed that PVDF degradation was triggered by the reaction of DHP–MA molecules with H‐atoms, forming solvent channels. Furthermore, with the penetration of H + and MA towards channels, the activation of the corrosion‐passivation reaction brought about the accelerated cathode material detachment. The separated material exhibited low impurity content (<0.026 wt%), minimal metal loss (<2 wt%), and a well‐preserved crystal structure, conducing to the repair of high‐performance materials. Similar results were achieved for LiFePO 4 and LiNi 0.3 Co 0.3 Mn 0.3 O 2 , offering a universal strategy for high‐quality cathode materials recycling.
Polyhydroxy organic molecule-cross-linked polyvinylidene fluoride with enhanced breakdown strength and energy density
Polyvinylidene fluoride (PVDF) has been extensively studied for dielectric energy storage applications owing to its excellent dielectric properties. There remains a persistent demand to enhance its breakdown strength and achieve higher energy storage density. In this work, a hydrogen-bonding cross-linking strategy is demonstrated to effectively enhance the breakdown strength and energy storage performance of PVDF. Tris(hydroxymethyl)nitromethane (THNM), containing multiple hydroxyl groups, was employed as a cross-linking agent to form multiple hydrogen bonds with the C–F groups in PVDF chains via a facile solution-casting process. The establishment of a hydrogen-bonding cross-linked network significantly enhances the mechanical strength and introduces charge traps into the PVDF matrix, thereby increasing the breakdown strength from 572 MV/m for the pristine PVDF film to 744 MV/m for the THNM-cross-linked-PVDF film (T-c-PVDF). Consequently, the T-c-PVDF film achieves a high energy storage density of 21.83 J/cm3, representing a 150% improvement over the pure PVDF film, while maintaining a charge–discharge efficiency exceeding 70%, and the energy storage performance stands out among PVDF-based dielectric materials from state-of-the-art works. This work highlights the significant potential of constructing a hydrogen-bonding cross-linked network within dielectric polymers in enhancing their breakdown strength and energy storage performance.
Dihydrogen Bond Cooperativity Resolves Zero‐Linear Compressibility in an Energetic Crystal
ABSTRACT Zero linear compressibility (ZLC) energetic materials can be used as anti‐shock materials to maintain stability in at high‐pressure environments up to tens of gigapascals under shock conditions. Achieving an energetic material with ZLC properties and clarifying its structure–activity relationship should meet the urgent safety demands. In this study, the first ZLC organic molecular crystal, trimethylamine borane (TMAB), which can be utilized as a propellant component, was discovered. TMAB underwent an isostructural phase transition at 9.2 GPa, as evidenced by the combination of Raman, infrared, and UV–vis absorption spectra and in situ synchrotron x‐ray diffraction patterns. Note that the c axis exhibited intriguing ZLC in the pressure range from 9.2 to 14.0 GPa, indicating the superior stability of TMAB under extreme high pressure. The dihydrogen‐bonding cooperativity effect under high pressure was responsible for the observed ZLC in TMAB, unlike that observed for previously reported ZLC materials. This study developed a ZLC energetic organic molecular crystal and revealed its underlying mechanism, which facilitates the design of anti‐shock propellants.
UV ozone oxidized high- <i>k</i> TaO <i>x</i> dielectric with van der Waals interface for two-dimensional electronic devices
Two-dimensional (2D) semiconductors are promising channel materials for next-generation field-effect transistors (FETs) due to their superior gate control capabilities, dangling-bond-free surfaces, and high mobility. However, it remains challenging to integrate ultrathin and uniform high-k dielectrics on 2D semiconductors to fabricate FETs with large gate capacitance and clean interfaces. Here, we report a high-k dielectric TaOx prepared via UV ozone oxidation of layered tantalum disulfide (TaS2), with a high effective dielectric constant (εr) of ∼28 and a breakdown field of ∼8 MV/cm. We integrated the TaOx dielectric with 2D semiconductors through van der Waals assembly, exhibiting small hysteresis (&lt;10 mV), a high current on/off ratio approaching 107, a steep subthreshold swing of 64 mV/dec, and a low interface trap density Dit of ∼6.8 × 1011 cm−2 eV−1. By integrating n-type MoS2 and p-type WSe2 transistors with van der Waals dielectric TaOx, we have realized logic circuits with low static power consumption capable of performing NOT, NAND, and NOR operations. Notably, the logic inverter (NOT gate) exhibits a static voltage gain as high as 260. Our dielectric fabrication strategy can be used to integrate 2D materials and amorphous oxide dielectrics, thus offering a promising approach for the development of high-performance low-power electronics.
On-demand microwave single-photon source based on tantalum thin films
Single-photon sources are crucial for quantum information technologies. Here, we demonstrate a microwave single-photon source based on tantalum thin films, whose favorable material properties enable high-quality, stable photon emission. The antibunching behavior of the emitted radiation is revealed by second-order correlation measurements. Furthermore, traveling-wave parametric amplifiers are used as low-noise pre-amplifiers in the detection chains, substantially improving the signal-to-noise ratio and thereby greatly reducing the acquisition time required for second-order correlation measurements. These results demonstrate the viability of tantalum-based superconducting devices as reliable platforms for microwave quantum photonics.
Steering the Shape‐shifting of Bullvalene‐Pd <sup>II</sup> Complexes Through Steric and Geometric Strain
Abstract Di‐substituted bullvalenes are fluxional molecules possessing up to fifteen possible isomers. Their shape‐shifting nature has been harnessed in host‐guest chemistry, drug design, polymers, and electromechanical systems. Despite this, principles for controlling the fluxional pathways of bullvalene, including access to isomers that are not normally populated, remain poorly understood. In this study, we elucidate the restricted shapeshifting of bis‐pyridyl bullvalene ligands in ethylenediamine (en) cis ‐capped Pd II complexes. The energetic landscape of 3‐substituted bis‐pyridyl bullvalene remains open to A and B isomers in [Pd 2 (en)L 2 ] complexes, whilst the coordination of 4‐ and 2‐substituted bis‐pyridyl derivatives significantly restrict bullvalene's isomerization pathway. In one case, chelation of bis‐2‐pyridyl bullvalene enables access to an otherwise energetically inaccessible D‐isomer. Exclusive formation of this isomer is achieved by increasing the sterics of the cis ‐capping ligand.
Observation of anomalous exciton-polariton bands in (PEA)2PbI4 perovskite based microcavity at room temperature
Recently, anomalous energy bands with negative mass attract intensive attention where non-Hermiticity plays an important role. In this work, we observe anomalous exciton-polariton bands in (PEA)2PbI4 perovskite based microcavity at room temperature. We simulate the anomalous band structure using a non-Hermitian coupled oscillator model, which agrees with experiments very well. Our results offer to study non-Hermitian polariton wave dynamics at room temperature.
Dual‐Functionalized Bonding Management via Aromatic Formamidine Ligands Enables 25.57%‐Efficient Ambient‐Printed Perovskite Solar Cells
ABSTRACT Ambient printing of perovskite solar cells (PSCs) faces severe challenges in controlling crystallization under humid conditions, leading to substantial performance losses compared to inertly processed devices. While ligand‐assisted coordination is known to modulate crystal growth, a precise understanding of how specific chemical bonds influence crystallization dynamics during ambient printing remains elusive. Herein, we unveil a dual‐functionalized bonding (DFB) mechanism enabled by aromatic formamidine ligands that concurrently coordinate with both the inorganic framework and organic cations during ambient printing. The key mechanistic insight lies in the ability of ligands to form simultaneous coordination bonds with [PbI 6 ] 4— octahedra and hydrogen bonds with formamidinium ions (FA + ), which collectively delay nucleation, suppress the δ‐phase formation, and widen the recrystallization window. By incorporating an electron‐deficient triazole ring into the ligand backbone, we enhance this bifunctional binding effect, leading to superior crystallization control and defect suppression. The resulting perovskite films exhibit remarkable homogeneity, low trap density, and enhanced carrier diffusion. Consequently, ambient‐printed devices achieve champion power conversion efficiencies of 25.57% for 0.09 cm 2 , 23.98% for 1.04 cm 2 , and 22.98% in 5 × 5 cm 2 mini‐modules. The optimized devices retain over 90% of their initial performance after 1,000 h of continuous operation. This work provides a profound mechanistic framework for molecular‐level crystallization control in printed photovoltaics.
Nanoscale crystallization of Cr2Ge2Te6 thin films induced by terahertz near-fields
Cr2Ge2Te6 (CrGT) is a promising phase-change material exhibiting low operating energy and a thermally stable amorphous phase, suitable for next-generation nonvolatile memory. To assess its nanoscale switching behavior, we investigated phase transitions in amorphous CrGT thin films using a scanning tunneling microscope excited by picosecond terahertz (THz) pulses. Local THz near-fields enhanced within the tunnel junction induced reproducible nanoscale crystallization without mechanical contact. By varying the field strength, we identified a threshold far-electric field of approximately 0.6 kV cm−1 for the onset of crystallization. The results indicate that Joule heating generated by the tip-enhanced THz near-field governs the amorphous-to-crystalline transition. These findings establish THz field-driven nanoscale phase switching in CrGT and provide a physical framework for ultrafast, nonvolatile phase-control architectures.
Spin‐Regulated Fe‐Cu Diatomic Catalytic Chemistry Enables Significant Minimization of Catalyst Consumption With High‐Efficiency Fenton‐Like Activity
ABSTRACT The high cost and limited metal loading of single‐atom catalysts hinder their broader applications in Fenton‐like reaction for water treatment. Herein, we developed an Fe‐Cu diatomic catalyst supported on N‐doped carbon (Fe‐Cu‐CN) that enabled catalyst minimization while maintaining high peroxymonosulfate (PMS) activation efficiency. By tailoring asymmetric Fe‐Cu coordination and inducing a spin‐state transition of Fe from low‐spin to high‐spin, the catalyst enhanced Fe 3d ‐O 2p electron coupling and substantially improved intrinsic activity. The Fe‐Cu‐CN/PMS system enabled a highly efficient electron transfer pathway for pollutant degradation, achieving rapid bisphenol A removal (100% within 5 min; k obs = 1.61 min − 1 ) with only 10%–20% of the catalyst dosage commonly reported in the literature. Density functional theory calculations and electrochemical analyses revealed that heteronuclear coordination modified the spin‐state of the active center, narrowing the gap between the d‐band center of Fe 3d orbitals and the Fermi energy level to strengthen the electronic interaction at the reaction interface, resulting in a lower free energy barrier of PMS adsorption thermodynamically. Furthermore, the life‐cycle analysis demonstrated superior environmental performance. This study provides a generalizable strategy to enhance unit catalytic activity through spin‐state engineering, offering practical potential for PMS‐based water treatment.
Electron drift velocity measurement of AlGaN/GaN single- and multi-channel Fin structures
This paper presents a method for extracting electron drift velocity vs electric field characteristics in AlGaN/GaN Fin structures by combining Fin-Hall bar and Fin-Transmission Line Model measurements. Carrier density and Ohmic contact resistivity were independently extracted as a function of Fin width, enabling accurate calculation of internal electric field and drift velocity from pulsed I–V curves. It is revealed that the drift velocity decreases with the narrowing of Fin width due to enhanced sidewall influence, and multi-channel structures show higher drift velocity thanks to weaker interaction between electrons and longitudinal optical phonons. This measurement method provides a quantitative approach for studying carrier transport behavior under high electric field, offering a fundamental tool for Fin-based device design and modeling.
Chain length effect of large organic cations on the amplified spontaneous emission and lasing properties of quasi-2D Dion–Jacobson perovskites
Quasi-two-dimensional (quasi-2D) Dion–Jacobson (DJ) perovskites modified with large organic cations exhibit superior optoelectronic properties and stability compared to their three-dimensional (3D) counterparts, making them promising for light-emitting diodes and lasing applications. While diammonium cations with linear chain structures are preferred due to their hydrogen-bonding capability and enhanced structural stability, the effect of cation chain length remains insufficiently understood. Here, we systematically investigate three diammonium spacers with varying chain lengths. Ultrafast spectroscopy reveals that longer-chain cations promote pronounced phase separation, which facilitates the formation of a high-quality n=2 phase, uniform phase distribution, efficient energy transfer, and suppressed non-radiative recombination. These effects collectively reduce the amplified spontaneous emission threshold, from 41.94 μJ/cm2 (EDA, short-chain) and 29.86 μJ/cm2 (BDA, medium-chain) to an ultralow 7.67 μJ/cm2 (PentDA, long-chain). Using this optimized gain medium, we demonstrate a single-mode vertical-cavity laser with a threshold of 6.75 μJ/cm2, a narrow linewidth of 0.49 nm, and a high-quality factor of 1093.8. Conversely, short-chain cations lead to weak phase separation and an insufficient n=2 phase content, resulting in film transient absorption characteristics dominated by excited-state absorption. This study clarifies the critical role of cation chain length in tuning the phase behavior and optical gain of quasi-2D DJ perovskites, providing guidance for their use in low-threshold laser devices.
Flow Pyrolysis Synthesis of Single‐Atom Catalysts With Tunable Crumple and Electronic Structures for 2‐Electron Oxygen Reduction
ABSTRACT Single‐atom catalysts (SACs) are attractive due to their high metal utilization efficiency and intriguing properties. Developing a facile and general method to synthesize SACs with tunable geometric and electronic structure is critical for realizing their widespread application. Here we report a continuous‐flow spray pyrolysis approach to SACs (including iron, cobalt, nickel, copper, and platinum) with control over the crumple structure of the graphene substrate and the electronic structure of the single‐atom sites. Notably, the formation of single‐atom sites and morphologic engineering of the substrate are simultaneously achieved within the single‐step droplet‐to‐particle conversion process. Taking Co SACs for catalyzing the 2‐electron oxygen reduction reaction (ORR) as a representative example, the Co moieties possess a deformed local geometric structure and electron deficiency that are dependent on the crumpling degree of the graphene substrate, leading to controllable ORR activity and selectivity. The optimal catalyst achieves an unprecedently high mass activity of 456 ± 4 A g −1 at 0.65 V, along with a high H 2 O 2 selectivity of up to 97%. Furthermore, a flow‐cell electrolyzer assembled with this catalyst demonstrates an averaged H 2 O 2 productivity of 23.78 mol g −1 catalyst h −1 , sustained over 120 h of operation.
Atomic layer etching-enabled interface engineering for reduced subthreshold swing and improved uniformity in p-channel GaN MOSFETs
In this work, enhancement-mode p-MOSFETs on p-GaN/AlGaN/GaN-on-Si substrates were fabricated using a gate recess process that combines reactive ion etching (RIE) with atomic layer etching (ALE), where ALE is employed as an interface engineering approach following conventional plasma etching to mitigate recess-induced interface damage. Compared with RIE-only devices, the RIE + ALE devices yield smoother surfaces and significantly suppress interface trap density. These interface improvements lead to enhanced subthreshold characteristics and markedly tighter device-to-device uniformity. In particular, the subthreshold swing decreased from 365 ± 179 to 149 ± 17 mV/dec, while the off-state leakage current was suppressed from 1.9 ± 3.6 × 10−7 to 8.5 ± 5.5 × 10−9 mA/mm. These results demonstrate that ALE provides an effective interface engineering approach for suppressing interface damage and enabling uniform enhancement-mode p-MOSFETs, highlighting its potential for reliable GaN complementary metal–oxide–semiconductor logic and power integrated circuits.
Carbon-doped quasi-bulk hexagonal boron nitride grown by HVPE
We report characterization of 4-in. diameter carbon-doped hexagonal boron nitride (h-BN:C) quasi-bulk crystals (100 μm in thickness) produced by hydride vapor-phase epitaxy. X-ray diffraction characterization results revealed that carbon incorporation enhances crystalline quality due to carbon's role in mitigating native defect formation by substituting on both the B and N sites. Photoluminescence spectroscopy demonstrated that carbon doping fundamentally alters the optical properties. While the undoped wafer exhibits a broad emission line near 3.41 eV, the carbon-doped sample displays three distinct ultraviolet lines at 4.10, 3.91, and 3.74 eV. These peaks correspond to the zero-phonon line of a carbon defect quantum emitter and its associated phonon replicas, characterized by a room-temperature radiative lifetime of approximately 0.5 ns. Although carbon is unsuitable for conventional n- or p-type doping in h-BN, carbon doping appears to be a useful tool for improving crystalline quality and enabling the control of unique properties essential for high-efficiency neutron detectors, optoelectronics, and quantum technologies.
A green and general room-temperature synthesis of doped 0D perovskites for tunable and enhanced luminescence
Zero-dimensional (0D) double perovskite Cs2ZrCl6 has emerged as a promising lead-free phosphor due to its strong quantum confinement, excellent stability, and tunable luminescence. However, the conventional synthesis routes often rely on harsh conditions—such as high temperature, corrosive reagents, or complex vapor-phase method—that hinder the scalability and environmental sustainability. Herein, we report a green, room-temperature, and scalable strategy to synthesize the Cs2ZrCl6 microcrystalline powders, which involves the sequential addition of ZrCl4 and CsCl to ethanol under ambient stirring conditions. By simply introducing dopant precursors (e.g., TeO2, SbCl3, and BiCl3) or substituting CsCl with CsBr during synthesis, we achieve the versatile doped Cs2ZrCl6 with various cations (Te4+, Sb3+, and Bi3+) and anions (Br−) to realize the tunable broad spectral from blue to orange emission. Notably, this approach overcomes the long-standing challenge of halide (Br−) incorporation into Cs2ZrCl6, which is difficult via hydrothermal methods and costly via vapor deposition. Furthermore, in situ formation of a hydrophobic SiO2 layer through tetramethoxysilane hydrolysis enhances the moisture resistance, as evidenced by an increased water contact angle. This facile, low-cost, and eco-friendly methodology paves the way for the practical deployment of Cs2ZrCl6-based phosphors in lighting, displays, and radiation detection technologies.
Demonstration of high-fidelity gates in a strongly anharmonic with long-coherence C-shunt flux qubit
We demonstrate high-fidelity single-qubit gates on a C-shunt flux qubit that simultaneously combines a large anharmonicity (A/2π=848 MHz) with long relaxation time (T1=23 μs). The large anharmonicity significantly suppresses leakage to higher energy levels, enabling fast and precise microwave control. Using derivative removal by adiabatic gate pulses and randomized benchmarking, the qubit achieves gate fidelities exceeding 99.9%, highlighting the capability of C-shunt flux qubits for robust and high-performance quantum operations. These results establish them as a promising platform for scalable quantum information processing.
Simulation study of low-field proton magnetic resonance spectroscopy using optically pumped magnetometers
We numerically investigated the feasibility of low-field magnetic resonance spectroscopy (MRS) using optically pumped magnetometers (OPMs). Low magnetic fields reduce signal strength and spectral resolution, challenging reliable metabolite quantification. To address these issues, we performed Bloch-equation–based simulations at 0.01–7 T using aqueous phantoms. We compared chemical shift selective and inversion recovery (IR) methods for water suppression. We also evaluated signal detection using both radio frequency coils and OPMs. The IR method, relying on T1 contrast rather than frequency selectivity, effectively suppressed water signals down to 0.1 T. The signal-to-noise ratio (SNR) of Glu increased below 0.7 T. OPMs maintained nearly constant SNR across 0.01–1 T and outperformed coils below 1 T. In mixed-metabolite settings, however, spectral overlap and IR-induced co-suppression impaired detection—particularly for Gln below 0.1 T. These results show that IR and OPMs offer complementary advantages for low-field MRS, while spectral resolution remains a challenge. This work provides a theoretical basis for enhancing low-field MRS techniques and expanding access to metabolic diagnostics in clinical and research settings.
On-chip FSR manipulation of optical frequency combs with a four-wave mixing time lens
Precise control of the free spectral range (FSR) in high-repetition-rate (e.g., 100 GHz) optical frequency combs is critical for advanced applications but remains technically challenging. The frequency domain Talbot effect has emerged as a predominant mechanism for such spectral reconfiguration. Conventional Talbot-based methods face distinct limitations: electro-optic modulation is constrained by bandwidth, while cross-phase modulation demands complex pulse shaping. Furthermore, traditional four-wave mixing (FWM) schemes suffer from bulky footprints and instability due to their reliance on long fibers. Here, we demonstrate on-chip spectral densification by integrating a silicon nitride chirped waveguide Bragg grating (CWBG) with an FWM time lens. Replacing the kilometer-scale fibers used in standard setups, our CWBG generates the requisite large group delay within a centimeter-scale footprint. This compact chip-based dispersion module significantly reduces the long-fiber footprint and mitigates environmental instability and higher-order dispersion distortions. We experimentally compressed the FSR of a 100-GHz comb by integer factors (N = 2, 3, 4), thereby validating a robust, scalable platform for miniature spectral reconstruction in microwave photonics.