Accepted
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Abstract +
Ultrafast magnetization dynamics represents a forefront area in modern spintronics and magnetic materials research, addressing the response and evolution of magnetic moments in magnetic systems over femtosecond to nanosecond timescales. To elucidate such ultrafast magnetic processes, a variety of time-resolved experimental techniques have been developed. Among them, synchrotron-based X-ray ferromagnetic resonance (XFMR) combines microwave-driven ferromagnetic resonance (FMR) with X-ray magnetic circular dichroism (XMCD) detection, enabling element-, valence-, and lattice space- resolved measurements of magnetization precession on the picosecond timescale and providing direct access to both the amplitude and phase of the dynamic magnetic moment. This work developed a picosecond time-resolved XFMR platform at the BL07U vector magnet beamline of the Shanghai Synchrotron Radiation Facility (SSRF). The system employs a lock-in modulation detection scheme precisely synchronized with the storage-ring master clock, realizing stable excitation and detection of spin precession in magnetic materials up to 6 GHz, with the background noise effectively suppressed to 30 fA, and an overall phase time resolution better than 10 ps. The successful implementation of this technique establishes a state-of-the-art XFMR capability in China, achieving internationally competitive performance in both temporal resolution and detection sensitivity. This development provides a powerful experimental foundation for future investigations of spin current and orbital current detection, as well as ferrimagnetic and antiferromagnetic dynamics.
Abstract +
Optical clocks, as the next-generation time and frequency standards, achieve ultra-low systematic uncertainty and frequency instability by precisely referencing the local oscillator frequency to the optical atomic transition frequency. Since the successful development of the first all-optical 199Hg+ optical clock in the early 21st century, optical atomic clocks have made remarkable progress over the past two decades. Currently, state-of-the-art optical clocks have achieved systematic uncertainties and frequency stabilities at the 10-19 level, surpassing traditional microwave atomic clocks by more than two orders of magnitude. This breakthrough has opened up new research dimensions in fundamental physics and precision measurement.
This paper begins by reviewing landmark developments in ion optical clocks and optical lattice clocks. Corresponding tables are provided to summarize the best performance metrics achieved by all known research groups, along with the specific optical clock types developed by each.
The main focus of the paper is a review of precision measurement applications based on optical clocks, covering four key areas.
First, the method and typical setup for steering International Atomic Time (TAI) using optical clocks are introduced. The principles underlying optical frequency measurement data submission are summarized, followed by an overview of progress in TAI steering with optical clocks.
Second, the principles for constraining variations in fundamental physical constants through optical clock comparisons are briefly outlined. Recent results on the fine-structure constant and the proton-to-electron mass ratio are presented to illustrate the capability of optical clocks in probing such variations.
Third, tests of Einstein’s equivalence principle are discussed, including principles and recent advances in examining local position invariance and local Lorentz invariance with optical clocks. Local position invariance is tested by measuring gravitational frequency shifts between clocks at different geopotential heights or within distinct regions of a vertical optical lattice. Local Lorentz invariance is probed by comparing optical clocks with different quantization axes; recent advances have pushed the upper limit on Lorentz-violation coefficients for electron-photon systems to the order of 10-21.
Finally, chronometric leveling based on optical clock comparisons is presented. A comparison with traditional geodetic methods is provided, highlighting the advantages of the chronometric approach. The paper also details recent experimental progress in chronometric leveling.
In the outlook section, the paper analyzes potential research directions for further enhancing the performance of optical clocks. It also explores the possible advancements in precision measurement applications, such as constraining the variation rates of fundamental physical constants, as the performance of optical clocks continues to improve.
This paper begins by reviewing landmark developments in ion optical clocks and optical lattice clocks. Corresponding tables are provided to summarize the best performance metrics achieved by all known research groups, along with the specific optical clock types developed by each.
The main focus of the paper is a review of precision measurement applications based on optical clocks, covering four key areas.
First, the method and typical setup for steering International Atomic Time (TAI) using optical clocks are introduced. The principles underlying optical frequency measurement data submission are summarized, followed by an overview of progress in TAI steering with optical clocks.
Second, the principles for constraining variations in fundamental physical constants through optical clock comparisons are briefly outlined. Recent results on the fine-structure constant and the proton-to-electron mass ratio are presented to illustrate the capability of optical clocks in probing such variations.
Third, tests of Einstein’s equivalence principle are discussed, including principles and recent advances in examining local position invariance and local Lorentz invariance with optical clocks. Local position invariance is tested by measuring gravitational frequency shifts between clocks at different geopotential heights or within distinct regions of a vertical optical lattice. Local Lorentz invariance is probed by comparing optical clocks with different quantization axes; recent advances have pushed the upper limit on Lorentz-violation coefficients for electron-photon systems to the order of 10-21.
Finally, chronometric leveling based on optical clock comparisons is presented. A comparison with traditional geodetic methods is provided, highlighting the advantages of the chronometric approach. The paper also details recent experimental progress in chronometric leveling.
In the outlook section, the paper analyzes potential research directions for further enhancing the performance of optical clocks. It also explores the possible advancements in precision measurement applications, such as constraining the variation rates of fundamental physical constants, as the performance of optical clocks continues to improve.
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Abstract +
Topological nodal-line semimetals have emerged as a fascinating class of materials due to their protected band crossings and unique electronic properties. Among them, ZrSiS stands out as a typical system with nodal-line and high carrier mobility. While its bulk properties have been extensively studied, the optical and plasmonic behaviors of its monolayer and bilayer ZrSiS remain largely unexplored. Understanding these low-dimensional forms is crucial for harnessing their potential in nanophotonics and optoelectronic devices. This work, based on first-principles calculations, systematically investigates the electronic band structure, optoelectronic conductivity, optical response, and surface plasmon polariton (SPP) characteristics of monolayer and bilayer ZrSiS. The results were compared with those of bulk materials and typical two-dimensional materials argentene to explore their advantages and disadvantages in all aspects and application prospects. Our results show that layered ZrSiS exhibits distinctive conductivity features arising from its topological nodal-line bands, displaying a significant intraband response in the infrared regime and interband response in the visible range. Analysis of the optical properties reveals that both mono/bilayer structures possess high absorption (significantly exceeding that of graphene) and tunable reflection/transmission windows from the infrared to visible spectrum. Furthermore, regarding plasmonic properties, we find that monolayer and bilayer ZrSiS support SPP in the infrared to visible range (monolayer: 0.5-4 eV; bilayer: 0.4-2.5 eV). These SPP are highly localized, with confinement ratios several times larger than those of bulk ZrSiS, while maintaining propagation lengths on the order of micrometers in the infrared regime. In conclusion, monolayer and bilayer ZrSiS combine tunable electronic structure, high optical absorption, and strongly confined surface plasmons, making them promising candidates for advanced nanophotonic and infrared optoelectronic applications. Their layer-dependent properties offer additional degrees of freedom for device design, paving the way for next-generation tunable plasmonic and photonic devices.
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Abstract +
High-quality-factor (Q-factor) mechanical resonators are indispensable components in quantum optomechanical experiments such as optomechanical cooling, quantum sensing, precision metrology and entanglement/squeezing generation. While the Q-factor measurement has been performed for high-frequency resonators with low Q-factor, the Q-factor measurement for a low-frequency resonator with high Q-factor is still challenging. It is difficult to identify the mechanical modes from the other noise source in the environment, such as audio noises of air fans and mechanical modes of clamps. Furthermore, the traditional piezoceramic transducer for driving the mechanical resonator has limited response speed. In this article, we employs the optical radiation pressure to directly drive the mechanical oscillator. The Q-factor is measured by the ring-down technique. With the help of precise controllable electrical current, the radiation pressure can be precisely controlled, thus providing faster response and broader operational bandwidth, especially in the acoustic and sub-acoustic frequency ranges. What’s more, this approach mitigates the low-frequency noise induced by environmental vibrations and experimental apparatus, which are difficult to isolate. In the experiment, we measure the Q-factors of a mechanical resonator array which includes tens of single mechanical resonators of different size and different structure. A single resonator consists of a single-crystal GaAs cantilever integrated with a micromirror. A laser beam, modulated by an acousto-optic modulator (AOM) acting as a fast optical switch, serves as the radiation pressure driving source. Another probe beam is reflected by the high-reflectivity micromirror of the resonator and detected by a quadrant photodetector (QPD) to obtain the ring-down signal from which the Q-factor is obtained. The results are compared with those obtained using traditional piezoceramic drive. The results show that in the low-frequency region (below ~2 kHz), where environmental noise coupling is pronounced, the optical drive method effectively suppresses low-frequency noises. The relative error of Q-factor measurements using optical drive is approximately 5%, lower than that obtained with piezoelectric drive. This optical radiation-pressure drive technique provides a robust and fast-response approach for measuring the Q-factors of massive low-frequency mechanical resonators.
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Abstract +
Self-trapping, a fundamental nonlinear phenomenon in which waves overcome diffusive spreading through system nonlinearities, is essential for understanding soliton formation and wave localization. Momentum lattices, constructed from the discrete momentum states of ultracold atoms to form synthetic dimensions, provide a versatile platform for investigating topological physics and localization phenomena. In this study, we experimentally investigate interaction-induced self-trapping in a one-dimensional momentum lattice by utilizing a Bose–Einstein condensate (BEC) of cesium atoms confined in a crossed optical dipole trap. Atomic interactions are tuned via a Feshbach resonance by adjusting the s-wave scattering length $a$. The system is initially prepared in a zero-momentum state and then quenched, with the subsequent dynamics probed using time-of-flight imaging. The results show that for weak interactions ($a\approx 3a_{0}$), the atoms undergo ballistic expansion. As the scattering length $a$ increases, diffusion is suppressed, leading to macroscopic self-trapping for $a\geq 600a_{0}$, where the atoms remain localized near the zero-momentum state. Numerical simulations based on the Gross–Pitaevskii equation agree well with the experimental results and yield a critical s-wave scattering length of $a\approx 591a_{0}$. Slight deviations observed at long evolution times arise from decoherence due to spatial separation and heating. In Bogoliubov theory, the repulsive interaction in real space manifests as a local attractive potential in momentum space. This energy shift suppresses tunneling between lattice sites, inducing macroscopic self-trapping. Our findings provide valuable insights for research on quantum many-body physics in momentum lattices.
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Abstract +
Ferroelectric thin films and their device applications have drawn wide attentions since 90s of the 20-century. However, due to the critical size effect, ferroelectric thin films cannot maintain the ferroelectric property as their thickness decreases to the nano size or one atomic thick, holding a big challenge for the development of related nano-electronic devices. With a naturally stable layered structure, two-dimensional materials exhibit many advantages such as high-quality and smooth interface without dangling bond, no interlayer interface defects and the ability to maintain complete physical and chemical properties even at limited atomic thickness. Thus, it is gradually realized that two-dimensional material is a good hotbed for the two-dimensional ferroelectricity. CuInP2S6, α-In2Se3, WTe2, and other intrinsic ferroelectric 2D materials have been reported successively while artificially stacked sliding ferroelectrics such as t-BN have also emerged, which expands the types of 2D ferroelectric materials and opens a new road for the further miniaturization and flexibility of ferroelectric electronic devices. In this article, the recent research progress on two-dimensional ferroelectric materials was reviewed, the composition characteristics, structural features and property modulation of two-dimensional ferroelectric materials were discussed, and the application potential and future research hotspots of 2D ferroelectric materials were prospected.
, , Received Date: 2025-10-24
Abstract +
Magnetic exchange interactions and their induced magnetic structures are crucial factors in determining magnetization switching. Dzyaloshinskii-Moriya interaction (DMI) is an asymmetric exchange interaction arising from spin-orbit coupling and structural inversion symmetry breaking, which is one of the key mechanisms to induce non-collinear magnetic order and chiral magnetic structures, including magnetic Skyrmion, vortex and chiral domain wall. These magnetic structures enable novel information proceeding devices with ultralow power consumption. More importantly, non-collinear magnetic order exhibits richer and more novel physical behaviors than traditional collinear magnetic structures. With ongoing exploration and research into magnetic materials, rare-earth transition metal ferrimagnetic materials such as CoGd, CoTb, and GdFeCohave emerged as notable candidates. These materials combine the spin-orbit coupling of rare-earth elements with the magnetic exchange interactions of transition metals, leading to ultrafast magnetization dynamics, tunable magnetic structures, and rich spin transport phenomena. These properties provide an ideal material platform for studying and manipulating DMI, demonstrating significant potential in designing future high-density magnetic storage and spintronic devices. This review systematically elucidates the microscopic physical origin of DMI, outlines the fundamental characteristics of rare-earth transition metal ferrimagnetic materials, and explores the coupling mechanisms between DMI and ferrimagnetic order. We introduce the fundamental properties of RE-TM systems and their applications in spin logic devices and magnetic memory devices. We focus on discussing the physical phenomena related to DMI in RE-TM systems, including the scaling relationship of DMI in RE-TM, DMI-related spin-orbit torque effects, and the principles and applications of skyrmion-based devices, which will provide both theoretical foundations and technical guidance for the future development of advanced spintronic technologies.
, , Received Date: 2025-08-20
Abstract +
, , Received Date: 2025-09-12
Abstract +
, , Received Date: 2025-10-10
Abstract +
With the rise and widespread applications of three-dimensional (3D) heterogeneous integration technology, inductive voltage regulators are becoming increasingly important for mobile terminals and high-computing-power devices, while also offering significant development opportunities for high-frequency soft magnetic films. According to the requirements of on-chip power inductors, we first review the advantages and limitations of three types of magnetic core films: permalloy, Co-based amorphous metal films, and FeCo-based nanogranular composite films, with a focus on the technical requirements and challenges of several μm-thick laminated magnetic core films. Secondly, almost all on-chip inductors are hard-axis excited, which means that the magnetic field of inductors should be parallel to the hard axis of the magnetic core. We thus compare the characteristics of two methods of preparing large-area films, i.e. applying an in-situ magnetic field and oblique sputtering, both of which can effectively induce in-plane uniaxially magnetic anisotropy (IPUMA). Their influences on the static and high-frequency soft magnetic properties are also compared. The influences of film patterning on the domain structures and high-frequency magnetic losses of magnetic cores, as well as corresponding countermeasures, are also briefly analyzed. Furthermore, the temperature stability of magnetic permeability and anisotropy of magnetic core films is discussed from the perspectives of process compatibility and long-term reliability. Although the Curie temperatures and crystallization temperatures of the three types of magnetic core films are relatively high, the upper limits of their actual process temperatures are affected by the thermal effects on the alignment of magnetic atomic pairs, microstructural defects, and grain size. Finally, the current bottlenecks in testing high-frequency and large-signal magnetic losses of magnetic core films are discussed, and potential technical approaches to achieving magnetic core films that meet the future demands of on-chip power inductors for higher saturation current and lower magnetic losses are outlined.
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Abstract +
Multi-Plane Light Conversion (MPLC) coherent beam combining (CBC) presents a promising approach for flexible optical field manipulation, overcoming the limitations of low energy utilization and poor beam quality in traditional CBC methods. However, its potential for generating diverse structured beams and the underlying design principles remain underexplored. In this work, theoretical model of MPLC-based CBC system was constructed to perform numerical investigation on the property and capability of MPLC optical field manipulation. Localized phase coding and vortex phase coding methods were proposed for mode mapping design to enhance the match between input and output modes. By employing multi-dimensional evaluation metrics including conversion efficiency (η), side-lobe suppression ratio (SSR), and phase matching degree (PMD), the performance of different coding strategies was systematically compared. The results manifested that while random coding yielded an average efficiency of 92% for five multi-focus beams, both localized and vortex coding significantly enhanced output quality, achieving a superior average efficiency of 97.1%. Based on the proposed encoding methods, MPLC successfully produced 5 Laguerre-Gaussian (LG) beams, 5 geometric shapes, and 5 letter patterns with remarkably high average efficiencies, reaching 97.4%, 99.2%, and 96.5%, respectively, accompanied by high SSR (>14 dB) and PMD (>96%). Furthermore, a strategy for arbitrary beam shaping by decomposing the target field into a linear combination of orthogonal modes was proposed and confirmed using a 21-mode MPLC. Simultaneously, its flexibility and the consequential requirement for strong amplitude modulation on the laser array were discussed. Finally, the relationship between the number of supported modes and the required number of phase plates was also analyzed, illustrating that maintaining high efficiency for a larger number of modes necessitates a significant increase in the number of phase plates. This study effectively generated a wide range of structured beams with minimal stray light and high energy utilization, demonstrating that MPLC-based CBC is a powerful and versatile technique for high-efficiency, high-quality optical field manipulation. Future work should focus on optimizing the design to reduce the requisite number of planes, paving the way for practical applications in high-power laser processing, optical communications, and quantum optics.
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Abstract +
Mid-infrared quantum light sources hold broad application prospects in fields such as gas sensing and infrared thermal imaging. However, currently used mid-infrared quantum entanglement light sources primarily rely on bulk periodically poled lithium niobate (PPLN) crystals, which suffer from limitations in both brightness and integration. This paper proposes a theoretical scheme based on lithium niobate thin films utilizing a 1556.9 nm pump to generate entangled photon pairs with a central wavelength of 3113.8 nm. Through optimized waveguide structure and periodic polarization design, Type-II phase matching and group velocity matching are achieved. This enables transverse electric (TE)-polarized pump input to downconvert to generate photon pairs with TE and transverse magnetic (TM) polarization. Furthermore, by combining a domain arrangement algorithm for customized design of the PPLN waveguide’s polarization direction, precise phase matching is achieved, yielding a quantum light source with a purity as high as 0.999 and a brightness reaching 6.18 × 106 cps/mW, representing a three-order-of-magnitude enhancement over bulk PPLN crystal sources. This work offers a promising solution for realizing high-brightness, high-purity on-chip quantum light sources in the mid-infrared band.
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Abstract +
Recent studies on orbital angular momentum (OAM) states in the surface plasmon polariton (SPP) field have primarily focused on the generation of single OAM modes and the evolution of OAM states with various topological charges. However, achieving coherent superposition of two OAM states with well-defined phase relations through precise nanostructure design remains challenging. In this work, we propose a plasmonic nanostructure consisting of paired rectangular slits arranged along circular or segmented Archimedes spiral. The Archimedean spiral of various radii in azimuthal angle provides a geometry-dependent helical phase; coupled with a rotated nanoslit pair, it introduces a geometric phase of twice the rotated angle. By combining chiral spiral with nanoslit pair units, the design both generates plasmonic OAM eigenstates with arbitrary topological charges and enables their coherent superposition. The amplitudes of the two constituent OAM states are continuously tunable through the degree of polarization of the incident light, and their relative phase difference is controlled by the polarization angle, enabling arbitrary superposition of the plasmonic OAM states with continuously variable amplitude ratios and phase differences. Theoretical analysis and numerical simulations demonstrate that circularly polarized illumination produces distinct OAM pure states, whereas linearly polarized light leads to equal-amplitude superposition states with structured field distributions. Moreover, rotating the polarization angle continuously adjusts the relative phase between the eigenstates and produces a predictable rotation of the resultant interference pattern. These results provide a new approach for coherent control of plasmonic OAM states and offer design guidelines for multifunctional on-chip optical field manipulation devices.
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Abstract +
Optical quantum memory plays a critical role in fields such as quantum computing, quantum sensing, and quantum communication. Cold atomic systems, owing to their excellent quantum coherence, controllability, and exceptional capability in handling weak optical fields, have emerged as one of the key platforms for faithful optical quantum state storage. Among these, cigarette-shaped, with up to 2 cm or more, cold atomic ensembles exhibit over 85 % storage effciency due to their optical depth reaching 100 or more. However, further applications are significantly hindered by the limited storage lifetimes caused by inhomogeneous residual magnetic fields along the long atomic cloud. This study analyzes the issue of atomic spin decoherence induced by non-uniform magnetic field with linear gradient, and obtain the result that storage lifetime dramatically decreases with this increasing linear gradient. Further, we demonstrate that in our two-dimensional magneto-optical trap system with a longitudinal atom-light interaction length of 2.7 cm, a DC magnetic field can provide a quantization axis, suppress the effects of inhomogeneous fields,and regulate the cycles of spin dephasing and rephasing. With the proper setting for optical pumping process of magnetic quantum levels, adjusting the pump laser power effectively controls the atomic population distribution, thereby precisely optimizes the light storage effciency at different time bins, as shown in Fig. 7(a). Based on these findings, we propose a scheme for storage of time-bin entangled photon pairs, who are prepared at two different time slots of DLCZ process. A bias magnetic field on the generation MOT (left panel of Fig. 7) induces modulation on the storage time as (a), so that read pulse exerted on rj reads only wj (j= 1, 2). Therefore, the two photonic time bins becomes distingushable and orthogonal. The retrieved photon pairs thus have fully controllable time bins for both photons. Compared to other degrees of freedom, the time encrypted photonic entanglement remains robust in long-distance network.
, , Received Date: 2025-09-10
Abstract +
Al1–xScxN, as a new generation of wurtzite-type ferroelectric material, has become a focal point in ferroelectric materials research in recent years, due to its high remnant polarization, nearly ideal rectangular polarization-electric field hysteresis loops, inherent compatibility with back-end-of-line (BEOL) CMOS processes, and stable ferroelectric phase structure. The systematic and in-depth studies on the preparation, property modulation, and device applications of this material have been conducted. This paper provides a comprehensive review of the research progress of Al1–xScxN ferroelectric thin films. Regarding the factors influencing ferroelectric properties, it emphasizes the regulatory effects of Sc doping concentration on phase transition and coercive field, explores the influences of substrate (such as Si and Al2O3) and bottom electrode (such as Pt, Mo, and HfN0.4) on thin-film orientation, stress, and interface quality, and systematically summarizes the influences of deposition conditions, film thickness, testing frequency, and temperature on ferroelectric performance. At the level of physical mechanisms governing polarization switching, this review elaborates on the domain structure, domain wall motion dynamics, nucleation sites and growth mechanisms in the Al1–xScxN switching process, revealing its microscopic response behavior under external electric fields and the mechanisms underlying fatigue failure. In terms of application prospects, Al1–xScxN thin films show significant advantages in memory devices such as ferroelectric random-access memory (FeRAM), ferroelectric field-effect transistors (FeFETs), and ferroelectric tunnel junctions (FTJs). Their high performance and integration compatibility provide strong technical support for developing next-generation, high-density, low-power ferroelectric memory and nanoelectronic devices.
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