Accepted
, , Received Date: 2025-09-12
Abstract +
Nuclear fission is a decay process by which a heavy nucleus splits into two or more lighter nuclei. It plays a crucial role in the synthesis of superheavy elements, the rapid neutron-capture process, nuclear energy application and so on. The fission barrier is an important property of heavy nuclei, because its height and width directly relate with the lifetime of heavy nuclei, and affect charge yield, mass yield, and kinetic energy of fission fragments. In our study, the potential energy curves of actinide nuclei are obtained from the relativistic density functional theory in 3D lattice when the axial symmetry, reflection symmetry and $V_4$ symmetry are broken in turn. The effects of all the quadrupole and octupole deformation degrees of freedom on the inner barrier, outer barrier, and the fission isomeric state are investigated. It is found that breaking the reflection symmetry can lower the outer fission barriers significantly, breaking the axial symmetry can lower both the inner and outer barriers, breaking the $V_4$ symmetry has little effect on the inner and outer barriers, and the fission isomeric state is almost unaffected by symmetry breaking. Based on the relativistic density functional PC-PK1 and monopole pairing interaction, our results well reproduce the empirical values of the inner and outer barriers extracted from experiments, and the energies of the fission isomeric states are slightly underestimated. All the data presented in this paper is openly available at https://www.doi.org/10.57760/sciencedb.j00213.00229 .
, , Received Date: 2025-09-02
Abstract +
Nuclear mass, β-decay half-life, and neutron-capture rate are the most important nuclear physics inputs for rapid-neutron capture process (r-process) simulations. Nuclear mass can directly impact the abundance ratio of neighboring isotopes during the (n, γ)-(γ, n) equilibrium stage. On the other hand, nuclear mass influences the predictions of β-decay half-lives and the neutron-capture rates, thus indirectly impacting the r-process simulation. Currently, only about 3000 nuclear masses have been precisely measured in experiments, and many of the nuclear masses involved in r-process simulations can only be predicted by theory models. However, when extrapolating nuclear masses towards the neutron drip line, there are large discrepancies between the predictions of different mass models, which inevitably affects the predictions of β-decay half-lives and neutron-capture rates. In this work, ten mass models are employed to systematically study the impact of nuclear mass uncertainties on β-decay half-lives and neutron-capture rates. The β-decay half-lives and neutron-capture rates are calculated by the β-decay half-life semi-empirical formula and TALYS code, respectively. It has been found that the uncertainties in nuclear mass predictions among different mass models can reach 10 MeV in the neutron-rich region; the differences between the maximum and minimum masses predicted by these models even exceed 30 MeV for some nuclei. For the predictions of β-decay energy $Q_{\beta}$ and $(\rm n,\gamma)$ reaction energy $Q_{(\rm n,\gamma)}$, there are large deviations mainly around the neutron magic numbers and close to the neutron drip line, with uncertainties about 1 MeV and 2 MeV, respectively. The impact of mass uncertainties on the β-decay half-lives is about 0.6 orders of magnitude for neutron-rich nuclei. The uncertainties of neutron-capture rates increase significantly when extrapolating towards the neutron-rich region. At the temperature of $T=10^9$ K, the average uncertainties of neutron-capture rates range over 2~3 orders of magnitude for nuclei near neutron drip line. Taking $N=50,\;82,\;126,\;184$ isotones as examples, it is found that the differences between the maximum and minimum neutron-capture rates obtained from various nuclear mass models even exceed 10 orders of magnitude for some nuclei. The $Q_{(\rm n,\gamma)}$ directly impacts the trend of the neutron-capture rates, and the neutron-capture rates are very sensitive to the uncertainties of $Q_{(\rm n,\gamma)}$ for neutron-rich nuclei. In addition, the effect of temperature on neutron-capture rates has also been investigated, and it is found that the increase in temperature can reduce the impact of mass uncertainties on the predictions of neutron-capture rates for neutron-rich nuclei. In this work, the β-decay half-lives and neutron-capture rates are calculated based on ten mass tables. Therefore, more self-consistent nuclear physics inputs will be provided for the simulation of the r-process. The datasets presented in this paper are openly available at https://www.doi.org/10.57760/sciencedb.j00213.00222 .
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Abstract +
To improve the security and efficiency of multi-image encryption, this paper proposes a hybrid encryption method that combines Interferenceless Coded Aperture Correlation Holography (I-COACH) with chaotic modulation and compressed sensing techniques. The method constructs a dual-layer encryption framework, integrating optical and digital processing to overcome the limitations of single-domain schemes.
In the optical layer, I-COACH is employed to encode multiple input images by recording their point spread holograms without interference, providing initial encryption and resistance against physical attacks. The resulting hologram is then processed using block-wise Discrete Cosine Transform (DCT) to achieve sparsity. Dual chaotic sequences perturb DCT coefficients to enhance key sensitivity and randomness. Finally, compressed sensing is applied to achieve secondary encryption while reducing the data volume by 30%, enabling efficient and secure storage or transmission. Experimental results demonstrate that the proposed method achieves an average Number of Pixels Change Rate (NPCR) of 99.44% and a Unified Average Changing Intensity (UACI) of 33.04% against differential attacks, with a ciphertext entropy of 7.9996 bit. Moreover, it exhibits excellent encryption performance in terms of key sensitivity, robustness, and resistance to statistical analysis. This method provides a practical solution for secure image application scenarios such as medical imaging and surveillance.
In the optical layer, I-COACH is employed to encode multiple input images by recording their point spread holograms without interference, providing initial encryption and resistance against physical attacks. The resulting hologram is then processed using block-wise Discrete Cosine Transform (DCT) to achieve sparsity. Dual chaotic sequences perturb DCT coefficients to enhance key sensitivity and randomness. Finally, compressed sensing is applied to achieve secondary encryption while reducing the data volume by 30%, enabling efficient and secure storage or transmission. Experimental results demonstrate that the proposed method achieves an average Number of Pixels Change Rate (NPCR) of 99.44% and a Unified Average Changing Intensity (UACI) of 33.04% against differential attacks, with a ciphertext entropy of 7.9996 bit. Moreover, it exhibits excellent encryption performance in terms of key sensitivity, robustness, and resistance to statistical analysis. This method provides a practical solution for secure image application scenarios such as medical imaging and surveillance.
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Abstract +
The modulation of electrical contact properties at the hole-selective contact represents a critical challenge for enhancing the efficiency of silicon heterojunction (SHJ) solar cells, particularly due to the complex carrier transport in the induced p-n junction at the p-layer/TCO interface. In this work, we systematically investigate the carrier transport behavior within the hole contact stack by employing TCAD numerical simulations. Both the majority- and minority-carrier analyzing models were built, based on the typical TLM (Transfer Length Method) and CSM (Cox and Strack Method) architectures, specifically. Our findings reveal that the activation energy (Ea,p) of p-layer is a decisive parameter governing the carrier transport dynamics. A lower Ea,p (e.g., 100 meV) significantly reduces the hole transport barrier at the p-layer/TCO interface, facilitating dominant band-to-band tunneling (B2BT) or dangling-bond-assisted trap-assisted tunneling (TAT-DBS), while simultaneously optimizing band bending at the i-a-Si:H/c-Si interface to enhance hole collection efficiency. These synergistic effects not only significantly reduce the contact resistivity but also suppress the parasitic electron current under high forward bias, thereby maintaining excellent carrier selectivity over a wide voltage range. From an optical perspective, a lower Ea,p broadens the selection window for transparent conductive oxide (TCO) materials, as it allows the use of TCO films with lower carrier concentration, thereby effectively mitigating parasitic absorption. This study clarifies the carrier transport mechanism at the hole-selective contact and establishes key material design criteria, providing vital theoretical guidance and practical strategies for the interface engineering and performance optimization of next-generation high-efficiency SHJ solar cells, as validated by experimental trends in recent high-efficiency devices.
Abstract +
The mass of the atomic nucleus, as one of the fundamental physical quantities of the atomic nucleus, plays an important role in understanding and researching the structure of the atomic nucleus and nuclear reactions, the basic interactions between nucleons. However, accurately predicting the mass of nuclei far from the β stability line remains a huge challenge. Based on the machine-learning-refined mass model, the newly measured atomic nucleus masses since 2022, the residual proton-neutron interaction (δVpn), and the α-decay energy of heavy nucleus are studied. It is found that: (1) For the 23 newly measured atomic nuclei, the root mean square deviations obtained by the machine-learning-refined mass models are between 0.51 and 0.58 MeV, which are significantly lower than the 3.275, 1.058, 0.752, and 0.785 MeV given by the liquid droplet model (LDM), Weizsäcker-Skyrme-4 (WS4), finite-range droplet model (FRDM), and Duflo-Zucker (DZ), respectively. (2) The δVpn of the atomic nucleus with N=Z obtained from machine-learning-refined mass models is consistent with the latest experimental data. (3) The root mean square deviations of the α-decay energy of heavy nuclei obtained from the machine-learning-refined mass models have also been significantly reduced. Furthermore, by using the Bayesian model average approach to consider the results of different machine-learning-refined mass models, a more accurate prediction can be obtained. These results demonstrate that the machine-learning-refined mass models possess good extrapolation capabilities and can provide useful insight for further researches. The datasets presented in this paper, including the Scientific Data Bank, are openly available at https://doi.org/10.57760/sciencedb.j00213.00246 (Please use the private access link https://www.scidb.cn /s/iY3iQn to access the dataset during the peer review process)
Abstract +
Rod-like Co3(HITP)2 microstructures were synthesized via a solvothermal method. By introducing reduced graphene oxide (rGO) during the synthesis, rGO/Co3(HITP)2 composites with different rGO contents (1 g/L, 1, 10 and 100μL) were prepared. The influence of rGO on the morphology, structure, and room-temperature gas-sensing properties of Co3(HITP)2 was systematically investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and gas-sensing analysis. Results indicate that the addition of rGO affects the formation of the rod-like Co3(HITP)2 structure, causing slight changes in the structural and morphology. Furthermore, the amount of rGO also impact the sensing property. Among all sensors, rGO10/Co3(HITP)2 sensor demonstrated optimal gas-sensing performance, exhibiting a response value of 4.3 to 2×10-5 (volume fraction) H2S at room temperature (~25℃) and 25% relative humidity (RH), with a detection limit of 5×10-8 (volume fraction). Furthermore, the rGO10/Co3(HITP)2 sensor showed excellent selectivity, strong anti-interference ability, and fast response/recovery characteristics (92 s/256 s). Band structure analysis revealed that the synergistic effect between rGO and Co3(HITP)2 is the main reason for the enhanced gas-sensing properties of the composite. Despite its significant sensitivity to humidity, the rGO10/Co3(HITP)2 sensor demonstrates superior performance at room-temperature compared to higher temperatures. This work provides important guidance for the efficient room-temperature detection of H2S gas.
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Abstract +
Adiabatic shear bands (ASBs) are a critical mechanism for damage initiation under high strain-rate shear impact, whereas the high-current-density-induced shear deformation mechanism of armature and rail materials remains unclear. This study employs a pulsed power source and an electromagnetic repulsion disk device to investigate the shear deformation characteristics of typical armature and rail materials under high strain rates (≥104 s-1 ) coupled with high current densities (≥108 A/m2 ). The results show that the ASB formation energy barrier decreases in the following order: pure copper, oxygen-free copper, CuCrZr alloy, Al2O3 dispersion-strengthened copper alloy, brass, and 7075 aluminum alloy. Therefore, 7075 aluminum alloy is the most prone to ASB formation, followed by brass, while other copper-based rail materials rarely exhibit ASB features. Both 7075 aluminum alloy and brass exhibit a current-induced suppression effect on crack propagation and ASB formation. Electron backscatter diffraction (EBSD) analysis reveals that numerous fine equiaxed grains are present within the shear bands of 7075 aluminum, and the texture within the bands significantly differs from that of the surrounding matrix. With increasing current density, the grain size within the band increases, while the fraction of dynamically recrystallized grains decreases markedly. The formation of ultrafine grains and the texture evolution can be reasonably explained by mechanically assisted rotational dynamic recrystallization. The results indicate that thermal softening alone is insufficient to induce ASB formation; instead, softening caused by rotational dynamic recrystallization is the dominant mechanism. The current-induced temperature rise was calculated, and the yield strength drop under high-strain-rate loading with current was measured, based on which the width of adiabatic shear bands (ASBs) under current was determined. The theoretical predictions show good agreement with experimental results. The results indicate that the temperature rise and softening effect induced by pulsed current lead to an increase in ASB width, which intensifies energy dissipation, suppresses dynamic recrystallization, and inhibits the formation of adiabatic shear bands.
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Abstract +
The optical solitons have been of considerable interest for a long time because of the important applications, such as all-optical information processing (e.g. all-optical switch, and all-logic gates, etc.), optical manipulation and beam control, etc. It was shown that an annular optical soliton may be formed when a fully coherent vortex beam propagates in strongly nonlocal nonlinear media (SNNM). The annular optical soliton with vortex has more advantages in applications than the Gaussian-like optical soliton without vortex. In practice, partially coherent beams are often encountered, and the partial coherence is one of the main features of laser beams. However, when a partially coherent vortex beam propagates in SNNM, an optical soliton cannot be formed due to partial coherence. The aim of this paper is to find a kind of partially coherent vortex soliton.
Based on the extended diffraction integral principle together with the ABCD matrix of SNNM, the analytical propagation formula of twisted partially coherent vortex（TPCV）beams in SNNM is derived in this paper. It is found that an annular optical soliton may be formed in SNNM because of the twist feature of TPCV beams, even if the spatial coherence is extremely low. The conditions for the formation of annular optical solitons of TPCV beams in SNNM are also given in this paper. In addition, it is shown that the intensity and the gradient force of annular optical solitons increase as the partial coherence of TPCV beams decreases, which may be applied in optical manipulation.
On the other hand, under certain conditions, an optical soliton may also be formed, when a TPCV beam and a twisted Gaussian Schell-model (TGSM) beam are combined coaxially and incoherently in SNNM. The conditions for the formation of optical solitons of the combined beams in SNNM are independent of the beam coherence degree, the topological charge, and the proportion of sub-beam power. Furthermore, the gradient force can be manipulated by the beam coherence degree, and the profile of optical solitons can be manipulated by the topological charge and the proportion of sub-beam power. The results obtained in this paper is useful for optical manipulation, material processing, and beam control.
Based on the extended diffraction integral principle together with the ABCD matrix of SNNM, the analytical propagation formula of twisted partially coherent vortex（TPCV）beams in SNNM is derived in this paper. It is found that an annular optical soliton may be formed in SNNM because of the twist feature of TPCV beams, even if the spatial coherence is extremely low. The conditions for the formation of annular optical solitons of TPCV beams in SNNM are also given in this paper. In addition, it is shown that the intensity and the gradient force of annular optical solitons increase as the partial coherence of TPCV beams decreases, which may be applied in optical manipulation.
On the other hand, under certain conditions, an optical soliton may also be formed, when a TPCV beam and a twisted Gaussian Schell-model (TGSM) beam are combined coaxially and incoherently in SNNM. The conditions for the formation of optical solitons of the combined beams in SNNM are independent of the beam coherence degree, the topological charge, and the proportion of sub-beam power. Furthermore, the gradient force can be manipulated by the beam coherence degree, and the profile of optical solitons can be manipulated by the topological charge and the proportion of sub-beam power. The results obtained in this paper is useful for optical manipulation, material processing, and beam control.
, , Received Date: 2025-09-01
Abstract +
Nuclear reaction rate databases serve as essential inputs for nucleosynthesis and stellar evolution modeling, directly influencing the accuracy and physical reliability of calculations in various nuclear astrophysics processes. This work provides a comprehensive review of the major reaction rate databases—REACLIB, STARLIB, and BRUSLIB—highlighting their objectives, data structures, and representative applications, and discussing their coverage, fitting methods, and uncertainty evaluation. These databases have been instrumental in advancing the standardization of nuclear reaction network calculations. However, although these databases have significantly lowered the barrier to performing network modeling, there remains substantial room for improvement in aspects such as database unit structures, update mechanisms, and organizational frameworks. For example, detailed information on the underlying nuclear physics experiments or data analyses is often not included in REACLIB. Therefore, enhancing the stored metadata warrants careful consideration, since it can significantly improve the reliability of astrophysical modeling. At the same time, the advancement of nuclear astrophysics reaction rate databases depends heavily on continuous progress at the experimental frontier. In recent years, innovative experimental techniques—such as novel 4π high-resolution detector arrays and γ–charged particle coincidence measurements—have been widely applied to studies of key nuclear astrophysics reactions, significantly expanding research capabilities. To meet the demands of cutting-edge astrophysical studies for accurate reaction rates, the real-time updating and systematic evaluation of experimental data for key reactions represent both an important opportunity and an urgent challenge for the development of modern databases. several important achievements of the JUNA Collaboration at the Jinping underground nuclear astrophysics facility, where low-background experiments have been conducted, are also presented in this paper. These new low-energy measurements, when compared with traditional extrapolations used in databases, are found to provide more direct constraints on key reactions in nuclear astrophysics and to offer crucial experimental support for the continuous optimization of future databases.
, , Received Date: 2025-10-13
Abstract +
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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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