Showing 1–50 of 171 results for author: Du, J

Radio Frequency Field-Induced Enhancement of Detection Sensitivity in Silicon Nanowire Sensors

Authors: Ang Liu, Jingsong Shang, Jiangang J. Du, Shyamsunder Erramilli, Pritiraj Mohanty

Abstract: Sensitive biomarker detection in physiological fluids is often limited by Debye screening, which suppresses electrostatic signals at sensor surfaces. Here we report a sensing approach based on flexoelectric resonance in silicon nanowire field-effect transistors. An applied radiofrequency field induces strain gradients in the nanowires, generating flexoelectric polarization that is amplified at res… ▽ More Sensitive biomarker detection in physiological fluids is often limited by Debye screening, which suppresses electrostatic signals at sensor surfaces. Here we report a sensing approach based on flexoelectric resonance in silicon nanowire field-effect transistors. An applied radiofrequency field induces strain gradients in the nanowires, generating flexoelectric polarization that is amplified at resonant frequencies. This effect enhances the sensitivity of conductance measurements to small surface charge variations associated with biomolecular binding. Using C-reactive protein as a model biomarker, we observe an order-of-magnitude improvement in detection sensitivity compared to conventional operation, with a 62% conductance increase versus 30% without radiofrequency modulation. The high-frequency field also perturbs the electrical double layer, reducing Debye screening in high-ionic-strength environments. These combined effects enable direct biomarker detection without sample dilution. This work establishes flexoelectric resonance as a general strategy for improving nanoscale biosensing performance in physiologically relevant conditions. △ Less

Submitted 30 April, 2026; originally announced April 2026.

Comments: 32 pages, 7 figures

Ultrafast electron vortex produced by a grating made of light

Authors: Zichen Li, Hao Liang, Yuan Gu, Jiaye Zhang, Aofan Lin, Juan Du, Sina Jacob, Maksim Kunitski, Till Jahnke, Sebastian Eckart, Reinhard Dörner, Kang Lin

Abstract: The generation of vortex matter waves carrying quantized orbital angular momentum is challenging and relies heavily on the material nanofabrication methods due to their extremely small de-Broglie wavelengths. Here, we introduce an all-optical method for generating an electron vortex by diffraction through a grating made of light. We realize the orbital angular momentum transfer between free electr… ▽ More The generation of vortex matter waves carrying quantized orbital angular momentum is challenging and relies heavily on the material nanofabrication methods due to their extremely small de-Broglie wavelengths. Here, we introduce an all-optical method for generating an electron vortex by diffraction through a grating made of light. We realize the orbital angular momentum transfer between free electrons and photons by stimulated Compton scattering. The transferred angular momentum quantum number can be freely tuned. The method can be generalized to a broad range of charged particles, neutral atoms, and molecules of diverse masses. Our results open up novel opportunities for applications in free electron lasers and ultrafast electron microscopy by utilizing the orbital angular momentum degree of freedom of free electrons. △ Less

Submitted 28 April, 2026; originally announced April 2026.

The properties of plasma sheath containing the primary electrons with a Cairns-distribution

Authors: Yida Zhang, Jiulin Du

Abstract: We study the properties of plasma sheath containing the cold positive ions, the secondary electrons, and the primary electrons with a Cairns-distribution (a non-thermal velocity-distribution). We derive the generalized Bohm criterion and Bohm speed, the new floating potential at the wall, and the new critical secondary electron emission coefficient. We show that these properties of the plasma shea… ▽ More We study the properties of plasma sheath containing the cold positive ions, the secondary electrons, and the primary electrons with a Cairns-distribution (a non-thermal velocity-distribution). We derive the generalized Bohm criterion and Bohm speed, the new floating potential at the wall, and the new critical secondary electron emission coefficient. We show that these properties of the plasma sheath depend significantly on the a-parameter in the non-thermal a-distribution, and so they are generally different from those of the plasma sheath if the primary electrons were assumed to be a Maxwellian distribution. △ Less

Submitted 18 March, 2026; v1 submitted 16 March, 2026; originally announced March 2026.

Comments: 13 pages, 7 figures, 25 references

Journal ref: Entropy 28 (2026) 237

A Stable, High-Order Time-Stepping Scheme for the Drift-Diffusion Model in Modern Solar Cell Simulation

Authors: Jun Du, Jun Yan

Abstract: This paper presents a one-dimensional transient drift--diffusion simulator for advanced solar cells, integrating a structure-preserving finite-volume spatial discretization with Scharfetter--Gummel--type fluxes and a high-order, L-stable implicit Runge--Kutta (Radau IIA) temporal integrator. The scheme ensures local charge conservation, handles sharp material interfaces, and achieves second-order… ▽ More This paper presents a one-dimensional transient drift--diffusion simulator for advanced solar cells, integrating a structure-preserving finite-volume spatial discretization with Scharfetter--Gummel--type fluxes and a high-order, L-stable implicit Runge--Kutta (Radau IIA) temporal integrator. The scheme ensures local charge conservation, handles sharp material interfaces, and achieves second-order spatial and fifth-order temporal convergence. Its accuracy is verified against the classical depletion approximation in $p$--$n$ junction and validated through excellent agreement with the established simulator for an organic photovoltaic device. The framework's extensibility is demonstrated by incorporating exciton kinetics in organic solar cells, capturing multi-timescale dynamics, and by modeling mobile ions in perovskite solar cells, reproducing characteristic $\tmem{J}$--$\tmem{V}$ hysteresis without empirical parameters. This work provides a robust, high-order numerical foundation for simulating coupled charge, exciton, and ion transport in next-generation photovoltaic devices. △ Less

Submitted 9 March, 2026; originally announced March 2026.

Comments: 16 pages, 12 figures, 5 tables

Extending gPET for Multi-Layer PET Simulation

Authors: Satzhan Sitmukhambetov, Junwei Du, Mingwu Jin, Yujie Chi

Abstract: Depth-of-interaction (DOI) encoding is an effective strategy for reducing parallax error and preserving spatial resolution in positron emission tomography (PET), particularly in compact small-animal scanners. To enable efficient simulation-driven design of DOI-capable systems, we extend the GPU-accelerated Monte Carlo toolkit gPET to support flexible multi-layer detector geometries. The original t… ▽ More Depth-of-interaction (DOI) encoding is an effective strategy for reducing parallax error and preserving spatial resolution in positron emission tomography (PET), particularly in compact small-animal scanners. To enable efficient simulation-driven design of DOI-capable systems, we extend the GPU-accelerated Monte Carlo toolkit gPET to support flexible multi-layer detector geometries. The original three-level hierarchical detector model in gPET (panel-module-crystal) was expanded by introducing an intermediate "layer" level, enabling parameterized modeling of stacked scintillator architectures. The photon transport algorithm was correspondingly updated to sample interactions across multiple layers and detector panels while preserving GPU-efficient memory usage. The framework was validated using three scanner configurations: a conventional single-layer ring (H2RSPET-1CL), an aligned split-layer design (H2RSPET-1CL-split), and an offset dual-layer design (H2RSPET-2CL). System performance was evaluated following NEMA NU4-2008 protocols using sensitivity, spatial resolution, and Derenzo phantom simulations with CASToR-based maximum likelihood expectation maximization reconstruction. The H2RSPET-1CL and H2RSPET-1CL-split configurations produced statistically identical hit distributions, while H2RSPET-2CL exhibited the expected offset interaction patterns. Sensitivity of H2RSPET-2CL remained comparable to H2RSPET-1CL, generally within about 2-5 percent, while radial spatial resolution improved substantially (0.8-1.6 mm vs. 1.0-4.2 mm from the center to a 50 mm radial offset). Runtime performance remained essentially unchanged between configurations. The extended gPET framework therefore enables fast and flexible simulation of multi-layer PET detectors and supports efficient optimization of DOI-enabled PET system designs. △ Less

Submitted 7 March, 2026; originally announced March 2026.

Sub-1-Angstrom-Resolution Imaging Reveals Phase Contrast Transition in Ice Ih Caused by Basal Stacking Faults

Authors: Jingshan S. Du, Suvo Banik, Lehan Yao, Shuai Zhang, Subramanian K. R. S. Sankaranarayanan, James J. De Yoreo

Abstract: Phase-contrast transmission electron microscopy (TEM) of hexagonal ice (Ih) along [0001] sometimes shows a honeycomb-like pattern, often interpreted as individual oxygen columns in single crystals. Here, we show that this pattern commonly arises from intrinsic basal stacking faults instead. A translational boundary separating domains of comparable thickness, with an in-plane offset of… ▽ More Phase-contrast transmission electron microscopy (TEM) of hexagonal ice (Ih) along [0001] sometimes shows a honeycomb-like pattern, often interpreted as individual oxygen columns in single crystals. Here, we show that this pattern commonly arises from intrinsic basal stacking faults instead. A translational boundary separating domains of comparable thickness, with an in-plane offset of $(\frac{2}{3} a_{1} + \frac{1}{3} a_{2})$, produces this honeycomb-like contrast. Stacking domains translated in nonequivalent directions yields patterns resembling cubic ice (Ic) along [111] but with a 3-fold symmetry. We imaged this structure at a record-breaking line resolution of 89 picometers, finer than the O-H covalent bond length. These findings highlight the defect tolerance of ice's molecular packing and clarify the structural relationships among hexagonal, stacking-disordered, and cubic ice phases. This resolution milestone opens new avenues for characterizing subtle structural perturbations of water in the solid state. △ Less

Submitted 23 February, 2026; v1 submitted 16 February, 2026; originally announced February 2026.

Comments: 17 pages, 4 figures, and 2 appendices. Including a Supplemental Material with 2 figures

Eliminating Delocalization Error through Localized Orbital Scaling Correction with Orbital Relaxation from Linear Response

Authors: Yichen Fan, Jincheng Yu, Jiayi Du, Weitao Yang

Abstract: Despite the great success that Kohn-Sham density functional theory (KS-DFT) has achieved, the delocalization error remains a major challenge for commonly used density functional approximations (DFAs), resulting in systematic errors in ionization energies, electron affinities, band structures, and charge distributions. A recently developed localized orbital scaling correction (LOSC) method, namely… ▽ More Despite the great success that Kohn-Sham density functional theory (KS-DFT) has achieved, the delocalization error remains a major challenge for commonly used density functional approximations (DFAs), resulting in systematic errors in ionization energies, electron affinities, band structures, and charge distributions. A recently developed localized orbital scaling correction (LOSC) method, namely linear response LOSC (lrLOSC), addresses these challenges by incorporating a functional correction that includes the screening effect and orbital localization within the LOSC framework. The method has been shown to provide accurate descriptions of bulk systems and core-level binding energies in small molecular systems. In this work, we extend the applicability of lrLOSC to a broader range of molecular systems, spanning various sizes, with a focus on the corrections to valence orbital energies and total energies. To enable the calculation of large chemical systems, we developed an efficient implementation of lrLOSC with computational costs comparable to standard KS-DFT calculations. Numerical results show that, while screening provides modest improvements for small molecules, it becomes critical for achieving high accuracy in larger molecules, from linear to three-dimensional systems. With the screening effect well captured in a unified way, lrLOSC provides accurate descriptions for a wide range of chemical systems, including organic molecular systems of varying sizes and transition-metal oxide complexes, establishing it as a powerful tool for enhancing the reliability of computational simulations of chemical systems. △ Less

Submitted 13 July, 2026; v1 submitted 11 February, 2026; originally announced February 2026.

From microscopic social force models to macroscopic continuum models for pedestrian flow

Authors: Liangze Yang, Hui Yu, Jie Du

Abstract: The pedestrian flow is one of the most complex systems, involving large populations of interacting agents. Models at microscopic and macroscopic scales offer different advantages for studying related problems. In general, microscopic models can describe interaction forces at the individual level. Macroscopic models, on the other hand, provide analytical insights into global interactions and long-t… ▽ More The pedestrian flow is one of the most complex systems, involving large populations of interacting agents. Models at microscopic and macroscopic scales offer different advantages for studying related problems. In general, microscopic models can describe interaction forces at the individual level. Macroscopic models, on the other hand, provide analytical insights into global interactions and long-term overall dynamics, along with efficient numerical simulations and predictions. However, the relationship between models at different scales has rarely been explored. In this study, based on the original microscopic social force model with a reactive optimal route choice strategy, we first derive kinetic equations at the mesoscopic level. By varying the interaction force in different scenarios, we then derive several continuum models at the macroscopic level. Finally, numerical examples are given to evaluate the behaviors of the social force model and our continuum models. △ Less

Submitted 23 January, 2026; originally announced January 2026.

MSC Class: 35K20; 35Q70; 35Q91; 91C20; 92B05; 92D25

Towards accurate predictions of bond-selective fluorescence spectra

Authors: Philip A. Kocheril, Ryan E. Leighton, Noor Naji, Dongkwan Lee, Haomin Wang, Jiajun Du, Lu Wei

Abstract: Vibrational-encoded fluorescence spectro-microscopies are emerging as powerful tools for studying molecular vibrations with the unparalleled sensitivity of fluorescence spectroscopy. We recently described one such technique, termed bond-selective fluorescence-detected infrared-excited (BonFIRE) spectro-microscopy. Currently, prospects of BonFIRE towards rational molecular design are limited, but t… ▽ More Vibrational-encoded fluorescence spectro-microscopies are emerging as powerful tools for studying molecular vibrations with the unparalleled sensitivity of fluorescence spectroscopy. We recently described one such technique, termed bond-selective fluorescence-detected infrared-excited (BonFIRE) spectro-microscopy. Currently, prospects of BonFIRE towards rational molecular design are limited, but they have the potential to be assisted by computational tools. In this Perspective, we provide a brief overview of the theory of BonFIRE spectroscopy. We then describe a fully automated computational pipeline for calculating BonFIRE spectra, reproducing key features of experimental results. Finally, we highlight a few potential applications of computational methods for vibrational-encoded fluorescence spectro-microscopies and their broader implications for chemistry and biology. △ Less

Submitted 16 January, 2026; originally announced January 2026.

Single-molecule Scale Nuclear Magnetic Resonance Spectroscopy using a Robust Near-Infrared Spin Sensor

Authors: Yu Chen, Qi Zhang, Yuanhong Teng, Chihang Luo, Zhijie Li, Jinpeng Liu, Ya Wang, Fazhan Shi, Jiangfeng Du

Abstract: Nuclear magnetic resonance (NMR) at the single-molecule level with atomic resolution holds transformative potential for structural biology and surface chemistry. Near-surface solid-state spin sensors with optical readout ability offer a promising pathway toward this goal. However, their extreme proximity to target molecules demands exceptional robustness against surface-induced perturbations. Furt… ▽ More Nuclear magnetic resonance (NMR) at the single-molecule level with atomic resolution holds transformative potential for structural biology and surface chemistry. Near-surface solid-state spin sensors with optical readout ability offer a promising pathway toward this goal. However, their extreme proximity to target molecules demands exceptional robustness against surface-induced perturbations. Furthermore, life science applications require these sensors to operate in biocompatible spectral ranges that minimize photodamage. In this work, we demonstrate that the PL6 quantum defect in 4H silicon carbide (4H-SiC) can serve as a robust near-infrared spin sensor. This sensor operates at tissue-transparent wavelengths and exhibits exceptional near-surface stability even at depth of 2 nm. Using shallow PL6 centers, we achieve nanoscale NMR detection of proton ($\mathrm{^{1}H}$) spins in immersion oil and fluorine ($\mathrm{^{19}F}$) spins in Fomblin, attaining a detection volume of $\mathrm{(3~nm)^3}$ and a sensitivity reaching the requirement for single-proton spin detection. This work establishes 4H-SiC quantum sensors as a compelling platform for nanoscale magnetic resonance, with promising applications in probing low-dimensional water phases, protein folding dynamics, and molecular interactions. △ Less

Submitted 10 December, 2025; originally announced December 2025.

Comments: 16 pages, 4 figures

Parallel accelerated electron paramagnetic resonance spectroscopy using diamond sensors

Authors: Zhehua Huang, Zhengze Zhao, Fei Kong, Zhecheng Wang, Pengju Zhao, Xiangtian Gong, Xiangyu Ye, Ya Wang, Fazhan Shi, Jiangfeng Du

Abstract: The nitrogen-vacancy (NV) center can serve as a magnetic sensor for electron paramagnetic resonance (EPR) measurements. Benefiting from its atomic size, the diamond chip can integrate a tremendous amount of NV centers to improve the magnetic-field sensitivity. However, EPR spectroscopy using NV ensembles is less efficient due to inhomogeneities in both sensors and targets. Spectral line broadening… ▽ More The nitrogen-vacancy (NV) center can serve as a magnetic sensor for electron paramagnetic resonance (EPR) measurements. Benefiting from its atomic size, the diamond chip can integrate a tremendous amount of NV centers to improve the magnetic-field sensitivity. However, EPR spectroscopy using NV ensembles is less efficient due to inhomogeneities in both sensors and targets. Spectral line broadening induced by ensemble averaging is even detrimental to spectroscopy. Here we show a kind of cross-relaxation EPR spectroscopy at zero field, where the sensor is tuned by an amplitude-modulated control field to match the target. The modulation makes detection robust to the sensor's inhomogeneity, while zero-field EPR is naturally robust to the target's inhomogeneity. We demonstrate an efficient EPR measurement on an ensemble of roughly 30000 NV centers. Our method shows the ability to not only acquire unambiguous EPR spectra of free radicals, but also monitor their spectroscopic dynamics in real time. △ Less

Submitted 9 December, 2025; originally announced December 2025.

Comments: 15 pages, 4 figures in the maintext

Journal ref: Phys. Rev. Lett. 134, 130801 (2025)

Ion-acoustic shock and solitary waves in magnetized plasma with Cairns-Gurevich distribution electrons

Authors: Rui Huo, Jiulin Du

Abstract: The propagation properties of ion-acoustic solitary and shock waves in the magnetized viscous plasma with nonthermal trapped electrons are investigated. The Cairns-Gurevich distribution as the electron distribution is considered to describe the plasma nonthermality and particle trapping. By adopting the reductive perturbation technique, we derived the nonlinear Schamel-Korteweg-de Vries-Burgers (S… ▽ More The propagation properties of ion-acoustic solitary and shock waves in the magnetized viscous plasma with nonthermal trapped electrons are investigated. The Cairns-Gurevich distribution as the electron distribution is considered to describe the plasma nonthermality and particle trapping. By adopting the reductive perturbation technique, we derived the nonlinear Schamel-Korteweg-de Vries-Burgers (SKdVB) equation, and then obtained the ion-acoustic shock and solitary wave solutions of the SKdVB equation for different limiting cases. It is found that the impact of nonthermal parameter α, external magnetic field Ω, obliqueness lz, wave speed U0, and the ion kinematic viscosity η0 can significantly change the characteristics of the shock and solitary waves. These results may be useful for better understanding the propagation of nonlinear structures in space (i.e. Earth's magnetosphere and ionosphere, auroral regions) and laboratory plasma with nonthermal trapped electrons. △ Less

Submitted 9 December, 2025; v1 submitted 4 December, 2025; originally announced December 2025.

Comments: 15 pages, 10 figures

Journal ref: Commun. Theor. Phys. 77 (2025) 065501

Firehose instability in the space plasma with anisotropic Cairns-distribution electrons

Authors: Rui Huo, Jiulin Du

Abstract: We study the electron firehose mode propagating parallel to the ambient magnetic field in the space plasma with anisotropic Cairns-distribution electrons. The dispersion relation, the wave frequency and the growth rate of electron firehose mode are derived, and the condition for onset of the firehose instability is obtained. We show that the wave frequency and the growth rate both depend significa… ▽ More We study the electron firehose mode propagating parallel to the ambient magnetic field in the space plasma with anisotropic Cairns-distribution electrons. The dispersion relation, the wave frequency and the growth rate of electron firehose mode are derived, and the condition for onset of the firehose instability is obtained. We show that the wave frequency and the growth rate both depend significantly on the parameters, such as the parallel electron beta , the nonthermal parameter Λ and the electron temperature anisotropy Ae , and the anisotropic Cairns-distribution electrons change the instability condition. The numerical analyses show that the wave frequency and the growth rate of the electron firehose mode increase with increase of the parameters. The results may be helpful for understanding the firehose instability in space plasma environments. △ Less

Submitted 9 December, 2025; v1 submitted 4 December, 2025; originally announced December 2025.

Comments: 11 pages, 6 figures

Journal ref: Eur. Phys. J. Plus. 139 (2024) 604

Kinetic Alfvén waves in the temperature anisotropic space plasma with a kappa-Maxwellian distribution

Authors: Rui Huo, Jiulin Du, Ran Guo

Abstract: The dispersion and damping rate of kinetic Alfvén waves are studied in temperature anisotropic space plasma with kappa-Maxwellian distribution. Employing a kinetic approach, the wave frequency and damping rate of kinetic Alfvén waves and the modified ion acoustic waves are derived in a low \b{eta} plasma, which both depend on the parameters \k{appa} and . The numerical analyses show that the wave… ▽ More The dispersion and damping rate of kinetic Alfvén waves are studied in temperature anisotropic space plasma with kappa-Maxwellian distribution. Employing a kinetic approach, the wave frequency and damping rate of kinetic Alfvén waves and the modified ion acoustic waves are derived in a low \b{eta} plasma, which both depend on the parameters \k{appa} and . The numerical analyses show that the wave frequency of kinetic Alfvén waves is larger in kappa-Maxwellian plasma than that in Maxwellian case. The wave frequency of the modified ion acoustic waves in kappa-Maxwellian plasma is larger in the short-wave region but smaller in the long-wave region than that in Maxwellian case. Again, we found that the damping rate of kinetic Alfvén waves in kappa-Maxwellian plasma is stronger than that in Maxwellian case. The damping rate of modified ion acoustic waves in kappa-Maxwellian plasma is stronger in the short-wave region but weaker in the long-wave region than that in Maxwellian case. The impact of the parameter on the two modes is relatively small because we consider the low \b{eta} case. These results are helpful for us to understand better the characteristics of kinetic Alfvén waves in space plasma. △ Less

Submitted 9 December, 2025; v1 submitted 4 December, 2025; originally announced December 2025.

Comments: 13 pages, 8 figures

Journal ref: Chin. J. Phys. 90 (2024) 199

Single-cell identification with quantum-enhanced nuclear magnetic resonance

Authors: Zhiyuan Zhao, Qian Shi, Shaoyi Xu, Xiangyu Ye, Mengze Shen, Jia Su, Ya Wang, Tianyu Xie, Qingsong Hu, Fazhan Shi, Jiangfeng Du

Abstract: Identification of individual cells within heterogeneous populations is essential for biomedical research and clinical diagnostics. Conventional labeling-based sorting methods, such as fluorescence-activated cell sorting and magnetic-activated cell sorting, enable precise sorting when reliable markers are available. However, their applicability is limited in cells lacking defined markers or sensiti… ▽ More Identification of individual cells within heterogeneous populations is essential for biomedical research and clinical diagnostics. Conventional labeling-based sorting methods, such as fluorescence-activated cell sorting and magnetic-activated cell sorting, enable precise sorting when reliable markers are available. However, their applicability is limited in cells lacking defined markers or sensitive to labeling, as labeling can compromise cellular viability and function. We present a single-cell identification approach using quantum-enhanced NMR with diamond nitrogen-vacancy centers for label-free detection of intracellular proton ($^1$H) signals. Using this method, we distinguish two human tumor cell lines by their proton spin-lattice ($T_1$) relaxation times, which serve as a cell-intrinsic physicochemical signature. It lays the groundwork for label-free sorting applications in rare cell analysis, personalized medicine, and single-cell diagnostics. △ Less

Submitted 8 December, 2025; originally announced December 2025.

Comments: 23 pages, 4 figures

Dual Role of Nb in Defect-Mediated Strength and Ductility of γ-TiAl Alloys

Authors: Zhiqiang Zhao, Siyao Shuang, Kepeng Ouyang, Maolin Yu, Junping Du, Liangli Chu, Xiaokai Chen, Shigenobu Ogata, Wanlin Guo, Zhuhua Zhang, Yong-Wei Zhang

Abstract: The origin of the superior high-temperature strength of γ-TiAl with high Nb addition remains highly controversial, largely due to the unclear role of Nb atoms. Using large-scale hybrid Monte Carlo and molecular dynamics simulations with a self-developed neural network potential,we show that Nb atoms predominantly occupy Ti sites and form short-range order with neighboring Al atoms, but a non-negli… ▽ More The origin of the superior high-temperature strength of γ-TiAl with high Nb addition remains highly controversial, largely due to the unclear role of Nb atoms. Using large-scale hybrid Monte Carlo and molecular dynamics simulations with a self-developed neural network potential,we show that Nb atoms predominantly occupy Ti sites and form short-range order with neighboring Al atoms, but a non-negligible fraction also occupies Al sites (NbAl) and promotes the formation of antisite defects (TiAl). Both the NbAl and TiAl antisites exceptionally reduce stacking fault energies and facilitate deformation twinning, thereby enhancing plasticity. Meanwhile, these substitutional and antisite defects also increase the Peierls stress of both screw and edge dislocations, which hinders dislocation motion to cause pronounced solid-solution strengthening. This work provides mechanistic insights into the dual role of Nb in enhancing both strength and ductility in γ-TiAl and further offers guidance for defect and composition engineering in advanced alloy systems. △ Less

Submitted 29 November, 2025; originally announced December 2025.

Comments: 24 pages,6 figures

Journal ref: Acta Materialia, 313, 122290 (2026)

Integrated polarization-entangled photon source for wavelength-multiplexed quantum networks

Authors: Xiaodong Shi, Yue Li, Jinyi Du, Lin Zhou, Ran Yang, En Teng Lim, Sakthi Sanjeev Mohanraj, Mengyao Zhao, Xu Chen, Xiaojie Wang, Guangxing Wu, Hao Hao, Veerendra Dhyani, Sihao Wang, Alexander Ling, Di Zhu

Abstract: Entangled photons are fundamental resources for quantum communication, computing, and networking. Among them, polarization-entangled photon pairs play an important role due to their straightforward state manipulation and direct use in quantum key distribution, teleportation, and network protocols. However, realizing compact, efficient, and scalable polarization-entangled sources that meet the requ… ▽ More Entangled photons are fundamental resources for quantum communication, computing, and networking. Among them, polarization-entangled photon pairs play an important role due to their straightforward state manipulation and direct use in quantum key distribution, teleportation, and network protocols. However, realizing compact, efficient, and scalable polarization-entangled sources that meet the requirements of practical deployment remains a major challenge. Here, we present a simple yet high-performance on-chip polarization-entangled photon-pair source on thin-film lithium niobate (TFLN). Our device employs dual quasi-phase matching (D-QPM) that sequentially supports type-0 and type-I spontaneous parametric down-conversion in a single nanophotonic waveguide, eliminating the need for interferometers, polarization rotators, or other complex circuits. The source directly produces high-fidelity Bell states with broad bandwidth, high brightness, and low noise. Using this integrated platform, we realize wavelength-multiplexed entanglement distribution in a four-user quantum network deployed over metropolitan fiber links up to 50 km. These results establish a robust and scalable pathway toward practical quantum communication systems and multi-user quantum mesh networks based on integrated photonics. △ Less

Submitted 5 August, 2026; v1 submitted 27 November, 2025; originally announced November 2025.

Achieving Empirical Potential Efficiency with DFT Accuracy: A Neuroevolution Potential for the $α$-Fe--C--H System

Authors: Fan-Shun Meng, Shuhei Shinzato, Zhiqiang Zhao, Jun-Ping Du, Lei Gao, Zheyong Fan, Shigenobu Ogata

Abstract: A neuroevolution potential (NEP) for the ternary $α$-Fe--C--H system was developed based on a database generated from spin-polarized density functional theory (DFT) calculations, achieving empirical potential efficiency with DFT accuracy. At the same power consumption, simulation speeds using NEP are comparable to, or even faster than, those with bond order potentials. The NEP achieves DFT-level a… ▽ More A neuroevolution potential (NEP) for the ternary $α$-Fe--C--H system was developed based on a database generated from spin-polarized density functional theory (DFT) calculations, achieving empirical potential efficiency with DFT accuracy. At the same power consumption, simulation speeds using NEP are comparable to, or even faster than, those with bond order potentials. The NEP achieves DFT-level accuracy across a wide range of scenarios commonly encountered in studies of $α$-Fe- and $α$-Fe--C under hydrogen environments. The NEP enables large-scale atomistic simulations with DFT-level accuracy at the cost of empirical potentials, offering a practical tool to study hydrogen embrittlement in steel. △ Less

Submitted 22 October, 2025; v1 submitted 20 October, 2025; originally announced October 2025.

Comments: 16 pages, 7 figures

MSC Class: 82B ACM Class: J.2

Broadband-operational orbital angular momentum generation in nonlocal metasurfaces with maximum efficiency approaching 80%

Authors: Keren Wang, Kaili Sun, Jing Du, Peijuan Dai, Hao Zhou, Lujun Huang, Zhanghua Han, Wei Wang

Abstract: Nonlocal metasurfaces provide a compact route to generating momentum-space optical vortices but are limited by steep dispersion typically associated with high-quality (Q) factor resonances, resulting in narrowband and inefficient operation. Here, we introduce a reflection-type nonlocal metasurface that hybrid-couples a bound state in the continuum (BIC) with two degeneracy points (DPs). This engin… ▽ More Nonlocal metasurfaces provide a compact route to generating momentum-space optical vortices but are limited by steep dispersion typically associated with high-quality (Q) factor resonances, resulting in narrowband and inefficient operation. Here, we introduce a reflection-type nonlocal metasurface that hybrid-couples a bound state in the continuum (BIC) with two degeneracy points (DPs). This engineered interaction enables on-demand control of dispersion, radiative Q-factors, and polarization states of guided resonances, yielding quasi-flat dispersion and enhanced scattering strength. Full-wave simulations predict near-unity on-resonance conversion and overall efficiencies above 90%, representing a three- to fourfold efficiency improvement and more than fifteenfold bandwidth expansion over conventional designs. Experiments confirm broadband operation from 1480 to 1600 nm, achieving peak efficiency approaching 80% and orbital angular momentum (OAM) purity up to 91.7% under flat-top illumination, while suppressing edge effects and mitigating positional sensitivity and numerical-aperture (NA) dependence. As a proof of concept, we demonstrate direct conversion of zero-order Bessel beams into OAM Bessel (perfect vortex) beams with enhanced wavelength tunability, underscoring the versatility of this approach over diverse illumination conditions. This record-high performance establishes a practical and scalable pathway toward broadband, high-efficiency vortex generation, opening new opportunities across high-dimensional optical communications, advanced imaging, and quantum photonics. △ Less

Submitted 5 October, 2025; originally announced October 2025.

Anomalous Spontaneous Emission Enhancement by Non-Hermitian Momentum-Space Bound States in the Continuum

Authors: Keren Wang, Jing Du, Wei Wang

Abstract: Conventional Purcell theory emphasizes high quality factors (Q) for spontaneous emission (SE) enhancement in cavities, but overlooks collective Bloch mode effects in periodic nanostructures like photonic crystal slabs. We introduce a unified temporal coupled-mode framework to compute Purcell and photoluminescence factors through momentum-space integration, revealing anomalous SE enhancement by non… ▽ More Conventional Purcell theory emphasizes high quality factors (Q) for spontaneous emission (SE) enhancement in cavities, but overlooks collective Bloch mode effects in periodic nanostructures like photonic crystal slabs. We introduce a unified temporal coupled-mode framework to compute Purcell and photoluminescence factors through momentum-space integration, revealing anomalous SE enhancement by non-Hermitian momentum-space bound states in the continuum (BICs). In silicon gratings with comparable effective mode volumes, this yields substantial SE enhancement in low-Q regimes--defying the traditional high-Q paradigm and inversely correlated with system Q--while emission rates are stably twice the photoluminescence, eliminating critical coupling requirements. Unique spectral profiles, contradicting Lorentzian/Fano assumptions, arise from collective mode interactions. Full-wave simulations confirm these challenges to conventional wisdom, with non-Hermitian BICs outperforming high-Q designs across broad numerical apertures. This establishes a novel paradigm leveraging non-Hermiticity and topological protection for robust, bright emitters, redefining nanophotonic applications in lasers and light-emitting diodes △ Less

Submitted 5 October, 2025; v1 submitted 30 September, 2025; originally announced October 2025.

Journal ref: ACS Photonics 2026 13 (2), 560-566

Dynamical phase evolution of Coulomb-focused electrons in strong-field ionization probed by a standing light wave

Authors: Yuan Gu, Hao Liang, Weiran Zheng, Aofan Lin, Jiaye Zhang, Zichen Li, Juan Du, Lei Ying, Peilun He, Jan-Michael Rost, Sina Jacob, Maksim Kunitski, Till Jahnke, Sebastian Eckart, Kang Lin, Reinhard Dörner

Abstract: We investigate the dynamical phase evolution of Coulomb-focused electrons in strong-field ionization. We diffract the electrons with an ultrashort standing light wave to track their time-dependent phase. Our findings show that low-energy electrons exhibit a unique chromosome-shaped diffraction pattern, distinct from higher-energy electrons. Our numerical model quantitatively reproduces the experim… ▽ More We investigate the dynamical phase evolution of Coulomb-focused electrons in strong-field ionization. We diffract the electrons with an ultrashort standing light wave to track their time-dependent phase. Our findings show that low-energy electrons exhibit a unique chromosome-shaped diffraction pattern, distinct from higher-energy electrons. Our numerical model quantitatively reproduces the experimental results, confirming this pattern maps the electron's time-dependent phase evolution as it escapes from a Coulomb potential. Our pulsed diffraction grating technique offers a new way to sense an electron's quantum phase without interfering its release mechanism. △ Less

Submitted 16 September, 2025; originally announced September 2025.

Theoretical and experimental study of the correlation between pulsed light repetition frequency and electric field measurement

Authors: Ke Di, Chenglin Ye, Meihui Liu, Pengfei Shi, Yu Liu, Jun He, Jiajia Du

Abstract: We propose a novel approach for improving the performance of Rydberg atom sensors by utilizing the repetition frequency of pulsed lasers, which has been validated through experimental testing. Rydberg atoms excited by pulsed lasers are influenced significantly by the repetition frequency of the pulsed laser on the Rydberg state population. As the number of Rydberg atoms increases, the measurement… ▽ More We propose a novel approach for improving the performance of Rydberg atom sensors by utilizing the repetition frequency of pulsed lasers, which has been validated through experimental testing. Rydberg atoms excited by pulsed lasers are influenced significantly by the repetition frequency of the pulsed laser on the Rydberg state population. As the number of Rydberg atoms increases, the measurement sensitivity of the sensor to external fields also increases, directly enhancing the performance of the sensor. This paper investigates the response of the sensor to the same electric field when the repetition frequency of the pulsed laser is at the MHz level, with a focus on its gain effects on the broadcast communication frequency bands of 66MHz and 88MHz. This research substantiates the distinctive benefits of pulsed light for Rydberg atom excitation, thereby enhancing the efficacy of the detection of feeble signals and introducing a new approach for the development of more sensitive atomic sensors. △ Less

Submitted 28 July, 2026; v1 submitted 25 August, 2025; originally announced August 2025.

Nanosecond-latency all-optical fiber sensing with in-sensor computing

Authors: Yu Tao, Yangyang Wan, Ziwen Long, Wenjia Zhang, Jiangbing Du, Zuyuan He

Abstract: Optical fiber sensing plays a crucial role in modern measurement systems and holds significant promise for a wide range of applications. This potential, though, has been fundamentally constrained by the intrinsic latency and power limitations associated with electronic signal processing. Here, we propose an all-optical fiber sensing architecture with in-sensor computing (AOFS-IC) that achieves ful… ▽ More Optical fiber sensing plays a crucial role in modern measurement systems and holds significant promise for a wide range of applications. This potential, though, has been fundamentally constrained by the intrinsic latency and power limitations associated with electronic signal processing. Here, we propose an all-optical fiber sensing architecture with in-sensor computing (AOFS-IC) that achieves fully optical-domain sensing signal demodulation at the speed of light. By integrating a scattering medium with an optimized diffractive optical network, AOFS-IC enables linear mapping of physical perturbations to detected intensity, and sensing results can be directly read out without electronic processing. The proposed system maintains high accuracy across various sensing tasks, providing sub-nano strain resolution and 100% torsional angle classification accuracy, as well as multiplexed sensing of multiple physical quantities, and performing multi-degree-of-freedom robot arm monitoring. AOFS-IC eliminates computing hardware requirements while providing <3 ns demodulation delay, which is more than 2 orders of magnitude faster than conventional fiber optic sensing systems. This work demonstrates the potential of next-generation optical sensing systems empowered by all-optical computing, and paves the way for expanded applications of fiber sensing through the integration of fully optical components, ultrafast measurement speed, and low power consumption. △ Less

Submitted 21 July, 2025; originally announced July 2025.

Journal ref: Light Sci Appl 15, 251 (2026)

Muon tracking in a LiquidO opaque scintillator detector

Authors: LiquidO Collaboration, J. Apilluelo, L. Asquith, E. F. Bannister, N. P. Barradas, C. L. Baylis, J. L. Beney, M. Berberan e Santos, X. de la Bernardie, T. J. C. Bezerra, M. Bongrand, C. Bourgeois, D. Breton, J. Busto, A. Cabrera, A. Cadiou, E. Calvo, M. de Carlos Generowicz, E. Chauveau, B. J. Cattermole, M. Chen, P. Chimenti, D. F. Cowen, S. Kr. Das, S. Dusini , et al. (67 additional authors not shown)

Abstract: LiquidO is an innovative radiation detector concept. The core idea is to exploit stochastic light confinement in a highly scattering medium to self-segment the detector volume. In this paper, we demonstrate event-by-event muon tracking in a LiquidO opaque scintillator detector prototype. The detector consists of a 30 mm cubic scintillator volume instrumented with 64 wavelength-shifting fibres arra… ▽ More LiquidO is an innovative radiation detector concept. The core idea is to exploit stochastic light confinement in a highly scattering medium to self-segment the detector volume. In this paper, we demonstrate event-by-event muon tracking in a LiquidO opaque scintillator detector prototype. The detector consists of a 30 mm cubic scintillator volume instrumented with 64 wavelength-shifting fibres arranged in an 8$\times$8 grid with a 3.2 mm pitch and read out by silicon photomultipliers. A wax-based opaque scintillator with a scattering length of approximately 0.5 mm is used. The tracking performance of this LiquidO detector is characterised with cosmic-ray muons and the position resolution is demonstrated to be 450 $μ$m per row of fibres. These results highlight the potential of LiquidO opaque scintillator detectors to achieve fine spatial resolution, enabling precise particle tracking and imaging. △ Less

Submitted 14 January, 2026; v1 submitted 18 July, 2025; originally announced July 2025.

Comments: 20 pages, 7 figures

Journal ref: JINST (2026) 21 P01010

Electric field measurements of Rydberg atomic frequency comb based on pulsed laser excitation

Authors: Ke Di, Chenglin Ye, Yijie Du, Yu Liu, Feng Gao, Jiajia Du, Jun He

Abstract: We present an innovative frequency comb methodology utilizing pulsed lasers for Rydberg atoms and implement it for electric field measurement. It achieves the Rydberg state population of multi-velocity group atoms through the two-photon resonant excitation of a 509 nm pulsed laser and an 852 nm continuous laser. The frequency comb approach markedly elevates the population of Rydberg atoms and augm… ▽ More We present an innovative frequency comb methodology utilizing pulsed lasers for Rydberg atoms and implement it for electric field measurement. It achieves the Rydberg state population of multi-velocity group atoms through the two-photon resonant excitation of a 509 nm pulsed laser and an 852 nm continuous laser. The frequency comb approach markedly elevates the population of Rydberg atoms and augments the atomic density for sensing, thereby enhancing measurement sensitivity. Our investigations generated high-sensitivity measurements of electric fields across a broad spectrum from 20 kHz to 96 MHz, with a minimum measured electric field sensitivity of 2.9uV/cm/Hz(1/2). Additionally, we have exhibited a high degree of measurement sensitivity in the 66 MHz and 88 MHz broadcast communication frequencies. This research enhances the effective detection of microwave signals over a broad spectrum of frequency bands utilizing Rydberg atoms and introduces an innovative technical methodology for microwave metrology grounded in Rydberg atoms. △ Less

Submitted 11 July, 2025; originally announced July 2025.

Thermal Property Microscopy with Compressive Sensing Frequency-Domain Thermoreflectance

Authors: Haobo Yang, Zhenguo Zhu, Zhongnan Xie, Jinhong Du, Shuo Bai, Hong Guo, Te-Huan Liu, Ronggui Yang, Xin Qian

Abstract: Spatial mapping of thermal properties is critical for unveiling the structure-property relation of materials, heterogeneous interfaces, and devices. These property images can also serve as datasets for training artificial intelligence models for material discoveries and optimization. Here we introduce a high-throughput thermal property imaging method called compressive sensing frequency domain the… ▽ More Spatial mapping of thermal properties is critical for unveiling the structure-property relation of materials, heterogeneous interfaces, and devices. These property images can also serve as datasets for training artificial intelligence models for material discoveries and optimization. Here we introduce a high-throughput thermal property imaging method called compressive sensing frequency domain thermoreflectance (CS-FDTR), which can robustly profile thermal property distributions with micrometer resolutions while requiring only a random subset of pixels being experimentally measured. The high-resolution thermal property image is reconstructed from the raw down-sampled data through L_1-regularized minimization. The high-throughput imaging capability of CS-FDTR is validated using the following cases: (a) the thermal conductance of a patterned heterogeneous interface, (b) thermal conductivity variations of an annealed pyrolytic graphite sample, and (c) the sharp change in thermal conductivity across a vertical aluminum/graphite interface. With less than half of the pixels being experimentally sampled, the thermal property images measured using CS-FDTR show nice agreements with the ground truth (point-by-point scanning), with a relative deviation below 15%. This work opens the possibility of high-throughput thermal property imaging without sacrificing the data quality, which is critical for materials discovery and screening. △ Less

Submitted 5 June, 2025; originally announced June 2025.

Journal ref: Physical Review Applied, 24, 014033 (2025)

Flexible Perovskite/Silicon Monolithic Tandem Solar Cells Approaching 30% Efficiency

Authors: Yinqing Sun, Faming Li, Hao Zhang, Wenzhu Liu, Zenghui Wang, Lin Mao, Qian Li, Youlin He, Tian Yang, Xianggang Sun, Yicheng Qian, Yinyi Ma, Liping Zhang, Junlin Du, Jianhua Shi, Guangyuan Wang, Anjun Han, Na Wang, Fanying Meng, Zhengxin Liu, Mingzhen Liu

Abstract: Thanks to their excellent properties of low cost, lightweight, portability, and conformity, flexible perovskite-based tandem solar cells show great potentials for energy harvesting applications, with flexible perovskite/c-silicon tandem solar cells particularly promising for achieving high efficiency. However, performance of flexible perovskite/c-silicon monolithic tandem solar cells still greatly… ▽ More Thanks to their excellent properties of low cost, lightweight, portability, and conformity, flexible perovskite-based tandem solar cells show great potentials for energy harvesting applications, with flexible perovskite/c-silicon tandem solar cells particularly promising for achieving high efficiency. However, performance of flexible perovskite/c-silicon monolithic tandem solar cells still greatly lags, due to challenges in simultaneously achieving both efficient photocarrier transport and reliable mitigation of residual stress. Here, we reveal the critical role of perovskite phase homogeneity, for achieving high-efficient and mechanical-stable flexible perovskite/c-silicon heterojunction monolithic tandem solar cells (PSTs) with textured surface. Through ensuring high phase homogeneity, which promotes charge transfer across all facets of the pyramid on the textured substrates and releases the residual stress at the perovskite/c-silicon interface, we demonstrate flexible PSTs with a bending curvature of 0.44 cm-1, and a certified power conversion efficiency of 29.88% (1.04 cm2 aperture area), surpassing all other types of flexible perovskite-based photovoltaic devices. Our results can lead to broad applications and commercialization of flexible perovskite/c-silicon tandem photovoltaics. △ Less

Submitted 29 April, 2025; originally announced April 2025.

Journal ref: Nature Communications 2025

Strongly confined Mid-infrared to Terahertz Phonon Polaritons in Ultra-thin SrTiO3

Authors: Peiyi He, Jiade Li, Cong Li, Ning Li, Bo Han, Ruochen Shi, Ruishi Qi, Jinlong Du, Pu Yu, Peng Gao

Abstract: Phonon polaritons (PhPs) enable subwavelength light control for infrared sensing, imaging, and optoelectronics, but conventional polar materials have narrow Reststrahlen bands, limiting applications. Materials that support PhPs with broad spectral range, strong field confinement, slow group velocity, and high quality factor are therefore needed. Here, using monochromatic electron energy loss spect… ▽ More Phonon polaritons (PhPs) enable subwavelength light control for infrared sensing, imaging, and optoelectronics, but conventional polar materials have narrow Reststrahlen bands, limiting applications. Materials that support PhPs with broad spectral range, strong field confinement, slow group velocity, and high quality factor are therefore needed. Here, using monochromatic electron energy loss spectroscopy in a scanning transmission electron microscope, we demonstrate that ultra-thin SrTiO3 membranes possess the desired properties. Systematic measurements across varying thicknesses reveal two PhP branches with wide spectral dispersion, strong confinement, and anomalously slow group velocities spanning from the mid-infrared to terahertz range. Notably, in 3-nm-thick membranes, these polaritons exhibit unprecedented confinement factors exceeding 500 and group velocities as low as ~ 7 x 10-5c, rivaling the best-performing van der Waals materials. These findings establish perovskite oxide such as SrTiO3 as versatile platforms for tailoring light-matter interactions at the nanoscale, providing critical insights for the design of next-generation photonic devices requiring broadband operation and enhanced optical confinement. △ Less

Submitted 20 November, 2025; v1 submitted 12 April, 2025; originally announced April 2025.

Journal ref: Peiyi He et al. ,Strongly confined mid-infrared to terahertz phonon polaritons in ultrathin SrTiO3.Sci. Adv.11,eady7316(2025)

An empirical formulation of accelerated molecular dynamics for simulating and predicting microstructure evolution in materials

Authors: Liang Wan, Qingsong Mei, Haowen Liu, Huafeng Zhang, Jun-Ping Du, Shigenobu Ogata, Wen Tong Geng

Abstract: Despite its widespread use in materials science, conventional molecular dynamics (MD) simulations are severely constrained by timescale limitations. To address this shortcoming, we propose an empirical formulation of accelerated MD method, adapted from a collective-variable-based extended system dynamics framework. While this framework is originally developed for efficient free energy sampling and… ▽ More Despite its widespread use in materials science, conventional molecular dynamics (MD) simulations are severely constrained by timescale limitations. To address this shortcoming, we propose an empirical formulation of accelerated MD method, adapted from a collective-variable-based extended system dynamics framework. While this framework is originally developed for efficient free energy sampling and reaction pathway determination of specific rare events in condensed matter, we have modified it to enable accelerated MD simulation and prediction of microstructure evolution of materials across a broad range of scenarios. In essence, the nearest neighbor off-centering absolute displacement (NNOAD), which quantifies the deviation of an atom from the geometric center of its nearest neighbors in materials, is introduced. We propose that the collection of NNOADs of all atoms can serve as a generalized reaction coordinate for various structural transitions in materials. The NNOAD of each atom, represented by its three components, is coupled with three additional dynamic variables assigned to the atom. Time evolution of the additional dynamic variables follows Langevin equation, while Nosé-Hoover dynamics is employed to thermostat the system. Through careful analysis and benchmark simulations, we established appropriate parameter ranges for the equations in our method. Application of this method to several test cases demonstrates its capability to accelerate MD simulations by several orders of magnitude while maintaining kinetic consistency and good accuracy in predicting long timescale microstructure evolutions of materials. We also provide some preliminary thoughts on theoretical justification of the method, offering insights into its underlying principles. △ Less

Submitted 9 December, 2025; v1 submitted 18 March, 2025; originally announced March 2025.

Comments: 41 pages, 18 figures with 8 supplementary movies

The Stochastic Light Confinement of LiquidO

Authors: LiquidO Collaboration, J. Apilluelo, L. Asquith, E. F. Bannister, N. P. Barradas, J. L. Beney, M. Berberan e Santos, X. de la Bernardie, T. J. C. Bezerra, M. Bongrand, C. Bourgeois, D. Breton, C. Buck, J. Busto, K. Burns, A. Cabrera, A. Cadiou, E. Calvo, E. Chauveau, B. J. Cattermole, M. Chen, P. Chimenti, D. F. Cowen, S. Dusini, A. Earle , et al. (72 additional authors not shown)

Abstract: Light-based detectors have been widely used in fundamental research and industry since their inception in the 1930s. The energy particles deposit in these detectors is converted to optical signals via the Cherenkov and scintillation mechanisms that are then propagated through transparent media to photosensors placed typically on the detector's periphery, sometimes up to tens of metres away. Liquid… ▽ More Light-based detectors have been widely used in fundamental research and industry since their inception in the 1930s. The energy particles deposit in these detectors is converted to optical signals via the Cherenkov and scintillation mechanisms that are then propagated through transparent media to photosensors placed typically on the detector's periphery, sometimes up to tens of metres away. LiquidO is a new technique pioneering the use of opaque media to stochastically confine light around each energy deposition while collecting it with an array of fibres that thread the medium. This approach preserves topological event information otherwise lost in the conventional approach, enabling real-time imaging down to the MeV scale. Our article demonstrates LiquidO's imaging principle with a ten-litre prototype, revealing successful light confinement of 90% of the detected light within a 5 cm radius sphere, using a custom opaque scintillator with a scattering length on the order of a few millimetres. These high-resolution imaging capabilities unlock opportunities in fundamental physics research and applications beyond. The absolute amount of light detected is also studied, including possible data-driven extrapolations to LiquidO-based detectors beyond prototyping limitations. Additionally, LiquidO's timing capabilities are explored through its ability to distinguish Cherenkov light from a slow scintillator. △ Less

Submitted 12 March, 2025; v1 submitted 4 March, 2025; originally announced March 2025.

Comments: 22 pages, 9 figures, 2 tables

COCOA: a compact Compton camera for astrophysical observation of MeV-scale gamma rays

Authors: LiquidO Collaboration, S. R. Soleti, J. J. Gómez-Cadenas, J. Apilluelo, L. Asquith, E. F. Bannister, N. P. Barradas, C. L. Baylis, J. L. Beney, M. Berberan e Santos, X. de la Bernardie, T. J. C. Bezerra, M. Bongrand, C. Bourgeois, D. Breton, J. Busto, K. Burns, A. Cabrera, A. Cadiou, E. Calvo, M. de Carlos Generowicz, E. Chauveau, B. J. Cattermole, M. Chen, P. Chimenti , et al. (67 additional authors not shown)

Abstract: COCOA (COmpact COmpton cAmera) is a next-generation gamma-ray telescope designed for astrophysical observations in the MeV energy range. The detector comprises a scatterer volume employing the LiquidO detection technology and an array of scintillating crystals acting as absorber. Surrounding plastic scintillator panels serve as a veto system for charged particles. The detector's compact, scalable… ▽ More COCOA (COmpact COmpton cAmera) is a next-generation gamma-ray telescope designed for astrophysical observations in the MeV energy range. The detector comprises a scatterer volume employing the LiquidO detection technology and an array of scintillating crystals acting as absorber. Surrounding plastic scintillator panels serve as a veto system for charged particles. The detector's compact, scalable design enables flexible deployment on microsatellites or high-altitude balloons. Gamma rays at MeV energies have not been well explored historically (the so-called "MeV gap") and COCOA has the potential to improve the sensitivity in this energy band. △ Less

Submitted 12 May, 2025; v1 submitted 28 February, 2025; originally announced February 2025.

Comments: 14 pages, 17 figures

Journal ref: Astropart. Phys. 172 (2025) 103135

PaMMA-Net: Plasmas magnetic measurement evolution based on data-driven incremental accumulative prediction

Authors: Yunfei Ling, Zijie Liu, Jun Du, Yao Huang, Yuehang Wang, Bingjia Xiao, Xin Fang

Abstract: An accurate evolution model is crucial for effective control and in-depth study of fusion plasmas. Evolution methods based on physical models often encounter challenges such as insufficient robustness or excessive computational costs. Given the proven strong fitting capabilities of deep learning methods across various fields, including plasma research, this paper introduces a deep learning-based m… ▽ More An accurate evolution model is crucial for effective control and in-depth study of fusion plasmas. Evolution methods based on physical models often encounter challenges such as insufficient robustness or excessive computational costs. Given the proven strong fitting capabilities of deep learning methods across various fields, including plasma research, this paper introduces a deep learning-based magnetic measurement evolution method named PaMMA-Net (Plasma Magnetic Measurements Incremental Accumulative Prediction Network). This network is capable of evolving magnetic measurements in tokamak discharge experiments over extended periods or, in conjunction with equilibrium reconstruction algorithms, evolving macroscopic parameters such as plasma shape. Leveraging a incremental prediction approach and data augmentation techniques tailored for magnetic measurements, PaMMA-Net achieves superior evolution results compared to existing studies. The tests conducted on real experimental data from EAST validate the high generalization capability of the proposed method. △ Less

Submitted 23 January, 2025; originally announced January 2025.

Comments: 20 pages, 8 figures

Single-molecule Scale Magnetic Resonance Spectroscopy using Nitrogen-Vacancy Centers in Diamond

Authors: Jiangfeng Du, Fazhan Shi, Xi Kong, Fedor Jekezko, Jörg Wrachtrup

Abstract: Single-molecule technology stands as a powerful tool, enabling the characterization of intricate structural and dynamic information that would otherwise remain concealed within the averaged behaviors of numerous molecules. This technology finds extensive application across diverse fields including physics, chemistry, biology, and medicine. Quantum sensing, particularly leveraging nitrogen-vacancy… ▽ More Single-molecule technology stands as a powerful tool, enabling the characterization of intricate structural and dynamic information that would otherwise remain concealed within the averaged behaviors of numerous molecules. This technology finds extensive application across diverse fields including physics, chemistry, biology, and medicine. Quantum sensing, particularly leveraging nitrogen-vacancy (NV) centers within diamond structures, presents a promising avenue for single-molecule magnetic resonance, offering prospects for sensing and imaging technology at the single-molecule level. Notably, while significant strides have been made in single-molecule scale magnetic resonance using NV centers over the past two decades, current approaches still exhibit limitations in magnetic sensitivity, spectral resolution, and spatial resolution. Particularly, the full reconstruction of three-dimensional positions of nuclear spins within single molecules remains an unattained goal. This review provides a comprehensive overview of the current state-of-the-art in single-molecule scale magnetic resonance, encompassing an analysis of various relevant techniques involving NV centers. Additionally, it explores the optimization of technical parameters associated with these methods. This detailed analysis serves as a foundation for the development of new technologies and the exploration of potential applications. △ Less

Submitted 7 January, 2025; originally announced January 2025.

Comments: 68 pages, 46 figures, 7 figures

Journal ref: Rev. Mod. Phys. 96, 025001 (2024)

Searches for exotic spin-dependent interactions with spin sensors

Authors: Min Jiang, Haowen Su, Yifan Chen, Man Jiao, Ying Huang, Yuanhong Wang, Xing Rong, Xinhua Peng, Jiangfeng Du

Abstract: Numerous theories have postulated the existence of exotic spin-dependent interactions beyond the Standard Model of particle physics. Spin-based quantum sensors, which utilize the quantum properties of spins to enhance measurement precision, emerge as powerful tools for probing these exotic interactions. These sensors encompass a wide range of technologies, such as optically pumped magnetometers, a… ▽ More Numerous theories have postulated the existence of exotic spin-dependent interactions beyond the Standard Model of particle physics. Spin-based quantum sensors, which utilize the quantum properties of spins to enhance measurement precision, emerge as powerful tools for probing these exotic interactions. These sensors encompass a wide range of technologies, such as optically pumped magnetometers, atomic comagnetometers, spin masers, nuclear magnetic resonance, spin amplifiers, and nitrogen-vacancy centers. These technologies stand out for their ultrahigh sensitivity, compact tabletop design, and cost-effectiveness, offering complementary approaches to the large-scale particle colliders and astrophysical observations. This article reviews the underlying physical principles of various spin sensors and highlights the recent theoretical and experimental progress in the searches for exotic spin-dependent interactions with these quantum sensors. Investigations covered include the exotic interactions of spins with ultralight dark matter, exotic spin-dependent forces, electric dipole moment, spin-gravity interactions, and among others. Ongoing and forthcoming experiments using advanced spin-based sensors to investigate exotic spin-dependent interactions are discussed. △ Less

Submitted 5 December, 2024; v1 submitted 4 December, 2024; originally announced December 2024.

Comments: 32 pages, 13 figures, accepted for publication in Reports on Progress in Physics

Journal ref: Rep. Prog. Phys. 88 (2025) 016401

Multi-focal Picosecond laser vertical slicing of 6 inch 4H-SiC ingot

Authors: Jiabao Du, Shusen Zhao, Xiaoyu Lu, Lu Jiang, Shifei Han, Xinyao Li, Xuechun Lin

Abstract: Ultrafast laser direct writing inside materials has garnered significant attention for its applications in techniques like two-photon polymerization, stealth dicing and vertical slicing. 4H-Silicon Carbide (4H-SiC) vertical slicing has wide potentials from research to industry due to low kerf loss and high slicing speed. In this paper, to improve the vertical slicing processing quality and lower t… ▽ More Ultrafast laser direct writing inside materials has garnered significant attention for its applications in techniques like two-photon polymerization, stealth dicing and vertical slicing. 4H-Silicon Carbide (4H-SiC) vertical slicing has wide potentials from research to industry due to low kerf loss and high slicing speed. In this paper, to improve the vertical slicing processing quality and lower the separation strength, we introduce a multi-focal vertical slicing method with spherical aberrations caused by refractive index eliminated. Additionally, by shaping the wavefront of picosecond laser, our experiments show the lower latitudinal ablation zone and higher crack propagation of multi-focal vertical slicing method on 4H-SiC, demonstrating that this method not only reduces filamentations to minimize ablation damage, but also significantly reduce the tensile strength during separation. We achieve a 6 inch 4H-SiC ingot vertical slicing and separation using 4-focal slicing. This method shows various potentials in laser processing. △ Less

Submitted 27 November, 2024; originally announced November 2024.

Adaptive Mesh Refinement for Two-Phase Viscoelastic Fluid Mixture Models

Authors: Bindi M. Nagda, Aaron Barrett, Boyce E. Griffith, Aaron L. Fogelson, Jian Du

Abstract: Multiphase flows are an important class of fluid flow and their study facilitates the development of diverse applications in industrial, natural, and biomedical systems. We consider a model that uses a continuum description of both phases in which separate momentum equations are used for each phase along with a co-incompressibility condition on the velocity fields. The resulting system of equation… ▽ More Multiphase flows are an important class of fluid flow and their study facilitates the development of diverse applications in industrial, natural, and biomedical systems. We consider a model that uses a continuum description of both phases in which separate momentum equations are used for each phase along with a co-incompressibility condition on the velocity fields. The resulting system of equations poses numerical challenges due to the presence of multiple non-linear terms and the co-incompressibility condition, and the resulting fluid dynamics motivate the development of an adaptive mesh refinement (AMR) technique to accurately capture regions of high stresses and large material gradients while keeping computational costs low. We present an accurate, robust, and efficient computational method for simulating multiphase mixtures on adaptive grids, and utilize a multigrid solver to precondition the saddle-point system. We demonstrate that the AMR discretization asymptotically approaches second order accuracy in $L^1$, $L^2$ and $L^\infty$ norms. The solver can accurately resolve sharp gradients in the solution and, with the multigrid preconditioning strategy introduced herein, the linear solver iterations are independent of grid spacing. Our AMR solver offers a major cost savings benefit, providing up to ten fold speedup over a uniform grid in the numerical experiments presented here, with greater speedup possible depending on the problem set-up. △ Less

Submitted 1 August, 2025; v1 submitted 30 September, 2024; originally announced September 2024.

MSC Class: 76-10; 76T06 ACM Class: G.1.8; G.4

Waveguide Superlattices with Artificial Gauge Field Towards Colorless and Crosstalkless Ultrahigh-Density Photonic Integration

Authors: Xuelin Zhang, Jiangbing Du, Ke Xu, Zuyuan He

Abstract: Dense waveguides are the basic building blocks for photonic integrated circuits (PIC). Due to the rapidly increasing scale of PIC chips, high-density integration of waveguide arrays working with low crosstalk over broadband wavelength range is highly desired. However, the sub-wavelength regime of such structures has not been adequately explored in practice. Herein, we proposed a waveguide superlat… ▽ More Dense waveguides are the basic building blocks for photonic integrated circuits (PIC). Due to the rapidly increasing scale of PIC chips, high-density integration of waveguide arrays working with low crosstalk over broadband wavelength range is highly desired. However, the sub-wavelength regime of such structures has not been adequately explored in practice. Herein, we proposed a waveguide superlattice design leveraging the artificial gauge field (AGF) mechanism, corresponding to the quantum analog of field-induced n-photon resonances in semiconductor superlattices. This approach experimentally achieves -24 dB crosstalk suppression with an ultra-broad transmission bandwidth over 500 nm for dual polarizations. The fabricated waveguide superlattices support high-speed signal transmission of 112 Gbit/s with high-fidelity signal-to-noise ratio profiles and bit error rates. This design, featuring a silica upper cladding, is compatible with standard metal back end-of-the-line (BEOL) processes. Based on such a fundamental structure that can be readily transferred to other platforms, passive and active devices over versatile platforms can be realized with a significantly shrunk on-chip footprint, thus it holds great promise for significant reduction of the power consumption and cost in PICs. △ Less

Submitted 30 July, 2024; v1 submitted 10 July, 2024; originally announced July 2024.

Out-of-Plane Polarization from Spin Reflection Induces Field-Free Spin-Orbit Torque Switching in Structures with Canted NiO Interfacial Moments

Authors: Zhe Zhang, Zhuoyi Li, Yuzhe Chen, Fangyuan Zhu, Yu Yan, Yao Li, Liang He, Jun Du, Rong Zhang, Jing Wu, Xianyang Lu, Yongbing Xu

Abstract: Realizing deterministic current-induced spin-orbit torque (SOT) magnetization switching, especially in systems exhibiting perpendicular magnetic anisotropy (PMA), typically requires the application of a collinear in-plane field, posing a challenging problem. In this study, we successfully achieve field-free SOT switching in the CoFeB/MgO system. In a Ta/CoFeB/MgO/NiO/Ta structure, spin reflection… ▽ More Realizing deterministic current-induced spin-orbit torque (SOT) magnetization switching, especially in systems exhibiting perpendicular magnetic anisotropy (PMA), typically requires the application of a collinear in-plane field, posing a challenging problem. In this study, we successfully achieve field-free SOT switching in the CoFeB/MgO system. In a Ta/CoFeB/MgO/NiO/Ta structure, spin reflection at the NiO interface, characterized by noncollinear spin structures with canted magnetization, generates a spin current with an out-of-plane spin polarization σz. We confirm the contribution of σz to the field-free SOT switching through measurements of the shift effect in the out-of-plane magnetization hysteresis loops under different currents. The incorporation of NiO as an antiferromagnetic insulator, mitigates the current shunting effect and ensures excellent thermal stability of the device. The sample with 0.8 nm MgO and 2 nm NiO demonstrates an impressive optimal switching ratio approaching 100% without an in-plane field. This breakthrough in the CoFeB/MgO system promises significant applications in spintronics, advancing us closer to realizing innovative technologies. △ Less

Submitted 4 July, 2024; originally announced July 2024.

Molecular-Resolution Imaging of Ice Crystallized from Liquid Water

Authors: Jingshan S. Du, Suvo Banik, Henry Chan, Birk Fritsch, Ying Xia, Ajay S. Karakoti, Andreas Hutzler, Subramanian K. R. S. Sankaranarayanan, James J. De Yoreo

Abstract: Despite the ubiquity of ice, a molecular-resolution image of ice crystallized from liquid water or the resulting defect structure has never been obtained. Here, we report the stabilization and angstrom-resolution electron imaging of ice Ih crystallized from liquid water by developing cryogenic liquid-cell transmission electron microscopy (CRYOLIC-TEM). We combine lattice mapping with molecular dyn… ▽ More Despite the ubiquity of ice, a molecular-resolution image of ice crystallized from liquid water or the resulting defect structure has never been obtained. Here, we report the stabilization and angstrom-resolution electron imaging of ice Ih crystallized from liquid water by developing cryogenic liquid-cell transmission electron microscopy (CRYOLIC-TEM). We combine lattice mapping with molecular dynamics simulations to reveal that ice formation is highly tolerant to nanoscale defects such as misoriented subdomains and trapped gas bubbles, which are stabilized by molecular-scale structural motifs. Importantly, bubble surfaces adopt low-energy nanofacets and create negligible strain fields in the surrounding crystal. These bubbles can dynamically nucleate, grow, migrate, dissolve, and coalesce under electron irradiation and be monitored in situ near a steady state. This work opens the door to understanding water crystallization behaviors at an unprecedented spatial resolution. △ Less

Submitted 26 November, 2024; v1 submitted 2 June, 2024; originally announced June 2024.

Comments: 26 pages, 5 figures, and 1 table. Supplementary Information: 35 pages, 37 figures, and 9 tables

Journal ref: Nature Communications 2025, 16, 8342

Challenging theories of dark energy with levitated force sensor

Authors: Peiran Yin, Rui Li, Chengjiang Yin, Xiangyu Xu, Xiang Bian, Han Xie, Chang-Kui Duan, Pu Huang, Jian-hua He, Jiangfeng Du

Abstract: The nature of dark energy is one of the most outstanding problems in physical science, and various theories have been proposed. It is therefore essential to directly verify or rule out these theories experimentally. However, despite substantial efforts in astrophysical observations and laboratory experiments, previous tests have not yet acquired enough accuracy to provide decisive conclusions as t… ▽ More The nature of dark energy is one of the most outstanding problems in physical science, and various theories have been proposed. It is therefore essential to directly verify or rule out these theories experimentally. However, despite substantial efforts in astrophysical observations and laboratory experiments, previous tests have not yet acquired enough accuracy to provide decisive conclusions as to the validity of these theories. Here, using a diamagnetically levitated force sensor, we carry out a test on one of the most compelling explanations for dark energy to date, namely the Chameleon theory, an ultra-light scalar field with screening mechanisms, which couples to normal-matter fields and leaves a detectable fifth force. Our results extend previous results by nearly two orders of magnitude to the entire physical plausible parameter space of cosmologically viable chameleon models. We find no evidence for such a fifth force. Our results decisively rule out the basic chameleon model as a candidate for dark energy. Our work, thus, demonstrates the robustness of laboratory experiments in unveiling the nature of dark energy in the future. The methodology developed here can be further applied to study a broad range of fundamental physics. △ Less

Submitted 15 May, 2024; originally announced May 2024.

Journal ref: Nature Physics 18, 1181-1185 (2022)

Near-Quantum-limited Haloscope Detection of Dark Photon Dark Matter Enhanced by a High-Q Superconducting Cavit

Authors: Runqi Kang, Man Jiao, Yu Tong, Yang Liu, Youpeng Zhong, Yi-Fu Cai, Jingwei Zhou, Xing Rong, Jiangfeng Du

Abstract: We report new experimental results on the search for dark photons based on a near-quantum-limited haloscope equipped with a superconducting cavity. The loaded quality factor of the superconducting cavity is $6\times10^{5}$, so that the expected signal from dark photon dark matter can be enhanced by more than one order compared to a copper cavity. A Josephson parametric amplifier with a near-quantu… ▽ More We report new experimental results on the search for dark photons based on a near-quantum-limited haloscope equipped with a superconducting cavity. The loaded quality factor of the superconducting cavity is $6\times10^{5}$, so that the expected signal from dark photon dark matter can be enhanced by more than one order compared to a copper cavity. A Josephson parametric amplifier with a near-quantum-limited noise temperature has been utilized to minimize the noise during the search. Furthermore, a digital acquisition card based on field programmable gate arrays has been utilized to maximize data collection efficiency with a duty cycle being 100$\%$. This work has established the most stringent constraints on dark photons at around 26.965 $μ$eV. In the future, our apparatus can be extended to search for other dark matter candidates, such as axions and axion-like particles, and scrutinize new physics beyond the Standard Model. △ Less

Submitted 19 April, 2024; originally announced April 2024.

Imaging a chain of strongly correlated Rydberg excitations enabled by Förster-resonance-enhanced interaction

Authors: Jinjin Du, Thibault Vogt, Ningxuan Zheng, Wenhui Li

Abstract: Rydberg atoms are currently a very fast advancing quantum platform. For many interesting and demanding applications, including quantum computation, fast detection of a Rydberg excitation or a Rydberg qubit for information readout would be one of the most desirable developments. We demonstrate single-shot and \textit{in situ} absorption imaging of individual Rydberg excitations. This level of resol… ▽ More Rydberg atoms are currently a very fast advancing quantum platform. For many interesting and demanding applications, including quantum computation, fast detection of a Rydberg excitation or a Rydberg qubit for information readout would be one of the most desirable developments. We demonstrate single-shot and \textit{in situ} absorption imaging of individual Rydberg excitations. This level of resolution is achieved using an electromagnetically induced transparency scheme involving a Rydberg energy level that is highly sensitive to the presence of Rydberg atoms due to Förster-resonance-enhanced dipole couplings. Spectroscopic measurements illustrate the existence of the Förster resonance and underscore the state-selectivity of the technique. With an imaging exposure time as short as 3 $μ$s, we successfully resolve linear chains of Rydberg excitations in a one-dimensional configuration. The extracted second-order correlation shows strong anti-bunching due to excitation blockade, and a Fourier analysis reveals the long-range order in the chains of Rydberg excitations. This imaging technique, with minimal destruction, will be of great interest for leveraging ensemble-encoded qubits in quantum computation and quantum simulation applications. △ Less

Submitted 29 September, 2025; v1 submitted 30 March, 2024; originally announced April 2024.

Comments: 10 pages, 5 figures

Journal ref: Optica 12(8), 1213 (2025)

Measurement of the earth tides with a diamagnetic-levitated micro-oscillator at room temperature

Authors: Yingchun Leng, Yiming Chen, Rui Li, Lihua Wang, Hao Wang, Lei Wang, Han Xie, Chang-Kui Duan, Pu Huang, Jiangfeng Du

Abstract: The precise measurement of the gravity of the earth plays a pivotal role in various fundamental research and application fields. Although a few gravimeters have been reported to achieve this goal, miniaturization of high-precision gravimetry remains a challenge. In this work, we have proposed and demonstrated a miniaturized gravimetry operating at room temperature based on a diamagnetic levitated… ▽ More The precise measurement of the gravity of the earth plays a pivotal role in various fundamental research and application fields. Although a few gravimeters have been reported to achieve this goal, miniaturization of high-precision gravimetry remains a challenge. In this work, we have proposed and demonstrated a miniaturized gravimetry operating at room temperature based on a diamagnetic levitated micro-oscillator with a proof mass of only 215 mg. Compared with the latest reported miniaturized gravimeters based on Micro-Electro-Mechanical Systems, the performance of our gravimetry has substantial improvements in that an acceleration sensitivity of 15 $μGal/\sqrt{Hz}$ and a drift as low as 61 $μGal$ per day have been reached. Based on this diamagnetic levitation gravimetry, we observed the earth tides, and the correlation coefficient between the experimental data and theoretical data reached 0.97. Some moderate foreseeable improvements can develop this diamagnetic levitation gravimetry into chip size device, making it suitable for mobile platforms such as drones. Our advancement in gravimetry is expected to facilitate a multitude of applications, including underground density surveying and the forecasting of natural hazards. △ Less

Submitted 23 March, 2024; originally announced March 2024.

Comments: 5 pages, 3 figures

Journal ref: Phys. Rev. Lett. 132, 123601 (2024)

Broadband squeezed light field by magnetostriction in an opto-magnomechanical

Authors: Ke Di, Shuai Tan, Anyu Cheng, Yinxue Zhao, Yu Liu, Jiajia Du

Abstract: We present a novel mechanism for generating a wide bandwidth squeezed optical output field in an opto-magnomechanical system. In this system, the magnon (mechanical) mode in the yttrium-iron-garnet crystal is coupled to the microwave field (optical field) through magnetic dipole (radiation pressure) interaction. The magnetostrictive force induced by the yttrium-iron-garnet crystal causes a mechani… ▽ More We present a novel mechanism for generating a wide bandwidth squeezed optical output field in an opto-magnomechanical system. In this system, the magnon (mechanical) mode in the yttrium-iron-garnet crystal is coupled to the microwave field (optical field) through magnetic dipole (radiation pressure) interaction. The magnetostrictive force induced by the yttrium-iron-garnet crystal causes a mechanical displacement and creates a quadrature squeezed magnon mode. Eventually, this quadrature squeezed mechanical mode is transferred to the output optical field through state-swap interaction. Our results demonstrate the optimal parameter range for obtaining a stable squeezed optical output field with a wide bandwidth. Moreover, the squeezed light field exhibits strong robustness to environmental temperature. The new scheme we propose has potential applications in quantum precision measurements, quantum wireless networks, quantum radar, etc. △ Less

Submitted 7 February, 2024; originally announced February 2024.

Liquid-State Semiconductor Lasers Based on Type-(I+II) Colloidal Quantum Dots

Authors: Donghyo Hahm, Valerio Pinchetti, Clément Livache, Namyoung Ahn, Jungchul Noh, Xueyang Li, Jun Du, Kaifeng Wu, Victor I. Klimov

Abstract: Present-day liquid-state lasers are based on organic dyes. Here we demonstrate an alternative class of liquid lasers that employ solutions of colloidal quantum dots (QDs). Previous efforts to realize such devices have been hampered by fast nonradiative Auger recombination of multi-carrier states needed for optical gain. We overcome this challenge using type-(I+II) QDs that feature a trion-like opt… ▽ More Present-day liquid-state lasers are based on organic dyes. Here we demonstrate an alternative class of liquid lasers that employ solutions of colloidal quantum dots (QDs). Previous efforts to realize such devices have been hampered by fast nonradiative Auger recombination of multi-carrier states needed for optical gain. We overcome this challenge using type-(I+II) QDs that feature a trion-like optical-gain state with strongly suppressed Auger recombination. When combined with a Littrow optical cavity, static (non-circulated) solutions of these QDs exhibit stable lasing tunable from 634 nm to 594 nm. These results point towards the feasibility of technologically viable dye-like QD lasers that feature wide spectral tunability and, importantly, allow for stable operation without the need for a bulky circulation system, a standard attribute of traditional dye lasers. △ Less

Submitted 16 January, 2024; originally announced January 2024.

Comments: Main text (29 pages, 4 Figs) + Supplementary Info (15 pages, 10 Figures)

Report number: LA-UR-23-33109

Demonstration of a low loss, highly stable and re-useable edge coupler for high heralding efficiency and low g^(2) (0) SOI correlated photon pair sources

Authors: Jinyi Du, George F. R. Chen, Hongwei Gao, James A. Grieve, Dawn T. H. Tan, Alexander Ling

Abstract: We report a stable, low loss method for coupling light from silicon-on-insulator (SOI) photonic chips into optical fibers. The technique is realized using an on-chip tapered waveguide and a cleaved small core optical fiber. The on-chip taper is monolithic and does not require a patterned cladding, thus simplifying the chip fabrication process. The optical fiber segment is composed of a centimeter-… ▽ More We report a stable, low loss method for coupling light from silicon-on-insulator (SOI) photonic chips into optical fibers. The technique is realized using an on-chip tapered waveguide and a cleaved small core optical fiber. The on-chip taper is monolithic and does not require a patterned cladding, thus simplifying the chip fabrication process. The optical fiber segment is composed of a centimeter-long small core fiber (UHNA7) which is spliced to SMF-28 fiber with less than -0.1 dB loss. We observe an overall coupling loss of -0.64 dB with this design. The chip edge and fiber tip can be butt coupled without damaging the on-chip taper or fiber. Friction between the surfaces maintains alignment leading to an observation of +-0.1 dB coupling fluctuation during a ten-day continuous measurement without use of any adhesive. This technique minimizes the potential for generating Raman noise in the fiber, and has good stability compared to coupling strategies based on longer UHNA fibers or fragile lensed fibers. We also applied the edge coupler on a correlated photon pair source and observed a raw coincidence count rate of 1.21 million cps and raw heralding efficiency of 21.3%. We achieved an auto correlation function g^(2) (0) as low as 0.0004 at the low pump power regime. △ Less

Submitted 14 March, 2024; v1 submitted 28 December, 2023; originally announced December 2023.

Journal ref: "Demonstration of a low loss, highly stable and re-useable edge coupler for high heralding efficiency and low g(2)(0) SOI correlated photon pair sources," Opt. Express 32, 11406-11418 (2024)

Dynamically tunable electromagnetically induced transparency-like metamaterial structure based on polarization sensitivity

Authors: Ke Di, Meng Xie, Zhaoyang Wang, Renpu Li, Yu Liu, Jiajia Du

Abstract: In this paper, we propose a plasmon-induced transparency (PIT) metamaterial structure composed of Ag nanomaterials with polarization sensitivity. The metamaterial model consists of three bright modes with different resonant frequencies. The optical properties of the structure are further investigated using finite difference time domain (FDTD) method. The results show that the conversion between si… ▽ More In this paper, we propose a plasmon-induced transparency (PIT) metamaterial structure composed of Ag nanomaterials with polarization sensitivity. The metamaterial model consists of three bright modes with different resonant frequencies. The optical properties of the structure are further investigated using finite difference time domain (FDTD) method. The results show that the conversion between single-band PIT and dual-band PIT effects can be achieved by changing the polarization degree of the incident light, the number of transparent windows can be changed from one to two, and the process is accompanied by the conversion of bright and dark modes and the change of the resonance wavelength of the transmission peak. In addition, When the light is polarized in the Y-direction, the two transparency windows have different refractive index sensitivities, with FOM values of 5.94/RIU and 5.65/RIU, respectively. △ Less

Submitted 19 December, 2023; originally announced December 2023.

Macroscopic entanglement between ferrimagnetic magnons and atoms via crossed optical cavity

Authors: Ke Di, Xi Wang, Huarong Xia, Yinxue Zhao, Anyu Cheng, Yu Liu, Jiajia Du

Abstract: We consider a two-dimensional opto-magnomechanical (OMM) system including two optical cavity modes, a magnon mode, a phonon mode, and a collection of two-level atoms. In this study, we demonstrate the methodology for generating stationary entanglement between two-level atoms and magnons, which are implemented using two optical cavities inside the setup. Additionally, we investigate the efficiency… ▽ More We consider a two-dimensional opto-magnomechanical (OMM) system including two optical cavity modes, a magnon mode, a phonon mode, and a collection of two-level atoms. In this study, we demonstrate the methodology for generating stationary entanglement between two-level atoms and magnons, which are implemented using two optical cavities inside the setup. Additionally, we investigate the efficiency of transforming entanglement from atom-phonon entanglement to atom-magnon entanglement. The magnons are stimulated by both a bias magnetic field and a microwave magnetic field, and they interact with phonons through the mechanism of magnetostrictive interaction. This interaction generates magnomechanical displacement, which couples to an optical cavity via radiation pressure. We demonstrate that by carefully selecting the frequency detuning of an optical cavity, it is possible to achieve an increase in bipartite entanglements. Furthermore, this improvement is found to be resistant to changes in temperature. The entanglement between atoms and magnons plays a crucial role in the construction of hybrid quantum networks. Our modeling approach exhibits potential applications in the field of magneto-optical trap systems as well. △ Less

Submitted 19 December, 2023; originally announced December 2023.

Comments: arXiv admin note: text overlap with arXiv:1903.00221 by other authors

Dispersion and damping of ion-acoustic waves in the plasma with a regularized kappa-distribution

Authors: Rui Huo, Jiulin Du

Abstract: The dispersion and damping of ion-acoustic waves in the plasma with a regularized kappa-distribution are studied. The generalized dispersion relation and damping rate are derived, which both depend significantly on the parameters alpha and kappa. The numerical analyses show that the wave frequency and the damping rate of ion-acoustic waves in the plasma with the regularized kappa-distribution are… ▽ More The dispersion and damping of ion-acoustic waves in the plasma with a regularized kappa-distribution are studied. The generalized dispersion relation and damping rate are derived, which both depend significantly on the parameters alpha and kappa. The numerical analyses show that the wave frequency and the damping rate of ion-acoustic waves in the plasma with the regularized kappa-distribution are both generally less than those in the plasma with the kappa-distribution, and if kappa is less than a value, the ion-acoustic waves and their damping rate exist in the plasma with the regularized kappa-distribution. △ Less

Submitted 27 September, 2023; originally announced September 2023.

Comments: 10 pages, 4 figures, 22 references

Journal ref: IEEE Transactions on Plasma 51 (2023) 2383-2387

Slowing down of charged particles in the dusty plasmas with a non-thermal velocity alpha-distribution

Authors: Yu Wang, Jiulin Du

Abstract: The slowing down of a charged particle beam passing through the dusty plasma with a non-thermal velocity alpha-distribution is studied. By using the Fokker-Planck collision theory, we derive the deceleration factor and slowing down time and make the numerical analyses. We show that the non-thermal velocity alpha-distributions of the plasma components have a significant effect on the slowing down.… ▽ More The slowing down of a charged particle beam passing through the dusty plasma with a non-thermal velocity alpha-distribution is studied. By using the Fokker-Planck collision theory, we derive the deceleration factor and slowing down time and make the numerical analyses. We show that the non-thermal velocity alpha-distributions of the plasma components have a significant effect on the slowing down. With increase of the mean velocity, the deceleration factor increases rapidly, reaches a peak and then decreases gradually. And the entire peak of the deceleration factor moves generally to the right with the increase of the alpha-parameter. The slowing down time decreases with the increase of the non-thermal alpha-parameter, and so the slowing down time in the non-thermal dusty plasma is generally less than that in a Maxwellian one. △ Less

Submitted 27 September, 2023; originally announced September 2023.

Comments: 8 pages, 4 figures, 25 references

Journal ref: Contribution to Plasma Physics 63 (2023) e202300037