Atmospheric and Oceanic Physics
The Complete Anatomy of the Madden-Julian Oscillation Revealed by Artificial Intelligence
Xiao Zhou, Yuze Sun, Jie Wu et al. (+1 more)
Accurately defining the life cycle of the Madden-Julian Oscillation (MJO), the dominant mode of intraseasonal
climate variability, remains a foundational challenge due to its propagating nature. The established linear-projection method (RMM index) often conflates mathematical artifacts with physical states, while direct clustering in raw data space is confounded by a "propagation penalty." Here, we introduce an "AI-for-theory" paradigm to objectively discover the MJO's intrinsic structure. We develop a deep learning model, PhysAnchor-MJO-AE, to learn a latent representation where vector distance corresponds to physical-feature similarity, enabling objective clustering of MJO dynamical states. Clustering these "MJO fingerprints" reveals the first complete, six-phase anatomical map of its life cycle. This taxonomy refines and critically completes the classical view by objectively isolating two long-hypothesized transitional phases: organizational growth over the Indian Ocean and the northward shift over the Philippine Sea. Derived from this anatomy, we construct a new physics-coherent monitoring framework that decouples location and intensity diagnostics. This framework reduces the rates of spurious propagation and convective misplacement by over an order of magnitude compared to the classical index. Our work transforms AI from a
forecasting tool into a discovery microscope, establishing a reproducible template for extracting fundamental dynamical constructs from complex systems.
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All authors Xiao Zhou, Yuze Sun, Jie Wu, Xiaomeng Huang
Chemical Physics
Singlet Fission among two Single Molecules
Sumanta Paul, Oleksandr Yampolskyy, Zehua Wu et al. (+2 more)
Singlet fission (SF) is a photophysical process where a singlet excitation generates two triplet excited states, enhancing
exciton multiplication potentially useful for
solar energy conversion. Since SF typically outcompetes radiative decay, single molecule studies of SF have remained elusive. Here, we present single molecule spectroscopy of a terrylenediimide (TDI) dimer at room and cryogenic temperatures. By analysing the stream of
photons emitted by single dimers, the rates of formation and decay of SF-born triplet states were determined. We report considerable static and dynamic heterogeneities of the SF process which are reflected in broad rate distributions as well as the occasional occurrence of delayed fluorescence and rate fluctuations during
spin evolution. Cryogenic experiments point to the formation of a coherent multiexciton superposition state which decays into the singlet
exciton from which a correlated triplet pair evolves. Our results establish single molecule spectroscopy as a new avenue into mechanistic details of the SF process which often are drowned by ensemble av-eraging.
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All authors Sumanta Paul, Oleksandr Yampolskyy, Zehua Wu, Klaus Müllen, Thomas Basché
General Physics
Jacobi's principle of stationary full action and its implications
Vitaliy Voytik
The purpose of this article is to extend the applicability of the principle of stationary Jacobi action to non-conservative natural systems and to derive the equations of motion corresponding to this generalized principle. To this end, in addition to the well-known variation of the Jacobi action with respect to coordinates, we introduce an independent variation of time. Small variations in both coordinates and time are considered at points along the actual trajectory, subject to standard boundary conditions.
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Classical Physics
Euler's elastica in nonlocal theory of elasticity
Vasyl Kovalchuk, Ewa Eliza Rożko and Barbara Gołubowska
A generalization of the Euler's elastic problem, i.e., finding a stationary configuration (planar elastica) of the Bernoulli's thin ideal elastic rod with boundary conditions defined through fixed endpoints and/or tangents at the endpoints, for the chosen nonlocal differential constitutive stress-strain relation (i.e., nonlocal theory of elasticity) is considered. In the classical (local) Euler-Bernoulli's beam model, the general solutions of the governing equations (that are inhomogeneous but linear) for bending moments and shear forces in the case of large deformations can be obtained using the Jacobi
elliptic functions and incomplete
elliptic integrals. For the discussed nonlocal toy differential model, the general solutions of the governing equations (that are this time nonlinear) can also be expressed in the parametric form through the linear combinations of all three incomplete
elliptic integrals. As further research, we plan to apply some boundary conditions (clamped, simply supported, etc.) for the obtained nonlocal general solutions in order to compare them to the local solutions for the corresponding boundary value problems.
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Atomic Physics
Parity Nonconservation in Rb and Sr$^+$ due to Low-Mass Vector Boson
V. A. Dzuba, V. V. Flambaum and G. K. Vong
We calculate the parity non-conserving (PNC) electric-dipole ($E1$) transition amplitudes for the $5s - 6s$ and $5s - 4d_{3/2}$ transitions in Rb and Sr$^+$. Our results include both the
nuclear-
spin-independent and
nuclear-
spin-dependent contributions, with particular emphasis on the potential effects of a hypothetical additional $Z'$-
boson. We highlight possible advantages of using light atoms in searches for such new interaction. The ratio of the contribution of a low mass $Z'$-
boson to the contribution of the Standard model $Z$ -
boson to PNC effects increases rapidly (faster than $1/Z^2$) with decreasing
nuclear charge $Z$. Another advantage is that theoretical interpretations of experiments in lighter systems may be carried out with a higher accuracy than that in Cs, Ba$^+$, Fr and Ra$^+$.
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Fluid Dynamics
Mesoscale Simulations of Thrombin Activation and Fibrin Formation in Microvascular and In Vitro Settings
Marina Echeverria-Ferrero, Nicolas Moreno and Marco Ellero
Blood coagulation is governed by tightly regulated reaction networks that unfold within a flowing, heterogeneous microvascular environment. Reduced kinetic models of the intrinsic and extrinsic pathways have seen limited in vitro validation, and their behavior within spatially resolved flow fields remains largely unexplored. Here, we embed two established reduced networks into a recently proposed mesoscale particle-based framework that resolves fluid momentum transport alongside multispecies advection-
diffusion-reaction dynamics. We investigate the initiation phase of coagulation by simulating thrombin formation in microvascular geometries and in vitro assays, and we assess the framework's ability to reproduce thrombin generation curves (TGCs) under physiologically relevant conditions. We further examine how variations in fibrinogen levels - an important determinant of clot structure and a biomarker for inflammation and thrombosis - affect thrombin and fibrin formation. Overall, this study provides a unified computational approach for analysing how biochemical kinetics interact with transport processes, offering insights relevant to thrombosis modeling and blood diagnostics.
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Data Analysis and Statistics · Cross-listed from cs.LG
On the continuity of flows
Congzhou M Sha
Flow matching has emerged as a powerful framework for generative modeling through continuous normalizing flows. We investigate a potential topological constraint: when the prior distribution and target distribution have mismatched
topology (e.g., unimodal to
multimodal), the optimal velocity field under standard flow matching objectives may exhibit spatial discontinuities. We suggest that this discontinuity arises from the requirement that continuous flows must bifurcate to map a single mode to multiple modes, forcing particles to make discrete routing decisions at intermediate times. Through theoretical analysis on bimodal Gaussian mixtures, we demonstrate that the optimal velocity field exhibits jump discontinuities along decision boundaries, with magnitude approaching infinity as time approaches the target distribution. Our analysis suggests that this phenomenon is not specific to $L^2$ loss, but rather may be a consequence of topological mismatch between distributions. We validate our theory empirically and discuss potential implications for flow matching on
manifolds, connecting our findings to recent work on Riemannian flow matching and the challenge of learning discontinuous representations in neural networks.
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Geophysics
Diffusion Model-Based Posterior Sampling in Full Waveform Inversion
Mohammad H. Taufik and Tariq Alkhalifah
Bayesian full waveform inversion (FWI) offers uncertainty-aware subsurface models; however, posterior sampling directly on observed seismic shot records is rarely practical at the field scale because each sample requires numerous wave-equation solves. We aim to make such sampling feasible for large surveys while preserving calibration, that is, high uncertainty in less illuminated areas. Our approach couples
diffusion-based posterior sampling with simultaneous-source FWI data. At each
diffusion noise level, a network predicts a clean velocity model. We then apply a
stochastic refinement step in model space using Langevin dynamics under the wave-equation likelihood and reintroduce noise to decouple successive levels before proceeding. Simultaneous-source batches reduce forward and adjoint solves approximately in proportion to the supergather size, while an unconditional
diffusion prior trained on velocity patches and volumes helps suppress source-related numerical artefacts. We evaluate the method on three 2D synthetic
datasets (SEG/EAGE Overthrust, SEG/EAGE Salt, SEAM Arid), a 2D field line, and a 3D upscaling study. Relative to a particle-based variational baseline, namely Stein variational gradient descent without a learned prior and with single-source (non-simultaneous-source) FWI, our sampler achieves lower model error and better data fit at a substantially reduced computational cost. By aligning encoded-shot likelihoods with
diffusion-based sampling and exploiting straightforward parallelization over samples and source batches, the method provides a practical path to calibrated posterior inference on observed shot records that scales to large 2D and 3D problems.
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Space Physics
Solar Energetic Particle Forecasting with Multi-Task Deep Learning: SEPNET
Yian Yu, Yang Chen, Lulu Zhao et al. (+3 more)
Solar energetic particle (SEP) events pose severe threats to spacecraft, astronaut safety, and aviation operations. Accurate SEP
forecasting remains a critical challenge in space weather research due to their complex origins and highly variable propagation. In this work, we built SEPNET, an innovative multi-task neural network that jointly predicts future
solar eruptive events, including
solar flares and coronal mass ejections (CMEs) and SEPs, incorporating long short-term
memory and
transformer architectures that capture contextual dependencies. SEPNet is a machine learning framework for SEP prediction that utilizes an extensive set of predictors, including
solar flares, CMEs, and space-weather HMI active region patches (SHARP)
magnetic field parameters. SEPNET is rigorously evaluated on the SEPVAL SEP
dataset (Whitman, 2025b), which is used to evaluate the performance of the current SEP prediction models. The performance of SEPNet is compared with classical machine learning methods and current state-of-the-art pre-eruptive SEP prediction models. The results show that SEPNET, particularly with SHARP parameters, achieves higher detection rates and skill scores while maintaining suitable for real-time space weather alert operations. Although class imbalance in the data leads to relatively high false alarm rates, SEPNET consistently outperforms reference methods and provides timely SEP forecasts, highlighting the capability of deep multi-task learning for next-generation space weather prediction. All data and code are available on GitHub at https://github.com/yuyian/SEP-Prediction.git.
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All authors Yian Yu, Yang Chen, Lulu Zhao, Kathryn Whitman, Ward Manchester, Tamas Gombosi
Optics
Intracavity-birefringence-enabled soliton states and wavelength control in the (C + L)-band fiber lasers
Chuangkai Li, Feng Ye, Hong Jin et al. (+4 more)
We demonstrate a compact all-fiber nonlinear-polarization-
evolution (NPE) fiber
laser capable of outputting wavelength-manipulated multiple
laser states in the C + L band. Leveraging the intracavity birefringence-induced filtering effect, without external spectral filters, the
laser achieves wavelength-tunable conventional
solitons (CSs) and
soliton molecules (SMs) with a tuning range of 72.85 nm and 45.54 nm, respectively, by adjusting the polarization states and pump power. Furthermore, wavelength-switchable harmonic mode-locking (over 1 GHz) and dual-wavelength mode-locking can also be achieved in the C + L band. To the best of our knowledge, this is the first experimental realization of wavelength-manipulated multiple
soliton states covering the C + L band in a single-fiber-
laser oscillator. Two examples of digital multi-letter encoding and transmission are further demonstrated on this platform by means of pump-driven wavelength/
soliton states switching. By enabling controllable multi-state
solitons and broad spectral tunability within a compact architecture, our work provides a promising source for spectrally diverse and temporally stable pulsed light sources that hold significant promise for applications in microscopy, bioimaging, and
LiDAR.
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All authors Chuangkai Li, Feng Ye, Hong Jin, Xuanyi Liu, H. Y. Fu, Boris A. Malomed, Qian Li
Atomic Physics
A Coulomb-included model for high-order harmonic generation from atoms
Yigen Peng, Jiayin Che, Ruihua Xu et al. (+3 more)
In strong
laser-atom interactions, the Coulomb potential can affect the trajectories of rescattering electron in high-order harmonic generation (HHG). Here, by constructing a semi-analytical Coulomb-included model and comparing it with numerical experiments that allow for direct observation of electron trajectories, we identify the role of Coulomb potential in different processes of HHG. We show that the
symmetry of the system determined by Coulomb potential plays an important role in the ionization process of HHG, inducing the tunneling-out time of electrons to shift towards earlier times. This
symmetry-related effect reflects the
quantum properties of atomic systems, in sharp contrast to the classical Coulomb-induced acceleration in the recombination process. In particular, compared with other strong-filed models, the scaling law of the amplitude of HHG electron trajectories predicted by this model agrees with the numerical experiments, indicating that the model developed here can be used to quantitatively describe HHG. This model can also be used to study strong-field ionization significantly influenced by rescattering.
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All authors Yigen Peng, Jiayin Che, Ruihua Xu, Shang Wang, Xuejiao Xie, Yanjun Chen
Applied Physics · Cross-listed from cond-mat.mtrl-sci
Plasma engineered Hydroxyl Defects in NiO a DFTSupported-Spectroscopic Analysis of Oxygen Hole States and Implications for Water Oxidation
Harol Moreno Fernandez, Mohammad Amirabbasi, Crizaldo Jr. Mempin et al. (+8 more)
Controlling
lattice oxygen reactivity in earth abundant OER catalysts requires precise tuning of defect chemistry in the
oxide lattice. Here, we combine DFT+U calculations with
plasma assisted synthesis to show how O2 and H2O in the discharge govern vacancy formation, electronic structure, and catalytic predisposition in NiO thin films. Oxygen rich
plasmas generate isolated and clustered Ni vacancies that stabilize oxygen ligand hole states and produce shallow O 2p Ni 3d hybrid levels, enhancing Ni O covalency. In contrast, introducing H2O during growth drives local hydroxylation that compensates vacancy induced Ni3+ centers, restoring Ni2+ like coordination, suppressing deep divacancy derived in gap states, and introducing shallow Ni O H derived valence-band tails. EXAFS confirms that hydroxylation perturbs only the local environment while preserving the medium-range NiO
lattice, and Ni L-edge spectroscopy shows a persistent but redistributed ligand-hole population. These complementary vacancy and hydroxylation driven pathways provide a
plasma controlled route to pre define electronic defect landscapes in NiO and to tune its activation toward OER relevant NiOOH formation.
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All authors Harol Moreno Fernandez, Mohammad Amirabbasi, Crizaldo Jr. Mempin, Andrea Trapletti, Garlef Wartner, Marc F. Tesh, Esmaeil Adabifiroozjaei, Thokozile A. Kathyola, Carlo Castellano, Leopoldo Molina Luna, Jan P. Hofmann
Data Analysis and Statistics · Cross-listed from q-bio.QM
Investigating High-Order Behaviors in Multivariate Cardiovascular Interactions via Nonlinear Prediction and Information-Theoretic Tools
Chiara Barà, Yuri Antonacci, Laura Sparacino et al. (+4 more)
Assessing the synergistic high-order behaviors (HOBs) that emerge from underlying structural mechanisms is crucial to characterize complex systems. This work leverages the combined use of predictability and information measures to detect and quantify HOBs in synthetic and physiological network systems. After providing formal definitions of mechanisms and behaviors in a complex system, measures of statistical synergy are defined as the whole-minus-sum excess of mutual predictability ($\Delta_\textrm{MP}$) or mutual information ($\Delta_\textrm{MI}$) obtained when considering the system as a whole rather than as a combination of its units. The two measures are computed using model-free methods based on nonlinear prediction and
entropy estimation. The application to simulated linear Gaussian systems and nonlinear deterministic and
stochastic dynamic systems shows that $\Delta_\textrm{MP}$ tends to vanish for target variables influenced by additive effects of single independent source variables and is positive in the presence of group interactions between sources, while $\Delta_\textrm{MI}$ exhibits a higher propensity to display positive values. The analysis of physiological variables shows significant values of $\Delta_\textrm{MI}$ when investigating the additive effect of systolic and diastolic arterial pressure on mean arterial pressure, and of both $\Delta_\textrm{MP}$ and $\Delta_\textrm{MI}$ when assessing how diastolic pressure is modulated by pre-ejection and left-ventricular ejection times. HOBs can be more clearly identified by information-theoretic measures, while prediction measures are more sensitive to synergy arising from the governing rules of the system analyzed rather than from pure statistical dependencies. Quantifying HOBs through measures sensitive to structural mechanisms can provide biomarkers to assess physio-pathological alterations of cardiovascular networks.
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All authors Chiara Barà, Yuri Antonacci, Laura Sparacino, Helder Pinto, Michal Javorka, Sebastiano Stramaglia, Luca Faes
Optics
Unidirectional spectral singularity lasing in a defective atomic lattice
Chen Peng, Xinfu Zheng, Duanfu Chen et al. (+4 more)
We propose an efficient scheme for achieving mode-tunable unidirectional reflection lasing (URL) by establishing a coherent gain atomic system to amplify the probe field and ingeniously designing the one-dimensional (1D) defective atomic
lattice. This
lattice not only replaces the resonant cavity to provide a distributed feedback mechanism but also breaks the spatial
symmetry of the probe susceptibility. Correspondingly, the URL can be characterized by a non-Hermitian degenerate spectral singularity (NHDSS), where the two
eigenvalues of the inverse scattering
matrix are engineered to satisfy $\lambda _{{S^{-1}}}^{+}\simeq \lambda _{{S^{-1}}}^{-}\rightarrow 0$. This intriguing NHDSS depends on the probe susceptibility and the Bragg condition, both of which can be modulated by adjusting the external optical field and
lattice structure, rendering the scheme experimentally feasible. Our approach achieves both nonreciprocity and lasing oscillation in a single system, significantly enhancing the efficiency of optical information transmission and facilitating the integration of active photonic devices into compact
quantum networks.
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All authors Chen Peng, Xinfu Zheng, Duanfu Chen, Hanxiao Zhang, Dong Yan, Jinhui Wu, Hong Yang
Fluid Dynamics
The interactions between two drops floating on a partially miscible liquid pool
Yuan Gao and Yanshen Li
The interaction of drops floating on
liquid surfaces is important for many natural processes and industrial applications. In many of the cases, the system is multicomponent, leading to Marangoni flows on the surface. Here we investigate the competing effect of the attractive “Cheerios effect” and the repulsive solutal Marangoni flow by observing the behaviors of two identical oil drops floating on partially miscible pool made of ethanol-water mixtures. Three typical behaviors are found: Repel, Coalesce and Rebound, in which the drops repel each other, attract each other and then coalesce, and attract and rebound upon contact. A scaling theory based on the two competing forces is developed to distinguish the repulsive and attractive behaviors of the drops. For the transition from Coalesce to Rebound, a lubrication layer is found to form when the immersed lower halves of the drops are more than half a sphere, which prevents the drops from coalescing.
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Instrumentation and Detectors · Cross-listed from astro-ph.SR
HEL1OS – A Hard X-ray Spectrometer on Board Aditya-L1
Anuj Nandi, Manju Sudhakar, Srikar Paavan Tadepalli et al. (+33 more)
HEL1OS (High Energy L1 Orbiting X-ray Spectrometer) is one of the remote sensing payloads on board Aditya-L1 mission designed to continuously monitor and measure the time-resolved spectra of
solar flares between 8 keV and 150 keV. This broad energy range has been covered by using compound
semiconductor detectors: cadmium telluride (CdTe: 8 - 70 keV) and cadmium zinc telluride (CZT: 20 - 150 keV) with
geometric areas of 0.5 cm$^2$ and 32 cm$^2$, respectively. A stainless steel collimator provides a field-of-view of 6$^\circ$ $\times$ 6$^\circ$ optimized to limit the off-axis response while keeping the design within the instrument mass constraints. The in-house designed low-noise digital pulse processing-based front-end electronics has achieved a spectral resolution of $\approx$ 1 keV at 14 keV (CdTe) and $\approx$ 7 keV at 60 keV (CZT). The instrument is also equipped with processing and power electronics to process the signal, drive the electronics, bias the detectors with required low and high voltages for optimal performance of the overall system. In this article, we present design aspects of the instrument, results from the pre-launch ground-based tests, and the in-orbit operations, which have indicated optimal performance in line with that expected.
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All authors Anuj Nandi, Manju Sudhakar, Srikar Paavan Tadepalli, Anand Jain, Brajpal Singh, Reenu Palawat, Ravishankar B. T., Bhuwan Joshi, Monoj Bug, Anurag Tyagi, Sumit Kumar, Mukund Kumar Thakur, Akanksha Baggan, Srikanth T., Arjun Dey, Veeresha D. R., Abhijit Avinash Adoni, Padmanabhan, Vivechana M. S., Evangelin Leeja Justin, James M. P., Kinshuk Gupta, Shalini Maiya P. R., Lakshmi A., Sajjade Faisal Mustafa, Vivek R. Subramanian, Gayatri Malhotra, Shree Niwas Sahu, Murugiah S., Medasani Thejasree, Narayan Rao G. S., T Rethika., Motamarri Srikanth, Ravi A., Nashiket Premlal Parate, Nigar Shaji
Biological Physics
Quantum Correlation and Synchronisation-Enhanced Energy Transfer in Driven-Dissipative Light-Harvesting Dimers
Wenhao Xu
Quantum synchronisation has recently been proposed as a mechanism for electronic excitation energy transfer in light-harvesting complexes, yet its robustness in driven-dissipative settings remains under active investigation. Here, we revisit this mechanism in cryptophyte photosynthetic
antennae using an
exciton–vibrational dimer model. By comparing the full open
quantum dynamics with semi-classical rate equations for electronic density-
matrix elements and vibrational observables, we demonstrate that
quantum correlations between electronic and vibrational degrees of freedom, beyond the semi-classical factorised limit, underpin the emergence of
quantum synchronisation. Furthermore, we introduce an environment-assisted transfer mechanism arising as a nonlinear, non-Condon correction to the dipole–dipole interaction. This mechanism enables long-lived
quantum coherence and continuous, synchronisation-enhanced energy transfer in a driven-dissipative regime, thereby suggesting new avenues for investigating photosynthetic energy-transfer dynamics.
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Fluid Dynamics
Integrating Fourier Neural Operator with Diffusion Model for Autoregressive Predictions of Three-dimensional Turbulence
Yuchi Jiang, Yunpeng Wang, Huiyu Yang et al. (+1 more)
Accurately autoregressive prediction of three-dimensional (3D)
turbulence has been one of the most challenging problems for machine learning approaches.
Diffusion models have demonstrated high accuracy in predicting two-dimensional (2D)
turbulence, but their applications in 3D
turbulence are relatively limited. To achieve reliable autoregressive predictions of 3D
turbulence, we propose the DiAFNO model which integrates the implicit adaptive
Fourier neural operator (IAFNO) with
diffusion model. IAFNO can effectively capture the global frequency and structural features, which is crucial for global consistent reconstructions of the denoising process in
diffusion models. Furthermore, based on conditional generation from
diffusion models, we design an autoregressive framework in DiAFNO to achieve long-term stable predictions of 3D
turbulence. The proposed DiAFNO model is systematically trained and tested separately with fixed hyperparameters in several types of 3D
turbulence, including forced homogeneous isotropic
turbulence (HIT) at Taylor Reynolds number 100, decaying HIT at initial Taylor Reynolds number at 100 and turbulent channel flow at friction Reynolds numbers 395 and 590 with case-specific training at each Reynolds number. The results in the a posteriori tests demonstrate that DiAFNO exhibits a significantly higher prediction accuracy in most of the analyzed statistics (such as the velocity spectra, the root-mean-square (RMS) values of both velocity and vorticity, and Reynolds stresses), as compared to the elucidated
diffusion model (EDM) and the traditional large-eddy simulation (LES) using dynamic Smagorinsky model (DSM). Although DiAFNO is not optimal in certain statistics, its overall performance is substantially better than all baseline models (EDM and DSM). Ignoring training costs, the well-trained DiAFNO achieves higher inference efficiency than EDM and LES with DSM.
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All authors Yuchi Jiang, Yunpeng Wang, Huiyu Yang, Jianchun Wang
Optics
Deep-learning-enabled inverse design of large-scale metasurfaces with full-wave accuracy
Borui Xu, Jingzhu Shao, Xiangyu Zhao et al. (+8 more)
Recent advances in meta-optics have enabled diverse functionalities in compact optical devices; however, conventional forward design approaches become inadequate as device complexity and scale grow. Inverse design offers a powerful alternative but often requires massive computational resources and neglects mutual coupling effects. Here, we propose and experimentally validate a deep-learning-enabled framework for rapid inverse design of large-scale, aperiodic metasurfaces with full-wave accuracy.The framework integrates an inverse design network responsible that maps target near-field responses to metasurface geometries in a non-iterative and scalable manner. A lightweight forward prediction network, integrated as a full-wave solver surrogate within the framework, enables efficient end-to-end training of the inverse design network while capturing mutual coupling effects by considering both local and neighboring geometries.The framework's effectiveness is experimentally verified through a multi-foci metalens and a
holographic metasurface. This framework enables the inverse design from micrometer to centimeter scales (> 20k{\lambda}), with near-field responses discrepancies less than 3% compared to full-wave solvers at subwavelength (< {\lambda}/10) resolution.Moreover, it is generalizable to metasurfaces of arbitrary size and operates efficiently without high-performance resources, overcoming the computational bottlenecks of previous inverse design methods.
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All authors Borui Xu, Jingzhu Shao, Xiangyu Zhao, Haishan Xu, Yudong Tian, Nanxi Chen, Jielin Sun, Han Lin, Qiaoliang Bao, Yiyong Mai, Chongzhao Wu
Optics
Soliton-Assisted Massive Signal Broadcasting via Exceptional Points
Zhuang Fan, Yukun Huang, Wenchan Dong et al. (+8 more)
Chip-scale all-optical signal broadcasting enables data replication from an optical signal to a large number of wavelength channels, playing a critical role in enabling massive-throughput optical communication and computing systems. The underlying process is four-wave mixing between an optical signal and a multi-wavelength pump source via optical Kerr nonlinearity. To enhance the generally weak nonlinearity, high-quality (Q) microcavities are commonly used to achieve practical efficiency. However, the ultra-narrow linewidths of high Q cavities prohibit achieving massive throughput broadcasting due to
Fourier reciprocity. Here, we overcome this challenge by harnessing a parity-time symmetric coupled-cavity system that supports equally spaced exceptional points in the frequency domain. This design seamlessly integrates generation of dissipative Kerr
soliton comb source and all-optical signal broadcasting into a unified nonlinear process. As a result, we realize
soliton-assisted intracavity massive signal broadcasting with a channel count exceeding 100 over 200 nm wavelength range, resulting in Terabit-per-second aggregated rates. This throughput surpasses the intrinsic microcavity linewidth constraint (~200 MHz) by over three orders of magnitude. We further demonstrate the utility of this approach through an optical convolutional accelerator, highlighting its potential to enable transformative capabilities in photonic computing. Our work establishes a new paradigm for chip-scale photonic processing devices based on non-Hermitian optical design.
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All authors Zhuang Fan, Yukun Huang, Wenchan Dong, Haodong Yang, Jiahao Hu, Yizheng Chen, Hanghang Li, Nuo Chen, Heng Zhou, Jing Xu, Xinliang Zhang
Space Physics
What are Switchbacks?
Zesen Huang, Marco Velli and Yuliang Ding
We present a solitary Alfvén wave model that exhibits nontrivial three-dimensional twisting of open
magnetic field lines while preserving constant $|B|$. Embedded rotational discontinuities sharply deflect the otherwise uniform field lines, producing localized, large-amplitude field reversals in one-dimensional profiles that closely resemble the “switchbacks” observed by the Parker
Solar Probe in the inner heliosphere. This indicates that switchbacks, as seen in one-dimensional spacecraft time series, arise from traversals through strongly curved segments of open
magnetic field lines.
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Chemical Physics
Extended dissipaton theory for higher-order bath couplings and application to non-Condon spectroscopy with anharmonicity
Zi-Fan Zhu, Yu Su, Yao Wang et al. (+2 more)
In this work, we develop an extended dissipaton theory that generalizes the environmental couplings beyond the conventional linear and quadratic forms, enabling the treatment of arbitrary order of bath couplings. Applying this theoretical framework to the condensed-phase non-Condon spectroscopy, we demonstrate the interplay of anharmonicity, non-Condon and solvent effects on optical spectra. Precise simulations are carried out with high efficiency on linear absorption spectra involving the above mentioned correlated effects. We exhibit how an anharmonic potential modulates the vibronic feature, offering insights into the role of nonlinear environmental couplings in spectroscopic signatures and exemplifying the success of the extended dissipaton formalism as an exact and efficient method for higher-order bath couplings.
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All authors Zi-Fan Zhu, Yu Su, Yao Wang, Rui-Xue Xu, YiJing Yan
Chemical Physics
Mechanisms of inductively coupled BCl3-plasma interaction with the GaN surfaceMechanisms of inductively coupled BCl3-plasma interaction with the GaN surface
Anton Kobelev, Nikolay Andrianov, Yuri Barsukov et al. (+1 more)
Consideration is given to inductively coupled BCl3-
plasma (ICP) treatment of the GaN surface, which is a promising technique to get the low resistance ohmic contacts in GaN-based transistors. In some cases, BCl3
plasma treatment results in ohmic contact degradation because BClx radicals tend to form a
polymer thin film BxCly on the surface. In the present work, the mechanisms of BCl3
plasma interaction with the GaN surface are considered. Threshold ion energies of reactive ion etching for
polymer BxCly and
semiconductor GaN, respectively, are estimated using numerical
plasma modeling. It has been demonstrated that a
plasma treatment regime without
polymer deposition and reactive etching is possible when an ion energy is in the range ~32-60 eV.
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All authors Anton Kobelev, Nikolay Andrianov, Yuri Barsukov, Alexander Smirnov