Pattern Formation and Solitons
Controllable excitation of vector Akhmediev breather patterns
Yan-Hong Qin, Ning Cao and Li-Chen Zhao
In the focusing Manakov system, multiple modulation instability (MI) branches coexist on the same plane wave background, so the usual weak periodic modulation cannot selectively excite a single vector Akhmediev breather (AB). Here we propose an eigenvector-based initial perturbation scheme that constructs the initial condition as a plane wave plus
Fourier modes whose coefficients follow the perturbation eigenvector of a selected MI branch, enabling controllable high-fidelity excitation of desired vector ABs. Numerical simulations show near-100% fidelity with the exact AB solution. The underlying mechanism is eigenvector-controlled mode selection. The initial seeding of the target MI branch through the chosen eigenvector, together with the non-Hermitian coupling inherent in the linearized MI dynamics, ensures that the targeted unstable mode dominates the early linear stage and thereby dictates the breather type. This eigenvector-based control succeeds in gain-balanced regimes and when the targeted branch has a sufficient gain advantage. The proposed method provides a simple and robust framework for controllable generation of vector ABs over a broad parameter range, highlighting the key role of eigenvector selectivity in multi-component nonlinear systems.
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Instrumentation and Detectors
Characterization of GaN:Si and ZnO:Ga for position-resolved fast timing applications
Julius Meyer, Joshua W. Cates, Woon-Seng Choong et al. (+7 more)
We present the characterization of two fast, crystalline inorganic scintillators, silicon-doped gallium nitride (GaN:Si) and gallium-doped zinc
oxide (ZnO:Ga), and compare their performance with cerium-doped yttrium aluminium perovskite (YAP:Ce) for in-
vacuum alpha-detection applications that require high-performance timing, position, and energy resolution, such as 3D elemental mapping, medical imaging, and homeland security applications. In this paper, we propose ZnO:Ga and GaN:Si as high-performance drop-in replacements for the alpha detector in Associated Particle Imaging (API) systems. However, the results reported here also have wide applicability. Prior work has reported on polycrystalline forms of ZnO:Ga, which suffer from self-absorption. To our knowledge, GaN:Si has not been proposed to be used in API systems. We present room-temperature scintillation time constants obtained via X-ray-induced time-correlated single-
photon counting for both proposed materials. They both exhibit exceedingly fast rise times of <15ps, and high brightness >1000ph/MeV with resolved alpha-peaks. Single-
crystal ZnO:Ga and single-
crystal GaN:Si yield single-component decays of 805ps and 32ps, respectively. Using a plastic scintillator reference setup, coincidence timing resolution (CTR) and detector timing resolution (DTR) measurements demonstrate a >3x improvement in timing resolution compared to traditional YAP:Ce. GaN:Si and ZnO:Ga exhibit (35(9))ps and (49(5))ps DTR, respectively, compared to(144(2))ps for conventional, single-
crystal YAP:Ce. Finally, we evaluate their position resolution in an experimental setup designed for API and measure better than 0.2mm for YAP:Ce and approximately 1mm for GaN:Si. We obtain a position resolution of 0.3mm for ZnO:Ga from simulations. We also present alpha-induced ionoluminescence emission spectra that reveal direct, red-shifted near-bandgap emission.
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All authors Julius Meyer, Joshua W. Cates, Woon-Seng Choong, Juan Cristhian Luque Gutierrez, Federico Moretti, Ryan Pavlovsky, Mauricio Ayllon Unzueta, Weronika W. Wolszczak, Markus Roth, Arun Persaud
Atmospheric and Oceanic Physics
Using Distributional Regression Networks to Retrieve Cloud Properties from Solar Satellite Channels for Data Assimilation
Stefano Franzoni, Christopher Bülte, Leonhard Scheck et al. (+2 more)
Satellite observations in the
solar spectrum (including visible and near-infrared channels) offer high-resolution information on clouds and atmospheric properties valuable for data assimilation. While forward operators for a direct assimilation of
solar images have become available recently and a first visible channel is already used operationally, their assimilation remains challenging due to strong non-linearities, ambiguities and high inter-channel correlations. This study addresses two central questions: what is the potential impact of assimilating multiple
solar channels jointly, and can observed reflectances be transformed into physically meaningful, uncertainty-quantified variables better suited to assimilation than the raw reflectances themselves? As a proof of concept, we assess the joint information content of six
solar channels from the Flexible Combined Imager (FCI) onboard Meteosat Third Generation and introduce a novel "Backward Operator" (BO) for probabilistic
retrievals of cloud-related variables. The BO is implemented in a machine learning approach as a distributional regression network that is trained on synthetic images from a NWP regional model run and produces multivariate Gaussian estimates of total optical thickness, column cloud fraction, ice fraction, and effective radii of water and ice. The BO predictions are unbiased and well-calibrated, with realistic, situation-dependent and non-trivial covariance structures. The retrieved variables can be overall usefully constrained. Despite strong inter-channel correlations, combining multiple channels yields substantial performance improvements. As the BO does not require prior information, is consistent with an existing forward operator, and yields cloud variables more linearly related to the NWP model state, assimilating these variables could be a viable alternative to direct reflectance assimilation.
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All authors Stefano Franzoni, Christopher Bülte, Leonhard Scheck, Christian Keil, George C. Craig
Plasma Physics
Reconnection-induced electron energization in magnetospheric Kelvin-Helmholtz dynamics
Silvia Ferro, Fabio Bacchini, Giuseppe Arrò et al. (+2 more)
The Kelvin-Helmholtz instability (KHI) is a major driver of multiscale
plasma dynamics at velocity shear layers, where it can promote the formation of current sheets and the onset of
magnetic reconnection as well as drive
plasma energization. While recent kinetic studies have shown efficient electron heating during nonlinear KH
evolution, the connection between reconnection dynamics and localized electron energization is still not fully understood. We investigate this link using two-dimensional fully kinetic simulations of KHI developing in a double-periodic system with two velocity shear layers and a uniform guide field, initialized from a finite-Larmor-radius
equilibrium. During the nonlinear stage, initially coherent
vortices evolve into layers populated by fragmented current sheets containing active
magnetic reconnection sites. The global energetics reveal distinct species-dependent energization pathways. Ions act as the primary energy reservoir, transferring energy to the electromagnetic fields, while electrons receive the dominant net positive energy input. Electron energization is strongly anisotropic ($T_{\parallel,e} > T_{\perp,e}$) and localized within intermittent reconnecting current sheets associated with enhanced field-particle energy exchange and elevated agyrotropy. These regions also show the development of suprathermal tails in the electron energy distributions, providing evidence for nonthermal electron energization. Despite opposite vorticity orientations, the two shear layers exhibit similar statistical behavior. Together, these results establish a direct connection between reconnection-associated current structures and localized electron energization in collisionless KHI dynamics.
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All authors Silvia Ferro, Fabio Bacchini, Giuseppe Arrò, Francesco Pucci, Pierre Henri
High Energy Astrophysical Phenomena
A broadband view of the thermal and non-thermal emission from the embedded massive star cluster RCW 38
Giada Peron, Andrea Bracco, Giovanni Morlino et al. (+4 more)
Gamma-ray emission has now been detected from a variety of source classes in the
Galaxy, including clusters of young massive
stars. RCW 38, a very young embedded massive
star cluster, is a case of particular interest: its gamma-ray emission detected up to hundreds of GeV, provided the first observational evidence of high-energy particle acceleration powered exclusively by
stellar winds. In this work, we aim to characterize the emission mechanisms responsible for the gamma-ray flux in RCW 38 and to provide estimates of the acceleration efficiency, as well as the fraction of accelerated electrons compared to
protons, $K_{ep}$. We present the most comprehensive multi-wavelength study of a single
star cluster to date. Our analysis ranges from MHz
radio observations obtained with the GLEAM-X survey from the Murchison Widefield Array (MWA) to GeV gamma-ray data from
Fermi-LAT, and includes GHz and THz measurements from Parkes, Planck, and IRAS. We model the thermal and non-thermal emission of RCW 38 using an eight-parameter model constrained by the Markov chain Monte Carlo method. Our results support an interpretation in which the gamma-ray emission from RCW 38 is produced by hadronic interactions with the host molecular cloud. We derive robust constraints on the electron-to-
proton ratio, with $K_{ep} \lesssim 10^{-3}$, and on the acceleration efficiency, estimated to be $\gtrsim$1%, consistent with the values required to explain the
cosmic-ray composition, and in particular its $^{22}$Ne anomaly. These results strengthen the idea that
stellar clusters play a significant role as contributors to
cosmic-ray
protons in our
Galaxy at least up to energies of a few TeV. Future investigations with the next generation of ground-based detectors will determine whether they also play a relevant role at higher energies, particularly in the context of the
cosmic-ray knee.
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All authors Giada Peron, Andrea Bracco, Giovanni Morlino, Silvia Mantovanini, Elena Amato, Daniele Galli, Marco Padovani
Atomic Physics
Direct evidence for projectile electronic structure effects in slow multielectron capture collisions
Akash Srivastav, Sumit Srivastav and Bhas Bapat
We investigate the role of the electronic structure of the projectile in ionization and subsequent fragmentation of CO$_2$ induced by multielectron capture in collisions at 0.31 a.u. impact velocity. Focusing on the $\text{CO}_2^{3+} \rightarrow \text{O}^+:\text{C}^+:\text{O}^+$ break-up channel as a representative channel, we report kinetic energy release distributions (KERDs) for collisions with equi-velocity N$^{q+}$ and O$^{q+}$ projectiles. We consider two complementary categories of measurements. In the first category, in which different projectiles of the same charge are considered, we find that KERDs obtained with N$^{q+}$ and O$^{q+}$ impact ($q=4,6$) are broadly similar, but they differ significantly from the earlier reported KERD with Ar$^{q+}$ impact. In the second category, pronounced differences are observed between the KERDs obtained with isoelectronic N$^{q+}$ and O$^{(q+1)+}$ ($q=3,5,7$) projectiles. These results provide direct evidence that projectile electronic structure plays a critical role in multielectron capture collisions.
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Computational Physics
MADField: Multi-fidelity Amortized Density Field for Adsorption in Nanoporous Materials
Yoonho Kim, Seongsu Kim, Sungsoo Ahn et al. (+1 more)
High-throughput computational screening of nanoporous materials for gas storage and separation requires fast and accurate characterization of adsorption
equilibrium. Particle-based grand canonical Monte Carlo (GCMC) and density-based classical density functional theory (cDFT) provide simulation-based estimates of gas uptake and adsorbate density fields, but their speed-accuracy tradeoff remains insufficient for large-scale screening. In this work, we address this gap with Multi-fidelity Amortized Density Field for Adsorption in Nanoporous Materials (MADField), which reframes adsorption prediction as
equilibrium density-field estimation. MADField learns from two complementary fidelities, combining broad and scalable cDFT density supervision with higher-fidelity GCMC density labels, and recovers gas uptake by integrating the predicted density field. MADField improves uptake accuracy over the strongest baselines by 6.0x for cDFT and 15.4x for GCMC, and its predicted fields accelerate cDFT solvers with 2.0x fewer iteration steps while recovering 42 percent of cases that fail under standard settings. Finally, we evaluate MADField for conventional CH4 working capacity screening on the 270k-structure ARC-MOF database. Within this space of extremely rare high-capacity targets, 167 in total, the model achieves 56x higher average precision than the strongest baseline and accelerates inference by five orders of magnitude compared to GCMC. By prioritizing the MADField rankings, selecting the top 1.7 percent of candidates recovers 95 percent of all targets, while the top 6 percent ensures 100 percent recall.
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All authors Yoonho Kim, Seongsu Kim, Sungsoo Ahn, Honghui Kim
Quantum Physics
Reducing measurement error with adaptivity
James Byrne, Noah Linden and Paul Skrzypczyk
We show that adaptivity, also called feed-forward, is a powerful resource in reducing the error of measurement
circuits that combine multiple uses of a noisy measuring device. In previous work, it has been shown that error in measurements can be mitigated by using the measuring device multiple times. So far, the most effective protocols have been parallel measurement schemes, where all measurements are simultaneous. We extend this idea to adaptive measurement schemes, where the results of previous measurements can influence our choice of processing further down the
circuit. We show that adaptive measurement
circuits can in general reduce overall measurement errors further than any non-adaptive measurement
circuit could with the same number of measurements. In particular, we show that for a large class of noisy two-outcome
qubit measurements, such an adaptive advantage can exist when as few as three measurements are used. We also show that the adaptive advantage is unbounded across the class of noisy two-outcome
qubit measurements, as the number of uses of the device increases. As part of this work, we devise and use methods for finding optimal measurement
circuits in both the non-adaptive and adaptive cases. In addition, we prove general results about the limits of such
circuits, both in measuring a
qubit, and more generally, a qudit.
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Materials Science
Floquet-induced anisotropic magnetoresistance and anomalous Hall effect in 2D $d$-wave altermagnets with Rashba spin-orbit coupling
Mohsen Yarmohammadi, Pieter M. Gunnink, Jairo Sinova et al. (+1 more)
Altermagnets (AMs) combine momentum-dependent
spin splitting with zero net magnetization, making them promising for spintronics. Periodic driving enables dynamic
symmetry engineering beyond static, material-specific control. We show that Floquet engineering in 2D $d$-wave AMs with out-of-plane Néel order and Rashba
spin-orbit coupling unlocks
equilibrium-forbidden transport responses. Monochromatic driving produces purely out-of-plane magnetization, yielding longitudinal anisotropic magnetoresistance (AMR) and an anomalous
Hall effect, whereas bichromatic driving generates both in-plane and out-of-plane magnetizations and additionally activates transverse AMR via the second harmonic of the secondary beam. Comparable static
magnetic fields would require hundreds of tesla, avoided in Floquet driving. These effects persist across linear, circular, and mixed light polarizations and are tunable via light parameters. Our results establish multi-color Floquet engineering for controlling magnetization and
symmetry-protected transport in AMs.
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All authors Mohsen Yarmohammadi, Pieter M. Gunnink, Jairo Sinova, James K. Freericks
Atmospheric and Oceanic Physics
Elastic Non-Uniform FFT (ENUFFT) spectral reconstruction of irregularly sampled orography on unstructured grids
Tridib Banerjee, Felix Jochum and Ulrich Achatz
Subgrid-scale orography remains a leading source of uncertainty in numerical modeling because terrain spectra must be recovered from irregularly sampled elevation data and then reduced to a flow-dependent launch budget for parameterizations. Existing approaches are limited either by assuming regular samples on rectangular grids or by fitting coefficients whose truncation and regularization effects become embedded in the spectrum. None achieves dynamic, flow-dependent truncation. This study introduces an Elastic Non-Uniform Fast
Fourier Transform (ENUFFT) framework that computes local
Fourier coefficients directly from irregularly sampled orography on unstructured grids, without interpolation or fitting. It combines a type-1 NUFFT with local windowing, quadrature weights, and a new Elastic Mode Selection (EMS)
algorithm for retaining a local flow-dependent subset of modes. ENUFFT is compared with the strongest relevant existing method in a monochromatic and a real Alpine terrain test. In both cases, it recovers peak amplitude and direction comparably while significantly compacting the spectra (monochromatic ~25%, Alpine ~60%). It also satisfies the Parseval condition more closely with its spectral variance (energy) deviating from reference by ~14-24% versus ~500-122,000% for the existing method. Its EMS is additionally tested in a mountain-wave test where it reduces the launch spectrum by >=75% while keeping launch-power loss <=7%. Along with better compute scaling, ENUFFT is thus a computationally efficient, physically interpretable framework that can make
Fourier-based orographic source descriptions practical for spectral-budget-aware parameterizations.
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Optics
Nested active pointing control for interspacecraft laser interferometry
Daikang Wei, Christoph Bode, Yihao Yan et al. (+3 more)
Precise pointing control is critical for interspacecraft
laser interferometry, as angular misalignment introduces measurement noise and can even lead to
laser link loss. We present a nested control architecture that uses differential wavefront sensing signals to drive a fast steering mirror (FSM) to track the incoming beam, while feeding the FSM deflections back to the attitude and orbit control system to suppress angle-dependent optical path variations. This scheme is experimentally validated in our hexapod-based setup. Relative to standalone FSM actuation, the nested configuration reduced the low-frequency root-mean-square pointing jitter by approximately a factor of 2 over 3–70 mHz in both directions. Additionally, tilt-to-length coupling was suppressed by an order of magnitude below 5 mHz and by two orders of magnitude below 0.5 mHz. These results demonstrate the feasibility of nested active pointing control for future interspacecraft
laser interferometry missions.
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All authors Daikang Wei, Christoph Bode, Yihao Yan, Vitali Müller, Juan José Esteban Delgado, Gerhard Heinzel
Optics
Non-line-of-sight imaging with arbitrary relay surface geometries via 3D Gaussian Transient Rendering
Yi Wang, Ziyu Zhan, Yuran Wang et al. (+5 more)
Imaging objects hidden outside the direct line of sight expands the effective field of view and is critical for applications such as autonomous driving and robotic perception. Despite impressive progress in time-of-flight (ToF)-based non-line-of-sight (NLOS) imaging, real-world deployment remains challenging because practical measurements are often collected over spatially limited, arbitrarily shaped relay regions-conditions that violate the planar-wall and dense-sampling assumptions made by most existing methods. To address these limitations, we propose a LOS-guided NLOS imaging pipeline that imposes no
geometric assumptions on the relay surface and naturally supports both confocal and non-confocal configurations. Our method represents the hidden scene using 3D Gaussian primitives and couples them with an efficient, differentiable transient rendering model, enabling end-to-end optimization directly from measured transients. We validate our approach on real-world measurements from both a public
dataset and a custom-built capture system. Across settings, our method achieves state-of-the-art reconstruction fidelity under spatially limited, sparsely sampled conditions, and significantly outperforms existing methods on complex, arbitrary relay surface geometries.
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All authors Yi Wang, Ziyu Zhan, Yuran Wang, Hao Wang, Qiang Liu, Zuoqiang Shi, Lingyun Qiu, Xing Fu
Nuclear Experiment
Evidence of the Excited X(5)-like Critical-Point Symmetry Structures in 152Sm
S. Basak, S. Rajbanshi, T. Bhattacharjee et al. (+23 more)
The positive-parity structure of 152Sm has been investigated through high-statistics {\gamma}-ray spectroscopy following the (150Nd({\alpha},2n)152Sm reaction at Elab = 26 MeV. Several collective structures built on excited 0+ states have been extended through the observation of new levels and {\gamma}-ray transitions, and
spin-parity assignments have been established using directional-correlation and linear-polarization measurements. Electromagnetic transition strengths (B(E2)), deduced from measured branching ratios and known level lifetimes, reveal pronounced collectivity among the excited configurations. The resulting level scheme provides evidence for a sequence of excited collective bands extending beyond the well-known ground-state and first excited 0+ structures. The excitation energies and transition strengths are examined within the framework of the X(5) critical-point description of the first-order U(5)-SU(3) shape-phase transition. In addition to the established X(5)-like features of the low-lying spectrum, the observed systematics of the higher-lying bands are found to be consistent with excited collective structures exhibiting X(5)-like characteristics. The results provide new constraints on the realization of critical-point behavior in finite
nuclei and on the
evolution of collectivity in the N=90 region.
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All authors S. Basak, S. Rajbanshi, T. Bhattacharjee, D. Kumar, A. Pal, S. S. Alam, A. Saha, A. K. Sikdar, J. Nandi, Ananya Das, Shabir Dar, S. Samanta, S. Chatterjee, R. Raut, S. S. Ghugre, A. Adhikari, Y. Sapkota, R. Rahaman, A. Gupta, A. Bisoi, S. Sharma, S. Das, P. Das, U. Datta, I. Ray, G. Duchêne
Materials Science
Strain induced magnetic phase transitions in Fe3GeTe2 monolayer
Anjali Jyothi Bhasu, Satish Kumar, Mátyás Török et al. (+11 more)
We investigate the
magnetic properties of a monolayer of Fe3GeTe2 as a function of the
lattice constant by combining first-principles calculations with atomistic
spin dynamics simulations. The calculated
magnetic exchange interactions reveal a competition between
ferromagnetic and
antiferromagnetic couplings, with the latter being significantly strengthened under compressive strain.
Stochastic Landau-Lifshitz-Gilbert simulations reveal a substantial decrease in the Curie temperature with decreasing
lattice constant, and predict a transition of the
magnetic ground state from a
ferromagnetic configuration to a conical
spin-spiral state. We introduce a simple
spin-model which explains the stabilization of the spiral phase due to competing exchange interactions. We found multiple
magnetic phase transitions involving
ferromagnetic, conical
spin-spiral, and planar Neel states, depending on both the
lattice constant and the temperature. The absence of Dzyaloshinskii-Moriya interactions is found to significantly reduce the Neel temperature, while leaving the Curie temperature largely unaffected. Our findings reveal the importance of
lattice distortions in controlling complex
magnetic phases and their
evolution with temperature.
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All authors Anjali Jyothi Bhasu, Satish Kumar, Mátyás Török, Dániel Tibor Pozsár, Bendegúz Nyári, László Udvardi, Gabriel Martínez-Carracedo, Balázs Nagyfalusi, Amador García-Fuente, Jaime Ferrer, Zoltán Tajkov, László Oroszlány, Levente Rózsa, László Szunyogh
Plasma Physics
Semi-local Floquet theory for active azimuthal magnetic modulation of Hall-thruster high-frequency instabilities
Yinjian Zhao and Changzheng Hu
We develop a semi-local Floquet model to screen active azimuthal
magnetic modulation as a control approach for high-frequency drift instabilities in
Hall thrusters. The uniform-field kinetic response supplies a local kernel for a finite sideband
matrix, and stability is measured by the upper growth envelope over the Bloch zone. Root searches include both frequency branches, continuation, singular-value validation, and contour root counts. At the reference normalized parallel wave number k_z = 0.045, for sinusoidal profiles with periods of 10, 20, and 40 mm, every nonzero sampled modulation amplitude increases both the peak and integrated positive Bloch-zone growth. The uniform-field reference is already unstable, so these increases describe faster linear amplification rather than the onset of instability from a stable state. At a period of 20 mm and relative amplitude 0.5, the peak and integral increase by 26.74 and 26.44 percent, respectively; this large amplitude requires caution within the semi-local ordering. Selected projected wave-number windows still show reductions, but these coexist with enhanced global growth and do not establish stabilization. A supplementary parallel-wave-number scan finds weak global growth reduction at k_z = 0.09: at 20 mm and amplitude 0.3, the peak and integral decrease by 0.300 and 0.299 percent, respectively, while the spectrum remains unstable. The sign and magnitude of the modulation effect therefore depend on the tested
plasma parameters; neither these small reductions nor the local projected changes establish improved nonlinear transport.
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Nuclear Theory
Level rearrangement in K- p system
T. Massimino, N.V. Shevchenko, Z. Papp et al. (+1 more)
We studied the level shifts in the $K^- p$ system caused by the interplay of strong
nuclear and long range Coulomb potentials. We observed a level rearrangement in the system and found that the $1s$ shift of kaonic hydrogen is in fact “attractive”. In addition, we demonstrated that absorption in the strong antikaon-nucleon interaction does not destroy the level rearrangement.
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All authors T. Massimino, N.V. Shevchenko, Z. Papp, J. Revai
Accelerator Physics
Role of the Local Electric-Field in High-Field Conditioning of DC Electrodes:Numerical and Experimental Insights
Victoria Madeleine Bjelland, William Lee Millar, Morten Kildemo et al. (+1 more)
Conditioning, the progressive increase of voltage-holding through the controlled application of fields, is an important and widely used process for bringing high-field and high-voltage devices up to their full operating parameters. Here, a study is presented on how conditioning can vary within a device, specifically, when there is a spatial variation in the surface electric field. What has been observed in high-field pulsed direct-current electrodes and
radio-frequency structures is that locations exposed to higher fields exhibit a greater tendency to breakdown, but this increase is counteracted by an increased conditioning rate. This interplay explains the observed breakdown locations and provides important insights into the mechanisms underlying both conditioning and breakdown. This study combines Monte Carlo simulations with experimental results from pairs of high-field electrodes with a radially varying surface electric field. Results are presented from a high-field pulsed DC system, in which the position of each breakdown during conditioning was recorded by triangulation using a pair of cameras, and the results are compared with Monte Carlo simulations.
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All authors Victoria Madeleine Bjelland, William Lee Millar, Morten Kildemo, Walter Wuensch
Mesoscale and Nanoscale Physics
Topological Hall Effect in Antiferromagnetic Co doped Fe$_3$GaTe$_2$
Shyam Raj Karullithodi, Yeonkyu Lee, Vadym Kulichenko et al. (+8 more)
Fe$_3$GaTe$_2$ is van der Waals (vdW) ferromagnet with a Curie temperature $T_C$ ranging from 350 K to 380 K, followed upon cooling by a ferrimagnetic transition near room temperature. Substituting Fe with Co was previously reported to induce antiferromagnetism (AFM) at a Co fraction dependent Neel temperature $T_N$. In this work, we confirm the overall phase diagram of the Fe$_{3-x}$Co$_x$GaTe$_2$ series as a function of $x$ and temperature via magnetization and electrical transport measurements. For $x \simeq 0.6$ the
Hall effect is observed to mimic the magnetization as the AF ground state is suppressed by the external
magnetic field via a metamagnetic transition, thus displaying an anomalous
Hall response. At low temperatures, we also observe a pronounced topological
Hall signal peaking at $\mu_0H$ = 4 T, or within the metamagnetic transition region of fields. This observation points to the presence of
magnetic field-induced
chiral spin textures, such as skyrmions upon approaching magnetization saturation.
Magnetic force microscopy (MFM) reveals the emergence of nearly circular
magnetic domains, with diameters on the order of 100 to 200 nm, within the
antiferromagnetic phase. A detailed analysis of the MFM images indicates that the topological
Hall effect is closely linked to the field-induced stabilization of
magnetic domain structures, likely exhibiting
chiral textures. This observation suggests the possible formation of skyrmions already in the AFM phase, i.e., AFM skyrmions, that evolve into
ferromagnetic (FM) ones upon increasing the
magnetic field. Consequently, Co-doped Fe$_3$GaTe$_2$ might provide a platform to investigate the transformation of skyrmions, initially coupled antiferromagnetically into
ferromagnetic skyrmions, and to explore its impact on the topological and skyrmion
Hall effects.
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All authors Shyam Raj Karullithodi, Yeonkyu Lee, Vadym Kulichenko, W. Kice Brown, Sang-Eon Lee, Chanyoung Lee, Jinyoung Yun, Gregory T. McCandless, Julia Y. Chan, Jeehoon Kim, Luis Balicas
Computational Physics
AI-accelerated metallized $\sigma$-bonding screening for superconductor discovery
Zechen Tang, Wen-Han Dong, Baochun Wu et al. (+11 more)
The computational discovery of
phonon-mediated
superconductors is hindered by the prohibitive cost of density functional perturbation theory (DFPT). Here, guided by the metallized $\sigma$-bonding picture, we introduce the $\sigma$-bonding density of states ($\sigma$DOS) as an efficient physical descriptor to identify high-transition-temperature ($T_{\mathrm{c}}$)
superconductors from density functional theory (DFT)-level electronic structure without explicit DFPT calculations. The evaluation of $\sigma$DOS can be further accelerated by a deep-learning DFT
Hamiltonian method, enabling efficient large-scale screening for
superconductors. Screening 2 million materials, we identify B$_{13}$Se as an ambient-pressure
superconductor candidate with predicted $T_{\mathrm{c}} > 40$~K, together with a family of high-$T_{\mathrm{c}}$ B$_{13}X$ candidates, supporting the effectiveness of this discovery strategy. By bridging physics priors with AI acceleration, this study delivers an efficient and generalizable route for computational materials discovery in the AI era.
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All authors Zechen Tang, Wen-Han Dong, Baochun Wu, Jian-Feng Zhang, Yuxiang Wang, Yang Li, Honggeng Tao, Qiyu Zeng, Chong Wang, Chen Si, Zhong-Yi Lu, Wenhui Duan, Tao Xiang, Yong Xu
High Energy Physics (Theory)
Phase diagram of the massless Gross-Neveu model with two components
Michael Thies
Recently, Benini, Mamroud, Reis and Serone have presented exact results for the Gross-Neveu model at finite density, both at finite N and in the large N limit. Generalizing previous studies, they introduce a chemical potential acting only on a subset of
fermion flavors - the two-component Gross-Neveu model. Here, we take up this idea and extend the semiclassical study to finite temperature. The full (large N) phase diagram including inhomogeneous phases is constructed without solving the thermal Hartree-Fock problem. All phase boundaries can be found on the basis of various kinds of stability analyses. As a result, we find a qualitative change of the phase diagram at some critical filling fraction.
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Instrumentation and Methods for Astrophysics
High multiplex and precision: the design and development of FLEX, a grid-based fiber positioner with large patrol radius and minimized telecentric error
Aaron Omadutt, Roelof S. de Jong, Will Saunders et al. (+5 more)
In next-generation spectroscopic facilities, high-multiplex fiber positioning systems must operate within highly constrained focal surfaces, such as the Wide-Field Spectroscopic
Telescope (WST) requiring 30,000+ fibers across a 1.4-meter surface. The Fiber Location EXtender (FLEX) positioner meets these constraints by improving fiber patrol radii while minimizing telecentric error and positioner spacing for dense clustering and high Multi-Object Spectrograph (MOS) multiplexing. The patented FLEX concept utilizes a superelastic nickel-titanium
alloy (Nitinol) inside three concentric, geometrically altered tubes. This construction ensures the tip remains parallel with its base during tilting, while internal routing allows the fiber to run freely along the axis to minimize Focal Ratio Degradation (FRD). Designed for a patrol radius of 2.5x the pitch within the WST architecture, the design delivers a maximum patrol radius up to ~22.5 mm with a telecentric error of less than 0.39 degrees. FLEX utilizes three piezoelectric actuators to provide large radial displacements and precise focus adjustment. To scale this architecture, a modular focal surface layout of 90 identical curvilinear modules has been devised. This layout houses 30,240 positioners across a 2-degree hexagonal field-of-view (FoV), accommodating a central hole for an Integral Field pickoff mirror. Only three support struts are required, obscuring just 0.8% of the FoV while allowing full positioner coverage. One in 16 positioners is allocated for high-resolution spectroscopy, with the remainder split among three low-resolution spectrograph sets; all four sets achieve virtually full coverage of the FoV.
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All authors Aaron Omadutt, Roelof S. de Jong, Will Saunders, Joseph W. Barrow, Suryansh Saxena, Jon Lawrence, Thomas Liebner, Frank Dionies
Quantum Physics
Entanglement-entropy analysis of critical and topological quantum phases in a frustrated spin-1/2 Heisenberg ladder
Azadeh Ghannadan, Hana Vargová, Jozef Genzor et al. (+2 more)
We investigate the ground-state phase diagram of a frustrated
spin-1/2 Heisenberg ladder in the transverse
magnetic field with an anisotropic inter-rung exchange coupling $\alpha$. This bond-anisotropic parameter continuously interpolates among the Ising-like limit $\alpha=0$, the isotropic point $\alpha=1$, and the XY-dominated regime $\alpha \gg 1$. Using density-
matrix renormalization group calculations within a
matrix-product-state framework, we analyze bipartite
entanglement, magnetization, and
spin correlations to characterize the emergent
quantum phases. We identify six distinct ground-state phases, including rung-singlet, Haldane-like, Tomonaga-Luttinger
liquid, canted Ising-ordered, XY-polarized, and ordered
ferromagnetic states. While magnetization and local correlations provide a first insight into phase classifications, the finite-size scaling of the
entanglement measures offers a more sensitive and unified diagnostics of both gapped and gapless regimes. In the gapless regime, we extract the central charge $c \simeq 1$, confirming Tomonaga-Luttinger
liquid behavior, while at the transition between the canted Ising and
ferromagnetic phases, we observe $c \simeq 1/2$, consistent with the Ising universality. Finally, we find that both the Haldane-like behavior and the extended critical Tomonaga-Luttinger
liquid regime are strongly confined to the vicinity of the isotropic point $\alpha = 1$.
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All authors Azadeh Ghannadan, Hana Vargová, Jozef Genzor, Roman Krčmár, Andrej Gendiar
Quantum Physics
Assessing Cost Hamiltonian Reliability in Quantum Protein Structure Prediction
Mathieu Roget, Cedric Damour, Frederic Cadet et al. (+1 more)
In variational
quantum algorithms, QAOA, and
quantum annealing, the cost
Hamiltonian defines the optimization landscape explored by the
quantum hardware; however, in many application-driven formulations, this
Hamiltonian is a simplified proxy for the true task-level objective. Using
lattice-based
quantum protein structure prediction as a case study, we investigate whether the contact-energy cost
Hamiltonian commonly used in this setting is sufficiently aligned with structural accuracy, as measured by RMSD against experimentally determined structures. Through this specific problem, we show the importance of studying the reliability of the cost
Hamiltonian independently from the
quantum approach used. This work shows that, for small peptides and on average, the energy landscape of the considered cost
Hamiltonian is not correlated well enough to the actual error to provide meaningful predictions. Moreover, this correlation was estimated through Monte-Carlo sampling for larger instances. It shows an increase of said correlation for larger problem instances and when more interaction shells are considered. This investigation illustrates the meaningfulness of investigating cost
Hamiltonian relevance independently from the
quantum algorithm used.
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All authors Mathieu Roget, Cedric Damour, Frederic Cadet, Jingbo Wang
Computational Physics
Physics-Informed Neural Networks for coupled stiff transport systems
Laetitia Laguzet and Gabriel Turinici
Physics-Informed Neural Networks (PINN) struggle with stiff, regime-changing transport equations due to instability, loss imbalance, and violations of physical consistency. This paper investigates these failures through the Marshak wave equations, a canonical
benchmark from radiative transport, where initial and boundary conditions differ by up to 12 orders of magnitude, and proposes modifications to the standard PINN framework to overcome them. Three modifications are introduced: a ScaledSigmoid final activation enforcing physical bounds and positivity of the unknowns; a logarithmic MSE loss replacing the standard quadratic loss for initial and boundary conditions, enabling training across extreme scale disparities; and explicit enforcement of global conservation laws as an additional physics loss term. Monte Carlo sampling with exponential time weighting is used throughout. The proposed framework recovers the Marshak wave dynamics - including the hot, cold, and wave-front regions - in good agreement with a reference Implicit Monte Carlo solution (sub-millimeter absolute error on the front position, although the relative error remains substantial at early times), with run times under 5 minutes. Ablation studies confirm that each ingredient is essential: linear activation, absence of the logarithmic loss, or removal of the PDE term each independently cause the method to fail qualitatively. This work identifies and resolves three concrete failure modes of standard PINN on stiff
hyperbolic systems with nonlinear coupling. The combination of bounded activations, scale-aware loss functions, and conservation law enforcement constitutes a framework validated on the present one-dimensional Marshak wave problem, with potential extension to other coupled stiff transport systems in engineering.
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Soft Condensed Matter
Exotic topological defects and director fields in free-floating spherical ferroelectric nematic liquid crystal shells
Churchill B. Agoni, Ema Pilih, Luka Cmok et al. (+5 more)
Ferroelectric nematic (NF)
liquid crystals exhibit polar
symmetry and large polarization, giving rise to phenomena absent in conventional apolar nematics. We investigate NF
liquid crystals confined to free-floating spherical shells with tangential boundary conditions, enforcing a total topological defect charge of +2. We
conjecture that ferroelectric nematics avoid splayed configurations with half-integer defects, common in apolar nematic shells, instead concentrating the topological charge into escaped azimuthal +1 defects requiring only bend and twist. Indeed, at room temperature in the NF phase, our thin RM734+DIO shells with inner and outer aqueous poly(vinyl alcohol) solutions develop an azimuthal director field around two antipodal +1 bend-twist defects. The non-centrosymmetric nature and the azimuthal director configuration of the shells in the NF phase are confirmed also through second-harmonic generation microscopy. At intermediate temperature the antiferroelectric Nx phase generates a new exotic texture rife in zigzag lines in the shells. In the regular N phase at high temperature, the shells develop the usual four +1/2 disclinations located near the thinnest point. Our study highlights the rich platform offered by spherical shells to study the behavior of exotic
liquid crystals subject to topological constraints, possibly opening new paths to apply the highly responsive ferroelectric nematic phase
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All authors Churchill B. Agoni, Ema Pilih, Luka Cmok, Calum J. Gibb, Jordan Hobbs, Richard Mandle, Irena Drevensek-Olenik, Jan P.F. Lagerwall
Mesoscale and Nanoscale Physics
In-plane and out-of-plane magnetic field driven Josephson diode effect in magic-angle twisted four-layer graphene
Marta Perego, Sayan Banerjee, Mohamad Abu El Hija et al. (+8 more)
The superconducting diode effect offers a powerful probe into the fundamental
symmetries of
quantum materials. Recent studies on twisted
graphene diodes have predominantly focused on
bilayer or trilayer systems under out-of-plane
magnetic fields. Here, we demonstrate both out-of-plane and in-plane driven Josephson diode effects in a magic-angle twisted four-layer
graphene junction, i.e., an even number of layers. We observe the emergence of a diode effect at zero out-of-plane field, tuned by an increasing in-plane
magnetic field. This result points to the presence of strong in-plane orbital coupling, which is highly sensitive to the specific layer parity of the structure. Our findings provide experimental insights into the
symmetry-breaking mechanisms of even-layer twisted
graphene, establishing in-plane
magnetic fields as a vital tool for unravelling their microscopic properties.
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All authors Marta Perego, Sayan Banerjee, Mohamad Abu El Hija, Clara Galante Agero, Alexandra Mestre-Torà, Giovanni Zhang, Takashi Taniguchi, Kenji Watanabe, Mathias S. Scheurer, Thomas Ihn, Klaus Ensslin
Quantum Physics
Synchronization in the quantum regime
Finn Schmolke and Eric Lutz
Can synchronization – the widespread spontaneous emergence of coordinated dynamics in classical nonlinear systems – also occur in the
quantum regime? This question has recently sparked intense research into collective behavior and temporal self-organization in
quantum systems. Typical
quantum features such as the linearity of time
evolution and the presence of
quantum noise seem to hinder the appearance of synchrony at the microscopic level. At the same time,
quantum coherence and
quantum correlations may provide novel mechanisms for enhancing synchronization beyond its classical counterpart. We here survey recent theoretical and experimental advances in
quantum synchronization, ranging from the characterization of synchronous oscillations and genuinely nonclassical forms of synchrony to many-body synchronization on
quantum networks.
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Soft Condensed Matter
Thermoresponsive self-oscillating hydrogel: spatially lumped model, relaxation dynamics and mechanical output
Yunjie Wang, Ling Yuan, Yang Li et al. (+5 more)
Thermoresponsive gels with a lower critical solution temperature (LCST) can undergo self-oscillation driven by a thermal flux through repeated cycles of positive feedback, driven by heating-induced collapse, and negative feedback, characterized by deformation recovery due to collapse-induced suppression of heating and heat dissipation to the environment. In order to explore the detailed bifurcation structure of a thermosensitive self-oscillating gel and understand its mechanical output of peristaltic motion and net displacement, we develop a minimal spatially lumped two-variable phenomenological model whose
equilibrium parameters are constrained by poly(N-isopropylacrylamide) (PNIPAAm) swelling data. A supercritical
Hopf bifurcation creates stable small-amplitude oscillations near a fold of the swollen
manifold, and canard-mediated growth transforms this branch into relaxation oscillations. Singular analysis relates the amplitude to fast jumps and the period to drift along slow
manifolds, while continuation separates the
Hopf boundary from the maximal-canard locus. For the representative maximum-power relaxation cycle considered here, the loaded model predicts greater work than a harmonic volume trajectory with the same stroke, period, and viscous load, with output concentrated in the fast collapse and re-swelling transitions. The net displacement during peristaltic locomotion of the thermoresponsive self-oscillating gel results from the work difference between collapse and re-swelling. These results provide a theoretical basis for designing autonomous thermoresponsive self-oscillating gel actuators whose oscillatory waveform and power output can be controlled through thermal feedback and mechanical loading.
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All authors Yunjie Wang, Ling Yuan, Yang Li, Lin Ren, Yuhan Wang, Xiaol Lv, Irving R Epstein, Qingyu Gao
Plasma Physics
Effect of Noise on Spatio-Temporal Evolution of Current Filamentation Instability in Relativistic Beam-Plasma Systems
Thulasidharan K and Vishwa Bandhu Pathak
The spatio-temporal
evolution of the current filamentation instability in a relativistic beam–
plasma system is studied analytically and with two-dimensional particle-in-
cell simulations. A partial differential equation for the transverse vector potential is derived for a sharp-front relativistic beam entering cold, unmagnetized
plasma, including a second-order spatial derivative term that governs the spatial growth near the beam front. The equation is solved analytically for constant, linearly growing, and oscillatory initial noise when this term is neglected, and numerically when it is included, as no closed-form solution then exists. For constant initial noise, the numerical solution reproduces the simulated
magnetic-field structure, unlike the analytical solution without the term. This shows that the longitudinal field modulation is intrinsic to the instability, present even for a noise with constant amplitudes. The noise profile as well can influence the spatial-temporal
evolution of the instability, which we discuss further considering linearly growing and oscillatory noise. The field grows spatially behind the beam front and saturates at a length $L_{\mathrm{sat}}\propto(v_{0b}+2)v_{0b}/\gamma_{0b}^{3}$, where $v_{0b}$ and $\gamma_{0b}$ are the beam velocity and Lorentz factor, beyond which growth is purely temporal. The saturation length increases linearly in time at a constant rate $\mathrm{d}L_{\mathrm{sat}}/\mathrm{d}\tau\approx0.42\,c$, matching the analytical estimate. The temporal growth rate remains unchanged, so the term modifies the spatial transport of the instability rather than its local amplification. For beam velocities above $0.6c$, the model deviates from the simulations as oblique modes and nonlinear filament dynamics outside the single-mode treatment become important.
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Mesoscale and Nanoscale Physics
Bose-Einstein Condensation of Three-Dimensional Exciton-Polaritons
Junhui Cao and Alexey Kavokin
We develop a band-structure-based theory of
exciton-polaritons in a three-dimensional inverse-opal photonic
crystal doped with
semiconductor quantum dots. Starting from a
symmetry-selected bright photonic branch near the photonic gap edge, we construct an
exciton-
photon Hamiltonian and obtain a lower-polariton band with a W-point global minimum and a nearby X-point van-Hove-enhanced density of states. We show that the W valleys determine the
equilibrium Bose-Einstein condensation threshold, while the X-point saddle provides a finite excited-state capacity that renormalizes the critical temperature when the W-X offset is thermally accessible. By tuning the
exciton resonance and the light-matter coupling, the relative W-X ordering can be reconstructed, leading to a strong variation of the critical temperature. We further formulate a momentum-resolved Boltzmann model for driven-dissipative kinetics. Under non-resonant pumping, reservoir feeding, radiative decay, and inter-sector relaxation can produce either W-dominated condensation, a mixed W-X regime, or an X-dominated nonequilibrium coherent state. Our results establish three-dimensional photonic-
crystal polaritons as a platform where condensation is controlled not only by the band minimum but also by valley geometry, van-Hove-enhanced phase space, and relaxation pathways.
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