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Physics

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Wednesday 22 July

Materials Science

Thickness-dependent crack suppression and wrinkle formation in freestanding BaTiO3 membranes

Rajesh Mandal, Ajay Kumar and Nini Pryds

Freestanding ferroelectric oxide membranes offer a promising route toward silicon-integrated low-power electronic and memory devices, but reproducible membrane quality remains challenging, particularly in ultrathin BaTiO3 (BTO), where cracking and wrinkling hinder integration. Here, we show that crack and wrinkle formation in released BaTiO3 membranes can be tuned by jointly controlling oxide thickness and polymer support thickness. Reducing the BaTiO3 thickness from 15 nm to 5 nm suppresses large-area, optically visible cracking across the analysed regions, but promotes dense nanoscale wrinkling, revealing a trade-off between fracture mitigation and morphological instability. In 10 nm BaTiO3 membranes, polymer support thickness further modulates wrinkling, with an intermediate thickness reducing wrinkle density. Piezoresponse force microscopy reveals time-dependent evolution of written contrast after release, indicating that apparent ferroelectric response is influenced by polarization switching, post-release morphology, interfacial contact, charge screening, and strain relaxation. These results establish processing guidelines for integrating freestanding ferroelectrics into future devices.
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Optics

Three-dimensional field of view of remote focusing microscopy system

Dinesh Saini and Manish Kumar

Remote focusing (RF) microscopy is well known for its ability to sharply image a wide range of planes away from the working distance of the microscope objective. However, the exact nature of the three-dimensional (3D) field of view (FOV) is not known. In this letter we report an optical ray tracing based FOV study of a remote focusing microscopy system. We numerically simulate the Strehl ratio of two configurations of the remote focusing systems, and use this for the evaluation of the 3D FOV. The FOV tapers down as the sample plane moves away from the working distance. To cross-verify our simulation results, we experimentally measured the FOV at various offset planes. This rate of taper depends on the numerical aperture. We also discuss the advantages and limitations of remote focusing in microscopy.
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Solar and Stellar Astrophysics

Height Dependent Phase Shifts of Wave Pulses in the Lower Solar Atmosphere Measured with SUNRISE III

Andreas Lagg, H. N. Smitha, Sami K. Solanki et al. (+32 more)

We report on the measurement of the height-dependent time shifts of wave pulses in the lower solar atmosphere from high-resolution spectro-polarimetric observations obtained with the SUSI instrument on board the SUNRISE III balloon-borne solar observatory during its successful science flight in July 2024. The line-of-sight velocities derived from the line-core positions of 19 spectral lines in a 2 nm-wide window around the Ca II H line were used to determine the time shifts of propagating pulses at their respective formation heights. Our analysis reveals that these shifts are roughly ordered according to the computed formation heights of the respective spectral lines. A statistical analysis of the time shifts using sit-and-stare observations with a total duration of one hour reveals that wave pulses propagating upwards from near the solar surface to heights of approximately 500-700 km are most common, with average time lags of 20 s to 30 s between these heights. Also present are pulses with close-to-zero phase shifts, predominantly above intergranular lanes and areas of enhanced magnetic activity. Additionally, downward propagating wave pulses with negative time lags of 10 s to 15 s are seen, mostly above areas of enhanced magnetic activity. A common feature of all the observed pulses is that in the lower 250 km they show small time lags of zero to a few seconds, and only at higher layers do the propagating pulses become more dominant. This study demonstrates the potential of the many-line approach for investigating the height dependence of the physical conditions in the solar atmosphere.
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All authors Andreas Lagg, H. N. Smitha, Sami K. Solanki, Tino L. Riethmüller, Achim Gandorfer, Alex Feller, Francisco A. Iglesias, Azaymi L. Siu-Tapia, Jose Carlos del Toro Iniesta, Yukio Katsukawa, Pietro Bernasconi, Thomas Berkefeld, Masahito Kubo, David Orozco Suárez, Robert Cameron, Jesper Schou, Damien Przybylski, Alberto Álvarez-Herrero, Bianca Grauf, Michael Carpenter, Alexander Bell, Valentín Martínez Pillet, Shahin Jafarzadeh, Lakshmi Pradeep Chitta, Francisco Javier Bailén, Julian Blanco Rodríguez, Juan Sebastián Castellanos Durán, Edvarda Harnes, Johannes Hölken, Ryohtaroh T. Ishikawa, Yusuke Kawabata, Takuma Matsumoto, Takayoshi Oba, Hanna Strecker, Dušan Vukadinović

Quantum Physics

PN-QNN: Harnessing Physical Noise as a Native Regularizer in Photonic Hybrid Quantum Neural Networks

Farah Elnakhal, Alberto Marchisio, Nouhaila Innan et al. (+2 more)

Physical noise in near-term quantum hardware is usually treated as a nuisance to suppress. We ask whether it can instead act as a hardware-native regularizer for photonic hybrid quantum-classical neural networks (PHQCNNs), analogous to noise-injection regularization in classical deep learning. Using Quandela's Perceval simulator and the MerLin framework, we build PHQCNNs for Iris, Digits, and MNIST and inject Perceval's seven-parameter physical noise model directly into training. A genetic algorithm searches the six continuous noise dimensions and 1 boolean parameter to find, per dataset, the configuration maximizing validation accuracy, compared against a noiseless baseline across five seeds. GA-tuned noise yields modest accuracy gains on Iris (+0.82pp) and Digits (+1.45pp), but a clear degradation on MNIST (-1.21pp). Per-parameter sweeps show that no individual noise parameter is consistently beneficial, motivating the joint search, while a second-order loss expansion shows that physical noise induces a Tikhonov-like regularization term whose effect is dataset-dependent. Physical photonic noise can thus act as a free regularizer, but not universally.
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All authors Farah Elnakhal, Alberto Marchisio, Nouhaila Innan, Gabriel Falcao, Muhammad Shafique

Mathematical Physics · Cross-listed from math.QA

The quantum loop algebra of $sl_2$ and $q$-Racah type bivariate functions

Pascal Baseilhac and Nicolas Crampe

A unified algebraic framework for two different six-parameter families of bivariate $q$-Racah type functions is given using the representation theory of the quantum loop algebra $\mathcal{L} U_q sl_2$ of $sl_2$. The starting point of the analysis is two left and right coideal subalgebras of $\mathcal{L} U_q sl_2$ and six commutative subalgebras, built from eight elements in $\mathcal{L} U_q sl_2 \otimes \mathcal{L} U_q sl_2$. The eight elements depend on two scalars $a,b \in {\mathbb C}^*$, and are diagonalized on a finite-dimensional vector space. The bivariate $q$-Racah type functions are interpreted as the overlap coefficients relating six `distinguished' eigenbases parametrized by $a,b$ of the tensor product (evaluation) representations of $\mathcal{L} U_q sl_2$ labeled by the evaluation parameters $u_1,u_2$. Upon certain conditions on $a,b,u_1,u_2$, it is shown that a subset of pairs of elements act as tridiagonal pairs of type I (also called $q$-Racah type). For $u_1/u_2=1$, another subset of pairs of elements are conjectured to act as factorized Leonard pairs. Thus, in both cases corresponding overlap coefficients relating the various eigenbases associated with different pairs are obtained. Some of their properties are also discussed, as well as their relation with known bivariate polynomials of Tratnik type and the rank 2 Askey–Wilson algebra.
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Quantum Physics

Slack-Free Deep-Unfolded Combinatorial Optimization Solver for Inequality Constraints

Ryo Hagiwara, Shunta Arai and Satoshi Takabe

Quantum annealing (QA) is used to solve combinatorial optimization problems (COPs). When COPs are implemented on quantum annealers, they are typically encoded as quadratic unconstrained binary optimization (QUBO) problems, but constraint encodings often increase the number of qubits and the embedding overhead. This issue is particularly important for COPs with inequality constraints, where standard slack-variable formulations introduce additional binary variables. Unbalanced penalization (UP) avoids slack variables, but the original UP formulation requires tuning two penalty coefficients and contains a squared residual term that can increase the number of quadratic couplings. In this paper, we propose the unbalanced penalization Ohzeki method (UPOM), which combines UP with the Ohzeki method for inequality-constrained COPs. UPOM replaces the two static penalty coefficients of original UP with an auxiliary-variable update and removes the squared residual term from the Hamiltonian used for sampling. We further propose the deep-unfolded unbalanced penalization Ohzeki method (DU-UPOM), which learns the step-size schedule of the UPOM update from training instances. Numerical experiments on random knapsack problems show that UPOM improves over original UP and that DU-UPOM reaches optimal solutions in fewer iterations than fixed-step UPOM and other baseline. These results demonstrate that the proposed framework reduces the tuning and embedding burdens of UP while making the Ohzeki method trainable for inequality constraints.
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Materials Science

Exploring Multifunctionality in MgO-Based Magnetic Tunnel Junctions with Coexisting Magnetoresistance and Memristive Properties

Alejandro Schulman, Elvira Paz, Tim Böhnert et al. (+2 more)

Magnetic tunnel junctions (MTJs) and memristors are two key emerging nanotechnologies that attracted significant interest for potential applications at the forefront of the digital revolution, including sensing, data storage, and non-conventional computation. The co-integration of these phenomena into a single multifunctional device is an important step toward harnessing the re-programmability of memristive systems with the high yield and varied functionality of MTJs. This study demonstrates the co-existence of magnetoresistance and memristive properties on MgO-based MTJs. These devices show a magnetoresistance with a linear response as a function of a magnetic field and no hysteresis, which are the requirements for good magnetic field sensors, as well as demonstrating a non-volatile and quasi-analogue memristive behavior as a function of an applied electrical field down to nanosecond pulses. Furthermore, by doping the oxide barrier, the memristive power consumption is lowered by 20% giving the multi-functionality of the devices a promising scalability potential. This study also shows that, memristive switching can be reversibly used to completely suppress and recover the spintronic functionalities. These results can pave the way for a seamless co-integration of memristors and spintronic devices in complex reprogrammable circuits addressing applications such as reprogrammable multifunctional field sensor arrays and neuromorphic computing.
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All authors Alejandro Schulman, Elvira Paz, Tim Böhnert, Alex Steven Jenkins, Ricardo Ferreira

Earth and Planetary Astrophysics

A comprehensive study of comet 67P/Churyumov-Gerasimenko in the 2021/2022 apparition. II. Colorimetry, polarimetry, modeling

Vera Rosenbush, Oleksandra Ivanova, Johannes Markkanen et al. (+5 more)

This paper presents the second part of our multi-technique observational study of comet 67P during its 2021-2022 apparition. While the first paper focused on photometry and spectroscopy, here we investigate the dust color and linear polarization of the coma. Imaging in the g-sdss and r-sdss filters was obtained with the 6-m BTA SAO Telescope, and aperture polarimetry was performed with the 2.6-m Shajn Telescope (CrAO) and the 2-m RCC Telescope. Observations at phase angles of 47.9 deg (6 October 2021) and 10.5 deg (6 February 2022) show negative polarization of about 0.5-2.5% at 10.5 deg and positive polarization of about 11% at 47.9 deg. The dust color was red, reaching about 0.8 mag near the nucleus and in the tail, and decreasing to about 0.2 mag in the coma and jet within 20,000 km of the nucleus. Spatial maps reveal a gradual decrease in color index and a corresponding increase in polarization with distance from the nucleus. Numerical modeling using ballistic particle-cluster aggregates composed of equal fractions of silicates and organics indicates that the coma is dominated by particles larger than 10 micrometers, while local polarization enhancements are consistent with regions containing smaller (1-10 micrometer) grains. Combining our aperture measurements with published data from four previous apparitions confirms that comet 67P belongs to the high-polarization class. The unusually high positive polarization observed during the 2021/22 apparition, together with the relatively isotropic coma morphology, suggests that the dust properties may have changed after the 2015/16 apparition.
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All authors Vera Rosenbush, Oleksandra Ivanova, Johannes Markkanen, Igor Lukyanyk, Valerii Kleshchonok, Ludmilla Kolokolova, Colin Snodgrass, Elena Shablovinskaya

Medical Physics

COBRA2026: a large-scale multicenter pelvic cone-beam computed tomography projection dataset

Adrian Thummerer, Simon Rit, Florian Kamp et al. (+11 more)

The COBRA2026 dataset is a large-scale, multicenter resource of raw radiotherapy cone-beam computed tomography (CBCT) acquisitions created for the development and evaluation of conventional and learning-based reconstruction and image-correction methods. It contains data from 867 patients undergoing pelvic radiotherapy at six European centers, acquired using Elekta and Varian imaging systems. For each case, the dataset includes raw projection data, acquisition geometry, calibration and correction information, clinically reconstructed CBCT images, and corresponding planning CT images. Vendor-specific files were anonymized and converted into open formats. Planning CT images were deformably registered to the daily CBCT anatomy, and matched projections were simulated using the corresponding acquisition geometry. All cases underwent visual quality control, and cases with substantial processing or registration errors were excluded. The approximately 950 GB dataset is divided into training, validation, and test sets containing 692, 52, and 123 cases, respectively. Projection stacks and volumetric images are provided as compressed MetaImage files, with geometry and metadata supplied in XML and YAML formats. COBRA2026 supports research on full- and sparse-view reconstruction, low-dose imaging, artifact and scatter correction, motion compensation, and synthetic CT generation. The dataset is released under the CC BY-NC 4.0 license, indexed on Zenodo (doi:10.5281/zenodo.21322350), and accompanied by openly available preprocessing and baseline reconstruction code. It also forms the basis of the COBRA2026 reconstruction challenge.
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All authors Adrian Thummerer, Simon Rit, Florian Kamp, Matteo Maspero, Martjin P.W. Intven, Thomas G. Boné, Christopher Kurz, Guillaume Landry, Thomas Baudier, Mustafa Kadhim, Julius Arnold, Michael Rauter, Barbara Knäusl, Lukas Zimmermann

Disordered Systems and Neural Networks

Vanishing spin stiffness in weakly disordered two-dimensional Heisenberg ferromagnets

Jacopo Niedda, Aldo Coraggio, Giacomo Bracci-Testasecca et al. (+1 more)

We show that a small fraction of antiferromagnetic bonds qualitatively alters the long-wavelength dynamics of two-dimensional Heisenberg ferromagnets. Although the classical ground state remains magnetized, weak bond frustration generates logarithmically correlated spatial fluctuations of the local spin stiffness, despite the microscopic disorder being short ranged. A replica field theory calculation shows that the effective disorder strength grows under coarse graining, while the spin stiffness decreases, yielding anomalously soft magnons with a scale-dependent dynamical exponent $z > 2$. Numerical diagonalization of the semiclassical spin-wave Hamiltonian confirms the anomalous low-energy scaling. The flow is toward an infinite-disorder, zero stiffness regime.
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All authors Jacopo Niedda, Aldo Coraggio, Giacomo Bracci-Testasecca, Antonello Scardicchio

Statistical Mechanics

Motility destabilizes an absorbing-state flock

Narayan Dutt Sharma, Subroto Mukerjee, Chandan Dasgupta et al. (+1 more)

Activity, when it takes the form of motility, is generally seen to promote order in many-body systems. Here we present a one-dimensional lattice model that, in the non-motile limit, exhibits absorbing ferromagnetic states. When activity is introduced through biased motility, these absorbing state are destabilised and the system instead undergoes a transition from an ordered flock to a disordered state as the alignment strength is decreased. A finite-size scaling analysis of physical quantities reveals a continuous transition with critical exponents satisfying the hyperscaling relation in one dimension, providing quantitative evidence for the activity-induced disorder.
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All authors Narayan Dutt Sharma, Subroto Mukerjee, Chandan Dasgupta, Sriram Ramaswamy

Materials Science

Huge hole injection in tungsten dichalcogenide heterostructures without electric gating: a DFT study

Dawid Ciszewski and Wojciech Grochala

Van der Waals heterostructures based on transition metal dichalcogenides, TMDs, provide a versatile platform for tailoring electronic properties through interlayer charge transfer, CT. Precise control of CT is essential because it directly determines the electronic structure and carrier concentration in atomically thin materials. Recently, the concept of a chemical capacitor has been proposed as a route to achieving exceptionally high carrier densities through CT across insulating separator layers. Here, we extend this concept to van der Waals heterostructures by investigating TMD hBN OX, oxidizer, systems using density functional theory, DFT. Following the screening of candidate TMDs and electron acceptors, XeF2 and KrF2 were identified as suitable acceptors exhibiting type III broken gap band alignment with WS2 and WSe2, respectively. Periodic DFT calculations of large supercells reveal CT corresponding to hole concentrations of up to 0.23 h+ and 0.35 h+ per W atom in WS2 hBN XeF2 and WSe2 hBN KrF2 heterostructures, respectively. The resulting charge redistribution demonstrates that noble gas fluorides provide an efficient route for noncontact engineering of carrier density in TMD heterostructures, offering a new strategy for tuning correlated electronic phases in two dimensional materials.
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Strongly Correlated Electrons

How to measure loop currents in scanning tunneling microscopy

Victoire Morisseau, Luke C. Rhodes, Peter Wahl et al. (+1 more)

The emergence of loop current phases, where spontaneous loops of orbital currents give rise to a weak local magnetic moments, has been proposed to exist in a number of quantum materials based on measurements that pick up weak signatures of time reversal symmetry breaking or small magnetic moment order. The most prominent example is as an explanation of the pseudogap phase on the underdoped side of the phase diagram of the high-temperature cuprate superconductors, but more recently, it has been proposed to occur in Kagome materials and at the surface layer of Sr$_2$RuO$_4$. Experimental results have, however, been inconclusive so far, some detecting signatures that can be understood as emerging due to loop current phases, whilst others have not detected any significant proof. One of the techniques that should be able to pick up local signatures of loop current orders is low temperature scanning tunneling microscopy and spectroscopy (STM/STS), however firm predictions of how to detect them are missing. Here, we provide specific predictions for how loop current orders in a square lattice can be seen in spectroscopic maps, using models of the cuprate high-temperature superconductors and of the surface layer of Sr$_2$RuO$_4$. We find that, besides lifting degeneracies at the specific ordering vector of the loop current order, a finite spin polarisation emerges when spin-orbit coupling is present, signatures of which can be detected in spin-polarised STM.
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All authors Victoire Morisseau, Luke C. Rhodes, Peter Wahl, Carolina A. Marques

Fluid Dynamics

Discrete Boltzmann model at Burnett level for compressible multicomponent flows under external forces

Demei Li, Huilin Lai, Chuandong Lin et al. (+1 more)

This work extends the Burnett-level discrete Boltzmann model (DBM) from single-component to multicomponent compressible flows under external forces, building on the fundamental framework of the high-precision discrete kinetic method. A high-isotropy 25-discrete-velocity set is adopted to guarantee numerical stability and spatial symmetry, while a rigorous moment-matching strategy is developed to construct the equilibrium distribution function and external force term. Different from the single-component counterpart, the present model intrinsically incorporates interspecies mass diffusion effects and multi-component thermodynamic nonequilibrium behaviors, which are critical for complex compressible multicomponent systems. The Chapman–Enskog expansion verifies that the proposed model can exactly recover the Burnett-level governing equations for forced multicomponent compressible flows in the continuum limit. Five canonical benchmark cases, including multicomponent mass diffusion, compressible Sod shock tube, thermal Couette flow, Kelvin–Helmholtz instability, and Rayleigh–Taylor instability, are systematically performed. Numerical results demonstrate that the developed Burnett-level multicomponent DBM achieves high accuracy and robustness in capturing both hydrodynamic evolution and multicomponent nonequilibrium characteristics under external forces.
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All authors Demei Li, Huilin Lai, Chuandong Lin, Suni Chen

Nuclear Theory

Stability of intruder-driven quadrupole and hexadecapole deformation effects in Xenon, Barium, Cerium and Neodymium isotopes

K. Ziyatkhan, R. Rodríguez-Guzmán and L. M. Robledo

Two-dimensional Generator Coordinate Method calculations for the axial quadrupole $\beta_{2}$ and hexadecapole $\beta_{4}$ collective deformations are carried out with the Gogny force in a series of Xe, Ba, Ce and Nd isotopes with neutron numbers covering both magic neutron shell closures N=82 and N=126. The underlying mean-field configurations are used to characterize the expected dynamic behavior of the system. Two regions of strong coupling between the quadrupole and hexadecapole degrees of freedom are found and characterized. Quantum fluctuations soften the mean-field ground state values of $\beta_{2}$ and $\beta_{4}$ in transitional regions. The ground state correlation energy coming from $\beta_{4}$ is comparable in size to the one coming from $\beta_{2}$, and both together amount to a sizable 1.5 MeV. Shape coexistence in some isotopes and its impact in the excitation energy of the first excited state is analysed. Finally, the role of a second intruder orbital in the explanation of the large deformation parameters of some nuclei in the region is discussed.
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Chemical Physics

Investigating aqueous mineral interfaces using sum frequency generation spectroscopy

Moritz Zelenka and Ellen H.G. Backus

Sum frequency generation spectroscopy can be utilized to address the challenge of studying solid-liquid interfaces under ambient pressure and with macroscopic amounts of liquid, while still retrieving molecular level information. By utilizing a non-linear optical process, this method allows to selectively measure vibrations of interfacial species. Within this chapter sum frequency generation spectroscopy is first briefly introduced and then comprehensively evaluated as an investigative tool for solid-liquid interfaces, with mineral-water interfaces as model system. Additionally, it is explained how the actual probing depth of this method depends on both the experimental setup and the properties of the investigated system, such as surface charges.
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Astrophysics of Galaxies

Anharmonic Infrared Emission of Cyano-Substituted Polycyclic Aromatic Hydrocarbon Molecules: Cyanonaphthalenes as a Case Study

Tao Chen, Kaijun Li and Aigen Li

Recent detections of cyano-substituted polycyclic aromatic hydrocarbons (cyano-PAHs) highlight them as key tracers of nitrogen heterocycles in the interstellar medium (ISM). However, their infrared (IR) identification requires anharmonic vibrational radiative models that account for dynamic cooling across diverse environments. We provide IR cascade emission spectra for neutral, cationic, and anionic 1- and 2-cyanonaphthalene (1- and 2-CNN) under representative astrophysical conditions, investigating how charge states and substitution positions modulate anharmonic profiles and energy redistribution during IR cascades. Using B3LYP/N07D with Second-order Vibrational Perturbation Theory (VPT2), we computed anharmonic properties and applied an optimized microcanonical sampling algorithm to calculate vibrational density of states and model environment-dependent cascade spectra. Results show that charge states strongly tune the CN nitrile band: anion intensity is enhanced by an order of magnitude compared to neutrals, whereas cation intensity is slightly weaker. 1- and 2-CNN present distinct isomeric signatures: 1-CNN displays a complex "red-wing" structure in the 3.3-micron C-H stretch due to peri-hydrogen interactions, whereas 2-CNN yields a more symmetric profile. We evaluated the fractional energy emitted via the CN stretch relative to total cascade emissivity across charge states and environments. Combined with observed CN fluxes, these fractions provide a quantitative tool to constrain cyano-PAH abundances. By bridging laboratory benchmarks with dynamic interstellar emission, this work delivers accurate anharmonic fingerprints to guide JWST observational analysis.
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Astrophysics of Galaxies

LMC-induced Perturbations in the Milky Way Halo II: Bridging Field-level Inference and Summary-level Simulation-Based Inference

Yanjun Sheng, Yuan-Sen Ting, Tomasz Różański et al. (+3 more)

The gravitational interaction between the Milky Way (MW) and the Large Magellanic Cloud (LMC) drives the outer halo into dynamical disequilibrium, imprinting the masses and structural parameters of both galaxies onto the 6D phase-space distribution of halo tracers. This signal has been characterised with summary statistics ranging from low-order velocity moments to basis function expansions, yet how much information these summaries discard, and whether they are complementary, remains unclear. We address these questions by comparing a likelihood of the halo phase-space distribution (field-level) with physically interpretable summaries for constraining $(M_{\mathrm{MW}}, M_{\mathrm{LMC}}, c, q)$, where $c$ and $q$ are the MW halo concentration and flattening. A Conditional Flow Matching (CFM) model trained on the HaloDance $N$-body suite provides an exact likelihood at a held-out fiducial point; for 5,000 tracers in $30$–$120$~kpc it tightens marginal constraints by factors of $2.5$–$9.9$ over an all-sky velocity-moment forecast. To narrow this gap, we construct four parameter-sensitive summaries via BFE+MOPED that capture the angular structure of the halo density and velocity and contain information complementary to the velocity moments. Combining the two sets of summaries tightens the marginal constraints by up to $15$ per cent relative to the angular summaries alone, and by $30$–$71$ per cent relative to the velocity moments alone, although the resulting constraints remain $1.3$–$2.9$ times broader than those from the full phase-space benchmark. We thus establish a physically interpretable summary-level route for applying this inference pipeline to future observations, while the field-level benchmark measures the information available for further improvement.
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All authors Yanjun Sheng, Yuan-Sen Ting, Tomasz Różański, Xiang-Xiang Xue, Roland M. Crocker, Jiashu Pan

Optics

Dirac-vortex modes beyond the continuum limit

Jiayu Fan, Jiusi Yu, Aoning Luo et al. (+7 more)

Dirac-vortex modes (DVMs) in Kekule-modulated lattices provide a topological route to wave confinement and are commonly described by the continuum Jackiw-Rossi model, in which the initial phase acts as a redundant gauge degree of freedom and does not affect observables of the mode. Here we show that this picture breaks down in discrete lattices when the complex mass texture that induces the DVMs no longer satisfies the slowly varying envelope approximation. In this regime, lattice discreteness turns the initial phase into a physically observable parameter that shifts the DVM center. By further introducing a sublattice-antisymmetric perturbation, we convert this phase-dependent center motion into a continuous spectral response of the DVM, enabling its frequency tuning across nearly the entire topological bandgap. Our simulation and experimental results agree well with a revised continuum model accounting for the mode-center motion. Within this perturbative framework, the model shows that the frequency shift exhibits a sinusoidal-like dependence on the initial phase. These findings reveal initial phase-sensitivity of the DVMs realized in lattices, an important and basic feature absent from the ideal continuum Jackiw-Rossi model, and demonstrate initial phase engineering as a potential pathway towards reconfigurable photonic devices.
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All authors Jiayu Fan, Jiusi Yu, Aoning Luo, Yiyi Yao, Shijie Kang, Xiexuan Zhang, Haitao Li, Biye Xie, Xiao-Dong Chen, Xiaoxiao Wu

Mesoscale and Nanoscale Physics

Spin-wave softening across the uniform-to-stripe domain transition in iron garnet film

Titiksha Srivastava, Victor Leroy, Nessrine Benaziz et al. (+6 more)

Spin-wave spectra across transitions between uniform and textured phases can offer deep insight into both symmetry-breaking physics and self-assembled magnonic bands. However, experiments require a material platform that combines low damping, well-defined textures, and spectroscopic access. Here, we study a Bi-doped iron-garnet film with perpendicular magnetic anisotropy (PMA), which undergoes a uniform-to-stripe-domain transition as a function of in-plane magnetic field. Real-space imaging by magnetic force microscopy reveals field-reorientable stripe domains aligned with the in-plane field, while reciprocal-space measurements using thermal microfocused Brillouin light scattering ($\mu$-BLS) reveal the softening of a low-frequency spin-wave branch near the transition and the appearance of additional modes in the stripe-domain state. Calculated dispersion relations identify finite-$k$ softening in the Damon-Eshbach geometry ($k \perp M$), with the corresponding wavelength matching the stripe periodicity at the transition. In addition, a $\mu$-BLS spectral model reproduces the measured mode frequencies and relative intensities at selected fixed fields. Micromagnetic simulations capture the field-driven formation of the stripe state and reproduce the experimental thermal $\mu$-BLS spectra. Our findings establish BiYIG with PMA as a model low-damping platform for studying spin-wave freezing, stripe-domain modes, and reconfigurable magnonic band structures.
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All authors Titiksha Srivastava, Victor Leroy, Nessrine Benaziz, Nathaniel Findling, Ludovic Largeau, Jamal Ben Youssef, Jean-Paul Adam, Thibaut Devolder, Joo-Von Kim

Accelerator Physics

Exploiting Non Redundant Aperture Interferometry as a Diagnostics Tool for Synchrotron Light Characterization

C. Carilli, U. Iriso, B. Nikolic et al. (+2 more)

We recently introduced a novel interferometric method inspired by radio astronomy, utilizing a Non-Redundant Aperture (NRA) mask with self-calibration to fully characterize the two-dimensional transverse shape of electron beams from a single-shot interferogram. This paper reports the latest advancements in this technique, including a new data analysis approach based on closure amplitudes, which removes the need for self-calibration. We also demonstrate the method's applicability to wavefront sensing, and we explore its potential for resolving beam halos superimposed on well-defined Gaussian beam core.
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All authors C. Carilli, U. Iriso, B. Nikolic, N. Thyagarajan, L. Torino

Astrophysics of Galaxies

The UK Infrared Telescope M33 monitoring project. VI. Feedback from dusty stellar winds across the galactic disc

Atefeh Javadi, Jacco Th. van Loon, Mina Alizadeh et al. (+2 more)

We have conducted a near-infrared monitoring campaign at the UK InfraRed Telescope (UKIRT), of the Local Group spiral galaxy M33 (Triangulum). In this sixth paper of the series, we measure the dust and gas mass-loss rates by the pulsating Asymptotic Giant Branch (AGB) stars and red supergiants (RSGs) across the stellar disc of M33. We combined our time-averaged near-IR photometry with the multi-epoch mid-IR photometry obtained with the Spitzer Space Telescope, and employed a combination of spectral energy distribution modelling and scaling relations. We found that the mass-loss rate is approximately proportional to luminosity (birth mass), with additional weaker dependence on pulsation period and/or amplitude (reflecting stellar evolution). As a population, AGB stars contribute most to the mass return into the interstellar medium (ISM). Super-AGB stars also reach very high mass-loss rates, in excess of $10^{-4}$ M$_\odot$ yr$^{-1}$. The mass loss of RSGs appears to be subject to different modes, with rates well below, around, and well above the nuclear burning timescale. The timescale for the dominant mass loss phase is $\sim0.6$-$2\times10^5$ yr, shorter than the thermal-pulsing AGB or RSG phases. The rate at which stars return mass to the ISM, $\sim0.1$ M$_\odot$ yr$^{-1}$ is about four times lower than the star formation rate, which would deplete the current ISM mass within about a Gyr, thus requiring additional, external gas supplies to sustain the long-term future of star formation in M33.
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All authors Atefeh Javadi, Jacco Th. van Loon, Mina Alizadeh, Seyed Azim Hashemi, Elham Saremi

Quantum Gases

A framework for separating dephasing from decoherence in matter-wave Bell interferometers

S. Kannan, Y. S. Athreya, X. T. Yan et al. (+2 more)

Matter-wave Bell interferometers provide a sensitive probe of mass-dependent decoherence in entangled quantum systems. The degree of entanglement is obtained from the Bell-correlation amplitude of this interferometer. For observing potential mass-dependent decoherence, a reliable interpretation of any observed reduction in the Bell correlation amplitude is required, which depends on three factors: geometric dephasing, environmental decoherence, and technical dilution from source and detection statistics. In this work, we present a framework based on the Schwinger SU(2) mapping to separate these contributions into local unitaries or dissipative channels. We show that by evaluating the Bell correlation at zero interferometer path difference, it is possible to extract a source-distribution-independent Bell correlation amplitude reduction. When this framework is extended to involve atoms of different mass, we show that the known differential decoherence channels are negligible at current sensitivity. This yields a concrete bound at which a dual-species Bell interferometer would begin to signal differential decoherence beyond the known systematics, opening the way for such systems to probe new physics, such as mass-dependent decoherence mechanisms.
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All authors S. Kannan, Y. S. Athreya, X. T. Yan, S. S. Hodgman, A. G. Truscott

Instrumentation and Methods for Astrophysics

Noise reduction in suspension control with photon-pressure actuator for CHRONOS gravitational wave detector

Daiki Tanabe, Yuki Inoue and Mario Juvenal S. Onglao III

Improving sub-Hz sensitivity of gravitational wave (GW) detectors is important to detect heavier binary black hole mergers and study phenomena in stronger gravity fields. Torsion-bar-based GW detectors have been projected to focus on low-frequency GW. Among noise sources of GW detector, actuation noise induced by vibration of force sources and fluctuation of environmental magnetic fields is one that increases in low frequency. In this study, we propose photon-pressure actuator as a solution to isolate an actuator from seismic and magnetic noise. It can also be used as a photon calibrator. We designed an optical layout of the photon-pressure actuator having four beams independently controlled and applied it to CHRONOS experiment. Based on a realistic power control system, we estimated its maximum torque amplitude around yaw rotation axis as $1.0\times 10^{-8}$ N$\cdot$m and actuation efficiency as $6.6\times 10^{-13}$ rad/V, which are sufficiently large for controlling the CHRONOS torsion bar. The actuation noise was estimated as $5.3\times 10^{-19}$ rad ${\rm Hz}^{-1/2}$ at 1 Hz, lower than the target sensitivity of CHRONOS. Assuming its usage as a photon calibrator, the estimated systematic error was 1.14%.
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Pattern Formation and Solitons

Using the Ehrenfest theorem for determining the self-focusing and self-trapping of nonlinear beams

Chandroth P. Jisha, Stefan Nolte and Alessandro Alberucci

We discuss how to generalize the Ehrenfest theorem for the computation of the width of nonlinear waves obeying the nonlinear Schrodinger equation. To do that, we model the nonlinear potential as a quantum harmonic oscillator (QHO) whose strength depends on the power and on the wavefunction width. We apply the model to different types of nonlinear responses, eventually comparing the results with numerical simulations. Our model has the advantage of explaining the main properties of nonlinear confined waves, such as stability and breathing, in a relatively simple and intuitive manner.
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Materials Science

Interface-resolved structural properties of epitaxial Y$_3$Fe$_5$O$_{12}$/ Gd$_3$Fe$_5$O$_{12}$ bilayers grown on GGG(111) by pulsed laser deposition

Kshitij Singh Rathore, Abhisek Mishra, Swayang Priya Mahanta et al. (+10 more)

Epitaxial Y$_3$Fe$_5$O$_{12}$ (YIG) and Gd$_3$Fe$_5$O$_{12}$ (GdIG) thin films, along with their bilayer heterostructures, were grown on Gd$_3$Ga$_5$O$_{12}$(GGG)(111) substrates using pulsed laser deposition. Structural properties were investigated using X-ray diffraction, reciprocal space mapping, and cross-sectional transmission electron microscopy. The results confirm high crystalline quality and coherent epitaxial growth, with RSM revealing a coexistence of strained and partially relaxed regions governed by layer sequence. TEM analysis shows sharp interfaces, columnar microstructures, and antiphase boundaries that facilitate strain relaxation. A comparative study indicates that the GGG/YIG/GdIG stacking sequence exhibits improved structural quality with reduced defect density, attributed to the superior epitaxial growth of YIG on the substrate. These findings highlight the critical role of growth sequence in controlling strain and interfacial structure in garnet heterostructures.
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All authors Kshitij Singh Rathore, Abhisek Mishra, Swayang Priya Mahanta, Shubhransu Sahoo, Anupama Swain, Pushpendra Gupta, Kapil Gupta, Jose M. Caicedo-Roque, Jessica Padilla-Pantoja, Francisco J. Belarre, Belen Ballesteros, Jose Santiso, Subhankar Bedanta

Solar and Stellar Astrophysics

Oscillatory reconnection and resonant response to wave excitation in 2D coronal null points

Konstantinos Karampelas and Tom Van Doorsselaere

Null points are magnetic field singularities, where the magnetic field strength rapidly drops to zero. In the solar atmosphere, null points are known sites of magnetic reconnection and wave generation and are associated with highly energetic phenomena, such as flares. The aim of this study is to explore the connection between the properties of oscillatory reconnection at null points and the latter's nature as resonant cavities for waves. We perform a set of 2D and 2.5D magnetohydrodynamics simulations of single null points in a stratified solar atmosphere, using the PLUTO code. We perturb each null point through a single propagating pulse and its reflections from the bottom boundary, hitting the null point in an asymmetrical fashion. This leads to both periodic reconnection events and wave refraction around the null point. We find that each null point imposes frequencies on the reconnection matching those of the waves generated from the individual resonant cavity. These frequencies also differ from those excited by the low frequency driver of the reflected waves returning to the null point, the latter lying outside the $95\%$ confidence interval. As such, excited periodic reconnection can be characterised as oscillatory reconnection, i.e. with properties intrinsic to the null points. Finally, the generated waves at the null propagate across the domain, reminiscent of the observed quasi-periodic fast-propagating waves. We provide results showing a direct connection between oscillatory reconnection and the generated high-frequency wavetrains at null points in the solar corona. The propagating waves generated at the resonant cavity, reminiscent of the observed quasi-periodic fast-propagating waves can provide us a diagnostic tool for the reconnection process at the null point and the coronal plasma conditions.
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Chemical Physics

Rem3Di: Learning smooth, chiral 3D molecular descriptors from atomistic foundation models

Steffen Wedig, Felix Burton, Rokas Elijošius et al. (+2 more)

Foundation machine-learned interatomic potentials (MLIPs) are trained on large quantum-mechanical datasets and generalise across broad regions of chemical and configurational space. Beyond their usual role in accelerating sampling-based simulations, their internal representations encode chemically rich local atomic environments. Here, we introduce Rem3Di, a representation-learning framework that repurposes latent features from atomistic foundation models as transferable molecular descriptors for property prediction and virtual screening. Rem3Di combines a potential's per-atom features into a single fixed-length descriptor of the whole molecule that varies smoothly with three-dimensional structure and is invariant to the ordering of the atoms. The descriptor can be used directly or fine-tuned for specific prediction tasks. To capture molecular handedness, Rem3Di constructs pseudoscalar features, which are unchanged by rotation but reverse sign under mirror reflection. This lets the descriptor distinguish enantiomers, which can differ in activity and toxicity. The transformer is pretrained on large molecular datasets by reconstructing corrupted atom features, so no experimental labels are required. Across public drug-property benchmarks, Rem3Di matches or exceeds published baselines without relying on classical 2D fingerprints. Additionally, the same descriptor yields chemically meaningful differentiation of transition-metal complexes without predefined bonding rules or handcrafted representations. Rem3Di therefore provides a route from simulation-trained atomistic representations to transferable, chirality-aware molecular representations for chemical machine learning.
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All authors Steffen Wedig, Felix Burton, Rokas Elijošius, Christoph Schran, Lars L. Schaaf

Accelerator Physics

Capabilities and Limitations of Non-Redundant Aperture Interferometry for Beam Size Measurements

C. Carilli, U. Iriso, B. Nikolic et al. (+3 more)

Non-Redundant Aperture Interferometry (NRAI) is a beam characterization technique developed at ALBA in collaboration with radio-astronomy institutes. It enables the single-acquisition measurement of the full 2D transverse profile of the electron beam using visible synchrotron radiation. To better understand the technique limitations and performance, we performed extensive SRW simulations and compare them with experimental data. This paper presents the results of these studies, which define the capabilities and limits of NRAI applied to the current ALBA machine.
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All authors C. Carilli, U. Iriso, B. Nikolic, N. Thyagarajan, L. Torino, A. Turull Barot

High Energy Astrophysical Phenomena

Constraints on the VHE counterpart of two binary black hole mergers observed by the MAGIC and CTAO LST-1 telescopes

K. Abe, S. Abe, J. Abhir et al. (+359 more)

We present very-high-energy gamma-ray observations of two binary black hole merger candidates, GW240615_113620 and GW241125_010116, performed with the Major Atmospheric Gamma Imaging Cherenkov (MAGIC) telescopes and the first Large-Sized Telescope of the Cherenkov Telescope Array Observatory's (CTAO LST-1). GW240615_113620 was the best localized event of the fourth observing run of the LIGO-Virgo-KAGRA gravitational waves interferometers. GW241125_010116 was temporally and spatially coincident with a sub-threshold short-duration burst detected with the Swift-Burst Alert Telescope (BAT), the Swift-X-Ray Telescope (XRT) and the Einstein Probe Follow-up X-ray Telescope (FXT). We observed the two events in stereoscopic mode, taking advantage of the improved sensitivity of joint MAGIC+LST-1 observations. No detection was achieved in the GeV-TeV gamma-ray band for any of the two sources. The unfavourable observing conditions of both events posed a challenge for a standard analysis and therefore a non standard analysis was necessary for both objects. Owing to the small localization area and the association with a GRB-like burst respectively, these events represented an unprecedented opportunity to study in details the electromagnetic emission from binary black holes merger events and, in particular, we discussed two theoretical models that predict a detectable gamma-ray emission and the possible future applications.
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All authors K. Abe, S. Abe, J. Abhir, A. Abhishek, V. A. Acciari, F. Acero, A. Aguasca-Cabot, I. Agudo, I. Albanese, D. Ambrosino, F. Ambrosino, T. Aniello, S. Ansoldi, L. A. Antonelli, C. Aramo, C. Arauner, A. Arbet-Engels, C. Arcaro, T.T.H. Arnesen, P. Aubert, A. Babić, C. Bakshi, A. Baktash, M. Balbo, A. Bamba, A. Baquero-Larriva, U. Barres-de-Almeida, J. A. Barrio, L. Barrios-Jiménez, I. Batkovic, J. Baxter, J. Becerra-González, W. Bednarek, E. Bernardini, J. Bernete, A. Berti, J. Besenrieder, C. Bigongiari, A. Biland, E. Bissaldi, O. Blanch, Ž. Bošnjak, G. Bonnoli, P. Bordas, L. Breton-Zaourat, A. Briscioli, E. Bronzini, G. Brunelli, J. Buces, A. Bulgarelli, I. Burelli, L. Burmistrov, C. Campa, A. Campoy-Ordaz, M. Cardillo, S. Caroff, A. Carosi, R. Carosi, R. Carraro, M. Carretero-Castrillo, F. Cassol, A. J. Castro-Tirado, D. Cerasole, G. Ceribella, A. Cerviño-Cortínez, Y. Chai, A. Chiavassa, A. Chilingarian, G. Chon, L. Chytka, G. M. Cicciari, A. Cifuentes Santos, J. L. Contreras, J. Cortina, H. Costantini, S. Covino, M. Croisonnier, G. D'Amico, P. Da-Vela, M. Dalchenko, F. Dazzi, A. De-Angelis, M. de-Bony-de-Lavergne, B. De-Lotto, R. de-Menezes, G. De-Palma, V. de-Souza, R. Del-Burgo, L. Del-Peral, M. Delfino, C. Delgado Mendez, J. Delgado-Mengual, D. della-Volpe, L. Di-Bella, C. Di-Domenico, A. Di-Piano, F. Di-Pierro, R. Di-Tria, L. Di-Venere, C. Díaz, A. Dinesh, E. Do Souto Espineira, D. Dominis-Prester, A. Donini, D. Dorner, M. Doro, L. Eisenberger, D. Elsässer, G. Emery, J. Escudero, L. Farina, L. Feligioni, F. Ferrarotto, A. Fiasson, L. Foffano, L. Font, F. Frías-García-Lago, Y. Fukazawa, S. Gallozzi, J. Garcia-Garcia, R. J. García López, S. Garcia-Soto, D. Gasparrini, S. Gasparyan, M. Gaug, J. G. Giesbrecht Paiva, N. Giglietto, F. Giordano, P. Gliwny, N. Godinovic, T. Gradetzke, R. Grau, J. Green, G. Grolleron, S. Gunji, P. Günther, D. Hadasch, A. Hahn, M. Hashizume, T. -Hassan, K. Hayashi, L. Heckmann, M. Heller, J. Herrera-Llorente, N. Hiroshima, D. Hoffmann, D. Horns, J. Houles, D. Hrupec, T. Inada, S. Inoue, K. Ioka, M. Iori, D. Israyelyan, A. Iuliano, J. Jahanvi, I. Jiménez-Martínez, J. Jiménez-Quiles, I. Jorge-Rodrigo, J. Jurysek, M. Kagaya, S. Kankkunen, V. Karas, H. Katagiri, T. Kayanoki, D. Kerszberg, M. Khachatryan, G. W. Kluge, Y. Kobayashi, K. Kohri, J. Konrad, P. Kornecki, P. M. Kouch, H. Kubo, J. Kushida, B. Lacave, M. Láinez, A. Lamastra, L. Lemoigne, E. Lindfors, M. Linhoff, S. Lombardi, F. Longo, R. López-Coto, M. López-Moya, A. López-Oramas, S. Loporchio, A. Lorini, J. Lozano-Bahilo, F. Lucarelli, H. Luciani, L. Lulić, P. L. Luque-Escamilla, P. Majumdar, M. Makariev, M. Mallamaci, D. Mandat, G. Maneva, M. Manganaro, S. Mangano, D. K. Maniadakis, G. Manicò, K. Mannheim, F. Marini, M. Mariotti, G. Marsella, J. Martí, D. Martin, G. Martínez, M. Martínez, O. Martinez, P. Maruš, evec, M. Massa, D. Mazin, S. Menchiari, J. Méndez-Gallego, S. Menon, E. Mestre-Guillen, D. Miceli, T. Miener, J. M. Miranda, J. M. Miranda, R. Mirzoyan, M. Mizuno, M. Molero-Gonzalez, E. Molina, H. A. Mondal, T. Montaruli, A. Moralejo, S. Morales-Sanchez-De-Lozada, K. Morita, A. -Morselli, V. Moya, K. Mrakovčić, A. L. Müller, H. Muraishi, T. Nagata, S. Nagataki, T. Nakamori, C. Nanci, A. Negro, A. Neronov, V. Neustroev, D. Nieto-Castaño, M. Nievas-Rosillo, C. Nigro, L. Nikolić, K. Nilsson, K. Noda, V. Novotny, S. Nozaki, M. Ohishi, A. Okumura, R. Orito, L. Orsini, J. Otero-Santos, P. Ottanelli, S. Paiano, M. Palatiello, G. Panebianco, D. Paneque, R. Paoletti, J. M. Paredes, M. Pech, M. Pecimotika, M. Peresano, F. Perrotta, M. Persic, F. Pfeifle, E. Pietropaolo, M. Pihet, G. Pirola, C. Plard, F. Podobnik, M. Polo, C. Pozo-Gonzaléz, P. G. Prada Moroni, E. Prandini, S. Rainò, R. Rando, W. Rhode, M. Ribó, J. Rico, V. Rizi, G. Rodriguez-Fernandez, A. Roy, E. Ruiz-Velasco, N. Sahakyan, T. Saito, S. Sakurai, D. A. Sanchez, H. Sano, E. Santos-Moura, T. Šarić, Y. Sato, F. G. Saturni, V. Savchenko, F. Schiavone, K. Schmitz, F. Schussler, T. Schweizer, M. Seglar-Arroyo, U. Sharma, T. Siegert, G. Silvestri, A. Simongini, J. Sitarek, V. Sliusar, D. Sobczynska, I. Sofia, A. Stamerra, J. Strišković, D. Strom, M. Strzys, Y. Suda, A. Sunny, H. Tajima, M. Takahashi, R. Takeishi, S. J. Tanaka, J. Tartera Barberà, T. Tavernier, P. Temnikov, Y. Terada, K. Terauchi, T. Terzic, M. Teshima, M. Tluczykont, T. Tomura, D. F. Torres, F. Tramonti, P. Travnicek, G. Tripodo, A. Tutone, S. Ubach, M. Vacula, M. Vázquez-Acosta, S. Ventura, G. Verna, I. Viale, A. Viana, A. Vigliano, C. F. Vigorito, E. Visentin, V. Vitale, M. Vorbrugg, G. Voutsinas, I. Vovk, T. Vuillaume, R. Walter, C. Walther, L. Wan, P. Witczak, F. Wersig, T. Yamamoto, R. Yamazaki, Y. Yao, P. K. H. Yeung, T. Yoshida, T. Yoshikoshi, W. Zhang