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Physics Physics

physics Watch Physics

Tuesday 13 January

Instrumentation and Detectors · Cross-listed from hep-ex

Search for Cosmic Ray Electron Boosted Dark Matter with the CDEX-10 Experiment

R. Xu, L. T. Yang, Q. Yue et al. (+85 more)

We present new constraints on the cosmic ray electron boosted light dark matter (CReDM) using the 205.4 kg$\cdot$day data of the CDEX-10 experiment located at the China Jinping Underground Laboratory. The cosmic ray electron spectrum and distribution in the Galaxy are generated by the $\tt GALPROP$ code package. In the calculation process of DM-electron scattering process in the Galaxy, we consider the energy-dependency of the DM-electron scattering cross section. The constraints on CReDM are set for both heavy and light mediator scenarios using the CDEX-10 dataset. The result exceeds previous Standard Halo Model (SHM) limits for DM mass lower than 0.6 MeV in heavy mediator case and corresponds to the best sensitivity among all direct detection experiments from 1 keV to 0.5 MeV in the light mediator scenario.
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All authors R. Xu, L. T. Yang, Q. Yue, K. J. Kang, Y. J. Li, H. P. An, Greeshma C., J. P. Chang, H. Chen, Y. H. Chen, J. P. Cheng, J. Y. Cui, W. H. Dai, Z. Deng, Y. X. Dong, C. H. Fang, H. Gong, Q. J. Guo, T. Guo, X. Y. Guo, L. He, J. R. He, H. X. Huang, T. C. Huang, S. Karmakar, Y. S. Lan, H. B. Li, H. Y. Li, J. M. Li, J. Li, M. C. Li, Q. Y. Li, R. M. J. Li, X. Q. Li, Y. L. Li, Y. F. Liang, B. Liao, F. K. Lin, S. T. Lin, J. X. Liu, R. Z. Liu, S. K. Liu, Y. D. Liu, Y. Liu, Y. Y. Liu, H. Ma, Y. C. Mao, A. Mureed, H. Pan, N. C. Qi, J. Ren, X. C. Ruan, M. B. Shen, H. Y. Shi, M. K. Singh, T. X. Sun, W. L. Sun, C. J. Tang, Y. Tian, H. F. Wan, G. F. Wang, J. Z. Wang, L. Wang, Q. Wang, Q. Wang, Y. F. Wang, Y. X. Wang, H. T. Wong, Y. C. Wu, H. Y. Xing, K. Z. Xiong, Y. Xu, T. Xue, Y. L. Yan, N. Yi, C. X. Yu, H. J. Yu, X. Yu, M. Zeng, Z. Zeng, F. S. Zhang, P. Zhang, P. Zhang, Z. Y. Zhang, M. G. Zhao, J. F. Zhou, Z. Y. Zhou, J. J. Zhu

Chemical Physics · Cross-listed from cond-mat.mtrl-sci

Cyclic- and helical-symmetry-adapted phonon formalism within density functional perturbation theory

Abhiraj Sharma and Phanish Suryanarayana

We present a first-principles framework for the calculation of phonons in nanostructures with cyclic and/or helical symmetry. In particular, we derive a cyclic- and helical-symmetry-adapted representation of the dynamical matrix at arbitrary phonon wavevectors within a variationally formulated, symmetry-adapted density functional perturbation theory framework. In so doing, we also derive the acoustic sum rules for cylindrical geometries, which include a rigid-body rotational mode in addition to the three translational modes. We implement the cyclic- and helical-symmetry-adapted formalism within a high-order finite-difference discretization. Using carbon nanotubes as representative systems, we demonstrate the accuracy of the framework through excellent agreement with periodic plane-wave results. We further apply the framework to compute the Young's and shear moduli of carbon nanotubes, as well as the scaling laws governing the dependence of ring and radial breathing mode phonon frequencies on nanotube diameter. The elastic moduli are found to be in agreement with previous density functional theory and experimental results, while the phonon scaling laws show qualitative agreement with previous atomistic simulations.
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Physics and Society

Bipartite structure and dynamics of political corruption networks

Monica V. Prates, Arthur A. B. Pessa, Sebastian Goncalves et al. (+2 more)

Political corruption is inherently an affiliation process linking agents to corruption cases; yet it is often studied via one-mode projections that connect co-offenders within the same scandal, implying a loss of information that potentially confounds properties of agents and cases. Here, we adopt a bipartite representation to analyze datasets of corruption scandals in Brazil and Spain spanning nearly three decades. By tracking the temporal growth of these networks, we quantify density and redundancy measures to capture partner reuse and co-occurrence across cases. Networks in both countries become progressively sparser over time, and agent redundancy is systematically higher than case redundancy, indicating a small cadre of recidivists who recombine largely with novice partners rather than forming durable co-offending ties. These networks exhibit near-exponential degree distributions, reflecting low recidivism and likely high coordination costs and secrecy constraints of large-scale scandals. Our bipartite view further reveals a moderate cross-mode disassortative degree mixing between agents and cases, with high-degree agents distributing their activity across small cases and large scandals mainly comprising low-degree participants. Finally, identifying atypical individuals within the bipartite structure reveals criminal trajectories marked by a gradual rise in network embeddedness that can appear ordinary in agent-projected networks.
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All authors Monica V. Prates, Arthur A. B. Pessa, Sebastian Goncalves, Matjaz Perc, Haroldo V. Ribeiro

Atomic Physics

Portable Single-Beam Atomic Total-Field Magnetometer for Stand-off Magnetic Sensing

Heonsik Lee, Hyunbeen Lee, Minseok Choi et al. (+2 more)

Optically pumped atomic magnetometers (OPAMs) offer high sensitivity at room temperature and are increasingly considered for portable magnetic sensing in geomagnetic-field environments. Here we report a handheld-scale, single-beam scalar $^{87}$Rb OPAM with a sensor-head volume of approximately 110~mL. The device operates in an all-optical Bell-Bloom configuration and uses digital lock-in, dispersive tracking of the $^{87}$Rb Larmor resonance, implemented with a hybrid electronics stack that combines in-house control hardware with commercial modules. A single frequency-modulated laser beam performs both pumping and probing without RF coils. All signal processing is realized in Python on a single-board computer paired with a commercial off-the-shelf (COTS) data-acquisition module, enabling immediate deployment without dedicated signal-processing hardware. The magnetometer has an intrinsic in-band field sensitivity of approximately 21~pT/$\sqrt{\mathrm{Hz}}$, estimated from the lock-in dispersion slope, over a 0.1–30~Hz closed-loop in-band region with a digital-output rate of 200~samples/s. In an unshielded Earth-field deployment, we detect repeatable transient magnetic signatures from a controlled elevator motion sequence and quantify standoff observability over sensor-elevator distances from 1.25~m to 10~m. These results show that compact scalar OPAMs can provide bandwidth and range-resolved event sensitivity suitable for field-deployable magnetic anomaly detection and infrastructure monitoring in realistic geomagnetic environments.
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All authors Heonsik Lee, Hyunbeen Lee, Minseok Choi, Yoontae Hwang, Deok-Young Lee

Optics

Broadband wide-view all-dielectric handedness-preserving mirror

Natalia Salakhova, Andrey Demenev, Oleg Klimenko et al. (+4 more)

We report the theoretical design and experimental realization of a wideband, all-dielectric mirror that preserves the handedness of incident light upon reflection in the near-infrared range. The mirror consists of a high-contrast, near-subwavelength, one-dimensional dielectric grating on a Bragg mirror. We optimized this structure using a genetic algorithm and demonstrated its robustness against geometric imperfections and oblique incidence. Experimental reflection spectra measured under normal incidence in a circular polarization basis demonstrate a more than 100-nm-wide reflection band in which more than 98% of the reflected light preserves its handedness. The total reflection coefficient reached 80%. Furthermore, we demonstrate that the fabricated mirror maintains high performance even under oblique incidence for angles up to $\pm 15^\circ$. Owing to these unique characteristics, this mirror can serve as a reflective phase plate, making it an excellent candidate for the creation of a Fabry-Pérot resonator for chiral light.
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All authors Natalia Salakhova, Andrey Demenev, Oleg Klimenko, Vladimir Kulakovskii, Vladimir Antonov, Nikolay Gippius, Sergey Dyakov

Optics

Attosecond quantum optics

Mohamed Sennary, Javier Rivera-Dean, Yihe Wange et al. (+2 more)

Modern quantum optics primarily operates in the quasistationary regime, isolated from the intrinsic timescales of ultrafast optical fields. Pushing these boundaries into the femtosecond and attosecond domains is a critical frontier. Here, we generate, shape, and interrogate the quantum state of an ultrafast squeezed light field. Our optical metrology reveals a highly dynamic, time dependent squeezing distribution across individual half cycles of the electric field. Incorporating this intracycle squeezing into strong field simulations demonstrates that the temporal redistribution of quantum uncertainty fundamentally reshapes the quantum strong field physics of high harmonic emission. Furthermore, we achieve attosecond scale control of the squeezed state, visualized through inferred effective Wigner representations. Finally, we show that ultrafast squeezed light encodes its quantum properties into a photoinduced tunneling current within a petahertz phototransistor with subfemtosecond resolution, demonstrating a direct optical electronic quantum coupling. This work lays the foundation for the emerging field of ultrafast quantum optics and unlocks new avenues for high speed quantum communication and photonics.
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All authors Mohamed Sennary, Javier Rivera-Dean, Yihe Wange, Maciej Lewenstein, Mohammed Th. Hassan

Chemical Physics

Solvation Lies Within: Simulating Condensed-Phase Properties from Local Electronic Structures

Kasper F. Schaltz, Jonas Greiner, Filippo Lipparini et al. (+1 more)

In transitions between different environmental settings, a molecular system inevitably undergoes a range of detectable changes, and the ability to accurately simulate such responses, e.g., in the form of shifts to molecular energies, remains an important challenge across physical chemistry. Based on an exact decomposition of total energies from Kohn–Sham density functional theory in a basis of spatially localized molecular orbitals, the present work outlines a robust protocol for sampling the effect of solvation within homogeneous condensed phases by focusing on perturbations to local electronic structures only. We report chemically intuitive results for binding energies of water, ethanol, and acetonitrile that all display fast convergence with respect to the bulk size. Results stay largely invariant with respect to the choice of basis set while reflecting differences in density functional approximations, and our protocol thus allows for a physically sound and efficient estimation of general effects related to bulk solvation.
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All authors Kasper F. Schaltz, Jonas Greiner, Filippo Lipparini, Janus J. Eriksen

Medical Physics

Percentile-based probabilistic optimization for systematic and random uncertainties in radiation therapy

Albin Fredriksson, Erik Engwall, Jenneke de Jong et al. (+1 more)

Geometric uncertainty can degrade treatment quality in radiation therapy. While margins and robust optimization mitigate these effects, they provide only implicit control over clinical goal fulfillment probability. We therefore develop a probabilistic planning framework using a percentile-based optimization function that targets a specified probability of clinical goal fulfillment. Systematic and random uncertainties were explicitly modeled over full treatment courses. A scenario dose approximation method based on interpolation between a fixed set of doses was used, enabling efficient simulation of treatment courses during optimization. The framework was evaluated on a prostate case treated with volumetric-modulated arc therapy (VMAT) and a brain case treated with pencil beam scanning (PBS) proton therapy. Plans were compared to conventional margin-based and worst-case robust optimization using probabilistic evaluation. For the prostate case, probabilistic optimization improved organ at risk (OAR) sparing while maintaining target coverage compared to margin-based planning, increasing average OAR goal fulfillment probability by 13.3 percentage points and reducing 90th percentile OAR doses by an average of 3.5~Gy. For the brain case, probabilistic optimization improved target minimum dose passing probabilities (e.g., 88% vs.~22% for $D_{95}$) and brainstem maximum dose passing probability (70% vs.~30%), while maintaining comparable or improved OAR sparing compared to worst-case optimization. Probabilistic optimization enables explicit and interpretable control over goal fulfillment probabilities. Combining full treatment course modeling with efficient approximate dose calculation, the proposed framework improved the trade-off between target coverage and OAR sparing compared to conventional planning approaches in both photon and proton therapy.
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All authors Albin Fredriksson, Erik Engwall, Jenneke de Jong, Johan Sundström

Classical Physics

The connection between electromagnetic stress tensors and the dielectric constant in a medium

R. Dengler

We perform explicit calculations for microscopic models to confirm that a single, unique electromagnetic stress tensor exists in a dielectric medium: the microscopic tensor $\sigma^{#}$. We demonstrate that the conventional macroscopic stress tensor of continuum electrodynamics, which contains the derivative of the dielectric coefficient, is merely a representation of $\sigma^{#}$'s spatial average. This result establishes that, contrary to claims in the literature, both this averaged electromagnetic stress and the hydrodynamic pressure always possess a unique physical meaning.
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Chemical Physics

Exciton-Exciton and Exciton-Photon Annihilation in Polaritonic Systems

Luca Nils Philipp, Julian Lüttig and Roland Mitric

Strong light–matter interactions forming hybrid quasiparticles termed polaritons can specifically tailor molecular photophysics. In this spirit, enhancing energy transport has recently been of special interest. Exciton–exciton annihilation is commonly used to quantify energy transfer in excitonic systems, and has been recently applied to investigate transport dynamics in polaritonic systems. However, the interpretation of experimental findings is challenging without a microscopic theory that accounts for the various nonradiative relaxation channels determining the quasiparticle diffusion length. In this work, we develop a microscopic model for polariton annihilation based on exciton–exciton annihilation and propose an exciton–photon annihilation as the decisive process that competes with exciton–exciton annihilation. The interplay between exciton–exciton and exciton–photon annihilation ultimately governs the annihilation dynamics and sets the fundamental limit to the transport efficiency. Our model explains recent experimental results and demonstrates that increased annihilation rates might serve as an explicit fingerprint to differentiate between the response of polaritons and other untargeted effects.
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Optics

Bridging Theory and Experiment in Virtually Imaged Phased Array (VIPA) Spectrometers

Kiumars Aryana, D. Michelle Bailey, Solomon I. Woods et al. (+1 more)

Virtually imaged phased array (VIPA) spectrometers provide high resolution and fast acquisition in a compact design, but their performance is sensitive to fabrication tolerances, component dimensions, and alignment. Here, leveraging numerical simulations validated by experimental data, we present a framework to identify the parameters that limit VIPA spectrometer resolution. This framework is applied to the construction of a new mid-infrared VIPA spectrometer, tested at wavelengths near $\lambda$ = 4.6 $\mu$m with both continuous-wave and frequency-comb laser sources, with a resolving power predicted by analytical expressions to be as high as $RP$ = 830 000 (corresponding to a resolution of $\delta\nu$ = 78 MHz). Validated numerical simulations, however, provided a more realistic estimate that captures limits set by all the optical components. By minimizing aberrations and optimizing alignment, a resolving power of $RP$ = 440 000 ($\delta\nu$ = 150 MHz) was experimentally achieved, corresponding to 80 % of the value predicted by numerical simulation of the entire spectrometer. The results bridge the gap between analytical expressions and experimental results for compact, high-resolution VIPA spectrometers to enable more efficient fabrication and advanced design across critical areas like space optics, line-by-line pulse shaping, and broadband spectral sensors.
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All authors Kiumars Aryana, D. Michelle Bailey, Solomon I. Woods, Adam J. Fleisher

Optics

Excitonic Landscape of Monolayer Transition-Metal Dichalcogenides: Experimental Discrepancies, Theoretical Advances, and Strain Dependence

Cem Sevik, Purushothaman Manivannan, Fulvio Paleari et al. (+1 more)

Excitons in monolayer transition-metal dichalcogenides (TMDs) have garnered significant attention because of their large binding energies due to weakly screened Coulomb interaction, and direct bandgap at the K/K$^\prime$ point in the hexagonal Brillouin zone featuring spin-polarised bands due to spin-orbit coupling and lack of inversion symmetry. This makes them prospective for next-generation optoelectronic and quantum devices. However, despite the intense research activity, the reported values for exciton binding energies, quasiparticle gaps, and spectral features exhibit substantial variation across both experimental and theoretical studies. In this article, we present a comprehensive and critical assessment of the current understanding of excitonic properties in single-layer TMDs, integrating results from the angle-resolved photoemission spectroscopy (ARPES), photoluminescence (PL) measurements, and other experimental techniques with first-principles theoretical insights. Special emphasis is placed on the comparison and reconciliation of discrepancies observed across different experimental setups and sample qualities. Furthermore, we highlight our state-of-the-art GW-BSE calculations, which include both equilibrium and laterally strained systems, to systematically analyse the behaviour of direct and indirect excitons. By evaluating the effect of strain as a tunable control variable, we demonstrate its potential to engineer excitonic properties, supported by cross-validation against prior theoretical predictions and experimental findings. In doing so, we clarify the sources of discrepancies in the literature and offer a unified perspective on excited-state engineering strategies in two-dimensional TMDs.
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All authors Cem Sevik, Purushothaman Manivannan, Fulvio Paleari, Milorad V. Milosevic

Biological Physics

FRET between NV centers in diamond and chlorophyll molecules: a novel resource for multimodal sensing and imaging in plant cells

Sebastian Westrich, Nimba Oshnik, Nina Thiele et al. (+5 more)

This work demonstrates efficient Forster resonance energy transfer (FRET) between ensembles of shallow nitrogen-vacancy (NV) centers located 7 nm and 9 nm below a single-crystal diamond surface and a naturally occurring fluorophore, namely a mixture of chlorophyll a and b molecules extracted from Arabidopsis thaliana. The broad fluorescence band of NV centers spectrally overlaps with the absorption of chlorophyll molecules, enabling FRET. As a result, depositing a chlorophyll layer on the diamond surface reduces the NV fluorescence lifetime from approximately 14 ns to below 4 ns, indicating efficient energy transfer. Laser-induced photobleaching of chlorophyll restores the unquenched NV lifetime. In contrast, NV centers located deeper within the diamond at depths of 40 nm and 72 nm remain unaffected, confirming that the observed quenching originates from a short-range FRET mechanism. The NV ensembles retain their optically detected magnetic resonance contrast while FRET is observed, demonstrating preservation of their spin properties. These proof-of-principle experiments establish the feasibility of combining FRET-based distance measurements with magnetic sensing using optically readable spins.
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All authors Sebastian Westrich, Nimba Oshnik, Nina Thiele, Nina Burmeister, Yanis Abdedou, Nikhita Khera, Stefanie J. Müller-Schüssele, Elke Neu

Biological Physics

Exchange-Symmetric Dissipation at the DNA-RNA Polymerase Interface

Tatsuaki Tsuruyama

In the DNA-RNA polymerase complex, RNA polymerase (RNAP) selectively incorporates ribonucleoside triphosphates according to the base information encoded in DNA, elongates the RNA strand, and progresses along the template. The state of the template DNA therefore conditions RNAP binding and chemical transitions. Conversely, from the viewpoint of DNA, the binding state and coordinate position of RNAP condition the local structural response of DNA. As RNAP advances, upstream DNA reanneals, downstream DNA opens, the RNA-DNA hybrid constrains the local geometry, and local bending and twisting of the DNA are updated. We introduce an interface dissipation, {\Sigma}int, that provides an exchange-symmetric measure of path irreversibility at the DNA-RNAP interface, independent of whether DNA or RNAP is assigned the role of observer or observed. Irreversibility is quantified by the path-space Kullback-Leibler (KL) divergence between the forward path measure and its time-reversed counterpart, from which the dissipation of the joint system and those of the marginal systems are defined. The non-negativity of the interface dissipation derived in this work does not rely on RNAP-specific kinetic assumptions; rather, it holds for general path processes for which the relevant KL divergences and conditional path measures are well defined. RNAP transcription is treated as a biophysical application of this general theorem to the DNA-RNAP interface.
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Optics

Geometry Driven Spin Polarization Effects in Waveguiding Plasmonic Crystal

Suman Mandal, Apuroop Vaidyam, Nishkarsh Kumar et al. (+3 more)

We investigated the modulation in the polarization-dependent optical behaviour of the waveguiding plasmonic crystal by varying the illumination and detection geometry. We employed the finite element method-based COMSOL simulation and Jones-Mueller formalisms to probe the variations in optical parameters by systematically varying the angle of incidence and azimuthal angle of the incident plane wave source, thereby quantifying the variations in the polarization anisotropy parameters. The enhancement of optical properties at various resonances and the tunability of the hybridized modes are discussed. Importantly, our study reveals that despite the system being perfectly inversion-symmetric and achiral, it exhibits circular polarization anisotropy effects for non-zero finite azimuthal angles, manifested in the off-block-diagonal elements of the constructed Mueller matrices. The origin of this intriguing circular anisotropy effect is unravelled using the sequential linear birefringence and linear diattenuation effects arising from geometrical polarization transformation. Its implications in the spin-orbit interaction of light in the plasmonic crystal system are discussed.
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All authors Suman Mandal, Apuroop Vaidyam, Nishkarsh Kumar, Sujit Rajak, Shyamal Guchhait, Nirmalya Ghosh

Fluid Dynamics

Chirality tomography: measuring local helicity from trajectory linking

Manuel Noseda, Bernardo Luciano Español, Pablo Daniel Mininni et al. (+1 more)

We present the first three-dimensional helicity maps of fully developed turbulence obtained through chirality tomography, a Lagrangian voxel-based method that reconstructs helicity density from particle trajectories. Our approach builds on an empirically established relation between helicity and trajectory linking, converting local counts of signed crossings $K$ into volumetric maps of dimensionless helicity, $H(\mathbf{x})$. We demonstrate that the entanglement of particle trajectories, quantified by the mean signed crossing number, provides a robust proxy for helicity, not only at the global scale, but also locally in space and time. Our method can reveal local spatial heterogeneities in helicity and relate them to large-scale flow organization, enabling the reconstruction of spatially resolved chiral structures. Applied to von Kármán experiments and Taylor-Green direct numerical simulations, the method reveals iso-helicity surfaces and coherent chiral features, while time series of $K$ accurately track the evolution of domain-averaged helicity. The proportionality between $K$ and $H$ remains robust across different voxel geometries and different values of particle inertia, but is not held in laminar or time-modulated flows. This study shows that chirality tomography provides a practical helicity diagnostic in turbulent flows, while establishing a direct bridge between trajectory-level topology and a fundamental dynamical invariant of turbulence.
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All authors Manuel Noseda, Bernardo Luciano Español, Pablo Daniel Mininni, Pablo Javier Cobelli

Chemical Physics

High-Resolution Infrared Spectroscopy and ASAP Analysis of Cyclopentadiene: The Vibrational Modes below 860 cm$^{-1}$ and the ${\nu}_{21}$ Mode at 961 cm$^{-1}$

Luis Bonah, Marie-Aline Martin-Drumel, Olivier Pirali et al. (+9 more)

The spectroscopic fingerprints of vibrationally excited states of astronomical molecules are interesting for multiple reasons. They are excellent temperature probes of the corresponding astronomical regions and are thought to be the origin of many unknown lines in astronomical survey spectra. Rovibrational spectra provide accurate vibrational energies and can guide subsequent pure rotational studies. The Automated Spectral Assignment Procedure (ASAP) greatly simplifies the rovibrational analysis when the rotational spectrum of either the upper or lower vibrational state is known with a high degree of accuracy (e.g., from a rotational analysis). Here, we present a new implementation of ASAP for the analysis of cyclopentadiene, a cyclic pure hydrocarbon that has already been detected astronomically toward the cold core of the Taurus Molecular Cloud. Using the synchrotron radiation extracted by the AILES beamline of the SOLEIL facility, we recorded mid- and far-infrared high-resolution spectra of cyclopentadiene. We analyzed the rovibrational spectrum of the $\nu_{21}$ fundamental (961 cm$^{-1}$) with ASAP and used ASAP$^2$ to determine the vibrational energies of the eight vibrational modes below 860 cm$^{-1}$. ASAP$^2$ is an extension of ASAP for rovibrational bands where the rotational structures of the lower and upper states are known with high accuracy, leaving only the vibrational band center to be determined. The presented rovibrational fingerprints agree with the results from pure rotational spectroscopy, demonstrating the efficiency and reliability of our new ASAP implementation.
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All authors Luis Bonah, Marie-Aline Martin-Drumel, Olivier Pirali, Francesca Tonolo, Michela Nonne, Mattia Melosso, Luca Bizzocchi, Cristina Puzzarini, Jean-Claude Guillemin, Christian P. Endres, Stephan Schlemmer, Sven Thorwirth

Biological Physics · Cross-listed from cond-mat.soft

Beyond uniform screening: electrostatic heterogeneity dictates solution structure of complex macromolecules

Fabrizio Camerin, Marco Polimeni, Letizia Tavagnacco et al. (+7 more)

The complexity of biomolecular interactions necessitates advanced methodologies to accurately capture their behavior in solution. In this work, we focus on monoclonal antibodies and adopt a multi-scale coarse-graining strategy for their modeling, with particular emphasis on the role of electrostatic interactions. Using scattering experiments, theoretical analysis, and large-scale computer simulations, we explicitly compare two selected case studies-markedly different in their charge distributions. Through mutually corroborating lines of evidence, we demonstrate that conventional approaches relying on electrostatic screening and implicit charge representations fail to capture the structural and thermodynamic properties of antibody solutions when strong charge heterogeneity is present, even at a moderate (amino acid) level of coarse-graining. These findings highlight the importance of a correct treatment of electrostatic interactions and ion screening for heterogeneously- and oppositely-charged colloidal and protein systems. Such considerations are essential to move beyond descriptive models towards a truly predictive framework, with direct implications for the formulation of therapeutics and the treatment of other complex soft-matter systems.
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All authors Fabrizio Camerin, Marco Polimeni, Letizia Tavagnacco, Jeffrey C. Everts, Szilard Saringer, Alessandro Gulotta, Nicholas Skar-Gislinge, Anna Stradner, Emanuela Zaccarelli, Peter Schurtenberger

Instrumentation and Detectors

Enhanced Athermal Phonon Responsivity in a Kinetic Inductance Detector with Integrated Phonon Collectors

Leonardo Pesce, Alessio Ludovico De Santis, Martino Calvo et al. (+10 more)

Cryogenic phonon detectors are adopted in light dark matter searches and coherent elastic neutrino-nucleus scattering experiments as they can achieve low energy thresholds. The phonon mediated sensing of silicon particle absorbers has already been proved with Kinetic Inductance Detectors (KIDs), acting both as sensors and athermal phonon absorbers. In this work we present the design and the performance of an improved detector design. In this architecture, the KID acts only as sensor and is coupled to dedicated phonon collectors. When a signal is coming from the substrate, the presence of a separated collector allows to detect an higher increase of quasi-particles density, thereby enhancing its responsivity. The meander of the KID is composed of a 77 nm trilayer wire of Aluminum-Titanium-Aluminum, while the phonon collectors are made of a 100 nm Aluminum layer and act as quasi-particles funnels. Inside the collectors, the absorbed athermal phonons generate quasi-particles which, after diffusion, are trapped in the lower-gap superconducting trilayer. The performance of this setup is compared to that of a standard phonon-mediated KID, showing an increased phonon collection efficiency by a factor of around 7.
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All authors Leonardo Pesce, Alessio Ludovico De Santis, Martino Calvo, Matteo Cappelli, Usasi Chowdhury, Angelo Cruciani, Giorgio Del Castello, Daniele Delicato, Matteo Folcarelli, Matteo del Gallo Roccagiovine, Alessandro Monfardini, Davide Quaranta, Marco Vignati

Applied Physics

Advances in All-Silicon Waveguides for Terahertz Integration

Nguyen H. Ngo, Weijie Gao and Masayuki Fujita

In chip-to-chip communication, terahertz waves provide a promising approach to achieve high data capacity with improved energy efficiency, effectively bridging the gap between electrical and optical domains. By realizing this potential, all-dielectric waveguides have emerged as high-speed interconnects, offering broad bandwidth and low-loss characteristics while being compatible with planar integration. This paper reviews different types of terahertz all-dielectric waveguides, including photonic-crystal and effective-medium-clad structures, and highlights recent progress in implementing these platforms to develop various passive functional devices, paving the way for high-speed operation and large-scale integration in terahertz systems.
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Instrumentation and Detectors

Design and construction of a cryogenic subcooler-box for supplying single phase supercritical helium to dark matter and gravitational wave experiments

Udai Raj Singh, Rajinikumar Ramalingam, Christoph Reinhardt et al. (+4 more)

We report on the design, development, and installation of the ALPS Cryo-Platform Subcooler Box (ACPS), which is part of the cryogenic platform being established in the HERA North Hall at DESY to supply helium for cooling large-scale dark-matter and gravitational-wave experiments with very high heat loads. The ACPS is capable of subcooling supercritical helium supplied via the 1.6-km-long HERA transfer line by means of a pipe heat exchanger immersed in a subcooler bath filled with liquid helium produced through Joule-Thomson valves. It is also equipped with numerous cryogenic components, including control valves, flow meters, and safety valves, enabling experimental operation to be carried out directly by the ACPS itself and thereby reducing the cryogenic requirements imposed on the experiments. To support a wide range of experiments, the ACPS provides three transfer lines that deliver different levels of cooling power.
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All authors Udai Raj Singh, Rajinikumar Ramalingam, Christoph Reinhardt, Olaf Korth, Jörg Penning, Jörn Schaffran, Axel Lindner

Atomic Physics

Precision Isotope-Shift Measurement of the ${}^1S_0 \leftrightarrow {}^3P_2$ Transition and a Multi-Transition King-Plot Consistency Test

Taiki Ishiyama, Koki Ono, Reiji Asano et al. (+6 more)

We present precision spectroscopy and isotope shift measurement of the ${}^1S_0 \leftrightarrow {}^3P_2$ clock transition in neutral ytterbium ($\mathrm{Yb}$) atoms. By revealing a magic wavelength at $905.4(2)$ nm, we successfully achieve the atomic spectrum narrower than $100$ Hz. The interleaved clock operation between isotopes allows us to determine isotope shifts of four bosonic isotope pairs at Hz-level uncertainties, which is combined with those of other four ultra-narrow transitions in $\mathrm{Yb}$ and $\mathrm{Yb}^+$ to construct the King plot. We show that a rich dataset spanning multiple transitions enables a test of a restricted isotope-shift ansatz comprising the leading mass and field shifts, one effective factorized higher-order Standard Model contribution, and a new-particle contribution. Within this ansatz, the five-transition data are inconsistent with the new-particle contribution serving as the sole additional contribution over the mass ranges $m_\phi \leq 6.5$ keV and $18$ keV $\leq m_\phi < 100$ keV, while the previous works rely on another bound set by the neutron scattering and $(g-2)_e$ measurements. This work paves the way for the effective use of precision isotope shift data in the King plot analysis and stimulates further measurements in Yb and other elements.
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All authors Taiki Ishiyama, Koki Ono, Reiji Asano, Hokuto Kawase, Tetsushi Takano, Ayaki Sunaga, Yasuhiro Yamamoto, Minoru Tanaka, Yoshiro Takahashi

Computational Physics

Multi-Task Fine-Tuning Enables Robust Out-of-Distribution Generalization in Atomistic Models

Chengqian Zhang, Duo Zhang, Anyang Peng et al. (+7 more)

Accurate de novo molecular and materials design requires structure-property models that generalize beyond known regimes. Although pretrained atomistic models achieve strong in-distribution accuracy after fine-tuning, their reliability under out-of-distribution (OOD) conditions remains unclear. We identify a critical failure mode in downstream adaptation: standard fine-tuning induces representation collapse, erasing pretrained chemical and structural priors and severely degrading OOD performance. To address this limitation, we propose multi-task fine-tuning (MFT), which jointly optimizes downstream property prediction with a physically grounded force-field objective inherited from pretraining. This approach preserves essential chemical priors while enabling task-specific adaptation. Across molecular and materials benchmarks, MFT consistently improves OOD generalization, approaching the theoretical limit set by in-distribution accuracy, while outperforming standard fine-tuning, training from scratch, and state-of-the-art task-specific models. These results establish safe adaptation as a central requirement for large atomistic models and position MFT as a practical and data-efficient pathway toward robust molecular and materials discovery.
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All authors Chengqian Zhang, Duo Zhang, Anyang Peng, Mingyu Guo, Yuzhi Zhang, Lei Wang, Guolin Ke, Linfeng Zhang, Tiejun Li, Han Wang

Optics

High-Power Single-Frequency Fiber Amplifiers

Chun-Wei Chen

High-power single-frequency fiber amplifiers are increasingly dominant in technologies that require high optical power, stability, and coherence simultaneously. In this chapter, we first provide an overview of their key characteristics, applications, architectures, and components. We then review the nonlinear acousto- and thermo-optical instabilities that limit power scaling and summarize the primary mitigation techniques. Finally, we discuss multimode excitation with wavefront shaping and anti-Stokes fluorescence cooling as two emerging strategies to circumvent the limitations of current approaches.
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Computational Physics · Cross-listed from hep-ex

MinGLE: A Minimalist, Configurable, and Pedagogical Geant4 Application Template

Jing Liu

The Geant4 toolkit is the leading software for the simulation of particle transport through matter, widely used in nuclear physics, high-energy physics, and medical physics. However, the initial learning curve for new developers can be steep, often due to the complexity and experiment-specific nature of many introductory examples. This paper introduces MinGLE (Mini Geant4 Learning Example), a dedicated application template designed to be a universal, flexible, and educational starting point for Geant4 projects. MinGLE achieves a complete, functional simulation kernel using fewer than 70 lines of core C++ code. This minimalism is realized by leveraging contemporary Geant4 features, including factory classes for run management and physics, and the Text Geometry format for detector definition. Furthermore, MinGLE employs a unique pedagogical structure, using Git tags to document the incremental development of eleven core Geant4 components, with each tagged version being fully compilable, executable, and testable, providing a clear, step-by-step learning resource.
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Atomic Physics

Causality of ultrafast photoionization from argon 3s using an ab initio relativistic approach

Rezvan Tahouri and Jan Marcus Dahlström

We study real-time photoionization flux at the $3s$ Amusia-Cooper minimum (ACM) in argon using ab initio simulations with the relativistic time-dependent configuration-interaction singles (RTDCIS) method in length (LG) and velocity (VG) gauges. A simple analytical model is used to interpret the results, and to construct Wigner delays and Wigner distributions for both gauges and relativistic channels of the photoelectron ($\epsilon p_j$ with $j=1/2$ and $3/2$). The two gauges are found to produce qualitatively different ionization dynamics, with LG having positive and VG having negative Wigner delays. The advancement of several femtoseconds, found for Wigner delays in VG, raises some concern for causality when atoms are ionized by attosecond pulses that are shorter than the absolute value of the Wigner delay. Reassuringly, numerical simulations of wave packets with RTDCIS show that the electrons behave in a causal way in both gauges. Weighted delays that take into account the temporal window of excitation (or the bandwidth of the pulses) are constructed from the Wigner distribution to reach agreement between the numerical simulations and our simple wave packet model. Furthermore, a strong effect of spin-orbit coupling of the photoelectron ($j$) is reported for ultrafast photoionization dynamics, and Schrödinger kitten and cat states are identified in the Wigner distributions as a result of the ACM. Our work paves the way for a deeper understanding of ultrafast photoionization and the role of causality in systems with strong electron-electron correlation effects.
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Atomic Physics

Light-induced spin-polarized desorption of Rb atoms from Co surfaces

Kanta Asakawa, Naoki Tanabe, Oki Watanabe et al. (+4 more)

The spin polarization of Rb atoms undergoing light-induced desorption from a spin-polarized Co (110) surface was investigated. Desorption induced by pulsed UV-light irradiation was driven by a non-thermal mechanism and the spins of the desorbed Rb atoms were polarized. This implies spin transfer between the surface and the adsorbate during desorption.
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All authors Kanta Asakawa, Naoki Tanabe, Oki Watanabe, Shuji Kamada, Keisuke Hara, Kaori Niki, Atsushi Hatakeyama

Optics

Tunable, high pulse energy and narrow linewidth gas-filled fiber laser across near- and mid-infrared

Yazhou Wang, Marcello Meneghetti, Manoj K. Dasa et al. (+9 more)

Wavelength widely tunable infrared fiber lasers that simultaneously deliver high pulse energies with narrow linewidths are critical for applications ranging from spectroscopy to nonlinear optics, yet achieving this combination has remained a long-standing challenge. Here, we demonstrate that gas-filled anti-resonant hollow-core fiber Raman laser offers tunability across a broad spectral range from the near-infrared (~1.4 {\mu}m) to the mid-infrared (~4.6 {\mu}m), with near microjoule level high pulse energy and a narrow linewidth of few gigahertz or less. This performance arises from a unique pump laser design together with an optimized selection of gas-filled anti-resonant hollow-core fibers, opening a promising pathway toward compact, high-performance tunable infrared fiber-based sources.
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All authors Yazhou Wang, Marcello Meneghetti, Manoj K. Dasa, Timothy Bate, J. E. Antonio-Lopez, Ian A. Davidson, Qiang Fu, Jaroslaw Rzegocki, Gregory T. Jasion, Francesco Poletti, Rodrigo Amezcua-Correa, Christos Markos

Accelerator Physics

High-power beyond extreme ultraviolet FEL radiation with flexible polarization at SHINE

Hanxiang Yang, Zhangfeng Gao, Bingyang Yan et al. (+3 more)

Linac-based free-electron lasers (FELs) feature high brightness, narrow bandwidth, controllable polarization, and wide wavelength tunability. With the rapid development of superconducting radio-frequency technology, linacs can now operate at MHz-level repetition rates, enabling FELs with both high repetition rates and high average power. Beyond extreme ultraviolet (BEUV) radiation is of great interest for scientific research and industrial applications, especially for next-generation lithography. Owing to the main design parameters of SHINE, the generation of BEUV radiation is a natural capability of the facility. The BEUV characteristics at SHINE are investigated and its achievable performance as a high-average-power light source is evaluated. By applying undulator tapering to enhance the energy extraction efficiency, kilowatt-level BEUV radiation with controllable polarization is shown to be achievable. These results demonstrate that SHINE can provide a high-performance BEUV source, offering a realistic pathway toward a high-average-power light source for next-generation high-resolution lithography.
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All authors Hanxiang Yang, Zhangfeng Gao, Bingyang Yan, Wencai Cheng, Nanshun Huang, Haixiao Deng

Plasma Physics

Near-axis quasi-isodynamic database

Eduardo Rodriguez and Gabriel G. Plunk

In this work, we investigate the landscape of quasi-isodynamic stellarators using the near-axis expansion of the magnetic field. Building on recent theoretical developments, we construct a database of more than 800,000 stable, approximately quasi-isodynamic vacuum magnetic configurations. These configurations span a range of field period numbers and other geometric control parameters, including the magnetic axis shape and plasma elongation. To evaluate each configuration, we use a broad set of measures, including effective ripple, sensitivity of the Shafranov shift to changes in plasma beta, the prevalence of maximum-J trapped particles, and the Rosenbluth-Hinton residual, among others. This enables an exhaustive, thorough and quantitative characterization of the database. Statistical analysis and modern machine learning techniques are then employed to find correlations, and identify key descriptors and heuristics to help understand tendencies that govern the behaviour of numerical optimization. The database provides baseline configurations for further studies, and to serve as tailored initial conditions for optimization. With this work we initiate a long term program to complete a systematic exploration of quasi-isodynamic stellarator design space.
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