Atomic Physics · Cross-listed from cond-mat.quant-gas
Strongly dipolar molecular Bose-Einstein condensates: From few- to many-body physics
Andreas Schindewolf, Jens Hertkorn, Ian Stevenson et al. (+8 more)
Recent advances in molecular cooling have enabled the realization of strongly dipolar Bose–Einstein condensates (BECs) of molecules, and BECs of many different molecular species may become experimentally accessible in the near future. Here, we explore the unique properties of such BECs and the new insights they may offer into dipolar
quantum fluids and many-body physics. We explore which parameter regimes can realistically be achieved using currently available experimental techniques, discuss how to implement these techniques, and outline which molecular species are particularly well suited to explore exotic new states of matter. We further determine how state-of-the-art beyond mean-field theories, originally developed for weakly dipolar
magnetic gases, can be pushed to their limits and beyond, and what other long-standing questions in the field of dipolar physics may realistically come within reach using molecular systems.
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All authors Andreas Schindewolf, Jens Hertkorn, Ian Stevenson, Matteo Ciardi, Phillip Gross, Dajun Wang, Tijs Karman, Goulven Quemener, Sebastian Will, Thomas Pohl, Tim Langen
Computational Physics · Cross-listed from cond-mat.mes-hall
Electrically tunable spin qubits in strain-engineered graphene p-n junctions
Myung-Chul Jung and Nojoon Myoung
Strain engineering enables
quantum confinement in pristine
graphene without degrading its intrinsic mobility and
spin coherence. Here, we extend previously proposed strain-induced charge-
qubit architectures by incorporating
spin degrees of freedom through Rashba
spin-orbit coupling (RSOC) and Zeeman fields, enabling
spin-
qubit operation in single-layer
graphene (SLG). In a
graphene p-n junction, a strain-induced nanobubble generates a pseudo-
magnetic field that forms double
quantum dots with gate-tunable level hybridization. Tight-binding
quantum transport simulations and a four-band model reveal two distinct avoided crossings:
spin-conserving gaps at zero detuning and
spin-flip gaps at finite detuning, the latter increasing with SOC strength while the former decreases. Time-domain simulations confirm detuning-dependent Rabi oscillations corresponding to these two operational regimes. These results demonstrate that strain-induced confinement combined with tunable SOC provides a viable mechanism for coherent
spin manipulation in pristine
graphene, positioning strained SLG as a promising platform for scalable
spin-based
quantum technologies.
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Computational Physics · Cross-listed from cond-mat.mtrl-sci
Multimode Jahn-Teller Effect in Negatively Charged Nitrogen-Vacancy Center in Diamond
Jianhua Zhang, Jun Liu, Z. Z. Zhu et al. (+3 more)
We present a first-principles study of the multimode Jahn-Teller (JT) effect in the exctied $^{3}E$ state of the negatively charged nitrogen-vacancy (NV) center in diamond. Using density functional theory combined with an intrinsic distortion path (IDP) analysis, we resolve the full activation pathways of the JT distortion and quantitatively decompose the distortion into contributions from individual vibrational modes. We find that multiple vibrational modes participate cooperatively in the JT dynamics, giving rise to a shallow adiabatic potential energy surface with low barriers, consistent with thermally activated pseudorotation. The dominant JT-active modes are found to closely correspond to vibrational features observed in two-dimensional electronic spectroscopy (2DES), in agreement with recent ab initio molecular dynamics simulations. Our results establish a microscopic, mode-resolved picture of vibronic coupling in the excited-state NV center and provide new insight into dephasing, relaxation, and optically driven dynamics relevant to solid-state
quantum technologies.
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All authors Jianhua Zhang, Jun Liu, Z. Z. Zhu, K. M. Ho, V. V. Dobrovitski, C. Z. Wang
Optics
Construction techniques and commissioning of the Three-Backlink Experiment for the LISA mission
Lea Bischof, Melanie Ast, Jiang Ji Ho-Zhang et al. (+10 more)
Designed to detect gravitational waves in the lower-frequency band, the space mission LISA will open a new window to astronomy after its launch in the 2030s. Each LISA spacecraft houses two optical benches that require the exchange of a phase reference between them via an optical connection, called a Backlink. Here we present the construction and commissioning of an ultra-stable quasi-monolithic optical testbed to investigate different Backlink implementations: a direct fiber, a frequency-separated fiber, and a free-beam link, compared in the Three-Backlink Experiment. Dedicated
alignment techniques crucial for the construction of these optical benches are presented together with the development of a high-precision beam
alignment and measurement tool - a Calibrated Quadrant Photodiode Singleton. An upper limit for the performance of all three investigated Backlink schemes, as determined by initial experiments, can be set at a $15\text{pm}/\sqrt{\text{Hz}}$-equivalent level within the LISA band, spanning 0.1mHz to 1Hz. Our measurements were able to verify the successful construction and commissioning of this very complex interferometer as an interferometric laboratory testbed for LISA. We find no limitations due to the construction on the here reported performance levels. Our results can support the construction of high-precision metrology testbeds for space-based
laser interferometry for future gravitational wave or geodesy missions.
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All authors Lea Bischof, Melanie Ast, Jiang Ji Ho-Zhang, Nicole Knust, Daniel Penkert, Daniel Jestrabek, Jens Reiche, Thomas S. Schwarze, Katharina-Sophie Isleif, Oliver Gerberding, Gerhard Heinzel, Stefan Ast, Karsten Danzmann
Optics
Demonstrating sub-picometer non-reciprocity levels in the Three-Backlink Experiment for LISA
Jiang Ji Ho-Zhang, Melanie Ast, Lea Bischof et al. (+9 more)
The current planned space-based gravitational-wave detectors require a bidirectional optical connection, referred to as Backlink, between two adjacent optical benches to provide a mutual phase reference for the local interferometric measurements. However, if the Backlink shows asymmetry between the two propagation directions, the effective optical pathlengths of the counter-propagating beams can introduce a differential phase noise, called non-reciprocity, into the main interferometric measurement that will limit the achievable accuracy in time-delay interferometry (TDI) post-processing. Hence, it is important to understand the properties of the Backlink to ensure that it will not compromise the interferometric detection. The Three-Backlink Experiment (3BL), which consists of an optical test facility with two rotatable benches, was designed under the
Laser Interferometer Space
Antenna (LISA) framework to study the performance of three Backlink configurations: two fiber-based and one free-beam scheme. In this paper, we report recent experimental results from the 3BL. We describe the commissioning and the subsequent noise mitigation. We achieve a setup noise floor below $1\text{ pm}\sqrt{\text{Hz}}$ across most of the LISA measurement band, and provide an understanding of the current technical limitations. With this low-noise baseline, we measured the performance of the three Backlink implementations under non-rotational conditions. We show that all three Backlinks reach sub-picometer non-reciprocity levels across most of the frequency band, with the remaining part dominated by the mentioned testbed noise. This enabled us to conduct a preliminary study of the Backlink inherent noise, where we emphasized on the backscatter noise intrinsic to a straightforward fiber-based Backlink, as this is the current baseline for LISA.
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All authors Jiang Ji Ho-Zhang, Melanie Ast, Lea Bischof, Michael Born, Daniel Jestrabek, Stefan Ast, Katharina-Sophie Isleif, Oliver Gerberding, Thomas S. Schwarze, Jens Reiche, Gerhard Heinzel, Karsten Danzmann
Biological Physics
A Compact Incubation Platform for Long-Term Cultivation of Biological Samples for Nitrogen-Vacancy Center Widefield Microscopy
A. Pointner, D. Thalheim, S. Belasi et al. (+7 more)
Nitrogen-vacancy (NV) centers in diamond provide a versatile
quantum sensing platform for biological imaging through
magnetic field detection, offering unlimited photostability and the ability to perform long-term observations without photobleaching or phototoxicity. However, conventional stage-top incubators are incompatible with the unique requirements for NV widefield magnetometry to study cellular dynamics. Here, we present a purpose-built compact incubation platform that maintains precise environmental control of temperature, CO$_2$ atmosphere, and humidity while accommodating the complex constraints of NV widefield microscopy. The system employs a 3D-printed biocompatible chamber with integrated heating elements, temperature control, and humidified gas flow to create a stable physiological environment directly on the diamond sensing surface. We demonstrate sustained viability and proliferation of HT29 colorectal cancer
cells over 90 hours of continuous incubation, with successful
magnetic field imaging of immunomagnetically labeled
cells after extended cultivation periods. This incubation platform enables long-term cultivation and real-time monitoring of biological samples on NV widefield magnetometry platforms, opening new possibilities for studying dynamic cellular processes using
quantum sensing technologies.
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All authors A. Pointner, D. Thalheim, S. Belasi, L. Heinen, L. R. Carnell, C. Janko, R. Tietze, C. Alexiou, R. Schneider-Stock, R. Nagy
Plasma Physics
Influence of ion motion in a resonantly driven wakefield accelerator
Erwin Walter, John P. Farmer, Marlene Turner et al. (+1 more)
Several different schemes for
plasma wakefield acceleration using a train of drivers have been pursued, based on the resonant excitation of a
plasma wave. Since these schemes rely on the
plasma electron wave surviving for many periods, the motion of the
plasma ions can have a significant impact on the beam–
plasma interaction. In this work, simulations are used to study the impact of this ion motion on the development of the self-modulation of a long beam, directly applicable to recent experiments. It is shown that two related but distinct effects contribute to the suppression of the wakefield excitation: the loss of resonance between the drive beam and the
plasma wave it excites, and phase mixing due to transverse wavebreaking. Although only the latter has previously been investigated, we show that the two effects follow the same scaling with ion mass.
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All authors Erwin Walter, John P. Farmer, Marlene Turner, Frank Jenko
Biological Physics
CTransformer: Deep-transformer-based 3D cell membrane tracking with subcellular-resolved molecular quantification
Zelin Li, Guoye Guan, Xiu Xian et al. (+13 more)
Deep learning
segmentation and fluorescence imaging techniques allow the cellular morphology of living embryos to be constructed spatiotemporally. These development processes involve numerous molecules distributed at the subcellular scale, such as
cell adhesion (E-cadherin), which accumulate at
cell-
cell interfaces to regulate intercellular connection. However, quantifying molecular distributions within specific subcellular regions across the entire embryo, where
cell movement and molecular redistribution occur rapidly, is challenging due to the need for simultaneous
cell morphology reconstruction and lineage tracing due to photobleaching and phototoxicity. We report a
transformer-based pipeline, CTransformer, that establishes a 4D cellular morphology map before the 550-
cell (late) stage. CTransformer constructed 4D cellular morphology atlases, reaching 80% accuracy at the 550-
cell stage. Through this advanced architecture, we use only one channel to reconstruct
cell morphology and achieve
cell tracing. With each
cell's morphology as a reference, the distribution of specific molecules throughout the
cell body and at
cell interfaces can be quantitatively measured in another fluorescence channel. We apply this methodology to track E-cadherin during embryonic development of the worm Caenorhabditis elegans, from fertilization to gastrulation. Our results reveal that E-cadherin is tightly regulated across individual embryos, both within single
cells and at
cell-
cell interfaces, displaying an anterior-posterior gradient and
cell- and lineage-specific patterns. Furthermore, its spatiotemporal heterogeneity influences
cell mechanics and embryonic morphogenesis, helping explain how C. elegans achieves stereotypical developmental patterns at cellular resolution.
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All authors Zelin Li, Guoye Guan, Xiu Xian, Dongying Xie, Yiming Ma, Sicheng You, Zhen Zhu, Darrick Lee, Zirui Zhang, Zhuohen Ran, Chenwei Wang, Jianfeng Cao, Chao Tang, Zhaoke Huang, Zhongying Zhao, Hong Yan
Space Physics
NASA/NOAA MOU Annex Final Report: Evaluating Model Advancements for Predicting CME Arrival Time
M. L. Mays, P. J. MacNeice, A. Taktakishvili et al. (+11 more)
The purpose of this project was to assess improvements in CME arrival time forecasts at Earth using the Air Force Data Assimilative Photospheric Flux Transport (ADAPT) model driven by data from the Global Oscillation Network Group (GONG) ground observatories. These outputs are then fed into the coupled Wang-Sheeley-Arge (WSA) - ENLIL model and compared to an operational version of WSA-ENLIL (without ADAPT). SWPC selected a set of 38 historical events over the period of five years from 2012–2014 (33 events) and 2017–2019 (5 events). The overall three-year project consisted of multiple simulation validation studies for the entire event set (1292 simulations): (a)
benchmark single map (operational version prior to May 2019) (b) time-dependent sequence of GONG maps driving WSA-ENLIL with 4 different model settings (c) single test simulation of a time-dependent sequence of GONG maps driving ADAPT-WSA-ENLIL (d) single GONG map driving ADAPT-WSA-ENLIL (e) time-dependent sequence of GONG maps driving ADAPT-WSA-ENLIL. We report that for all 38 events, within each model version/settings combination, the CME arrival time error decreased by 0.2 to 0.9 hours when using a sequence of time-dependent zero-point corrected magnetograms compared to using single magnetogram input. Overall, for all events, when using the older uncorrected magnetograms, the CME arrival time error increased for all new model versions/settings combination compared to the
benchmark. Notably for the 5 events in the period 2017–2019 when more reliable zero-point corrected magnetograms were available, the ADAPT-WSA-ENLIL (median arrival realization) CME arrival time error decreased against all
benchmarks. In this report we also discuss replicating the operational model, challenges in detecting CME arrival in simulations, and comparing zero-point corrected and uncorrected magnetogram inputs.
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All authors M. L. Mays, P. J. MacNeice, A. Taktakishvili, C. P. Wiegand, J. Merka, E. T. Adamson, V. J. Pizzo, D. A. Biesecker, A. R. Marble, D. Odstrcil, C. J. Henney, C. N. Arge, S. I. Jones, S. Wallace
Optics
Leveraging Plasmonic Nanocavity Arrays Forming Metasurfaces to Boost Second Harmonic Generation due to Surface Effects
Sky Semone, Matthew J. Brandsema, Thang Hoang et al. (+1 more)
Plasmonic metasurfaces have emerged as a promising platform for enhancing a range of nonlinear optical processes, offering compact geometry and flexibility in light manipulation. Second order nonlinear processes, like second harmonic generation (SHG), typically require non-centrosymmetric
crystals to be realized. Here, we experimentally demonstrate enhanced SHG response by using a gold nanocavity array forming a plasmonic metasurface absorber where titanium dioxide (TiO2), a centrosymmetric dielectric material, with subwavelength thickness is deposited in the realized nanogaps. While such dielectric material has an extremely low second order nonlinear susceptibility, we observe 105-fold boosting in the nonlinear SHG process mainly due to the surface nonlinear susceptibility of the gold metal aided by the significant electric field enhancement that occurs in the nanogaps due to the formed nanocavity resonance. The experimental results obtained are theoretically explained with extensive and rigorous nonlinear simulations that consider all the bulk and surface linear and nonlinear material properties. The presented robust harmonic generation from an ultrathin plasmonic metasurface can be used in nonlinear and
quantum integrated photonic applications.
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All authors Sky Semone, Matthew J. Brandsema, Thang Hoang, Christos Argyropoulos
Optics
Polarization- and wave-vector selective optical metasurface with near-field coupling
Helene Wetter, Jan Wingenbach, Falk Rehberg et al. (+3 more)
Metasurfaces are a powerful tool for manipulating light using small structures on the nanoscale. In most meta-surfaces, near-field couplings are treated as unfavorable perturbations. Here, we experimentally investigate a structure consisting of sinusoidally modulated silicon waveguides where near-field coupling of local resonances leads to negative coupling, i.e. a negative coupling constant. This gives rise to wave-vector dependent eigenstates of elliptical, linear and circular polarizations. In particular, fully circular polarization states are not only present at a single point in momentum-space (k-space), but along a line. This circular polarization line, as well as a linear polarization line, emanates from a polarization degeneracy at the Dirac point. We experimentally validate the existence of these eigenstates and demonstrate the energy-, polarization- and wave-vector-dependence of this metasurface. By tuning the incident k-vector, certain polarization-energy eigenstates are strongly reflected allowing for uses in angle-tunable polarization filters and light sources.
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All authors Helene Wetter, Jan Wingenbach, Falk Rehberg, Wenlong Gao, Stefan Schumacher, Thomas Zentgraf
Classical Physics
On the Invariance of the Spacetime Interval
Marco Moriconi
We present a
geometric proof of the invariance of the relativistic spacetime interval based solely on the constancy of the speed of light, and the homogeneity and isotropy of spacetime. The derivation is based on a simple construction involving light rectangles, whose areas remain invariant across inertial frames. Based on this construction, we also derive the Lorentz transformations.
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Optics
Free-Running Ring Quantum Cascade Laser with 50 kHz Linewidth
Alexandre Parriaux, Ina Heckelmann, Mathieu Bertrand et al. (+3 more)
We report on the noise characterization of a free-running ring
quantum cascade
laser resonator emitting a single frequency mode around 7.7 $\mu$m. Using a gas
cell filled with N$_2$O as a frequency-to-voltage discriminator, we measured the frequency noise power spectral density of the
laser from which we extracted its linewidth. The results show a full width at half maximum close to 50 kHz at 1 s integration time, which represents at least a sixfold improvement compared to state-of-the-art
quantum cascade
lasers operating in a spectral region above 7 $\mu$m. We also demonstrate that such
lasers can be efficiently used for frequency modulation spectroscopy, which opens up new possibilities for high resolution metrology and spectroscopic applications in the mid-infrared.
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All authors Alexandre Parriaux, Ina Heckelmann, Mathieu Bertrand, Mattias Beck, Jérôme Faist, Thomas Südmeyer
Computational Physics · Cross-listed from stat.ML
From STLS to Projection-based Dictionary Selection in Sparse Regression for System Identification
Hangjun Cho, Fabio V.G. Amaral, Andrei A. Klishin et al. (+2 more)
In this work, we revisit dictionary-based sparse regression, in particular, Sequential Threshold Least Squares (STLS), and propose a score-guided library selection to provide practical guidance for data-driven modeling, with emphasis on SINDy-type
algorithms. STLS is an
algorithm to solve the $\ell_0$ sparse least-squares problem, which relies on splitting to efficiently solve the least-squares portion while handling the sparse term via proximal methods. It produces coefficient vectors whose components depend on both the projected reconstruction errors, here referred to as the scores, and the mutual coherence of dictionary terms. The first contribution of this work is a theoretical analysis of the score and dictionary-selection strategy. This could be understood in both the original and weak SINDy regime. Second, numerical experiments on ordinary and partial differential equations highlight the effectiveness of score-based screening, improving both accuracy and interpretability in dynamical system identification. These results suggest that integrating score-guided methods to refine the dictionary more accurately may help SINDy users in some cases to enhance their robustness for data-driven discovery of governing equations.
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All authors Hangjun Cho, Fabio V.G. Amaral, Andrei A. Klishin, Cassio M. Oishi, Steven L. Brunton
Optics
From Atomic Defects to Integrated Photonics: A Perspective on Solid-State Quantum Light Sources
Anuj Kumar Singh, Parul Sharma, Kishor Kumar Mandal et al. (+2 more)
Single-
photon emitters (SPEs) constitute a foundational resource for
quantum technologies, including secure communication, photonic
quantum computing, and emerging
quantum network architectures. A wide range of
quantum materials, from atom-like point defects in bulk
crystals to excitonic states in low-dimensional
semiconductors, now provide bright, coherent, and scalable sources of non-classical light. Meanwhile, advances in photonic integration have enabled efficient routing, filtering, and on-chip manipulation of these emitters. From this perspective, we survey and discuss the technological landscape in which solid-state emitters interface with
quantum sensing,
quantum communication,
quantum computation, and emerging photonic AI platforms. Further, we discuss the materials landscape underpinning modern single-
photon sources from the zero-dimensional, one-dimensional, two-dimensional and three-dimensional materials. Lastly, we highlight key integration pathways for these single-
photon emitters into scalable
quantum photonic systems.
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All authors Anuj Kumar Singh, Parul Sharma, Kishor Kumar Mandal, Lekshmi Eswaramoorthy, Anshuman Kumar
Fluid Dynamics · Cross-listed from cs.LG
SuperWing: a comprehensive transonic wing dataset for data-driven aerodynamic design
Yunjia Yang, Weishao Tang, Mengxin Liu et al. (+3 more)
Machine-learning surrogate models have shown promise in accelerating aerodynamic design, yet progress toward generalizable predictors for three-dimensional wings has been limited by the scarcity and restricted diversity of existing
datasets. Here, we present SuperWing, a comprehensive open
dataset of transonic swept-wing aerodynamics comprising 4,239 parameterized wing geometries and 28,856 Reynolds-averaged Navier-Stokes flow field solutions. The wing shapes in the
dataset are generated using a simplified yet expressive geometry parameterization that incorporates spanwise variations in airfoil shape, twist, and dihedral, allowing for an enhanced diversity without relying on perturbations of a baseline wing. All shapes are simulated under a broad range of Mach numbers and angles of attack covering the typical flight envelope. To demonstrate the
dataset's utility, we
benchmark two state-of-the-art
Transformers that accurately predict surface flow and achieve a 2.5 drag-count error on held-out samples. Models pretrained on SuperWing further exhibit strong zero-shot generalization to complex
benchmark wings such as DLR-F6 and NASA CRM, underscoring the
dataset's diversity and potential for practical usage.
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All authors Yunjia Yang, Weishao Tang, Mengxin Liu, Nils Thuerey, Yufei Zhang, Haixin Chen
Fluid Dynamics · Cross-listed from cond-mat.soft
Ingo Nitschke, Jan Magnus Sischka and Axel Voigt
Coarse-grained continuous descriptions for lipid
bilayers are typically based on minimizing the Helfrich energy. Such models consider the fluid properties of these structures only implicitly and have been shown to nicely reproduce
equilibrium properties. Model extensions that also address the dynamics of these structures are surface (Navier–)Stokes–Helfrich models. They explicitly account for membrane viscosity. However, these models also usually treat the lipid
bilayer as a homogeneous continuum, neglecting the molecular degrees of freedom of the lipids. Here, we derive refined models which consider in addition a scalar order parameter representing the molecular
alignment of the lipids along the surface normal. Starting from hydrodynamic surface
liquid crystal models, we obtain a hydrodynamic surface Landau–Helfrich model for asymmetric lipid
bilayers and a surface Beris–Edwards model for symmetric lipid
bilayers. The fully ordered case for both models leads to the known surface (Navier–)Stokes–Helfrich models. Besides more detailed continuous models for lipid
bilayers, we therefore also provide an alternative derivation of surface (Navier–)Stokes–Helfrich models.
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Optics · Cross-listed from cond-mat.mes-hall
Terahertz response of confined electron-hole pair: crossover between strong and weak confinement
Filip Klimovič, Jens Paaske and Tomáš Ostatnický
We analyze theoretically THz response of an electron-hole pair confined in a
semiconductor nanoparticle. We show that the interplay of particle confinement and electron-hole Coulomb interaction leads to significant renormalizations and energy shifts in THz linear conductivity of the nanocrystal. We develop and evaluate models in the strong and the weak confinement regime in order to correctly address the effect of Coulomb interaction. In the weak confinement regime, we find solutions of the problem in a form similar to the Wannier wavefunction whose spatial extent is reduced as a consequence of the confinement. The resulting states are scalable down to the strong confinement regime, enabling a theoretical description of the
exciton response for arbitrarily sized nanoparticles.
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Applied Physics
Sensor free, self regulating thermal switching via anomalous Ettingshausen effect and spin reorientation in DyCo5
Shibo Wang, Hiroki Tsuchiura and Nobuaki Terakado
We propose a sensor free, self regulating thermal switch that combines the anomalous Ettingshausen effect (AEE) with a temperature driven
spin reorientation transition (SRT) in the rare earth cobalt compound DyCo$_5$. Using density functional theory and the Kubo linear-response formalism, we compute the anomalous
Hall conductivity $\sigma_{xy}(\varepsilon)$ and the finite temperature anomalous Nernst conductivity $\alpha_{xy}(T)$ for two magnetization directions, magnetization parallel and perpendicular to the crystallographic c axis. While the intrinsic $\sigma_{xy}$ at the
Fermi level remains sizable for both orientations, $\alpha_{xy}$ exhibits an about two orders of magnitude contrast in the SRT temperature window. This contrast is consistent with the low temperature Mott relation through the energy slope $\partial_\varepsilon \sigma_{xy}(\varepsilon)\rvert_{E_{\mathrm F}}$ and is traced to strongly peaked Berry
curvature hot spots generated by
spin orbit coupling induced avoided crossings of Co $3d$ bands. Combining $\alpha_{xy}$ with longitudinal transport coefficients, we estimate device level metrics, namely the anomalous Nernst thermopower $S_{\mathrm{ANE}}$ and the Ettingshausen coefficient $\Pi_{\mathrm{AEE}}=T S_{\mathrm{ANE}}$, and demonstrate robust orientation controlled switching under a fixed in plane bias current. These results establish a materials based route to compact thermal control without external sensors or feedback electronics and provide a concrete example that the proposed principle can be realized in an existing ferromagnet.
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Optics
In-plane optically tunable magnetic states in 2D materials via tailored femtosecond laser driving
Shuang Liu, Oren Cohen, Peng Chen et al. (+1 more)
It is well established that light can control magnetism in matter, e.g. via the inverse Faraday effect or ultrafast demagnetization. However, such control is typically limited to magnetization transverse to light's polarization plane, or out-of-plane magnetism in 2D materials, while in-plane
magnetic moments have remained largely unexplored. This is due to the difficulty of generating electronic orbital angular momentum components within light's polarization plane. Here we overcome this limitation, demonstrating complete three-dimensional, all-optical control of magnetism in 2D materials. Using first-principles simulations, we show that a tailored, two-color
laser field can induce and steer
magnetic moments in any direction with the relative angle between the
laser polarizations playing a key parameter in coherent control. We analyze the physical mechanism of this process and show that it arises from a simultaneous breaking of time-reversal and spatial-inversion
symmetries in the two-color
laser. In-plane orbital moments are introduced via non-zero out-of-plane longitudinal photogalvanic currents enabled by broken inversion and mirror
symmetries, while time-reversal
symmetry breaking enables build-up of
spin-rotation processes through
spin-orbit coupling, translating the orbital moments to transient magnetism. Our findings demonstrate a full 3D coherent control scheme for transient
magnetic states on femtosecond timescales driven by tailored
lasers, and can be used to develop novel spectroscopies for magnetism, all-optical
magnetic switching for ultrafast spintronics, and novel information storage capabilities.
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All authors Shuang Liu, Oren Cohen, Peng Chen, Ofer Neufeld
Optics
Decoding Orbital Angular Momentum in Turbid Tissue-like Scattering Medium via Fourier-Domain Deep Learning
Avraham Yosovich, Anton Sdobnov, Alexander Doronin et al. (+3 more)
Structured light beams carrying orbital angular momentum (OAM), such as Laguerre-Gaussian modes, are promising tools for high-capacity optical communications and advanced biomedical imaging. However, multiple scattering in turbid media distorts their phase and amplitude, complicating the
retrieval of topological charge. We introduce VortexNet, a deep learning architecture that integrates an Angular
Fourier Transform to explicitly extract rotational
symmetries of OAM beams from experimentally acquired intensity and interference patterns. By transforming spatial information into the angular frequency domain, VortexNet isolates azimuthal features that persist despite scattering, enabling accurate topological charge classification even in complex optical environments. The results reveal that OAM-specific angular correlations can survive multiple scattering and be decoded through angular-domain learning. This establishes a new paradigm for structured-light analysis in complex medium, where deep learning enables the recovery of topological information beyond the reach of classical optics, paving the way for resilient photonic systems in communication, sensing, and imaging.
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All authors Avraham Yosovich, Anton Sdobnov, Alexander Doronin, Alexander Bykov, Igor Meglinski, Zeev Zalevsky
Physics and Society
Not all Chess960 positions are equally complex
Marc Barthelemy
We analyze strategic complexity across all 960 Chess960 (Fischer Random Chess) starting positions. Stockfish evaluations reveal a near-universal first-move advantage for White ($\langle E \rangle = +0.33 \pm 0.12$ pawns), indicating that the initiative is a robust structural feature of the game. To quantify decision difficulty, we introduce an information-based measure $S(n)$ that captures the cumulative information required to identify optimal moves over the first $n$ plies. This measure decomposes into White and Black contributions, $S_W$ and $S_B$, defining a total opening complexity $S_{\mathrm{tot}} = S_W + S_B$ and a decision asymmetry $A = S_B - S_W$. Across the ensemble, $S_{\mathrm{tot}}$ ranges from $2.6$ to $17.2$ bits, while $A$ spans from $-4.5$ to $+4.2$ bits (mean $\langle A \rangle = -0.26$), showing that openings are nearly evenly split between those that burden White and those that burden Black, with a slight average excess complexity for White. Standard chess (position \#518, RNBQKBNR) exhibits near-average total complexity and asymmetry, yet lies far from the configuration that jointly minimizes evaluation imbalance and decision asymmetry. These results reveal a highly heterogeneous Chess960 landscape in which small rearrangements of back-rank pieces can substantially alter strategic depth and competitive balance. The classical starting position–despite centuries of refinement–appears not as an extremum, but as one configuration among many in a broad statistical ensemble.
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History and Philosophy of Physics
Another 100 Years of Quantum Interpretation?
Karen Crowther
Interpretation is not the only way to explain a theory's success, form and features, and nor is it the only way to solve problems we see with a theory. This can also be done by giving a reductive explanation of the theory, by reference to a newer, more accurate, and/or more fundamental theory. We are seeking a theory of
quantum gravity, a more fundamental theory than both
quantum mechanics and general relativity, yet, while this theory is supposed to explain general relativity, it's not typically been thought to be necessary, or able, to explain
quantum mechanics – a task instead assigned to interpretation. Here, I question why this is. I also present a new way of assessing the various interpretations of
quantum mechanics, in terms of their heuristic and unificatory potential in helping us find a more fundamental theory.
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Atmospheric and Oceanic Physics
Climatological variability of a thunderstorm environment dataset in tropical and temperate regions
Andrew Dowdy, Andrew Brown, Todd Lane et al. (+1 more)
Spatiotemporal variations in thunderstorm occurrence frequency are considered here using an environmental
dataset derived from ERA5 reanalysis data. Interannual variability in the thunderstorm environments is examined for the period 1979-2023, with the standard deviation and coefficient of variation showing considerable spatial differences through the world. Atmospheric and oceanic modes of
climate variability account for some of this interannual variability, particularly for the El Nino-Southern Oscillation through tropical and maritime regions, as well as to a lesser degree for the Indian Ocean Dipole, Arctic Oscillation and Antarctic Oscillation. Long-term trends can also contribute to interannual variability, with results showing increases are more common than decreases in the thunderstorm environments through the study region over the period 1979-2023. However, considerable uncertainties in those trends are noted as is also suggested from some additional analysis of global
climate models, indicating that although more favorable thunderstorm environments might occur in a warming world, the estimated change over the period 1979-2023 is relatively small compared to the standard deviation in most locations. The study findings are intended to be complementary to other studies and contribute as part of a broader range of information available on thunderstorms and
climate variability.
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All authors Andrew Dowdy, Andrew Brown, Todd Lane, Mateusz Taszarek
Optics
Spectroscopic Ellipsometry for Two-Dimensional Materials: Methods, Optical Modeling, and Emerging Phenomena
Ersyzario Edo Yunata, Angga Dito Fauzi, Khoirunnisa Qoulan Aziza et al. (+4 more)
Spectroscopic ellipsometry (SE) has emerged as a powerful and non-destructive optical characterization technique for probing the complex dielectric properties of two-dimensional (2D) materials. This review provides a comprehensive overview of ellipsometric methods applied to atomically thin and multilayer van der Waals materials, including
graphene, transition metal dichalcogenides, and other emerging 2D systems. We discuss experimental configurations, optical modeling strategies, and challenges associated with reduced dimensionality, anisotropy, and substrate effects. Advanced techniques such as Mueller
matrix ellipsometry are highlighted for their capability to resolve in-plane and out-of-plane dielectric tensor components in anisotropic and low-
symmetry materials. Furthermore, we review recent discoveries enabled by ellipsometry, including extreme optical anisotropy,
hyperbolic dispersion, and tunable plasmonic responses in multilayer 2D materials. These findings establish spectroscopic ellipsometry as an essential tool for both fundamental studies and photonic device engineering based on two-dimensional materials.
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All authors Ersyzario Edo Yunata, Angga Dito Fauzi, Khoirunnisa Qoulan Aziza, Priscelia Arie Novita, Dian Meilanita Edi Sayom, Novita Aulia Rafi, Nabilah Mufidah
Applied Physics
Worldwide Scientific Landscape on Fires in Photovoltaic
Esther Salmerón-Manzano, David Muñoz-Rodríguez, Alberto-Jesus Perea-Moreno et al. (+2 more)
The rapid growth of photovoltaic (PV) technology in recent years called for a comprehensive assessment of the global scientific landscape on fires associated with PV energy installations. This study examines the scientific literature indexed in Scopus from 1983 to 2023. It reveals a striking increase in output since 2011, with nearly one hundred publications in the most recent year under review. This growth of interest has occurred in parallel with the global expansion of photovoltaics. The majority of studies in this field are classified as engineering, with 34% of publications in this area. The USA leads the way with over 160 publications, followed by China with 125. Two institutions in the USA are particularly prominent in this field: Sandia National Laboratories in New Mexico with 22 publications, and the National Renewable Energy Laboratory in Colorado with 16 publications. The second institution is the University of Science and Technology of China, which has published 17 articles on the subject. A close examination of the
evolution of keywords reveals a remarkable transformation in the scientific landscape over the past 10 years, from 2013 to 2023. The
evolution of keywords suggests a maturation in the understanding of fire risks associated with photovoltaic energy. A total of seven scientific communities have been identified in which these works are grouped according to their keywords. These include Fire and Energy Storage, PV faults, Fire resistance, Fire hazard, Fire detectors, Deep learning, and Fire safety. It has been found that fires caused by PV installations are not listed as a cause of fire starts. This should be taken into account when conducting preventive analyses of this potential danger, particularly in light of the possible development of agrivoltaics, where facilities will be mainly located in the natural environment.
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All authors Esther Salmerón-Manzano, David Muñoz-Rodríguez, Alberto-Jesus Perea-Moreno, Quetzalcoatl Hernandez-Escobedo, Francisco Manzano-Agugliaro
Atomic Physics · Cross-listed from cond-mat.quant-gas
Dipolar quantum gases: from 3D to Low dimensions
Yifei He, Haoting Zhen and Gyu-Boong Jo
Dipolar
quantum gases, encompassing atoms and molecules with significant dipole moments, exhibit unique long-range and anisotropic dipole-dipole interactions (DDI), distinguishing them from systems dominated by short-range contact interactions. This review explores their behavior across dimensions, focusing on
magnetic atoms in quasi-2D in comparison to 3D. In 3D, strong DDI leads to phenomena like anisotropic superfluidity,
quantum droplets stabilized by Lee-Huang-Yang corrections, and supersolid states with density modulations. In 2D, we discuss a new scenario where DDI induces angle-dependent Berezinskii-Kosterlitz-Thouless transitions and potential supersolidity, as suggested by recent experimental realizations of strongly dipolar systems in quasi-2D geometries. We identify key challenges for future experimental and theoretical work on strongly dipolar 2D systems. The review concludes by highlighting how these unique 2D dipolar systems could advance fundamental research as well as simulate novel physical phenomena.
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Atmospheric and Oceanic Physics
Large-scale patterns of small-scale vorticity interactions foster moist convection during cyclogenesis
Shruti Tandon, Apoorva Singh, B. N. Goswami et al. (+1 more)
The formation and intensification of a tropical cyclone is a complex phenomenon involving several feedback interactions between momentum and energetics of the storm, and across multiple spatio-temporal scales. Background vorticity interactions in the turbulent atmosphere play a crucial role in the formation of cyclones. How these vorticity interactions lead to convective organization and sustain a disastrous cyclonic
vortex amidst a turbulent atmosphere remains elusive. Moreover, what processes distinguish depressions that develop into a cyclone from those that do not? Here, we investigate the role of small-scale vorticity interactions in the background flow in sustaining large-scale organization during the emergence of a cyclone. We construct time-varying complex networks where geographical locations are nodes and connections between nodes represent short-time vorticity correlations. Only those nodes are connected that are in spatial proximity corresponding to sub-meso length scales. Each network is constructed for 29 hours of data; consecutive networks are separated by three hours, thus revealing the
evolution of local coherence in vorticity dynamics. We discover that small-scale vorticity interactions manifest as large-scale emergent patterns. Further, we establish that organized moist convection is significantly correlated to regions of locally coherent vorticity dynamics during the intensification of a depression that forms a cyclone; however, such correlations are not sustained during non-developing cases. Using modal analysis of time-evolving network connectivity, we show that these large-scale patterns are essentially large-scale modes of propagation of coherence in small-scale vorticity dynamics. We explain that such propagation is facilitated by moisture feedback at small-scales and self-organized patterns at large-scales.
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All authors Shruti Tandon, Apoorva Singh, B. N. Goswami, R. I. Sujith
Instrumentation and Detectors
An LNGS Mobile Neutron Detector (ALMOND): Mapping Ambient Neutron Background of Gran Sasso National Laboratory
Melih Solmaz, Klaus Eitel, Alfredo Davide Ferella et al. (+3 more)
In deep underground laboratories, environmental
neutrons, which are produced at the cavern walls, introduce a source of background to rare event searches. The flux and spectrum of the ambient
neutrons vary considerably with time and location. Precise knowledge of this background is necessary to devise shielding and veto mechanisms, thereby improving the sensitivity of the
neutron-susceptible underground experiments. ALMOND, currently in operation, is a low-flux mobile
neutron spectrometer developed for the LNGS underground laboratory to measure the ambient
neutron background of the entire facility. In this paper, an overview of the design, construction and calibration of ALMOND is given. Furthermore, the result of the first underground
neutron measurement is shown along with an outlook for future measurements and analyses.
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All authors Melih Solmaz, Klaus Eitel, Alfredo Davide Ferella, Felix Kratzmeier, Francesco Pompa, Kathrin Valerius
Physics and Society · Cross-listed from cs.LG
Beyond MMD: Evaluating Graph Generative Models with Geometric Deep Learning
Salvatore Romano, Marco Grassia and Giuseppe Mangioni
Graph generation is a crucial task in many fields, including network science and bioinformatics, as it enables the creation of synthetic graphs that mimic the properties of real-world networks for various applications. Graph Generative Models (GGMs) have emerged as a promising solution to this problem, leveraging deep learning techniques to learn the underlying distribution of real-world graphs and generate new samples that closely resemble them. Examples include approaches based on Variational Auto-Encoders, Recurrent Neural Networks, and more recently,
diffusion-based models. However, the main limitation often lies in the evaluation process, which typically relies on Maximum Mean Discrepancy (MMD) as a metric to assess the distribution of graph properties in the generated ensemble. This paper introduces a novel methodology for evaluating GGMs that overcomes the limitations of MMD, which we call RGM (Representation-aware Graph-generation Model evaluation). As a practical demonstration of our methodology, we present a comprehensive evaluation of two state-of-the-art Graph Generative Models: Graph Recurrent
Attention Networks (GRAN) and Efficient and Degree-guided graph GEnerative model (EDGE). We investigate their performance in generating realistic graphs and compare them using a
Geometric Deep Learning model trained on a custom
dataset of synthetic and real-world graphs, specifically designed for graph classification tasks. Our findings reveal that while both models can generate graphs with certain topological properties, they exhibit significant limitations in preserving the structural characteristics that distinguish different graph domains. We also highlight the inadequacy of Maximum Mean Discrepancy as an evaluation metric for GGMs and suggest alternative approaches for future research.
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