Mesoscale and Nanoscale Physics
Occupation-Driven Josephson Diode in a Symmetric Junction
Jianxiong Zhai, Zelei Zhang and Jiawei Yan
We propose a Josephson diode mechanism in which nonreciprocity arises not from a conventional asymmetric Andreev spectrum but from nonequilibrium occupation of the current-carrying states engineered by attached reservoirs. We realize this mechanism in a double-
quantum-dot junction, where a phase-textured nonlocal reservoir acts as a
quantum Zeno selector: rapid dissipation freezes out the bright state directly coupled to the jump operator $L$, while preserving an orthogonal dark Andreev channel whose supercurrent remains comparable to that of the lossless junction. In the infinite-gap limit, the steady-state current factorizes as $I_{\rm ss}=I_A P_\gamma$, so that even when the Andreev current $I_A$ is strictly reciprocal, the phase asymmetry of $P_\gamma$ alone can produce a Josephson diode effect through reservoir engineering. We further show that local Coulomb repulsion can drive the system toward a nearly ideal diode regime via a dark-pair resonance. Using Keldysh-Lindblad calculations, we demonstrate that our results remain robust for realistic junctions with a finite superconducting gap and dissipation.
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Medical Physics
Constrained estimation of rotational invariants of the cumulant expansion (RICE) for rapid tensor-valued diffusion MRI
Jinyang Yu, Oliver Gödicke, Frederik B. Laun et al. (+10 more)
Purpose: To complement 1.5-minute measurements of common tensor-valued
diffusion MRI (dMRI) markers with rapid constrained fitting. Methods: Fast dMRI protocols for obtaining rotational invariants of the cumulant expansion (RICE) were paired with constrained weighted linear least squares (CWLLS) to stabilize the more fragile WLLS fit. A compact constraint set was formulated, including a novel mean-dependent upper bound on total diffusional variance. Evaluation used
diffusion tensor distribution (DTD) simulations, healthy-volunteer data with a resolution-dependent SNR experiment, and a glioma patient
dataset. A 5-minute q-space trajectory imaging (QTI) protocol served as a reference. Results: Across experiments, CWLLS reduced unphysical estimates and fit outliers in parameters such as microscopic FA and isotropic diffusivity variance. In simulations, it narrowed error distributions most clearly in the CSF-dominant case, while some metrics showed a bias-variance trade-off. In vivo, CWLLS removed negative variance estimates, truncated out-of-bounds tails, and reduced artifacts in fluid-contaminated voxels while preserving anatomical contrast. It also retained more stable maps than WLLS at higher resolution, although both
estimators degraded in the lowest-SNR setting. Notably, the new mean-dependent variance bound was violated in 15.4% of voxels in the patient
dataset, accounting for nearly half of the 32.7% that violated at least one constraint. Healthy-volunteer benchmarking showed that CWLLS completed in under 30 seconds. The constrained QTI fit required 72 minutes, making CWLLS 160 times faster. Conclusion: CWLLS for fast RICE yielded high-quality parameter maps at an online-ready computational cost. This may enhance the reliability of dMRI tissue characterization and strengthen the path toward clinical translation.
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All authors Jinyang Yu, Oliver Gödicke, Frederik B. Laun, Obada T. Alhalabi, Iris A. Kohler, Jürgen Hesser, Sandro M. Krieg, Bogdana Suchorska, Heinz-Peter Schlemmer, Mark E. Ladd, David Bonekamp, Johann M. E. Jende, Tristan A. Kuder
Quantum Physics
The Find Rows and Columns and Decode algorithm for quantum expander codes
Dimiter Ostrev
A new adaptation of the Find Erasures and Decode
algorithm from classical to
quantum expander codes is presented. It runs in linear time and is parallelizable to logarithmic depth. Compared to Small Set Flip and Small Set Find, the new
algorithm avoids the overhead of considering the subsets of stabilizer generators, requires less expansion and corrects more errors.
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Physics and Society
Distinct routes to phase transitions in spatial activation systems
Jialu Zhang, Guanyu Zhang, Leyang Xue et al. (+1 more)
Threshold-driven activation governs a wide range of collective phenomena, yet the microscopic origins of its phase transitions in spatial systems remain unresolved. Here, we show that spatial activation systems undergo multiple distinct routes to phase transitions, controlled by a single parameter—the interaction range. We uncover a unified phase diagram featuring continuous, first-order, and mixed-order transitions, and demonstrate that the two abrupt transitions arise from fundamentally different mechanisms: nucleation-driven front propagation and critical branching. These routes exhibit distinct dynamical scaling, establishing a direct link between microscopic activation dynamics and macroscopic critical behavior. We further identify a metastable phase in which global activation cannot be achieved by random activation alone, but can be triggered by localized seeds. In this regime, the critical activation
nucleus remains finite and independent of system size, implying that arbitrarily large systems can remain stable under random perturbations yet highly vulnerable to localized triggers. The onset of this phase is abrupt, revealing an extreme sensitivity of collective dynamics to small parameter changes. These results establish a mechanistic framework for phase transitions in spatial activation systems and reveal how microscopic perturbations can trigger macroscopic cascades.
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All authors Jialu Zhang, Guanyu Zhang, Leyang Xue, Peng-Bi Cui
Quantum Physics
Strong Converse Exponent of Quantum State Merging
Mario Berta, Hao-Chung Cheng, Roberto Rubboli et al. (+1 more)
We determine the strong converse exponent for the
entanglement cost of
quantum state merging, showing that it is characterized by the optimized $\alpha$-$z$ conditional Rényi
entropies with $z=\alpha/2\in[1/2,1]$. This contrasts with the sandwiched conditional Rényi
entropies that typically govern strong converse exponents in
quantum information theory. As a consequence, we derive the strong converse exponent of the partially smoothed conditional min-
entropy in purified distance. This exponent is governed by club-sandwiched conditional
entropies, whereas global smoothing leads to a sandwiched expression.
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All authors Mario Berta, Hao-Chung Cheng, Roberto Rubboli, Marco Tomamichel
Strongly Correlated Electrons
Multi-orbital physics in inverse Lieb lattice altermagnets
Mercè Roig, Jannik Gondolf, Andreas Kreisel et al. (+2 more)
The inverse Lieb
lattice has recently emerged as a promising platform for altermagnetism, with several materials with this structure proposed as $d$-wave altermagnetic candidates. Here, we develop a
symmetry-based microscopic
Hamiltonian for these materials that includes both sublattice and orbital degrees of freedom, going beyond the sublattice-only minimal models that have been extensively used to study such altermagnets. We apply these models to examine multi-orbital electron correlation physics in the vanadium oxychalcogenide family altermagnets, which contain dominant $xy$ and $xz/yz$ orbitals character at the
Fermi level in the altermagnetic state. We demonstrate that $xy$ orbitals are crucial to stabilize the altermagnetic state observed within a single V$_2$O layer, and altermagnetic order in the $xz/yz$ orbitals is induced through Hund's coupling. Additionally, we show that these multi-orbital models reveal topological regimes in which topological edge states are naturally orbital selective.
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All authors Mercè Roig, Jannik Gondolf, Andreas Kreisel, Brian M. Andersen, Daniel F. Agterberg
High Energy Astrophysical Phenomena
Testing Narrow-jet Gamma-Ray Bursts as Sources of Ultrahigh-Energy Cosmic Rays
Saikat Das, Soebur Razzaque, Justin D. Finke et al. (+1 more)
Gamma-ray bursts (GRBs) have long been considered candidate sources of ultrahigh-energy
cosmic rays (UHECRs) due to their large energy release and relativistic
outflows. The detection of multi-TeV $\gamma$-rays from GRB~221009A and its rarity have renewed interest in this connection and motivate considering an additional narrow-jet long GRB population in the local Universe. We investigate whether such a local narrow-jet population can contribute to the observed diffuse UHECR energy spectrum. We also examine the associated cosmogenic
neutrino and cascade $\gamma$-ray emissions to assess the multimessenger viability of this scenario. We fit the observed UHECR spectrum and mass composition data using three source-
evolution models: a uniform comoving source emissivity, a standard-jet GRB population tracing the
star formation rate (SFR), and a standard + narrow-jet GRB population tracing SFR. We propagate a mixed-composition UHECR injection and calculate the cosmogenic
neutrino and cascade $\gamma$-ray fluxes. The standard + narrow jet model fits the observed UHECR spectrum and composition, with the highest-energy flux dominated by the narrow-jet population confined to $z\le z_{\max,*}\simeq0.36$. This low-
redshift dominance lowers the cosmogenic
neutrino flux compared to the standard-jet GRB population. For the narrow-jet GRB population, the fit implies a
baryon loading factor $\xi_{\rm CR}^{\rm nj}\simeq10$. Such a locally enhanced long-GRB population can therefore explain the highest-energy UHECR flux without violating current multimessenger constraints. Future UHE searches can further probe this scenario through the associated cosmogenic fluxes.
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All authors Saikat Das, Soebur Razzaque, Justin D. Finke, Siyao Xu
Mesoscale and Nanoscale Physics
Terahertz anomalous Hall effect in magnetic Weyl semimetal Co$_3$Sn$_2$S$_2$
Ashutosh Singh, Hongjing Xu, Xielin Wang et al. (+6 more)
Time-reversal-
symmetry-broken Weyl semimetals are known to have at least two nodes in their electronic band structure, separated in momentum space and acting as sources and sinks of Berry
curvature. This gives rise to a transverse
Hall conductivity, known as the anomalous
Hall effect (AHE), which, in the simplest two-node picture, is proportional to the momentum-space separation between the nodes in the zero frequency limit. In the recently discovered Weyl semimetal $\mathrm{Co_3Sn_2S_2}$, a
giant AHE has been observed. However, experimental investigations in the low-energy regime, which directly probe quasiparticle excitations near the Weyl nodes, remain limited. Here, we present a systematic study of the intrinsic low-energy gyrotropic optical response of $\mathrm{Co_3Sn_2S_2}$ using terahertz spectroscopy combined with semianalytical calculations based on a physically intuitive effective model. Our results provide a robust and transparent explanation of the observed magnetooptical phenomena in terms of intrinsic gyrotropy arising from momentum-space separation of the Weyl nodes. Furthermore, quantitative comparison between experiment and theory places stringent constraints on the material parameters.
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All authors Ashutosh Singh, Hongjing Xu, Xielin Wang, Kohei Fujiwara, Atsushi Tsukazaki, Shengxi Huang, Andrey Baydin, Junichiro Kono, Alexey Belyanin
Nuclear Theory
Scale Invariance and Compact Star Matter
Hyun Kyu Lee and Won-Gi Paeng
We present discussions on the possibility of emerging hidden scale
symmetry, as a pseudo-conformal phase in super dense baryonic matter, using the velocity of sound as a criterion for a scale
symmetry window in hadronic dense matter. In the density dependent mean field approach à la Brown-Rho scaling, it has been observed that the interplay between vector
mesons and $ \chi$, one of the strongly correlated effects between
hadrons, is nontrivial such that the trace of the energy momentum tensor becomes density-independent in the super dense regime and the sound velocity approaches the conformal sound velocity for the pseudo-conformal phase. It is suggested that in the pseudo conformal phase the rearrangement terms induced by density dependent couplings do not spoil the hidden scale
symmetry in the compact
star matter. We elaborate further on the astrophysically observable quantities of the compact
stars and the implications for the parity doubling and the
quark-
hadron transitions.
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Instrumentation and Methods for Astrophysics
Optimal transport regularized dynamic radio interferometric reconstruction
Andy Nilipour, Kotaro Moriyama, Shiro Ikeda et al. (+2 more)
We propose a new technique for dynamic
video reconstruction of
radio interferometric data using the optimal transport (OT) distance as a regularizer within the regularized maximum likelihood (RML) framework. Compared to other commonly used regularization terms in RML and related prior-based approaches, the OT distance more naturally captures information including physical motion and promotes coherent dynamics. This property makes the OT regularization particularly suitable for dynamic imaging of astrophysical phenomena on minute timescales. We perform a series of tests on simulated very long baseline interferometric (VLBI) observations of Sagittarius A$^\ast$ (SgrA*), the supermassive black hole at the
Galactic Center, with the Event Horizon
Telescope (EHT), using both
geometric and general relativistic magnetohydrodynamic models. We demonstrate that adding an OT regularization term yields significant improvements in dynamic reconstructions compared to those without it, as quantified by better recovery of orbital motion and higher dynamic cross-correlation metrics. Continued developments in OT theory across various fields, proposed extensions to the EHT network, and broad applicability to other VLBI networks make it so that OT regularization for dynamic
radio interferometric reconstructions will continue to be utilized and improved in the future.
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All authors Andy Nilipour, Kotaro Moriyama, Shiro Ikeda, Kazunori Akiyama, Mareki Honma
Mathematical Physics
Multiscale Loop Vertex Expansion for Cumulants, the $\phi^4_2$ Model
Vincent Rivasseau
We consider the $\phi^4_2$ model. It has been called the simplest non- trivial super-renormalisable model. The method we use is the multiscale loop vertex expansion, an improvement of constructive field theory. We prove analyticity and Borel summability of the cumulants up to a finite order.
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High Energy Physics (Phenomenology)
Exploring $Z/\gamma$-mediated heavy FCNCs at the FCC-ee
Abhik Sarkar, Subhajit Kala, Amir Subba et al. (+1 more)
The
flavor structure of the Standard Model (SM) remains one of the most compelling questions in particle physics, with the third generation being particularly intriguing due to its significantly larger masses and comparatively less precisely measured properties. These features make third-generation
flavor transitions particularly interesting in context of search for physics beyond the SM. In this work, we investigate
flavor-violating transitions between the third and the first two generations, mediated by the neutral gauge
bosons ($Z/\gamma$), within the framework of the SM Effective Field Theory (SMEFT), using dipole and
Higgs-current operators. We determine the optimal sensitivities using the optimal observable technique (OOT) at different center-of-mass energies of the upcoming Future Circular
Collider in the $e^+e^-$ mode (FCC-ee). We further derive complementary constraints on the relevant SMEFT operators from low-energy
flavor-violating observables and heavy
fermion decay channels. Our analysis also reveals characteristic interference patterns among the dipole contributions, which depend on the underlying
flavor transition and exhibit distinct behavior between the $Z$ pole and higher-energy FCC-ee stages. The FCC-ee provides a complementary and direct probe of
flavor-violating interactions at the electroweak scale, with the projections showing improved sensitivity for several interactions and comparable sensitivity to existing
flavor constraints for several others. This highlights the importance of a systematic assessment across the different FCC-ee energy stages, which provides a comprehensive picture of its potential to explore
flavor-violating phenomena and its complementarity with low-energy
flavor experiments.
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All authors Abhik Sarkar, Subhajit Kala, Amir Subba, Yu Shi
Chemical Physics
ElemCo.jl: A Julia package for electron-correlation methods
Daniel Kats, Charlotte Rickert, Thomas Schraivogel et al. (+3 more)
We present ElemCo.jl, an open-source Julia package for molecular electronic structure and properties calculations with a particular emphasis on Coupled Cluster and Distinguishable Cluster methods. The package provides a high-level, macro-based user interface which makes routine calculations accessible to users with no prior Julia experience. A newly developed visualizer, JLmol, assists in the graphical preparation of ElemCo.jl input files and displays results such as molecular orbitals. ElemCo.jl offers restricted closed-shell and unrestricted variants of state-of-the-art electron-correlation methods such as FCI, MP2, CCSD(T) as well as EOM-CCSD and the DC methods DCSD and DC-CCSDT. In addition to traditional approaches, ElemCo.jl provides recently developed methods that are currently unique to the package. These include tensor-decomposed implementations of DCSD and DC-CCSDT (SVD-DCSD and SVD-DC-CCSDT) as well as two-determinant and fixed-reference CC and DC methods. For excited-state calculations, ElemCo.jl also offers EOM-DCSD, which is benchmarked in this work against CC3 on the QUEST3
benchmark set, alongside EOM-CCSD. Furthermore, both ground and excited states, including those of multireference character, can be treated using CIPHI - an efficient selected Configuration Interaction (CI) approach employing a CIPSI/Heat-Bath-CI-based
algorithm. Users can directly invoke internal functions from the input file, enabling them to test and compose new methods without the need to modify ElemCo.jl's source code. Also, ElemCo.jl can be readily interfaced with external
quantum chemistry codes through the Fcidump format, for example as the high-level solver for transcorrelated
Hamiltonians, periodic embedded fragments, etc. We provide a detailed overview of ElemCo.jl's methodological repertoire and discuss its technical details and implementation, performance, interfaces, and usage.
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All authors Daniel Kats, Charlotte Rickert, Thomas Schraivogel, Kristoffer Simula, Denis Usvyat, Fangcheng Wu
Quantum Physics
Conditional contraction coefficients and their applications to quantum networks
Christoph Hirche, Ian George, Theshani Nuradha et al. (+1 more)
Contraction coefficients quantify the loss of distinguishability induced by a channel and provide a strong form of the data-processing inequality. While standard contraction coefficients ignore auxiliary
quantum systems, existing extensions based on complete contraction coefficients require the compared states to have identical reference marginals. In this work, we introduce conditional contraction coefficients, a novel family that incorporates arbitrary
quantum reference systems by subtracting the distinguishability already present in the reference system. We develop a general framework for contraction coefficients with such
quantum side information, including the corresponding strong-data-processing-inequality (SDPI) constants, expansion coefficients, and relative contraction coefficients. For the trace distance, we show that the optimization can be restricted to orthogonal input states. For the
quantum relative
entropy, we prove that its conditional contraction coefficient is exactly equal to the contraction coefficient of the conditional mutual information, extending the classical correspondence between relative-
entropy contraction and mutual-information contraction to the setting with
quantum side information. More generally, we identify structural properties of divergences required for these results and discuss extensions beyond the relative
entropy. These results establish a unified framework for analyzing information contraction in
quantum network settings, where
quantum side information and distributed correlations are intrinsic features of the information-processing task. Applications include an extension of the Polyanskiy-Wu bounds on mutual information contraction, new perspectives on mixing times, and fundamental limits on
quantum memories.
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All authors Christoph Hirche, Ian George, Theshani Nuradha, Mark M. Wilde
Solar and Stellar Astrophysics
NGTS clusters survey - VI: Stellar rotation in seven young open clusters within the PLATO LOPS2 field
Alexander Hughes, Edward Gillen, Matthew Battley et al. (+18 more)
We present NGTS measurements of rotation period distributions for FGKM
stars in seven young open clusters spanning ~40–700 Myr within PLATO's first long-stare LOPS2 field. We measure 1063 rotation periods, of which 479 are newly analysed as part of cluster specific rotation studies, whilst 63 are unique periods not reported in the recent TESS All-Sky Rotation Survey. Of the 1063 rotation periods, 285 are identified as likely binary or higher order multiple systems using colour-magnitude diagrams and
Gaia astrometry. These are the first comprehensive rotation period distributions for Trumpler 10, NGC 2451B and Alessi 3, while extending existing distributions for NGC 2451A, NGC 2516, Collinder 135 and IC 2391, to create a fuller picture on the rotation state of young
stars in PLATO's LOPS2 field. We find that main-sequence
solar-mass
stars in the ~40 Myr old NGC 2451B cluster, form a slow sequence that can be distinguished from their counterparts at ~70–80 Myr, thereby significantly reducing the age at which young
stellar groups can be relatively aged via their rotation sequences. We also observe stalled
spin down from the age of NGC 2451A to at least that of NGC 2516 (~70–150 Myr) at masses $\gtrsim1$ $M_{\odot}$, supporting previous predictions that angular momentum redistribution and removal should result in a wave of stalled
spin down that propagates as a function of both mass and age. Finally, we provide a new age estimate for Alessi 3 of 687$\pm$106 Myr using differential gyrochronology age dating.
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All authors Alexander Hughes, Edward Gillen, Matthew Battley, Deepak Chahal, Beatrice Caccherano, David Anderson, Ioannis Apergis, Daniel Bayliss, Matthew Burleigh, Jorge Fernández Fernández, Michael Goad, George Harvey, James S. Jenkins, Alicia Kendall, James McCormac, Jose Moyano, Gavin Ramsay, Suman Saha, Jose Vines, Richard G. West, Peter J. Wheatley
Quantum Physics
Dynamics and spectra of open quantum systems coupled to anharmonic environments
Kian Damezin, Brendon W. Lovett, Erik M. Gauger et al. (+1 more)
In open
quantum systems, the environment is typically modelled as a collection of harmonic oscillators, whereas realistic environments often exhibit unique non-Markovian effects due to the anharmonicity of the environment. Here we present a framework for modelling anharmonic environments in open
quantum systems numerically exactly, in which, via a matching criterion, we map the anharmonic environment onto an effective harmonic one. This results in an effective spectral density that is a collection of shifted bare spectra arising from the non-equidistant energy gaps of the anharmonic environment, along with a unique zero-frequency term that effectively acts as static disorder on the system. This is due to the non-zero variance of the diagonal of the bath coupling operator. In tandem, we develop a framework for investigating the effects of environments comprising a few damped anharmonic modes where the matching criterion fails to work due to the non-Gaussianity of the environment. For both continuous and discrete damped anharmonic environments, this work investigates their unique influence on the system's dynamics, including enhanced non-Markovianity compared to a harmonic approximation, novel effects in the absorption spectrum, and the potential for anharmonic environments to enhance energy transport.
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All authors Kian Damezin, Brendon W. Lovett, Erik M. Gauger, Adam Burgess
Materials Science
Data-efficient crack quantification in lithium-ion cathodes using foundation model transfer
Thorsten Tegetmeyer-Kleine, Thomas Schmitt, Phillip Aquino et al. (+3 more)
Battery lifetime is central to sustainable electrification, yet the particle cracking that drives lithium-ion cathode aging is hard to measure: quantitative microscopy of this degradation is bottlenecked by annotation, because each destructive electron-microscopy cross-section spans hundreds of megapixels and pixel-level expert labelling requires hours per image. We show that a frozen self-supervised
vision-
transformer encoder, combined with a lightweight trainable decoder and iterative model-assisted annotation, turns this sparse labelling budget into population-scale degradation measurements. Applied to three 120-megapixel NMC cathode cross-sections representing initial, cycled-aged and calendar-aged states, the framework distinguishes intragranular cracks from early- and late-stage intergranular cracks and yields per-particle distributions of crack width, tortuosity and area fraction. Late intergranular crack coverage reaches 4.6% in the cycled sample versus 0.5% in the initial and calendar-aged samples, forming more tortuous, higher-coverage networks, consistent with degradation from repeated electrochemical cycling rather than elevated-temperature storage alone. A single destructive image yields the population-level statistics needed for lifetime-extending design, aging assessment and second-life decisions.
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All authors Thorsten Tegetmeyer-Kleine, Thomas Schmitt, Phillip Aquino, Christiane Rahe, Dirk Uwe Sauer, Weihan Li
Applied Physics
Diamond quantum-sensing platform with integrated boron-doped diamond microwave antenna and thermometer
Masahiro Ohkuma, Ryo Matsumoto, Shintaro Adachi et al. (+5 more)
Wide-field nitrogen-vacancy (NV)
magnetic imaging at cryogenic temperatures requires microwave excitation and reliable knowledge of the temperature near the sensing region. Here, we report an integrated diamond
quantum-sensing platform combining an ensemble of NV centers with a boron-doped diamond (BDD) microwave
antenna and thermometer formed on the same diamond substrate. The BDD
antenna provides microwave excitation for optically detected
magnetic resonance measurements, and the BDD thermometer monitors the thermal environment near the NV sensing region. The BDD thermometer detected
laser-induced local heating that was not clearly resolved by a stage-mounted thermometer. Using this platform, we imaged the temperature-dependent Meissner response of multiple cuprate
superconductors while recording the temperature. These results demonstrate that the integrated BDD–NV platform provides a practical approach for cryogenic wide-field
magnetic imaging with integrated microwave delivery and local thermometry.
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All authors Masahiro Ohkuma, Ryo Matsumoto, Shintaro Adachi, Shinobu Onoda, Kensei Terashima, Takao Watanabe, Yoshihiko Takano, Keigo Arai
Chemical Physics
Franson-Interferometric Bounds on Entangled Two-Photon Absorption
Albin Hedse, Sankaran Ramesh, Luis Matheis et al. (+7 more)
Entangled
photons offer
quantum correlations with no classical analogue. In entangled pair two-
photon absorption (ETPA), absorption rate is predicted to scale linearly rather than quadratically with
photon flux, promising molecular excitation at fluxes far below the classical threshold. Reported ETPA cross sections nevertheless vary widely across experiments, largely since the observable, the differential of the transmitted flux or weak fluorescence, is difficult to separate from scattering and linear losses. We present a method which uses Franson interference to study entangled two-
photon absorption through delay-dependent coincidence measurements on dye molecules. Applying the method to Rhodamine 6G, we observe a small asymmetry in the Franson interference envelope and obtain a model-derived effective cross section of approximately 2.1 E(-21) centimeter squared for Rhodamine 6G. However, the estimated systematic uncertainty does not allow a definitive ETPA assignment. Instead, the experiment establishes a quantitative bound on the ETPA response and provides a background-free
benchmark for future measurements.
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All authors Albin Hedse, Sankaran Ramesh, Luis Matheis, Sebastian Gstir, Andreas Wacker, Gregor Weihs, Robert Keil, Qi Shi, Amitav Sahu, Tõnu Pullerits
Geophysics
Quantifying the effects of nickel on Earth's inner-core nucleation
Jiahui Zhai, Liangrui Wei, Chen Gao et al. (+1 more)
The formation of Earth's solid inner core marks a major transition in the thermal and chemical
evolution of the deep Earth, yet its origin remains paradoxical, as initial nucleation appears to require unrealistically large undercooling in the outer core. Here, we use atomistic simulations to quantify how Ni affects this process under inner-core conditions. While Fe-Ni
alloys preserve strong thermodynamic competition between the hcp and bcc phases, the bcc phase consistently forms smaller critical
nuclei and has lower nucleation barriers than hcp. Increasing Ni content in the melts further lowers the nucleation barrier and shortens the nucleation waiting time. Local chemical fluctuations also strongly affect the macroscopic nucleation rate. Combining these effects, bcc nucleation in Fe80Ni20 reaches about 250 K of undercooling, approaching geophysical constraints. We demonstrate that Ni enrichment, bcc nucleation, and chemical heterogeneity substantially narrow the inner-core nucleation paradox.
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All authors Jiahui Zhai, Liangrui Wei, Chen Gao, Yang Sun
Quantum Physics
Optimal Gaussian networks for private distributed quantum sensing
Hanbom Yoo, Byeongyun Yang, Hyunwoo Yoo et al. (+1 more)
Private distributed
quantum sensing aims to estimate an authorized collective parameter while preventing independent estimation of individual local parameters. Here, we analytically characterize Gaussian
quantum networks satisfying this perfect local
privacy condition. Using a graph representation of the Gaussian pairing
matrix, we show that two-mode squeezed
vacuum states constitute the essential building blocks of
privacy-preserving Gaussian states. We then analytically derive the optimal sensitivity under perfect local
privacy and determine a Gaussian probe that achieves Heisenberg scaling with respect to both the
photon number and the number of sensing modes. Using local homodyne measurements and maximum-likelihood estimation, we numerically verify
quantum-enhanced sensitivity beyond the shot-noise limit while preserving perfect local
privacy. We further show that the local-
privacy condition is preserved under arbitrary phase-independent
quantum channels, including optical loss. Our results provide a general framework for constructing and optimizing
privacy-preserving continuous-variable
quantum sensing networks.
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All authors Hanbom Yoo, Byeongyun Yang, Hyunwoo Yoo, Seongjin Hong
Strongly Correlated Electrons
3D- (H-theta-phi) magnetic phase diagram of antiferromagnetic metal GdB6 with electron and lattice instability
A. N. Azarevich, A. V. Bogach, T. F. Garipova et al. (+10 more)
The origin of charge transport and magnetization anisotropy was studied in GdB6, an
antiferromagnetic (AF) metal (Néel temperature TN ~ 15.5 K) with cubic
lattice and Gd S-type
magnetic ions. Both small static Jahn-Teller distortions and nanoscale electronic instabilities (dynamic charge stripes) were found in precise low temperature X-ray diffraction measurements. The detailed
magnetic field (H) vs temperature (T) phase diagrams were constructed with two main
magnetic phases AF(I) and AF(II). Using the angular phi-dependences of magnetoresistance and magnetization, impeller-type patterns of the H-phi
magnetic phase diagrams in the (110) and (111) planes were found at helium temperatures, which included the AF phases I and II separated from each other by radial and circular boundaries. The results argue in favor of the important role of the
spin density wave 5d- component in the
magnetic structure of AF(II) state. Charge fluctuations in stripes are proposed to be responsible for the suppression of the Ruderman-Kittel-Kasuya-Yoshida (RKKY) indirect exchange between the first and second neighboring Gd3+ ions located along the <100> and <110> directions. These dynamic charge stripes and vibrationally coupled Gd-Gd pairs produce unusual anisotropy of charge scattering and the impeller-type diagrams in GdB6 with S-type
magnetic ion.
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All authors A. N. Azarevich, A. V. Bogach, T. F. Garipova, V. V. Voronov, M. Rajnak, S. Gabani, K. Flachbart, N. B. Bolotina, O. N. Khrykina, V. M. Gridchina, A. Yu. Tsvetkov, S. Yu. Gavrilkin, N. E. Sluchanko
Earth and Planetary Astrophysics
Narrow-Shell Stochasticity in Source-Sink Models of the Low Earth Orbit Environment
Jaewon Choi, Souvik Dhara and Harsha Honnappa
Deterministic source-sink models are widely used to assess the long-term
evolution, capacity, and sustainability of the low Earth orbit (LEO) environment. These models propagate shell-averaged populations through ordinary differential equations (ODEs), relying on individual collision, disposal, and decay events to average out within sufficiently large altitude shells. As constellation traffic is increasingly organized into kilometer- and sub-kilometer-scale shells, this averaging assumption becomes strained. We formulate the multi-shell, multi-species LEO environment as a Markov jump process and, from this formulation, recover the conventional source-sink ODE as a large-volume limit and derive a
stochastic differential equation (SDE) approximation whose fluctuations scale as V^{-1/2} in the per-shell volume V. The
diffusion approximation is validated against an exact discrete-event simulation of the underlying jump process. Sweeping V at fixed spatial density over the 450-800 km band, we find that the two descriptions agree at shell volumes comparable to those used in established source-sink models but diverge as shells narrow. At the finest shell volume considered, the mean debris population reaches roughly 4.5 times the ODE prediction, with several realizations undergoing runaway growth absent from the ODE trajectory. This departure is driven by nonlinear collision terms, through which population variance and covariance raise expected collision rates, generating further debris and reinforcing the collision-debris feedback. Narrow-shell stochasticity thus both widens the outcome distribution and shifts the expected trajectory. Because the
stochastic model shares its parameterization with the deterministic one, it provides a scale-consistent extension of existing source-sink models for evaluating shell configuration, collision risk, and long-term LEO sustainability.
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Quantum Physics
Programmable Cavity Squeezing for Distributed Sensing in a Tweezer Array
Youssef Trifa, Marco Fattori and Luca Pezzè
Field sensing with state-of-the-art atom interferometers is restricted to the use of uncorrelated devices op- erating in parallel. We can overcome this limitation by using distributed sensing protocols where
quantum correlations among spatially-separated devices are engineered in the spatial mode carrying the signal. We show that a tweezer array in a cavity offers an ideal testbed to engineer
quantum states for distributed sensing, with the possibility to generate
entanglement both within and between the clouds. The competition between local and intercloud cavity-mediated exchange allows the sign and spatial pattern of the intercloud couplings to select the squeezed mode. For two ensembles, positive coupling produces uniform collective squeezing, whereas negative coupling generates strong staggered, nonlocal squeezing. A semiclassical analysis reveals a counter-twisting- like phase-space flow, qualitatively distinct from standard one-axis twisting. The analysis and results can be further generalized to a larger number of ensembles. We apply the scheme to differential Ramsey interferometry with common phase noise spanning the full 2 \pi range, the resulting staggered states reduce the phase uncertainty below the standard
quantum limit, with an ellipse
estimator approaching the Cramèr-Rao bound. These results establish programmable cavity interactions as a scalable route to
entanglement tailored to distributed signals.
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Earth and Planetary Astrophysics
Catastrophic tidal disruption of heterogeneous rubble piles: a tale of two regimes
John Wimarsson, Eric Frizzell, Martin Jutzi et al. (+1 more)
The way a rubble-pile body deforms or disrupts under the influence of
tidal forces can be directly tied to its internal strength and configuration. Computational modelling of such
tidal disruption events provides an indispensable numerical laboratory for constraining the origin and
evolution of small bodies in the
Solar System. A majority of previous investigations into
tidal disruption of rubble piles have mainly considered progenitors consisting of same-sized, spherical elements. Our study attempts to fill the existing gap in studies analysing the effect of aggregate heterogeneity on
tidal disruption outcomes by varying element shape and size frequency distribution. Such heterogeneities have been shown to strongly influence rubble pile dynamics for impacts and rotational failure. We performed numerical simulations of
parabolic and
hyperbolic tidal encounters between six unique rubble-pile progenitors and the Earth using the N-body code GRAINS. The resulting mass distributions of generated fragments and
tidal chain morphologies for the different progenitors were further tied to the internal strength of rubble piles. Two regimes of
tidal disruption are identified. In the first regime, closest to the
planet, the dynamic
evolution is dominated by
tidal forces. Here, particle shape, size distribution and resolution appear to have little importance for the resulting distribution of fragment masses. In the second, shear-controlled regime, the internal structure of the progenitor begins to strongly influence the resulting
tidal chain morphology and properties of the surviving fragments. Heterogeneity originating from the shape and size frequency distribution of elements in rubble pile models has a substantial effect on the outcomes of
tidal disruption events. These parameters must be carefully taken into account when future studies attempt to tie results from numerical models to observations.
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All authors John Wimarsson, Eric Frizzell, Martin Jutzi, Fabio Ferrari
Applied Physics
Diatom frustules as naturally occurring resonant microarchitectures: revealing vibrational eigenmodes across pennate and centric species
Chiara Gazzola, Dame Fall, Stefano Stassi et al. (+3 more)
Diatom frustules, the hierarchically structured, species-specific silica exoskeletons of diatom microalgae, are among Nature's most sophisticated examples of bottom-up self-assembly, exhibiting nanoscale porosity, multifunctional mechanical and optical properties, and a morphological diversity that spans nearly three orders of magnitude in size. Despite growing interest in their optical and static mechanical properties, the elastodynamic behaviour of frustules has remained largely unexplored. Here we report the first experimental detection and spatially resolved reconstruction of vibrational eigenmodes in diatom frustules, combining
laser Doppler vibrometry with morphology-faithful finite-element models informed by scanning electron microscopy (SEM) and focused-ion-beam scanning electron microscopy (FIB-SEM). Two morphologically contrasting taxa were investigated as model systems: the pennate diatom Rhaphoneis amphiceros and the centric diatom Stictodiscus californicus var. nitida, spanning the two principal branches of diatom diversity. Four eigenmodes were identified for R. amphiceros in the 5.90-14.17 MHz range and three for S. californicus in the 9.96-17.62 MHz range; the simulations yield a complete modal landscape for each species, including modally split and nearly degenerate eigenmodes arising from deviations from ideal
symmetry, and show quantitative agreement with the experimentally measured mode shapes and resonant frequencies. These results establish diatom frustules as a class of naturally occurring resonant microarchitectures, and open new avenues for their integration as bio-derived functional elements in nanomechanical and MEMS/NEMS applications.
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All authors Chiara Gazzola, Dame Fall, Stefano Stassi, Marc Duquennoy, Marc Serra Garcia, Marco Miniaci
Quantum Physics
Kramers pseudospin and the quantum number proposed for the many-electron Dirac?Coulomb Hamiltonian
Shadan Ghassemi Tabrizi
The square of a sum of single-electron time reversals has been proposed as a conserved quantity with an integer
eigenvalue spectrum for the many-electron Dirac-Coulomb
Hamiltonian [Phys. Rev. A 94, 052104 (2016)], and its expectation value is in use as a diagnostic of Kramers contamination. This work identifies the operator behind the construction, a component of a pseudospin attached to the chosen Kramers pairs, whose angular-momentum
algebra reproduces the reported spectrum and yields the eigenvectors in closed form. The label $k$ entering the proposed
quantum number $-k^2$ is twice the magnitude of a pseudospin projection onto an axis fixed by the basis and changes when the Kramers pairs are rephased. The commutation with the
Hamiltonian is unfounded, and the proposed
quantum number does not stand.
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Mathematical Physics
Quasi-polynomiality and $N$-point functions of single connected leaky completed Hurwitz numbers
Chongyu Wang and Chenglang Yang
In this paper, we study the structures of single connected $k$-leaky $(r+1)$-completed Hurwitz numbers. We first prove that, for fixed genus, after extracting an explicit product of Pochhammer type factors, the stable connected leaky Hurwitz numbers for partition $\mu$ are
polynomials in the quotients $[\mu_i]$ modulo $k+r$. We then give a closed formula for the generating function of single connected leaky Hurwitz numbers, which can be used to study the genus dependence of leaky Hurwitz numbers.
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Materials Science
Emergent Skyrmion Hall Effect in $d$-wave Altermagnets at Finite Temperature
Tingting Liu, Bingyu Sun, Fengyue Zhu et al. (+4 more)
Altermagnets combine compensated
magnetic order with unconventional
symmetry-dependent responses, offering a promising platform for spintronic applications. Here, we show that a voltage-controlled
magnetic-anisotropy gradient drives altermagnetic (ATM) skyrmions in a nearly rectilinear,
Hall-free manner in the absence of thermal fluctuations, owing to their strongly compensated gyrotropic response. Thermal
magnons qualitatively modify this behavior by increasing the longitudinal drag through
magnon–skyrmion scattering and generating a transverse reaction force through handedness-dependent skew scattering. Owing to the anisotropic altermagnetic
magnon band structure, the relative transport weights of the two
magnon handednesses are interchanged between propagation along the $x$ and $y$ directions, resulting in transverse skyrmion drifts of opposite sign. By contrast, along the high-
symmetry direction, the two
magnon handednesses remain degenerate and their transverse contributions cancel, preserving
Hall-free motion even at finite temperature. We thus uncover a thermally emergent anisotropic skyrmion
Hall effect whose direction-dependent magnitude and sign originate from the intrinsic
symmetry-dependent
magnon spectrum, making it a generic finite-temperature dynamical feature of ATM skyrmions. Our results establish a low-power route toward electrically controlled and thermally tunable ATM skyrmion transport.
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All authors Tingting Liu, Bingyu Sun, Fengyue Zhu, Zhihui Zhang, Peiyu Zhang, Yang Liu, Minghui Qin
Fluid Dynamics
Stochastic Transport and Wave Interactions for Multiscale Surface Gravity Waves: Part II: Kinetic Theory and Ocean-Wave Applications
E. Mémin, B. Chapron, A. Debussche et al. (+1 more)
Building on the
stochastic variational framework established in the companion paper, we investigate here the linearized
stochastic water-wave system, consisting of a large-scale
stochastic wave dynamics coupled to transport dynamics for the small-scale correlation modes. Within this framework, we develop, in the deep-water regime, a kinetic theory for surface
gravity waves interacting with unresolved
stochastic velocity fields. An energy analysis yields a wave-action kinetic equation exhibiting two distinct regimes: a diffusive scattering regime and a quartic interaction regime with structural similarities to Hasselmann–Zakharov theory. In the present framework, these effective quartic interactions arise through
stochastic transport of unresolved fluctuations by the large-scale flow rather than through classical intrinsic resonant nonlinearity. Scaling laws are derived for the
diffusion tensor and the effective growth rate, revealing a Miles-type production–dissipation mechanism. Using JONSWAP spectra, we then compare the strength of
stochastic transport and classical Hasselmann interactions. For realistic oceanic values of unresolved velocity variance ($\sigma_u \approx 0.1\,\mathrm{m\,s^{-1}}$) and decorrelation time ($\tau_c \approx 10\,\mathrm{s}$),
stochastic transport is found to compete with, and often exceed, classical four-wave interaction rates over broad spectral ranges. The transport intensity $S=\sigma_u^2\tau_c$ emerges as a key parameter controlling the transition between interaction regimes. These results suggest that unresolved
stochastic transport may play a substantially larger role in spectral
evolution than is commonly represented in operational wave models, and motivate the inclusion of transport-induced source terms alongside standard resonant interaction closures.
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All authors E. Mémin, B. Chapron, A. Debussche, L Marié