Soft Condensed Matter
Order by inertia in spinning active matter: holey fluids and spin-textured crystals
Camille Jorge and Denis Bartolo
Active matter sustains emergent flows at the expense of preserving structural order. The feedback between structure and viscous flows typically disrupts crystalline and
liquid-crystalline organization by amplifying the very deformations they generate. Yet this destabilizing paradigm has recently been challenged by experiments showing that inertial fluid flows can stabilize few-body bound states of active spinners. Whether inertial active matter can sustain genuine cohesion and order at the many-body level, however, remains elusive. Here we investigate two-dimensional assemblies of macroscopic spinners operating at high Reynolds number and uncover two phase transitions leading to the emergence of a dilute percolating fluid and a dense
spin-textured
crystal. At low density, inertial flows generate two competing interactions: anisotropic attractions and transverse Magnus forces that continuously break and reconfigure bonds. Together they drive a percolation transition toward a dynamically rearranging holey
liquid reminiscent of the empty-
liquid states observed in
equilibrium patchy colloids. At high density, the feedback between
spin alignment and particle positions suppresses transverse rearrangements and yields a first-order transition toward a
spin-ordered
crystal. Our results demonstrate that, beyond the overdamped limit, hydrodynamic feedback can promote rather than destroy collective order, revealing a distinct regime of many-body active matter governed by inertial flows.
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Mesoscale and Nanoscale Physics
Unity-order coupling between free electrons and multiphoton waveguided Fock states
L. Prelat, S. Abdullah, C. I. Velasco et al. (+1 more)
Electron beams enable highly localized near-field excitation of waveguided optical modes, yet their coupling is typically limited by short interaction times along straight-line trajectories with fixed impact parameters. Here, we theoretically demonstrate that electrostatic steering overcomes this limitation by introducing a tunable turning point in grazing electron trajectories, thus controlling the minimum electron–waveguide separation and producing strong coupling to waveguided modes. Specifically, we consider a biased rectangular silicon waveguide, where a repulsive static field deflects a grazing electron. In this configuration, the electron turning point governs both the coupling strength and the modal selectivity, which can be dynamically tuned through the electron incidence angle and the applied bias. In addition, the aloof electron–waveguide interaction suppresses lossy high-energy channels (e.g., above the silicon band gap) while preserving substantial excitation of the targeted waveguided modes. Using a practical biasing configuration and 100~keV electrons, we predict an average yield exceeding ten
photons per electron, with voltage-tunable control of the interaction. Our results establish electrostatic steering as a practical route for engineering and enhancing free-electron coupling to waveguided photonic modes.
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All authors L. Prelat, S. Abdullah, C. I. Velasco, F. J. García de Abajo
Soft Condensed Matter · Cross-listed from physics.class-ph
A nonlinear beam model for photoresponsive thermoelastic solids driven by localised heating
William T. Simpkins, Matteo Taffetani and Matthew G. Hennessy
Asymptotic methods are used to derive a geometrically nonlinear beam model for thermoelastic solids with a spatially localised heat source. The asymptotic reduction is based on collapsing the heated region to a point. Away from the point of heating, the governing equations reduce to a pair of beam equations with nonlinear von Kármán strains. The effects of the localised heat source are captured through asymptotically consistent jump conditions that hold at the point of heating. The model accounts for changes in beam length due to longitudinal thermal expansion and bending moments produced by transverse thermal gradients. The model is used to study light-induced actuation of photoresponsive hydrogel beams with localised heating arising from
laser irradiation. Two loading scenarios are considered. In the first, the ends of the beam are assumed to be free, resulting in a V-shaped deformation upon heating. An analytical expression for the fold angle of the V is provided. In the second, the beam is assumed to be in a pre-buckled configuration due to clamped end conditions. The critical conditions leading to light-driven snap-through are calculated. Offsetting the
laser from the mid-point of the beam is found to inhibit the onset of snap through.
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Materials Science
Engineering Molecular Rectification: Mechanisms, Modulation Strategies, and Device Integration
Junnan Guo, Shufan Song, Wenhui Fang et al. (+6 more)
Molecular rectifiers, as prototypical components of molecular electronics, present unique opportunities for pushing device miniaturization to its ultimate limits. Nevertheless, challenges including limited rectification ratios (RR), insufficient robustness, and poor reproducibility impede their practical deployment. To make molecular rectifiers competitive with silicon-based devices, it is important to fully understand the design principles and fabrication methods from both mechanistic and experimental perspectives. By holistically considering the transport mechanisms, modulation strategies, fabrication, characterization techniques, and theoretical simulations, this review provides a comprehensive overview of molecular rectifiers. Representative examples of conceptually significant and high-performance molecular rectifier systems are highlighted to illustrate the relationships between rectification mechanisms, molecular design strategies, and device realization. Building on these discussions, we present an outlook for current bottlenecks and future directions to guide the development of molecular rectifiers. This review aims to serve as both a conceptual framework and a technical reference for researchers working at the intersection of molecular electronics and nanoscale device engineering in the post-CMOS era.
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All authors Junnan Guo, Shufan Song, Wenhui Fang, Jifeng Tang, Wenhao Li, Weikang Wu, Hui Li, Shishen Yan, Lishu Zhang
Materials Science · Cross-listed from cs.LG
LEIA: Learned Environment for Interactive Architected Materials
Haiqian Yang, Yuan Cao and Markus J. Buehler
World models have enabled interactive exploration of game environments and robotic manipulation, but physical engineering remains beyond their reach: real materials exhibit nonlinear constitutive laws, carry history-dependent internal state, undergo inertial dynamics, and may possess hierarchical structures spanning multiple length scales. We present LEIA (Learned Environment for Interactive Architected materials), a world model that lets engineers apply boundary conditions step by step and observe the resulting deformation and stress fields in real time. LEIA handles large three-dimensional unstructured meshes and generates autoregressive responses to user-specified loading. We introduce MicroPlate, a
benchmark of architected plates spanning two regimes of microstructure modeling: architected
lattices that resolve microstructure explicitly through three-dimensional geometry, and a homogeneous plate where microstructural change is modeled implicitly through internal degrees of freedom. MicroPlate is used to assess LEIA alongside four baseline methods across both regimes. Finally, we demonstrate that LEIA enables efficient candidate generation and ranking for fast surrogate-guided search for de novo designs of architected materials, with stress-accurate candidate ranking validated by finite element ground truth.
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Materials Science
SC-1 Etching of Niobium and Titanium Nitride Thin Films
Adrián Gutiérrez-Cruz, K. A. C. Rathnathilaka, Jani M. Taskinen et al. (+6 more)
Dry etching techniques, ubiquitous in microelectronics fabrication, often result in challenging levels of undesired collateral
plasma-induced damage. In this work, we demonstrate a wet etching alternative for the patterning of niobium (Nb) and titanium nitride (TiN) thin films using the Standard Cleaning 1 (SC-1) solution. We characterize the etching process through its time-
evolution dynamics, supported by scanning-electron and atomic force microscopy assessment of the etched film morphology. The results suggest etch dynamics that are linked to native
oxides and film microstructure. Overall, the manageable etch rates, the safe operation and the high material selectivity are attractive for practical use in microelectronics fabrication.
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All authors Adrián Gutiérrez-Cruz, K. A. C. Rathnathilaka, Jani M. Taskinen, Tuomas Vaimala, Kestutis Grigoras, Harshad Mishra, Rishabh Upadhyay, Jorden Senior, Alberto Ronzani
Materials Science
Energy and Scaling Limits of Phase-Change Memory
Rivka-Galya Nir-Harwood, Asir I. Khan, Emanuel Ber et al. (+6 more)
Phase change
memory (PCM) relies on a reversible transition between amorphous and crystalline states of a material, and stands as a promising candidate for next-generation, energy-efficient data storage and neuromorphic hardware. Here, we review key innovations that have driven PCM technology to achieve energy consumption down to only tens of femtojoules per bit, and could further advance it closer to its fundamental limits. Because PCM switching is induced thermally, we highlight improvements in energy-efficiency through two primary strategies: by minimizing the active phase change material region to sub-10 nm dimensions, and by enhancing heat confinement within PCM devices to reduce thermal dissipation into the surrounding environment. While the theoretical limits could reach single attojoules per cubic nanometer of
memory material, realizing these limits in practice is significantly constrained by electrical and thermal parasitics, particularly at contacts and interfaces.
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All authors Rivka-Galya Nir-Harwood, Asir I. Khan, Emanuel Ber, Efrat Ordan, Keren Stern, Kye L. Okabe, Nicolás Wainstein, Eilam Yalon, Eric Pop
Soft Condensed Matter
Dry Glass Reference Perturbation Theory: Development, Applications and Extensions
Bennett D. Marshall
This manuscript reviews the development, application and extensions of the dry glass reference perturbation theory (DGRPT) closure to the non-
equilibrium thermodynamics of glassy
polymers (NETGP). DGRPT was developed to allow for the self-consistent and accurate predictions of sorption from complex
liquid mixtures into glassy
polymers. DGRPT is applied in the context of
diffusion theory to predict the membrane based separations of complex
liquid mixtures with glassy
polymer membranes. Several examples are given, including the membrane based fractionation of crude oil as well as the membrane based separation of highly non-ideal alcohol / hydrocarbon
liquid mixtures. Extensions of the theory to higher order expansions are reviewed and evaluated.
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Statistical Mechanics · Cross-listed from math-ph
Dissipative Spectral Form Factor of the Complex Elliptic Ginibre Ensemble across Various Non-Hermiticity Regimes
Gernot Akemann, Sung-Soo Byun and Seungjoon Oh
We study the dissipative spectral form factor (DSFF) at complex time $T e^{i\theta}$ for the complex
elliptic Ginibre ensemble with non-Hermiticity parameter $\tau \in [0,1)$. As the
matrix dimension $N \to \infty$, we consider the natural scalings in both the time variable and the non-Hermiticity parameter, namely $T = O(N^\gamma)$ and $1 - \tau = O(N^{-\alpha})$. For all regimes $\gamma \ge 0$ and $\alpha \ge 0$, we derive the precise asymptotic behaviour of both the disconnected and connected components of the DSFF. In particular, we explicitly characterise the dip–ramp–plateau structure, including the dip time and the Heisenberg time. In addition, we identify the mesoscopic regime $\alpha \in (0,1)$, which interpolates between the behaviour of the DSFF of non-Hermitian random
matrices and the spectral form factor (SFF) of Hermitian ensembles. We further provide an explicit description of the phase diagram, in which the ramp exhibits quadratic, linear, or intermediate behaviour depending on the scaling parameters.
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Mesoscale and Nanoscale Physics
Nanoscale Confinement Enhances Ultrafast Demagnetization
Yoav William Windsor, Tobias Lojewski, Moumita Kundu et al. (+21 more)
Nanoscale miniaturization has revolutionized the field of spintronics by enabling exponential growth in areal bit density. A similar leap is also expected in device speeds through successfully harnessing femtosecond magnetization dynamics. However, combining this with the miniaturization of realistic devices is challenging. To address this, we studied the effect of dimensional confinement on the femtosecond demagnetization of Fe. By gradually increasing the level of confinement while keeping excitation conditions constant, we found that Fe layers thinner than 10 nm exhibit enlarged demagnetization amplitudes, reaching a $\sim75\%$ increase at 2 nm. By combining ultrafast experiments sensitive to the
spins, the charge carriers, and the
phonons, we establish that this finite$\text{-}$size effect is
magnetic in origin and is not
phonon$\text{-}$driven. With the support of ab$\text{-}$initio calculations and atomistic
spin dynamics simulations, we identify the enhancement effect as due to local weakening of
spin order at the Fe$\text{'}$s interface, which becomes significant upon increased confinement.
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All authors Yoav William Windsor, Tobias Lojewski, Moumita Kundu, Klaus Sokolowski-Tinten, Nico Rothenbach, Andrea Eschenlohr, Markus Ernst Gruner, Katharina Ollefs, Carolin Schmitz-Antoniak, Soma Salamon, Daniela Zahn, Laurenz Rettig, Christian Schüßler-Langeheine, Niko Pontius, Renkai Li, Mianzhen Mo, Suji Park, Xiaoshe Shen, Stephen Weathersby, Xijie Wang, Rossitza Pentcheva, Heiko Wende, Ulrich Nowak, Uwe Bovensiepen
Materials Science
High temperature Jahn-Teller distortion and short-range order in CsCuCl$_3$
Emma A. Pappas, Toby Woods, Jue Liu et al. (+1 more)
CsCuCl$_3$,
chiral and Jahn-Teller distorted at room temperature, takes a more symmetric structure above 423 K. Describing this 'simpler' high temperature structure is far from simple and has been the subject of many, sometimes contradicting, studies. Here we reinvestigate the high temperature structure of CsCuCl$_3$, its thermal stability, and its effect on room temperature chirality. In situ pair distribution function data from powder
neutron diffraction confirms that CsCuCl$_3$ is Jahn-Teller distorted both below and above $T_\mathrm{c}$, and provides a quantitative view of short-range order in the high temperature structure. In situ powder x-ray diffraction shows that CsCuCl$_3$ does not undergo any additional structural changes above 423 K and is congruently melting. In situ single
crystal x-ray diffraction experiments reveal that the phase transition induces domains of mixed handedness in originally homochiral
crystals. These findings contribute to a better understanding of phase transitions in Jahn-Teller distorted compounds, and highlight the potential use of phase transitions to control
chiral domains.
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All authors Emma A. Pappas, Toby Woods, Jue Liu, Daniel P. Shoemaker
Materials Science · Cross-listed from cs.LG
AtomComposer: Discovering Chemical Space from First Principles with Reinforcement Learning
Bjarke Hastrup, Francois Cornet, Tejs Vegge et al. (+1 more)
Discovering novel stable molecules without training data remains a grand scientific challenge. Current molecular generative models are trained on large, pre-curated
datasets, which introduce biases and limit exploration of novel chemistry. In contrast, we propose a new paradigm: autonomous, generalized
agents capable of mapping vast, unknown chemical spaces without any pretraining. For the first time, we present AtomComposer, a self-guided
agent that autonomously constructs valid 3D isomers under stoichiometric constraints and is trained exclusively online using reinforcement learning. Unlike existing approaches that generally overfit to a specific chemical formula, we establish a multi-composition training scheme that enables a broad generalization across diverse chemistry, guided by energy- and validity-based rewards. Our
agent can discover up to an order of magnitude more valid isomers on unseen test formulas than existing single-composition reinforcement-learning baselines trained with per-step energy rewards. These results fulfill the promise of online reinforcement learning as a powerful paradigm for scalable, from-scratch exploration of chemical configuration space.
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All authors Bjarke Hastrup, Francois Cornet, Tejs Vegge, Arghya Bhowmik
Mesoscale and Nanoscale Physics
Photon-energy-programmable subnanometric electron birth-site control
Hirofumi Yanagisawa, Abhisek Sinha, Ravi Kumar et al. (+4 more)
Optical control of electron-generation sites has broadly enabled ultrafast nanoscale imaging, spectroscopy, and functional control. Existing approaches achieve nanoscale site selectivity by shaping localised optical fields around nanostructures, thereby limiting independent site selectivity within the same local-field hotspot. Here, using a single-molecule electron emitter, we show that site selectivity can instead be encoded in the electronic excitation pathway, enabling subnanometric control of electron birth sites within a common local-field hotspot. By tuning the
photon energy, we selectively access different groups of molecular states whose combined contributions define emission channels with distinct spatial character, thereby reversibly switching the electron birth site within the same emitter. The switching is read out directly in the far-field emission pattern and occurs upon changing the
photon energy, but not upon varying the intensity or polarisation. Our results establish optical birth-site selectivity that is not dictated by the local-field distribution, opening a route to electron birth-site control through the electronic excitation pathway.
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All authors Hirofumi Yanagisawa, Abhisek Sinha, Ravi Kumar, Hiroki Funata, Pasquale Barbato, Neill Lambert, Hirotaka Kitoh-Nishioka
Strongly Correlated Electrons
Change in charge density wave order beyond the Lifshitz transition in 2H-Ta\textsubscript{1$\pm\delta$}S\textsubscript{2}
Mihir Date, Jan Berges, Enrico Da Como et al. (+6 more)
We investigate electronic instabilities in 2H-TaS\textsubscript{2} and a self-intercalated variant, 2H$^\dagger$-Ta\textsubscript{1+$\delta$}S\textsubscript{2}. In conventional samples, which we determine to be slightly hole-doped, spectral gaps and backfolded features are found as fingerprints of the $3\times3$ charge density wave (CDW). Notably, the backfolded features emerge only at a temperatures below $T\approx$~65~K, substantially lower than the established CDW temperature of 78~K, suggesting an incommensurate-commensurate lock-in transition analogous to the phenomenology of the 2H-TaSe\textsubscript{2}. In contrast, the self-intercalated 2H$^\dagger$ sample exhibits substantial electron doping and signatures of a novel \tworootthree CDW. Using ab initio calculations of the
phonon spectrum, we demonstrate that the \threebythree instability ($\mathbf{q}=\sfrac{2}{3}\mathbf{\Gamma M}$) is highly sensitive to band filling. Furthermore, with increased interlayer spacing, a competing soft
phonon mode emerges near $\mathbf{q}=\sfrac{1}{2}\mathbf{\Gamma K}$, corresponding to the superstructure observed in the 2H$^\dagger$ phase, although in our calculations this instability arises under hole doping rather than the electron doping inferred experimentally. These results establish band filling and interlayer spacing as key control parameters for CDW ordering vectors in 2H-TaS\textsubscript{2}, and highlight a route to engineering electronic instabilities in a prototypical layered material.
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All authors Mihir Date, Jan Berges, Enrico Da Como, Marcin Mucha-Kruczyński, Alex Louat, Gabriele Domaine, Niels B. M. Schröter, Malte Rösner, Matthew D. Watson
Mesoscale and Nanoscale Physics
Taming quantum interference: a route to high electrical conductance in carbon nanotube assemblies
Teresa Kulka, Agnieszka E. Lekawa-Raus, John S. Bulmer et al. (+6 more)
In nanostructured networks, transport is governed by junctions between neighbouring building blocks. Improving their
alignment and removing defects is the intuitive route to better electron transport. At low temperatures, when transport becomes coherent, a junction cannot always be reduced to a single effective resistance, because electron-wave interference can strongly enhance or suppress transmission even in nominally ideal junctions. Using carbon nanotube (CNT) networks as a model system, we explore coherent transport through experimentally relevant junctions, from single and multiple single-walled CNT (SWCNT) contacts to double-walled CNT (DWCNT) and multi-walled CNT (MWCNT) junctions, with atomistic tight-binding non-
equilibrium Green's-function calculations, also under a perpendicular
magnetic field. We use analytically solvable minimal models to identify transport regimes expected for quasi-1D nanoscale junctions, and an electron-waveguide picture to interpret their CNT-specific manifestations. For single SWCNT–SWCNT junctions, high-transmission windows are set mainly by overlap length, doping and
magnetic field. Gateway states can enhance conductance when some CNT subbands are gapped, and in some cases a
magnetic field can restore transmission by lifting an interference blockade. In more complex architectures, added paths become selective: multi-junctions generate resonant filtering, while additional walls redistribute transmission instead of acting as independent channels. DWCNT junctions remain outer-wall dominated and SWCNT-like, whereas MWCNT junctions redistribute transmission among coupled walls and show a more complex field response. Our ultrahigh-field measurements likewise show lower, more field-sensitive conductance in MWCNT than SWCNT fibres. This work turns microscopic interference mechanisms into design principles for high-conductance, field-stable CNT conductors.
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All authors Teresa Kulka, Agnieszka E. Lekawa-Raus, John S. Bulmer, Krzysztof Koziol, Fedor F. Balakirev, Irina V. Lebedeva, Jacek A. Majewski, Magdalena Marganska, Karolina Z. Milowska
Strongly Correlated Electrons
Zero-Field Thermal Hall Effect in Insulator
Zhe Cui, Haoran Fan, Wenjiang Zhou et al. (+9 more)
Fourier's law dictates that heat flow is usually parallel to the applied temperature gradient. However, under a high
magnetic field, heat flow carried by both electrons in conductors and
phonons in
insulators can be deflected, a phenomenon known as thermal
Hall effect. Intriguingly, we observe at zero field a spontaneous thermal
Hall effect in an
antiferromagnetic insulator. Despite a vanishingly small uncompensated magnetization, the magnitude of this effect is surprisingly large, comparable to typical responses induced by several teslas of external field. This zero-field behavior indicates that charge-neutral heat carriers can be governed by an intrinsic effective field arising from the unique
spin arrangement. Our discovery challenges the centuries-old preconception of heat conduction and open up new avenues for exploring non-trivial topological responses in
quantum materials.
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All authors Zhe Cui, Haoran Fan, Wenjiang Zhou, Xianghong Jin, Yuchen Gu, Da Ma, Cong Xiao, Hua Jiang, Xincheng Xie, Bai Song, Yuan Li, Xi Lin
Materials Science
Nonlinear Elasticity at the Damage Threshold of Semiconductor Nanocrystals
Daniel Hensel, Adriana Rodrigues, Anagha Kamath et al. (+5 more)
The nonlinear photoacoustic response of indium phosphide nanocrystals on silicon nanotip arrays is investigated using time-resolved optical pump-probe spectroscopy and synchrotron-based X-ray diffraction. Femtosecond
laser excitation triggers low-frequency and high-frequency radial breathing modes of the nanocrystals at 8 GHz and 10.3 GHz, respectively. At excitation fluences above 3 mJ/cm^2, nonlinear frequency mixing occurs, including sum- and difference-frequency generation, indicative of strain-induced nonlinear elasticity. A higher-order extension of Hooke's law models the fluence-dependent spectral response and yields a physically valid elastic energy potential. Ex-situ energy-dispersive X-ray spectroscopy reveals a correlation between nanocrystal oxidation and the emergence of nonlinear acoustic modes. Time-resolved X-ray diffraction confirms the nanocrystals as the origin of the low-frequency modes and supports the hypothesis of acoustic decoupling from the substrate. These findings provide insight into the mechanical limits of
semiconductor nanostructures under intense optical excitation and suggest new pathways for material characterization and optomechanical control at the nanoscale. The results advance the understanding of nonlinear
phonon dynamics in nanocrystals and highlight their potential for integration into next-generation photonic and
quantum devices.
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All authors Daniel Hensel, Adriana Rodrigues, Anagha Kamath, Daniel Schmidt, Mariana Brede, Oliver Skibitzki, Fariba Hatami, Peter Gaal
Superconductivity
Three-component superconductivity: the effect of second-order Josephson couplings
Shen-Yi Peng, Ling-Feng Zhang and Xiao Hu
Recently, a three-component Ginzburg-Landau (GL) model compatible with the 3Q pair-density-wave state has been proposed to explain the fractional
quantum magnetic resistance oscillations of period $\phi_0/3 = hc/6e$ observed in vanadium-based kagome
superconductors. The physics of this model is governed by second-order Josephson-type couplings, which break both time-reversal
symmetry and discrete $\pi$-phase flip
symmetry. In this work, we theoretically derive the complete set of ground-state solutions and construct a comprehensive phase diagram in the GL parameter space, characterized by analytically determined phase boundaries. We identify five distinct ground states: an 8-fold degenerate frustrated state and four 4-fold degenerate non-frustrated phase-locked states. Four of these states spontaneously break time-reversal
symmetry. Numerical analysis of the collective modes reveals the emergence of a
Higgs-Leggett mode unique to the frustrated region, accompanied by mode softening near the phase boundaries. Our findings provide a comprehensive theoretical framework for understanding the multifaceted physics of multicomponent superconductivity.
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Statistical Mechanics
Barrier crossing in a two-state system: Effect of bias and stochastic fields
Sara Oliver-Bonafoux, Raúl Toral and Amitabha Chakrabarti
We study barrier crossing in a two-state system, namely the kinetic Ising model, in the presence of a weak bias field and spatially homogeneous, but time-dependent, Gaussian random fields. We find that the bias field determines the location of the dominant maxima of the probability distribution function of the magnetization, whereas the noise intensity controls their sharpness and stability of the distribution. A moderate
stochastic field lowers the effective energy barrier and facilitates transitions between ordered states, while strong noise induces broad distributions and significant backflow, which reduces directional selectivity. Our results suggest that efficient barrier crossing requires a balanced combination of moderate
stochastic driving and controlled bias.
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Materials Science
Search for high-pressure phases of yttrium via a data assimilation approach
Yuuki Kubo, Takahiro Ishikawa, Yuta Tanaka et al. (+3 more)
We investigate the distorted face-centered-cubic (dfcc) phase of yttrium (Y) using a data-assimilation-based structure search that combines high-resolution powder x-ray diffraction (XRD) data with machine-learning interatomic potentials. By exploring supercells containing up to 128 atoms, we identify three low-enthalpy phases: the previously reported $I4_1/a$ structure and two additional structures, $Ibam$ and $R\overline{3}$. No data-assimilation-derived structure relaxes to the previously proposed $R\overline{3}m$ phase.
Phonon calculations show that $I4_1/a$, $Ibam$, and $R\overline{3}$ are dynamically stable, whereas $R\overline{3}m$ exhibits imaginary modes near the $\Gamma$ point, indicating dynamical instability. Enthalpy calculations using both PBE and r$^{2}$SCAN place the four candidate structures within about 10 meV/atom, indicating a complex energy landscape with multiple competing minima, although $R\overline{3}m$ is consistently highest in enthalpy and r$^{2}$SCAN favors $I4_1/a$ throughout the dfcc pressure range. Rietveld refinements of the powder XRD profile at 60 GPa further narrow the viable structural models to $I4_1/a$ and $Ibam$, both of which reproduce the experimental data better than $R\overline{3}m$ and $R\overline{3}$. Taken together with the energetic ordering and dynamical stability, these results identify $I4_1/a$ as the most plausible structure of the dfcc phase of Y, with $Ibam$ remaining a close competing candidate, particularly toward the high-pressure side of the dfcc region.
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All authors Yuuki Kubo, Takahiro Ishikawa, Yuta Tanaka, Yuki Nakamoto, Masafumi Sakata, Shinji Tsuneyuki
Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Quantum Spin Squeezing Enhanced by Critical Exceptional Points
Yuma Nakanishi
Critical exceptional points (CEPs) are nonequilibrium critical points in open many-body systems at which multiple collective excitation modes coalesce. CEPs are known to amplify classical fluctuations, but their effect on genuinely
quantum fluctuations remains unclear. Here, we show that dissipative collective-
spin systems hosting CEPs exhibit parametrically enhanced steady-state
quantum spin squeezing. Close to the CEP, the optimally squeezed variance scales as $|Z|$, whereas the anti-squeezed variance diverges as $|Z|^{-1}$, with $Z$ the dimensionless order parameter. Importantly, the anti-squeezed fluctuation direction asymptotically aligns with the coalescing eigenvector of the stability
matrix, reflecting the defective nature of the CEP dynamics. These scalings are robust against dephasing channels generated by
spin components orthogonal to the coalesced critical collective mode. Our results identify CEPs as a route to engineering steady-state anisotropic
quantum fluctuations and correlations in driven-dissipative platforms.
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Strongly Correlated Electrons
Cascade of magnetic-field-induced quantum spin states in a spin-1 honeycomb magnet
Kaixin Tang, Zhao-Yang Dong, Yanyan Shangguan et al. (+10 more)
Quantum fluctuations endow
spin systems with surprisingly enriched
magnetic phase diagrams. In frustrated magnets, strong
quantum fluctuations boosted by either geometrical incompatibility or competitive exchange interactions stabilize cascades of unusual phases of matter. Here we reveal the presence of multiple
quantum phases in the honeycomb antiferromagnet Na$_{3}$Ni$_{2}$BiO$_{6}$, both inside and beyond its field-induced one-third magnetization plateau. Comprehensive measurements of thermodynamic quantities demonstrate that the one-third plateau comprises at least three distinct
spin states with nearly-degenerate net magnetization, separated by first-order transitions that likely involve sequential
spin reconfiguration. Upon further increasing the
magnetic field, the system evolves across a myriad of peculiar phases before reaching full polarization; these intermediate phases possess copious low-energy excitations, manifested by anomalous upturns of specific heat at ultralow temperatures – probably hinting at the development of "hidden" ordered ground states. The complex
magnetic phase diagram of Na$_{3}$Ni$_{2}$BiO$_{6}$ underlines the preponderant impact of
quantum fluctuations on a honeycomb
spin lattice with strong exchange frustration.
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All authors Kaixin Tang, Zhao-Yang Dong, Yanyan Shangguan, Zhao Gong, Ye Yang, Song Bao, Houpu Li, Nan Zhang, Hongyu Li, Jian-Xin Li, Jinsheng Wen, Ziji Xiang, Xianhui Chen
Materials Science
Analytical solution of the Langmuir model for moisture diffusion in cylindrical coordinates
Corentin Guigot, Romain Grangeat and Gilles-Alexis Renaut
Moisture
diffusion in
polymers and bio-based materials frequently exhibits non-Fickian behavior that cannot be described by classical
diffusion models. The Langmuir model, which accounts for the coexistence of mobile and bound water molecules, has been widely used to represent such phenomena. However, analytical solutions of this model are generally limited to planar geometries, while cylindrical systems are typically investigated using numerical methods. In this work, the Langmuir
diffusion model is solved analytically in cylindrical coordinates. The resulting solution provides both the local
evolution of moisture content within the cylinder and the corresponding global moisture uptake kinetics. The analytical solution is validated through comparison with an independent numerical solution based on a finite difference scheme, showing excellent agreement for both the global absorption kinetics and the radial moisture profiles. The proposed formulation therefore provides a simple and efficient analytical framework for studying non-Fickian moisture
diffusion in cylindrical systems such as natural fibers, and facilitates the identification of model parameters from experimental data.
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Soft Condensed Matter · Cross-listed from physics.bio-ph
Primary hemostasis and dynamics of clot formation after microvascular injury
Alper Topuz, Gerhard Gompper and Dmitry A. Fedosov
Primary hemostasis is initiated by platelet adhesion and aggregation at a site of vascular injury and is strongly regulated by local hydrodynamic conditions. At elevated shear rates, platelet capture is mediated by von Willebrand factor (vWF), a multimeric
protein that undergoes shear-induced unfolding and becomes adhesive. We investigate early-stage clot formation under physiological high-shear-flow conditions by employing particle-based mesoscale hydrodynamics simulations with explicitly resolved red blood
cells, platelets, and mechano-sensitive vWF in a microchannel geometry. The model incorporates vWF-mediated adhesion of platelets to a hemostatic surface, together with non-periodic inflow-
outflow boundary conditions that allow continuous material supply and transport. We analyze the dynamics of platelet-vWF aggregation, clot growth dynamics, clot geometry and internal stresses, and thrombo-embolization across a range of elevated flow rates. Our results demonstrate that clot formation proceeds through the establishment of platelet-vWF aggregates at the hemostatic site, and that the clot reaches a finite size determined solely by hydrodynamic forces, without invoking biochemical stabilization mechanisms. Beyond a critical size, increased drag from fluid flow leads to recurrent embolization events that limit further growth. These findings highlight the central role of hydrodynamic stresses in regulating primary hemostasis and provide a mechanistic framework for understanding clot stability under physiological flow conditions.
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Quantum Gases
Hall effect in multi-leg bosonic ladders
Edmond Orignac, Roberta Citro and Thierry Giamarchi
We use bosonization to analyze the ground state
Hall response of interacting bosonic N-leg ladders threaded by a flux. We derive an explicit expression of the
Hall imbalance in a perturbative expansion in the band
curvature, retaining fully the interactions. For small
magnetic field the
Hall resistance is proportional to the derivative of the logarithm of the charge stiffness with respect to density, generalizing the result obtained in the two leg case. We also consider the effect of temperature, and establish that at low temperature, corrections to the
Hall resistance are exponentially small in the Meissner phase.
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Quantum Gases · Cross-listed from quant-ph
Environment-Enhanced Single-Photon Absorption in a Nano-Ring of Dipole-Coupled Quantum Emitters
Eric Sánchez-Llorente, Helmut Ritsch and Maria Moreno-Cardoner
Decoherence is mostly detrimental in
quantum information and
quantum optics applications. However, the interplay between environment-induced incoherent dynamics and
unitary evolution can give rise to novel
quantum many-body phenomena that can be harnessed as a useful resource. As is well known, in dense subwavelength atomic arrays only a single collective eigenmode in the single-excitation
manifold couples strongly to free-space radiation, exhibiting superradiant spontaneous emission. Most of the remaining eigenstates form a
manifold of weakly radiative modes, giving rise to long-lived subradiant excitations. Here we demonstrate that populating these subradiant modes via additional decoherence mechanisms, such as dephasing or coupling to
phonons, can significantly enhance single-
photon absorption in a nanoring of
quantum emitters. Such nanoring geometry is particularly appealing due to its unique optical properties and its resemblance to natural light-harvesting complexes, which serve as efficient
antennas in photosynthesis. Our findings may shed light on fundamental aspects of energy absorption in nature; despite the much greater complexity of biological systems, they may nonetheless operate according to similar underlying optical principles.
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Materials Science
Effect of Vacancies on Hydrogen Mobility and Trapping in Elemental Fe and Cr: A DFT and kMC Study
Vallinathan K, Gurpreet Kaur and Sharat Chandra
Hydrogen-vacancy interactions play an important role in governing hydrogen transport and embrittlement in body-centered cubic (BCC) metals. In this study, a multiscale approach combining density functional theory (DFT) and kinetic Monte Carlo (kMC) simulations is employed to investigate hydrogen behavior in BCC Fe and Cr. The DFT-calculated binding energies and Bader charge analysis indicate stronger hydrogen trapping in Cr than in Fe. Migration and detrapping energy barriers are determined using the climbing-image nudged elastic band method, showing that the detrapping energy generally decreases with increasing hydrogen occupancy. However, the sixth hydrogen atom in Fe exhibits a finite barrier, contrary to some previous reports. kMC simulations are then used to evaluate hydrogen
diffusion over extended time and length scales. The results demonstrate that vacancy defects significantly reduce hydrogen mobility and increase the effective activation energy, with a more pronounced effect observed in Cr due to stronger trapping. The combined DFT-kMC framework provides detailed insight into the mechanisms of hydrogen trapping, detrapping, and
diffusion in BCC metals, offering important implications for understanding hydrogen embrittlement in structural materials.
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Strongly Correlated Electrons
Direction-selective intertwined charge, orbital, and lattice orders under uniaxial strain in hole-doped manganite: La0.75Ca0.25MnO3
Ju Hyeon Lee, Beom Hyun Kim and Bongjae Kim
The complex interplay of charge,
spin, orbital, and
lattice degrees of freedom governs emergent phases in
quantum materials, making strain a powerful control parameter. Recent advances in free-standing layer techniques have enabled extreme strains of nearly 8%, opening access to novel and often unexpected electronic and
magnetic phases. Here, using a density functional theory approach, we investigate the effect of direction-selective uniaxial strain on the prototypical Jahn-Teller system La1-xCaxMnO3 (x = 0.25). We find that different strain directions stabilize qualitatively distinct structural, charge, and orbital responses, rather than merely different strengths of the same phase. In particular, extreme uniaxial strain selectively induces cooperative Jahn-Teller, breathing-like, and site-selective modulations, thereby enabling previously inaccessible intertwined orders in manganites. These results establish direction-selective uniaxial strain as a powerful and selective route for engineering emergent phases in
quantum materials.
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Statistical Mechanics
Finite-size occupancy scaling of apparent fractal dimensions in stochastic trajectories
Bon A. Koo and Edward Ju
Estimating a fractal dimension from a finite
stochastic trajectory is a finite-size scaling problem: the apparent box-counting exponent is shaped by an occupancy crossover between the resolved range of scales and the finite number of sampled points, and need not equal the dimension of the limiting process. We model this crossover with a balls-in-boxes occupancy law, which predicts the box-count curve, the finite-size saturation scale, and a scaling function for the normalized local slope. Across random-walk traces, fractional Brownian graphs, and Levy flights, the normalized local slope collapses onto a single crossover curve, while the windowed box-counting bias collapses when the regression window is positioned relative to the saturation scale. Inverting the occupancy model gives a finite-size bias correction that reduces error on controlled
stochastic trajectories and transfers across held-out model classes. Comparisons with correlation dimension, detrended fluctuation analysis, the variogram, and Higuchi's method show that the dominant bias is specific to point-sampled box-counting over finite scale windows, and that local-slope stability alone is not a reliable diagnostic. A DNA-walk example illustrates the workflow on measured data, and all figures, tables, and in-text numbers are regenerated from released single-seed code.
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Statistical Mechanics · Cross-listed from quant-ph
Geometry near rank-changing points on the mixed-state manifold: Bures metric, conical singularities, and Lindblad dynamics
Yu-Huan Huang, Xu-Yang Hou, Hao Guo et al. (+1 more)
We elucidate the Bures metric in
quantum state space near a rank-changing point of the density
matrix and show contrasting behavior for two-level ($N=2$) systems versus higher-level systems. Due to the smooth pure-state boundary for $N=2$, we prove the apparent metric divergences to be merely coordinate artifacts and present three Lindblad processes exhibiting qualitatively different
evolution near rank-changing points, showing geodesic approach, power-law scaling, and pure-state escape law. For higher-dimensional ($N\ge 3$) systems, the geometry near a rank-changing point differs fundamentally. Under suitable restrictions of the density
matrix and its approach towards a pure state, the Bures metric reduces to a conical metric with the pure state at the cone tip. Such a conic geometry leads to genuine
curvature singularities: A two-dimensional cone exhibits a Dirac delta-function
curvature near the tip while a higher-dimensional cone shows a power-law divergence of the
curvature towards the cone tip. A construction of Lindblad
evolution for $N=3$ systems with conic singularities is presented, along with possible implications for future experimental and theoretical research.
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All authors Yu-Huan Huang, Xu-Yang Hou, Hao Guo, Chih-Chun Chien