Soft Condensed Matter
Amorphous Radial Frustration and Water-Like Anomalies in a Ramp-Shoulder Fluid
Murilo S. Marques, Lucas Axel R. Santana, Gabriel San R. R. Câmara et al. (+1 more)
We investigate the thermodynamic, structural, and dynamic behavior of a three-dimensional coarse-grained ramp-shoulder fluid derived from effective interactions between
polymer-grafted nanoparticles. The interaction combines a softened repulsive ramp with a shallow attractive shoulder, stabilizing competing local organizations over a broad pressure interval. Molecular dynamics simulations reveal density,
diffusion, and structural anomalies together with crystalline, amorphous, and fluid regions in the phase diagram. Unlike conventional isotropic core-softened fluids, the anomalous hierarchy becomes partially decoupled: the density anomaly extends beyond the structural anomaly, while the
diffusion anomaly becomes closely connected to amorphization and shell migration processes. Analysis of radial distribution functions, excess
entropy, translational and orientational order, and coordination-shell organization shows that the anomalies are not controlled solely by shell competition. Instead, they emerge from cooperative radial restructuring in a regime where radial correlations increase without the development of crystalline orientational order. The results indicate that the detailed shape of the softened interaction region strongly influences the structural pathways explored under compression, leading to a regime of amorphous radial frustration associated with anomalous
diffusion and frustrated shell reorganization.
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All authors Murilo S. Marques, Lucas Axel R. Santana, Gabriel San R. R. Câmara, José Rafael Bordin
Statistical Mechanics · Cross-listed from quant-ph
Entanglement-facilitated macroscopic cluster formation in quantum many-body dynamics
Xiao Wang, Alexander Yosifov, Aditya Iyer et al. (+1 more)
Metastable
quantum many-body dynamics could facilitate the organisation of microscopic degrees of freedom into macroscopic structures. However, the conditions under which this occurs are not well understood. Here we study false-
vacuum decay in a 2D
quantum Ising model and show that the initial correlation structure can qualitatively change this behaviour. Compared with product-state initialisations, correlated false-
vacuum states suppress the proliferation of small true-
vacuum domains and favour the formation of macroscopic connected clusters. Tree tensor network simulations of
lattices up to $25 \times 25$ further reveal that nucleation proceeds predominantly from the boundary. Finite-size scaling demonstrates the dominant connected cluster remains an extensive fraction of the system even as its size increases. By suppressing this edge-assisted nucleation pathway through boundary pinning, we generate large magnetisation fluctuations consistent with macroscopic superposition. This mechanism relies on the 2D nucleation barrier and is absent in 1D systems or product-state quenches. Our results identify correlated state preparation and boundary engineering as complementary techniques for controlling metastable
quantum dynamics.
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All authors Xiao Wang, Alexander Yosifov, Aditya Iyer, Jinzhao Sun
Mesoscale and Nanoscale Physics
Non-reciprocal Coulomb drag in a ballistic quantum wire
Suyang Cai, Mingyang Zheng, Nathan Rao et al. (+4 more)
1D-Coulomb drag serves as a platform for probing electron-electron interactions in 1D systems. Under the charge fluctuation formalism, the non-reciprocal component of Coulomb drag signal in mesoscopic devices is predicted to rely on the breaking of translational invariance due to intrinsic disorder. In this work, we report the measurement of a Coulomb drag device with a ballistic drag wire, allowing us to study the drag signal in nearly pristine
quantum wires. Surprisingly, a non-reciprocal component with strength comparable to that of the reciprocal component is still detected across the measured regime, despite the drag wire being ballistic. We suggest that the non-reciprocal signal arises from low energy disorder in the device, which is consistent with the
evolution of the drag wire's conductance at low biases voltages and temperatures. Additionally, the non-reciprocal component of the drag signal shows a power-law temperature dependence that coincides with a diffusive model, while the reciprocal component's temperature dependence cannot be explained under the existing framework. The bias voltage dependence of the drag wire conductance is fitted into three models to extract the interaction parameter and disorder level within the wire, but none of the models provides a fully self-consistent explanation for the data.
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All authors Suyang Cai, Mingyang Zheng, Nathan Rao, Glen Gillia, Rebika Makaju, Sadhvikas J. Addamane, Dominique Laroche
Materials Science
A new method to probe conducting filaments in MoS$_2$-based memristors
Pierre Trousset, Lucie Le Van-Jodin, Bruno Reig et al. (+7 more)
Two-dimensional (2D) transition metal dichalcogenides (TMDs), such as molybdenum disulfide (MoS$_2$), are emerging as promising materials for next-generation electronic devices. They have proved to be serious candidates for integration with memristors in non-volatile
memory and
radio frequency (RF) applications. However, the physical mechanisms behind their resistive switching, particularly the formation and resorption of conducting filaments, remain unclear. In this study, we present a novel mechanical exfoliation technique that selectively removes the top metallic electrode from MoS$_2$-based memristors by exploiting the weak van der Waals interaction between MoS$_2$ and the top electrode. This method enables direct and multi-scale characterization of the MoS$_2$ surface in different states (initial, ON and OFF) using Kelvin Probe Force Microscopy (KPFM) and Raman spectroscopy mapping. To complete this study, cross-sectional Transmission Electron Microscopy (TEM) was also performed in different conductive states. Our results reveal that the conducting filament is formed by metallic atom migration from the top electrode into the MoS$_2$ layer. Additionally, we demonstrate that the choice of metallic electrodes (gold vs. nickel) significantly impacts the switching behavior due to differences in adsorption and
diffusion energies. This work not only clarifies the filament formation mechanism and introduces a reproducible approach for in-operando characterization but also represents a real progress in the understanding and optimization of 2D material-based memristors.
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All authors Pierre Trousset, Lucie Le Van-Jodin, Bruno Reig, Clotilde Ligaud, Thomas Jalabert, Hanako Okuno, Le Van-Hoan, Paul Brunet, Stéphane Cadot, Matthieu Jamet
Statistical Mechanics
Emergent heavy-tailed distributions from a Markovian random walk
Henrique S. Lima and Evaldo M. F. Curado
The emergence of heavy-tailed statistics in complex systems is conventionally attributed to non-local
stochastic jumps or non-Markovian
memory. Here, we present a one-dimensional random walk where power-law behaviors arise instead from a strictly local, discrete-time Markovian mechanism. The step length is governed by a deterministic function of the walker's position, establishing a positive feedback loop that induces strong effective correlations along the trajectories. Through analytical derivations in the continuum limit and extensive numerical simulations, we show that this rule yields a robust, non-Gaussian stationary state. The exact analytical solution is obtained in the closed form of a symmetric, Lorentz-like distribution, $\rho_{\text{st}}(x) \propto (|x|/l+r\Delta x)^{-2}$, confirming asymptotic power-law tails that decay as $|x|^{-2}$ over six decades. Furthermore, by employing the Onsager-Machlup path-integral formalism, we demonstrate that effective velocity and acceleration acquire physical meaning along the shortest fluctuation trajectories. Crucially, we find that a non-zero initial acceleration acts as the fundamental mechanism driving the walker away from the origin, ensuring both the emergence of scale-free statistics and the normalizability of the stationary distribution. This minimal pathway provides a new microscopic foundation for the widespread $-2$ power law observed across multidisciplinary complex systems.
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Materials Science
Thickness-Dependent Spintronic Terahertz Emission in MBE-Grown PtTe$_2$: From Semiconductor to Type-II Dirac Semimetal
Rahul Sharma, Sylvain Massabeau, Armando Pezo et al. (+13 more)
Spintronic terahertz (THz) emitters have established themselves as among the most practical broadband THz sources available, yet their performance remains fundamentally limited by the
spin Hall conductivity of the nonmagnetic conversion layer - a quantity that is fixed once the material is chosen. Here, we demonstrate that in PtTe$_2$, a type-II Dirac semimetal within the transition metal dichalcogenide family, this limitation can be circumvented by exploiting the dramatic thickness-driven electronic phase
evolution of the material itself. Using molecular beam epitaxy to grow PtTe$_2$ films with single-monolayer precision from 1 to 20 ML, we show that the spintronic THz emission tracks the underlying electronic phase diagram directly: it is absent in the single-layer semiconducting phase, turns on sharply at the semimetal transition near 2 ML, and reaches a peak amplitude six times that of an equivalent Pt reference at 10 ML, before declining at larger thicknesses due to THz reabsorption in the increasingly metallic film. This non-monotonic behavior is inconsistent with a bulk inverse
spin Hall mechanism and instead reflects a multi-channel
spin-to-charge conversion process in which
spin-momentum-locked topological surface states and a thickness-dependent interfacial Rashba splitting both contribute and strengthen as the type-II Dirac band structure develops. First-principles calculations of the interfacial
spin accumulation reproduce the experimental trend quantitatively, confirming this physical picture. These findings introduce thickness engineering of van der Waals semimetals as a new and accessible route to optimizing spintronic THz emitters and
spin-orbit torques in
magnetic memories (SOT-MRAMs), with direct implications for the broader class of dimensionally tunable topological materials.
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All authors Rahul Sharma, Sylvain Massabeau, Armando Pezo, Ekta Yadav, Viliam Vretenár, Ravi K. Biroju, Fatima Ibrahim, Sukhdeep Dhillon, Alain Marty, Isabelle Gomes de Moraes, Adrien Michon, Jing Li, Mairbek Chshiev, Henri Jaffrès, Jean-Marie George, Matthieu Jamet
Disordered Systems and Neural Networks · Cross-listed from quant-ph
Observation of associative-memory retrieval and spin-glass phases on a photonic quantum simulator
Taira Giordani, Gennaro Zanfardino, Luca Leuzzi et al. (+16 more)
Models of interacting complex systems provide the fundamental statistical physics reference frame for the study and the understanding of associative
memories, machine learning, and the dynamics of neural networks. On the other hand, simulating complex multi-synaptic interactions on a classical hardware is computationally demanding due to the super-linear scaling of the system complexity. Photonic
quantum technologies provide a promising solution to these limitations by leveraging on their inherent speed and parallel processing ability in order to simulate complex networks. Recently, a connection between multiphoton processes and generalized $p$-body Hopfield models has been theoretically established. Here, we design and demonstrate an experimental platform that exploits single
photons distributed across a set of optical modes, in which controlled arrays of binary phase shifters act as Ising-like
neurons. We focus specifically on a fully connected Hopfield
Hamiltonian with four-body local interaction terms, realized via two-
photon processes. Through
quantum simulations on programmable photonic processors, the study identifies three distinct regimes: a
memory retrieval phase, a
spin-glass
memory "black-out" phase, and a paramagnetic phase. Experimental results confirm successful
memory retrieval at low storage capacities and temperatures, where the system consistently relaxes to fixed points with high
memory overlap, effectively reconstructing the stored patterns. Future research will extend the platform design to investigate networks with local or dilute interactions, while advances in the realization of scalable photonic
circuits will enable architectures that encompass very large numbers of interacting
spins.
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All authors Taira Giordani, Gennaro Zanfardino, Luca Leuzzi, Enrico Bonfissuto, Eugenio Caruccio, Gabriele Gasbarri, Mattia Bossi, Abhiram Rajan, Riccardo Albiero, Francesco Ceccarelli, Nicolò Spagnolo, Raffaele Santagati, Stefano Paesani, Marco Leonetti, Roberto Osellame, Giorgio Parisi, Giancarlo Ruocco, Fabrizio Illuminati, Fabio Sciarrino
Quantum Gases · Cross-listed from hep-ph
Scale-Invariant Open Quantum Systems
Carlos Argüelles, Gabriela Barenboim, Gonzalo Herrera et al. (+2 more)
We develop a complete theoretical framework for open
quantum systems coupled to scale-invariant environments. We show that such environments are universally described by unparticle baths characterized by a single scaling dimension $d_{\mathcal{U}}$. This work provides the proof of the uniqueness
theorem, the formalism of the resulting non-Markovian dynamics, and applications to several physical systems. From the uniqueness
theorem, we derive the non-Markovian
memory kernels, the exact noise kernel including
vacuum and thermal contributions, and a fractional generalization of the Caldeira-Leggett master equation for arbitrary $d_{\mathcal{U}}$. The scaling dimension governs a rich phase structure, including a thermalization transition at $d_{\mathcal{U}}=3/2$, the Ohmic boundary at $d_{\mathcal{U}}=2$, and a decoherence transition at $d_{\mathcal{U}}=5/2$ in the thermal regime, beyond which long-time
quantum coherence is protected. Three realizations are studied. For the
quantum Ising model at criticality, coupling to the energy operator in $(1+1)$ dimensions gives $d_{\mathcal{U}}=3/2$, producing $1/f$ noise, while the $(2+1)$D case yields $d_{\mathcal{U}}\approx1.413$ from the conformal bootstrap. In inflationary cosmology, massless scalar and graviton baths in de Sitter spacetime give $d_{\mathcal{U}}=2$, predicting linear decoherence growth consistent with the
quantum-to-classical transition. For high-energy astrophysical
neutrinos, the decoherence rate $\Gamma_{\mathrm{decoh}}\propto \mathcal{B}(E,T_{\mathcal{U}})L^{5-2d_{\mathcal{U}}}$ provides an observable signature of the scaling dimension. We also compare the framework with Caldeira-Leggett and Lindblad approaches, analyze the validity regimes, and discuss experimental implications for trapped-ion simulators,
neutrino telescopes, and superconducting
qubits.
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All authors Carlos Argüelles, Gabriela Barenboim, Gonzalo Herrera, Tanvi Krishnan, Héctor Sanchis
Statistical Mechanics · Cross-listed from quant-ph
Quantum Fisher Information under decoherence with explicit wavefunctions
Francesco Musso, Vittorio Vitale and Sara Murciano
We present a method to estimate the
quantum Fisher information (QFI) of many-body
quantum states in the presence of decoherence, where its direct evaluation requires the full spectral resolution of the density
matrix. We show that, for many-body wave functions known analytically in the occupation-number basis, systematic lower bounds to the QFI can be mapped onto expectation values over a classical probability distribution defined by the wave function amplitudes. This mapping enables efficient estimation via Markov-chain Monte Carlo sampling, with a computational cost that scales as a `slow' exponential ($e^{b L}$ with $b \lesssim 0.6$) and remains manageable for system sizes well beyond exact diagonalization. We specify this framework to Jastrow-Gutzwiller wave functions. We characterize their metrological content by identifying the observables that maximize the QFI and the corresponding scaling with $L$. Then, we analyze the QFI under three physically motivated noise channels: local dephasing, local amplitude damping, and global depolarizing. We compare
polynomial and Krylov-based lower bounds across these channels, relating their behavior to the effective rank of the noisy density
matrix and to the structure of the operator generating the parameter encoding. The framework extends naturally to other analytically known wave functions and to a broader class of information-theoretic quantities beyond the QFI.
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Statistical Mechanics · Cross-listed from quant-ph
Unified resonant-manifold framework for dynamical quantum phase transitions
Jesse J. Osborne, Cheuk Yiu Wong and Jad C. Halimeh
Dynamical
quantum phase transitions (DQPTs) are an exciting paradigm of out-of-
equilibrium criticality in many-body systems manifested in nonanalytic behavior in the return rate to the initial state following a sudden quench. While previous work has tried to distinguish between distinct types of DQPTs, such as regular and anomalous, or
manifold and branch, a comprehensive understanding of why each type appears in a given scenario is still lacking. In this work, we propose a unified framework addressing this gap in terms of the energy structure of different product state configurations. In particular, while
manifold DQPTs are governed by resonances within the initial state
manifold, branch DQPTs are governed by resonances with a transitional
manifold of states dynamically connected to the initial
manifold by low-order processes. We show that the (ir)regularity of branch DQPTs is related to the multiplicity of this transitional
manifold, and we also observe exotic periods of extended degeneracy in the return rate (beyond the conventional level crossing of a DQPT) which are also conditioned on the structure of this transitional
manifold. We demonstrate this by studying quenches of two different configurations in the 1 + 1D Z_2 LGT to various parameter regimes. Our findings provide a dynamical mechanism underlying branch DQPTs and frames DQPTs as probes of resonant connectivity in constrained
Hilbert spaces, paving the way to a more complete understanding of the multifaceted nature of dynamical criticality.
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Strongly Correlated Electrons
Fractionalization, emergent SU($N$) symmetries, and fragmentation in layered quantum spin-orbital models
Pedro M. Cônsoli, Aayush Vijayvargia and Onur Erten
We propose a family of layered
quantum spin-orbital models as a platform to study fractionalization, unconventional forms of
symmetry-breaking order, and their possible coexistence. The models are built by stacking $N$ layers of a square-
lattice system in which Kitaev-type interactions promote the formation of a $\mathbb{Z}_2$
quantum spin-orbital
liquid and coupling the different layers via Ising
spin interactions. Using a parton construction, we show how, at low energies, these
Hamiltonians can be mapped to $N$-component
Fermi Hubbard models on a $\pi$-flux square
lattice at half filling. We also demonstrate that the models acquire an emergent SU($N$)
symmetry in the limit of equal all-to-all interlayer couplings and argue that, for $N>2$, the proximity to this limit offers the potential to realize an array of competing phases. To illustrate this point, we compute the zero-temperature phase diagram of the effective $N=3$ Hubbard model within mean-field theory and uncover rich phenomena, including intertwined orders and
flavor-selective localization. Mapping back to the original degrees of freedom reveals that the ground states realize distinct forms of
magnetic fragmentation, wherein the orbitals remain in a
quantum liquid state whereas the
spins can present conventional long-range order or nonlocal order characterized by a nontrivial string order parameters. We highlight possible extensions of our construction as well as its potential to provide concrete microscopic models for different fractionalized
quantum critical points.
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Quantum Gases
Weak wave turbulence as a precursor to universal coarsening in a homogeneous Bose gas
Simon M. Fischer, Martin Gazo, Sebastian J. Morris et al. (+6 more)
Relaxation and condensation of an isolated low-energy Bose gas provide an ideal setting for the study of the universal features of far-from-
equilibrium many-body dynamics and the emergence of long-range order. Conceptually, the emergence of such order involves two steps: the formation of local coherence, on a system-specific microscopic lengthscale, and the spreading of coherence, over lengthscales much larger than any microscopic scale. The latter is understood in terms of universal phase-ordering kinetics, or coarsening, characterized by an algebraic growth of the coherence length. Here, for a homogeneous Bose gas with tunable interactions, we show that the former also has a universal description, within the framework of weak wave
turbulence (WWT). Specifically, the initial transport of particles to low momenta corresponds to an inverse turbulent cascade that is, in agreement with the WWT theory, characterized by a power-law momentum distribution, with exponent $\gamma = 2.4(1)$, and transport times ${\propto} (na)^{-2}$, where $n$ is the gas density and $a$ the $s$-wave scattering length.
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All authors Simon M. Fischer, Martin Gazo, Sebastian J. Morris, Nikolai Maslov, Haoyu Zhang, Jiří Etrych, Gevorg Martirosyan, Christoph Eigen, Zoran Hadzibabic
Materials Science
Genome-Guided Interpretable Screening of Phase-Stable, Lead-Free Double Perovskite Absorbers for All-Inorganic Semiconductors, Sensors, and Photovoltaics with DFT-Validated Design Rules
Nafis Ahtasu, Sohanur Rahman Sohan, Md. Mostaq Ahmed Himel et al. (+6 more)
The discovery of stable, lead-free halide perovskites for optoelectronic applications is constrained by vast compositional space and limited interpretability of conventional screening approaches. We present a genome-guided, physics-informed framework that decodes thermodynamic stability and optoelectronic behavior through four physically interpretable descriptor families: packing, bonding, polarization, and electronic identity. Trained on 1,221 DFT-calculated A2BB'X6 compounds, machine-learning surrogates achieve robust predictive performance, with a recall-optimized stability classifier (ROC-AUC = 0.92) and an XGBoost regressor for band-gap prediction (R2 = 0.93 on held-out data). Applying a staged inverse-design constraint stack to 13,088 charge-balanced, lead-free compositions reduces the search space to five DFT-validated, phase-stable
semiconductors: Rb2SnMnBr6, Cs2CdSnBr6, Cs2CdSnI6, Cs2KGaI6, and Cs2AgAlBr6. These candidates lie on the convex hull (E_hull <= 0 meV/atom), preserve ordered double-perovskite structures, and exhibit strong optical absorption (alpha peak ~1e5 cm^-1). Genotype-phenotype coupling analysis reveals a hierarchical control mechanism: packing genes define structural formability, bonding genes govern near-edge optical transitions and conductivity, and optoelectronic response genes regulate dielectric response and
exciton screening (epsilon0 = 4.6-8.2). This work establishes a generalizable paradigm for interpretable inverse design, linking descriptor-level genomics to experimentally relevant optoelectronic phenotypes and providing design rules for discovering stable, lead-free double perovskites for photovoltaics, sensing, and transparent electronic applications.
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All authors Nafis Ahtasu, Sohanur Rahman Sohan, Md. Mostaq Ahmed Himel, Md. Zahid Hassan, Muhammad Harussani Moklis, Masud Rana Rashel, Hasan Jamil, AKM Kamrul Islam, Mouhaydine Tlemcani
Mesoscale and Nanoscale Physics
Signatures of the Quantum Geometric Dipole of Interlayer Excitons in Counterflow Conductivity
Fanuel I. Mendez, Luis Brey and H.A. Fertig
Collective excitations of many-body electron systems can carry internal structure, supporting novel
quantum geometric and topological properties. Among these are a
quantum geometric dipole (QGD), which for
excitons have direct significance as an internal polarization. For interlayer
excitons of a
bilayer system, this represents an in-plane dipole moment, which can be used to drive them with in-plane electric fields. In this work, we consider counterflow electric currents associated with driven
excitons in such a
bilayer system as a probe of their QGD structure. As a simple but non-trivial example, we analyze a structure with a one-dimensional periodic potential in a strong perpendicular
magnetic field. The resulting magnetoexciton bands host QGD structure that distinguishes it from the
exciton QGD of a uniform system. To model
exciton transport we adopt a Boltzmann approach that includes inter-band tunneling, allowing us to consider non-
equilibrium momentum distributions that result from strong layer-antisymmetric driving fields. We show how linear response to a layer-symmetric component of the driving fields provide information about the QGD, and that the broad QGD structure of the
exciton bands can be probed by the varying the layer-antisymmetric field. Our results demonstrate that counterflow conductivity serves as a tunable probe of the internal
quantum geometric structure carried by the interlayer
excitons, connecting transport to the
quantum geometry of many-body excitations.
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Disordered Systems and Neural Networks · Cross-listed from math.PR
Persistence of asymptotic variance under transport: from hyperfluctuation to stealthy hyperuniformity
Luca Lotz and Michael A. Klatt
We introduce $p$-uniformity to characterize the scaling of density fluctuations in spatial random systems in $\mathbb R^d$, ranging from hyperfluctuation to stealthy hyperuniformity. Our central
theorem establishes sufficient conditions to preserve $p$-uniformity under transport. The first condition, a finite $(d+p)$-th moment of the transport distance, allows for a Taylor expansion of the transport. The second condition controls the corresponding terms. We thus solve a previously stated open problem; indeed we extend it, since our result applies to a general $p$-uniform source in any dimension, and the source and transport may be dependent. As an application, we construct new classes of point processes that are isotropic and $p$-uniform with arbitrarily high $p$, and that can be simulated in linear time. We thus achieve three-dimensional isotropic hyperuniform samples with an unprecedented system size of $10^9$ points. We conclude with an outlook on a converse statement.
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Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Local projective reconstruction of driven bosonic Hamiltonians
A. M. Tishin
Inferring a
Hamiltonian from a single
quantum trajectory is generally non-unique. This ambiguity limits inverse use of projective
quantum geometry. Here we show that a nearest-neighbour structural prior makes the problem locally identifiable. For a smooth real time-dependent Jacobi
Hamiltonian initialized at a ladder endpoint, the physical-time projective jet through order M+1 reconstructs the first M couplings, their logarithmic rates, and diagonal energy differences, up to an overall scalar-energy gauge. A canonical osculating-frame representation encodes the same data in a gauge-fixed connection. Pair-driven bosonic dynamics provides a direct realization because the
vacuum evolves on the even-Fock Jacobi chain. In a nonstationary test, shallow reconstructions fit early projective data yet strongly overpredict later occupation growth; adding the projective order that resolves each hidden nonlinear layer restores the self-limited dynamics. The result supplies an inverse local counterpart to forward Krylov/Lanczos constructions and specifies when phase-resolved short-time state information identifies a sparse driven
Hamiltonian.
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Soft Condensed Matter
Hollow Needle Puncture Mechanics for Biopsy Sampling
Yiting Wu, Frederic Lechenault, Matteo Ciccotti et al. (+1 more)
Biopsy sampling relies on hollow needles that puncture soft tissues by propagating and opening a cylindrical crack, yet the mechanics governing this coring process remain only partially understood. Motivated by this gap, we develop a simple, energy based model for puncture by blunt hollow needles, grounded in brittle fracture mechanics and extended to include frictional interactions at the needle tissue interface. The model describes puncture as the competition between the fracture energy and the elastic energy. This energetic balance is controlled by the interplay among needle geometry (radius and wall thickness), material properties (toughness and elastic modulus), and interfacial parameters (adhesion and friction). This model provides semi-analytical predictions for five key quantities: core size, frictionless force, frictional force slope, critical insertion depth, and critical insertion force. Model predictions are validated against experiments, demonstrating that friction significantly improves force estimation and alters the puncture regime. These results offer quantitative insight into the mechanics of tissue coring and force generation during biopsy, providing a predictive foundation for needle design, sampling performance, and real time control in robotic biopsy and needle insertion systems.
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All authors Yiting Wu, Frederic Lechenault, Matteo Ciccotti, Mattia Bacca
Materials Science
Atomic scale demonstration of ferromagnetism in a single layer FeCl2 on Au(111)
Adriana E. Candia, Eliecer Peláez-Sifonte, Amitayush Jha Thakur et al. (+8 more)
FeCl2 is a promising single-layer material with sizeable
magnetic susceptibility and insulating character that can be easily grown by molecular beam epitaxy on various surfaces. In order to include it into the select palette of van der Waals materials used to engineer functional
heterostructures, it is necessary to confirm its
magnetic and electronic ground states, and understand the influence of the supporting substrate. In this work, we unambiguously demonstrate
ferromagnetic ordering in a single-layer FeCl2 on Au(111) by means of
spin-polarized scanning tunnelling microscopy. The material features a relatively wide insulating gap of 3.3 eV and a strongly
spin-polarized conduction band that emerges at 1.5 eV above the
Fermi level. Atomic scale defects with triangular shape play a primary role in the electronic gap and
spin density distribution. Specifically, in a region of 1.6 nm around each defect, the conduction band is locally suppressed and the tunnelling magneto-conductance is reduced a factor of four. By tracking the
spin-dependent tunnelling conductance as a function of the applied
magnetic field, we record atomically resolved hysteresis loops, revealing a soft
ferromagnetic ground state with pronounced out-of-plane anisotropy and coercive fields in the range of 15-50 mT.
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All authors Adriana E. Candia, Eliecer Peláez-Sifonte, Amitayush Jha Thakur, Sebastien E. Hadjadj, Samuel Kerschbaumer, Aymeric Saunot, Martina Corso, Maxim Ilyn, Jorge Lobo-Checa, Celia Rogero, David Serrate
Superconductivity · Cross-listed from astro-ph.HE
J. A. Sauls
The interior crust and much of the
liquid core of
neutron stars is believed to be a
quantum liquid mixture of
neutron and
proton superfluids and a relativistic electron
liquid. Quantized
vortices in the
neutron superfluid and quantized flux lines in the
proton superconductor are topological defects of these hadronic condensates. I consider the formation of the superfluid state in young
neutron stars under non-
equilibrium conditions imposed by the
neutrino cooling rate. The nonequilibrium phase transition implies that the onset of superfluidity is accompanied by the generation of quantized
vortices based on the mechanism envisioned by Kibble in the context
cosmic string formation in an evolutionary models of an expanding universe, and further developed by Zurek for nonequilibrium phase transitions in
quantum liquids such as $^4$He. I discuss the Kibble-Zurek mechanism (KZM) and scaling relations for topological defect formation starting from the Cooper pair fluctuation propagator for temperatures approaching $T_c$. I then calculate the predicted
vortex densities based on Urca and modified Urca cooling mechanisms in the cores of
neutron stars for several models of the superfluid gap and transition temperature of the interior
neutron superfluid. In all cases studied the KZM leads to a large density of topological defects in the condensate phase, which in 3D form a random network of
vortex lines and loops, i.e. the generation of
quantum turbulence.
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Disordered Systems and Neural Networks
Spin Glass Mapping of the Parallel Minority Game
Aryan Tyagi, Soumyaditya Das, Soumyajyoti Biswas et al. (+1 more)
The parallel minority game (PMG) extends the classical minority game to many choices, with each
agent restricted to two predetermined alternatives. In this condition, minimizing the population variance across all choices is a complex combinatorial optimization problem. We show that this minimization is exactly equivalent to finding the ground state of an Ising
spin glass in the mean-field limit, i.e., the Sherrington-Kirkpatrick model. By encoding the
agent choices as
spin variables, the variance becomes a quadratic
Hamiltonian with quenched random couplings $J_{ij}$ and random fields $h_i$. This mapping reveals inherent frustration and connects the PMG to the well developed theory of
spin glasses, providing a new perspective on the frozen, sub-optimal configurations observed in
stochastic strategies.
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All authors Aryan Tyagi, Soumyaditya Das, Soumyajyoti Biswas, Anirban Chakraborti
Soft Condensed Matter
Topological cell-openness index for porous materials
Michał Bogdan and Paweł Dłotko
We propose a method of estimating and parametrising the proportion of open and closed
cells in a porous material based on measuring Betti numbers on the structures. We define a
cell-openness index {\tau} which can be used to complement the proportion of open-celled volume reported by gas pycnometry, which is the current gold standard for pore type characterization. We discuss in what types of structures mismatches between the two measures can occur and how such mismatches convey additional information about the structure. We demonstrate examples of significant correlations between {\tau} and measurable physical quantities in both numerical and experimental structures. We also discuss how Betti curves can be used to estimate characteristic feature sizes in porous structures.
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Mesoscale and Nanoscale Physics
Signatures of quantum chaos in phonon-polariton billiards
Yinan Dong, Felix Liu, Ekrem Demirboga et al. (+11 more)
We use scanning near-field optical microscopy to image
hyperbolic phonon polaritons in hexagonal boron nitride (hBN) billiards with integrable and chaotic geometries. In Sinai billiards, we observe irregular mode patterns consistent with
quantum scarring, together with an unexpected sensitivity to weak probe perturbations. These random-wave features coexist with non-chaotic one-dimensional boundary modes arising from nontrivial polariton reflection at the billiard edge. As the billiard boundary becomes increasingly complex, the
Fourier transforms of the measured signals evolve toward ring-like structures consistent with Berry's random-wave
conjecture. We develop a numerical framework based on the Helmholtz equation with generalized boundary conditions that encode angle-dependent reflection phase shifts. The calculated level statistics exhibit a crossover from Poisson-like behavior in integrable billiards to Wigner-Dyson-like behavior in chaotic geometries, with small deviations from the canonical form arising from nonlinear boundary conditions that require self-consistent bulk-boundary analysis. Theoretical analysis based on dissipative Green's functions qualitatively reproduces the near-field data. These results establish mesoscopic van der Waals billiards as a rich platform for studying generalized chaotic dynamics of hybrid light-matter polaritons.
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All authors Yinan Dong, Felix Liu, Ekrem Demirboga, Andrey Grankin, Dihao Sun, Yuchen Lin, Lukas Wehmeier, Matthew Fu, Cory R. Dean, Song Liu, James H. Edgar, Michael M. Folger, Victor M. Galitski, Dmitri N. Basov
Mesoscale and Nanoscale Physics
Monitored quantum transport through a disordered one-dimensional conductor
J. Sánchez Fernán, J. Tworzydło and C. W. J. Beenakker
We formulate a
quantum master equation for the many-particle density
matrix of electrons propagating through a single-mode conductor, combining elastic scattering by disorder with time-resolved projective measurements that monitor the outcome of scattering events. The full counting statistics of transmitted electrons has a binomial distribution function, whose mean ${\cal T}$ and variance ${\cal T}(1-{\cal T})$ determine the conductance and shot noise power, respectively. Monitoring suppresses the phase coherence responsible for one-dimensional localization: The decay with conductor length $L$ of the typical transmission probability crosses over at $L\simeq \ell_\phi$ from the exponential $e^{-L/\xi}$ (with localization length $\xi$) to the Ohmic $1/L$ decay. Numerical solution of the master equation gives, for weak monitoring, a logarithmic dependence $\ell_\phi\simeq \xi\ln(v_{\rm F}\tau_\phi/\xi)$ of the coherence length $\ell_\phi$ on the mean time $\tau_\phi$ between measurements.
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Statistical Mechanics · Cross-listed from cs.LG
Latent Spectroscopy: Posterior Collapse as a Feature
Johannes Hirn
We show that, in linear Gaussian VAEs, posterior collapse is a form of latent feature selection. Feature importance is set by each latent coordinate's contribution to reconstruction, itself given by the corresponding PCA
eigenvalue. Varying the regularizer strength $\beta$ reveals a ranked spectrum of collapse events, with thresholds set by the utility/PCA spectrum. A mode-by-mode analysis identifies the scale-invariant signal fraction as an order parameter obeying Landau scaling near collapse. WorldClim experiments confirm both the utility-threshold calibration and the predicted near-collapse scaling.
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Disordered Systems and Neural Networks
Directed extended-range percolation
Wenbo Liu, Yiwen Zeng, Xueming Liu et al. (+1 more)
While for standard percolation directionality is known to increase the combinatorial complexity of percolation, here we show that when connectivity is ensured by paths of length $R\geq 2$, network directionality, impeding backtracking, can significantly reduce the complexity of percolation. To illustrate this finding, we introduce Directed Extended-Range Percolation (DERP), defined directed networks with non-reciprocal edges, motivated by applications in
quantum communication. In this framework, message transmission is enabled between trusted nodes separated by a directed path of length at most $R$. Using a message-passing approach, we show that directionality enables an exact determination of the percolation threshold and the anomalous critical indices on locally tree-like structures. On random directed networks we find that the critical behavior of DERP depends sensitively on degree correlations. These analytical predictions are corroborated by extensive Monte Carlo simulations, highlighting the profound impact of directionality and correlations on long-range connectivity in complex networks.
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All authors Wenbo Liu, Yiwen Zeng, Xueming Liu, Ginestra Bianconi
Disordered Systems and Neural Networks · Cross-listed from hep-th
Ising surface defects can get dirty
António Antunes, Apratim Kaviraj and Baishali Roy
Real critical systems, such as uniaxial ferromagnets in the 3d Ising universality class, are constrained by boundaries and subject to random couplings. We consider the Wilson-Fisher fixed point in $4-\epsilon$ dimensions subject to a random
magnetic field localized on a two-dimensional surface, which becomes co-dimension 1 in the physical $\epsilon\to1$ limit. Using the replica method for the disordered field, we find that the ordinary boundary condition is stable under disorder but also discover a non-trivial “dirty" boundary condition which can be reached by tuning the disorder strength or the local temperature. We also investigate the logarithmic structure of the defect spectrum and how it emerges via the replica formalism.
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Materials Science · Cross-listed from cs.HC
Summarizing Time-Varying Digital Image Correlation Strain Fields Using Sankey Diagrams
Victor Persson, Christofer Boo, Mohit Sharma et al. (+1 more)
Digital Image Correlation (DIC) enables dense, time-resolved measurement of surface strain in deforming materials, providing insight into strain localization and failure mechanisms. However, the resulting strain fields are typically explored frame-by-frame through spatial visualizations, making global temporal patterns difficult to discern. We present a visual summarization approach that represents the
evolution of high-strain regions as a single Sankey diagram constructed from superlevel sets of the von Mises equivalent strain field. By tracking connected components over time via spatial overlap, the diagram encodes the birth, persistence, merging, and disappearance of strain concentrations. Applied to four tensile test
datasets with varying notch geometries, the approach compactly captures differences in deformation regimes and qualitative precursors to failure, complementing traditional spatial strain visualizations with a global temporal overview.
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All authors Victor Persson, Christofer Boo, Mohit Sharma, Ingrid Hotz
Materials Science
A Local Probe Mass Spectrometer for Localized and Sensitive Product Detection in Environmental Electron Microscopy
Saleh Firoozabadi, Timofei Ivanov, Frederik Stender et al. (+4 more)
Aberration-corrected environmental transmission electron microscopy (ETEM) enables atomic-resolution imaging of dynamic catalytic processes. Correlating atomic-scale structural changes with reaction products detected by mass spectrometry offers a powerful route to uncover catalytic mechanisms. However, current approaches face fundamental limitations: closed-
cell ETEM setups suffer from diffuse scattering by SiN windows, degrading spatial resolution and sensitivity, while open-
cell configurations enable high-resolution imaging and maintain high sensitivity but suffer from significant dilution of reaction products during transport to the mass spectrometer (MS). To overcome these challenges, we develop a Local Probe Mass Spectrometer (LPMS) integrated with aberration-corrected ETEM. The setup combines a DENSsolution Stream holder with a MS. To preserve spatial resolution, both top and bottom SiN membranes of the MEMS chip are removed, while the gas environment is maintained via the ETEM chamber. Reaction products are sampled locally via a micro-capillary positioned near the catalyst and connected to a holder gas line that delivers the gas to the MS. Initial validation in environmental SEM confirmed controlled gas delivery to the MS. Co3O4 nanoplates serve as a model catalyst due to their inherent electron transparency, enabling atomic-resolution imaging without FIB lamella preparation and associated ion-beam damage. A novel micro-shuttle transfer strategy enables controlled placement of a defined number of nanoplates at the reaction site with precise crystallographic orientation. This establishes the foundation for quantitative structure reactivity correlation by enabling simultaneous, spatially resolved detection of reaction products and atomic-scale structural dynamics.
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All authors Saleh Firoozabadi, Timofei Ivanov, Frederik Stender, Julian Grahl, Stephan Schulz, Christian Jooss, Tobias Meyer
Mesoscale and Nanoscale Physics
Spintronic Neuromorphic Hardware Using Domain Wall-Based Neurons and Quantized Synapses
Sakshi Kiran Bandekar, Arnab Ganguly, Debanjan Polley et al. (+1 more)
In this work, we simulate the functionality of an artificial
neuron and synapse using
spin-orbit torque-based spintronic devices and implement a fully connected artificial neural network (ANN). These neuro-synaptic devices are emulated via transverse domain wall dynamics within a rectangular
magnetic nanotrack comprised of heavy-metal (HM)/ferromagnet (FM)
heterostructures. Here, the
heterostructure is parameterized using Pt-based
alloys for the HM layer and CoFeB for the FM layer. The ReLU activation function of the
neuron has been mimicked using the domain wall (DW) motion induced by a 3 ns current pulse. The synapse is modeled using current-induced DW dynamics with a corrugated HM/FM nanotrack. Semicircular notches are symmetrically positioned along both edges of the nanotrack to serve as pinning sites. By applying 10 ns current pulses of varying current densities, we achieve controlled, stepwise DW motion characterized by temporary pauses at consecutive pinning centers. The electrical conductance of the pinned DW across various pinning points act as stable synaptic weights for our ANN. Furthermore, we observe a threshold-dependent delay effect where each depinning event is influenced by previous ones, successfully mimicking synaptic states and adaptability in neuromorphic systems. The fully connected ANN has been modeled using the conventional float32 synaptic weights for the MNIST and Fashion-MNIST
datasets with an accuracy of ~97% and ~86%, respectively, which serves as a test bed for our neuromorphic simulations. To implement a sparse and low-
memory-footprint ANN, we quantize the trained synaptic weights into discrete quantized levels and tested the network, which demonstrate an accuracy of ~95% and ~62% for the MNIST and Fashion-MNIST
datasets, respectively.
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All authors Sakshi Kiran Bandekar, Arnab Ganguly, Debanjan Polley, Debasis Das
Strongly Correlated Electrons
Nonlinear Magnon Magnetic Moment Transport in Triangular-Lattice f-Wave Antialtermagnets
Volodymyr P. Kravchuk, Kostiantyn V. Yershov, Bastián Pradenas et al. (+6 more)
We study the
spin excitations in the frustrated coplanar 120-degree ground state of the triangular-
lattice Heisenberg antiferromagnet and demonstrate that they carry a
magnetic moment perpendicular to the plane in which the
spins order, despite the ground-state sublattice moments having no out-of-plane component. The
symmetry of the momentum dependence of the
magnetic moment and energy of the
magnons renders the system an odd-parity f-wave magnet. Extending this model to a stack of antiferromagnetically coupled triangular layers provides a realization of
magnons in a three-dimensional f-wave antialtermagnet. We show that nonlinear thermal transport effects of
magnons, such as Edelstein and
spin-splitter effects, provide clear experimental signatures of
magnons in f-wave antialtermagnets.
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All authors Volodymyr P. Kravchuk, Kostiantyn V. Yershov, Bastián Pradenas, Robin R. Neumann, Rodrigo Jaeschke-Ubiergo, Ricardo Zarzuela, Jairo Sinova, Jeroen van den Brink, Alexander Mook