Materials Science · Cross-listed from physics.app-ph
Electron Emission Yield Datasets Under Electron Impact From Surfaces Characterized In Situ by XPS or AES
M.Belhaj and S. dadouch
We present the measurement, characterization, and calibration procedures used to produce a series of
datasets for various conductive and semiconductive materials. The data, provided, include emission yields as a function of incident electron energy together with surface composition obtained from X-Ray Photoelectron Spectroscopy or Auger Electron Spectroscopy analyses. Initial
datasets cover copper and gold, with additional materials to be released on arXiv.
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Disordered Systems and Neural Networks
Order parameter for non-mean-field spin glasses
Michele Castellana
We propose a novel renormalization group (RG) method for non mean-field models of
spin glasses, which leads to the emergence of a novel order parameter. Unlike previous approaches where the RG procedure is based on a priori notions on the system, our analysis follows a minimality principle, where no a priori assumption is made. We apply our approach to a
spin-glass model built on a hierarchical
lattice. In the RG decimation procedure, a novel order parameter spontaneously emerges from the system
symmetries, and self-similarity features of the RG transformation only. This order parameter is the projection of the
spin configurations on the ground state of the system. Kadanoff's majority rule for
ferromagnetic systems is replaced by a more complex scheme, which involves such novel order parameter. The ground state thus acts as a pattern which translates
spin configurations from one length scale to another. The rescaling RG procedure is based on a minimal, information-theory approach and, combined with the decimation, it yields a complete RG transformation. Below the upper critical dimension, the predictions for the critical exponent $\nu$, which describes the critical divergence of the correlation length, are in excellent agreement with numerical simulations from both this and previous studies. Overall, this study opens new avenues in the understanding of the critical ordering of realistic
spin glasses, and it can be applied to
spin-glass models on a cubic
lattice and nearest-neighbor couplings which directly model
spin-glass materials, such as AuFe, CuMn and other
magnetic alloys.
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Soft Condensed Matter
Calibration of a DEM contact model for wet industrial granular materials
Sahar Pourandi, P. Christian van der Sande, Igor A. Ostanin et al. (+1 more)
This study presents and calibrates a Discrete Element Method (DEM) contact model for wet granular materials in the pendular regime. The model extends a previously calibrated dry contact formulation by incorporating
liquid bridges that generate capillary adhesion between particles, while
liquid migration is represented through evolving bridge volumes. Two reactor-grade polypropylene powders with different particle size distributions, bulk densities, and surface morphologies are investigated, resulting in distinct wetting behavior. A schematic framework is introduced to relate increasing
liquid content to the transition from dry to wet contacts using two key parameters: the minimum
liquid film volume and the maximum
liquid bridge volume. These parameters are calibrated using dynamic angle of repose measurements from rotating drum experiments. The calibrated model reproduces the experimental flow behavior of both powders: full agreement is obtained for the coarser, more porous powder across all
liquid contents, while for the finer, denser powder, agreement is achieved at low to moderate
liquid contents. At higher
liquid contents, discrepancies arise due to agglomeration effects amplified by particle scaling. These results demonstrate the effectiveness of the dynamic angle of repose as a calibration target and highlight the limitations of particle scaling for strongly cohesive wet granular systems. The proposed framework provides a practical basis for DEM-based modeling of wet powder flow in industrial processes.
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All authors Sahar Pourandi, P. Christian van der Sande, Igor A. Ostanin, Thomas Weinhart
Soft Condensed Matter
Many interacting particles in solution. III. Spectral analysis of the associated Neumann–Poincaré-type operators
Sergii V. Siryk and Walter Rocchia
The interaction of particles in an electrolytic medium can be calculated by solving the Poisson equation inside the solutes and the linearized Poisson–Boltzmann equation in the solvent, with suitable boundary conditions at the interfaces. Analytical approaches often expand the potentials in spherical harmonics, relating interior and exterior coefficients and eliminating some coefficients in favor of others, but a rigorous spectral analysis of the corresponding formulations is still lacking. Here, we introduce pertinent composite many-body Neumann–Poincaré-type operators and prove that they are compact with spectral radii strictly less than one. These results provide the foundation for systematic screening-ranged expansions, in powers of the Debye screening parameters, of electrostatic potentials, interaction energies, and forces, and establish the analytical framework for the accompanying works arXiv:2512.09421, arXiv:2512.08407, arXiv:2512.08682.
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Soft Condensed Matter
Many interacting particles in solution. II. Screening-ranged expansion of electrostatic forces
Sergii V. Siryk and Walter Rocchia
We present a fully analytical integration of the Maxwell stress tensor and derive exact relations for interparticle forces in systems of multiple dielectric spheres immersed in a polarizable ionic solvent, within the framework of the linearized Poisson–Boltzmann theory. Building upon the screening-ranged (in ascending orders of Debye screening) expansions of the potentials developed and rigorously analyzed in the accompanying works arXiv:2512.08407, arXiv:2512.08684, arXiv:2512.09421, we construct exact screening-ranged many-body expansions for electrostatic forces in explicit analytical form. These results establish a rigorous foundation for evaluating screened electrostatic interactions in complex particle systems and provide direct analytical connections to, and systematic improvements upon, various earlier approximate or limited-case formulations available in the literature, both at zero and finite ionic strength.
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Materials Science
Engineering Topological Bands in Strained Covalent Organic Frameworks
Rebecca Peake, Zoé Truyens, Jan Mol et al. (+4 more)
The tunability of covalent organic frameworks (COFs) opens opportunities to engineer topological electronic phases, including topological
insulators (TIs) and higher-order topological
insulators (HOTIs)–materials that host in-gap states localized at their edges, hinges, or corners. Here we explore how chemically feasible perturbations can drive triazine-based COFs (CTFs) into topological regimes. Using a tight-binding model on the Honeycomb
lattice inspired by the frontier electronic states of CTFs, we show that introducing an effective uniaxial strain–implemented as a modulation of electron hopping on a subset of bonds–can generate a series of distinct topological band structures. This effect can be realized in practice through chemical substitution of linkers along the strained bonds. First-principles calculations demonstrate that replacing biphenyl with pyrene linkers drives a CTF to the brink of a HOTI phase, suggesting a viable route toward topological band-structure engineering in COFs.
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All authors Rebecca Peake, Zoé Truyens, Jan Mol, Christian B Nielsen, David Beljonne, David Cornil, Owen Benton
Materials Science
Observation of Raman anomaly and characterization of magnetic phases in van der Waals ferromagnet Fe$_5$GeTe$_2$
Sreelakshmi M. Nair, Aabhaas Vineet Mallik and R. S. Patel
Two-dimensional (2D) van der Waals (vdW) ferromagnet Fe$_5$GeTe$_2$ has garnered significant interest due to its high Curie temperature (T$_C$), large saturation magnetization, and complex
magnetic behavior arising, in part, from multiple inequivalent iron sites and vacancies. While several aspects of its complex
magnetic and structural characteristics have been examined through careful experiments and first principles studies, much of it remains debatable. In this study, we present one of the first comprehensive temperature-dependent Raman spectrum for bulk Fe$_5$GeTe$_2$ and in the process reveal an interesting peak shift anomaly at 150 K. We discuss the possible relationship of this Raman anomaly with the anomalous
lattice expansion reported earlier for this material at around 110 K. The impact of the anomalous
lattice expansion on the
magnetic anisotropy in this van der Waals material is also revealed by an isothermal magnetization analysis. These findings will prove crucial for the use of Fe$_5$GeTe$_2$ in high-performance spintronic devices.
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Quantum Gases · Cross-listed from quant-ph
Spectroscopic readout of chiral photonic topology in a single-cavity spin-orbit-coupled Bose-Einstein condensate
Kashif Ammar Yasir and Gao Xianlong
Topological photonic phases are typically identified through band reconstruction, steady-state transmission, or real-space imaging of edge modes. In this work, we present a framework for spectroscopic readout of
chiral photonic
topology in a single driven optical cavity containing a
spin-orbit-coupled Bose-Einstein condensate. We demonstrate that the cavity transmission power spectral density provides a direct and measurable proxy for a momentum- and frequency-resolved photonic Chern marker, enabling topological characteristics to be inferred from spectral data without the need for bulk-band
tomography. In the loss-dominated regime, where cavity decay exceeds atomic dissipation, the power spectral density exhibits Dirac-like gapped hybrid modes with a vanishing Chern marker, indicating a trivial phase. When the dissipation imbalance is reversed, a bright, gap-spanning spectral ridge emerges, co-localized with peaks in both the Chern marker and Berry
curvature. The complex spectrum reveals parity-time symmetric coalescences and gain-loss bifurcations, marking exceptional points and enabling
chiral, gap-traversing transport. By linking noise spectroscopy to
geometric and non-Hermitian
topology in a minimal cavity-QED architecture, this work provides a framework for spectroscopic detection of topological order in driven
quantum systems. This approach offers a pathway to compact, tunable topological photonics across a broad range of light-matter platforms, providing a method for the study and control of topological phases in hybrid
quantum systems.
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Mesoscale and Nanoscale Physics
Surface-modes mediated long-range radiative heat transfer through a plasmonic Su-Schrieffer-Heeger chain
A. Naeimi, F. Herz and S.-A. Biehs
We study the radiative heat transfer through a Su-Schrieffer-Heeger chain of plasmonic InSb nanoparticles in close vicinity of an InSb substrate. We show how the frequency bands of the in-plane and out-of-plane modes in the chain are deformed by the coupling to the surface waves in the InSb substrate by considering different carrier concentrations. By calculating the Zak phase we show that also in the presence of the substrate there is a topological phase transition and that topologically protected edge modes emerge for finite chains. Finally, we demonstrate the long-range heat transport along the chain due to the coupling to the surface waves of the sample {accompanied by a non-monotonic distance dependence of this effect and we show imprints of the trivial and non-trivial phase in the photonic local density of states.} We find an enhanced heat transfer in the topological non-trivial phase compared to the trivial phase due to the contribution of the edge modes.
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Statistical Mechanics · Cross-listed from physics.flu-dyn
Stretching and breaking of particles in compressible random flows
Dipankar Roy, Marco Martins Afonso, Jason R. Picardo et al. (+1 more)
A key feature of turbulent suspensions that involve floating particles on the surface or inertial particles in the bulk is the compressibility of the effective particle-phase velocity field. Little, however, is known about the effects of small-scale flow compressibility on the stretching and breaking of particles. Here, we gain insight into the nature of these effects by studying the deformation of tiny particles in model fluctuating flows. We consider a generic particle with extensional dynamics that are governed by a vector model, which accounts for elasticity, internal viscosity, and non-affine deformation. Applying the dynamical systems approach of Balkovsky, Fouxon & Lebedev (2000), we first obtain general results for the stationary statistics of particle extension in compressible chaotic flows. We then specialize to a time-decorrelated Gaussian random flow and derive an exact solution for the Batchelor regime of the compressible Kraichnan model. We also perform numerical simulations for a time-correlated renewing flow. While straining is suppressed on the average in compressible flows, our results show that large deviations of the strain rate strongly stretch particles and give rise to a power-law distribution of extensions. Extreme straining events are particularly important for stiff particles and, in the examples considered here, give rise to a counter-intuitive effect: stiff particles stretch more and break faster in flows of increasing compressibility. Highly-elastic particles, whose deformation is dictated by the mean straining, stretch less and break slower. Though based on specific random flows, our work shows how compressibility can affect the extensional dynamics of particles by altering the fluctuations of the strain rate, including its large deviations.
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All authors Dipankar Roy, Marco Martins Afonso, Jason R. Picardo, Dario Vincenzi
Strongly Correlated Electrons
Operator Lanczos Approach enabling Neural Quantum States as Real-Frequency Impurity Solvers
Jonas B. Rigo and Markus Schmitt
To understand the intricate exchange between electrons of different bands in strongly correlated materials, it is essential to treat multi-orbital models accurately. For this purpose, dynamical mean-field theory (DMFT) provides an established framework, whose scope crucially hinges on the availability of efficient
quantum impurity solvers. Here we present a real-frequency
impurity solver based on neural
quantum states (NQS) combined with an operator-Lanczos construction. NQS are an asymptotically unbiased variational ground-state ansatz that employs neural networks to capture long-range correlations on complicated graph structures. We leverage this ability to solve multi-orbital
impurity problems using a systematically improvable Segmented Commutator Operator-Lanczos (SCOL) construction. Our
benchmarks on both the single-orbital Anderson model and the multi-orbital Hubbard-Kanamori
impurity Hamiltonian reveal excellent ground-state precision and the capacity to accurately resolve zero temperature spectral functions and self-energies. These results open avenues for extending DMFT to more challenging problems.
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Materials Science
Nonequilibrium Photocarrier and Phonon Dynamics from First Principles: a Unified Treatment of Carrier-Carrier, Carrier-Phonon, and Phonon-Phonon Scattering
Stefano Mocatti, Giovanni Marini, Giulio Volpato et al. (+2 more)
We develop a first-principles many-body framework to describe the dynamics of photocarriers and
phonons in
semiconductors following ultrafast excitation. Our approach incorporates explicit ab initio light-matter coupling and first-principles collision integrals for carrier-carrier, carrier-
phonon, and
phonon-
phonon scattering. It also yields time-dependent quasiparticle and
phonon frequency renormalizations, along with light-induced coherent atomic motion. The equations of motion are solved in a maximally localized Wannier basis, ensuring gauge-consistent scattering integrals and ultradense momentum sampling, thereby enabling direct comparison with pump-probe experiments. The method can be coupled to constrained density-functional theory to access light-induced structural phase transitions at longer times after the light pulse. We showcase the capabilities and predictive power of this framework on MoS$_2$ and h-BN monolayers. For MoS$_2$, we resolve photoinduced renormalizations of electronic and
lattice properties, ultrafast carrier relaxation, hot-
phonon dynamics, and displacive coherent atomic motion. Including carrier-carrier scattering is crucial to obtain realistic photocarrier equilibration times, while omitting
phonon-
phonon scattering leads to incorrect long-time
lattice thermalization and a factor of two larger A$_{1g}$ coherent
phonon damping time. For h-BN, we quantify photoinduced changes in the electronic, optical, and
lattice responses in quasi-
equilibrium, demonstrating a fluence-dependent enhancement of screening and melting of excitonic features.
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All authors Stefano Mocatti, Giovanni Marini, Giulio Volpato, Pierluigi Cudazzo, Matteo Calandra
Mesoscale and Nanoscale Physics
Anisotropic transport in ballistic bilayer graphene cavities
Florian Schoeppl, Alina Mrenca-Kolasinska, Ming-Hao Liu et al. (+3 more)
Closing the gap between ray tracing simulations and experimentally observed electron jetting in
bilayer graphene (BLG), we study all-electronic, gate-defined BLG cavities using tight-binding simulations and semiclassical equations of motion. Such cavities offer a rich playground to investigate anisotropic electron transport due to the trigonally warped
Fermi surfaces. In this work, we achieve two things: First, we verify the existence of triangular modes (as predicted by classical ray tracing calculations) in the
quantum solutions of closed circular BLG cavities. Then, we explore signatures of said triangular modes in transport through open BLG cavities connected to leads. We show that the triangular
symmetry translates into anisotropic transport and present an optimal setup for experimental detection of the triangular modes as well as for controlled modulation of transport in preferred directions.
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All authors Florian Schoeppl, Alina Mrenca-Kolasinska, Ming-Hao Liu, Korbinian Schwarzmaier, Klaus Richter, Angelika Knothe
Materials Science
MBE obtained n-CdO:Eu p-Si heterojunctions – electron beam induced profiling, electrical and structural properties
E Przezdziecka, I Perlikowski, S Chusnutdinow et al. (+7 more)
The present investigation reports on the fabrication and characterization of heterojunctions based on in situ Eu doped CdO layers, which were deposited on p-type silicon using the
plasma assisted molecular beam epitaxy (PA MBE) method. The structural and optical properties of the cadmium
oxide (CdO) films were investigated using X ray diffraction and
Fourier transform infrared spectroscopy (FTIR). The CdO Eu films are polycrystalline. The electrical properties of the p n heterojunction composed of transparent n CdO Eu and p Si
semiconductors were investigated by current voltage and electron beam-induced current (EBIC) measurements. Current voltage measurements demonstrate good junction characteristics with a rectifying ratio of 20 . EBIC measurements allowed us to calculate the
diffusion length of minority carriers and the precise location of the depleted area at the CdO and Si interfaces.
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All authors E Przezdziecka, I Perlikowski, S Chusnutdinow, A Wierzbicka, A Adhikari, M Stachowicz, R Jakiela, E Zielony, P Wojnar, A Kozanecki
Superconductivity
Microwave Signature of the Emerging Abrikosov Lattice Above $H_{c2}$
Hang Zhou, Zhanghai Chen, A. A. Varlamov et al. (+2 more)
The emergence of the Abrikosov
lattice in the normal phase of type-II superconducting films when the
magnetic field approaches the critical field $H_{c2}$ from above was predicted in Ref.~\cite{GVV2011}. In the
quantum fluctuation regime \cite{GL2001} it is characterized by the formation of relatively large (with sizes of order $\xi_{\mathrm{QF}} \sim \xi_{\mathrm{BCS}}\sqrt{H_{c2}/(H-H_{c2})}$) “long lived” (lifetime of order $\tau_{\mathrm{QF}} \sim \hbar \Delta^{-1} H_{c2}/(H-H_{c2})$) clusters of rotating fluctuation Cooper pairs - signatures of developing Abrikosov
vortices. We demonstrate that these fluctuation-induced
vortex clusters, previously considered unobservable due to their ultrafast dynamics and weak (only logarithmically singular) contribution to the dc-conductivity, can in fact be detected through their distinct electromagnetic signature. By analyzing the high-frequency electromagnetic response of these rotating fluctuation Cooper pairs above the second critical field in superconducting film, we predict a pronounced and measurable enhancement in the imaginary part of the ac-conductivity arising directly from
quantum fluctuations. This enhancement is expected to occur at characteristic frequencies $\omega_{QF} \sim \hbar^{-1}\Delta(H-H_{c2})/H_{c2}$, which are well below the superconducting threshold at $2\hbar^{-1}\Delta $, where a similar increase in imaginary conductivity occurs in the superconducting phase. For niobium, a prototypical type II
superconductor, $\omega_{QF}$ lies in the experimentally accessible microwave range, making the effect directly testable with modern microwave spectroscopy.
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All authors Hang Zhou, Zhanghai Chen, A. A. Varlamov, Andreas Glatz, Yuriy Yerin
Statistical Mechanics
Supercritical-subcritical correspondence, asymmetric effects and antisymmetric corrections near a critical point
Xinyang Li and Yuliang Jin
The second-order phase transitions in the Ising model and
liquid-gas systems share a universality class and critical exponents, despite the absence of $Z_2$
symmetry in the
liquid-gas
Hamiltonian. This discrepancy highlights a central puzzle in critical phenomena: what is the influence of asymmetry on scaling laws? For over a century, this question has been explored through examining violations of the empirical “rectilinear diameter law” for the subcritical coexistence curve, where asymmetry could generate singular corrections. Here, we extend this investigation to the supercritical regime. We propose a supercritical-subcritical correspondence, drawing a formal analogy between the subcritical coexistence curve and recently defined supercritical boundary lines ($L^\pm$ lines). Our theory predicts that the linear mixing of physical fields - a hallmark of asymmetric systems - produces universal scaling corrections, with antisymmetric coefficients, in these supercritical loci. We verify these predictions using
liquid-gas data from the NIST database and a model
liquid-
liquid transition. Furthermore, we demonstrate that the same asymmetric scaling framework governs the behavior of higher-order cumulants in the order parameter distribution.
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Superconductivity
Effect of thermal fluctuations on topological crossover in the chiral d+id superconducting phase
A.G. Groshev and A.K. Arzhnikov
The effect of thermal fluctuations on the temperature dependence of the topological index C1 of the
chiral d+id superconducting phase of a two-dimensional single-band model on a triangular
lattice is investigated. Thermal fluctuations are taken into account within the framework of the self-consistent functional-integral theory. It is established that when the nodal points are located far inside (outside) the
Fermi contour of the normal phase, thermal fluctuations expand the relative temperature ranges in which the values of the topological index are close to integer values C1=4(-2). This expansion depends both on the value of the topological index and on the magnitude of the effective attraction between the electrons. However, as the nodal points approach the
Fermi contour, topological crossovers to new C1 values are observed, which can persist over a wide temperature range. The nature and degree of influence of thermal fluctuations on these crossovers are established. It is assumed that the observed effects may also manifest in the edge state behavior of a similar system with open boundaries.
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Superconductivity
Michał J. Winiarski, Dominik Walczak, Szymon Królak et al. (+3 more)
We report the synthesis and physical properties of a polycrystalline, hexagonal boride YRu$_3$B$_2$. Our resistivity and heat capacity measurements indicate that YRu$_3$B$_2$ is a weakly coupled
superconductor, with critical temperature $T_c$ = 0.63 K and upper critical field $\mu_0 H_{c2}$ (0)=0.11 T. Density functional theory calculations, together with chemical-bonding analysis, reveal that the electronic states at and near the
Fermi energy level are dominated by the Ru kagome sublattice.
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All authors Michał J. Winiarski, Dominik Walczak, Szymon Królak, Duygu Yazici, Robert J. Cava, Tomasz Klimczuk
Soft Condensed Matter · Cross-listed from physics.bio-ph
Data-Efficient Learning of Anomalous Diffusion with Wavelet Representations: Enabling Direct Learning from Experimental Trajectories
Gongyi Wang, Yu Zhang and Zihan Huang
Machine learning (ML) has become a versatile tool for analyzing anomalous
diffusion trajectories, yet most existing pipelines are trained on large collections of simulated data. In contrast, experimental trajectories, such as those from single-particle tracking (SPT), are typically scarce and may differ substantially from the idealized models used for simulation, leading to degradation or even breakdown of performance when ML methods are applied to real data. To address this mismatch, we introduce a wavelet-based representation of anomalous
diffusion that enables data-efficient learning directly from experimental recordings. This representation is constructed by applying six complementary wavelet families to each trajectory and combining the resulting wavelet modulus scalograms. We first evaluate the wavelet representation on simulated trajectories from the andi-
datasets benchmark, where it clearly outperforms both feature-based and trajectory-based methods with as few as 1000 training trajectories and still retains an advantage on large training sets. We then use this representation to learn directly from experimental SPT trajectories of fluorescent beads diffusing in F-actin networks, where the wavelet representation remains superior to existing alternatives for both
diffusion-exponent regression and mesh-size classification. In particular, when predicting the
diffusion exponents of experimental trajectories, a model trained on 1200 experimental tracks using the wavelet representation achieves significantly lower errors than state-of-the-art deep learning models trained purely on $10^6$ simulated trajectories. We associate this data efficiency with the emergence of distinct scale fingerprints disentangling underlying
diffusion mechanisms in the wavelet spectra.
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Mesoscale and Nanoscale Physics
Single-Particle X-ray Scattering Reveals a High Local Supersaturation of Precursors as the Origin of CoO Assembly Formation
Sani Y. Harouna-Mayer, Lars Klemeyer, Cecilia A. Zito et al. (+24 more)
Single-particle small-angle X-ray scattering (SP-SAXS) enables quantitative morphological analysis by recording diffraction snapshots from isolated particles using X-ray free-electron
laser (XFEL) pulses. Unlike conventional X-ray techniques, which average over the entire illuminated sample volume, SP-SAXS resolves low-contrast, less abundant, or transient species within heterogeneous particle populations that would otherwise remain hidden. Here, we apply SP-SAXS to investigate the solvothermal formation of CoO nanocrystal assemblies from a Co(acac)$_3$ precursor in benzyl alcohol. The single-particle data reveal amorphous, uniform-density Co(acac)$_2$ spheres as transient intermediates that directly crystallize into cavernous CoO nanocrystal assemblies, which explains why CoO forms as hierarchical aggregates rather than as isolated nanocrystals. These results demonstrate that SP-SAXS provides a powerful framework for disentangling morphological heterogeneity in nanoparticle formation processes.
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All authors Sani Y. Harouna-Mayer, Lars Klemeyer, Cecilia A. Zito, Johan Bielecki, Xuemei Cheng, Davide Derelli, Armando D. Estillore, Tjark L.R. Groene, Lukas V. Haas, Romain Letrun, Chan Kim, Jayanath C.P. Koliyadu, Abhishek Mall, Parichita Mazumder, Diogo V.M. Melo, Adam R. Round, Amit K. Samanta, Abhisakh Sarma, Zhou Shen, Xiao Sun, Patrik Vagovic, Tamme Wollweber, Richard Bean, Jochen Küpper, Henry N. Chapman, Dorota Koziej, Kartik Ayyer
Materials Science
Exogenous Metal Cations in the Synthesis of CsPbBr3 Nanocrystals and their Interplay with Tertiary Amines
Zhanzhao Li, Luca Goldoni, Ye Wu et al. (+9 more)
Current syntheses of CsPbBr3 halide perovskite nanocrystals (NCs) rely on over-stoichiometric amounts of Pb2+ precursors, resulting in unreacted lead ions at the end of the process. In our synthesis scheme of CsPbBr3 NCs we replaced excess Pb2+ with different exogenous metal cations (M) and investigated their effect on the synthesis products. These cations can be divided into two groups: group 1 delivers monodisperse CsPbBr3 cubes capped with oleate species (as for the case when Pb2+ is used in excess) and with photoluminescence
quantum yield (PLQY) as high as 90% with some cations (for example with M= In3+); group 2 yields irregularly shaped CsPbBr3 NCs with broad size distributions. In both cases, the addition of a tertiary ammonium cation (didodecylmethyl ammonium, DDMA+) during the synthesis, after the nucleation of the NCs, reshapes the NCs to monodisperse truncated cubes. Such NCs feature a mixed oleate/DDMA+ surface termination with PLQY values up to 90%. For group 1 cations, this happens only if the ammonium cation is directly added as a salt (DDMA-Br) while for group 2 cations this happens even if the corresponding tertiary amine (DDMA) is added, instead of DDMA-Br. This is attributed to the fact that only group 2 cations can facilitate the protonation of DDMA by the excess oleic acid present in the reaction environment. In all cases studied, the incorporation of M cations is marginal and the reshaping of the NCs is only transient: if the reactions are run for a long time the truncated cubes evolve to cubes.
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All authors Zhanzhao Li, Luca Goldoni, Ye Wu, Muhammad Imran, Yurii P. Ivanov, Giorgio Divitini, Juliette Zito, Iyyappa Rajan Panneerselvam, Dmitry Baranov, Ivan Infante, Luca De Trizio, Liberato Manna
Materials Science
Core@Shell AgBr@CsPbBr3 Nanocrystals as Precursors to Hollow Lead Halide Perovskite Nanocubes
Zhanzhao Li, Yurii P. Ivanov, Anna Cabona et al. (+7 more)
We report the synthesis of colloidal core@shell AgBr@CsPbBr3 nanocubes by a one-pot approach, where the nucleation and growth of AgBr nanocrystals occurs rapidly after the injection of chemical precursors. This is immediately followed by the overgrowth of CsPbBr3, delivering AgBr@CsPbBr3 nanocubes of several tens of nanometers in size, with the volume of the AgBr core being only a small fraction of the overall nanocrystal volume. The formation of a core@shell geometry is facilitated by the epitaxial compatibility between AgBr and CsPbBr3 along multiple crystallographic directions. Exchange with Cl-ions leads to Ag@CsPbCl3 nanocubes, whereas exchange with I-ions leads to hollow CsPbI3 nanocubes, due to selective etching of the AgBr (or Ag) core region by the I-ions diffusing in the nanocubes. These hollow CsPbI3 nanocubes can then be converted into hollow CsPbBr3 and CsPbCl3 nanocubes by halide exchange. The optical emission properties of the hollow CsPbX3 (X=Cl, Br, I) nanocubes are in line with those expected from large, non-hollow halide perovskite nanocrystals, indicating that the small hollow region in the cubes has no major influence on their optical properties.
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All authors Zhanzhao Li, Yurii P. Ivanov, Anna Cabona, Andrea Fratelli, Stefano Toso, Saptarshi Chakraborty, Giorgio Divitini, Ilka Kriegel, Sergio Brovelli, Liberato Manna
Materials Science
Benchmarking First-Principles Approaches for Extracting Magnetic Exchange Interactions
Nafise Rezaei, Artem R. Oganov, Ali Ghojavand et al. (+2 more)
Magnetic exchange interactions govern the macroscopic
magnetic behavior of solids and underpin both fundamental
spin phenomena and emerging technologies. The accurate and efficient determination of these interactions is therefore critical for predictive modeling of
magnetic materials. Here we present a systematic first-principles comparison of three widely used approaches-the Least-Squares Total Energy (LSTE), the Four-State Total Energy (FSTE), and the Green's function-based Liechtenstein et al. (LKAG) methods-applied to thirteen
antiferromagnetic compounds. We introduce an framework for identifying the minimal supercells required for an accurate exchange parameter extraction in the FSTE method, significantly reducing computational cost while preserving precision. Our results show that LSTE and FSTE yield nearly identical exchange parameters, whereas the LKAG method reproduces the dominant exchange interactions but exhibits quantitative deviations. A detailed analysis of computational efficiency versus accuracy reveals that the LSTE scheme offers the most favorable balance, establishing a general, reproducible, and scalable workflow for Heisenberg mapping, while the FSTE approach remains the most straightforward for extracting specific exchange interactions.
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All authors Nafise Rezaei, Artem R. Oganov, Ali Ghojavand, Milorad V. Milošević, Mojtaba Alaei
Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Higher Josephson harmonics in a tunable double-junction transmon qubit
Ksenia Shagalov, David Feldstein-Bofill, Leo Uhre Jakobsen et al. (+11 more)
Tunable Josephson harmonics open new avenues for
qubit design. We demonstrate a superconducting
circuit element consisting of a tunnel junction in series with a SQUID loop, yielding a Josephson potential whose harmonic content is strongly tunable by
magnetic flux. Through spectroscopy of the first four
qubit transitions, together with an effective single-mode model renormalized by the internal mode, we resolve a second harmonic with an amplitude up to $\sim10\%$ of the fundamental. We identify a flux sweet spot where the dispersive shift vanishes, achieved by balancing the dispersive couplings to the internal and
qubit modes. This highly tunable element provides a route toward protected
qubits and customizable nonlinear microwave devices.
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All authors Ksenia Shagalov, David Feldstein-Bofill, Leo Uhre Jakobsen, Zhenhai Sun, Casper Wied, Amalie T. J. Paulsen, Johann Bock Severin, Malthe A. Marciniak, Clinton A. Potts, Anders Kringhøj, Jacob Hastrup, Karsten Flensberg, Svend Krøjer, Morten Kjaergaard
Materials Science
Synthesis, Growth Mechanism, and Photocatalytic Properties of Metallic-Bi/Bi13S18Br2 Nano-Bell Heterostructures
Anna Cabona, Stefano Toso, Andrea Griesi et al. (+8 more)
We report the synthesis of bell-shaped Bi/Bi13S18Br2 metal/
semiconductor heterostructures as a photocatalyst based on non-toxic and Earth-abundant elements. Their unique morphology arises from a multi-step growth process, involving 1) the nucleation of Bi13S18Br2 nanorods, 2) the reduction of a metallic-Bi domain on their surface induced by N,N-didodecylmethylamine, and 3) the
heterostructure accretion by a localized reaction at the Bi/Bi13S18Br2 interface promoted by Ostwald ripening. These
heterostructures display remarkable stability in polar solvents, remaining almost unaffected by prolonged exposure to isopropanol and water, and exhibit high photocatalytic efficiency for the degradation of organic dyes (i.e., Rhodamine-B and Methylene Blue) under visible-light irradiation, with good recyclability. Additionally, preliminary tests demonstrate CO2 reduction capabilities, which make them promising for both the photocatalytic degradation of pollutants and photo-electro CO2 conversion. The straightforward synthesis process and the use of non-toxic and earth-abundant elements offers significant potential for sustainable energy conversion technologies.
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All authors Anna Cabona, Stefano Toso, Andrea Griesi, Martina Rizzo, Michele Ferri, Pascal Rusch, Giorgio Divitini, Julia Perez-Prieto, Raquel E. Galian, Ilka Kriegel, Liberato Manna
Materials Science
Modeling the Effects of Slip, Twinning, and Notch on the Deformation of Single-Crystal Austenitic Manganese Steel
Saketh Virupakshi, Xinzhu Zheng, Karol Frydrych et al. (+3 more)
The objective of this work is to deconvolute the interaction of slip, twinning, and notch on the deformation response of an austenitic manganese (Hadfield) steel using detailed finite element simulations. The simulations employ a rate-dependent
crystal plasticity constitutive model that incorporates both slip and twinning deformation mechanisms. The model accounts for the spatially non-uniform appearance of new twin-related orientations, hardening due to slip–twin interactions, and modified properties of the twinned
crystal. Limited experiments on single-
crystal dog-bone and single-edge notch specimens, with two
crystal orientations, are also conducted to aid the simulation. Several features of the experimental observations are accurately captured in the simulations. For example, simulations accurately capture distinct stress–strain responses associated with different crystallographic orientations, including variations in initial hardening behavior followed by either decreasing or increasing hardening depending on the dominant deformation mechanisms. The simulation also captures the observed orientation-dependent asymmetric deformation of the notch in single-edge notch specimens. Additionally, by selectively activating deformation mechanisms, the role of twinning is isolated and its influence on both global and local response is clearly demonstrated. These results provide a mechanistic understanding of how deformation mode interactions and local geometry (i.e., notch) influence the response of these materials.
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All authors Saketh Virupakshi, Xinzhu Zheng, Karol Frydrych, Ibrahim Karaman, Ankit Srivastava, Katarzyna Kowalczyk-Gajewska
Soft Condensed Matter · Cross-listed from physics.flu-dyn
Transition in elastic Dean flow: the centre-mode versus hoop-stress pathways
P. S. D. Surya Phani Tej, Ganesh Subramanian and V. Shankar
We analyse the stability of viscoelastic Dean flow (flow of an elastic fluid through a curved two-dimensional channel, driven by an azimuthal pressure gradient) in the absence of fluid inertia. This configuration is well known to exhibit a hoop-stress-driven `purely elastic' instability (referred to henceforth as the hoop-stress mode – `HSM') on account of the base-flow streamline
curvature. The objective of this study is to demonstrate the existence and importance of a distinct elastic instability in this flow configuration, which is not driven by hoop-stresses, but instead is a continuation of a novel `centre-mode' (CM) instability recently identified in rectilinear shear flows. We use both the Oldroyd-B and FENE-P models to map out parameter regimes in the $W\!i$–$\epsilon$–$\beta$ space where the aforementioned instabilities are present. Here, $W\!i$ is a suitably defined Weissenberg number that characterizes fluid elasticity, $\beta$ is the ratio of solvent to total solution viscosity, and $\epsilon$ is the ratio of the gap (channel) width to the radius of
curvature. For FENE-P model, decreasing the finite extensibility parameter $L$ has opposing effects on the HSM and CM instabilities – stabilising the former, but destabilising the latter. In the dilute solution regime ($\beta > 0.95$), and for realistic values of $L \sim O(100)$, corresponding to
polymer molecular weights of $O(10^{5-6})$g/mol, the CM remains the most unstable mode for $\epsilon \leq 0.25$, rendering it potentially relevant to the onset of elastic
turbulence in the flow of such
polymer solutions through curved channels.
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Materials Science
The unexpected dewetting during growth of silicene flakes with dendritic pyramids
Kejian Wang, Mathieu Abel, Filippo Fabbri et al. (+6 more)
Silicene growth on
graphene has emerged as a novel method for fabricating silicon-based van der Waals
heterostructures. However, the silicene flakes produced in this manner are the result of an exotic growth mode characterized by metastable nanostructures with varying degrees of deviation from
equilibrium, with large two-dimensional flakes surrounded by a rim that coexist with small 3D islands, and, at large deposits, thick dendritic pyramids separated by a denuded zone. In order to rationalize and control this growth, a model is derived that revisits the dewetting thermodynamics and considers generally ignored adsorption and step-edge energies. The model is investigated using kinetic Monte-Carlo simulations and mean-field rate equations, and implemented by close inspection of microscopy images. This model perfectly reproduces the experimental outcomes, unveiling an anomalous growth mode, and provides guidelines on experimental conditions for high-quality silicene growth.
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All authors Kejian Wang, Mathieu Abel, Filippo Fabbri, Mathieu Koudia, Adrien Michon, Adam Hassan Denawi, Holger Vach, Isabelle Berbezier, Jean-Noël Aqua
Strongly Correlated Electrons
Decay of spin helices in XXZ quantum spin chains with single-ion anisotropy
Florian Lange, Frank Göhmann, Gerhard Wellein et al. (+1 more)
Long-lived
spin-helix states facilitate the study of non-
equilibrium dynamics in
quantum magnets. We consider the decay of transverse
spin-helices in
antiferromagnetic spin-$S$ XXZ chains with single-ion anisostropy. The
spin-helix decay is observable in the time
evolution of the local magnetization that we calculate numerically for the system in the thermodynamic limit using infinite time-evolving block decimation simulations. Although the single-ion anisotropy prevents helix states from being eigenstates of the
Hamiltonian, they still can be long-lived for appropriately chosen wave numbers. In case of an easy-axis exchange anisotropy the single-ion anisotropy may even stabilize the helices. Within a
spin-wave approximation, we obtain a condition giving an estimate for the most stable wave number $Q$ that agrees qualitatively with our numerical results.
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All authors Florian Lange, Frank Göhmann, Gerhard Wellein, Holger Fehske
Soft Condensed Matter
Many interacting particles in solution. I. Screening-ranged expansions of electrostatic potential and energy
Sergii V. Siryk and Walter Rocchia
We present an analytical many-body formalism for systems of spherical particles carrying arbitrary free charge distributions and interacting in a polarizable electrolyte solution, that we model within the linearized Poisson–Boltzmann framework. Building on the detailed spectral analysis of the associated nonstandard Neumann–Poincaré-type operators developed in our companion study arXiv:2512.08684, we construct exact explicit expansions of the electrostatic potential and energy in ascending orders of Debye screening thereby obtaining systematic "screening-ranged" series for potentials and energies. These screening-ranged expansions provide a unified and tractable description of many-body electrostatics. We demonstrate the versatility of the approach by showing how it generalizes and improves upon both classical and modern methods, enabling rigorous treatment of heterogeneously charged systems (such as Janus particles) and accurate modeling of higher-order phenomena (such as asymmetric dielectric screening, opposite-charge repulsion, like-charge attraction) as well as yielding many-body generalizations to analytical explicit results previously known only in the two-body setting.
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