Materials Science
Theory-Guided Discovery of Pressure-Induced Transitions in Fast-Ion Conductor BaSnF4
Robin Turnbull, Zhang YingLong, Claudio Cazorla et al. (+6 more)
Fast-ion conductors such as BaSnF4 are of significant interest for next-generation solid-state battery technologies due to their high ionic conductivity and chemical stability. However, the behaviour of these materials under extreme conditions remains poorly understood, despite the relevance of pressure-induced modifications for tuning functional properties. In this study, we combine density functional theory (DFT) calculations with high-pressure experiments to investigate the structural
evolution of BaSnF4 up to 40 GPa. DFT predicts two pressure-induced phase transitions: from the ambient-pressure tetragonal P4/nmm phase to a monoclinic P21/m-I structure at 10 GPa, and subsequently to a denser monoclinic P21/m-II phase at 32 GPa. The first transition is experimentally confirmed via angle-dispersive X-ray diffraction, Raman spectroscopy, and electrical resistivity measurements, all performed at ambient temperature. The second transition is supported by distinct changes in high-pressure Raman modes and resistivity behaviour, consistent with a further structural reorganization. These findings not only clarify the high-pressure phase diagram of BaSnF4, but also shed light on the potential for pressure-tuned ionic transport in fluorostannate-based solid electrolytes.
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All authors Robin Turnbull, Zhang YingLong, Claudio Cazorla, Akun Liang, Rahman Saqib, Miriam Pena-Alvarez, Catalin Popescu, Laura Pampillo, Daniel Errandonea
Statistical Mechanics · Cross-listed from astro-ph.HE
Reginald Christian Bernardo
Langevin
stochastic differential equations provide a dynamical description of
pulsar timing noise and gravitational wave background (GWB) signals. They are also central to state space
algorithms that have gained traction in
pulsar timing array analysis due to their linear computational scaling with the number of observations. In this work, we utilize established methods in
diffusion theory to derive analytical time-domain solutions (means, covariances, and probability density functions) to Langevin equations relevant to red noise and the GWB signal in
pulsars. The solutions give direct physical insight on the dynamics of
pulsar timing signals. As a canonical example, we show that the
pulsar spin frequency modeled as an Ornstein-Uhlenbeck process is mathematically inconsistent with a stationary GWB signal when the timing residual is the direct observable. The nonstationarity can be partially dealt with by marginalizing over long time deterministic trends in the data. Then, we show that a random process based on an overdamped harmonic oscillator supports both a stationary
spin frequency and phase residuals, consistent with a stationary GWB signal. We also turn our
attention to a phenomenological model of a
neutron star – a two-component model with
spin wandering – that has been motivated to explain observed timing noise in
radio pulsars. We derive analytical expressions for the means, covariances, and cross-covariances of the crust and superfluid rotational states driven by white noise. The associated constant deterministic torques are linked to the quadratic
spin-down of
pulsars. The solutions reveal the physical origin of nonstationarity in the residual model: the coexistence of damped and diffusive eigenmodes of the system.
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Materials Science
Comparative high-pressure study on rare-earth entropy fluorite-type oxides
Pablo Botellaa, David Vie, Leda Kolarek et al. (+6 more)
We report a comparative high-pressure study of two fluorite-type rare-earth
oxides with increasing configurational
entropy, (CePr)O$_{2-{\delta}}$ and (CePrLa)O$_{2-{\delta}}$. Synchrotron-based powder X-ray diffraction and Raman spectroscopy were carried out up to 30 GPa and 20 GPa, respectively. Both compounds retain the cubic fluorite structure throughout the pressure range explored, although an anomaly is observed between 9-16 GPa, characterized by a compressibility plateau and changes in vibrational modes. This behavior is attributed to local
lattice distortions and a progressive bond angle bending rather than abrupt phase transitions. In (CePrLa)O$_{2-{\delta}}$, the onset of amorphization is observed above 22 GPa, highlighting its reduced structural stability. The bulk modulus of both systems shows a slight decrease after the onset of the anomaly, suggesting subtle
lattice softening. Raman spectroscopy reveals suppression of the F$_{2g}$ mode intensity with increasing cationic disorder, and under compression, partial reordering is evidenced by an increase in the RE-O mode intensity. Our results highlight the complex interplay between configurational
entropy, cation size, and pressure in determining the structural stability and vibrational properties of rare-earth high-
entropy oxides and provide insight into the mechanisms governing their resilience and local disorder under extreme conditions.
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All authors Pablo Botellaa, David Vie, Leda Kolarek, Neha Bura, Peijie Zhang, Anna Herlihy, Dominik Daisenberger, Catalin Popescu, Daniel Errandonea
Soft Condensed Matter
Axial forces in capillary liquid bridges of polymer solutions
Sreeram Rajesh, Riley S. Tinianov, Jooyeon Park et al. (+1 more)
Liquid bridges form between particles during wet mixing with binders or by condensation due to ambient humidity. The consequences of capillary bridges can be quite drastic, creating macroscopic cohesion, as seen in sandcastles and in the formation of particulate agglomerates. Bulk effects in cohesive particles arise from forces generated by capillary bridges, so particle-scale measurements are needed to develop predictive models. Most existing studies at the particle scale assume Newtonian
liquids. Yet many binders in industry and in the environment can exhibit viscoelastic behavior. In this study, we measure the axial force generated by
liquid bridges of viscoelastic
polymer solutions between two spherical beads during controlled uniaxial separation. We vary the
polymer concentration, separation velocity, and particle size, and track the force as the bridge thins and ruptures. At quasi-static rates, the axial force remains dominated by capillarity and is not significantly affected by
polymer rheology. However, increasing the stretching rate increases the peak force through viscous dissipation and promotes the formation of a viscoelastic filament, thereby delaying rupture. The peak axial forces collapse when rescaled by a capillary number and particle size, while the effective rupture distance collapses with a Weissenberg number. These results provide a simple first-order particle-scale force law for polymeric binders.
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All authors Sreeram Rajesh, Riley S. Tinianov, Jooyeon Park, Alban Sauret
Materials Science
2D Ferroelectric Ruddlesden-Popper Perovskites: an Emerging Fully Electronically Controllable Shift Current and Persistent Spin Helix
Yue Zhao, Fu Li, Vikrant Chaudhary et al. (+5 more)
Two-dimensional (2D) hybrid organic–inorganic perovskites (HOIPs) are promising candidates for next-generation optoelectronic and spintronic applications. This work systematically investigates the relationship between structural distortions and functional responses in three $C_{2v}$-symmetric Ruddlesden–Popper (RP) ferroelectric perovskites, $(4,4\text{-DFPD})_{2}\mathrm{PbI}_{4}$, $(\mathrm{DFCHA})_{2}\mathrm{PbI}_{4}$, and PEPI, using first-principles calculations combined with irreducible representation decomposition and wave-vector point-group
symmetry (WPGS) analysis. The results reveal that the lead–iodide framework yields shift-current (SC) magnitudes comparable to, and in specific cases even an order of magnitude larger than, those of traditional ferroelectric
oxides, with PEPI reaching a maximum of $69.16\ \mu\mathrm{A}/\mathrm{V}^{2}$. The SC magnitude correlates positively with the octahedral distortion index ($D_i$), while a competition mechanism is identified between covalent bond strength and structural asymmetry, where increased average bond lengths can offset the enhancement induced by $D_i$. Regarding spintronics, $C_{2v}$
symmetry-protected persistent
spin textures (PST) are identified. A transition to $C_2$-protected quasi-PST occurs in monoclinic $(4,4\text{-DFHHA})_{2}\mathrm{PbI}_{4}$, leading to a persistent
spin helix (PSH) with long-distance
spin transport. The synergy among ferroelectricity, SC, and PST enables nonvolatile electrical control of both photocurrent direction and
spin configurations. This work provides evaluation criteria and practical guidance for designing high-performance integrated spintronic–photovoltaic devices.
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All authors Yue Zhao, Fu Li, Vikrant Chaudhary, Hongbin Zhang, Gaoyang Gou, Niuzhuang Yang, Yue Hao, Wenyi Liu
Materials Science · Cross-listed from physics.chem-ph
From Full Dynamic to Pure Static: A Family of $GW$-Based Approximations
Pierre-François Loos and Johannes Tölle
We introduce a systematic hierarchy of one-body Green's function methods derived from the $GW$ approximation, constructed by progressively reducing the dynamical content of the self-energy. Starting from the fully dynamical Dyson formulation, we generate a family of approximations that interpolates between the standard $GW$ approximation to purely static effective single-particle
Hamiltonians. This framework enables a controlled investigation of the role of dynamical effects and particle-hole coupling in the description of ionization potentials. Within this unified formalism, the hole and particle branches can be selectively decoupled through downfolding strategies into reduced one-particle spaces. By benchmarking the different members of this hierarchy on molecular ionization energies, we assess their accuracy, numerical robustness, and algorithmic complexity. We demonstrate that consistently derived partially static schemes can yield reliable quasiparticle energies while significantly simplifying the underlying
eigenvalue problem. We further introduce a novel static Hermitian self-energy obtained as the static limit of this hierarchy. Despite its conceptually distinct origin, it produces results remarkably close to those of qs$GW$, thereby providing an alternative static route toward partial self-consistency.
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Statistical Mechanics
Controlling the rain fall statistics using Mean-Reverting Jump Diffusion model
Joya GhoshDastider, D. Pal and Pankaj Kumar Mishra
We present a
stochastic mean-reverting jump-
diffusion model to simulate rainfall time series and validate it using long-term half-hourly rain fall data from the North-East region of India. The model captures the intermittent and extreme-event dynamics of rainfall, reproducing superdiffusive behavior with an exponent $\sim 1.8$, along with the observed probability distributions and multifractal features. By systematically varying key parameters, we demonstrate a transition between Log-Normal and Gamma distributions, and show how the occurrence of extreme events and dry-patch durations can be controlled. Spectral and wavelet analyses further confirm that the simulated series reproduces the dominant temporal scales observed in real rainfall data. Our proposed framework provides a robust tool for generating realistic synthetic rainfall series and serves as an effective approach for understanding the influence of underlying
stochastic processes that governs the rainfall statistics.
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Soft Condensed Matter
Exact Generalized Langevin Dynamics of Pair Coordinates in Elastic Networks
Shunsuke Ando, Tomoya Urashita, Soya Shinkai et al. (+1 more)
Generalized Langevin equations (GLEs) provide a powerful framework for describing slow dynamics in soft-matter systems, but deriving an exact GLE for a reaction coordinate from an underlying many-body system remains generally difficult. Here, we analytically derive an exact coupled GLE for the overdamped dynamics of two tagged beads in arbitrary harmonic elastic networks. We further derive an exact GLE for their relative coordinate. The
memory kernel and effective restoring force are expressed explicitly in terms of the network
matrices, thereby providing a systematic reduction of the high-dimensional network dynamics to a pair coordinate. Within the small-displacement approximation, we further derive a GLE for the inter-bead distance, a central observable in distance-sensitive single-molecule experiments. These results therefore have broad potential applications in modeling
proteins and other soft-matter systems.
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All authors Shunsuke Ando, Tomoya Urashita, Soya Shinkai, Tomoshige Miyaguchi
Strongly Correlated Electrons
Orbital-Selective $d$-wave Superconductivity in the Two-Band $t$-$J$ Model: Possible Applications to La$_3$Ni$_2$O$_7$
Zhan Wang, Kun Jiang, Fu-Chun Zhang et al. (+1 more)
We investigate superconductivity in a two-band $t$-$J$ model consisting of an itinerant orbital (orbital-0) and a quasi-localized orbital (orbital-1) using variational Monte Carlo. A robust orbital-selective $d$-wave superconducting state is found to emerge exclusively from the itinerant orbital. An analysis of the superexchange energy hierarchy shows that the quasi-localized orbital-1 competes with superconductivity by favoring local inter-orbital bound states, which act as energy defects and disrupt phase coherence. Consistently, the superconducting order parameter is monotonically suppressed as the occupancy of orbital-1 increases. Motivated by superconductivity in nickelate La$_3$Ni$_2$O$_7$, these results highlight the essential role of multi-orbital physics beyond the single-band $t$-$J$ framework and point to a concrete route to enhance $T_c$: suppressing the involvement of localized $d_{z^2}$-derived orbitals.
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All authors Zhan Wang, Kun Jiang, Fu-Chun Zhang, Hui-Ke Jin
Soft Condensed Matter · Cross-listed from physics.bio-ph
Active Transport as a Mechanism of Microphase Selection in Biomolecular Condensates
Le Qiao, Peter Gispert, Lukas S. Stelzl et al. (+1 more)
The size and organization of biomolecular condensates formed by
liquid-
liquid phase separation (LLPS) are set by multiple cellular mechanisms that are not yet fully understood. Here we identify a transport-driven mechanism:
stochastic binding of phase-separating
proteins to cytoskeletal motor
proteins, followed by active redistribution along filament networks, generates an effective long-range repulsion that arrests coarsening and selects a finite condensate size. A minimal
diffusion-transport model, analyzed by linear stability theory and three-dimensional simulations, reveals a transition from macroscopic to microphase separation at remarkably low binding/release fractions, corresponding to minute motor-bound populations. Tuning motor binding rates $b$ or transport velocities enables sublinear control of condensate sizes ($L \sim b^{-1/4}$) from a few hundred nanometres up to the micron scale. The selected length scale is robust to the intrinsic shot noise of the binding–release reactions. In anisotropic cytoskeletal environments, transport asymmetry drives morphological transitions from spherical to cylindrical condensates, independently of the thermodynamic parameters. This mechanism provides a versatile, spatiotemporally programmable route to condensate organization and informs the design of synthetic active emulsions with tunable architectures.
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All authors Le Qiao, Peter Gispert, Lukas S. Stelzl, Friederike Schmid
Mesoscale and Nanoscale Physics
Modern Approach to Orbital Hall Effect Based on Wannier Picture of Solids
Mirco Sastges, Insu Baek, Hojun Lee et al. (+3 more)
The orbital
Hall effect (OHE) and its key figure of merit, the orbital
Hall conductivity (OHC), are central to the emerging field of orbitronics. The OHC is conventionally computed via Kubo linear response theory, where the orbital angular momentum (OAM) operator is approximated through atom-centered projections that retain only local contributions, discarding physically important itinerant components. Here, we present a rigorous framework for the OAM operator grounded in the modern theory of orbital magnetization, formulated in a Wannier function basis. Critically, this naturally introduces a hierarchy of non-local contributions to the OAM operator. In turn, this gives rise to an additional non-Kubo contribution to the OHC of purely
geometric origin, absent in all atom-centered treatments. First-principles calculations across a diverse set of materials demonstrate that this term can constitute a significant fraction of the total OHC, with its omission leading to qualitatively incorrect predictions. Our framework provides a unified and numerically tractable approach to orbital transport and improves our understanding of the OAM in solids, allowing for a more precise estimation of various orbital effects in complex materials.
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All authors Mirco Sastges, Insu Baek, Hojun Lee, Hyun-Woo Lee, Yuriy Mokrousov, Dongwook Go
Materials Science
Rapid and Highly Efficient Synergistic Sonophotocatalytic Degradation of Methyl Orange with CuDoped LaFeO3 Perovskite Nanoparticles
Salma Elmouloua, M barek Amjoud, Daoud Mezzane et al. (+6 more)
The integration of sonocatalysis with photocatalysis offers a powerful strategy for advanced wastewater treatment by overcoming rapid charge carrier recombination in conventional photocatalytic systems. Although these processes are often treated separately due to their distinct mechanisms, their combination creates a highly efficient synergistic system. In this study, we investigate the sonophotocatalytic degradation of methyl orange (MO) using Cu-doped LaFeO3 perovskite nanoparticles. The Cu doped catalyst demonstrated excellent performance, achieving a degradation rate of 0.0455 min-1 and complete removal of MO within 120 minutes under combined ultrasonic and light irradiation. A strong synergistic effect was observed, with a synergy index of approximately 10, highlighting the enhanced interaction between sonocatalysis and photocatalysis. The catalyst also exhibited good stability and reusability, maintaining high efficiency over four consecutive cycles. Mechanistic studies using scavenger experiments revealed that hydroxyl radicals and photogenerated holes are the main reactive species responsible for degradation. A plausible reaction pathway is proposed based on these findings. Overall, Cu doped LaFeO3 shows superior sonophotocatalytic activity compared to the undoped material, demonstrating the potential of synergistic sonophotocatalytic processes for efficient pollutant removal.
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All authors Salma Elmouloua, M barek Amjoud, Daoud Mezzane, Manal Benyoussef, Jaafar Ghanbaja, Mohamed Goune, Mohamed Lahcini, Zdravko Kutnjak, Mimoun El Marssi
Materials Science · Cross-listed from physics.optics
Experimental Evidence of Thermal Capillary Waves Excitation on a Microsphere Surface
Abhishek Sureshkumar, Georges Perin, Julien Lapeyre et al. (+7 more)
Whispering-gallery-mode (WGM) microsphere resonators have emerged as a versatile platform across various photonic applications. Despite significant progress, their performance at short wavelengths is fundamentally limited by scattering-induced optical losses that restrict achievable quality factors (Q-factor). Although surface roughness has long been recognised as the leading cause of these losses, its physical origin has remained unclear, with current understanding attributing it to unavoidable fabrication imperfections. Here, we show that thermally excited capillary waves are the fundamental source of scattering losses in microsphere cavities. Using high-resolution atomic force microscopy (AFM) combined with rigorous statistical analysis, we quantitatively identify the characteristic signatures of frozen capillary fluctuations at the sub-nanometre level. The experimentally extracted roughness parameters show close agreement with theoretical predictions based on capillary wave theory. These findings fundamentally revise the prevailing interpretation of surface scattering losses and establish thermodynamic fluctuations, rather than fabrication defects, as the limiting roughness mechanism. By identifying frozen capillary waves as the limiting factor, this work opens new pathways for engineering ultra-high-Q microsphere resonators through fabrication management strategies, particularly for visible- and ultraviolet-photonic applications where scattering losses are most severe.
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All authors Abhishek Sureshkumar, Georges Perin, Julien Lapeyre, Rozenn Bernard, Kelig Terrien, Bertrand Dudoux, Adil Haboucha, Hélène Ollivier, Yannick Dumeige, Stéphane Trebaol
Soft Condensed Matter
3D microprinting anisotropic and deformable active matter – A perspective
Mengshi Wei and Daniela J. Kraft
Active colloidal particles provide versatile model systems for exploring non-
equilibrium physics in motile matter. To date, most experimental realizations have focused on spherical particles, largely due to fabrication constraints. However, theoretical and computational studies have long predicted that particle anisotropy and flexibility can dramatically enrich single-particle dynamics, interparticle interactions, and emergent collective behavior. Here, we highlight recent advances in the fabrication of anisotropic active particles and architectures enabled by the unprecedented design freedom of 3D microprinting. We discuss how additive manufacturing is expanding the accessible parameter space of active soft matter, allowing precise control over shape, location of active forces, and functionality at the microscale. These developments establish new model platforms for uncovering fundamental principles of active and soft matter, and simultaneously pave the way toward microrobotic systems with programmable dynamics and emergent functionalities.
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Superconductivity
Topological multicomponent superconductivity with sizable $s$-wave admixture in twisted bilayer cuprates
Yu-Hang Li, Congjun Wu and Wang Yang
We investigate multicomponent superconductivity in twisted
bilayer cuprates with order parameter $s+d_1 e^{i\phi_1}+d_2 e^{i\phi_2}$, where $s=s_1+s_2$ is the layer-symmetric $s$-wave pairing and $d_i$ is the $d$-wave pairing in layer $i$. When $\phi_1-\phi_2\neq 0,\pi$, this three-component state spontaneously breaks time-reversal and $C_4$ rotational
symmetries and can realize a topologically nontrivial phase. Ginzburg-Landau analysis and self-consistent mean-field calculations show that this state is stabilized over a broad parameter regime. We further identify nematic Kerr anisotropy as a key signature distinguishing it from $s+id$ and $d_1+e^{i\phi}d_2$, and find that its Josephson critical current remains sizable near the $45^{\circ}$ twist. Our results show that $s$-wave pairing does not preclude
chiral topological superconductivity, pointing to twisted cuprates as a more robust platform than previously appreciated.
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Materials Science
Odd-parity Magnetism from the Generalized Bloch Theorem
Mikkel Christian Larsen and Thomas Olsen
In the non-relativistic limit, helimagnetic order is always associated with odd-parity magnetism. That is, for single-particle states the expectation value of the electronic
spin is odd in
crystal momentum, which implies direct control of the
spin by means of electric fields. However, the theoretical description of helimagnets is hindered by the fact that the spiral pitch may require large super
cells or even be incommensurate with the
lattice. In the this letter we show that such issues may be remedied by use of the Generalized Bloch
theorem. It allows one to describe (by models or first principles) the system in terms of the primitive unit
cell, from which all relevant properties can be obtained by downfolding in reciprocal space. We exemplify the procedure using MnI$_2$ and NiI$_2$, which are known type II multiferroics having spiral order and the helimagnetic metal MnTe$_2$. We analyze how the magnitude of
spin splitting depends on orbital composition of bands, and we show that
spin splitting is maximized for states having large odd-orbital ($p$-type) character. It is straightforward to generalize the framework to handle response functions for helimagnets using only the primitive unit
cell and the present downfolding procedure thus strongly facilitate theoretical progress in the field.
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Superconductivity
Exploring the conventional and anomalous Josephson effects at arbitrary disorder strength in systems with spin-dependent fields
Maryam Darvishi, F. Sebastián Bergeret and Stefan Ilić
We present a theory of the Josephson current in
superconductor-normal metal-
superconductor (SNS) junctions in the presence of generic
spin-dependent fields, such as
spin-orbit coupling (SOC), Zeeman fields, and altermagnetism. We consider systems with arbitrary disorder strength, going beyond the usual diffusive and ballistic approximations. Using the linearized quasiclassical Eilenberger equation, we derive a compact expression for the Josephson current, which is then applied to various situations of experimental interest. First, we investigate the
evolution of the Josephson critical current in an applied
magnetic field in the presence of Rashba and Dresselhaus SOC, and discuss how this dependence can be used to probe SOC in the junction. We then study the anomalous Josephson ($\varphi_0$) effect in systems with Rashba SOC and show that it remains robust over a wide range of disorder strength, and can even be enhanced by moderate disorder in sufficiently long junctions. Finally, we investigate the Josephson current in disordered junctions with altermagnets, and show how the $0$-$\pi$ transition in such systems is suppressed by disorder. Our results may be useful for describing experimental setups with high-mobility samples, which nevertheless always contain some amount of disorder, and where neither purely ballistic nor diffusive approximations are adequate.
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Mesoscale and Nanoscale Physics
Engineering Ferrimagnetic Interactions in Molecular Quantum Systems
Elia Turco, Fupeng Wu, Annika Bernhardt et al. (+6 more)
Achieving long-range ferrimagnetic order in purely organic systems remains a major challenge in molecular magnetism. Here we report the synthesis and characterization of heterospin-coupling motifs, formed by covalently linking
spin-1/2 and
spin-1 triangular nanographenes. A combined solution-phase and on-surface synthetic strategy yields three distinct compounds, whose structures are elucidated by bond-resolved scanning probe microscopy. Starting from a
spin-1/2–
spin-1 dimer as the elemental ferrimagnetic unit, we employ inelastic electron tunneling spectroscopy to resolve low-energy
magnetic excitations and extract the parameters of the Heisenberg
Hamiltonian. Extension to trimeric architectures results in two distinct
spin configurations, with compensated ($S=0$) and uncompensated ($S=3/2$) ferrimagnetic ground states. The Heisenberg model accurately describes all
magnetic transitions, offering direct insight into increasingly complex
spin Hamiltonians. These findings establish a molecular platform for designing tunable heterospin systems with robust exchange interactions, opening routes toward multi-level
spin encoding in qudit-based
quantum technologies.
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All authors Elia Turco, Fupeng Wu, Annika Bernhardt, Nils Krane, Ji Ma, Roman Fasel, Michal Juriček, Xinliang Feng, Pascal Ruffieux
Materials Science · Cross-listed from physics.optics
Comparative performance of three optical biosensing platforms for SARS-CoV-2 antibodies detection in human serum
Agostino Occhicone, Alberto Sinibaldi, Peter Munzert et al. (+5 more)
This study presents a rigorous comparative analysis of two label-free optical biosensing platforms, Bloch surface wave (BSW) and microring resonator (MRR), for the detection of SARS-CoV-2 antibodies in human serum. To ensure direct comparability, a new BSW readout system was established alongside an existing MRR platform, allowing assays to be conducted under nearly identical experimental conditions. Both sensors were functionalized with various SARS-CoV-2 Spike and Nucleocapsid
protein variants to capture specific host antibodies. The results demonstrate that both platforms provide rapid, quantitative, and sensitive detection of anti-Spike and anti-Nucleocapsid antibodies without the need for secondary labels. Furthermore, the platforms show excellent agreement with longitudinal serology
benchmarks and high repeatability across different biochip batches. This work establishes both BSW and MRR technologies as powerful, low-cost candidates for next-generation clinical diagnostics and serological surveillance.
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All authors Agostino Occhicone, Alberto Sinibaldi, Peter Munzert, Jordan N. Butt, Ethan P. Luta, Diego M. Arévalo, Francesco Michelotti, Benjamin L. Miller
Strongly Correlated Electrons
Co-operating multiorbital and nonlocal correlations in bilayer nickelate
Evgeny A. Stepanov, Steffen Bötzel, Ilya M. Eremin et al. (+1 more)
The interplay of multiorbital physics and nonlocal self-energy effects is studied within an effective three-orbital model for the high-pressure normal state of superconducting
bilayer nickelate La$_3$Ni$_2$O$_7$. The model is solved within an advanced many-body framework capturing $k$-dependent correlations beyond dynamical mean-field theory. Different low-energy scenarios subtly depend on the strength of the interorbital interaction, either placing the notorious flat $\gamma$ quasiparticle band in the occupied part of the spectrum, or letting it cross the
Fermi level. In the latter case, intriguing
spin-polaron formation due to the scattering of electrons with paramagnon excitations takes place. This leads to bound states appearing as a shadow band with incoherent low-energy spectral weight below the
Fermi level. Our results uncover additional competing states that exist in
bilayer nickelates and could explain the controversy of recent angle-resolved photoemission experiments.
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All authors Evgeny A. Stepanov, Steffen Bötzel, Ilya M. Eremin, Frank Lechermann
Materials Science
Giant photostriction in lead-free ferroelectric stemming from photo-excited thermalized carriers
Gaëlle Vitali-Derrien, Oana Condurache, Antoine Ducournau et al. (+14 more)
Ferroelectrics are polar materials whose polarization can be switched by applying electric fields; they offer unique opportunities to develop performant photostrictive materials, i.e., materials that can deform under visible light illumination. Naturally devoid of inversion
symmetry, they exhibit original photogalvanic effects such as the Bulk Photovoltaic Effect, which relies on “hot” photoexcited carriers. It has long been thought that the electric field generated by this effect may couple to the natural piezoelectric abilities of ferroelectrics to provide large photoinduced deformations. However, due to competing effects, such as thermal dilatation, deformation potential, polarization, or depolarizing-field screening by thermalized carriers, it remains unclear which microscopic phenomena govern the photoinduced deformations in classical ferroelectric materials. Here, we demonstrate the largest photoinduced deformation measured in a ferroelectric thin film. Reaching 1 %, this
giant photostriction likely originates from the contribution of thermalized photoinduced carriers.
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All authors Gaëlle Vitali-Derrien, Oana Condurache, Antoine Ducournau, Pascale Gemeiner, Maxime Vallet, Nicolas Guiblin, Thomas Antoni, Sylvia Matzen, Pascal Ruello, Dagmar Chvostova, Tetyana Ostapchuk, Jirka Hlinka, Simon Hurand, Mouna Khiari, Houssny Bouyanfif, Charles Paillard, Pierre-Eymeric Janolin
Materials Science
Bulk versus interface nucleation of CO$_2$ hydrates from computer simulations
Joanna Grabowska, Samuel Blazquez, Carlos Vega et al. (+1 more)
Gas hydrates are of great relevance to both the oil industry and the environment. Understanding how these solid structures nucleate from aqueous solutions is essential to controlling their formation. Experimental studies have often suggested that hydrate nucleation originates at the interface between the aqueous phase and the guest-molecule reservoir. To assess this hypothesis, we perform molecular dynamics simulations of CO$_2$ hydrate nucleation. First, we place hydrate seeds at different positions relative to the interface and monitor their
evolution, finding that seeds embedded in the bulk are more likely to grow than those located near or at the interface. Second, we analyse spontaneous nucleation simulations with and without an interface. Our previous work showed that nucleation rates are indistinguishable in both systems, strongly indicating that the interface does not play a role. Here, trajectory analysis reveals that hydrates nucleate in regions of locally high CO$_2$ concentration, which arise spontaneously in the bulk and are not associated with the interface. Our results indicate that hydrate nucleation does not preferentially occur at the interface, at least at the at deep supercooling conditions explored in this work. Further work at higher temperatures, and considering alternative nucleation locations, is needed to reconcile experiments and simulations, and thereby reach a deep understanding of the mechanism of hydrate formation.
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All authors Joanna Grabowska, Samuel Blazquez, Carlos Vega, Eduardo Sanz
Materials Science
Switching magnetic spin-states using small magnetic fields in compositionally complex Sm(M7)O$_3$
R. K. Dokala, M. Geers, P. Nordblad et al. (+2 more)
High-
entropy perovskites (HEPs) offer a unique platform for exploring
magnetic phenomena arising from extreme B-site chemical disorder. In Sm(M7)O$_3$, where there are 7 cations in equal amounts at the B-site; M = Ti, Cr, Mn, Fe, Co, Ni, Cu), we observe long-range
antiferromagnetic ordering near 105 K accompanied by a small but robust excess
magnetic moment intrinsic to the chemically disordered
lattice. This uncompensated moment is evident from ZFC-FC irreversibility, shifts in the isothermal M(H) loops, and discrete remanent states identified through direct-current-demagnetization measurements. Remarkably, cooling fields as small as $\pm$ 20 Oe are sufficient to select the direction of the excess moment, and the chosen
magnetic state remains stable against applied fields up to 50 kOe. A low-temperature anomaly in the remanent magnetization further reveals a secondary contribution from the Sm$^{3+}$ sublattice, although the primary origin of the excess moment resides in the B-site AFM sublattice.
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All authors R. K. Dokala, M. Geers, P. Nordblad, R. Clulow, R. Mathieu
Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Charging Quantum Batteries via Dissipative Quenches
Riccardo Grazi, Donato Farina, Niccolò Traverso Ziani et al. (+1 more)
We investigate work extraction in open
quantum batteries composed of interacting
spin chains weakly coupled to engineered environments. Focusing on two- and four-
qubit XX models initially prepared in thermal Gibbs states, we analyze how dissipation and dephasing, acting either locally or collectively, can generate and shape ergotropy during both transient and steady-state dynamics. By introducing a continuous interpolation between parallel and collective noise channels, we systematically characterize the impact of environmental structure on work extractability. We show that purely dissipative dynamics can activate finite ergotropy from completely passive thermal states, giving rise to temperature-dependent transient regimes where hotter initial states temporarily outperform colder ones in an ergotropic Mpemba-like fashion. In contrast, collective dissipation leads to steady states whose passivity crucially depends on the initial temperature and system size, a behavior we trace back to the emergence of non-trivial dark subspaces. Finally, we demonstrate that dephasing channels suppress both transient advantages and steady-state work extraction, highlighting the qualitative difference between dissipative and dephasing environments.
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All authors Riccardo Grazi, Donato Farina, Niccolò Traverso Ziani, Dario Ferraro
Disordered Systems and Neural Networks
FlowEqProp: Training Flow Matching Generative Models with Gradient Equilibrium Propagation
Alex Gower
We introduce Gradient
Equilibrium Propagation (GradEP), a mechanism that extends
Equilibrium Propagation (EP) to train energy gradients rather than energy minima, enabling EP to be applied to tasks where the learning objective depends on the velocity field of a convergent dynamical system. Instead of fixing the input during dynamics as in standard EP, GradEP introduces a spring potential that allows all units, including the visible units, to evolve, encoding the learned velocity in the
equilibrium displacement. The spring and resulting nudge terms are both purely quadratic, preserving EP's hardware plausibility for neuromorphic implementation. As a first demonstration, we apply GradEP to flow matching for generative modelling - an approach we call FlowEqProp - training a two-hidden-layer MLP (24,896 parameters) on the Optical Recognition of Handwritten Digits
dataset using only local
equilibrium measurements and no backpropagation. The model generates recognisable digit samples across all ten classes with stable training dynamics. We further show that the time-independent energy landscape enables extended generation beyond the training horizon, producing sharper samples through additional inference-time computation - a property that maps naturally onto neuromorphic hardware, where longer relaxation yields higher-quality outputs. To our knowledge, this is the first demonstration of EP training a flow-based generative model.
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Mesoscale and Nanoscale Physics
Relation between the areal rate of Zitterbewegung and Berry curvature in two-band systems
Sonja Predin
We introduce the Zitterbewegung areal rate operator to study the relation between the orientation of trembling motion and band
topology. Constructed from the oscillatory interband displacement and velocity, this operator distinguishes clockwise from anticlockwise motion. For a generic gapped two-band
Hamiltonian in two dimensions, we show that the Zitterbewegung areal rate is proportional to the Berry
curvature. The derivation uses only spectral projectors and is therefore gauge invariant. We also demonstrate that the Zitterbewegung areal rate operator is time-independent and a constant of motion at each momentum, although the displacement and velocity from which it is constructed oscillate in time. Its sign distinguishes anticlockwise from clockwise Zitterbewegung and coincides with the sign of the Berry
curvature. For wave packets narrowly localized around the isolated massive Dirac points, the Zitterbewegung chirality equals the sign of the local Chern contribution. The Chern number can therefore be reconstructed from the orientations of the Zitterbewegung motion around the individual Dirac points.
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Materials Science
Equivariant Many-body Message Passing Interatomic Potentials for Magnetic Materials
Cheuk Hin Ho, Cas van der Oord, James P. Darby et al. (+11 more)
Magnetism governs key properties of materials used in energy, data storage, and spintronic technologies, yet its complex coupling to
lattice and electronic degrees of freedom challenges conventional first-principles approaches. We introduce an equivariant message-passing graph neural network that embeds atomic
magnetic moments as explicit degrees of freedom, enabling the learning of
magnetic interactions beyond collinear approximations. The model learns physically consistent and transferable representations of
magnetic behaviour and can incorporate
spin-orbit coupling, achieving near density-functional-theory accuracy with strong data efficiency across diverse
magnetic systems by fine-tuning from a pre-trained model. Applications to structural transformations, finite-temperature
magnetic phenomena, and materials screening for strongly
spin-orbit coupled materials demonstrate transferable
magnetic behaviour, establishing a practical foundation for data-driven, high-throughput discovery of complex
magnetic materials.
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All authors Cheuk Hin Ho, Cas van der Oord, James P. Darby, Theo Keane, Raz L. Benson, Cristian Rebolledo Espinoza, Rutvij Kulkarni, Elina Spinu, Michail Papanikolaou, Richard Tomsett, Robert M. Forrest, Jonathan J. Bean, Gábor Csányi, Christoph Ortner
Soft Condensed Matter
Cohesion from Action-Dependent Perception in Decision-Based Active Matter
Julian Giraldo-Barreto and Viktor Holubec
Many biological and artificial
agents reorient by locally optimizing a utility over a finite set of candidate actions. We show that decision rules based on pairwise additive scores over candidate-dependent interaction neighborhoods provide a generic mechanism for a cohesive bias in active matter: the utility factorizes into the product of an average interaction score and the number of recruited neighbors. Maximizing it therefore couples the decision to neighbor recruitment as a structural consequence of the decision process itself. For
alignment-based utilities and orientational candidate actions, our models reduce to a variant of the Vicsek model when the interaction neighborhood is independent of the candidate action. This identifies the mechanism behind our previous finding that maximizing predicted future
alignment produces cohesive flocks, and extends it to arbitrary candidate sets and additive utilities, provided that at least some actions can have positive scores. We further study scanning
alignment, in which
agents evaluate a topological neighborhood within a finite
vision cone along each candidate heading, without future-state predictions. Even the baseline variant—with a sign-changing score and zero-neighbor candidates eligible—already produces nontrivial cohesive flocks and swarms in open, unbounded two-dimensional space. Excluding zero-neighbor candidates, or replacing the score with a non-negative one, yields substantially richer collective behavior that additionally includes swirling. We focus on the former as the most biologically motivated choice. The swirling states occupy an interval of noise intensities and spontaneously reverse their sense of rotation; the rotation appears to set in abruptly at the low-noise edge and to die away gradually at the high-noise one.
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Materials Science
Unveiling the Core of Materials Properties via SISSO and Sensitivity Analysis
Lucas Foppa and Matthias Scheffler
Interpretable AI can reveal physical principles governing intricate materials properties by uncovering explicit relationships between physical parameters and target properties. The sure-independence screening and sparsifying operator (SISSO) symbolic-regression approach identifies analytical expressions that correlate a target property with a small set of parameters, termed materials genes, selected from a large pool of candidates. However, multiple gene combinations can yield equally accurate SISSO models, with individual genes contributing with different weights. Here, we establish a derivative-based sensitivity analysis that resolves the non-uniqueness of symbolic-regression descriptions, enhances interpretability, thereby enabling deeper physical insight. This analysis reveals how distinct gene combinations encode equivalent information and identifies valence orbital radii,
nuclear charges, and their products as the key quantities governing the
equilibrium lattice constant of perovskites.
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Materials Science · Cross-listed from physics.comp-ph
Direction-aware topological descriptors for elastic stiffness tensor prediction in porous materials
Rafał Topolnicki, Michał Bogdan, Jakub Malinowski et al. (+3 more)
Classical topological descriptors used in topological data analysis (TDA) are invariant under permutations of spatial axes and therefore cannot represent the loading direction, which is essential for modeling anisotropic mechanical response. Here, this limitation is addressed by introducing a direction-aware TDA framework in which the loading axis is explicitly embedded into filtration functions used to compute both persistent homology and Euler characteristic profile descriptors. We apply this framework to predict the full elastic stiffness tensor of porous microstructures using non-directional as well as direction-aware descriptors of the structures as well as convolutional neural networks trained directly on the voxelized structure. We show that the performance of all those are comparable on the diagonal uniaxial, Poisson, and shear components. However for the twelve off-diagonal, normal shear coupling components - which govern elastic anisotropy and are the hardest to predict - only direction-aware
topology retains meaningful predictive power, with all baselines, non-directional descriptors and the CNN collapsing to near-chance accuracy. When used as inputs to gradient-boosted tree models, the proposed descriptors match or exceed the accuracy of the convolutional neural network specifically on these hardest-to-predict coupling terms, despite relying on a compact, physically interpretable representation that is orders of magnitude smaller than the raw voxel grid. Overall, the results establish direction-aware TDA as a practical route for linking porous microstructure to the full anisotropic elastic response, capturing coupling terms that conventional descriptors and end-to-end deep learning models fail to resolve.
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All authors Rafał Topolnicki, Michał Bogdan, Jakub Malinowski, Bartosz Naskręcki, Maciej Harańczyk, Paweł Dłotko