Materials Science
Competing ferromagnetic and antiferromagnetic interactions in non-altermagnetic Ru$_{1-x}$Cr$_{x}$O$_{2}$
David T. Plouff, Nawsher J. Parvez, Subhash Bhatt et al. (+4 more)
We investigate the proposal of hole doping RuO$_{2}$ via alloying with Cr ions to induce altermagnetism. Thin film samples of Ru$_{1-x}$Cr$_{x}$O$_{2}$ ($0 \leq x \leq 0.28$) were prepared by reactive magnetron co-sputtering on TiO$_{2}$ substrates, with epitaxial nature verified by X-ray diffraction and composition depth profiles determined by X-ray photoelectron spectroscopy combined with Ar etching.
Neutron diffraction measurements of samples with $x = 0$ and $x = 0.23$ at low temperatures show no evidence of long-range altermagnetic order with
spins oriented along the $c$-axis or within the $ab$-plane. In contrast, temperature dependent susceptibility measurements in samples with $x \geq 0.16$ show a gradual downturn below $T\approx20~$K, suggestive of
antiferromagnetic interactions, although this coexists with
ferromagnetic hysteresis and remnant magnetization at $4~$K for samples with $x \geq 0.23$. Together, our magnetometry and
neutron scattering measurements suggest the coexistence of antiferromagnetically coupled
ferromagnetic CrO\textsubscript{2} clusters. This indicates that Cr ions do not hole dope Ru bands to induce an altermagnet state, but rather the holes remain localized to the Cr ions.
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All authors David T. Plouff, Nawsher J. Parvez, Subhash Bhatt, Xixiang Zhang, Adam A. Aczel, Jonathan Gaudet, John Q. Xiao
Strongly Correlated Electrons
Proximity-induced charge transfer, strain and magnetic exchange in graphene/CrSBr heterostructure
Asish K. Kundu, Anil Rajapitamahuni, Niraj Aryal et al. (+8 more)
Stacking van der Waals materials provides a powerful route to engineer emergent electronic and
magnetic behaviors through proximity-driven interactions. The
graphene/CrSBr
heterostructure has emerged as a compelling platform in this frontier, exhibiting exotic macroscopic responses– including uniaxial surface-plasmon-polariton propagation and an unconventional
quantum Hall effect– indicative of strong interfacial electronic and
magnetic coupling. However, a microscopic electronic landscape governing these phenomena has remained elusive. Here, we provide a comprehensive spectroscopic characterization of the
graphene/CrSBr interface using a combination of angle-resolved photoemission spectroscopy (ARPES), low-energy electron microscopy (LEEM), and density functional theory. We resolve a massive redistribution of interfacial charge that concurrently hole dopes
graphene and populates the quasi-one-dimensional
spin-polarized conduction band of CrSBr, resulting
insulator-to-metal transition in the interfacial CrSBr layer. Furthermore, electronic structure of CrSBr exhibits strong momentum-dependent renormalization distinct from conventional charge doping, and theoretical modeling supported by Raman spectroscopy points to additional interfacial compressive strain. In addition, ARPES reveals a splitting-like feature in the
graphene Dirac cone consistent with
spin degeneracy lifting, providing possible evidence of
magnetic proximity coupling. These findings provide crucial microscopic insight into the system's optical and transport responses and establish
graphene/CrSBr as a versatile platform for charge-transfer control, strain-driven band engineering,
magnetic-proximity coupling, and directionally confined excitations for next-generation spintronic and nanophotonic devices.
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All authors Asish K. Kundu, Anil Rajapitamahuni, Niraj Aryal, Turgut Yilmaz, Margalit L. Feuer, Suji Park, Houk Jang, Abhay Pasupathy, Xavier Roy, Jerzy T. Sadowski, Elio Vescovo
Strongly Correlated Electrons
Magnetoresistive Memory in the Paramagnetic Phase of Eu$_5$In$_2$As$_6$
Sudhaman R. Balguri, Mira B. Mahendru, Rourav Basak et al. (+9 more)
Magnetoresistive materials that respond sensitively to applied fields are central to modern data storage technologies. Here we unveil a novel Magnetoresistive
Memory (MRM) in Eu$_5$In$_2$As$_6$, where the electrical resistivity depends not only on the magnitude but also on the history of the applied
magnetic field. Such an effect has been reported in only two classes of strongly correlated electron systems: perovskite manganites and pyrochlore iridates. In both cases, the effect has been observed in the magnetically ordered phase. It has been attributed to metastable
magnetic states in manganites and conducting domain walls in iridates. Remarkably, the MRM in Eu$_5$In$_2$As$_6$ onsets at twice the
antiferromagnetic transition temperature, well within the paramagnetic phase. The temperature, field, and time dependence of resistivity suggest that either a hidden order or a fluctuating phase with short-range correlations underlies this effect. Our results offer MRM as a new platform for
quantum sensing and
memory technologies, and encourage searching for MRM in related materials.
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All authors Sudhaman R. Balguri, Mira B. Mahendru, Rourav Basak, Enrique O. González-Delgado, Adam A. Aczel, David E. Graf, Andreas Rydh, Christopher C. Homes, Jonathan Gaudet, Ying Ran, Alex Frano, Fazel Tafti
Mesoscale and Nanoscale Physics
Angular Momentum Quantization of a Charge-flux Composite: Quantum Electrodynamic Approach
Kicheon Kang
The fractional angular momentum of a two-dimensional charge-flux composite is a well-established phenomenon usually derived from a semiclassical
Hamiltonian. However, when the composite is treated as an isolated system in free two-dimensional space, the fundamental rotational and reflection
symmetries of the $O(2)$ group demand that its total angular momentum is strictly quantized. We address this conceptual discrepancy by applying a full
quantum electrodynamic (QED) approach combined with Noether's
theorem. We demonstrate that the interaction between the charge and flux, mediated by the
vacuum electromagnetic field, generates an intrinsic interaction angular momentum composed of both field momentum and hidden relativistic momentum. This gauge-invariant interaction angular momentum exactly compensates for the fractional part of the kinetic angular momentum. Consequently, the net angular momentum of the composite strictly follows the integer or half-integer quantization rule. Our formalism clarifies that the conventional fractional
spin corresponds to the expectation value of the kinetic angular momentum within the perturbed QED ground state. It also elucidates why the standard classical field angular momentum definition fails to capture this in two dimensions, due to non-vanishing boundary terms.
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Statistical Mechanics
Random walks in Dirichlet random environment in dimension $d+1$
Guillaume Barraquand, Alexander K. Hartmann and Pierre Le Doussal
The atypical behaviour of random walks in time-dependent random environment was recently related to Kardar-Parisi-Zhang (KPZ) growth. While this is now well-understood in spatial dimension $d=1$, further efforts are necessary to better understand these connections in dimensions $d>1$. In this paper, we study this problem numerically for $d=1, 2$ and $3$, focusing on a discrete model with Dirichlet distributed transition probabilities. This model is a generalization of an integrable model in $d=1$, and it has the advantage of admitting an explicit, product-form, stationary measure. We verify that the growth of the variance of the logarithm of point-to-point probabilities, namely from the origin to position $x$ in time $t$, is compatible with KPZ growth in dimension $d=1$ and $d=2$. In spatial dimension $d=3$, we confirm the existence of a phase transition as the angle $\vert x\vert /t$ increases and we obtain a lower bound based on an exact second moment calculation. We find that in the weak disorder phase the point-to-point probability acquires a heavy tailed distribution, and that in the strong disorder phase the cumulants of its logarithm grow with time. Further, we show that for this model, we can compute exactly the sample to sample variance of the thermal average $\overline{ \langle x \rangle^2}$ and that it is related to the extreme
diffusion coefficient introduced recently.
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Strongly Correlated Electrons
Coherence-driven origin of metamagnetism in anisotropic heavy-fermion systems
Ewan Scott, Zheyu Wu, Theodore I. Weinberger et al. (+2 more)
A number of heavy-
fermion materials exhibit
magnetic field-induced metamagnetism: on applying a field along the
magnetic hard axis, the magnetization first rises gradually, then jumps abruptly once a critical field is reached. Despite decades of phenomenological modeling, the microscopic origin of the pronounced
magnetic anisotropy underlying this behavior has remained unresolved. The same is true of a related, long-standing puzzle: an anomalous maximum in the hard-axis susceptibility versus temperature. Both are complicated in $5f$ compounds by the dual localized-itinerant character of the relevant electrons. Here we develop an analytic $c$–$f$ theory of
magnetic anisotropy in heavy-
fermion metamagnets, identifying the mixed susceptibility $\chi_{\rm cf}(T,h,p)$ as a single thermodynamic observable that unifies the anisotropic response across temperature, field, and pressure. We test this theory against primary and literature data for the heavy-
fermion superconductor UTe$_2$, finding excellent quantitative agreement in the temperature, field, and pressure
evolution of its
magnetic anisotropy – including a Kondo-coherence origin for the anomalous hard-axis susceptibility maximum, which we show is directly connected to the metamagnetic transition itself. Our results establish a general, microscopic, coherence-driven framework for anisotropic metamagnetism, applicable across the broad class of heavy-
fermion compounds that display this phenomenology.
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All authors Ewan Scott, Zheyu Wu, Theodore I. Weinberger, Alexander G. Eaton, Michal P. Kwasigroch
Disordered Systems and Neural Networks
Dynamical Criticality of a Machine-learning-assisted Monte Carlo algorithm for a Mean-Field Spin Glass model
Seiya Miyamoto, Masayuki Ohzeki and Yoshihiko Nishikawa
We critically assess the performance of an autoregressive generative neural network model by applying it to an
antiferromagnetic Ising model on a random regular graph. We train the network on
equilibrium configurations in the low-temperature
spin-glass phase of the model and perform Monte Carlo simulations using
spin configurations generated by the network. The relaxation time of the Monte Carlo simulations drastically decreases with increasing the size of the training
dataset and converges to an optimal value. The dynamical exponent characterizing the growth of the optimal relaxation time as a function of the system size is slightly reduced compared to the local Monte Carlo dynamics. However, we find that the size of the training
dataset to achieve the optimal performance grows much faster with the system size than the relaxation time, implying that the total training cost eventually hinders a practical use of the method at large system sizes.
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Materials Science
Role of Resonant $\mathbf{k}$-Points in the Transient Optical Response of Pumped Germanium
Amir Eskandari-asl, Giacomo Inzani, Matteo Lucchini et al. (+1 more)
Pump-induced transient optical properties combine contributions from electronic states throughout the Brillouin zone, but the relative relevance of off-resonant and l-
photon resonant
crystal momenta has remained unexplored. We address this issue in pumped germanium by resolving the transient absorptive response into momentum-space classes defined by the presence or absence of 1-, 2-, and 3-
photon resonances with respect to the pump. Using the Dynamical Projective Operatorial Approach together with the related generalized linear response theory, we compute the differential imaginary part of the dielectric function and evaluate the contributions of each resonance class. Resonant regions account for nearly the entire optical response, whereas points outside the identified resonance sets contribute only negligibly. Nevertheless, the 2-
photon-resonant set, although containing more than 98% of the residual (post-pump) excitation population, does not reproduce the full transient spectrum. Conversely, resonance classes with very small residual populations generate non-negligible contributions to the transient optical properties. This mismatch shows that the transient optical weight is not determined solely by the real-charge dynamics (which results in post-pulse residual excitation population) and is consistent with substantial virtual pump-induced contributions, whose dominant optical weight nevertheless arises from the resonant regions of momentum space. The class-resolved phase of the dominant 2$\omega_{\mathrm{pu}}$ oscillations further shows that, whenever a class contributes appreciably, the phase of its oscillatory component follows that of the corresponding full signal. The resulting decomposition provides a momentum-resolved connection among multi-
photon resonances and transient optical observables in a realistic material.
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All authors Amir Eskandari-asl, Giacomo Inzani, Matteo Lucchini, Adolfo Avella
Materials Science · Cross-listed from quant-ph
Coupling phase interference effects in a multimode cavity magnonics system
M. Avicena, G. Bourcin, V. Vlaminck et al. (+2 more)
Coupling phases play a decisive yet often overlooked role in cavity magnonics, particularly in complex multimode systems. Here, we investigate phase-mediated interference effects in a cavity magnonics system comprising a four-post re-entrant microwave cavity coupled to Yttrium Iron Garnet (YIG) spheres. Using an input-output model that explicitly accounts for both internal and external coupling phases, we achieve agreement with experimental microwave transmission measurements. Our results unravel the emergence of a positionally-dependent uncoupled mode due to interference of cavity
photon-
magnon (internal) coupling phases. Further, we experimentally observed large nonreciprocity at the antiresonance frequencies and show that this feature arises due to the far-detuned modes' odd parity cavity
photon-probe (external) coupling phase interfering with the internal coupling phases. Bridging theory, simulation and experiment, these results establish coupling-phase engineering as a key principle for accurately modeling and designing multimode cavity magnonics devices.
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All authors M. Avicena, G. Bourcin, V. Vlaminck, J. Bourhill, V. Castel
Soft Condensed Matter
A Theoretical Framework for the Coupling of Macroscale-Nanoscale Mechanochemical Phenomena in Condensed Matter
Brenden W Hamilton
The field of covalent mechanochemistry has transitioned from fundamental science to engineering applications, yet it lacks a robust theoretical framework for predicting reaction kinetics in condensed matter. Existing analytical models fail under realistic conditions where macroscopic strains drive molecular-scale deformations that are highly non-linear. We develop a non-perturbative theoretical framework that captures activation barrier changes in highly strained molecules undergoing complex, non-linear deformations, describing the macroscale-nanoscale coupling of phenomena. The framework yields general expressions, parameterizable from atomistic simulations, enabling multiscale prediction of mechanochemical behavior. By presenting the expressions in terms of general observables, this work enables predictions of mechanochemical effects from simple structure optimization calculations, enabling the use of high level
quantum chemical methods. We demonstrate this approach on the mechanochromic
polymer spiropyran, showing how non-linear strain fields govern mechanophore activation.
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Statistical Mechanics
Derivation of the Boltzmann equation with no "molecular chaos"-type approximation
Victor F. Los
The paper resolves the problem of the derivation of a completely closed
evolution equation for $s$-particle distribution function $F_s(t)$ ($s \le N$) from the Liouville equation for $N \gg 1$-particle distribution function $F_N(t)$ with arbitrary initial condition $F_N(0)$ and without any use of the "molecular chaos" type approximation. The initial correlations are accounted for in this equation in the kernel governing the
evolution of $F_s(t)$ via the special projection operator which exactly transforms the inhomogeneous Nakajima-Zwanzig Generalized Master Equation (GME) with an irrelevant initial condition term into the homogenous one. This equation is further simplified by presenting its kernel in the linear in the particles' density $n$ approximation. In this approximation the equations for one-particle $F_1(t)$ and two-particle $F_2(t)$ distribution functions are derived. It is shown that the terms describing the influence of initial correlations in the equation for $F_1(t)$ disappear at the large timescale $t \sim t_{\text{rel}} \gg t_{\text{cor}}$ ($t_{\text{cor}}$ is a short correlation time as compared to a relaxation time $t_{\text{rel}}$ of $F_1(t)$) resulting in the linear Boltzmann equation. This equation can be presented as the nonlinear Boltzmann equation in the time interval $t_{\text{cor}} \ll t \ll t_{\text{rel}}$. At $t_{\text{rel}} \to \infty$ (mean free path $l \to \infty$) the Boltzmann equation holds for all finite times $t \gg t_{\text{cor}}$.
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Soft Condensed Matter
Let's Stalk About Membranes: Committor-Based Enhanced Sampling of Stalk Formation
Giorgia Rossi, Enrico Trizio, Davide Bochicchio et al. (+2 more)
Membrane fusion is essential for cellular communication and function, and understanding how two lipid
bilayers merge is key to informing therapeutic strategies. Functionalized nanoparticles have recently emerged as synthetic fusogens, but the molecular mechanisms driving this process remain unclear, partly because fusion involves transitions over high free-energy barriers, difficult to capture in molecular simulations. While enhanced sampling methods can address this problem, they also rely on the definition of collective variables, which are especially hard to define for fusion, as it arises from the collective rearrangement of many molecules and cannot be easily reduced to a simple intuitive coordinate. Here, we study stalk formation, the first step of fusion, mediated by an amphiphilic gold nanoparticle, by employing an enhanced sampling strategy based on the committor function, machine-learned through a self-consistent procedure. This method requires minimal prior knowledge of the system and leverages the learned committor function as an effective collective variable, enabling uniform sampling of the entire pathway. From the resulting reactive trajectories and extensive transition region sampling, we obtain converged free-energy estimates and mechanistic insight into stalk formation.
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All authors Giorgia Rossi, Enrico Trizio, Davide Bochicchio, Giulia Rossi, Michele Parrinello
Mesoscale and Nanoscale Physics
Frequency-dependent electron-phonon coupling and vibrational responses in tight-binding and continuous Dirac models with nuclear velocity correction
Paolo Fachin, Francesco Macheda, Paolo Barone et al. (+1 more)
The
nuclear motion induces in the electronic atomic orbitals a
nuclear-velocity-dependent phase (also known as electron-translation factor), which modifies the effective
Hamiltonians constructed from localised atomic orbitals. In this work, using an Ehrenfest Lagrangian approach for the localised atomic orbitals (LCAO) and tight-binding methods, we determine, at any order in the
nuclear velocity, the equations of motion and the vibrational responses within a linear response formalism, focusing on the tight-binding assessment of the Born effective charges and the force-constant
matrix. The appearance of
nuclear-velocity-dependent Peierls-like phases in the non-local part of the interactions restores the all-electron sum rules for frequency-dependent vibrational responses. In tight-binding models these corrections crucially modify the vibrational response from a qualitative point of view, also yielding contributions required to capture phenomena such as vibrational circular dichroism. We test these corrections in the tight-binding model for metallic gapped
graphene - finding excellent agreement with ab initio calculations - and for the topological time-reversal
symmetry breaking Haldane model.
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All authors Paolo Fachin, Francesco Macheda, Paolo Barone, Francesco Mauri
Mesoscale and Nanoscale Physics
Frequency-Division Multiplexing in Magnonic Waveguides
Alina-Cristina Bunea, Laurentiu Stoleriu, Giacomo Talmelli et al. (+3 more)
Frequency-division multiplexing is a key functionality for wave-based information processing, enabling multiple information channels to coexist within the same physical medium. Here, we experimentally investigate
spin-wave multiplexing in a CoFeB waveguide using all-electrical excitation and detection. Two independently generated microwave signals are simultaneously coupled into the same
spin-wave waveguide through inductive
antennas and characterized using broadband vector network analyzer measurements. The transmission spectra obtained under single-channel and multiplexed operation exhibit excellent agreement, demonstrating that
spin waves with different frequencies and wavelengths propagate simultaneously without measurable interaction in the linear regime. The observation is confirmed using both dual-sweep and sweep-plus-single-tone excitation schemes. A theoretical analysis based on linear superposition and phase-sensitive detection explains the absence of observable inter-channel interference for independent microwave sources. Micromagnetic simulations further confirm that the amplitudes and wavevectors of the individual
spin-wave modes remain unchanged during co-propagation, demonstrating the absence of interaction over the entire propagation distance. The results provide direct experimental evidence that independent
spin-wave channels can coexist in a single waveguide and support the implementation of frequency-division multiplexing in future magnonic computing and microwave signal-processing architectures.
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All authors Alina-Cristina Bunea, Laurentiu Stoleriu, Giacomo Talmelli, Dan Neculoiu, Christoph Adelmann, Florin Ciubotaru
Soft Condensed Matter
Inferring activity from fluid flow in continuum models of active matter
Aditya Mohapatra, Sagarika Adhikary and Rajesh Singh
Active matter systems are driven out of thermodynamic
equilibrium by localized, microscale energy dissipation. While hydrodynamic continuum frameworks are highly successful at simulating these non-
equilibrium phenomena (the forward problem), characterizing real-world active materials is fundamentally bottlenecked by the difficulty of measuring active stresses directly. This paper addresses the inverse problem using deep learning: model inference and model selection from observable flow field data of active fluids. We formulate a generalized hydrodynamic inversion framework applied to two cornerstone paradigms of active continuum physics: Active Model H (representing scalar active matter) and Active Nematics (representing active systems with orientational order). We demonstrate that the kinetic energy spectrum obtained from the fluid flow fields preserve a high-fidelity signature of activity to infer parameters of active model H and active nematics. Our deep learning method presents a principled way to bear upon questions of model inference and selection given the flow field data in continuum models of active matter.
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Superconductivity
Power-Law Suppression of Superfluid Stiffness in High-Kinetic-Inductance NbN Films
Meenakshi Sharma, Hrishikesh Borah, Sandeep Singh et al. (+8 more)
Disorder is a powerful route to high kinetic inductance in superconducting ultrathin films, enabling compact high-impedance
quantum circuits. This functionality, however, comes at the cost of reduced phase
rigidity and potentially anomalous electrodynamics. Here, we use NbN microwave resonators with thicknesses down to 2.8 nm and sheet kinetic inductance up to 300 pH per square to probe how this trade-off reshapes the superconducting response. In the thinnest films, transport shows signatures of a Berezinskii-Kosterlitz-Thouless transition, while the microwave response reveals a pronounced low-temperature power-law suppression of the superfluid stiffness, inconsistent with Mattis-Bardeen theory. With increasing thickness, this anomalous regime is progressively suppressed, marking a continuous crossover toward conventional, gap-dominated electrodynamics. Cross-sectional transmission electron microscopy reveals a nanocrystalline twin-domain structure, pointing to oriented microstructural disorder as a crucial factor in the observed response. Overall, the crossover is governed by the ratio of superfluid stiffness to pairing energy, Theta(0)/Tc, identifying this ratio as a parameter governing the boundary between phase-fluctuation-dominated and gap-dominated superconducting electrodynamics in disordered nanofilms.
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All authors Meenakshi Sharma, Hrishikesh Borah, Sandeep Singh, Berit H. Goodge, Edouard Lesne, Sandra Nestler, Surinder P. Singh, Haolin Jin, Yejin Lee, Bernd Büchner, Uri Vool
Mesoscale and Nanoscale Physics
Exact theory of chirality-dependent p-wave magnetism and Edelstein effect in spin spirals
Börge Göbel, Tom G. Saunderson, Freia Opfermann et al. (+3 more)
Spin-momentum locking is widely regarded as a hallmark of relativistic
spin-orbit coupling. Here we demonstrate analytically that it can instead emerge solely from
magnetic chirality. Solving the minimal tight-binding model of electrons coupled to a
spin spiral using a generalized Bloch
theorem, we show that the spiral generates chirality-dependent p-wave magnetism characterized by the antisymmetric
spin texture $\boldsymbol{s}(\boldsymbol{k})=-\boldsymbol{s}(-\boldsymbol{k})$. The exact solution further yields closed-form expressions for the electrical conductivity and the
spin Edelstein susceptibility, revealing a microscopic mechanism by which
magnetic chirality alone can generate
spin polarization without
spin-orbit coupling, with direct implications also for chirality-induced
spin selectivity. In the strong exchange-coupling regime, the
spin-dependent physics of the
spin spiral becomes directly analogous to the orbital-dependent physics of electrons propagating through a non-
magnetic helix. Our work establishes a minimal exactly solvable model of chirality-induced
spin-momentum locking and
spin-charge conversion beyond the conventional
spin-orbit coupled paradigm.
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All authors Börge Göbel, Tom G. Saunderson, Freia Opfermann, Lennart Schimpf, Ersoy Şaş{\i}oğlu, Samir Lounis
Statistical Mechanics
Logarithmic scaling correction in quench dynamics of the J1-J2 Potts model
Kun Li and Wanzhou Zhang
In conventional quench dynamics governed by the Kibble-Zurek mechanism (KZM), the defect density generally decays as a pure power law of the quench rate. However, the KZM scaling of the two-dimensional (2D) XY model with topological phase transitions features prominent logarithmic corrections. Nevertheless, it remains unclear whether such logarithmic scaling corrections emerge in discrete-
spin systems that host two successive topological phase transitions under thermal quenches. This work investigates the J1-J2
antiferromagnetic Potts model and constructs its
equilibrium phase diagram. Based on the temperature ranges of the paramagnetic phase, quasi-long-range ordered (QLRO) phase, long-range ordered phase, and zero-temperature ground state, we design four quench protocols with distinct temperature intervals. Our results demonstrate that quenches terminating in the QLRO phase exhibit logarithmically corrected KZM scaling of the excess energy density, consistent with the dynamical universality class of the 2D XY model. In contrast, quenches ending in the LRO phase, including both finite-temperature and zero-temperature protocols, follow conventional power-law scaling. Our results clearly uncover the characteristic scaling corrections of the J1-J2 Potts model and offer theoretical guidance for future experimental investigations of KZM via photonic simulation platforms.
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Materials Science
From MLIPs to Microstructure: A High-Throughput Computational Framework to Design Spinodal Alloys in High-Dimensional Composition Spaces via Analytic Derivatives of CALPHAD Model Predictions
Courtney Kunselman, Doguhan Sariturk, Siya Zhu et al. (+2 more)
Identifying regions of design space subject to spinodal decomposition is a critical component of
alloy design in high-dimensional composition spaces. In cases where designers are seeking to exploit spinodal microstructures to tailor
alloy properties, prediction of microstructure
evolution and morphology is also needed. In this work, we present a Machine Learning Interatomic Potential (MLIP)-trained, CALPHAD-based, open-source workflow for high-throughput microstructure stability analysis and visualization. In this workflow, coherent strain contributions are captured via high-throughput MLIP elastic constant calculations. To predict microstructure morphology for compositions of interest, MLIP-generated thermodynamic models are fed into an elasto-chemical phase field simulation. Both stability analyses and phase-field simulations utilize analytically-derived Gibbs energy Hessians to improve computational efficiency and accuracy over finite difference approximations. We demonstrate this workflow by investigating microstructure stability in the Hf-Nb-Ti-V quaternary system.
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All authors Courtney Kunselman, Doguhan Sariturk, Siya Zhu, Vahid Attari, Raymundo Arroyave
Quantum Gases
Two- and three-body bound states in one-dimensional Fermi bipolaron with three-body interaction
O. Hryhorchak and V. Pastukhov
We discuss the ground-state properties of two bosonic (or
spin-1/2 fermionic in a singlet
spin state)
impurities immersed in a one-dimensional ideal
Fermi gas with only the three-body contact interaction accounted for. Despite its simplicity, the considered model is found to demonstrate a variety of medium-induced few-body bound states. Particularly, using variational calculations with trial wave functions that correctly take into account one particle-hole excitation, we predict the emergence of a dimer state and several trimer states over a wide range of the three-body coupling parameter.
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Other Condensed Matter
Core and valence photoemission spectra of atoms and molecules from a multichannel Dyson equation
Stefano Paggi, J. Arjan Berger and Pina Romaniello
We recently presented multichannel Dyson equations for the ab initio simulation of various spectroscopies. In particular, we introduced a multichannel Dyson equation for the description of photoemission spectra. In this work, we apply our approach to the simulation of photoemission spectra of atoms and molecules. We introduce a numerically efficient approach to calculate their spectral functions. We compare the spectra obtained within the multichannel Dyson equation to those obtained with full configuration interaction and the $GW$ method. We are thus able to show that the satellite features due to shake-up processes are significantly better described by the multichannel Dyson equation than by $GW$. Finally, we also discuss the slow convergence of the satellite energies with the size of the basis set and we propose a simple extrapolation method to reach the complete basis-set limit.
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Materials Science
Kinetically-Arrested Phase Separation leads to Tunable Domain Structures in Vapor-Deposited Glasses
A T M Mahbub Alahe, Thomas J. Ferron and Camille E. Bishop
The characteristic length scale of phase-separated organic thin film blends is a critical structural parameter governing the performance and functionality of organic electronic devices. The arrested morphologies of vapor-deposited organic thin films result from the interplay between thermodynamic driving forces and kinetic constraints during deposition. Here, we aim to isolate the role of kinetic effects in phase separation by varying the deposition rate at a constant substrate temperature for a co-deposited molecular glass blend of N,N'-bis(3-methylphenyl)-N,N'-diphenylbenzidine (TPD) and Disperse Orange 37 (DO37). The dependence of morphology on deposition rate is quantified using power spectral density (PSD) analysis of atomic force microscopy (AFM) images. Two distinct deposition rate-dependent length scales at the surface reveal how deposition kinetics directly influence domain size and film topography. Complementary Resonant Soft X-ray Scattering (RSoXS) measurements indicate that phase separation extends throughout the film thickness. These observations are consistent with the surface equilibration mechanism previously described for homogeneous vapor-deposited films, in which enhanced surface mobility allows molecules in the growing film to partially equilibrate into distinct surface-templated states during deposition. In the current work, this mechanism allows the multi-component blend to phase separate and coarsen into a structure with multiple length scales before kinetically arresting to an extent that depends on the deposition rate. The demonstration of finely tunable domain size with deposition rate provides strategies to design new organic electronic devices with desired morphologies.
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Mesoscale and Nanoscale Physics · Cross-listed from cs.AI
Reading and Steering Representations of Materials-Science Mechanisms in an Open-Weight Language Model
Markus J. Buehler
Large
language models can answer scientific questions, yet a correct output does not reveal whether the model represents or uses the governing physics. Here, using three open-weight Gemma 4 models (google/gemma-4-E4B-it, google/gemma-4-12B-it, google/gemma-4-31B-it) we identify three experimentally separable signatures of materials-science mechanism information: selective concept readability, relational encoding of qualitative constitutive orientation, and causal, context-dependent control of constrained engineering answers. We combine matched direct and Jacobian vocabulary readouts, option-free state geometry, a 60-law counterfactual
benchmark and causal interventions. In 50 held-out materials descriptions, three independently fitted Jacobian lenses reproduced concept ranks, and target-free word sets from both readouts enabled blinded identification of 9 of 10 mechanism families. A separate 72-
prompt benchmark produced mechanism-specific hidden-state neighborhoods, but an exact graph audit showed that this apparent physical organization was equally explained by numerical comparison. We therefore compared otherwise identical
prompts in which only the direction of the physical input was reversed, asking whether the resulting hidden-state movement followed the supplied constitutive law. These state transformations ordered direct, physically neutral and inverse laws across 60 frozen relations and correctly oriented 39 of 40 directional laws, whereas lexical controls were near chance. Bidirectional interventions shifted answer probabilities toward or away from the physically appropriate outcome across all 12 matched cases, while counterfactual state patches transferred opposing decision signals across mechanisms and answer formats. Physical relationships were therefore more visible in controlled state changes than in absolute states alone.
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Materials Science
Thickness-dependent crack suppression and wrinkle formation in freestanding BaTiO3 membranes
Rajesh Mandal, Ajay Kumar and Nini Pryds
Freestanding ferroelectric
oxide membranes offer a promising route toward silicon-integrated low-power electronic and
memory devices, but reproducible membrane quality remains challenging, particularly in ultrathin BaTiO3 (BTO), where cracking and wrinkling hinder integration. Here, we show that crack and wrinkle formation in released BaTiO3 membranes can be tuned by jointly controlling
oxide thickness and
polymer support thickness. Reducing the BaTiO3 thickness from 15 nm to 5 nm suppresses large-area, optically visible cracking across the analysed regions, but promotes dense nanoscale wrinkling, revealing a trade-off between fracture mitigation and morphological instability. In 10 nm BaTiO3 membranes,
polymer support thickness further modulates wrinkling, with an intermediate thickness reducing wrinkle density. Piezoresponse force microscopy reveals time-dependent
evolution of written contrast after release, indicating that apparent ferroelectric response is influenced by polarization switching, post-release morphology, interfacial contact, charge screening, and strain relaxation. These results establish processing guidelines for integrating freestanding ferroelectrics into future devices.
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Materials Science
Exploring Multifunctionality in MgO-Based Magnetic Tunnel Junctions with Coexisting Magnetoresistance and Memristive Properties
Alejandro Schulman, Elvira Paz, Tim Böhnert et al. (+2 more)
Magnetic tunnel junctions (MTJs) and memristors are two key emerging nanotechnologies that attracted significant interest for potential applications at the forefront of the digital revolution, including sensing, data storage, and non-conventional computation. The co-integration of these phenomena into a single multifunctional device is an important step toward harnessing the re-programmability of memristive systems with the high yield and varied functionality of MTJs. This study demonstrates the co-existence of magnetoresistance and memristive properties on MgO-based MTJs. These devices show a magnetoresistance with a linear response as a function of a
magnetic field and no hysteresis, which are the requirements for good
magnetic field sensors, as well as demonstrating a non-volatile and quasi-analogue memristive behavior as a function of an applied electrical field down to nanosecond pulses. Furthermore, by doping the
oxide barrier, the memristive power consumption is lowered by 20% giving the multi-functionality of the devices a promising scalability potential. This study also shows that, memristive switching can be reversibly used to completely suppress and recover the spintronic functionalities. These results can pave the way for a seamless co-integration of memristors and spintronic devices in complex reprogrammable
circuits addressing applications such as reprogrammable multifunctional field sensor arrays and neuromorphic computing.
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All authors Alejandro Schulman, Elvira Paz, Tim Böhnert, Alex Steven Jenkins, Ricardo Ferreira
Disordered Systems and Neural Networks
Vanishing spin stiffness in weakly disordered two-dimensional Heisenberg ferromagnets
Jacopo Niedda, Aldo Coraggio, Giacomo Bracci-Testasecca et al. (+1 more)
We show that a small fraction of
antiferromagnetic bonds qualitatively alters the long-wavelength dynamics of two-dimensional Heisenberg ferromagnets. Although the classical ground state remains magnetized, weak bond frustration generates logarithmically correlated spatial fluctuations of the local
spin stiffness, despite the microscopic disorder being short ranged. A replica field theory calculation shows that the effective disorder strength grows under coarse graining, while the
spin stiffness decreases, yielding anomalously soft
magnons with a scale-dependent dynamical exponent $z > 2$. Numerical diagonalization of the semiclassical
spin-wave
Hamiltonian confirms the anomalous low-energy scaling. The flow is toward an infinite-disorder, zero stiffness regime.
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All authors Jacopo Niedda, Aldo Coraggio, Giacomo Bracci-Testasecca, Antonello Scardicchio
Statistical Mechanics
Motility destabilizes an absorbing-state flock
Narayan Dutt Sharma, Subroto Mukerjee, Chandan Dasgupta et al. (+1 more)
Activity, when it takes the form of motility, is generally seen to promote order in many-body systems. Here we present a one-dimensional
lattice model that, in the non-motile limit, exhibits absorbing
ferromagnetic states. When activity is introduced through biased motility, these absorbing state are destabilised and the system instead undergoes a transition from an ordered flock to a disordered state as the
alignment strength is decreased. A finite-size scaling analysis of physical quantities reveals a continuous transition with critical exponents satisfying the hyperscaling relation in one dimension, providing quantitative evidence for the activity-induced disorder.
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All authors Narayan Dutt Sharma, Subroto Mukerjee, Chandan Dasgupta, Sriram Ramaswamy
Materials Science
Huge hole injection in tungsten dichalcogenide heterostructures without electric gating: a DFT study
Dawid Ciszewski and Wojciech Grochala
Van der Waals
heterostructures based on transition metal dichalcogenides, TMDs, provide a versatile platform for tailoring electronic properties through interlayer charge transfer, CT. Precise control of CT is essential because it directly determines the electronic structure and carrier concentration in atomically thin materials. Recently, the concept of a chemical capacitor has been proposed as a route to achieving exceptionally high carrier densities through CT across insulating separator layers. Here, we extend this concept to van der Waals
heterostructures by investigating TMD hBN OX, oxidizer, systems using density functional theory, DFT. Following the screening of candidate TMDs and electron acceptors, XeF2 and KrF2 were identified as suitable acceptors exhibiting type III broken gap band
alignment with WS2 and WSe2, respectively. Periodic DFT calculations of large supercells reveal CT corresponding to hole concentrations of up to 0.23 h+ and 0.35 h+ per W atom in WS2 hBN XeF2 and WSe2 hBN KrF2
heterostructures, respectively. The resulting charge redistribution demonstrates that noble gas fluorides provide an efficient route for noncontact engineering of carrier density in TMD
heterostructures, offering a new strategy for tuning correlated electronic phases in two dimensional materials.
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Strongly Correlated Electrons
How to measure loop currents in scanning tunneling microscopy
Victoire Morisseau, Luke C. Rhodes, Peter Wahl et al. (+1 more)
The emergence of loop current phases, where spontaneous loops of orbital currents give rise to a weak local
magnetic moments, has been proposed to exist in a number of
quantum materials based on measurements that pick up weak signatures of time reversal
symmetry breaking or small
magnetic moment order. The most prominent example is as an explanation of the pseudogap phase on the underdoped side of the phase diagram of the high-temperature cuprate
superconductors, but more recently, it has been proposed to occur in Kagome materials and at the surface layer of Sr$_2$RuO$_4$. Experimental results have, however, been inconclusive so far, some detecting signatures that can be understood as emerging due to loop current phases, whilst others have not detected any significant proof. One of the techniques that should be able to pick up local signatures of loop current orders is low temperature scanning tunneling microscopy and spectroscopy (STM/STS), however firm predictions of how to detect them are missing. Here, we provide specific predictions for how loop current orders in a square
lattice can be seen in spectroscopic maps, using models of the cuprate high-temperature
superconductors and of the surface layer of Sr$_2$RuO$_4$. We find that, besides lifting degeneracies at the specific ordering vector of the loop current order, a finite
spin polarisation emerges when
spin-orbit coupling is present, signatures of which can be detected in
spin-polarised STM.
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All authors Victoire Morisseau, Luke C. Rhodes, Peter Wahl, Carolina A. Marques
Mesoscale and Nanoscale Physics
Spin-wave softening across the uniform-to-stripe domain transition in iron garnet film
Titiksha Srivastava, Victor Leroy, Nessrine Benaziz et al. (+6 more)
Spin-wave spectra across transitions between uniform and textured phases can offer deep insight into both
symmetry-breaking physics and self-assembled magnonic bands. However, experiments require a material platform that combines low damping, well-defined textures, and spectroscopic access. Here, we study a Bi-doped iron-garnet film with perpendicular
magnetic anisotropy (PMA), which undergoes a uniform-to-stripe-domain transition as a function of in-plane
magnetic field. Real-space imaging by
magnetic force microscopy reveals field-reorientable stripe domains aligned with the in-plane field, while reciprocal-space measurements using thermal microfocused Brillouin light scattering ($\mu$-BLS) reveal the softening of a low-frequency
spin-wave branch near the transition and the appearance of additional modes in the stripe-domain state. Calculated dispersion relations identify finite-$k$ softening in the Damon-Eshbach geometry ($k \perp M$), with the corresponding wavelength matching the stripe periodicity at the transition. In addition, a $\mu$-BLS spectral model reproduces the measured mode frequencies and relative intensities at selected fixed fields. Micromagnetic simulations capture the field-driven formation of the stripe state and reproduce the experimental thermal $\mu$-BLS spectra. Our findings establish BiYIG with PMA as a model low-damping platform for studying
spin-wave freezing, stripe-domain modes, and reconfigurable magnonic band structures.
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All authors Titiksha Srivastava, Victor Leroy, Nessrine Benaziz, Nathaniel Findling, Ludovic Largeau, Jamal Ben Youssef, Jean-Paul Adam, Thibaut Devolder, Joo-Von Kim