Materials Science
AutoMOOSE: Use Case and Logical Views of Agentic Phase-Field Simulation Software
Sukriti Manna, Henry Chan and Subramanian Sankaranarayanan
AutoMOOSE is an agentic software framework that converts a natural-
language request into an executed, screened, and interpreted MOOSE phase-field simulation. Here, we deploy AutoMOOSE as a agentic software, complementing our prior work which focused on development of the agentic tool. We describe our software framework and architecture through Use Case and logical views of the 1+5 architectural-views model, covering its user roles, component structure, six-
agent pipeline, physics plugin layer, Model Context Protocol interface, and screening/falsification/recovery loop. Our architecture separates physical falsification from automatic repair, so corrected simulations remain inspectable and must be re-admitted before acceptance. We focus on software design, extensibility, interoperability, and reuse of the AutoMoose framework for broad utilization in multiphysics materials design problems.
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Materials Science · Cross-listed from cond-mat.soft
A molecular perspective on the yield and flow of polymer glasses: The role of enhanced segmental dynamics during active deformation
M.D. Ediger and Kelly Hebert
The mechanical properties of
polymer glasses are often critical in determining the best material for a particular application. Extremely stiff materials (high modulus) may be important for some applications while avoiding catastrophic failure due to fracture (high toughness) may be more important for others. The mechanical properties of a
polymer glass will depend upon both molecular structure and many experimental variables, including temperature and the mode of deformation (tension, compression, or shear). In this chapter we discuss the mechanical response of
polymer glasses from a molecular perspective. In particular, we consider how deformation changes the rate at which
polymer segments rearrange and how this in turn influences the mechanical response of the material. It will be shown that this focus on the changes in dynamics provides an understanding of many important features of
polymer glass deformation. Of course, it is also true that the structure of a
polymer glass must be altered by nonlinear deformation. Although not a major focus, we will make some comments about these structural changes at the end of this chapter.
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Materials Science · Cross-listed from cond-mat.soft
Highly organized smectic-like packing in vapor-deposited glasses of a liquid crystal
Ankit Gujral, Jaritza Gomez, Jing Jiang et al. (+6 more)
Glasses of a model smectic
liquid crystal-forming molecule, itraconazole, were prepared by vapor deposition onto substrates with temperatures ranging from Tsubstrate = 0.78 Tg to 1.02 Tg, where Tg = 330 K is the glass transition temperature. The films were characterized using x-ray scattering techniques. For Tsubstrate near and below Tg, glasses with layered smectic-like structures can be prepared and the layer spacing can be tuned by 16% through choice of Tsubstrate. Remarkably, glasses prepared with Tsubstrate above Tg exhibit much higher structural organization than a thermally annealed film. These results are explained by a mechanism based upon preferred molecular orientation and enhanced molecular motion at the free surface, indicating that molecular organization in the glass is independent of the anchoring preferred at the substrate. These results suggest new strategies of optimizing molecular packing within active layers of organic electronic and optoelectronic devices.
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All authors Ankit Gujral, Jaritza Gomez, Jing Jiang, Chengbin Huang, Kathryn A. OHara, Michael F. Toney, Michael L. Chabinyc, Lian Yu, M.D. Ediger
Materials Science · Cross-listed from cond-mat.soft
Reversing strain deformations probe mechanisms for enhanced segmental mobility of polymer glasses
Kelly Hebert and M.D. Ediger
Optical probe reorientation measurements were performed to monitor changes in segmental dynamics resulting from the nonlinear deformation of a
polymer glass. Segmental dynamics were monitored in a poly(methyl methacrylate) glass near Tg before and after a series of reversing deformations in which the sample was extended at constant strain rate and then allowed to retract back to zero stress at constant strain rate. Evidence of a rejuvenation mechanism, as quantified by a departure of the segmental dynamics from the quiescent aging dynamics after the reversing deformation, is observed for deformations which reach 60% of the yield strain or greater. By this measure, a saturation of the rejuvenation mechanism is not observed until at least five times the yield strain. For comparison, purely mechanical measurements of rejuvenation, based upon the reduction of the yield stress in a subsequent deformation, were also performed. These purely mechanical experiments show broad qualitative agreement with the probe reorientation experiments, but quantitatively differ in the pre-yield regime. The results are discussed in the context of recent theoretical approaches and simulations which provide a molecular-level description of
polymer glass deformation.
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Materials Science
Interplay of nonrelativistic and relativistic spin splittings in altermagnets
Daegeun Jo, Peter M. Oppeneer and Mohsen Yarmohammadi
Despite their compensated
magnetic moments, altermagnets (AMs) exhibit nonrelativistic
spin splitting (NRSS) that offers routes to spintronic functionality without relying on relativistic
spin-orbit coupling. However, how NRSS influences relativistic phenomena remains largely unexplored. Here we show that NRSS plays a crucial role in reshaping the Rashba effect in AMs with broken inversion
symmetry. Using a tight-binding model, we demonstrate that Rashba
spin splitting, whose magnitude is typically limited by the strength of
spin-orbit coupling, is governed by NRSS energy scales. The resulting Rashba bands combined with NRSS generate anomalously large charge-to-
spin conversion with a Néel-vector-tunable
spin polarization. First-principles calculations for the noncentrosymmetric AM GdAlSi corroborate the emergence of these effects in a real system. Our results reveal the interplay between nonrelativistic and relativistic effects in AMs and identify them as fertile platforms for
spin-orbitronic applications.
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Materials Science
Revealing the Role of Confined Molecular H$_2$ in the Passivation of Defective Silicon Using First-Principles Simulations
Hania Azzam, Tobias Binninger, Benedikt Fischer et al. (+2 more)
The passivation of silicon dangling bonds by hydrogen is a crucial requirement for silicon-based optoelectronic technology, especially for solar
cells. Recent experiments on intense light soaking of silicon heterojunction solar
cells unveiled interesting dynamical aspects of hydrogen passivation that are linked to Si-H bond breaking and repassivation. These processes take place predominantly in porous regions near the amorphous/crystalline interface, where hydrogen can exist in molecular form. This work addresses the question of whether molecular H$_2$ directly participates in Si-H depassivation and repassivation. Using density functional theory, we calculate and compare formation energies of point defects, multivacancy cavities and the Si(100) surface to identify relevant passivated and depassivated states. Furthermore, we employ nudged elastic band calculations to determine the activation barriers of the corresponding pathways. We find that sufficient local free volume enables a direct double-H pathway for depassivation through the formation of confined molecular H$_2$. Despite involving the breaking of two Si-H bonds, the double-H process can be energetically and kinetically competitive with the single-H process and can exhibit a reverse repassivation barrier as low as $0.15\,$eV under p-type conditions. These findings provide a plausible atomistic explanation for passivation recovery during light soaking and illuminated annealing in porous regions near amorphous/crystalline silicon interfaces.
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All authors Hania Azzam, Tobias Binninger, Benedikt Fischer, Uwe Rau, Michael Eikerling
Materials Science · Cross-listed from physics.chem-ph
Real-time ESR tracking for sub-micron 3D magnetic mapping with VB- quantum sensors in hexagonal boron nitride
Jefferson A. O. Galindo, Edwin D. C. Sanchez, Cecília L. A. V. Campos et al. (+6 more)
The discovery of
spin-dependent luminescent properties of negatively charged boron-vacancy centers ($V^-_B$) in hexagonal boron nitride (hBN) enabled a new platform for
quantum sensing with van der Waals materials. Particularly, the possibility of performing optically detected
magnetic resonance (ODMR) for determining the electron
spin resonance (ESR) frequencies of hBN color centers became a strong tool for
quantum sensing of
magnetic fields with submicrometric resolution. However, due to low ODMR contrast, current techniques proposed for mapping DC
magnetic fields require hours of integration to obtain a
magnetic image of a micron-sized region. In this work, we report the implementation of a frequency-tracking approach for real-time monitoring of ESR frequencies of localized $V^-_B$ centers in hBN. With this technique,
magnetic field monitoring was used to map the field pattern generated by a micron-sized conical
magnetic tip in only a few minutes. By controlling the
magnetic sample's position relative to the
quantum sensor, three-dimensional
magnetic mapping of the field was achieved with diffraction-limited resolution and shot-noise-limited sensitivity of 54 $\mu$T$/\sqrt{\text{Hz}}$.
Magnetic field gradients of 3.6 $\pm$ 0.2 $\mu$T/nm were measured with our system, in which a maximum detected field rate of 6 mT/s was achieved. The results of this study establish
spin resonance frequency-tracking as a viable technique and fast method for minute-scale
magnetic imaging, reducing acquisition times by at least one order of magnitude if compared to conventional techniques.
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All authors Jefferson A. O. Galindo, Edwin D. C. Sanchez, Cecília L. A. V. Campos, Allison R. Pessoa, Hugo A. D. Correia, José D. M. de Lima, Klaus Krambrock, Leonardo de S. Menezes, Anderson M. Amaral
Materials Science
Carrier Capture at Defects from Finite-Temperature Lattice Dynamics
Menglin Huang, Shanshan Wang and Shiyou Chen
Defect-assisted carrier capture is commonly described within nonradiative multiphonon (NMP) theory using normal modes of the
equilibrium defect structure. This description becomes inadequate when finite-temperature
lattice fluctuations explore configurations that cannot be represented by a fixed normal-mode basis. Here, we present a trajectory-based method for calculating carrier capture rate from first principles, which allows
lattice relaxation and electron–
lattice coupling
matrix element to be reconstructed directly from correlation functions of finite-temperature
lattice dynamics. For hole capture at C$_\mathrm{N}$ in GaN within harmonic regime, the method reproduces static NMP results including mode mixing and agrees with experiment. For oxygen vacancy in SiO$_2$, by contrast, the thermally sampled potential energy surface is substantially softer than the zero-temperature normal-mode harmonic expansion, strongly modifying the
lattice relaxation and electron–
lattice coupling, and producing pronounced changes in both the capture coefficient and its temperature dependence. These results establish the finite-temperature configurational ensemble, rather than
phonon occupations alone, as an essential ingredient of defect-assisted carrier capture.
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Materials Science
An LLM agent for end-to-end computational materials discovery
Chen Yuntong, Huang Ju, Liu Yu et al. (+6 more)
The coordination of multi-scale tasks is an effective strategy for computational materials discovery, yet the repeated application of diverse
algorithms and tools renders it challenging. We report MAESTRO, a large
language model (LLM)
agent system capable of executing the entire screening pipeline for metal-organic frameworks (MOFs). It processes a large body of MOF literature, links relevant publications to their
crystal structures, and curates the results into a computation-ready database, which is then screened through a strategy of progressively increasing computational cost. The promising candidates identified for separation under wet flue gas conditions all originate from unrelated studies. By connecting the heterogeneous stages of computational materials discovery, the LLM-based
agents of MAESTRO can operate across application domains and uncover high-performance materials that conventional screening approaches would be unlikely to consider.
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All authors Chen Yuntong, Huang Ju, Liu Yu, Zhao Dan, Sun Mingqi, Ju Chentian, Liu Yanbing, Huang Lijiang, Zhao Guobin
Materials Science
Three-dimensional imaging of oxygen dopant distribution in Sr$_2$CuO$_{3+\delta}$ by electron ptychography
Hongbin Yang, Jinkwon Kim, Desheng Ma et al. (+3 more)
Oxygen dopants play a critical role in tuning the properties of cuprate
superconductors, yet it is challenging to visualize them at the atomic scale. Here, we use multislice electron ptychography to directly image oxygen dopants in a Sr2CuO3+delta film. We observe oxygen dopants at interstitial sites between the Cu-O chains, with a strong preference for clustering in tensile-strained regions, which are often associated with dislocations and interfacial steps. These findings indicate that the oxygen dopant distribution in cuprates is not random but rather sensitive to strain field, suggesting strain as a doping tuning parameter.
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All authors Hongbin Yang, Jinkwon Kim, Desheng Ma, Dasol Yoon, Darrell G. Schlom, David A. Muller
Materials Science
A Unified Theoretical Framework for Photoemission and Its Inverse: Reciprocity, Spin, and Photon Polarization
Frank O. Schumann and Jürgen Henk
We present a unified theoretical framework for
spin- and angle-resolved photoemission spectroscopy (SARPES) and its inverse process (SARIPES), treating both on an equal footing. The formulation is based on a response tensor that encodes the reciprocity between the two processes. We show that polarization
tomography within SARPES calculations provides a systematic route for reconstructing the tensor elements. The number of independent components is significantly reduced by
symmetry constraints, which in turn allows for explicit expressions describing
spin-reversal processes and intensity modulations. The formalism is illustrated for the W(110) surface. The resulting framework provides a
symmetry-adapted description of
spin-dependent optical transitions at surfaces and enables the direct prediction of SARIPES intensities from SARPES calculations.
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Materials Science
Quantum Dissipative Paraelectricity
A. Cano
Whether a
quantum system with a double-well effective potential undergoes spontaneous
symmetry breaking depends not only on the potential landscape but also on the kinetics and the coupling with additional degrees of freedom. Here we introduce a quasi-exactly solvable model to study this problem in the context of ferroelectrics, with results that apply to a broad class of
quantum phase transitions. Exploiting the analytical solutions, we provide a strict definition of the
quantum paraelectric regime and identify a distinct
quantum ferroelectric regime in which
symmetry breaking can be realized without tunneling features. We then show that explicit
symmetry breaking cannot be inferred from the order-parameter
Hamiltonian alone, but requires additional couplings. This leads us to identify a regime of
quantum dissipative paraelectricity, in which observable
symmetry breaking is suppressed during the
evolution toward the ground state, even when the double-well structure dominates over zero-point
quantum fluctuations.
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Materials Science
Effects of the surface on double surface Fermi arcs in a realistic tight-binding model of Na$_3$Bi (100)
Vasilios K. Passias and Lucas K. Wagner
Na$_3$Bi is a topological Dirac semimetal (TDSM) that can support double surface Fermi arcs (DSFAs), which are important for its material classification and their potential use in spintronic devices. However, it is unclear how the surfaces affect realistic Na$_3$Bi (100) systems. To investigate the effects of diverse surfaces on DSFAs, we consider first principles derived tight-binding models of two Na$_3$Bi (100) terminations. On the stoichiometric termination, we find DSFAs as expected. On the non-stoichiometric structure there are DSFAs on one termination and two loops that retain many of the properties of DSFAs. Thus, the local properties such as
spin momentum locking and hybridization with the Dirac points appear to be more robust than their global connectivity. That is, the surface can reshape the arc fingerprint without destroying the arc-like physics.
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Materials Science · Cross-listed from cond-mat.str-el
Pressure-tuning of electronic structure of CeTe3 probed by femtosecond collective mode spectroscopy
Chandra V. Kotyada, Priyanka Yogi, Amon P. Lanz et al. (+8 more)
We use femtosecond optical spectroscopy to study the
evolution of coherent order-parameter dynamics in the prototypical charge-density-wave (CDW) system CeTe3 under hydrostatic pressure. The CDW transition temperature decreases from approximately 570 K at ambient pressure to near room temperature at approximately 6 GPa. The pressure dependence of the order-parameter recovery dynamics indicates enhanced electron-
phonon coupling with increasing pressure, implying that CDW suppression is driven predominantly by the reduction in Fermi-surface nesting. Above 7 GPa, no evidence of CDW order is observed down to cryogenic temperatures. Concurrently, the relaxation dynamics exhibit significant slowing down at low-temperatures, consistent with emerging heavy-electron behaviour due to pressure-enhanced hybridization between localized Ce 4f levels and itinerant carriers.
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All authors Chandra V. Kotyada, Priyanka Yogi, Amon P. Lanz, Rolf Heid, Jonas Tauch, Manuel Obergfell, Hanjo Schaefer, Paula Giraldo-Gallo, Ian R. Fisher, Alexej Pashkin, Jure Demsar
Materials Science
Anomalous behavior of native point defects in C2-ordered antiferromagnet $\alpha$-MnO$_2$
Archana Sharma and Brahmananda Chakraborty
$\alpha$-MnO$_2$ is an emerging material for electronic, optoelectronic, and energy applications, owing to its structural flexibility and defect-driven functionality. During synthesis of $\alpha$-MnO$_2$, native oxygen vacancies readily form and are typically compensated by foreign dopants. A thorough understanding of intrinsic defects is therefore essential for enabling controlled extrinsic doping and optimizing material performance. Using density functional approach, we investigate the structural, electronic,
magnetic, and optical properties of the ground state C2-type antiferromagnetic $\alpha$-MnO$_2$ in the presence of native point defects, including interstitials, vacancies, and antisites. We compute their thermodynamic stability, incorporating electrostatic corrections to eliminate spurious long-range interactions. Mn interstitial (Mn$_\text{i}$) and Mn antisite O (Mn$_\text{O}$) introduce shallow donor levels, whereas O-vacancy (V$_\text{O}$) exhibit amphoteric behavior and act as compensating centers. The calculated defect formation energies reveal pronounced competition between donor- and acceptor-type native defects, leading to strong intrinsic defect compensation under both Mn-rich and O-rich growth conditions. Mn vacancy (V$_\text{Mn}$) remains ionized across the band gap and behaves as a shallow acceptor, suggesting its potential role under suitable non-
equilibrium growth conditions, whereas O antisite Mn (O$_\text{Mn}$) forms deep acceptor levels. BSE@G$_0$$W_0$ calculations reveal a strongly anisotropic optical response in stoichiometric $\alpha$-MnO$_2$, while native point defects introduce pronounced sub-gap excitations and enhanced dielectric screening, with vacancies producing the largest effect.
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Materials Science
Amorphous and Nanocrystalline Topological Semimetal YPtBi/W/CoFeB Heterostructures for BEOL-Compatible Spin-Orbit Torque Devices
Quang Le, Brian R. York, Cherngye Hwang et al. (+17 more)
Spin-orbit torque (SOT) devices require
spin-source materials that combine efficient charge-to-
spin conversion with back-end-of-line (BEOL) thermal compatibility. Here, we show that YPtBi/W/CoFeB
heterostructures deposited directly on Si/SiOx remain predominantly amorphous or weakly nanocrystalline from room temperature to 400 {\deg}C while preserving a large effective damping-like SOT response. Anomalous Hall and harmonic Hall measurements, together with X-ray diffraction, cross-sectional transmission electron microscopy, X-ray reflectivity, and electron energy-loss spectroscopy, show that the response does not correlate with bulk crystallization of YPtBi. Instead, the interfacial analysis indicates that the strongest trend of the
spin Hall angle is associated with the chemistry of the upper YPtBi/W boundary: the effective SOT response tracks the integrated W concentration at that YPtBi surface. Meanwhile, a two-
spin source analysis shows that the Pt-W-rich interlayer provides only a small positive correction, insufficient to explain the large negative effective
spin Hall angle by itself. The dominant control variable is therefore inferred to be the incorporation of W into the upper YPtBi interface, which plausibly modifies the local electronic structure of YPtBi and amplifies the stack-level response. These results provide a more physically constrained interpretation of the stack behavior and identify a BEOL-compatible route to disordered topological
spin-source layers for scaled SOT
memory and compute-in-
memory hardware.
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All authors Quang Le, Brian R. York, Cherngye Hwang, Xiaoyong Liu, Tsann Lin, Xiaoyu Xu, Yudi Wang, Jia Li, Mazin Osman, Katherine Le, Maher Osman, Son Le, Lei Xu, Maki Maeda, Tuo Fan, Yu Tao, Hisashi Takano, Sho Kagami, Ohiro Fujie, Pham Nam Hai
Materials Science · Cross-listed from cond-mat.soft
Role of topology in scaling laws for studying mechanics in open-porous solids: Moving beyond classical Gibson-Ashby scaling
Ameya Rege
The elastic modulus of porous materials is commonly described using power-law scaling relations with relative density, where the scaling exponent is often interpreted in terms of the underlying deformation mechanism. However, in highly disordered porous networks, changes in density are generally accompanied by changes in network
topology, which can substantially modify the apparent scaling behavior. In this paper, we propose a
topology-informed framework that separates the intrinsic mechanical contribution from the effects of network structure. Three representative topological descriptors are considered: the mean coordination number, the fraction of the load-bearing backbone, and the tortuosity of the load paths. For each case, the corresponding density-dependent contribution to the apparent modulus-scaling exponent is derived and analyzed. The results show that variations in connectivity, mechanical participation of the solid phase, and load-path efficiency can all lead to apparent scaling exponents exceeding the intrinsic exponent associated with the local deformation mechanism. These effects are particularly pronounced at low relative densities, where network
topology evolves most strongly. The framework provides a physically interpretable basis for understanding anomalous modulus-density scaling in disordered porous materials and highlights the need to consider
topology explicitly alongside relative density.
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Materials Science · Cross-listed from physics.optics
Oscillator-driven broadband femtosecond transient microspectroscopy with supercontinuum probes generated in a photonic crystal fiber
Rikuto Fukuda, Kyosuke Kishihata, Ryo Man-nami et al. (+4 more)
We present an oscillator-driven femtosecond transient microspectroscopy system based on supercontinuum generation in a photonic
crystal fiber (PCF). The system operates at 80 MHz without pulse amplification, enabling high-sensitivity measurements with a detection sensitivity better than $10^{-4}$ while using low pulse energies suitable for microspectroscopy. Optimization of the PCF length ($\leq 50$ mm) suppresses dispersion-induced chirp, achieving nearly uniform temporal resolution below 100 fs across 450-900 nm. The high-repetition-rate operation allows rapid spectral acquisition and efficient noise reduction. The developed system provides micrometer-scale spatial resolution and supports both reflection and transmission configurations. Ultrafast carrier dynamics in multilayer and monolayer MoS$_2$ are successfully resolved, including spatially dependent relaxation within a single monolayer flake. These results demonstrate a versatile platform for probing local ultrafast dynamics in low-dimensional materials.
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All authors Rikuto Fukuda, Kyosuke Kishihata, Ryo Man-nami, Hiroaki Atsumi, Borja Cirera, DaeGwi Kim, Masahiro Shibuta
Materials Science
A low-temperature setup for lock-in technique based dynamic magnetoelectric coupling measurements
Balwant Singh Chauhan, Priyanka Sharma, Rie Y. Umetsu et al. (+1 more)
Magnetoelectric (ME) phenomena in emerging material classes, such as two-dimensional van der Waals (vdW) magnets and Single-Molecule Magnets (SMMs), hold immense promise for next-generation cryogenic
memory and
quantum technologies. However, ME coupling in these systems predominantly manifests at low temperatures, making a sensitive, cryo-compatible ME characterization techniques critical. To address this requirement, we report the design, validation, and performance of a custom closed-cycle refrigerator-based setup for dynamic lock-in ME coupling measurements across 20-300 K under dc
magnetic fields up to 7.5 kOe. Key design considerations for mitigating parasitic inductive background signals are also presented. The setup was validated on a CoFe2O4-BaTiO3 (CFO-BTO) particulate composite, reproducing the characteristic room-temperature butterfly ME loop with a maximum ME coefficient value of 0.23 mV/cm-Oe at ~ 3 kOe. Temperature-dependent measurements resolved ME anomalies at ~ 200 K and 280 K, coinciding with the rhombohedral-orthorhombic and orthorhombic-tetragonal structural transitions of BaTiO3, and were corroborated by simultaneous dielectric measurements on the same sample without cryostat reconfiguration. The instrument enables reliable ME and dielectric characterization down to 20 K, making it well suited for probing weak magnetoelectric coupling and phase transitions in multiferroic composites and
quantum materials.
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All authors Balwant Singh Chauhan, Priyanka Sharma, Rie Y. Umetsu, Ratnamala Chatterjee
Materials Science
Tuning of Photoexcited Electron Dynamics at Monolayer h-BN/Metal Interfaces by Corrugation
Masahiro Shibuta, Maximilian Schaal, Marco Gruenewald et al. (+4 more)
Atomic-scale corrugation in two-dimensional materials can modify interfacial electronic coupling, yet its influence on ultrafast carrier relaxation remains poorly established. Here, we compare image potential states (IPS) at monolayer h-BN/Ir(111) and h-BN/Pt(111) interfaces using structural characterization and time-resolved two-
photon photoemission spectroscopy. Consistent with literature, h-BN is strongly corrugated on Ir(111) but comparatively flat on Pt(111). The first (n = 1) and second (n = 2) IPS appears at similar energies on both substrates, whereas their relaxation dynamics differ markedly. On h-BN/Ir(111), the IPS decay is response-limited (<20 fs), while h-BN/Pt(111) exhibits lifetimes of 56 fs (n = 1) and 75 fs (n = 2). The lifetime contrast is most consistently explained by corrugation-enhanced overlap of the IPS wavefunction with the metal substrate, which accelerates electron decay. These results indicate that atomic-scale corrugation is an effective physical parameter for tuning ultrafast electron dynamics at two-dimensional material and metal interfaces.
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All authors Masahiro Shibuta, Maximilian Schaal, Marco Gruenewald, Jonas Brandhoff, Felix Otto, Roman Forker, Torsten Fritz
Materials Science
Building atomistic models of heterointerfaces with optimal transport
Yuxuan Tang and Keith T. Butler
Heterogeneous interfaces underpin technologies from microelectronics to energy conversion and storage, but their configurational complexity precludes exhaustive first-principles screening of interface registries. Although data-driven approaches can alleviate this burden, they remain limited by sparse interface
datasets. Here, we introduce an energy-independent workflow that represents coherent interfaces as attributed graphs, quantifies their similarity to parent bulk environments using the fused Gromov-Wasserstein (FGW) distance, and couples this metric with
Bayesian optimization over the in-plane registry space. We assess the approach for KI/NaCl, GaP/GaAs and GaN/$\mathrm{Al_{2}O_{3}}$ interfaces spanning ionic, covalent and mixed-bonding regimes, using hierarchical validation with MACE and density functional theory (DFT). Comparison with single-point energy landscapes shows that the FGW distance captures registry-dependent periodicity, while interfaces exhibit deviations between structural and energetic extrema, reflecting additional chemistry-specific contributions. Furthermore, FGW distances show an overall association with relaxed energies. Under limited screening budgets, FGW-guided registry selection consistently outperforms random search and is more robust across interface systems than selection guided by pretrained MACE energies. The workflow converts the qualitative notion of bulk-like continuity into a quantitative prescreening criterion, enabling efficient registry exploration and providing physically informed candidate structures for materials discovery workflows.
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Materials Science · Cross-listed from cond-mat.str-el
Tilted $p$-wave magnet candidate CeNiAsO
Zhuo Wang, Zheng Liu, Shuo Zou et al. (+17 more)
The unexpectedly small ordered moments of CeNiAsO, a candidate for correlated $p$-wave magnet, have posed a serious challenge to the precise determination of its
magnetic structure, hindering the understanding of its fundamental properties. By leveraging the high sensitivity to local internal fields, our $^{75}$As nuclear quadrupole /
magnetic resonance experiments reveal a commensurate antiferromagnetic order with a small out-of-plane moment $m_z\approx0.05$ $\mu_{\mathrm{B}}$. This tilted
magnetic configuration not only rotates the
spin polarization axis away from the crystallographic $\mathbf{c}$-axis, but also enhances the non-relativistic
spin splitting. We refer to this rare paradigm as a \textit{tilted $p$-wave magnet}.
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All authors Zhuo Wang, Zheng Liu, Shuo Zou, Hua-Xun Li, Jin-Xin Hu, Zhuolun Qiu, Ze Wang, Jiamin Gong, Lucheng Wei, Kangjian Luo, Hai Zeng, Meng Zhang, Chao Dong, Chuanyin Xi, Junfeng Wang, Jiakun Fang, Xiaotao Han, Guang-Han Cao, Liang Li, Yongkang Luo
Materials Science
Controlling catalyst agglomeration in high-density unordered III-V nanowire growth using Au colloid solutions
Chris Yannic Bohlemann, Pavithira Manoharan, Helene Reichel et al. (+4 more)
III-V
semiconductor nanowires (NWs) are a promising platform for optoelectronic and photoelectrochemical applications, where device performance strongly depends on NW density and spatial arrangement. While ordered arrays provide precise control, their fabrication requires complex and costly lithographic techniques. Unordered growth offers a scalable alternative but is limited by insufficient control over catalyst distribution and particle agglomeration. Here, we investigate the density scaling of unordered III-V NW arrays using commercially available Au colloid solutions as catalysts for NW growth via vapor-
liquid-solid growth mode. Repeated deposition cycles yield a near-linear increase in particle density, which is ultimately limited by non-linear agglomeration effects not captured by simple
stochastic models. To address this limitation, a previously established pre-anneal growth concept is transferred from patterned catalyst arrays to randomly deposited Au colloids, thereby suppressing thermally induced coalescence and stabilizing the catalyst distribution. This approach enables up to a tenfold increase in NW density while improving uniformity and vertical yield. The method is demonstrated for colloid diameters between 100 and 200 nm. Overall, this work provides a scalable, lithography-free route toward high-density III-V NW ensembles and offers insight into the role of particle dynamics in colloid-based growth processes.
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All authors Chris Yannic Bohlemann, Pavithira Manoharan, Helene Reichel, Kai Daniel Hanke, Peter Kleinschmidt, Thomas Hannappel, Juliane Koch
Materials Science
Constitutive modelling of open-porous neo-Hookean solids
Ameya Rege
Open-porous materials exhibit pronounced compressibility, nonlinear densification, and power-law scaling of stiffness with density. In this work, we propose a thermodynamically consistent compressible neo-Hookean constitutive model for open-porous solids in which porosity serves as the primary governing variable. The strain-energy density is formulated to couple distortional elasticity of the solid skeleton with a volumetric response governed by deformation-induced porosity
evolution, including a bounded representation of pore collapse. The formulation introduces a minimal set of parameters, namely the initial porosity, intrinsic skeleton moduli, and a scalar parameter controlling the onset of densification. A key feature of the model is a modified volumetric term in which the response is normalised by the current porosity, ensuring a physically consistent transition from a porous to a densified state without artificial stiffening. In the small-strain limit, the model recovers classical linear elasticity with effective moduli that may be chosen either from homogenisation bounds, such as the Hashin-Shtrikman estimates, or from Gibson-Ashby-type power-law scaling to capture
topology-dependent behaviour. At finite strains, the formulation captures the characteristic nonlinear stiffening and convex stress-stretch response associated with progressive pore collapse. The proposed framework thus provides a compact, flexible, and extensible constitutive description that unifies effective-medium consistency with experimentally observed scaling behaviour, and is well suited for finite element implementation and multiscale modelling of highly compressible open-porous materials. The model is finally validated against available experimental data.
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Materials Science
Valley- and Spin-Dependent Electronic and Transport Properties of Two-Dimensional Altermagnetic Titanium-Based Chalcogenide Halides
Ruo-Yu Ning, Zhi-Hua Yan, Jin-Yang Li et al. (+2 more)
Altermagnets (AMs) combine fully compensated magnetization with momentum-dependent
spin splitting, yet intrinsic altermagnetic materials exhibiting exceptional valley characteristics remain scarce. Here, we identify monolayer titanium-based chalcogenide halides, Ti$_2X_2Y$ ($X$ = F, Cl, Br, I; $Y$ = O, S, Se, Te), as a new family of two-dimensional altermagnetic valley materials. These monolayers exhibit robust $d$-wave altermagnetic order, semiconducting band gaps, and pronounced
spin-polarized valley characteristics. We show that uniaxial strain breaks the valley degeneracy, inducing giant valley polarization together with a tunable piezomagnetic response. An in-plane electric field generates noncollinear
spin currents, while
spin–orbit coupling gives rise to the anomalous Hall effect, valley-selective linear dichroism, and the magneto-optical Kerr effect. These findings establish Ti$_2X_2Y$ monolayers as a versatile platform for exploring
spin- and valley-dependent electronic, optical, and transport phenomena in two-dimensional altermagnets.
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All authors Ruo-Yu Ning, Zhi-Hua Yan, Jin-Yang Li, Yong-Kun Wang, Si Li
Materials Science
Mirror Chern insulators in two-dimensional altermagnetic Tc$_2$Cl$_2$O and Tc$_2$Br$_2$O
Rong Wang, Ruo-Yu Ning, Zhi-Hua Yan et al. (+1 more)
The interplay between altermagnetism and crystalline band
topology provides an intriguing avenue for realizing unconventional topological phases with distinctive
spin-dependent properties. Here, based on first-principles calculations and theoretical analysis, we identify monolayer $\mathrm{Tc}_2X_2\mathrm{O}$ ($X$ = Cl, Br) as a family of two-dimensional altermagnetic mirror Chern
insulators. In the absence of
spin–orbit coupling (SOC), both monolayers exhibit robust altermagnetism with mirror-
spin coupling and host two
symmetry-protected Weyl points in each
spin channel near the Fermi level. The Weyl points in opposite
spin channels carry distinct mirror-
symmetry eigenvalues, $m_z=\pm i$. Upon inclusion of SOC, the Weyl points are gapped, and the two mirror sectors acquire opposite Chern numbers, ${\cal {C}}_{+}=1$ and ${\cal {C}}_{-}=-1$, resulting in a nonzero mirror Chern number ${\cal {C}}_m=1$. A low-energy $k\cdot p$ model captures the
symmetry protection of the Weyl points and elucidates their SOC-induced mass gaps and topological character. Furthermore, the resulting mirror Chern insulating phases host helical edge states within the bulk band gap and exhibit a quantized
spin Hall conductivity. Our work establishes a direct connection between altermagnetism and mirror Chern
topology and provides a promising platform for exploring unconventional topological and
spin-dependent phenomena in two-dimensional altermagnetic materials.
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All authors Rong Wang, Ruo-Yu Ning, Zhi-Hua Yan, Si Li
Materials Science · Cross-listed from cond-mat.soft
Cooperative effects of membrane confinement and gelation on PEG crystallization pathway
Masaki Yoshida, Naoya Yanagisawa, Fumiya Kanie et al. (+5 more)
Lipid-coated microscale hydrogels provide confined, hydrated environments in which
polymer phase behavior can differ markedly from that in bulk. Here, we investigate the crystallization pathway of poly(ethylene glycol) (PEG) encapsulated in lipid-coated agarose microgels. Surprisingly, polarized-light microscopy reveals birefringence in the microgels under conditions where PEG remains non-crystalline in the corresponding bulk solution. The birefringence disappears upon heating and spontaneously reappears after further cooling or upon local mechanical stimulation. Infrared microspectroscopy demonstrates that the birefringent microgels contain crystalline PEG, whereas non-birefringent microgels contain PEG in an amorphous-like state, indicating the existence of a metastable precursor prior to crystallization. Furthermore, cooling below the phase-separation temperature produces PEG-rich domains preferentially near the membrane, suggesting that membrane wetting governs the spatial distribution of PEG before crystallization. Together, these results indicate that membrane confinement and agarose gelation cooperatively alter the local hydration environment of PEG, thereby stabilizing an amorphous-like precursor and redirecting the subsequent crystallization pathway. Our findings identify the coupling of membrane wetting and gelation as a key factor governing PEG crystallization in confined soft materials.
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All authors Masaki Yoshida, Naoya Yanagisawa, Fumiya Kanie, Hidemasa Teraoka, Ikki Morichika, Satoshi Ashihara, Tetsuya Hama, Miho Yanagisawa
Materials Science
Interplay of exchange and spin-conserving scattering processes in a ferromagnetic two-sublattice system
Ariyan Tavakoli, Kai Leckron and Hans Christian Schneider
In
magnetic alloys or hybrid systems formed by molecular magnets coupled to a
magnetic substrate, the exchange interaction leads to fast
spin dynamics after excitation. We investigate the electronic charge and
spin dynamics due to the exchange interaction in a two-sublattice system with antiferromagnetic coupling. We employ a simplified model for a ferrimagnetic
alloy as a coupled system of itinerant and localized electron states together with an exchange coupling between the two. For the itinerant system we include electron-electron Coulomb scattering and electron-
phonon scattering. We study numerically the heat-induced ultrafast magnetization dynamics due to the interplay of exchange scattering and
spin-independent scattering processes and discuss different scenarios for the demagnetization and relaxation dynamics of the sublattices. Our results highlight the impact of
spin-conserving electron-electron scattering processes on the exchange-driven
spin dynamics on ultrashort timescales.
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Materials Science · Cross-listed from quant-ph
Physics-guided machine learning for sim-to-real calibration of NV diamond magnetometers
Jonathan Daniel, Martin Y. Kim, Jesse Hernandez et al. (+4 more)
Ensemble nitrogen-vacancy (NV) centers in diamond enable robust vector magnetometry in unshielded environments, yet deployment remains bottlenecked by complex calibration and a reliance on external data references. Conventional statistical machine learning requires an exorbitantly large volume of training data and suffers from severe simulation-to-reality mismatches. To address this, we introduce a physics-guided hybrid machine learning framework that embeds the Zeeman splitting directly into the learning pipeline. Our physics-guided model significantly reduces the average tracking error demonstrating a 372-fold precision improvement over purely statistical baselines. Furthermore, our hybrid architecture pairs a sparse physical measurement with scalable synthetic data generation, seamlessly incorporating real-world hardware non-idealities. When deployed to decode uncalibrated, raw experimental ODMR data, our framework delivers exceptional predictive accuracy for the scalar
magnetic field. This work paves the way toward self-calibrated sensors while establishing a machine learning training method applicable to other data-scarce physical systems
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All authors Jonathan Daniel, Martin Y. Kim, Jesse Hernandez, Emanuel Suarez, Sangwoo Lee, Jinhee Lee, Je-Hyung Kim
Materials Science
Composition-Driven Phase Evolution in Sm-Doped BiFeO3 via Latent-Field Reconstruction of Atomically Resolved STEM Data
Newsha Javanmardi, Christopher T. Nelson, Anna N. Morozovska et al. (+3 more)
Functionalities of ferroelectric materials are governed by the spatial organization and coupling of polarization, strain,
lattice rotation, and structural order accessible via atomically resolved scanning transmission electron microscopy (STEM) images. Quantitative interpretation of atomic-resolution STEM data has conventionally relied on locating atomic columns and converting their fitted coordinates into local structural descriptors. Here, we develop a field-based approach in which atomic-resolution images are represented by spatially varying latent Bragg fields, whose amplitudes and phases provide continuous maps of crystalline order,
lattice displacement, strain, rotation, and mode-specific residual structure. The observed atomically resolved images are decoded from the latent fields. We apply this framework to image series of Sm-substituted BiFeO3 spanning 0-20% Sm and crossing the composition-driven boundary between the R3c ferroelectric phase and the orthorhombic, nonpolar Pnma phase. Conventional atom-resolved parameterization is used as an independent validation, showing that reconstructed Bragg amplitude tracks local atomic-column intensity and that field-derived shear reproduces unit-
cell angular distortions obtained from atom fitting. The combined analysis reveals a systematic
evolution from extended ferroelectric domains at low Sm concentration, through the appearance and growth of localized regions with period-doubled Pnma order at intermediate compositions, to a connected Pnma-dominated state at high Sm content. The period-doubled order is accompanied by enhanced shear and
lattice rotation and by progressive reorganization of the ferroelectric domain structure. These results establish latent-field reconstruction as a physically interpretable complement to atom finding and provide a unified framework for resolving composition-driven phase
evolution in ferroic materials.
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All authors Newsha Javanmardi, Christopher T. Nelson, Anna N. Morozovska, Eugene A. Eliseev, Ichiro Takeuchi, Sergei V. Kalinin