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Physics Condensed Matter Materials Science

cond-mat.mtrl-sci Watch Materials Science

Monday 5 January

Materials Science · Cross-listed from cond-mat.str-el

Emergent Anomalous Hall Effect in the Eu-Based Compound with a Diamond Network: The Centrosymmetric Cubic Antiferromagnet EuTi$_2$Al$_{20}$

Ryuji Higashinaka, Kohsuke Sato, Ryosei Ideura et al. (+2 more)

The centrosymmetric cubic compound EuTi$_2$Al$_{20}$, in which magnetic Eu ions form a diamond network, undergoes an antiferromagnetic transition at T$_N$ = 3.3 K and exhibits metamagnetic transitions at H$_{m1}$ = 1.7 T and H$_{m2}$ = 2.8 T for H || [100] at 1.9 K. Between these fields, the magnetization shows a step-like behavior, defining an intermediate field-induced phase (Phase~II). We investigated the electronic transport in Phase~II and found that both the resistivity and Hall resistivity are markedly enhanced, while remaining nearly field independent within the phase. Phase~II appears for all field directions, although its transport response shows moderate directional dependence. These features differ from the strongly orientation-selective behavior often observed in skyrmion-lattice phases of several 4f-electron compounds, suggesting that Phase II may host a field-induced spin texture with a topological character distinct from that of a conventional skyrmion lattice.
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All authors Ryuji Higashinaka, Kohsuke Sato, Ryosei Ideura, Masahiro Kawamata, Tatsuma D. Matsuda

Materials Science

Anharmonic lattice dynamics study of phonon transport in layered and molecular-crystal indium iodides

Takuma Shiga, Yoshikazu Mizuguchi and Hiroshi Fujihisa

Indium iodides, which adopt layered or molecular-crystal-like arrangements depending on composition, are expected to exhibit low lattice thermal conductivity because of their heavy constituent atoms and weak In-I bonding. In this work, we employed first-principles anharmonic lattice dynamics calculations to systematically investigate phonon transport in indium iodides from particle- and wave-like perspectives. The calculated lattice thermal conductivities of both materials remained below 1 W/m-K over a broad temperature range. Notably, the influence of wave-like phonon transport differed by composition: in InI3, the wave-like contribution became comparable to the particle-like Peierls contribution, whereas it remained negligible in InI. We also investigated the thermal transport properties of the experimentally reported high-pressure phase of InI3. Motivated by experimental indications of stacking faults and partial disorder in indium site occupancy within the rhombohedral phase, we constructed several ordered structural models with different stacking sequences. These stacking sequences exhibited no significant energetic preference and had similar lattice thermal conductivities, suggesting that in-plane thermal transport is largely governed by the vibrational properties of the In2I6 layers themselves rather than by the specific stacking sequence. These findings provide insight into phonon transport in layered and molecular-crystal systems with structural complexity and contribute to a broader understanding of thermal transport mechanisms in layered and molecular-crystal-like materials.
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Materials Science

Charge Hopping Dynamics along a Disordered Chain in Quantum Environments: Comparative Study of Different Rate Kernels

Seogjoo J. Jang and Andres Montoya-Castillo

This work presents a computational study of charge hopping dynamics along a one dimensional chain with Gaussian site energy disorder and linearly coupled quantum bath. Time dependent square displacements are calculated directly from numerical solutions of Pauli master equations, for five different rate kernels: exact Fermi golden rule (FGR) rate expression, stationary phase interpolation (SPI) approximation, semiclassical (SC) approximation, classical Marcus rate expression, and Miller-Abrahams expression. All results demonstrate diffusive behavior in the steady state limit. The results based on the FGR rate expression show that the charge transport in quantum bath can be much more sensitive to the disorder than the prediction from the classical Marcus expression. While the SPI approximation captures this general trend reasonably well, the SC approximation tends to be unreliable at both quantitative and qualitative levels, and becomes even worse than the classical Marcus expression under certain conditions. These results offer useful guidance in the choice of approximate rate kernels for larger scale simulations, and also demonstrate significant but fragile positive effects of quantum environments on the charge hopping dynamics.
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Sunday 4 January

Materials Science

A large-scale nanocrystal database with aligned synthesis and properties enabling generative inverse design

Kai Gu, Yingping Liang, Senliang Peng et al. (+3 more)

The synthesis of nanocrystals has been highly dependent on trial-and-error, due to the complex correlation between synthesis parameters and physicochemical properties. Although deep learning offers a potential methodology to achieve generative inverse design, it is still hindered by the scarcity of high-quality datasets that align nanocrystal synthesis routes with their properties. Here, we present the construction of a large-scale, aligned Nanocrystal Synthesis-Property (NSP) database and demonstrate its capability for generative inverse design. To extract structured synthesis routes and their corresponding product properties from literature, we develop NanoExtractor, a large language model (LLM) enhanced by well-designed augmentation strategies. NanoExtractor is validated against human experts, achieving a weighted average score of 88% on the test set, significantly outperforming chemistry-specialized (3%) and general-purpose LLMs (38%). The resulting NSP database contains nearly 160,000 aligned entries and serves as training data for our NanoDesigner, an LLM for inverse synthesis design. The generative capability of NanoDesigner is validated through the successful design of viable synthesis routes for both well-established PbSe nanocrystals and rarely reported MgF2 nanocrystals. Notably, the model recommends a counter-intuitive, non-stoichiometric precursor ratio (1:1) for MgF2 nanocrystals, which is experimentally confirmed as critical for suppressing byproducts. Our work bridges the gap between unstructured literature and data-driven synthesis, and also establishes a powerful human-AI collaborative paradigm for accelerating nanocrystal discovery.
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All authors Kai Gu, Yingping Liang, Senliang Peng, Aotian Guo, Haizheng Zhong, Ying Fu

Materials Science · Cross-listed from cond-mat.mes-hall

Probing the dynamics and configurations of single molecule junctions via Seebeck coefficient spectroscopy

Juan Hurtado-Gallego, Jeremie Pirard, Abdalghani H. S. Daaoub et al. (+5 more)

Single molecule junctions exhibit dynamic structural configurations that strongly influence their electronic and thermoelectric properties. Here, we combine conductance (G) and Seebeck coefficient (S) measurements using the novel AC based scanning tunnelling microscope break junction technique to probe the real-time evolution of oligo(phenylene ethynylene) molecular junctions. We show that most junctions undergo configuration changes that lead to notable changes in S while G remains nearly constant. Density functional theory and quantum transport simulations link these observations to variations in contact geometry and charge transfer at the molecule electrode interface. Our results demonstrate that simultaneous G and S measurements enable direct access to the dynamic reconfiguration of single molecule junctions and offer design insights for thermoelectric molecular devices and new routes for increasing single molecule junction stability.
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All authors Juan Hurtado-Gallego, Jeremie Pirard, Abdalghani H. S. Daaoub, Sara Sangtarash, Charlotte Kress, Marcel Mayor, Hatef Sadeghi, Pascal Gehring

Materials Science

Magnetic Structures Database from Symmetry-aided High-Throughput Calculations

Hanjing Zhou, Yuxuan Mu, Dingwen Zhang et al. (+11 more)

Magnetic structures-the spatial arrangement of magnetic moments-underpin the diverse functionalities of magnetic materials, yet they have been experimentally determined for only a small fraction of known compounds. Conventional first-principles prediction requires candidate magnetic configurations as input, but the number of possible configurations is in principle infinite. Although the classic Landau-theory based symmetry analysis is widely used to classify magnetic ordering, their direct application to generate input magnetic configurations remains a major challenge due to unavoidable residual degrees of freedom. Here we turn this classification language into a practical predictive framework by resolving these freedoms through a two-step symmetry-aided strategy: an irrep-compatible maximal-magnetic-subgroup selection, followed by the physically motivated high-symmetry-direction construction. This highly efficient scheme is justified within the newly developed oriented spin space group framework. Benchmarked against 1,043 Landau-compatible experimental structures in MAGNDATA, our candidate sets reproduce 90% of the experimentally reported magnetic structures in the four high-symmetry crystal systems with only ~51 candidates per material on average, and subsequent first-principles calculations with material-specific Hubbard U parameters recover the experimental ground state with 83% accuracy. Applying the validated workflow to 19,808 transition-metal compounds, we construct a database of more than 5,000 magnetic materials-nearly twice the size of the experimental MAGNDATA. The database reveals statistical regularities accessible only at scale, including the occurrence rate of magnetism, the prevalence of competing magnetic states, and enables the identification of hundreds of magnetic topological materials, altermagnets, and other emerging magnetic phases and functionalities.
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All authors Hanjing Zhou, Yuxuan Mu, Dingwen Zhang, Yuhui Li, Xiaobing Chen, Hangbing Chu, Fan Jiang, Erjun Kan, Chun-Gang Duan, Di Wang, Huimei Liu, Qihang Liu, Xin-Gao Gong, Xiangang Wan

Materials Science · Cross-listed from cond-mat.mes-hall

Band-Edge Carrier Trapping Limits Light Emission in WSe$_2$

Juri G. Crimmann, Sander J. W. Vonk, Yannik M. Glauser et al. (+2 more)

Monolayers of transition metal dichalcogenides (TMDs) exhibit bright photoluminescence, a desirable property for light-emitting diodes and single-photon emitters. Because the emission intensity is heavily influenced by factors such as defect density and oxidation, it is critical to understand how they affect photoluminescence efficiency. However, due to the time-consuming process of identifying individual monolayers, studies of high-quality exfoliated TMDs have been limited to only a few samples. Here, we present an investigation of excited-state lifetimes and spectra for over 200 WSe$_2$ exfoliated monolayers at room temperature. We find a linear correlation between photoluminescence lifetime and intensity across hundreds of monolayers and within individual monolayers. Results from intentional photooxidation experiments indicate that this correlation is due to photoinduced band-edge carrier traps, which introduce a nonradiative decay pathway that competes with exciton emission. Our work highlights the importance of controlling such traps, as they are the primary limitation of bright photoluminescence.
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All authors Juri G. Crimmann, Sander J. W. Vonk, Yannik M. Glauser, Gabriel Nagamine, David J. Norris

Materials Science

Electrical Regulation of Transverse Spin Currents in Unconventional Magnetic Ferroeletrics

Yudi Yang, Zhuang Qian, Ruichun Xiao et al. (+4 more)

We identify hexagonal YMnO$_3$ as a material realization of the elusive $\beta$-phase of unconventional magnetism, a noncollinear, noncoplanar antiferromagnetic state defined by intrinsic spin-momentum locking and a topological spin texture. First-principle calculations reveal that this unique electronic structure enables a perpendicular electric field to generate a transverse pure spin current, a response that occurs without requiring relativistic spin-orbit coupling. Symmetry analysis demonstrates that this spin current is intimately related to the material's ferroelectric polarization that breaks the inversion symmetry and is rigorously forbidden at domain walls where electrical polarization vanishes. This provides a blueprint for a non-volatile transistor where a gate voltage switches the spin current conductivity by controlling domain wall density, enabling all-electrical control for energy-efficient antiferromagnetic spintronics.
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All authors Yudi Yang, Zhuang Qian, Ruichun Xiao, Yuanyuan Xu, Hua Wang, Shi Liu, Congjun Wu

Materials Science

Sol-Gel-Derived NiO/ZnO Thin Films with Single and Heterostructure Layers for Electrochemical Energy Storage

Miss Nourin Nurain Amina, Md Noushad Hossain, Muhammad Shahriar Bashar et al. (+2 more)

NiO/ZnO-based thin films, including single-layer and heterostructure configurations, were synthesized to investigate the influence of stacking order on their electrochemical performance for supercapacitor applications. To improve the relatively low capacitive performance of ZnO compared to NiO, NaCl was introduced as a dopant. All films were deposited using a non-vacuum spin-coating method on fluorine-doped tin oxide (FTO) substrates, chosen for their excellent electrical conductivity and stability as electrode materials. The surface morphology and structural parameters were examined using scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. Optical properties were analyzed via UV-Vis spectroscopy, revealing direct band gaps in the range of 3.17-3.31 eV for ZnO and Na-ZnO, and wider gaps up to 3.81 eV for NiO. Electrochemical performance was evaluated using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) in a three-electrode configuration with 1 M KOH as the electrolyte. Among the electrodes, the single-layer NiO film exhibited the highest specific capacitance of 1.391 Fg^{-1}. In contrast, the NiO/ZnO heterostructure demonstrated a synergistic effect, resulting in enhanced charge storage and achieving a maximum specific capacitance of 1.627 Fg^{-1} at a current density of 2.0 mA cm^{-2}. Furthermore, sodium doping significantly improved the capacitance of ZnO. Overall, the results highlight the potential of sol-gel-derived oxide heterostructures and doped thin films as cost-effective and scalable electrode materials for supercapacitors in portable electronics and energy storage systems.
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All authors Miss Nourin Nurain Amina, Md Noushad Hossain, Muhammad Shahriar Bashar, Munira Sultana, Md. Salahuddin Mina

Materials Science

Spontaneous growth of perfectly circular domains of MoS2 monolayers using chemical vapour deposition technique

Umakanta Patra and Subhabrata Dhar

Very large-scale integration of devices in a circular pattern has several advantages over the commonly used rectangular grid layout. For the development of such integrated circuits on a 2D semiconductor platform, spontaneous growth of the material in the form of circular islands is desirable. Here, we report the natural formation of 1L-MoS2 circular islands of diameter as large as a few hundreds of micrometer on SiO2/Si substrates by chemical vapor deposition (CVD) technique without the use of any seeding layer. The size of the circles is found to increase with the amount of sulphur used during growth. The study reveals that these circular islands are formed with a less-defective interior and a more-defective outer part that is dominated by a large density of grain boundaries and twists. Due to the lower defect density, the interior region yields much higher photoluminescence than the peripheral part. Field effect transistors (FETs) are fabricated on inner and outer portions of a circle to estimate the mobility and concentration of the background carriers in the two regions. The study shows that the maximum mobility is more than double in the interior than the outer part. While the carrier concentration remains practically unchanged in the two regions. The natural tendency to minimize the strain energy resulting from the mismatch between the thermal expansion coefficients of the monolayer and the substrate as well as the edge energy that originates from the boundary tension are thought to be the driving forces behind the formation of these circular domains.
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Materials Science · Cross-listed from cond-mat.mes-hall

Generating unconventional spin-orbit torques with patterned phase gradients in tungsten thin films

Lauren J. Riddiford, Anne Flechsig, Shilei Ding et al. (+7 more)

A key aim in spintronics is to achieve current-induced magnetization switching via spin-orbit torques without external magnetic fields. For this, the focus of recent work has been on introducing controlled lateral gradients across ferromagnet/heavy-metal devices, giving variations in thickness, composition, or interface quality. However, the small gradients achievable with common growth techniques limit both the impact of this approach and understanding of the underlying physical mechanisms. Here, spin-orbit torques are patterned on a mesoscopic length scale in tungsten thin films using direct-write laser annealing. Through transmission electron microscopy, resistivity, and second harmonic measurements, the continuous transformation of the crystalline phase of W films from the highly spin-orbit coupled, high resistivity $\beta$ phase to the minimally spin-orbit coupled, low resistivity $\alpha$ phase is tracked with increasing laser fluence. Gradients with different steepness are patterned in the tungsten phase to create spin-orbit torque channels and, when interfaced with CoFeB, tungsten wires with a sufficiently strong gradient can switch the magnetization without an applied magnetic field. Therefore, exploiting the unique microstructure of mixed-phase W allows precise control of the local electronic current density and direction, as well as local spin-orbit torque efficiency, providing a new avenue for the design of efficient spintronic devices.
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All authors Lauren J. Riddiford, Anne Flechsig, Shilei Ding, Emir Karadza, Niklas Kercher, Tobias Goldenberger, Elisabeth Müller, Pietro Gambardella, Laura J. Heyderman, Aleš Hrabec

Materials Science · Cross-listed from cond-mat.supr-con

Common sublattice-pure van Hove singularities in the kagome superconductors $\textit{A}$V$_{3}$Sb$_{5}$ ($\textit{A}$ = K, Rb, Cs)

Yujie Lan, Yuhao Lei, Congcong Le et al. (+7 more)

Kagome materials offer a versatile platform for exploring correlated and topological quantum states, where van Hove singularities (VHSs) play a pivotal role in driving electronic instabilities, exhibiting distinct behaviors depending on electron filling and interaction settings. In the recently discovered kagome superconductors $\textit{A}$V$_{3}$Sb$_{5}$ ($\textit{A}$ = K, Rb, Cs), unconventional charge density wave order, superconductivity, and electronic chirality emerge, yet the nature of VHSs near the Fermi level ($\textit{E}$$_{F}$) and their connection to these exotic orders remain elusive. Here, using high-resolution polarization-dependent angle-resolved photoemission spectroscopy, we uncover a universal electronic structure across $\textit{A}$V$_{3}$Sb$_{5}$ that is distinct from density-functional theory predictions that show noticeable discrepancies. We identify multiple common sublattice-pure VHSs near $\textit{E}$$_{F}$, arising from strong V-$\textit{d}$/Sb-$\textit{p}$ hybridization, which significantly promote bond-order fluctuations and likely drive the observed charge density wave order. These findings provide direct spectroscopic evidence for hybridization-driven VHS formation in kagome metals and establish a unified framework for understanding the intertwined electronic instabilities in $\textit{A}$V$_{3}$Sb$_{5}$.
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All authors Yujie Lan, Yuhao Lei, Congcong Le, Brenden R. Ortiz, Nicholas C. Plumb, Milan Radovic, Xianxin Wu, Ming Shi, Stephen D. Wilson, Yong Hu

Materials Science

Phonon-informed Crystal Structure Classification via Precision-Adaptive ResNet-based Confidence Ensemble

Hongyu Chen, Mengyu Dai, Hongjiang Chen et al. (+7 more)

Accurate description of crystal structures is a prerequisite for predicting the physicochemical properties of materials. However, conventional X-ray diffraction (XRD) characterization often encounters intrinsic bottlenecks when applied to complex multiphase systems, necessitating the integration of complementary optical measurement. In this study, we developed a multi-descriptor framework by integrating key parameters including space groups, Pearson symbols, and Wyckoff sequences, to categorize the dataset of over 19,000 crystals into several dozen structural prototypes. Then, an accuracy-adaptive ensemble network based on residual architectures was implemented to capture structural “fingerprints" within phonon vibration modes and Raman spectra. The ensemble algorithm demonstrates exceptional robustness when processing various crystals of varying lengths and quality. This data-driven classification strategy not only overcomes the reliance of traditional characterization on ideal data but also provides a high-throughput tool for the automated analysis of material structures in large-scale experimental workflows.
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All authors Hongyu Chen, Mengyu Dai, Hongjiang Chen, Ruilin Liu, Xiaole Tian, Ruixiao Lian, Yuqian Zhang, Xia Cai, Wenwu Li, Hao Zhang

Materials Science · Cross-listed from cond-mat.mes-hall

Alignment-Dependent Gapless Chiral Split Magnons in Altermagnetic Domain Walls

Zhaozhuo Zeng, Zhejunyu Jin and Peng Yan

Altermagnets, an emerging class of magnetic materials, exhibit exotic chiral split magnons that are of great interest for both fundamental physics and spintronic applications. However, detecting and manipulating these magnons is challenging due to their THz frequency response. Here, we report the discovery of gapless chiral split magnons confined within altermagnetic domain walls. Unlike in conventional ferromagnets or antiferromagnets, their spectrum is highly sensitive to the domain wall orientation relative to the crystal axis. These magnons inherit the chiral splitting of their bulk counterparts and are detectable in the microwave regime, offering a distinctive signature for identifying altermagnets. We further show that the interfacial Dzyaloshinskii-Moriya interaction drives hybridization of magnons with opposite chiralities, enabling unidirectional strong magnon-magnon coupling. Moreover, we demonstrate that spin-orbit torque can control the domain wall orientation, providing a practical means to manipulate these chiral magnons. Our findings open pathways for novel magnonic nanocircuitry based on altermagnetic domain walls.
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Materials Science

Recent Progress in Ultrafast Dynamics of Transition-Metal Compounds Studied by Time-Resolved X-ray Techniques

Hiroki Wadati, Kohei Yamamoto and Kohei Yamagami

X-ray absorption spectroscopy and X-ray magnetic circular dichroism have long served as indispensable tools for probing the electronic and magnetic properties of transition-metal compounds with elemental selectivity. In recent years, the emergence of femtosecond lasers has opened a new avenue for studying nonequilibrium dynamics in condensed matter. However, conventional optical techniques lack elemental and orbital specificity, making it difficult to disentangle the coupled charge, spin, and lattice responses in complex materials. The development of X-ray free-electron lasers (XFEL) and laboratory high-harmonic generation (HHG) sources has enabled the extension of X-ray absorption and scattering techniques into the femtosecond time domain. Time-resolved X-ray absorption spectroscopy, X-ray magnetic circular dichroism, and resonant soft X-ray scattering now provide direct, complementary access to element- and momentum-resolved ultrafast dynamics. This review summarizes recent progress in these techniques, focusing on pump-probe measurements of laser-induced demagnetization, spin-state transitions, and valence and structural changes in transition-metal compounds. We also discuss advances in tabletop HHG-based X-ray spectroscopy and its integration with large-scale XFEL facilities. These developments provide powerful routes for visualizing the nonequilibrium evolution of charge, spin, orbital, and lattice degrees of freedom, offering new insights into the ultrafast control of quantum materials.
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Materials Science

Molecular simulation of methane hydrate growth confined into a silica pore

Ángel M. Fernández-Fernández, María M. Conde, Germán Pérez-Sánchez et al. (+2 more)

The growth of a methane hydrate seed within a silica slit pore of fixed width has been studied using AllAtom Molecular Dynamics (AA-MD). An AA force field has been used to describe the molecules of the solid silica substrate, with a-quartz crystalline structure. The crystallisation of hydrates in confined geometries is not well understood yet, and the objective of this work is to study the hydrate growth inside a silica pore using molecular simulation. Both NVT and NpT ensembles were used in the AA-MD simulations to analyse the hydrate growth from an initial seed. Results showed that the boundary conditions imposed by the nanometric slit pore yielded a hydrate with structural defects, filling the accessible space between the silica walls. The water molecules which were not incorporated to the initial seed hydrate formed a high density water layer trapped between the silica walls and the crystallised hydrate. These results provide an interesting insight into the hydrate crystallisation process in confined geometries, resembling those found in natural hydrate deposits.
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All authors Ángel M. Fernández-Fernández, María M. Conde, Germán Pérez-Sánchez, Martín Pérez-Rodríguez, Manuel M. Piñeiro

Materials Science

Predicting Coherent B2 Stability in Ru-Containing Refractory Alloys Through Thermodynamic Elastic Design Maps

Avik Mahata

Ruthenium-based B2 intermetallics are promising for refractory superalloys but are limited by the trade-off between high thermodynamic stability and elastic precipitation strain. We present a physics-guided machine learning framework integrating high-throughput Density Functional Theory (DFT), Random Forest screening, and Symbolic Regression to navigate this design space. This approach resolves the paradox where stoichiometric compounds like RuHf fail to achieve theoretical solvus temperatures. By deriving a closed-form physical law, we quantify the strain penalty: a 1% lattice misfit reduces the solvus temperature by approximately 200 degrees C. This finding confirms that maximizing thermodynamic driving force alone is insufficient. We demonstrate that multi-component alloying is structurally necessary, identifying ternary additions such as Al and Ti as essential lattice-tuning agents that zero out the elastic penalty. This framework establishes a rigorous, constraint-based protocol for alloy design, enabling the precise engineering of zero-misfit, high-stability microstructures.
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Materials Science

Calorimetric Measurement of the Surface Energy of Enstatite, MgSiO$_3$

Megan A. Householder, Tamilarasan Subramani, Kristina Lilova et al. (+3 more)

Surface thermodynamics of minerals influence their properties and occurrence in both terrestrial and planetary systems. Using high-temperature oxide melt solution calorimetry, we report the first direct measurement of the surface energy of enstatite, MgSiO$_3$. Enstatite nanoparticles of different sizes were synthesized using the sol-gel method, characterized with X-ray diffraction, thermal analysis, infrared spectroscopy, surface area measurements, and electron microscopy. The materials consist of crystallites with sizes of $\sim $10 - 20 nm, which are agglomerated into larger nanoparticles. Thus, both surface and interface terms contribute to the measured enthalpies. Analysis based on calorimetry and calculated surface and interface areas gives the surface enthalpy of enstatite as 4.79 $\pm$ 0.45 J m$^{-2}$. This value is comparable to that of forsterite (Mg$_2$SiO$_4$) and larger than those of many nonsilicate oxide materials. This large surface energy may present a barrier to the nucleation of enstatite in planetary atmospheres and other geochemical and planetary environments. The interfacial energy of enstatite appears to be close to zero. The transition enthalpy from bulk orthoenstatite to bulk clinoenstatite is 0.34 $\pm$ 0.93 kJ mol$^{-1}$, which is in agreement with earlier reports. The methodology developed here can be extended to other materials having complex structures and morphologies to separate surface and interfacial contributions to energetics.
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All authors Megan A. Householder, Tamilarasan Subramani, Kristina Lilova, James R. Lyons, Rhonda M. Stroud, Alexandra Navrotsky

Saturday 3 January

Materials Science · Cross-listed from astro-ph.IM

Exploring Metal Additive Manufacturing in Martian Atmospheric Environments

Zane Mebruer and Wan Shou

In-space manufacturing is essential for achieving long-term planetary colonization, particularly on Mars, where material transport from Earth is both costly and logistically restrictive. Traditional subtractive manufacturing methods are highly equipment-, energy-, and material-intensive, making additive manufacturing (AM) a more practical and sustainable alternative for extraterrestrial production. Among various AM technologies, selective laser melting (SLM) stands out due to its exceptional versatility, precision, and capability to produce dense metallic parts with complex geometries. However, conventional SLM processes rely heavily on inert argon environments to prevent oxidation and ensure high-quality part formation, conditions that are difficult to reproduce on Mars. This study investigates the feasibility of using carbon dioxide (CO2), which makes up over 95% of the Martian atmosphere, as a potential substitute for argon in SLM. Single-track and two-dimensional 316L stainless steel specimens were fabricated under argon, CO2, and ambient air environments with a wide range of laser parameters to evaluate the influence of atmospheric composition on surface morphology, microstructural cohesion, and oxidation behavior. The results reveal that no single parameter controls the overall part quality; rather, a balance of parameters is essential to maintain thermal equilibrium during fabrication. Although parts produced in CO2 exhibited slightly inferior surface finish, cohesion, and oxidation resistance compared to argon, they performed significantly better than those fabricated in ambient air. These findings suggest that CO2-assisted SLM could enable sustainable in situ manufacturing on Mars and may also serve as a cost-effective alternative shielding gas for terrestrial applications.
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Materials Science · Cross-listed from cond-mat.stat-mech

A Unified Computational Framework for Two Dimensional Diffusion Limited Aggregation via Finite-Size Scaling, Multifractality, and Morphological Analysis

Satish Prajapati

Diffusion-Limited Aggregation (DLA), the canonical model for non-equilibrium fractal growth, emerges from the simple rule of irreversible attachment by random walkers. Despite four decades of study, a unified computational framework reconciling its stochastic algorithm, universal fractal dimension, multifractal growth measure, and finite-size effects remains essential for applications from materials science to geomorphology. Through large-scale simulations (clusters up to $N = 10^6$ particles) in two dimensions, we perform a tripartite analysis: (1) We establish a definitive finite-size scaling collapse, extracting the universal fractal dimension $D = 1.712 \pm 0.015$ and identifying the crossover to boundary-dominated growth at a scaled mass $x_0 \approx 0.10 \pm 0.02$. (2) We quantify the full multifractal spectrum of the harmonic measure ($\Delta\alpha \approx 1.13$), directly linking the stochastic algorithm to the deterministic Laplacian growth equation $\nabla^2 p = 0$ and explaining the screening effect via an exponential decay $\eta \sim e^{-r/\xi}$ with screening length $\xi = 22.7 \pm 0.8$ lattice units. (3) We provide a complete morphological characterization, revealing power-law branch length distributions ($\tau \approx 2.1$) and angular branching preferences ($\sim 72^\circ$). This work computationally validates DLA as a robust universality class and provides a scalable methodology for analyzing diffusion-controlled pattern formation across disciplines.
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Materials Science · Cross-listed from cond-mat.supr-con

Exploring the Thermodynamic, Elastic, and Optical properties of LaRh2X2 (X = Al, Ga, In) low Tc Superconductors through First-Principles Calculations

Md. Hasan Shahriar Rifat, Mirza Humaun Kabir Rubel, Md. Borhan Uddin et al. (+3 more)

LaRh2X2 (X = Al, Ga, In) compounds crystallize in a tetragonal layered ThCr2Si2-type structure and belong to a family of low critical temperature superconductors. Using first-principles density functional theory calculations implemented in the CASTEP code, we systematically investigated their structural, mechanical, elastic, electronic, vibrational, thermophysical, and optical properties for the first time. The optimized structural parameters show good agreement with available experimental data. The Born stability criteria and negative formation energies confirm the mechanical and thermodynamic stability of these materials. Poisson and Pugh ratios indicate a ductile nature, while low Debye and melting temperatures together with low Vickers hardness suggest that the compounds are relatively soft. The electronic band structures and density of states reveal metallic behavior. Charge density distribution and Mulliken population analysis indicate mixed covalent, ionic, and metallic bonding. The calculated Fermi surfaces contain both hole-like and electron-like sheets, suggesting possible multiband characteristics. Phonon dispersion analysis confirms the dynamical stability of LaRh2Al2 and LaRh2Ga2, while LaRh2In2 shows dynamical instability associated with a possible structural phase transition. Optical property analysis indicates that these superconductors may be promising candidates for high-density optical data storage applications. The estimated electron-phonon coupling constant of about 0.56 indicates that LaRh2X2 compounds are weakly coupled low critical temperature superconductors.
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All authors Md. Hasan Shahriar Rifat, Mirza Humaun Kabir Rubel, Md. Borhan Uddin, Apon Kumar Datta, Md. Mijanur Rahaman, Jubair Hossan Abir

Materials Science · Cross-listed from cond-mat.mes-hall

Breakdown of Ohm's Law by Disorders in Low-Dimensional Transistors

Chang Niu, Adam Charnas, Jian-Yu Lin et al. (+4 more)

Ohm's law provides a fundamental framework for understanding charge transport in conductors and underpins the concept of electrical scaling that has enabled the continuous advancement of modern CMOS technologies. As transistors are scaled to even smaller dimensions, device channels inevitably enter low-dimensional regimes to achieve higher performance. Low-dimensional materials such as atomically thin oxide semiconductors, 2D van der Waals semiconductors, and 1D carbon nanotubes, have thus emerged as key candidates for extending Moore's law. Here, we reveal the fundamental distinction between three-dimensional and low-dimensional conductors arising from disorder-induced electron localization, which leads to the breakdown of Ohm's law and lateral linear scaling. We develop a quantitative model that captures the role of the disordered region, a unique characteristic intrinsically to low-dimensional transistors. Furthermore, the disorder-induced localization framework consistently explains experimental observations in atomically thin In2O3 field-effect transistors across variations in channel length, temperature, thickness, and post-annealing conditions. This work establishes a unified physical picture for understanding and optimizing disorder-driven electronic transport in low-dimensional transistors.
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All authors Chang Niu, Adam Charnas, Jian-Yu Lin, Linjia Long, Zehao Lin, Zhuocheng Zhang, Peide D. Ye

Materials Science · Cross-listed from quant-ph

Simulating Wigner Localisation with the IBM Heron 2 Quantum Processor: A Proof-of-Principle Benchmarking Study

Airat Kiiamov and Dmitrii Tayurskii

We report on a high-fidelity digital quantum simulation of Wigner localisation in a quasi-one-dimensional (quasi-1D) electron system using a 6-qubit segment of the state-of-the-art IBM\,Heron\,2 quantum processor. By mapping the Coulomb interaction Hamiltonian onto a 6-qubit ring lattice, we reconstruct the ground-state energy landscape for a 2-electron Wigner dimer across fifteen interaction regimes in the range $U \in [5, 75]$. This study serves as a rigorous benchmarking exercise, translating foundational experimental models originally developed for electrons on liquid helium into the domain of modern quantum computing. Leveraging the enhanced gate fidelity and tunable coupler architecture of the Heron 2, we demonstrate that the digital simulation accurately captures the energy minimisation trends associated with Wigner dimer formation, achieving a relative error below 7% in the strong-interaction limit. Our results provide a crucial proof-of-principle validation for using superconducting quantum hardware to probe strongly correlated phases of matter with high precision, establishing a baseline for future simulations beyond the classical limit.
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Materials Science

Structural, Bonding, and Optical Properties of B$_{18}$Ca$_2$ Clusters: Double-Ring Forms

P. L. Rodríguez-Kessler

The structural and electronic properties of the doubly calcium-doped boron cluster B$_{18}$Ca$_2$ have been systematically investigated using density functional theory calculations. Basin-hopping searches reveal that B$_{18}$Ca$_2$ adopts a double-ring geometry as its global minimum, consisting of two fused B$_9$ rings symmetrically stabilized by calcium atoms located above and below the boron framework. Vibrational frequency calculations verify the dynamical stability of the low-lying structures, while infrared and UV-Vis spectra highlight strong Ca–B coupling and pronounced electronic delocalization within the boron scaffold. Atomic dipole-corrected Hirshfeld charge analysis indicates substantial charge transfer from Ca to the electron-deficient boron framework, with the donated electrons uniformly delocalized over the B$_{18}$ skeleton. Real-space bonding analyses based on the electron localization function (ELF), Interaction Region Indicator (IRI), and the Laplacian of the electron density reveal an extended multicenter bonding network characterized by global $\sigma$-delocalization and Ca-induced polarization effects rather than localized two-center Ca–B bonds. Together, these results establish B$_{18}$Ca$_2$ as a prototypical boron toroidal cluster and provide fundamental insights into the role of alkaline-earth doping in stabilizing complex boron nanostructures.
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Materials Science · Cross-listed from cs.ET

Analog Weight Update Rule in Ferroelectric Hafnia, using pico-Joule Programming Pulses

Alexandre Baigol, Nikhil Garg, Matteo Mazza et al. (+5 more)

In an effort to compete with the brain's efficiency at processing information, neuromorphic hardware combines artificial synapses and neurons using mixed-signal circuits and emerging memories. In ferroelectric resistive weights, the strength of the synaptic connection between two neurons is stored in the device conductance. During learning, programming pulses are applied to the synaptic weight, which reconfigures the ferroelectric domains and adjusts the conductance. One strategy to lower the energy cost during the training phase is to lower the duration of the programming pulses. However, the latter cannot be shorter than the self-loading time of the resistive weights, limited by intrinsic parasitics in the circuits. In this work, ferroelectric resistive weights are fabricated using a process compatible with CMOS Back-End-Of-Line integration, based on hafnia/zirconia nanolaminates. By laterally scaling the device area under 100 $\mu$m$^2$, the self-loading time becomes sufficiently short to enable 20 ns programming, which corresponds to a maximum of 3 picoJoules per pulse. Further, in this work, the weight update rule with 20 ns pulses is experimentally measured not only for different amplitudes but also for different initial conductance states. We find that the final weight is determined by the pulse amplitude, independent of the initial weight value.
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All authors Alexandre Baigol, Nikhil Garg, Matteo Mazza, Yanming Zhang, Elisa Zaccaria, Wooseok Choi, Bert Jan Offrein, Laura Bégon-Lours

Materials Science · Cross-listed from physics.comp-ph

AutoPot: Automated and massively parallelized construction of Machine-Learning Potentials

Max Hodapp and Guillaume Anciaux

Machine-learning potentials (MLIPs) have been a breakthrough for computational physics in bringing the accuracy of quantum mechanics to atomistic modeling. To achieve near-quantum accuracy, it is necessary that neighborhoods contained in the training set are rather close to the ones encountered during a simulation. Yet, constructing a single training set that works well for all applications is, and likely will remain, infeasible, so, one strategy is to supplement training protocols for MLIPs with additional learning methods, such as active learning, or fine-tuning. This strategy, however, yields very complex training protocols that are difficult to implement efficiently, and cumbersome to interpret, analyze, and reproduce. To address the above difficulties, we propose AutoPot, a software for automating the construction and archiving of MLIPs. AutoPot is based on BlackDynamite, a software operating parametric tasks, e.g., running simulations, or single-point ab initio calculations, in a highly-parallelized fashion, and Motoko, an event-based workflow manager for orchestrating interactions between the tasks. The initial version of AutoPot supports selection of training configurations from large training candidate sets, and on-the-fly selection from molecular dynamics simulations, using Moment Tensor Potentials as implemented in MLIP-2, and single-point calculations of the selected training configurations using VASP. Another strength of AutoPot is its flexibility: BlackDynamite tasks and orchestrators are Python functions to which own existing code can be easily added and manipulated without writing complex parsers. Therefore, it will be straightforward to add other MLIP and ab initio codes, and manipulate the Motoko orchestrators to implement other training protocols.
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Materials Science · Cross-listed from cond-mat.soft

Dilatancy-induced surface deformation in dense cohesive granular media

Huzaif Rahim, Thorsten Poeschel and Sudeshna Roy

When granular materials with interstitial liquid bridges are sheared in a split-bottom cell, a localized shear band develops, accompanied by a surface elevation. Cohesion, governed by the surface tension of the interstitial liquid, enhances dilatancy in dense cohesive packings, leading to expansion within the shear band and the emergence of a surface elevation. Surface deformation is observed not only in cohesive systems with high particle density and large liquid surface tension, but also in those with lower values of these parameters. The equivalent Bond number arises as a key control parameter for the surface deformation, shaping both the evolution of the surface profile and the packing density. At higher shear rates, inertial effects dominate dilatancy, resulting in less pronounced surface deformation.
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Materials Science

Automatic calculation of symmetry-adapted tensors under spin-group symmetry. STENSOR, a new tool of the Bilbao Crystallographic Server

Luis Elcoro, Jesus Etxebarria, J. Manuel Perez-Mato et al. (+1 more)

We present STENSOR, a new computational tool integrated into the Bilbao Crystallographic Server, designed for the automatic calculation of symmetry-adapted tensors under spin group symmetry. The program requires either a file containing the structural data of the magnetic compound or the generators of the oriented spin point group, together with the so-called generalized Jahn symbol associated to the tensor of interest. The user can propose any arbitrary tensor type or select a particular one from a predefined list. The program output returns the symmetry-adapted tensor under the spin point group and also under the magnetic point group, which is also calculated. The comparison of these two tensor forms allows to distinguish the coefficients that are due to spin-orbit coupling effects from those that have a non-relativistic origin and thus are usually more important. A couple of examples are given to illustrate the operation of the program.
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All authors Luis Elcoro, Jesus Etxebarria, J. Manuel Perez-Mato, Emre S. Tasci

Materials Science

Efficient magnetization switching driven by orbital torque originating from light 3d-transition-metal nitrides

Gaurav K. Shukla, Yoshio Miura, Mayank K. Singh et al. (+1 more)

The orbital Hall effect (OHE) in light transition metals offers a promising route to generate orbital torques for efficient magnetization control, providing an alternative to conventional spin Hall effect approaches that rely on heavy metals. We demonstrate perpendicular magnetization switching in [Co/Pt]3 multilayers driven by the OHE in a light 3d transition metal nitride, VN, with 111-texture of face-center cubic structure. Second harmonic Hall measurement reveals a large torque efficiency of -0.41 in the VN(7.5 nm)/[Co(0.35nm)/Pt(0.3 nm)]3, which significantly surpasses that in the control samples with Co, Py, and CoFeB ferromagnets, suggesting strong conversion of orbital current originating from VN to spin current by [Co/Pt]3 ferromagnet. Full switching by in-plane current is achieved with an in-plane magnetic field, while partial field-free switching occurs without it. The critical current density for the switching is found to be comparable to that of the W-based spin-orbit torque device. First-principles calculations confirm a large orbital Hall conductivity in VN, with a small spin Hall conductivity around the Fermi energy. Our results highlight the potential in the combination of light 3d transition metal nitrides and Co/Pt ferromagnetic multilayer with 111-texture to maximize the magnetization switching efficiency of orbitronic devices.
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All authors Gaurav K. Shukla, Yoshio Miura, Mayank K. Singh, Shinji Isogami

Materials Science

Landscape of grain boundary migration in polycrystals

Jianfeng Hu

Grain boundary (GB) migration is a pivotal process that significantly impacts the development of microstructures, thereby influencing the practical performance of polycrystalline materials. Recent advances in 3D experimental techniques have revealed conflicts between observed GB migration behaviors and classical theoretical models. These contradictions raise two fundamental questions, namely, whether GB migration is linearly related to curvature, and how GB energy affect GB migration? Here, we provide a comprehensive analysis of GB migration dynamics in polycrystals and resolve these conflicts within a theoretical framework. Unexpectedly, in a polycrystalline system, the range of GB migration velocities shows little correlation with the magnitude of its curvature. The extent of the influence of GB energy on GB migration is revealed to mostly depend on GB step energy. Finally, a more general GB migration formula is derived to incorporate various driving forces beyond curvature.
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