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Physics Condensed Matter Materials Science

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Friday 5 June

Materials Science

Flexible PDMS/La$_{0.7}$Sr$_{0.3}$MnO$_3$/MWCNT Composite Thin Films for Multifunctional Temperature and Magnetic Sensing Electronic Skin

Jimlee Patowary, G. Suresh, Jitendra Kumar et al. (+1 more)

The development of multifunctional electronic skin (e-skin) requires materials that combine mechanical flexibility with responsiveness to multiple stimuli. In this work, a flexible PDMS/La0.7Sr0.3MnO3 (LSMO)/MWCNT composite thin film was fabricated via solution casting, using LSMO powder synthesized by a solid-state reaction method. Structural and spectroscopic analyses confirm the formation of single-phase rhombohedral LSMO and successful incorporation of PDMS, LSMO, and MWCNT components. The composite exhibits a smooth and uniform surface morphology, along with significantly enhanced thermal stability, retaining ~70% mass at elevated temperatures. Electrical measurements reveal thermally activated resistivity behavior, enabling temperature sensing functionality. Additionally, the composite shows a notable decrease in resistance under an applied magnetic field, exhibiting magnetoresistance due to spin-dependent transport in the LSMO phase. Mechanical testing indicates elastomeric behavior with a maximum load of ~0.49 N and stretchability of ~26%, along with ductile deformation characteristics. The multifunctional sensing properties arise from the synergistic interaction between the conductive MWCNT network and magnetically active LSMO within the flexible PDMS matrix. Overall, the composite demonstrates a unique combination of thermal stability, mechanical flexibility, and dual sensing capability, making it a promising material for next-generation e-skin applications.
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All authors Jimlee Patowary, G. Suresh, Jitendra Kumar, Ashutosh Kumar

Materials Science

Peculiarities Of Phase States In N2O-CO2 Cryoalloys According To Electron Diffraction Data

A. A. Solodovnik and O. P. Konotop

The structural characteristics of n2o-co2 alloys have been studied using transmission electron diffraction (THEED) across the entire range of their mutual concentrations at temperatures of 5 K and 65 K. The ranges in which regular solutions exist and intervals of alloy phase separation have been identified using the dependence of lattice parameters on composition and profile analysis of the diffraction pattern intensity distribution. It was found that maximum solubility values are up to 11 mol.% CO2 in the N2O matrix and up to 30 mol.% n2o in solid co2 at 65 K. The solubility limits for the components at 5 K are less 20 mol.% co2 in crystalline n2o and less than 35 mol.% n2o in a co2 crystal lattice. It was established that the character of n2o-co2 alloy separation corresponds to the mechanism of spinodal decomposition. The relative excess volumes that pertain to the admixture were determined for the CO2 impurity in solid n2o and for n2o impurity in co2 crystal. Conclusions regarding the character of n2o-co2 phase diagram have been made.
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Materials Science

Towards Engineering Material Neural Networks

Charles de Kergariou, Hortense le Ferrand, Ali Momeni et al. (+4 more)

Structures that capture functionality in the form of animate or intelligent machines have the potential to transform modern engineering applications. Animation and embedded intelligence are typically realised by integrating advanced capabilities such as reversibility, adaptive responses and learning directly into the materials themselves. Currently, the majority of adaptive material systems rely on predefined adaptive designs combined with in-service, electronics-based computing to dynamically modify the structural behaviour. However, structural configurations with interconnected adaptable nodes are able to approximate continuous functions, providing new possibilities and opportunities than classical metamaterials and computational materials. We discuss here the potential to design load-bearing engineering materials with trainable physical parameters and neural network-inspired morphologies, embedding intelligence directly into their structure, a concept we define as Engineering Material Neural Networks (EMNNs) as a subcategory of Physical Neural Networks. In this perspective, we first establish the foundational concept of EMNNs; we then detail the mechanical and multifunctional properties required for such structural configurations. Finally, we evaluate existing and emerging engineering materials that hold promise for enabling this innovative approach. Key material candidates for realising EMNNs include composites, architected, biological and engineering living materials. We also outline future directions in materials science and structural engineering for developing EMNNs.
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All authors Charles de Kergariou, Hortense le Ferrand, Ali Momeni, Romain Fleury, Kunal Masania, Adam W Perriman, Fabrizio Scarpa

Materials Science

Ptychographic Algorithms for Phase Recovery in 4D Scanning Transmission Electron Microscopy

Amel Shamseldeen Ali Alhassan

In Momentum-resolved Scanning Transmission Electron Microscopy (4D STEM), a convergent electron beam is raster-scanned across a think specimen in 2D in real space. The corresponding 2D diffraction pattern, in momentum space, to each point is recorded, forming a 4D data set. Information decoding process can follow thereafter to produce an image of the specimen in real space. Ptychography is reconstruction algorithm that allow the extraction of the probe wavefunction and the multiplicative object transmission function of the specimen. Ptychography is implemented through direct and iterative schemes. Some of which are the extended Ptychographic Iterative Engine (ePIE), the Wigner Distribution Deconvolution (WDD) and the simpler version of WDD, the Single Side-Band (SSB). This thesis gives an overview of STEM ptychography giving examples of its experimental and simulated implementations. The different ptychographic reconstruction methods are explored in a mathematical framework when applicable. Finally, an SSB reconstruction was made using an original script for simulated data of MoS2 monolayer. Moreover, four-dimensional data was recorded using a STEM instrument. A natural step following this research would be the implementation of the WDD algorithm.
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Materials Science

Chromium chalcohalide Janus monolayer ferromagnets with perpendicular magnetic anisotropy and high Curie temperature

M. Bosnar, J.M. Lendinez, A.Yu. Vyazovskaya et al. (+8 more)

Using density functional theory, we revisit the magnetic properties of a recently proposed family of noncentrosymmetric two-dimensional magnetic materials, chromium chalcohalide monolayers, CrXY (X=S, Se, Te; Y=Cl, Br, I). These systems consist of three atomic planes stacked in the X-Cr-Y sequence, which breaks inversion symmetry, giving rise to their designation as "Janus" monolayers. We consider both 1T and 1H structural polymorphs of CrXY. Among the two polymorphs, the 1T phase is consistently more favorable, with energy gains exceeding 0.55 eV per formula unit. Our total-energy calculations reveal that all dynamically stable CrXY monolayers exhibit ferromagnetic coupling. However, robust out-of-plane magnetic anisotropy is observed only in the CrSI and CrSeI compositions, for both 1T and 1H structures. The perpendicular magnetic anisotropy results from a constructive interplay between single-ion and anisotropic exchange contributions that overcome the dipole-dipole interaction. We further quantify the Dzyaloshinskii-Moriya interaction (DMI) in CrSI and CrSeI for both polymorphs, and reveal a weak-to-moderate DMI strength as compared to the isotropic exchange interaction term. Finally, for systems exhibiting ferromagnetic coupling and perpendicular magnetic anisotropy, the exchange and anisotropy parameters derived from density functional theory calculations are employed as inputs for large-scale atomistic spin dynamics simulations to probe the temperature evolution of real-space magnetic structures. The calculated Curie temperatures are at least 210 K for 1T-CrSI, 235-260 K for 1H-CrSeI, and 370-410 K for 1H-CrSI. In contrast, the sizable DMI in 1T-CrSeI results in a worm-like domain ground state at zero external field and enables the stabilization of skyrmions under a perpendicular magnetic field.
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All authors M. Bosnar, J.M. Lendinez, A.Yu. Vyazovskaya, I.Yu. Sklyadneva, R. Heid, S. V. Eremeev, U. Atxitia, S. Gallego, E.V. Chulkov, A. Arnau, M.M. Otrokov

Materials Science

Skyrmions in Synthetic Antiferromagnets: Collapse and Nucleation

M.N. Potkina

Magnetic skyrmions in synthetic antiferromagnets are promising nanoscale bits, but their usefulness depends on how reliably a written pair survives and can be created. Using a reduced lattice model, we compute minimum energy paths for collapse of an antiferromagnetically bound skyrmion pair and for reverse nucleation from a pinned antiferromagnetic reference state. With antiferromagnetically pinned boundaries, the main saddle energy changes only weakly with pinned-island size, whereas the skyrmion-pair minimum carries a strong size-dependent boundary penalty. For large pinned islands, collapse is layer-sequential and can pass through a single-layer skyrmion intermediate whenever this state satisfies the relaxation criterion. The much larger reverse barrier for nucleation shows a strong asymmetry with collapse in the same pinned-boundary model and is consistent with assisted layer-sequential writing.
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Materials Science

Cocktail effect and robust Berry curvature driven anomalous Hall conductivity in the entropy-stabilized Heusler alloy Co$_2$(Ti$_{0.25}$V$_{0.25}$Cr$_{0.25}$Fe$_{0.25}$)Al

Suraj Kushwaha, S. K. Panda, Sourav Marik et al. (+2 more)

The interplay between chemical disorder and persistence of Berry curvature driven transport phenomena remains an important open question in entropy-stabilized systems. Here, we synthesize an entropy-stabilized Heusler alloy Co$_2$(Ti$_{0.25}$V$_{0.25}$Cr$_{0.25}$Fe$_{0.25}$)Al and systematically investigate its structural, magnetic, and magnetotransport properties using a combination of experimental measurements and density functional theory (DFT) calculations. The system crystallizes in cubic space group $Fm\Bar{3}m$ and exhibits ferromagnetism with saturation magnetization in close agreement with the Slater–Pauling prediction. Transport and magnetotransport measurements reveal metallic behavior and a pronounced anomalous Hall effect with an anomalous Hall conductivity of approximately $134.4~ \Omega^{-1}$.cm$^{-1}$. Combined experimental observations and first-principles calculations establish that the anomalous Hall effect is predominantly intrinsic in origin and originates from the Berry curvature of the electronic bands. Remarkably, despite the substantial configurational disorder and the dilution of the constituent parent compounds, the anomalous Hall conductivity remains comparable to the largest values reported in the corresponding parent Heusler systems. This behavior reflects the manifestation of the cocktail effect, one of the core characteristics of entropy-stabilized systems. Our results also demonstrate that Berry curvature mediated transport persists in this chemically disordered system and indicates that entropy engineering can be a promising route for tuning intrinsic anomalous Hall responses.
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All authors Suraj Kushwaha, S. K. Panda, Sourav Marik, Kartik Samanta, Tirthankar Chakraborty

Materials Science

Unravelling the Role of Stacking Disorder on the Optoelectronic Properties of Zn3P2

Francesco Salutari, Nico Kawashima, Aidas Urbonavicius et al. (+9 more)

Zinc phosphide (Zn3P2) is a promising photovoltaic absorber for thin-film and flexible solar cells due to its earth-abundant composition and favourable optoelectronic properties. Recent advances in epitaxy have enabled the growth of high-quality Zn3P2 thin films despite the challenges posed by its incompatible lattice parameter and thermal expansion coefficient. However, Zn3P2 remains prone to intrinsic extended defects, such as rotated domains, that can limit device performance. Here, using (scanning) transmission electron microscopy, we identify a previously unreported class of extended defects that appear as planar faults described by displacement vectors lying in the (001) plane. Within a pseudo-cubic description of Zn3P2, we establish a direct correspondence between planar faults and rotated domains, showing that both arise from the flexible ordering of vacant sites in the Zn sublattice. First-principles calculations reveal an extremely low planar-defect formation energy of 2.5 mJ m-2, demonstrating that these defects form at essentially negligible energetic cost, in excellent agreement with their high experimentally observed occurrence. Additional density functional theory (DFT) calculations show that intrinsic planar defects neither introduce mid-gap electronic states nor significantly perturb the local electrostatic potential, indicating that they are electronically benign. Instead, we propose that planar defects indirectly degrade device performance by acting as preferential segregation sites for optically active point defects.
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All authors Francesco Salutari, Nico Kawashima, Aidas Urbonavicius, Helena Rabelo Freitas, Raphael Lemerle, Thomas Hagger, Kimberly A. Dick, Anna Fontcuberta i Morral, Simon Escobar Steinvall, Maria Chiara Spadaro, Silvana Botti, Jordi Arbiol

Materials Science

Iron-mediated on-surface synthesis of substrate-decoupled graphdiyne monolayers

Alice Cartoceti, Simona Achilli, Gianni Conti et al. (+9 more)

Graphdiynes are emerging two-dimensional sp-sp$^2$ carbon materials with electronic structures complementing those of graphene, yet their on-surface synthesis is limited by the persistence of metalated intermediates or yields disordered covalent networks. Here, we report an iron-assisted route to covalent hydrogenated graphdiyne monolayers on Au(111) from 1,3,5-tris(bromoethynyl)benzene. Low-temperature scanning tunnelling microscopy, X-ray photoelectron spectroscopy and density functional theory show that Fe scavenges chemisorbed Br byproducts forming FeBr$_2$, in turn promoting the removal of Au adatoms from the organometallic network, thus enabling its metalated-to-covalent conversion under mild thermal treatment. Subsequent annealing removes FeBr$_2$ and yields covalent, ordered domains weakly coupled to the substrate. Scanning tunnelling spectroscopy, combined with density functional theory, reveals a semiconducting gap of about 1.6 eV associated with carbon p$_z$ frontier orbitals. This Fe-mediated on-surface synthesis strategy provides a route to atomically precise, weakly substrate-coupled graphdiyne networks and offers a design principle for two-dimensional carbon semiconductors.
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All authors Alice Cartoceti, Simona Achilli, Gianni Conti, Eliecer Pelaez-Sifonte, Alessio Orbelli Biroli, Sabine Maier, Francesco Sedona, Paolo D'Agosta, Francesco Tumino, Andrea Li Bassi, Jorge Lobo-Checa, Carlo S. Casari

Materials Science

Electric-field induced trends of exchange interactions in transition-metal trilayers

Moinak Ghosh, Stefan Heinze and Souvik Paul

Using density functional theory, we have performed a systematic study of the Heisenberg pairwise exchange interaction and the beyond Heisenberg multi-spin higher-order exchange interactions in unsupported transition-metal trilayers in the presence of external electric fields. The systems consist of a hexagonal atomic Fe layer sandwiched between 4$d$ (Ru, Rh, and Pd) and 5$d$ (Ir) transition-metal layers. Both fcc and hcp stackings of the 4$d$ overlayer have been taken into account. To scan a large part of the magnetic phase space, we have calculated the energy dispersion of spin spirals without and with applied electric fields up to $\pm 1.0$ V/Å. We find that the energy dispersion remains qualitatively the same upon applying the electric fields and the magnetic ground state remains unchanged. The exchange constants obtained by fitting the energy dispersions exhibit a linear dependence on the electric field up to values of about $\pm 0.5$ V/Å. The sign of the calculated pairwise and higher-order exchange constants remain unchanged with electric field, however, their values and field induced variation are sensitive to the 4$d$ overlayer. The changes are on the order of a few percent for the nearest-neighbor exchange constant and up to a few ten percent for beyond nearest-neighbor constants. The higher-order exchange constants are calculated based on the total energies of multi-$Q$ states, such as the $uudd$ and the 3$Q$ state. Similar to the pairwise exchange constants, we find a nearly linear field dependence of the higher order constants at small electric fields and variations of up to ten percent. We study the spin-dependent screening of the electric field for the three trilayers based on the spin- and orbital-decomposed electronic states.
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Materials Science

Characterization of Nonlinear Dynamics in Semiconductors in Frequency Domain using Modulated Photoexcitation

Attia Awan, Rong Tang, Zhou Kang et al. (+1 more)

Carrier dynamics in semiconductors is inherently complex owing to the coexistence of different excited species, such as free carriers and excitons, and their interactions among themselves and with traps and phonons. It is usual to use time-resolved responses to identify the processes that contribute to the dynamics. However, the responses often are non-exponential, leading to ambiguity in the interpretation. Here, we propose a frequency domain method to characterize nonlinear dynamics in semiconductors using CdSe as the test system. We show that by analyzing the frequency components in the total photoluminescence induced by a pair of phase-modulated beams, the parameters, such as rates of different types of recombination of free carriers and excitons, can be evaluated. The method can be used as a simple diagnostic tool to characterize ultrafast processes that are relevant to the functionality of semiconductor devices.
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All authors Attia Awan, Rong Tang, Zhou Kang, Khadga Jung Karki

Materials Science · Cross-listed from physics.optics

Circular Raman responses from angular-momentum inequivalence in CoSi

Yuki Suganuma, Gakuto Kusuno, Kohei Miyazaki et al. (+8 more)

Circularly polarized Raman scattering in solids exhibits distinct phenomena such as Raman optical activity (ROA) and chiral-phonon-induced frequency splitting, whose relationship has remained unclear. Here we show that these seemingly different responses can be understood within a common framework based on the inequivalence of phonon states carrying opposite crystal angular momenta. Using helicity-resolved Raman spectroscopy of the chiral crystal CoSi, we find that ROA and frequency splitting arise from different symmetry channels, namely axial multipolar symmetry and structural chirality, respectively. First-principles calculations reproduce both effects and clarify their symmetry origins. These results establish angular-momentum inequivalence as a unifying principle of circular Raman responses and link helicity-resolved Raman spectroscopy to the angular-momentum structure of chiral phonons in topological materials.
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All authors Yuki Suganuma, Gakuto Kusuno, Kohei Miyazaki, Hikaru Watanabe, Rikuto Oiwa, Ryotaro Arita, Satoshi Iwasaki, Yoshiki Yasuoka, Yusuke Kousaka, Yoshihiko Togawa, Takuya Satoh

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

Distilling first-principles accuracy into compact machine learning potentials for condensed-phase chemistry

Sijia Chen, Niamh O'Neill, Benjamin X. Shi et al. (+1 more)

Accurate machine learning interatomic potentials (MLIPs) have made first-principles-quality potential energy surfaces increasingly accessible for condensed-phase chemistry, but their inference cost can still limit the sampling needed to compute experimentally relevant observables. In this work, we combine transfer learning and knowledge distillation to construct compact "student" models that retain the accuracy of much larger "teacher" models obtained by applying transfer learning to foundation models. The resulting students reduce production simulation cost by roughly an order of magnitude, making high-accuracy sampling practical for challenging condensed-phase problems. We demonstrate this across three problems of increasing sampling complexity: finite-temperature NPT simulations of ice Ih, classical and path-integral simulations of liquid water over 240-370 K, and path-integral umbrella-sampling simulations of water dissociation at the anatase TiO2(101)/water interface. In all cases, the distilled students reproduce the target observables of their teachers more reliably than models of the same size trained directly on the limited reference data. The liquid-water student, distilled from a {\Delta}-learned CCSD(T)-quality teacher, reproduces thermodynamic, structural, transport, and nuclear quantum properties over the full temperature range studied. At the TiO2/water interface, distillation makes PIMD umbrella sampling practical and shows that nuclear quantum effects lower the dissociation barrier by roughly 2 kcal/mol and shift the molecular-dissociated free energy difference into quantitative agreement with recent solid-state 17O NMR measurements. Our work demonstrates how knowledge distillation can make accurate MLIPs practical for the sampling methods needed to connect condensed-phase reaction thermodynamics with experiment, notably for interfacial chemistry and catalysis.
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All authors Sijia Chen, Niamh O'Neill, Benjamin X. Shi, Venkat Kapil

Thursday 4 June

Materials Science · Cross-listed from cs.AI

PhononBench-MP40: a spectrum-resolved benchmark dataset for phonon stability

Wen-Kao Li, Ze-Feng Gao and Zhong-Yi Lu

Imaginary phonon modes remain a practical bottleneck in computational materials screening because otherwise plausible structures can be locally dynamically unstable under a chosen workflow. Here we present PhononBench-MP40, a spectrum-resolved benchmark dataset of Materials Project-derived crystals for workflow-defined phonon stability. The dataset starts from 47,969 MP40 workflow tasks and provides 46,899 completed records with paired stability labels and local phonopy YAML spectra, including 16,683 Stable records and 30,216 completed-phonon unstable records. A further 1,067 relaxation failures are reported separately rather than merged into the completed phonon denominator. The release centers on the local YAML spectrum: the stability label, the lowest sampled frequency and any threshold-dependent relabeling are derived from that spectrum. The dataset is openly available through Science Data Bank at https://doi.org/10.57760/sciencedb.38735. A companion GitHub repository provides the calculation code and lightweight access utilities. PhononBench-MP40 provides an auditable reference for workflow-defined stability classification, minimum-frequency analysis, threshold studies and failure-aware triage, while keeping the reference workflow, data schema and interpretation boundaries explicit.
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Materials Science · Cross-listed from cond-mat.mes-hall

Hierarchical Disorder in Moiré Exciton Photoluminescence Probed by Spectral-Descriptor Correlations

Katsunori Wakabayashi

Hyperspectral photoluminescence (PL) maps of moiré transition-metal dichalcogenide heterobilayers encode rich information about the underlying disorder, but extracting it is hampered by the ambiguity of assigning individual spectral peaks. We show that the spatial correlations among a set of simple, peak-decomposition-free spectral descriptors – such as the centroid energy, the dominant-peak energy, and a sharp-line fraction – provide a peak-decomposition-free route to infer features of that disorder. Different descriptors act as filters that select different components of a multi-scale disorder landscape – a smooth, micron-correlated background and a dense set of localized traps – and therefore acquire different spatial correlation lengths. The central prediction is a correlation-length hierarchy, $\xi(E_{\rm cent}) \ge \xi(E_{\rm dom})$, which we derive by splitting the dominant-peak energy into a smooth background part and a short-range trap-switching fluctuation. The same picture explains the measured inter-descriptor correlations, including the near-perfect anticorrelation $\rho_{\rm S}(\Delta E_{\rm cd}, R_{\rm HL}) \approx -0.978$, which we show to be a robust geometric trend for spectra dominated by a common emission-envelope asymmetry. Benchmarked against phenomenological simulations, Hamiltonian diagonalization, and the measured MoSe$_2$/WSe$_2$ descriptor correlations, the framework turns descriptor maps into a quantitative, peak-decomposition-free probe of slow disorder and local traps in moiré excitons and, more broadly, in disordered semiconductor emitters.
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Materials Science

Atomic-scale phase-field modeling for 2D ferroelectrics including non-Gaussian fluctuations

Kairi Masuda and Yu Kumagai

Atomic-scale phase-field modeling extends the phase-field framework down to the level of individual atoms by treating the probability density of atomic vibrations as a field variable and constructing a corresponding free-energy functional from this atomic field together with interatomic potentials. In this way, the framework has the potential to visualize local thermodynamic states with atomic-level resolution, just as conventional phase-field modeling has served as a computational microscope for free energy, stress, and related quantities at mesoscopic scales. However, existing formulations mainly assume Gaussian probability distributions for atomic vibrations, which limits their applicability to more complex and heterogeneous systems such as surfaces. In this work, we generalize the atomic-scale phase-field methodology by extending the free-energy functional to include non-Gaussian fluctuations. We apply this approach to monolayer SnTe in the NVT ensemble and show that the predicted equilibrium polarization is in better agreement with molecular dynamics simulations and that the ferroelectric-to-paraelectric phase transition is successfully reproduced. Furthermore, by decomposing the entropy on a per-atom basis, we visualize atomically resolved maps of local entropy and find that Sn atoms contribute more strongly to the entropy than Te atoms at high temperature, which is a driving factor of the ferroelectric-to-paraelectric phase transition. These results broaden the applicability of phase-field approaches to a wider range of atomic systems and suggest a route toward an atom-resolved theory of phase transitions based on high-resolution thermodynamics.
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Materials Science

Reactivity-Informed Machine Learning for Performance Prediction and Design Space Exploration of Alkali-Activated Slag

Qiyao He, Zhanzhao Li and Kai Gong

Establishing quantitative relationships among mix design, raw material properties, curing conditions, and performance remains a long-standing challenge in cementitious materials, particularly for alkali-activated materials with variable precursor and activator chemistry. Here, we curated the largest literature-derived alkali-activated slag (AAS) dataset to date, comprising over 3100 compressive strength records, 155 chemically distinct ground granulated blast-furnace slags (GGBSs), and 24 attributes incorporating precursor chemistry, fineness, and reactivity. Multiple machine learning (ML) algorithms were benchmarked across progressively enriched feature scenarios, demonstrating that integrating GGBS compositions, fineness, curing conditions, and specimen geometry improves predictive performance. The average metal oxide dissociation energy (AMODE), a physically interpretable representation of precursor reactivity, provides a compact alternative descriptor to explicit oxide compositions while enabling comparable predictive performance. Model interpretation revealed physically consistent trends from heterogeneous data, including non-monotonic effects of Na2O dosage and silicate modulus, reduced predicted strength at higher water content and larger specimen size, and coupled oxide-level effects more coherently represented by AMODE than by individual oxide contents. Statistically constrained design space exploration reveals reactivity-dependent trade-offs among strength, embodied CO2 emissions, and cost. The design maps identify high-strength regions with substantially lower CO2 emissions than OPC-based references at similar cost. Overall, this work demonstrates how reactivity-informed ML can extract physically meaningful trends from heterogeneous AAS data and guide source-dependent binder design. The curated dataset is publicly accessible to support advances in cement and concrete research.
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Materials Science

Engineering magnetic anisotropy and ferromagnetism in topological Kagome metal GdV6Sn6 via Nd substitution

Santosh Karki Chhetri, M.M. Sharma, Jian Wang et al. (+4 more)

Kagome metals with the formula RM6X6 (R = rare-earth, M = 3d transition metal, and X = Sn/Ge) provide a rich platform for exploring magnetic and electronic phenomena, with tunable properties enabled by the combination of rare-earth elements and transition metals. In this study, we report the structural, electrical and magnetic properties of Kagome metal (NdxGd1-x)V6Sn6. We demonstrate that substituting lighter Nd atoms at the Gd site tunes the complex magnetic ground state of GdV6Sn6 into a ferromagnetic-like one. Moreover, the isotropic magnetization of GdV6Sn6 becomes anisotropic, with the c-axis emerging as the easy axis. Transport measurements reveal a strong coupling between magnetism and electronic properties, with negative magnetoresistance observed at low magnetic fields in all compositions. In addition, a fourfold anisotropy component tends to emerge in end compounds at higher magnetic fields. These findings highlight the role of rare-earth substitution in tuning magnetic anisotropy and magneto-transport behaviour in RM6X6 compounds, featuring a non-magnetic Kagome layer, with potential implications for spintronic and topological applications.
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All authors Santosh Karki Chhetri, M.M. Sharma, Jian Wang, Dinesh Upreti, Gokul Acharya, Md Rafique Un Nabi, Jin Hu

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

Plasticity of Neutron Star Crusts

Matthew E Caplan, Nevin T Smith, Ashley J Bransgrove et al. (+1 more)

We use first-principles molecular dynamics simulations to study the deformation and breaking of neutron star crusts. When simulating with strain rates several orders of magnitude slower than prior work, we find a new regime of steady plastic flow beyond the breaking point that is independent of the initial crystal structure. Polycrystals exhibit a robust transition from linear elasticity to perfect plastic flow at shear strains of $\epsilon = 0.05$, while monocrystals break at $\epsilon = 0.11$ and then flow plastically. The universal post-break plasticity may arise because the crystal self-consistently assumes a defect density to accommodate the imposed strain rate. If broken crusts can re-anneal to large crystal sizes, crust breaking may repeat with implications for magnetar bursts and flares.
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All authors Matthew E Caplan, Nevin T Smith, Ashley J Bransgrove, Charles J Horowitz

Materials Science

Symmetry-Protected Phonon Topology and Low Lattice Thermal Conductivity in Square-Octagonal Chalcogenides

Nair Surabhi Suresh, Mondal Chiranjith, Alam Aftab et al. (+1 more)

Unconventional lattice geometries provide an effective platform for realizing symmetry-protected topological phonon states that can strongly influence lattice heat transport. In this work, we explore the relationship between topological phonon band features and thermal transport in square–octagonal (so) chalcogenide monolayers, namely MoS2 and SnS, by combining first-principles calculations with phonon Boltzmann transport theory. Symmetry analysis reveals the presence of nontrivial phonon band topology in the form of symmetry-protected nodal lines. Crossings between nodal lines carrying different symmetry eigenvalues produce fourfold Dirac points that enhance the phonon group velocity (vg), whereas nearly flat nodal lines lead to strong suppression of vg. The coexistence of these features, together with substantial phonon softening and enhanced anharmonic scattering around the topological band crossings, markedly suppresses the lattice thermal conductivity ($\kappa_l$). As a result, room-temperature $\kappa_l$ values of 4.0 W/mK for so-SnS and 18.7 W/mK for so-MoS2 are obtained, representing reductions by more than a factor of two and eight, respectively, relative to their hexagonal phases. Our results uncover a direct connection between phonon band topology and heat transport in two-dimensional materials, highlighting lattice symmetry and topological band engineering as promising routes for tailoring thermal properties. These findings further suggest opportunities for designing topological phononic and thermoelectric devices with controllable heat flow.
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All authors Nair Surabhi Suresh, Mondal Chiranjith, Alam Aftab, Singh Nirpendra

Materials Science

Matching Terahertz and Hall Mobilities as a Hallmark of Intrinsic Charge Transport in Metal-Halide Perovskites

Dmitry R. Maslennikov, Ben P. Carwithen, Vladimir V. Bruevich et al. (+9 more)

Charge-carrier transport in soft-lattice materials, including metal-halide perovskites, is often perceived to be highly heterogeneous across different length scales, and influenced by both the intrinsic (dynamic) thermal electronic disorder and extrinsic (static) disorder due to crystal defects, impurities, grain boundaries, and surface states. As a consequence, the reported carrier mobilities obtained by different electrical and optical measurement techniques frequently disagree, raising a critical question: can a truly intrinsic charge transport regime (that is, a regime not dominated by static disorder) extend across macroscopic single crystals of these materials? Here, we demonstrate such a regime in an exemplary metal-halide perovskite system, epitaxial CsPbBr$_{3}$ single crystals, where the local mobility obtained via optical pump-terahertz probe (OPTP) spectroscopy quantitatively agrees with the macroscopic transport mobility across a broad range of experimental conditions. Using a dedicated device platform that enables concurrent Hall-effect and OPTP measurements on the same single-crystalline sample, we obtain consistent room-temperature mobilities of ~ 30 cm$^{2}$V$^{-1}$s$^{-1}$, among the highest reliably reported for CsPbBr$_{3}$. Both techniques reveal band-like temperature dependence of the hole mobility with similar power exponents, confirming that the same intrinsic transport mechanism governs the ultrafast/local and steady-state/macroscopic responses. These results show that defect-free charge transport is achievable in soft-lattice perovskites on millimetre length scales and establish a robust methodology for benchmarking intrinsic mobility in emerging semiconductors.
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All authors Dmitry R. Maslennikov, Ben P. Carwithen, Vladimir V. Bruevich, Yichao Cai, Davide Nodari, Navendu Mondal, Xijia Zheng, Beier Hu, Nicola Gasparini, Jarvist M. Frost, Vitaly Podzorov, Artem A. Bakulin

Materials Science

Temperature-Induced Crossover of Coherent Phonon Mechanisms in Chiral 2D Perovskites

Katherine A Koch, Matthew P Hautzinger, Matthew C Beard et al. (+1 more)

The coupling between electronic excitations and lattice degrees of freedom fundamentally dictates the optoelectronic functionality of hybrid perovskites. While the potential energy surfaces (PESs) of the electronic excited states are typically considered static, albeit modulated by thermal disorder, the exact nature of their structural evolution with temperature remains elusive. Here, we demonstrate that the excited-state structural reconfiguration in two-dimensional metal-halide perovskites is explicitly temperature-evolving, governed by lattice compliance. We select a chiral perovskite framework with an exceptionally large, temperature-dependent bond angle variance to maximize the structural compliance. Through phase-resolved resonant impulsive stimulated Raman scattering, we measure the coherent phonon dynamics and resolve the real-time structural pathways of exciton-lattice dressing. We observe a temperature-induced crossover from field-driven Impulsive Stimulated Raman Scattering (ISRS) to population-driven Displacive Excitation of Coherent Phonons (DECP). While momentum-driven ISRS pathways dominate at low temperatures, increasing thermal energy softens the lattice and enhances coordinate-driven displacive pathways, allowing excitons to sample steeper, highly anharmonic regions of the excited-state PES. Our results show that temperature can actively modulate the excited-state structural coordinates of flexible 2D frameworks, offering a practical strategy to tune exciton-lattice interactions in chiral optoelectronics.
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All authors Katherine A Koch, Matthew P Hautzinger, Matthew C Beard, Ajay Ram Srimath Kandada

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

Self-organized Floquet band geometry in cavity-driven quantum materials

Christopher Yang, Gil Refael, Mark S. Rudner et al. (+1 more)

Floquet engineering has emerged as a powerful route to dynamically control band structure and topology in quantum materials, but most implementations rely on externally imposed laser fields that are power intensive, difficult to integrate into devices, and weakly coupled to the electronic system. We propose and analyze an alternative paradigm in which a self-generated cavity field Floquet-dresses the electronic bands and produces a geometric Hall response in an electrically driven cavity material system. We consider a semiconductor layer embedded in a cavity and coupled to external leads and a bath of acoustic phonons, where dc pumping leads to the buildup of a coherent intracavity field through light-matter coupling. We determine the resulting nonequilibrium steady state self-consistently and show that, above threshold, the coupled system settles into a stable time-periodic limit cycle with a field amplitude set by the cavity quality factor and dissipation. This emergent periodic field Floquet-dresses the electronic bands and modifies the anomalous Hall response of a material with broken time-reversal symmetry. We demonstrate that the resulting Hall conductivity can be directly probed via in-plane dc transport measurements. Our work establishes a route to self organized Floquet band reconstruction and geometric transport without external laser illumination, highlighting cavity driven steady states as a platform for electrically controlled nonequilibrium phases.
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All authors Christopher Yang, Gil Refael, Mark S. Rudner, Iliya Esin

Materials Science

Element-Specific Solute Trapping and Grain Structure Evolution during Laser Powder Bed Fusion of Multicomponent Alloys

Xinxin Yao, James Hanagan, Md Shafiqur Rahman Jame et al. (+5 more)

Under the rapid solidification conditions of laser powder bed fusion (LPBF), solute trapping manifests in an element-specific manner, altering nonequilibrium partitioning, constitutional undercooling, and grain selection behavior in multicomponent alloys. Here, we elucidate the mechanisms by which element-specific solute trapping governs nucleation behavior and grain structure evolution during LPBF demonstrated on a SS316L. This requires quantitative description of nonequilibrium multicomponent thermodynamics and grain evolution across broad LPBF solidification conditions, which is achieved through a CALPHAD-informed Gaussian Process Regression (GPR)-assisted Phase-Field (PF) approach. The predicted transitions in grain morphology and grain size are validated against EBSD measurements under multiple LPBF processing conditions. Results demonstrate that increasing solidification rate drives a composition-dependent transition from solute diffusion-controlled nucleation to solute trapping-controlled grain growth, where nonequilibrium solute redistribution intensified by solute trapping suppresses equiaxed grain formation despite high cooling rates. Quantitative decomposition of multicomponent undercooling further reveals distinct element-specific sensitivities to solute trapping, where C, Cr, and Mo remain dominant contributors to the overall undercooling, while the undercooling contribution of low-partitioning elements such as S and P are strongly suppressed relative to their equilibrium values under rapid solidification conditions. These results reveal how element-specific solute trapping governs grain selection in multicomponent alloys, providing a mechanistic basis for alloy design under nonequilibrium solidification conditions.
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All authors Xinxin Yao, James Hanagan, Md Shafiqur Rahman Jame, Mallikharjun Marrey, Mohsen Taheri Andani, Raymundo Arróyave, Veera Sundararaghavan, Lei Chen

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

Superconducting triode effect in a quantum-dot Josephson junction with a biased top gate

Yu-Hang Li, Xiaan Du, Hua Jiang et al. (+1 more)

Non-reciprocal supercurrents enable non-dissipative rectification, holding great promise for superconducting electronics. Conventionally, this non-reciprocity, termed the superconducting diode effect, requires the simultaneous breaking of time-reversal and parity symmetries. Here, we propose a superconducting triode effect in an asymmetric quantum-dot Josephson junction coupled to an additional metallic top gate, which breaks the parity symmetry while explicitly preserving time-reversal symmetry. We demonstrate that the supercurrent across this junction exhibits a strong non-reciprocal effect that can be continuously manipulated via the top gate to achieve an ideal unidirectional supercurrent, thus manifesting a superconducting triode effect. Furthermore, under radio-frequency radiation, this junction exhibits highly asymmetric Shapiro steps, realizing fully quantized supercurrent rectification. Our work not only provides an alternative physical mechanism for the superconducting diode effect observed in Josephson junctions with explicit time-reversal symmetry, but also introduces a new tuning knob to manipulate supercurrent non-reciprocity.
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All authors Yu-Hang Li, Xiaan Du, Hua Jiang, X. C. Xie

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

Quantum Thermal Logic Gates

Shuvadip Ghosh, Arnab Ghosh, Bivas Dutta et al. (+1 more)

We propose a new concept for quantum thermal logic gates – analogous to classical electronic logic gates – that exploit the heat current in a coupled quantum-dot system tunnel-coupled to metallic thermal reservoirs for logic operations in quantum circuits. We obtained a remarkable one-to-one correspondence with the structure of classical electronic logic gate circuits. An experimental setup is presented that demonstrates a realizable nano-electronic quantum circuit architecture for implementing such quantum thermal logic operations.
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All authors Shuvadip Ghosh, Arnab Ghosh, Bivas Dutta, Papiya Maity

Materials Science

PolyGraphPy: A unified Python framework for atomistic simulation and machine learning-driven polymer design

João G. C. S. Duarte, Shruti Venkatram, Morgan Cencer et al. (+2 more)

Polymers are indispensable materials with daily applications ranging from electronics to medicine, owing to their versatility, which can be tailored by adjusting their chemical composition and architecture. The design space for these compounds is vast and governed by factors such as monomer classes, copolymer configurations (e.g., linear, branched, random, and alternating), chain size, stoichiometry, and material properties (e.g., density, refractive index, solubility, and Poisson's ratio). Thus, its exploration requires efficient computational methodologies for polymer science. To address this challenge, this paper introduces PolyGraphPy, an open-source, unified Python framework that integrates atomistic simulations with machine learning for accurate property prediction and property-guided polymer design. The framework automates quantum mechanics calculations using Density Functional Tight Binding (DFTB+) to efficiently construct structured datasets for monomers, homopolymers, and alternating copolymers. For property prediction, PolyGraphPy employs Bayesian Graph Neural Networks (GNNs) utilizing stochastic graph representations to predict target properties-such as static polarizability, while providing robust uncertainty quantification. Furthermore, the platform incorporates two complementary generative models for the de novo design of targeted molecules: a SELFIES-based Generative Pre-trained Transformer (GPT) and a Genetic Algorithm (GA) based on BRICS graph fragmentation. Demonstrated on a dataset of acrylates, PolyGraphPy provides a highly customizable, end-to-end pipeline that reduces computational costs and accelerates data-driven polymer informatics.
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All authors João G. C. S. Duarte, Shruti Venkatram, Morgan Cencer, Traian Dumitricǎ, Ketson R. M. dos Santos

Materials Science

Optical Signature of Moiré Superlattices Formed by Twisted SrTiO$_3$ Membranes

T. A. M. Ragib Shahriar, Fumikazu Murakami, Xing He et al. (+11 more)

Moiré superlattices formed at the interfaces of mismatched lattices have attracted significant interest over the past decade due to their large tunability of band parameters and interactions among electrons, spins, and lattices. Superlattices made from twisted perovskite oxides may have strong structure and potential modulation, but evidence of such modulation over macroscopic areas, particularly at large twisting angles, has not been clearly demonstrated so far. Here, we fabricated millimeter-scale twisted oxide bilayers at $36^\circ$ angle, close to the simple coincidence site lattice condition $\Sigma5$, from freestanding SrTiO$_3$ membranes. We discovered new low-frequency vibrational modes whose Raman activity, according to molecular dynamics simulations, is greatly enhanced by an asymmetric, twisted interface between the SrO and TiO$_2$ layers. Such an interface is energetically favorable from first-principles calculations and is corroborated by the observation of strong second harmonic generation from the interface comparable to that from the SrTiO$_3$ surface throughout the bilayer region. The results are consistent with interlayer coupling enhanced by high-temperature annealing and confirmed by cross-sectional scanning transmission electron microscopy imaging. Our work sheds light on the structural behavior of twisted oxides and provides directions for tuning their phononic and nonlinear optical properties in future studies.
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All authors T. A. M. Ragib Shahriar, Fumikazu Murakami, Xing He, Konnor Koons, Xinyan Li, Bumseop Kim, Shihan Qin, Varun Harbola, Jochen Mannhart, Yimo Han, Ruijuan Xu, Shengxi Huang, Andrew Rappe, Hanyu Zhu

Materials Science

Endowing variational phase-field fracture models with custom strength criteria

Roberto Alessi, Matteo Brunetti, Roshan Udaram Patil et al. (+1 more)

By now, several approaches have been proposed to endow phase-field fracture models with the ability to describe crack nucleation under multiaxial stress states. These include techniques for splitting the free energy, direct modifications of the phase-field driving or resisting forces that sacrifice the variational structure of the problem, and the introduction of additional internal variables, such as plastic strains or other nonlinear strains. In this paper, we propose a fundamentally different strategy for incorporating arbitrary elastic domains into phase-field fracture models, formulated within the variational framework of generalized standard materials. The proposed approach relies on letting the dissipation potential depend on the current state of the material. In this way, the variational structure of the problem is preserved, while elastic degradation and the strength criterion remain two distinct and independently controllable aspects of the material response. Simple yet representative models are presented and thoroughly discussed to demonstrate the effectiveness of the proposed methodology. The resulting evolution of the elastic domain is investigated in both strain and stress spaces. Moreover, numerical simulations demonstrate a range of crack nucleation processes under multiaxial loading conditions for various analytical strength surfaces. This work paves the way for future developments and applications in several directions.
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All authors Roberto Alessi, Matteo Brunetti, Roshan Udaram Patil, Jacinto Ulloa

Materials Science

Stacking-Dependent Magnetism and Tunable Half-Metallicity in Bilayer Janus 1T-MnSSe

Jakkapat Seeyangnok, Udomsilp Pinsook and Graeme J. Ackland

We investigate the structural, electronic, and magnetic properties of bilayer Janus 1T-MnSSe using first-principles calculations. Various AA- and AB-type stacking configurations are considered to examine the influence of interlayer registry on magnetic ordering and exchange interactions. The nonmagnetic state is unstable for all stackings, confirming intrinsic magnetism. The AA2 stacking is identified as the ground state and exhibits A-type antiferromagnetic ordering, indicating antiferromagnetic interlayer coupling. Monte Carlo simulations based on an effective Ising model reveal enhanced magnetic transition temperatures in the bilayer relative to the monolayer, with Néel temperatures above 300~K for antiferromagnetic stackings and Curie temperatures up to 250~K for ferromagnetic phases. Several stacking configurations exhibit robust half-metallic ferromagnetism with nearly 100% spin polarization at the Fermi level. Moreover, the half-metallic state can be tuned and ultimately transformed into a metallic ferromagnetic phase through carrier doping and biaxial strain. These findings establish bilayer MnSSe as a promising platform for controllable interlayer magnetism and spintronic applications in two-dimensional materials.
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