Peer Revenue Impact factor: volatile

Papers

Fresh from arXiv, typeset properly. Highlighted words trade on the market.

Physics Condensed Matter Materials Science

cond-mat.mtrl-sci Watch Materials Science

Wednesday 22 October

Materials Science

Spin injection and emission helicity switching in a 2D perovskite/WSe2 heterostructure

Jakub Jasinski, Francesco Gucci, Thomas Brumme et al. (+16 more)

The initialization and control of a long-lived spin population in lead halide perovskites are prerequisites for their use in spintronic applications. Here, we demonstrate circular polarization of the interlayer exciton emission in a (BA)2PbI4/WSe2 monolayer heterostructure. The helicity of this emission is controlled by tuning the energy of the excitation laser through the manifold of exciton resonances of the WSe2 monolayer, together with an emerging interlayer absorption feature of the heterostructure. Theoretical calculations show that this resonance arises from hybridized (BA)2PbI4/WSe2 states in the valence band. This hybrid character enables its observation in both linear absorption and ultrafast pump-probe spectroscopies, and plays a key role in controlling the sign of the helicity of the interlayer exciton emission. The tunable spin polarization demonstrated here, with the WSe2 monolayer effectively acting as a tunable spin filter, represents an important step toward the use of 2D perovskites in opto-spintronic applications.
Read the full abstract

All authors Jakub Jasinski, Francesco Gucci, Thomas Brumme, Swaroop Palai, Armando Genco, Alessandro Baserga, Jonas D. Ziegler, Takashi Taniguchi, Kenji Watanabe, Mateusz Dyksik, Christoph Gadermaier, Michal Baranowski, Duncan K. Maude, Alexey Chernikov, Giulio Cerullo, Agnieszka Kuc, Stefano Dal Conte, Paulina Plochocka, Alessandro Surrente

Materials Science

Synergistic effects of rare-earth doping on the magnetic properties of orthochromates: A machine learning approach

Guanping Xu, Zirui Zhao, Muqing Su et al. (+1 more)

Multiferroic materials, particularly rare-earth orthochromates (RECrO$_3$), have garnered significant interest due to their unique magnetic and electric-polar properties, making them promising candidates for multifunctional devices. Although extensive research has been conducted on their antiferromagnetic (AFM) transition temperature (N$\acute{\textrm{e}}$el temperature, $T_\textrm{N}$), ferroelectricity, and piezoelectricity, the effects of doping and substitution of rare-earth (RE) elements on these properties remain insufficiently explored. In this study, convolutional neural networks (CNNs) were employed to predict and analyze the physical properties of RECrO$_3$ compounds under various doping scenarios. Experimental and literature data were integrated to train machine learning models, enabling accurate predictions of $T_\textrm{N}$, besides remanent polarization ($P_\textrm{r}$) and piezoelectric coefficients ($d_{33}$). The results indicate that doping with specific RE elements significantly impacts $T_\textrm{N}$, with optimal doping levels identified for enhanced performance. Furthermore, high-entropy RECrO$_3$ compounds were systematically analyzed, demonstrating how the inclusion of multiple RE elements influences magnetic properties. This work establishes a robust framework for predicting and optimizing the properties of RECrO$_3$ materials, offering valuable insights into their potential applications in energy storage and sensor technologies.
Read the full abstract

All authors Guanping Xu, Zirui Zhao, Muqing Su, Hai-Feng Li

Materials Science

Exciton thermal radiation from structure-sorted carbon nanotube membranes

Akiteru Takahashi, Kaichi Teranishi, Shonosuke Takaichi et al. (+2 more)

Owing to their small binding energies, excitons in bulk semiconductors typically exhibit a sharp optical peak at low temperatures only. This limitation can be overcome by single-walled carbon nanotubes (SWCNTs) and other low-dimensional semiconductors with highly enhanced exciton binding energies. Exciton thermal radiation, which can potentially be exploited for selective thermal emission and energy harvesting, has been recently observed in individual SWCNTs heated under photoirradiation. However, whether macroscale-SWCNT assemblies can emit exciton thermal radiation under conduction heating remains unclear and constitutes an important challenge for practical applications. Herein, we observed peaked exciton thermal radiation from structure-sorted SWCNT membranes. Transmission spectroscopy showed robust exciton resonance at high temperatures, resulting in clear exciton resonance in the thermal radiation band. The absolute emissivity spectra of the membranes were determined at 850 K. Exciton dominance suppresses the contribution of thermal free carriers to the infrared absorption/emission spectra, maintaining the transparency below the optical gap even at elevated temperatures. These phenomena are not observed in bulk semiconductors, highlighting the structure-sorted SWCNT membranes as unique semiconductors leveraging stable exciton resonances at elevated temperatures.
Read the full abstract

All authors Akiteru Takahashi, Kaichi Teranishi, Shonosuke Takaichi, Taishi Nishihara, Yuhei Miyauchi

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

Identifying the Catalytic Descriptor of Single-Atom Catalysts in Nitrate Reduction Reaction: An Interpretable Machine-Learning Method

Zhen Zhu, Shan Gao, Jing Zhang et al. (+3 more)

Elucidating the catalytic descriptor that accurately characterizes the structure-activity relationships of typical catalysts for various important heterogeneous catalytic reactions is pivotal for designing high-efficient catalytic systems. Here, an interpretable machine learning technique was employed to identify the key determinants governing the nitrate reduction reaction ($\rm NO_3RR$) performance across 286 single-atom catalysts (SACs) with the active sites anchored on double-vacancy $\rm BC_3$ monolayers. Through Shapley Additive Explanations (SHAP) analysis with reliable predictive accuracy, we quantitatively demonstrated that, favorable $\rm NO_3RR$ activity stems from a delicate balance among three critical factors: low $\rm N_V$, moderate $\rm D_N$, and specific doping patterns. Building upon these insights, we established a descriptor ($\psi$) that integrates the intrinsic catalytic properties and the intermediate O-N-H angle ($\theta$), effectively capturing the underlying structure-activity relationship. Guided by this, we further identified 16 promising catalysts with predicted low limiting potential ($U_{\rm L}$). Importantly, these catalysts are composed of cost-effective non-precious metal elements and are predicted to surpass most reported catalysts, with the best-performing Ti-V-1N1 is predicted to have an ultra-low $U_{\rm L}$ of $-0.10$ V.
Read the full abstract

All authors Zhen Zhu, Shan Gao, Jing Zhang, Xuxin Kang, Shunfang Li, Xiangmei Duan

Materials Science

Synthesizability Prediction of Crystalline Structures with Structure-Aware Feature Learning and Uncertainty Quantification

Danial Ebrahimzadeh, Sarah Sharif and Yaser Mike Banad

Predicting which hypothetical inorganic crystals can be experimentally realized remains a central challenge in accelerating materials discovery. SyntheFormer is a positive-unlabeled framework that learns synthesizability directly from crystal structure, combining Fourier-transformed crystal properties (FTCP) representation with structure-aware feature extraction, Random-Forest feature selection, and a compact deep MLP classifier. The model is trained on historical data from 2011 through 2018 and evaluated prospectively on future years from 2019 to 2025, where the positive class constitutes only 1.02 percent of samples. Under this temporally separated evaluation, SyntheFormer achieves a test AUC of 0.735, AUPRC of 0.099 and 97.6 percent recall at 94.2 percent coverage with dual-threshold calibration. Direct prospective validation supports this result as two materials that were unlabeled at the time of data curation, Y6Fe(SiS7)2 and BaYb2F8, were assigned high SyntheFormer scores (0.961 and 0.753, respectively) and were subsequently reported experimentally. Crucially, the model recovers experimentally confirmed metastable compounds that lie far from the convex hull and simultaneously assigns low scores to many thermodynamically stable yet unsynthesized candidates, demonstrating that stability alone is insufficient to predict experimental attainability.
Read the full abstract

Materials Science

High-Efficiency Nonrelativistic Charge-Spin Conversion in X-Type Antiferromagnets

Jiabin Wang, Wancheng Zhang, Zhenhua Zhang et al. (+3 more)

Antiferromagnetic materials with spin splitting have attracted considerable attention for their symmetry-enabled anisotropic spin textures that sustain a zero net magnetization, thereby facilitating efficient spin-current generation. In this work, the highly efficient generation of nonrelativistic spin currents is demonstrated to be facilitated by the distinctive Fermi surface geometry of X-type collinear antiferromagnets. As a prototype conducting X-type antiferromagnet, the Fermi surface of $\beta-\mathrm{Fe_2PO_5}$ exhibits a distinct $d$-wave altermagnetic characteristic, which compresses into a nearly X-shaped configuration. This results in highly efficient spin currents, achieving a charge-spin conversion efficiency of up to 90%. Moreover, the spin current polarization is controlled by the orientation of the Néel vector. When the Néel vector tilts to the out-of-plane direction, an in-plane injected charge current can generate a special spin current component with both spin polarization and propagation along the out-of-plane direction, whose charge-spin conversion efficiency substantially exceeds that of known ferromagnets, altermagnets, noncollinear antiferromagnets, and low-symmetry materials. The highly efficient charge-spin conversion in X-type antiferromagnets provides a novel and highly effective spin source system for the development of low-power spintronic devices.
Read the full abstract

All authors Jiabin Wang, Wancheng Zhang, Zhenhua Zhang, Rui Xiong, Yong Liu, Zhihong Lu

Materials Science

Transient Absorption Spectroscopy of NbOI$_2$

Salman Ahsanullah, Neema Rafizadeh and Hui Zhao

NbOI$_2$ has recently emerged as a new van der Waals material combining semiconducting behavior with intrinsic in plane ferroelectricity and pronounced transport and optical anisotropy. However, its photocarrier dynamics remain largely unexplored. Here we report transient absorption spectroscopy of NbOI$_2$ using femtosecond pump probe reflectance measurements. A pronounced transient absorption feature is observed near the 2.34 eV excitonic resonance, arising from photocarrier induced excitonic energy shifts and saturation. The decay dynamics reveal an exciton lifetime of several tens of picoseconds and show density-dependent behavior consistent with exciton exciton annihilation and defect-assisted Auger recombination, yielding a rate of 0.4 cm$^2$ s$^{-1}$, which is comparable to that in monolayer transition metal dichalcogenides. Polarization resolved measurements further reveal a pronounced in-plane anisotropy in the transient response that follows the linear absorption anisotropy. These findings provide fundamental insight into photocarrier dynamics in NbOI$_2$ and establish key parameters for understanding and exploiting its optoelectronic behavior.
Read the full abstract

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

Control of out-of-plane anti-damping spin torque with a canted ferromagnetic spin source

Xiaoxi Huang, Daniel A. Pharis, Hang Zhou et al. (+13 more)

To achieve efficient anti-damping switching of nanoscale magnetic memories with perpendicular magnetic anisotropy using spin-orbit torque requires that the anti-damping spin-orbit torque have a strong out-of-plane component. The spin anomalous Hall effect and the planar Hall effect spin current produced by a ferromagnetic layer are candidate mechanisms for producing such an out-of-plane anti-damping torque, but both require that the magnetic moment of the spin source layer be canted partly out of the sample plane at zero applied magnetic field. Here we demonstrate such a canted configuration for a ferromagnetic SrRuO3 layer and we characterize all vector components of the torque that it produces, including non-zero out-of-plane anti-damping torques. We verify that the out-of-plane spin component can be tuned by the orientation of magnetic moment, with significant contributions from both the spin anomalous Hall effect and the planar Hall effect spin current.
Read the full abstract

All authors Xiaoxi Huang, Daniel A. Pharis, Hang Zhou, Zishen Tian, Thow Min Jerald Cham, Kyoungjun Lee, Yilin Evan Li, Chaoyang Wang, Yuhan Liang, Maciej Olszewski, Di Yi, Chang-Beom Eom, Darrell G. Schlom, Lane W. Martin, Ding-Fu Shao, Daniel C. Ralph

Tuesday 21 October

Materials Science

Vertex and front-tracking methods for the modeling of microstructure evolution at the solid state: a brief review

Marc Bernacki

In mesoscopic scale microstructure evolution modeling, two primary numerical frameworks are used: Front-Capturing (FC) and Front-Tracking (FT) ones. FC models, like phase-field or level-set methods, indirectly define interfaces by tracking field variable changes. On the contrary, FT models explicitly define interfaces using interconnected segments or surfaces. In historical FT methodologies, Vertex models were first developed and consider the description of the evolution of polygonal structures in terms of the motion of points where multiple boundaries meet. Globally, FT-type approaches, often associated with Lagrangian movement, enhance spatial resolution in 3D surfacic and 2D lineic problems using techniques derived from finite element meshing and remeshing algorithms. These efficient approaches, by nature, are well adapted to physical mechanisms correlated to interface properties and geometries. They also face challenges in managing complex topological events, especially in 3D. However, recent advances highlight their potential in computational efficiency and analysis of mobility and energy properties, with possible applications in intragranular phenomena.
Read the full abstract

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

Many-Body Perturbation Theory for Driven Dissipative Quasiparticle Flows and Fluctuations

Thomas Blommel, Enrico Perfetto, Gianluca Stefanucci et al. (+1 more)

We present a unified many-body perturbation theory for open quantum systems, that treats dissipation, correlations, and external driving on equal footing. Using a Keldysh-Lindblad formalism, we introduce diagrammatic treatment of dissipative interaction lines representing quasiparticle flows and fluctuations. Two new Feynman rules render the evaluation of dissipative diagrams compact and systematically improvable, while preserving the Keldysh and anti-Hermitian symmetries of the closed-system theory. Consequently, the structure of the Kadanoff-Baym equations (KBE) remains unchanged, enabling existing numerical methods to be directly applied. To illustrate this, we derive dissipative versions of the second Born and $GW$ approximations, identifying the physical content of the self-energy components. Moreover, we demonstrate that time-linear approximations to the full KBE retain their closed structure and can be efficiently used to simulate relaxation and decoherence dynamics. The impact of dissipation-induced correlations is illustrated in the driven Haldane model, where quasiparticles exhibit nontrivial stabilization and acquire lifetimes that far exceed those of the bare system. This framework establishes a general route toward first-principles modeling of correlated, driven, and dissipative quantum materials.
Read the full abstract

All authors Thomas Blommel, Enrico Perfetto, Gianluca Stefanucci, Vojtech Vlcek

Materials Science · Cross-listed from physics.ins-det

Quantitative measurement of magnetic dichroic signals at sub-nanometer to atomic scale resolution conditions

Sharath Kumar Manjeshwar Sathyanath, Anna L. Ravensburg, Vassilios Kapaklis et al. (+3 more)

When aiming for atomic resolution electron magnetic circular dichroism (EMCD) in STEM mode, the high convergence angle of the electron probe can lead to unforeseen artefacts and strong reductions of the signal to noise ratio (SNR) in the measurement of magnetic magnitudes. In this work, the EMCD signal is measured in STEM mode at semi-convergence angles ranging from \alpha=\ 2-10\ mrad\ using iron samples with high structural perfection. We observe that the relative EMCD signal remains very similar for all convergence angles, which is in good agreement with simulations. The improvement in the signal-to-noise ratio as compared to earlier works is due to better crystalline quality of the Fe sample, high control of the sample orientation, better control over sample thickness, and factors such as higher beam current and the use of a fast and sensitive hybrid-pixel electron detector. One of the key factors to remove experimental ambivalences is the use of an acquisition geometry where the two conjugate EMCD spectra are acquired simultaneously. Furthermore the high crystalline quality Fe sample enables the acquisition of statistical entities of spectra at the same sample orientation, which in turn results in high SNR EMCD signals. We obtain high SNR EMCD signals for all semi convergence angles and could measure the orbital to spin magnetic moment ratio ml/ms with high precision. We observed that at high convergence angles, the ml/ms ratio gets sensitive to minute changes in sample orientation.
Read the full abstract

All authors Sharath Kumar Manjeshwar Sathyanath, Anna L. Ravensburg, Vassilios Kapaklis, Jan Rusz, Björgvin Hjörvarsson, Klaus Leifer

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

Ab Initio Free Energy Surfaces for Coupled Ion-Electron Transfer

Ethan Abraham, Martin Z. Bazant and Troy Van Voorhis

Although coupled ion-electron transfer (CIET) has emerged as a powerful framework to rationalize the kinetics of Faradaic reactions, its mechanism has lacked a fully microscopic, first-principles description. Here we show that the coupling of electron-transfer to ion-transfer can be understood as an extension of Marcus theory in which the ensemble of diabatic nuclear configurations is conditioned on a classical collective variable describing the interfacial anisotropy. This formalism enables direct construction of the CIET free-energy surface from constrained ab initio trajectories, providing a first-principles route to electrochemical current-overpotential relations. We demonstrate this method for CO2 redox on a gold electrode and find that the resulting two-dimensional saddle-point barriers differ substantially from one-dimensional treatments that consider only electron- or ion-transfer coordinates individually.
Read the full abstract

Materials Science

First-principles calculation of electronic and topological properties of low-dimensional tellurium

Gabriel Elyas Gama Araujo and Andreia Luisa da Rosa

We present a comprehensive first-principles investigation of the structural, electronic, vibrational, and topological properties of tellurium across its dimensional hierarchy, including bulk trigonal Te-I, two-dimensional tellurene polymorphs, and one-dimensional helical nanowires. Using density functional theory with full inclusion of spin-orbit coupling, we confirm that bulk Te-I is a narrow-gap semiconductor hosting Weyl nodes arising from broken inversion symmetry and degenerate phonon modes suggestive of chiral phonon behavior. In contrast, two-dimensional alpha and beta-tellurene are found to be topologically trivial, with no spin-orbit-driven band inversion in the occupied manifold. Beyond these established phases, we find that buckled kagome and buckled square tellurene lattices exhibit a nontrivial two-dimensional topology of the occupied electronic bands, indicating incipient quantum spin Hall character in metallic systems. In contrast, one-side hydrogen-passivated hexagonal tellurene realizes a fully gapped quantum spin Hall phase with a robust Z2 = 1 invariant, preserved under applied strain and chemical functionalization. In the one-dimensional limit, helical tellurium nanowires preserve chirality and host edge-localized states accompanied by pronounced anisotropy in carrier effective masses. These results establish tellurium as a highly tunable platform for engineering topological phenomena across dimensionality, bridging three-dimensional Weyl physics, two-dimensional quantum spin Hall and incipient Z2 phases, and one-dimensional helical systems.
Read the full abstract

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

iDART: Interferometric Dual-AC Resonance Tracking nano-electromechanical mapping

J. Bemis, F. Wunderwald, U. Schroeder et al. (+3 more)

Piezoresponse force microscopy (PFM) has established itself as a very successful and reliable imaging and spectroscopic tool for measuring a wide variety of nanoscale electromechanical functionalities. Quantitative imaging of nanoscale electromechanical phenomena requires high sensitivity while avoiding artifacts induced by large drive biases. Conventional PFM often relies on high voltages to overcome optical detection noise, leading to various non-ideal effects including electrostatic crosstalk, Joule heating, and tip-induced switching. To mitigate this situation, we introduce interferometrically detected, resonance-enhanced dual AC resonance tracking (iDART), which combines femtometer-scale displacement sensitivity of quadrature phase differential interferometry with contact resonance amplification. Through this combination, iDART achieves 10x or greater signal-to-noise improvement over current state of the art PFM approaches including both single frequency interferometric PFM or conventional, resonance enhanced PFM using optical beam detection. In this work, we demonstrate a >10x improvement of imaging sensitivity on PZT and Y-HfO. Switching spectroscopy shows similar improvements, where further demonstrates reliable hysteresis loops at small biases, mitigating nonlinearities and device failures that can occur at higher excitation amplitudes. These results position iDART as a powerful approach for probing conventional ferroelectrics with extremely high signal to noise down to weak piezoelectric systems, extending functional imaging capabilities to thin films, 2D ferroelectrics, beyond-CMOS technologies and bio-materials.
Read the full abstract

All authors J. Bemis, F. Wunderwald, U. Schroeder, X. Xu, A. Gruverman, R. Proksch

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

Machine-learned domain partitioning for computationally efficient coupling of continuum and particle simulations of membrane fabrication

Matthias Busch, Gregor Häfner, Jiayu Xie et al. (+4 more)

All simulation approaches eventually face limits in computational scalability when applied to large spatiotemporal domains. This challenge becomes especially apparent in molecular-level particle simulations, where high spatial and temporal resolution leads to rapidly increasing computational demands. To overcome these limitations, hybrid methods that combine simulations with different levels of resolution offer a promising solution. In this context, we present a machine learning-based decision model that dynamically selects between simulation methods at runtime. The model is built around a Multilayer perceptron (MLP) that predicts the expected discrepancy between particle and continuum simulation results, enabling the localized use of high-fidelity particle simulations only where they are expected to add value. This concurrent approach is applied to the simulation of membrane fabrication processes, where a particle simulation is coupled with a continuum model. This article describes the architecture of the decision model and its integration into the simulation workflow, enabling efficient, scalable, and adaptive multiscale simulations.
Read the full abstract

All authors Matthias Busch, Gregor Häfner, Jiayu Xie, Marius Tacke, Marcus Müller, Christian J. Cyron, Roland C. Aydin

Materials Science

Decoding optoelectronic behavior in X$_3$BI$_3$ antiperovskite derivatives through many-body perturbation theory

Ayan Chakravorty, Surajit Adhikari and Priya Johari

Antiperovskite derivatives have emerged as promising candidates for optoelectronic applications. However, due to the significant computational cost, their excitonic and polaronic properties remain underexplored despite being critical for optoelectronic performance. Here, we present the structural, electronic, optical, excitonic, and polaronic properties of a series of antiperovskite derivatives with the chemical formula X$_{3}$BI$_{3}$ (X = Ca, Sr; B = P, As, Sb, Bi) using state-of-the-art first-principles calculations. All the compounds exhibit direct bandgaps with G$_{0}$W$_{0}$@PBE bandgap ranging from 2.42 to 3.02 eV, optimal for efficient light absorption with minimal energy loss. Exciton binding energies (0.258-0.318 eV) indicate moderate Coulomb attraction, favoring exciton dissociation. Employing the Feynman polaron model, we established the polaronic properties, where weak to intermediate carrier-phonon coupling was observed, with polaron mobilities reaching values up to 37.19 cm$^{2}$V$^{-1}$s$^{-1}$. These properties establish X$_{3}$BI$_{3}$ materials as viable candidates for next-generation optoelectronic devices.
Read the full abstract

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

Generating ferro-spinetic polarizations in altermagnetic insulators

Toshihiro Sato, Mengli Hu, Ion Cosma Fulga et al. (+5 more)

Altermagnets are a novel class of fully spin-compensated magnetic materials that nevertheless have spin-split electronic bands, offering novel perspectives for spintronics applications. Based on a rigorous analysis of altermagnetic many-body models and their symmetry we establish the important role of two fundamental types of polarizations in altermagnetic insulators: the charge and the spinetic one, where the latter corresponds to a macroscopic spin-displacement field. First principles calculations confirm and quantify their presence in real materials. The two polarizations are directly coupled and emerge in orthogonal directions when inversion symmetry is broken, either by the system developing a spontaneously ferroelectric polarization (in ferroelectric altermagnets), or by a charge displacement induced by an external electric field (for inversion invariant altermagnetic insulators). This presence of large and switchable spin accumulations constitute an attractive fundamental feature of altermagnetic insulators.
Read the full abstract

All authors Toshihiro Sato, Mengli Hu, Ion Cosma Fulga, Oleg Janson, Jorge I. Facio, Alessandro Stroppa, Fakher F. Assaad, Jeroen van den Brink

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

Haerter-Shastry kinetic magnetism and metallicity in the triangular Hubbard model

Sogoud Sherif, Prakash Sharma, Aman Kumar et al. (+1 more)

The fermionic Hubbard model, when combined with frustration, associated with the breaking of particle-hole symmetry, harbors a rich phase diagram. Theoretical findings associated with the nature of magnetism and metallicity across this phase diagram are now being actively investigated in triangular Hubbard cold atom and solid-state (moiré) based emulators. Building on the theoretical work of Haerter and Shastry, we explore the impact of kinetically frustrated magnetism, a phenomenon where antiferromagnetic order emerges without any underlying magnetic interactions, at finite hole density. We numerically study the infinite-$U$ triangular Hubbard model using the density matrix renormalization group algorithm and estimate the stability of the kinetically induced $120^{\circ}$ antiferromagnetic state to hole doping. Beyond the Haerter-Shastry regime, we find an intermediate phase with multimer (involving multiple correlated spins) stripes that eventually gives way to a paramagnet. We also find evidence of gapless charge excitations (metallicity) throughout the phase diagram for finite hole density. We discuss the implications at large, but finite, values of $U/t$, and investigate whether kinetic magnetism and superexchange collaborate or compete.
Read the full abstract

All authors Sogoud Sherif, Prakash Sharma, Aman Kumar, Hitesh J. Changlani

Materials Science

An Encoder-Decoder Foundation Chemical Language Model for Generative Polymer Design

Harikrishna Sahu, Wei Xiong, Anagha Savit et al. (+2 more)

Traditional machine learning has advanced polymer discovery, yet direct generation of chemically valid and synthesizable polymers without exhaustive enumeration remains a challenge. Here we present polyT5, an encoder-decoder chemical language model based on the T5 architecture, trained to understand and generate polymer structures. polyT5 enables both property prediction and the targeted generation of polymers conditioned on desired property values. We demonstrate its utility for dielectric polymer design, seeking candidates with dielectric constant >3, bandgap >4 eV, and glass transition temperature >400 K, alongside melt-processability and solubility requirements. From over 20,000 generated promising candidates, one was experimentally synthesized and validated, showing strong agreement with predictions. To further enhance usability, we integrated polyT5 within an agentic AI framework that couples it with a general-purpose LLM, allowing natural language interaction for property prediction and generative design. Together, these advances establish a versatile and accessible framework for accelerated polymer discovery.
Read the full abstract

All authors Harikrishna Sahu, Wei Xiong, Anagha Savit, Shivank S Shukla, Rampi Ramprasad

Materials Science

Scale-bridging dislocation plasticity in MgO at room temperature

Jiawen Zhang, Zhangtao Li, Yuwei Zhang et al. (+7 more)

Dislocations in ceramics have recently gained renewed research interest, in contrast to the traditional belief that ceramics are inherently brittle. Understanding dislocation mechanics in representative oxides is beneficial for effective dislocation engineering. Here, we use MgO single crystals with mechanically seeded dislocation densities from about 10 to the power of 12 to about 10 to the power of 15 per square meter to investigate the mechanical behavior such as yield and fracture. Micro-pillar compression tests reveal a dislocation density dependent yield strength, mediated by the varying dominating dislocation mechanisms from nucleation to multiplication/motion. In situ TEM compression measurements highlight the dislocation-seeded samples can achieve a much-improved compressive plastic strain beyond about 70%, with a high yield strength of about 2.35 GPa (diameter of about 400 nm), indicating size effect. Complementary bulk compression tests, along with digital image correlation (DIC), demonstrate a consistent dislocation-mediated deformation and a notable size effect, with bulk samples exhibiting much reduced yield strength (about 120 MPa) compared to the nano-/micro-pillars. Using three-dimensional Discrete Dislocation Dynamics (3D-DDD) simulation, we further qualitatively analyze the collective dislocation activities (slip events) and work hardening during compression. This study provides new insights into dislocation-mediated plasticity in MgO, across different length scales, by systematically tuning dislocation density.
Read the full abstract

All authors Jiawen Zhang, Zhangtao Li, Yuwei Zhang, Hendrik Holz, James P. Best, Oliver Preuß, Zhenyong Chen, Yinan Cui, Xufei Fang, Wenjun Lu

Materials Science

Interplay of Magnetism, Band Gap Tuning, Optical, and Thermoelectric Responses in Fe-Doped YMnO$_3$: Insights from First-Principles Calculations

Kazi Mazba Kamal and Alamgir Kabir

The hexagonal multiferroic oxide YMnO$_3$ has demonstrated applications in various fields and is widely researched due to its interesting properties. Since Mn(3d)–O(2p) interactions predominate close to the Fermi level, doping in the B-site (Mn) with Fe provides a way to modulate the band gap and magnetic order of YMnO$_3$. The need for a lead-free ferroelectric material with a narrow band gap is crucial for absorbing a wide range of the solar spectrum. Density functional theory calculations were carried out using GGA and meta-GGA (for an accurate description of the band gap) exchange correlation functional for the Fe-doped YMnO$_3$ multiferroics. Various magnetic configurations were analyzed, finding collinear G-type AFM as the least energy state. The hexagonal lattice is retained after Fe doping with slight distortions and a change in lattice constants. Fe doping reduces spin frustration and induces magnetization, while reducing the band gap from 1.88 eV for pure to 1.19 eV for a 25 percent doping concentration. Additionally, Fe doping exhibits an enhanced dielectric response, characterized by an increase in the static dielectric constant and the presence of strong absorption peaks in the visible and UV energy ranges. Thermoelectric studies illustrate enhanced conductivity due to increased charge carriers induced by doping. In summary, first-principles predictions of structural, electronic, optical, and transport behavior in Fe-doped YMnO$_3$ provide a foundation for tailoring this oxide in photovoltaic, thermoelectric, and optoelectronic applications.
Read the full abstract

Materials Science

Hydrogen redistribution in Zr-base cladding under gradients in temperature and stress

Lars O. Jernkvist and Ali R. Massih

Computational models are used here for simulating diffusion-controlled redistribution of hydrogen that is picked up by zirconium-base nuclear fuel cladding during light water reactor operation. Axial localization of hydrogen, leading to localized precipitation of zirconium hydrides at lower-temperature regions near interpellet gaps, is studied with a bespoke model, while radial diffusion, leading to formation of a densely hydrided rim subjacent to the waterside oxide layer, is studied with a more general model. The calculated results are compared with experimental observations and similar computational studies reported in the literature. The results underline the importance of hydrogen redistribution with regard to local embrittlement of the cladding tubes.
Read the full abstract

Materials Science

Modeling Polaron Excitations and Stabilization Mechanisms in Conjugated Polymers

Vishal Jindal and Scott T. Milner

Charge carriers in organic semiconductors form polarons, which are self-localized states stabilized by interactions with their environment. Using a dielectric-stabilized tight-binding model parameterized from first-principles calculations, we compute ground and excited polaron states in poly(3-hexylthiophene) (P3HT). Our results quantitatively reproduce key mid-infrared absorption features, notably the chain-length-dependent shift of the intrachain polaron excitation peak (peak B) and its variation between regioregular and regiorandom P3HT. Comparison to an alternative stabilization mechanism based on local ring distortions reveals that dielectric polarization dominates polaron formation, as ring distortions yield insufficient binding and excitation energies inconsistent with experiments. These findings clarify the microscopic origin of polarons in conjugated polymers and provide a predictive framework linking polaron energetics to spectroscopic observables, advancing the understanding of charge transport in organic semiconductors.
Read the full abstract

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

Cavity modification of magnetoplasmon mode through coupling with intersubband polaritons

Lucy L. Hale, Daniele De Bernardis, Stephan Lempereur et al. (+12 more)

We investigate the coupling of a multi-mode metal-insulator-metal cavity to a two-dimensional electron gas (2DEG) in a quantum well in the presence of a strong magnetic field. The TM cavity mode is strongly hybridized with an intersubband transition of the 2DEG, forming a polaritonic mode in the ultrastrong coupling regime, while the TE mode remains an almost purely cavity mode. The magnetoplasmon excitation emerging from the presence of the magnetic field couples with both TM and TE modes, exhibiting different coupling strengths and levels of spatial field inhomogeneity. While the strong homogeneity of the bare TE mode gives rise to the standard anticrossing of strong coupling, the inhomogeneous polaritonic TM mode is shown to activate an observable Coulombic effect in the spectral response, often referred to as non-locality. This experiment demonstrates a cavity-induced modification of the 2DEG response and offers a new route to probing the effect of Coulomb interactions in ultrastrongly coupled systems via reshaping of their cavity mode profiles.
Read the full abstract

All authors Lucy L. Hale, Daniele De Bernardis, Stephan Lempereur, Lianhe H. Li, A. Giles Davies, Edmund H. Linfield, Trevor Blaikie, Chris Deimert, Zbigniew R. Wasilewski, Iacopo Carusotto, Jean-Michel Manceau, Mathieu Jeannin, Raffaele Colombelli, Jérôme Faist, Giacomo Scalari

Materials Science

Dislocation-point defect interaction on plasticity across the length scale in SrTiO3

Chukwudalu Okafor, Kohei Takahara, Svetlana Korneychuk et al. (+7 more)

Point defect engineering is widely used to tailor the electronic and transport properties of complex oxides, yet its influence on dislocation plasticity remains poorly understood. Here, we establish how donor (Nb) doping modifies dislocation nucleation, multiplication, and mobility in single-crystal SrTiO3 by bridging nano-, meso-, and macroscale deformation. Using a combinatorial approach involving nanoindentation, cyclic Brinell indentation, and bulk uniaxial compression, we show that 0.5 wt% Nb doping consistently suppresses room-temperature plasticity. Nanoindentation reveals increased pop-in stresses, increased lattice friction stress, and reduced creep rates, indicating inhibited dislocation nucleation and motion with Nb doping. Mesoscale Brinell indentation exhibits discrete, widely spaced slip traces reflecting more difficult dislocation multiplication. Bulk uniaxial compression confirms ~50% higher yield stress in Nb-doped (0.5 wt%) SrTiO3 samples. Comparison with Fe-doped SrTiO3 (equivalent doping concentration) isolates the role of defect chemistry: oxygen vacancies promote incipient plasticity, whereas Sr vacancies dominate in Nb-doped SrTiO3, strongly hindering dislocation motion. This length-scale bridging approach consistently reveals suppressed dislocation nucleation, multiplication, and motion in the 0.5 wt% Nb-doped samples. These insights underline the importance of dislocation-defect chemistry on the mechanical behavior of functional oxides.
Read the full abstract

All authors Chukwudalu Okafor, Kohei Takahara, Svetlana Korneychuk, Isabel Huck, Sebastian Bruns, Ruoqi Li, Yan Li, Karsten Durst, Atsutomo Nakamura, Xufei Fang

Materials Science

First-Principles Investigation of Sr2PrSbO6 Double Perovskite: An Emerging Aspirant for Electrocatalysis, Plasmonic, Photonics, Thermoelectric and Solar Cell Applications

Md. Mohiuddin and Alamgir Kabir

In this study, we investigate the structural properties, chemical stability, and electronic, optical, and thermoelectric properties of $\mathrm{Sr_2PrSbO_6}$ using first-principles calculations based on Density Functional Theory (DFT). The goal of this study is to evaluate its potential contribution to next-generation electrocatalysts, optoelectronic devices, and thermoelectric systems. The structural optimization reveals that $\mathrm{Sr_2PrSbO_6}$ crystallizes in a stable cubic perovskite structure with space group $Fm\bar{3}m$. The calculated formation energy indicates high thermodynamic stability, confirming the viability of $\mathrm{Sr_2PrSbO_6}$ for practical applications. The electronic band structure calculations show that $\mathrm{Sr_2PrSbO_6}$ is a wide bandgap semiconductor with a direct bandgap of $3.488~\mathrm{eV}$ at the $\Gamma$-point. The calculated density of states (DOS) indicates significant contributions from O $2p$, Sb $5p$, and Pr $5d$ orbitals. Optical property calculations, including the dielectric function and absorption coefficient, reveal strong absorption in the UV regions, making $\mathrm{Sr_2PrSbO_6}$ a promising candidate for optoelectronic applications such as UV light-emitting diodes (LEDs) and photovoltaic-thermoelectric (PV-TE) tandem systems. At room temperature, the calculated dimensionless quantity $ZT$ is $0.33$, which indicates this material as a possible candidate for thermoelectric applications. Our results will serve as a benchmark for future experimental and theoretical research on the properties of this material.
Read the full abstract

Materials Science

Defect thermodynamics of orthorhombic Ba$_2$In$_2$O$_5$: First-principles calculations on the role of oxygen dumbbell interstitials

Rachele Sciotto and Karsten Albe

The brownmillerite-type barium indate (Ba$_2$In$_2$O$_5$) is a potential electrolyte for mixed ionic-electronic conduction in solid oxide fuel cells. Revealing the defect chemistry of this material is key to understanding its ionic and electronic conductivity. In this contribution, we report the existence of oxygen interstitials in a dumbbell configuration, which are also observed in In$_2$O$_3$. Using Density Functional Theory within the generalized gradient approximation, complemented by selected hybrid-functional calculations, we investigate vacancies, various oxygen interstitials, and Frenkel pairs. In doing so, we evaluate the formation energies, charge transition levels, and concentrations as a function of oxygen partial pressure. Our results show that oxygen vacancies and interstitials dominate the intrinsic defect landscape. Among the interstitials, we identify stable dumbbell configurations that remain neutral across the entire band gap. Other interstitial configurations exhibit charged states and become the prevailing compensating defects at high oxygen partial pressures, alongside oxygen vacancies. Our results provide a consistent picture of the thermodynamics of intrinsic defects in barium indate, setting the stage for future investigations of the diffusion dynamics of oxygen vacancies and interstitials.
Read the full abstract

Materials Science

Multiferroic-like Quasiparticles in Ferroelectrics

Ping Tang and Gerrit E. W. Bauer

Multiferroics are materials with coexisting electric and magnetic orders that are of central importance for fundamental research and technological applications. Unfortunately, intrinsic multiferroics that operate at room temperature remain rare due to an apparent incompatibility between magnetism and ferroelectricity. Here we predict that a pure ferroelectric support multiferroic-like quasiparticles, termed “multiferrons", that simultaneously carry static magnetic and electric dipoles. The electric dipole moment emerges from the parity-odd anharmonicity of the ferroelectric dynamics, while the magnetic moment has both paramagnetic and diamagnetic origins generated by circularly polarized transverse fluctuations of the ferroelectric polarization. In contrast to the established “dynamical multiferroicity" of circularly polarized phonons, which involve only oscillating electric dipoles, multiferrons cause, apart from Zeeman and Einstein-de Haas effects, a linear dc Stark response, giant electric-field-tunable second-harmonic generation in the THz-frequency regime, and a finite magnetoelectric cross coupling. Multiferrons open a new route toward nonlinear THz optical applications and offer multiferroic functionalities with simple ferroelectrics.
Read the full abstract

Materials Science

Stability Criteria and Optoelectronic Properties of Mg3ZBr3 (Z = As, Sb, Bi) Perovskites for Evaluating the Performance in PIN Photo Diode

Md Mohiuddin, Mohammed Mehedi Hasan and Alamgir Kabir

The toxicity and stability issues of lead-based perovskites motivate the search for non-toxic, durable alternatives. This work examines lead-free $\mathrm{Mg_3ZBr_3}$ ($Z=\mathrm{As,Sb,Bi}$) halide perovskites as optoelectronic materials, with emphasis on $\mathrm{Mg_3AsBr_3}$ and $\mathrm{Mg_3SbBr_3}$. First-principles calculations establish cubic $Pm\bar{3}m$ frameworks stabilized by strong Mg–Br linkages, and indirect band gaps of $2.0645\,\mathrm{eV}$ for $\mathrm{Mg_3AsBr_3}$ and $1.6533\,\mathrm{eV}$ for $\mathrm{Mg_3SbBr_3}$ obtained using hybrid functionals. Optical spectra show a rapid rise in absorption above the gap and an increasing static dielectric response along $\mathrm{As}\rightarrow\mathrm{Sb}\rightarrow\mathrm{Bi}$, indicating strengthened light–matter coupling. Phonon dispersions lack imaginary branches, confirming dynamical stability, and exhibit large mode anharmonicity (Grüneisen signatures) consistent with soft-lattice heat transport. Moving down the pnictogen series expands the lattice and lowers the Goldschmidt tolerance factor, while enhanced pnictogen–Br $p$-orbital hybridization and stereochemically active $n\mathrm{s}^{2}$ lone pairs (Sb, Bi) narrow the band gap and increase the optical dielectric response. Elastic analyses confirm Born stability and moderate stiffness, with Hill-averaged bulk moduli decreasing from approximately $44\,\mathrm{GPa}$ ($\mathrm{Mg_3AsBr_3}$) to $35\,\mathrm{GPa}$ ($\mathrm{Mg_3BiBr_3}$). Drift–diffusion $p$–$i$–$n$ simulations qualitatively track band-edge-limited spectra, aligning with the computed gaps. Together, these results position these materials as promising lead-free candidates for stable thin-film photodiode and photovoltaic applications.
Read the full abstract

Materials Science

Imaging atoms in real-space with elemental selectivity

Harry Mönig

Tip functionalization in AFM allows imaging organic nano-structures with sub-molecular resolution. Here, recent progress by using atomically defined copper-oxide tips is discussed. With their outstanding rigidity and elemental selectivity on metal-oxide surfaces, these probes constitute a powerful approach for the atomic-scale characterization of metal-oxide surfaces and a major step towards standardized scanning probe microscopy.
Read the full abstract