Materials Science
Sustainable Metal-Organic Framework Water Harvesters in the Artificial Intelligence Era
Reid A. Coyle, Shyam Chand Pal, Peter Walther et al. (+3 more)
Metal-organic frameworks (MOFs) are excellent candidates for water harvesting due to their tunable pore environments, which can be precisely engineered to capture and release water in arid conditions. Integrating artificial intelligence (AI) into MOF discovery can further accelerate the design of high-performance sorbents by identifying structural features that enhance atmospheric water harvesting (AWH), stability, and cycling efficiency. In this Perspective, we examine key MOF design principles, including cooperative adsorption, operational relative humidity (RH), uptake capacity, hysteresis, and scalability. We highlight recent design advancements such as multivariate strategies and long-arm linker extension, and examine how these principles tune pore capacity and hydrophilicity, while preserving stability and crystallinity. Furthermore, we discuss how AI, large
language models (LLMs), and data mining can accelerate the discovery process through predictive synthesis, inverse design, and elucidating synthesis-structure-property relationships for the next generation of MOF water harvesters.
Read the full abstract ▾
All authors Reid A. Coyle, Shyam Chand Pal, Peter Walther, Saeun Park, Bin Feng, Zhiling Zheng
Materials Science
Field-Driven Hybrid Filament Formation Governs Switching in Ta-HfO$_2$-Pt Memristors
Ashutosh Krishna Amaram, Aditya Koneru and Subramanian KRS Sankaranarayanan
Memristive devices have gained significant
attention for their potential in next-generation non-volatile
memory and neuromorphic computing architectures. Among emerging candidates, transition metal
oxides have proven particularly promising. While the switching mechanism in Ta/HfO$_2$/Pt devices was long attributed solely to oxygen vacancy based filaments, recent experimental evidence suggests a more complex dual-regime: the
diffusion of metal cations also contributes to the formation of a conductive bridge. However, the precise atomistic mechanisms governing this metal cation migration remain poorly understood. Additionally, the role of defects such as oxygen vacancies present in the transition metal
oxide in determining the final filament size and shape is also not well understood. Here, we employ molecular dynamics (MD) simulations with dynamic charge transfer to provide a detailed analysis of the atomistic mechanisms governing the co-formation of Ta-cation and oxygen-deficient filaments. We clearly show how varying the initial oxygen vacancy concentrations and spatial configurations within the HfO$_2$
matrix influences the final morphology and dimensions of the conductive filament. The switching is governed by field-driven formation and rupture of a hybrid Ta-cation-rich, oxygen-deficient filament in HfO$_2$. Our simulations closely match experiment, validating the model as a robust framework for understanding switching in
oxide memristors and guiding designs that reduce cycle-to-cycle and device-to-device variability – key barriers to high-performance devices.
Read the full abstract ▾
Materials Science · Cross-listed from cond-mat.str-el
Strongly-coupled hybrid lattice-plasmons in layered cuprates
Ke-Jun Xu, Nathan Giles-Donovan, Stefano Agrestini et al. (+11 more)
Metallic systems with delocalized valence electrons host collective charge density oscillations known as plasmons. On the other hand, conventional
insulators do not have free electrons and the low energy charge degrees of freedom are pinned to the ions. The fate of the collective charge excitations in the intermediate regime is an outstanding question. This problem is especially important for strongly correlated systems such as the layered cuprates, where unconventional superconductivity and other emergent phenomena arise from valence electrons on the border between Mott localization and itinerancy. Using resonant inelastic X-ray scattering, we track this
evolution in the prototypical electron-doped cuprate Nd2-xCexCuO4. We find a continuous transformation of the low-energy charge response: from an acoustic plasmon in the metallic regime, to a gapped hybrid mode at intermediate doping, and finally to a nearly dispersionless 139 meV excitation at half filling. Remarkably, the 139 meV excitation has approximately twice the energy of the oxygen breathing
phonon responsible for the dispersion kink observed in angle-resolved photoemission spectroscopy, and is consistent with a putative 2-
phonon excitation observed in Raman spectroscopy. These results establish a unified picture of collective charge excitations across the phase diagram of electron-doped cuprates, showing that such modes persist across the Mott transition via strong coupling to
lattice degrees of freedom and revealing a missing link in the charge dynamics of carrier doped Mott
insulators.
Read the full abstract ▾
All authors Ke-Jun Xu, Nathan Giles-Donovan, Stefano Agrestini, Jaewon Choi, Mirian Garcia-Fernandez, Kejin Zhou, Junfeng He, Costel R. Rotundu, Young S. Lee, Thomas P. Devereaux, Zhi-Xun Shen, Dung-Hai Lee, Robert J. Birgeneau, Wei-Sheng Lee
Materials Science · Cross-listed from physics.app-ph
Comparing Spatially Periodic Feedback and Space-Time Modulation for Unidirectional Wave Propagation in a 1D Mass-Spring-Damper System
João H.S. Brandão, Danilo Braghini and José R.F. Arruda
Unidirectional wave propagation has emerged as a key concept in the dynamics of non-reciprocal mechanical and acoustic metamaterials. This work investigates two fundamentally distinct strategies for achieving directional wave propagation in a periodic one-dimensional mass-spring-damper lumped system: space-time modulation and spatially periodic feedback. In the first approach, the stiffness is modulated periodically in both space and time. The resulting space-time periodic system is analyzed using a Plane Wave Expansion (PWE) formulation based on the Bloch-Floquet theory to obtain the dispersion relation. The traveling modulation produces asymmetric dispersion diagrams and directional band gaps, within which elastic waves propagate preferentially in a single direction due to broken time-reversal
symmetry. In the second approach, non-reciprocity is introduced through a spatially periodic feedback action. The force can depend on the displacement and/or its derivatives, such as velocity or acceleration, and is applied to the masses along the system. The lumped system with a finite number of unit
cells is modeled using classical mechanics principles, yielding a state-space model of the system. The active mechanism can generate directional amplification or attenuation via the non-Hermitian skin effect (NHSE), characterized by boundary-localized modes identified by a topological invariant, the winding number. The stability of the space-time periodic system is assessed through the Lyapunov-Floquet theory. In the periodic feedback case, stability is investigated using the
eigenvalues of the state
matrix. These results provide design guidelines for directional wave propagation in elastic waveguides.
Read the full abstract ▾
Materials Science · Cross-listed from physics.optics
Material selection for mid-infrared thin-film coatings and windows
Jin-Woo Cho, Tanuj Kumar, Hongyan Mei et al. (+1 more)
We summarized the room-temperature optical properties for infrared-transparent materials, defining transparency windows for two different applications: thin-film coatings (absorption coefficient $\alpha < 10 cm^{-1}$) and windows ($\alpha < 1 cm^{-1}$). The transparency requirements for thin films are substantially less stringent, enabling the use of many more optical materials for a given wavelength range. To make an easy-to-use reference, we categorized materials by chemical group, crystallinity, and typical deposition technique, and discussed practical pros and cons such as chemical and thermal stability, mechanical hardness, and cost. The
datasets and plotting scripts are provided so that users can regenerate transparency-window maps for different applications. If you do optical design at infrared wavelengths, we recommend that you print out the figures and stick them on your wall.
Read the full abstract ▾
All authors Jin-Woo Cho, Tanuj Kumar, Hongyan Mei, Mikhail A. Kats
Materials Science
Geometry-based Discovery of Calcium Battery Cathodes Accelerated by Foundational Machine-Learned Models
Dereje Bekele Tekliye, Achinthya Krishna Bheemaguli and Gopalakrishnan Sai Gautam
Calcium batteries (CBs) are an attractive post-Li-ion technology, offering the appeal of Ca's natural abundance and high volumetric energy density. However, practical realization of CBs remains limited by the scarcity of positive electrode (cathode) materials that support reversible Ca$^{2+}$ (de)intercalation under electrochemical conditions. To address this challenge, we screen the materials project (MP) database for novel host structures that can intercalate Ca using geometry- and chemistry-based design principles. Specifically, we employ the Voronoi polyhedral volume as a descriptor of site compatibility for hosting Ca in potential frameworks. Further, we down-select candidate structures progressively through criteria including charge neutrality, absence of non-Ca mobile cations, thermodynamic (meta)stability, average voltage, and Ca migration barriers ($E_m$) using foundational machine-learning (ML) models. Subsequently, we validate the ensemble-ML-predicted $E_m$ in a subset of the final candidates using density functional theory based nudged elastic band calculations. Overall, from an initial pool of 52,945 MP structures, our workflow identifies 37 promising Ca cathode candidates, several of which exhibit favorable combinations of thermodynamic (meta)stability, voltage, and Ca-mobility, marking them as strong candidates for synthesis and electrochemical characterization. Particularly, we identify two Ca cathode candidates with markedly low Ca$^{2+}~E_m$ (CaSc$_2$V$_2$O$_8$ and CaVSO$_4$F$_3$), and four cathode candidates with thermodynamically stable charged states (Ca$_3$(CoO$_2$)$_4$, Ca$_3$Mn$_4$(TeO$_6$)$_2$, CaVF$_5$, and CaVSO$_4$F$_3$). Beyond identifying Ca-cathodes, our work establishes geometry-based descriptors and ML-based workflows as transferable methods for high-throughput screening, enabling the rapid discovery of novel materials for battery and other applications.
Read the full abstract ▾
Materials Science · Cross-listed from cond-mat.str-el
Realization of the Ruby Lattice Antiferromagnet in Layered Transition-Metal Fluorides
Harald O. Jeschke, Daniel Guterding and Pratyay Ghosh
The antiferromagnet on the ruby
lattice is expected to host a range of exotic emergent phenomena, yet its material realization has remained elusive. Here we show that the layered transition metal fluorides CsBaFe$_3$F$_{12}$ and CsBaCr$_3$F$_{12}$ with Fe$^{3+}$ and Cr$^{3+}$ ions realize only slightly distorted ruby
lattice geometries with
spin moments $S=5/2$ and $S=3/2$, respectively. Their microscopic
Hamiltonians, calculated with DFT energy mapping, are dominated by short-ranged
antiferromagnetic interactions within the ruby layers. Classical Monte Carlo simulations reveal strong frustration in both compounds, with local Néel correlations on the hexagonal plaquettes and distinct long-range ordering tendencies governed by weaker triangular links. For CsBaFe$_3$F$_{12}$, the calculated thermodynamic behaviour is consistent with the experimentally reported
magnetic ordering scale. For CsBaCr$_3$F$_{12}$, classical Monte Carlo and Luttinger-Tisza analysis reveal competing low-energy ordering wave vectors, strong finite-size sensitivity, and a tendency toward incommensurate order. Overall, our results establish these fluorides as experimentally accessible ruby-
lattice antiferromagnets and provide quantitative predictions for future
neutron-scattering studies.
Read the full abstract ▾
Materials Science
A GPU-based Solver for Polarization Dynamics in Ferroelectric Materials
Ali Hasan, Edoardo Piccolo, Anna Giordano et al. (+4 more)
Ferroelectric materials can be used for the development of multiple device concepts combining non-
volatility, small dimensions, low-power actuation, and electrical tunability. Such development demands efficient and precise design of simulation tools describing the polarization texture. However, most existing ferroelectric solvers are CPU-based and rely on simplified electrostatic treatments and reduced-dimensional representations of the polarization field. These approximations limit their ability to capture finite-size and boundary effects and restrict the range of domain structures and domain walls that can be realistically simulated. Here, we present a fully GPU (graphics processing units)-accelerated and scalable numerical solver, named PETASPIN_microelectrics, for computing the full polarization vector field of ferroelectric systems using the Ginzburg-Landau formalism. Our solver incorporates an optimized and validated calculation of the full electrostatic field and enables the parallel execution of multiple simulations. We systematically validated the solver with several
benchmark problems, including phase transitions in BaTiO3 and ferroelectric domain wall profiles. Our simulations reproduce temperature-driven hysteretic phase transitions in BaTiO3. We also reproduce hysteresis loops and demonstrate stabilization of a three-dimensional hybrid skyrmion in a PbTiO3/SrTiO3
bilayer system. Our results show quantitative agreement with predictions from an analytical theory and prior experimental studies. The proposed solver provides an efficient, accurate platform for large-scale simulations of ferroelectric materials including stabilization of topological textures supporting predictive modeling for next-generation of ferroelectric device design.
Read the full abstract ▾
All authors Ali Hasan, Edoardo Piccolo, Anna Giordano, Natalya Fedorova, Jorge Íñiguez-González, Davi Rodrigues, Giovanni Finocchio
Materials Science
Synthesis and properties of bulk Mg$_3$WN$_4$ in a wurtzite-derived structure
Anna A. Berseneva, Christopher L. Rom, Layton Rudolph et al. (+5 more)
Experimental synthesis of theoretically predicted materials with controlled elemental coordination environments can lead to realization of useful properties, such as facile ion transport or ferroelectric switching. Among such materials are new ternary nitrides in the Mg-W-N composition space, where several new stable and metastable compounds have been predicted and synthesized recently in bulk and film forms. Here, we report for the first time on the bulk synthesis of Mg$_3$WN$_4$ in a wurtzite-derived
crystal structure via a solid state metathesis reaction. $In$ $situ$ synchrotron powder X-ray diffraction shows how the ion exchange proceeds from Li$_6$WN$_4$ + 3 MgCl$_2$ precursors to Mg$_3$WN$_4$ + 6 LiCl products, with the reaction starting slowly near 380 $^\circ$C and completing by 600 $^\circ$C, including the presence of a competing disordered rocksalt-derived phase (Mg,W)N above 440 $^\circ$C. The follow up $ex$ $situ$ powder synthesis at 400 $^\circ$C for 0.5 hour with 10% excess MgCl$_2$ reveals the cation-ordered nature of the wurtzite-derived Mg$_3$WN$_4$ structure with polar
symmetry confirmed by second harmonic generation measurements. Optical absorption spectra, chemical composition analysis, and electron microscopy imaging suggests that bulk wurtzite Mg$_3$WN$_4$ is prone to defect formation. Overall, this study shows that selective $ex$ $situ$ synthesis of the phase pure ternary nitrides, informed by in situ measurements, is possible by carefully controlling the thermal budget of the reaction, and paves a way towards property characterization of wurtzite Mg$_3$WN$_4$.
Read the full abstract ▾
All authors Anna A. Berseneva, Christopher L. Rom, Layton Rudolph, Yunseung Kuk, P. Shiv Halasyamani, Rebecca W. Smaha, James R. Neilson, Andriy Zakutayev
Materials Science · Cross-listed from physics.chem-ph
How reproducible are first-principles simulations of liquid water?
Niamh ONeill, Benjamin X. Shi, William J. Baldwin et al. (+5 more)
Liquid water is fundamentally important, and its accurate computer simulation has been the driving force for myriad methodological developments. Ab initio molecular dynamics with forces obtained from density functional theory (DFT) is now a standard tool widely used by researchers. However, we reveal that previous studies of
liquid water using the same widely-used density functional (revPBE-D3) exhibit significant discrepancies with one another, varying by over 20% in the
diffusion coefficient and 10% in the density, raising fundamental questions about reproducibility. By combining modern long-range machine-learning interatomic potentials that enable robust statistical sampling with carefully converged DFT training data, we resolve these discrepancies, achieving consensus across six diverse community codes. Our predictions differ markedly from previous literature: we show that most previous results overestimate the density and underestimate the
diffusion coefficient of revPBE-D3 water due to basis set incompleteness and pseudopotential inconsistencies, coupled with limitations in statistical sampling (in some cases). These
benchmark values provide a reliable reference for validating current and future implementations of DFT-based ab initio molecular dynamics. Reaching agreement establishes confidence and credibility and serves as a prerequisite for the systematic assessment of new density functionals and numerical approximations.
Read the full abstract ▾
All authors Niamh ONeill, Benjamin X. Shi, William J. Baldwin, Albert P. Bartok, Chris J. Pickard, Angelos Michaelides, Gabor Csanyi, Timothy C. Berkelbach
Materials Science · Cross-listed from cond-mat.str-el
Avoided Stoner instability at a single ordinary Van Hove point
I.S. Tupitsyn, B. Currie, A.V. Chubukov et al. (+3 more)
When the
Fermi surface and the Brillouin zone boundary touch at a Van Hove point, mean-field analysis predicts a
ferromagnetic (Stoner) instability at finite $T_{MF}$ for any coupling strength due to the divergent density of states. However, the predicted effect has not been observed experimentally. Several qualitative theoretical proposals have been put forward to explain why the mean-field prediction fails. Based on numerically exact results for the two-dimensional Hubbard model with an ordinary Van Hove singularity, we uncover the mechanisms behind the suppression of the
ferromagnetic instability. We employ two diagrammatic Monte Carlo approaches: (i) the four-channel self-consistent approximation and (ii) numerically exact method of combinatorial summation of diagrams with controlled resummation of the truncated expansion. We find that the system avoids the Stoner instability down to temperatures an order of magnitude below $T_{MF}$ due to the combination of the downward renormalization of the effective coupling and the suppression of the density of states by the loss of the quasiparticle residue.
Read the full abstract ▾
All authors I.S. Tupitsyn, B. Currie, A.V. Chubukov, B.V. Svistunov, E. Kozik, N.V. Prokof'ev
Materials Science
Universal Stability of Ga Split Vacancies across \alpha-, \beta-, and \kappa-Ga2O3 Polymorphs: A Machine-Learning Accelerated Study
Mohamed Abdelilah Fadla, Myrta Grüning and Lorenzo Stella
Split Ga vacancies are the dominant native acceptor in $\beta$-$Ga_2O_3$; however, their role in $\alpha$ and $\kappa$ phases has been largely overlooked or assumed to be unfavorable. A detailed understanding of these defects is critical for tailoring the electrical conductivity and optical properties and optimising $Ga_2O_3$-based devices. In this work, we used machine learning interatomic potentials (MLIPs) to accelerate the discovery of non-local defect reconstructions, followed by HSE06 hybrid DFT to accurately quantify defect properties of single vacancy $V_{\text{Ga}}$, split vacancy $V_{\text{Ga}}^{\text{i}}$ and substitutional donors ($\mathrm{Hf_{Ga}}$ and $\mathrm{Si_{Ga}}$) across a wide range of experimentally relevant conditions for the oxygen chemical potential. We find that split vacancies are the ground-state vacancy for all studied polymorphs ($\beta$, $\alpha$, and $\kappa$). Split vacancies are more stable than simple vacancies by ~0.75 eV ($\beta$), ~0.41 eV ($\alpha$), and ~0.14 eV ($\kappa$). Notably, MLIPs correctly identified the specific split-vacancy ground states and yielded an energetic ordering of
symmetry-inequivalent defect configurations in excellent agreement with HSE06 results. While Hf and Si show low formation energy and act as shallow donors, especially under oxygen-poor conditions, their efficiency is limited by split-vacancy compensation. The growth under oxygen-poor conditions is a universal requirement to suppress these defects and achieve high n-type conductivity across the $Ga_2O_3$ polymorph.
Read the full abstract ▾
Materials Science · Cross-listed from physics.optics
Orbital Altermagnetic Photonic Crystal
Sichang Qiu, Huichang Li, Yan Meng et al. (+6 more)
Altermagnetism features momentum-dependent
spin splitting without net magnetization, extending spintronics beyond conventional ferromagnetism and antiferromagnetism. However, the photonic realization of altermagnetism has remained a formidable challenge due to the fundamental differences between fermionic electrons and bosonic
photons. Here, we report the first experimental realization of an orbital altermagnetic photonic
crystal, based on an antiunitary $C_{4z}\mathcal{T}$
symmetry enforced correspondence between a local $p$-orbital $\sigma/\pi$ doublet and
crystal momentum. We experimentally demonstrate that the resulting system exhibits momentum-dependent
spin splitting with alternating pseudospin polarization and a $d_{xy}$-wave form factor, as confirmed by measured band structures and iso-frequency contours. Moreover, we show that the orbital altermagnetic photonic
crystal supports unique pseudospin-selective transport of electromagnetic waves, including photonic pseudospin splitting and pseudospin filtering. Our results extend the field of alternagnetism to photonic systems, opening a new avenue for designing spinphotonic devices.
Read the full abstract ▾
All authors Sichang Qiu, Huichang Li, Yan Meng, Xiang Xi, Zebin Zhu, Ce Shang, Zhen Gao, Tie Jun Cui, Shuo Liu
Materials Science
Ultrafast dynamics of excitons in black phosphorus
Geoffroy Kremer, Juan F. P. Mosquera, Joël Morf et al. (+9 more)
Excitons are key quasiparticles determining the optical properties of solids. As such, they can be utilized to coherently control the electronic structure of materials using optical femtosecond pulses. Identifying the decoherence mechanism during the early non-
equilibrium dynamics is crucial to achieve light-induced band-structure engineering in
semiconductors. Here, we generate
excitons in the direct band gap
semiconductor black phosphorus with a resonant mid-infrared photoexcitation. Using time- and angle-resolved photoemission spectroscopy, we track their complex ultrafast dynamics on the few-picosecond time scale. We develop a
quantum-kinetic theoretical framework to model the decoherence of
excitons into dark
excitons via
phonon scattering. By combining simulation and experiment, we quantify key parameters describing the early dynamics of the
excitons. Our work highlights
phonon-mediated intravalley scattering as a fundamental limitation for coherent
exciton phenomena in single-valley
semiconductors.
Read the full abstract ▾
All authors Geoffroy Kremer, Juan F. P. Mosquera, Joël Morf, Aymen Mahmoudi, Frédéric Chassot, Viktor Christiansson, Maxime Rumo, Manuele Balestra, Fabian O. von Rohr, Philipp Werner, Michael Schüler, Claude Monney
Materials Science · Cross-listed from cond-mat.soft
Third rank permeability in chiral solids
Roderic S. Lakes
Effects of a third rank permeability term in
chiral solids are studied. Fluid flow through such materials acquires vorticity upon emergence from the material. Materials of interest include
chiral surface
lattices such as the gyroid,
chiral rib
lattices, and granular materials comprised of sugar
crystals, quartz sand, wheat or beans. A characteristic length scale is associated with the chirality. The length scale can be obtained by several methods. Contacts with nonlocal permeability, elasticity and piezoelectricity are explored.
Read the full abstract ▾
Materials Science
Electron-beam induced methane decomposition for in-situ carbon doping of hexagonal boron nitride
Barbara Maria Mayer, Manuel Längle, Umair Javed et al. (+3 more)
Controlling the spatial incorporation of carbon into hexagonal boron nitride (hBN) is essential for engineering optically active defects, yet existing approaches lack nanoscale precision and control over the carbon supply. Here, we demonstrate a method for carbon doping of hBN using electron-beam irradiation in a low-pressure methane atmosphere, where the beam simultaneously generates vacancies and decomposes methane into individual carbon and hydrogen atoms. Using annular dark-field scanning transmission electron microscopy, we show that increasing the methane partial pressure suppresses pore growth and drives the formation of triangular boron-terminated pores through preferential hydrogen etching of nitrogen. Time-resolved electron energy-loss spectroscopy (EELS) mapping reveals progressive carbon incorporation into the
lattice, accompanied by boron and nitrogen depletion. Carbon clustering occurs predominantly within the irradiated area: 84+-7% of carbon-rich regions are confined to the area exposed to the electron beam, while some carbon atoms are also found to diffuse up to an average distance of 4.7+-0.5 nm beyond it. The incorporated carbon atoms arrange in a hexagonal pattern within the
lattice, forming patches that do not exceed ~1 nm in size. Analysis of the EELS fine structure indicates modifications to the local electronic environment within these regions, with implications for the optical properties of the resulting carbon-related defects.
Read the full abstract ▾
All authors Barbara Maria Mayer, Manuel Längle, Umair Javed, Toma Susi, E. Harriet Åhlgren, Jani Kotakoski
Materials Science · Cross-listed from cond-mat.mes-hall
Electrically driven Rabi dynamics of magnetic-field-induced corner states in a two-dimensional topological insulator
D. V. Khomitsky, E. A. Lavrukhina, D. P. Krasavin et al. (+2 more)
We study coherent electric manipulation of
magnetic-field-induced localized states at a double kink of a helical edge in a HgTe/CdHgTe
quantum well. An in-plane
magnetic field opens a gap in the one-dimensional edge spectrum, while changes in the edge orientation generate localized in-gap states at the kinks. We show that, for suitable geometry and
magnetic-field direction, two such states form an effective lithographically defined two-level subsystem. Using an edge-state model that includes both the localized levels and the fully propagating 1D edge states outside the
magnetic-field-induced gap, we calculate the electric-dipole
matrix elements and solve the time-dependent problem under resonant driving. The resulting dynamics exhibits Rabi oscillations with linear frequencies of $20$–$40$~GHz for realistic parameters. We find that the propagating 1D edge states provide a leakage channel whose strength is strongly controlled by the driving amplitude: reducing the electric field suppresses leakage below the percent level while preserving GHz-scale coherent oscillations. These results establish a route from
magnetic-field-induced corner-state physics to electrically driven two-level dynamics in a realistic two-dimensional topological-
insulator edge geometry.
Read the full abstract ▾
All authors D. V. Khomitsky, E. A. Lavrukhina, D. P. Krasavin, S. S. Krishtopenko, F. Teppe
Materials Science · Cross-listed from cond-mat.mes-hall
Symmetry-Selective Topological Magnon Engineering by Phonon Angular Momentum
Markus Weißenhofer, Philipp Rieger, Chandan K. Singh et al. (+3 more)
Dynamical control of Berry
curvature remains an outstanding challenge in the engineering of topological phases. Here, we demonstrate control of
magnon band structures via coherently driven
phonons, based on ab initio
spin-
lattice coupling and Floquet theory. We show that this control is
symmetry selective: linearly polarized
phonons leave the spectrum unchanged, whereas circular and elliptical
phonons carrying finite
phonon angular momentum (PAM) induce
chiral interactions that open and tune gaps at Dirac points, generating and reversing topological
magnon phases. The gap magnitude and Chern numbers are directly governed by the PAM, enabling handedness-selective
topology control. Applied to monolayer CrI$_3$, and supported by
symmetry analysis, our results establish driven
lattice dynamics as a general route to engineering topological bosonic excitations and a versatile platform for Floquet control of magnetism.
Read the full abstract ▾
All authors Markus Weißenhofer, Philipp Rieger, Chandan K. Singh, M. S. Mrudul, Sergiy Mankovsky, Peter M. Oppeneer
Materials Science
Can MACE Potentials Accurately Describe Magnetism and Phase Stability in Fe-Ni Alloys? A Systematic Benchmark
Kushal Ramakrishna, Mani Lokamani and Attila Cangi
We present a systematic
benchmark of MACE potentials for iron-nickel
alloys, focusing on structural, elastic,
magnetic, and finite-temperature properties relevant to phase stability. The reference
dataset comprises
spin-polarized PBE density functional theory (DFT) calculations for chemically disordered special quasirandom structures (SQS), spanning compositions, bcc and fcc
crystal structures, and volumetric and shear deformations. A system-specific MACE-sqs model trained on this
dataset achieves validation errors of 2.0 meV/atom for energies and 24.3 meV/Angstrom for forces. Compared with several MACE foundation models, including models trained with Hubbard U corrections, MACE-sqs gives the most consistent agreement with DFT and experiment for equations of state,
equilibrium volumes, elastic constants, and thermal expansion trends in bcc and fcc Fe-Ni
alloys. For the bcc-to-hcp transition, MACE-sqs predicts a pure-Fe transition pressure closer to experiment than the tested foundation models, but all models predict an incorrect increase of transition pressure with Ni content. This failure indicates that high-pressure
magnetic collapse and composition-dependent magnetoelastic effects are not yet fully captured. Overall, targeted SQS-based training substantially improves the accuracy of MACE potentials for Fe-Ni
alloys, while phase stability under
magnetic collapse remains a key limitation for future model development.
Read the full abstract ▾
Materials Science
Global magnetic phase diagram and multiple unconventional magnets in NiAs-type compounds
Shibo Shen and Yilin Wang
NiAs-type compounds such as CrSb and MnTe host $g$-wave altermagnet (AM) state. In order to search other possible unconventional magnets in this system, we present a global
magnetic phase diagram based on a classical $J_1$-$J_2$-$J_3$ Heisenberg model and density functional theory (DFT) calculations. We find another $g$-wave AM state and two $f$-wave OPMs in the phase diagram. Intriguingly, we show that a mixed-parity of the $f$-wave OPM and $g$-wave AM state can naturally emerge in an umbrella-like noncollinear
magnetic structure. Our DFT calculations show that CrSe and CrTe$_{1-x}$Se$_x$ are generally in such mixing state with dominated $f$-wave component. The interlayer next-nearest-neighbor coupling $J_3$ is shown to be crucial in determining the phase diagram and in inducing strong competition between conventional and unconventional magnets. Inspired by this, we demonstrate that AM or OPM could be realized by applying chemical doping or strain to conventional magnets. Our results provide a guidance for design of both even- and odd-parity as well as mixed-parity unconventional magnets in NiAs-type compounds.
Read the full abstract ▾
Materials Science
Engineering Molecular Rectification: Mechanisms, Modulation Strategies, and Device Integration
Junnan Guo, Shufan Song, Wenhui Fang et al. (+6 more)
Molecular rectifiers, as prototypical components of molecular electronics, present unique opportunities for pushing device miniaturization to its ultimate limits. Nevertheless, challenges including limited rectification ratios (RR), insufficient robustness, and poor reproducibility impede their practical deployment. To make molecular rectifiers competitive with silicon-based devices, it is important to fully understand the design principles and fabrication methods from both mechanistic and experimental perspectives. By holistically considering the transport mechanisms, modulation strategies, fabrication, characterization techniques, and theoretical simulations, this review provides a comprehensive overview of molecular rectifiers. Representative examples of conceptually significant and high-performance molecular rectifier systems are highlighted to illustrate the relationships between rectification mechanisms, molecular design strategies, and device realization. Building on these discussions, we present an outlook for current bottlenecks and future directions to guide the development of molecular rectifiers. This review aims to serve as both a conceptual framework and a technical reference for researchers working at the intersection of molecular electronics and nanoscale device engineering in the post-CMOS era.
Read the full abstract ▾
All authors Junnan Guo, Shufan Song, Wenhui Fang, Jifeng Tang, Wenhao Li, Weikang Wu, Hui Li, Shishen Yan, Lishu Zhang
Materials Science · Cross-listed from cs.LG
LEIA: Learned Environment for Interactive Architected Materials
Haiqian Yang, Yuan Cao and Markus J. Buehler
World models have enabled interactive exploration of game environments and robotic manipulation, but physical engineering remains beyond their reach: real materials exhibit nonlinear constitutive laws, carry history-dependent internal state, undergo inertial dynamics, and may possess hierarchical structures spanning multiple length scales. We present LEIA (Learned Environment for Interactive Architected materials), a world model that lets engineers apply boundary conditions step by step and observe the resulting deformation and stress fields in real time. LEIA handles large three-dimensional unstructured meshes and generates autoregressive responses to user-specified loading. We introduce MicroPlate, a
benchmark of architected plates spanning two regimes of microstructure modeling: architected
lattices that resolve microstructure explicitly through three-dimensional geometry, and a homogeneous plate where microstructural change is modeled implicitly through internal degrees of freedom. MicroPlate is used to assess LEIA alongside four baseline methods across both regimes. Finally, we demonstrate that LEIA enables efficient candidate generation and ranking for fast surrogate-guided search for de novo designs of architected materials, with stress-accurate candidate ranking validated by finite element ground truth.
Read the full abstract ▾
Materials Science
SC-1 Etching of Niobium and Titanium Nitride Thin Films
Adrián Gutiérrez-Cruz, K. A. C. Rathnathilaka, Jani M. Taskinen et al. (+6 more)
Dry etching techniques, ubiquitous in microelectronics fabrication, often result in challenging levels of undesired collateral
plasma-induced damage. In this work, we demonstrate a wet etching alternative for the patterning of niobium (Nb) and titanium nitride (TiN) thin films using the Standard Cleaning 1 (SC-1) solution. We characterize the etching process through its time-
evolution dynamics, supported by scanning-electron and atomic force microscopy assessment of the etched film morphology. The results suggest etch dynamics that are linked to native
oxides and film microstructure. Overall, the manageable etch rates, the safe operation and the high material selectivity are attractive for practical use in microelectronics fabrication.
Read the full abstract ▾
All authors Adrián Gutiérrez-Cruz, K. A. C. Rathnathilaka, Jani M. Taskinen, Tuomas Vaimala, Kestutis Grigoras, Harshad Mishra, Rishabh Upadhyay, Jorden Senior, Alberto Ronzani
Materials Science
Energy and Scaling Limits of Phase-Change Memory
Rivka-Galya Nir-Harwood, Asir I. Khan, Emanuel Ber et al. (+6 more)
Phase change
memory (PCM) relies on a reversible transition between amorphous and crystalline states of a material, and stands as a promising candidate for next-generation, energy-efficient data storage and neuromorphic hardware. Here, we review key innovations that have driven PCM technology to achieve energy consumption down to only tens of femtojoules per bit, and could further advance it closer to its fundamental limits. Because PCM switching is induced thermally, we highlight improvements in energy-efficiency through two primary strategies: by minimizing the active phase change material region to sub-10 nm dimensions, and by enhancing heat confinement within PCM devices to reduce thermal dissipation into the surrounding environment. While the theoretical limits could reach single attojoules per cubic nanometer of
memory material, realizing these limits in practice is significantly constrained by electrical and thermal parasitics, particularly at contacts and interfaces.
Read the full abstract ▾
All authors Rivka-Galya Nir-Harwood, Asir I. Khan, Emanuel Ber, Efrat Ordan, Keren Stern, Kye L. Okabe, Nicolás Wainstein, Eilam Yalon, Eric Pop
Materials Science · Cross-listed from cond-mat.soft
Dry Glass Reference Perturbation Theory: Development, Applications and Extensions
Bennett D. Marshall
This manuscript reviews the development, application and extensions of the dry glass reference perturbation theory (DGRPT) closure to the non-
equilibrium thermodynamics of glassy
polymers (NETGP). DGRPT was developed to allow for the self-consistent and accurate predictions of sorption from complex
liquid mixtures into glassy
polymers. DGRPT is applied in the context of
diffusion theory to predict the membrane based separations of complex
liquid mixtures with glassy
polymer membranes. Several examples are given, including the membrane based fractionation of crude oil as well as the membrane based separation of highly non-ideal alcohol / hydrocarbon
liquid mixtures. Extensions of the theory to higher order expansions are reviewed and evaluated.
Read the full abstract ▾
Materials Science
High temperature Jahn-Teller distortion and short-range order in CsCuCl$_3$
Emma A. Pappas, Toby Woods, Jue Liu et al. (+1 more)
CsCuCl$_3$,
chiral and Jahn-Teller distorted at room temperature, takes a more symmetric structure above 423 K. Describing this 'simpler' high temperature structure is far from simple and has been the subject of many, sometimes contradicting, studies. Here we reinvestigate the high temperature structure of CsCuCl$_3$, its thermal stability, and its effect on room temperature chirality. In situ pair distribution function data from powder
neutron diffraction confirms that CsCuCl$_3$ is Jahn-Teller distorted both below and above $T_\mathrm{c}$, and provides a quantitative view of short-range order in the high temperature structure. In situ powder x-ray diffraction shows that CsCuCl$_3$ does not undergo any additional structural changes above 423 K and is congruently melting. In situ single
crystal x-ray diffraction experiments reveal that the phase transition induces domains of mixed handedness in originally homochiral
crystals. These findings contribute to a better understanding of phase transitions in Jahn-Teller distorted compounds, and highlight the potential use of phase transitions to control
chiral domains.
Read the full abstract ▾
All authors Emma A. Pappas, Toby Woods, Jue Liu, Daniel P. Shoemaker
Materials Science · Cross-listed from cs.LG
AtomComposer: Discovering Chemical Space from First Principles with Reinforcement Learning
Bjarke Hastrup, Francois Cornet, Tejs Vegge et al. (+1 more)
Discovering novel stable molecules without training data remains a grand scientific challenge. Current molecular generative models are trained on large, pre-curated
datasets, which introduce biases and limit exploration of novel chemistry. In contrast, we propose a new paradigm: autonomous, generalized
agents capable of mapping vast, unknown chemical spaces without any pretraining. For the first time, we present AtomComposer, a self-guided
agent that autonomously constructs valid 3D isomers under stoichiometric constraints and is trained exclusively online using reinforcement learning. Unlike existing approaches that generally overfit to a specific chemical formula, we establish a multi-composition training scheme that enables a broad generalization across diverse chemistry, guided by energy- and validity-based rewards. Our
agent can discover up to an order of magnitude more valid isomers on unseen test formulas than existing single-composition reinforcement-learning baselines trained with per-step energy rewards. These results fulfill the promise of online reinforcement learning as a powerful paradigm for scalable, from-scratch exploration of chemical configuration space.
Read the full abstract ▾
All authors Bjarke Hastrup, Francois Cornet, Tejs Vegge, Arghya Bhowmik
Materials Science · Cross-listed from cond-mat.mes-hall
Taming quantum interference: a route to high electrical conductance in carbon nanotube assemblies
Teresa Kulka, Agnieszka E. Lekawa-Raus, John S. Bulmer et al. (+6 more)
In nanostructured networks, transport is governed by junctions between neighbouring building blocks. Improving their
alignment and removing defects is the intuitive route to better electron transport. At low temperatures, when transport becomes coherent, a junction cannot always be reduced to a single effective resistance, because electron-wave interference can strongly enhance or suppress transmission even in nominally ideal junctions. Using carbon nanotube (CNT) networks as a model system, we explore coherent transport through experimentally relevant junctions, from single and multiple single-walled CNT (SWCNT) contacts to double-walled CNT (DWCNT) and multi-walled CNT (MWCNT) junctions, with atomistic tight-binding non-
equilibrium Green's-function calculations, also under a perpendicular
magnetic field. We use analytically solvable minimal models to identify transport regimes expected for quasi-1D nanoscale junctions, and an electron-waveguide picture to interpret their CNT-specific manifestations. For single SWCNT–SWCNT junctions, high-transmission windows are set mainly by overlap length, doping and
magnetic field. Gateway states can enhance conductance when some CNT subbands are gapped, and in some cases a
magnetic field can restore transmission by lifting an interference blockade. In more complex architectures, added paths become selective: multi-junctions generate resonant filtering, while additional walls redistribute transmission instead of acting as independent channels. DWCNT junctions remain outer-wall dominated and SWCNT-like, whereas MWCNT junctions redistribute transmission among coupled walls and show a more complex field response. Our ultrahigh-field measurements likewise show lower, more field-sensitive conductance in MWCNT than SWCNT fibres. This work turns microscopic interference mechanisms into design principles for high-conductance, field-stable CNT conductors.
Read the full abstract ▾
All authors Teresa Kulka, Agnieszka E. Lekawa-Raus, John S. Bulmer, Krzysztof Koziol, Fedor F. Balakirev, Irina V. Lebedeva, Jacek A. Majewski, Magdalena Marganska, Karolina Z. Milowska
Materials Science · Cross-listed from cond-mat.str-el
Zero-Field Thermal Hall Effect in Insulator
Zhe Cui, Haoran Fan, Wenjiang Zhou et al. (+9 more)
Fourier's law dictates that heat flow is usually parallel to the applied temperature gradient. However, under a high
magnetic field, heat flow carried by both electrons in conductors and
phonons in
insulators can be deflected, a phenomenon known as thermal
Hall effect. Intriguingly, we observe at zero field a spontaneous thermal
Hall effect in an
antiferromagnetic insulator. Despite a vanishingly small uncompensated magnetization, the magnitude of this effect is surprisingly large, comparable to typical responses induced by several teslas of external field. This zero-field behavior indicates that charge-neutral heat carriers can be governed by an intrinsic effective field arising from the unique
spin arrangement. Our discovery challenges the centuries-old preconception of heat conduction and open up new avenues for exploring non-trivial topological responses in
quantum materials.
Read the full abstract ▾
All authors Zhe Cui, Haoran Fan, Wenjiang Zhou, Xianghong Jin, Yuchen Gu, Da Ma, Cong Xiao, Hua Jiang, Xincheng Xie, Bai Song, Yuan Li, Xi Lin
Materials Science
Nonlinear Elasticity at the Damage Threshold of Semiconductor Nanocrystals
Daniel Hensel, Adriana Rodrigues, Anagha Kamath et al. (+5 more)
The nonlinear photoacoustic response of indium phosphide nanocrystals on silicon nanotip arrays is investigated using time-resolved optical pump-probe spectroscopy and synchrotron-based X-ray diffraction. Femtosecond
laser excitation triggers low-frequency and high-frequency radial breathing modes of the nanocrystals at 8 GHz and 10.3 GHz, respectively. At excitation fluences above 3 mJ/cm^2, nonlinear frequency mixing occurs, including sum- and difference-frequency generation, indicative of strain-induced nonlinear elasticity. A higher-order extension of Hooke's law models the fluence-dependent spectral response and yields a physically valid elastic energy potential. Ex-situ energy-dispersive X-ray spectroscopy reveals a correlation between nanocrystal oxidation and the emergence of nonlinear acoustic modes. Time-resolved X-ray diffraction confirms the nanocrystals as the origin of the low-frequency modes and supports the hypothesis of acoustic decoupling from the substrate. These findings provide insight into the mechanical limits of
semiconductor nanostructures under intense optical excitation and suggest new pathways for material characterization and optomechanical control at the nanoscale. The results advance the understanding of nonlinear
phonon dynamics in nanocrystals and highlight their potential for integration into next-generation photonic and
quantum devices.
Read the full abstract ▾
All authors Daniel Hensel, Adriana Rodrigues, Anagha Kamath, Daniel Schmidt, Mariana Brede, Oliver Skibitzki, Fariba Hatami, Peter Gaal