Materials Science
Interfacial Coupling Controls Molecular Epitaxy of HMTP on Graphene/SiC
Devanshu Varshney, Pavel Procházka, Veronika Stará et al. (+4 more)
Epitaxial growth critically influences structural and electronic properties of organic
semiconductors.
Graphene serves as a prominent van der Waals template for molecular self-assembly; however,
graphene on SiC is intrinsically heterogeneous, with decoupled monolayer
graphene coexisting with residuals of a covalently bound buffer layer, which may affect molecular ordering. Here, we track the ordering of the molecular donor, 2,3,6,7,10,11-hexamethoxytriphenylene (HMTP), from the first layer to thin films, combining low-energy electron microscopy and diffraction with X-ray diffraction. HMTP forms highly ordered epitaxial layers on single-layer
graphene, whereas growth on the buffer layer initiates as amorphous and evolves into polycrystalline films with weak orientation with respect to the substrate. Crucially, hydrogen intercalation decouples the buffer layer, converting it into quasi-freestanding monolayer
graphene and restoring epitaxial growth. These findings demonstrate that interfacial coupling governs molecular epitaxy on
graphene/SiC, and interface engineering via hydrogen intercalation provides a scalable route to control organic thin-film crystallinity on
graphene.
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All authors Devanshu Varshney, Pavel Procházka, Veronika Stará, Mykhailo Shestopalov, Jan Kunc, Jiří Novák, Jan Čechal
Materials Science · Cross-listed from physics.med-ph
Chitosan/alginate bionanocomposites adorned with mesoporous silica nanoparticles for bone tissue engineering
Satar Yousefiasl, Hamed Manoochehri, Pooyan Makvandi et al. (+6 more)
The regeneration of oral and craniofacial bone defects ranging from minor periodontal and peri-implant defects to large and critical lesions imposes a substantial global health burden. Conventional therapies are associated with several limitations, highlighting the development of a unique treatment strategy, such as tissue engineering. A well-designed scaffold for bone tissue engineering should possess biocompatibility, biodegradability, mechanical strength, and osteoconductivity. For this purpose, mesoporous silica nanoparticles (MSNs) were synthesized and incorporated at different ratios (10, 20, and 30%) into alginate/chitosan (Alg/Chit)-based porous composite scaffolds fabricated through the freeze-drying method. The MSN incorporation significantly improved the mechanical strength of the scaffolds while showing a negligible decreasing effect on the porosity. All of the samples showed desirable swelling behaviors, which is beneficial for
cell attachment and proliferation. The MSN-containing scaffolds indicated a decreased hydrolytic degradation in an MSN percentage-dependent manner. The fabricated scaffolds did not depict cytotoxic characteristics. The Alg/Chit/MSN30 scaffolds not only showed noncytotoxic properties, but also increased the
cell viability significantly compared to the control group. The biomineralization properties of the MSN-containing nanocomposite scaffolds were significantly higher than the Alg/Chit composite, suggesting the potential of these nanoparticles for bone tissue engineering applications. Taken together, it is concluded that the Alg/Chit/ MSN30 scaffolds are considerable substances for bone tissue regeneration, and MSN has a great tissue engineering potential in addition to its extensive biomedical applications.
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All authors Satar Yousefiasl, Hamed Manoochehri, Pooyan Makvandi, Saeid Afshar, Erfan Salahinejad, Pegah Khosraviyan, Massoud Saidijam, Sara Soleimani Asl, Esmaeel Sharifi
Materials Science · Cross-listed from quant-ph
Designing quantum technologies with a quantum computer
Juan Naranjo, Thi Ha Kyaw, Gaurav Saxena et al. (+2 more)
Interacting
spin systems in solids underpin a wide range of
quantum technologies, from
quantum sensors and single-
photon sources to
spin-defect-based
quantum registers and processors. We develop a
quantum-computer-aided framework for simulating such devices using a general many-body electron-
spin-resonance
Hamiltonian that incorporates zero-field splitting, the Zeeman effect, hyperfine interactions, dipole-dipole
spin-
spin interactions, and electron-
phonon decoherence. Within this framework, we combine Gray-encoded qudit-to-
qubit mappings,
qubit-wise commuting aggregation, and a multi-reference selected
quantum Krylov fast-forwarding hybrid
algorithm, aiming to access extended-time dynamics within the constraints of NISQ and early fault-tolerant hardware. Numerical simulations demonstrate the computation of operationally useful quantities including autocorrelation functions up to $\sim100$ ns, together with microwave absorption spectra and the $\ell_1$-norm of coherence, achieving 18-30$\%$ reductions in gate counts and
circuit depth for Trotterized time-
evolution circuits compared to unoptimized implementations. Using the nitrogen vacancy center in diamond as a testbed, we
benchmark the framework against classical simulations and identify the reference-state selection in sQKFF as the primary factor governing accuracy at fixed hardware cost. This methodology provides a flexible blueprint for using
quantum computers to design, compare, and optimize solid-state
spin-
qubit technologies under experimentally realistic conditions.
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All authors Juan Naranjo, Thi Ha Kyaw, Gaurav Saxena, Kevin Ferreira, Jack S. Baker
Materials Science
Universal Multifractality at the Topological Anderson Insulator Transition
Ksenija Kovalenka, Ahmad Ranjbar, Sam Azadi et al. (+3 more)
Disorder is ubiquitous in
quantum materials, and its interplay with
topology can generate phases absent in the clean limit. Using the Haldane model as a minimal setting, we show that disorder not only shifts topological boundaries but also stabilizes a topological Anderson
insulator (TAI) between trivial and Chern insulating regimes. Employing the local Chern marker as a real-space topological probe, we map the full phase diagram and demonstrate that the TAI forms a finite domain bounded by trivial and Anderson
insulators. Multifractal analysis of low-energy eigenstates at the boundary reveals universal critical spectra, independent of whether disorder generates or destroys
topology. These results place
topology, localization, and criticality within a unified framework and provide clear
benchmarks for real-space diagnostics of disordered topological phases.
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All authors Ksenija Kovalenka, Ahmad Ranjbar, Sam Azadi, Rodion Vladimirovich Belosludov, Thomas D. Kühne, Mohammad Saeed Bahramy
Materials Science · Cross-listed from physics.chem-ph
Molecular structure, binding, and disorder in TDBC-Ag plexcitonic assemblies
J. Baños-Gutiérrez, R. Bercy, Y. García Jomaso et al. (+5 more)
Plexcitonic assemblies are hybrid materials composed of a plasmonic nanoparticle and molecular or semiconducting emitters whose electronic transitions are strongly coupled to the plasmonic mode. This coupling hybridizes the system modes into upper and lower polariton branches. The strength of the interaction depends on the number of emitters and on their orientation and spatial arrangement relative to the metallic surface. These structural factors have profound consequences for the ensuing photoexcited dynamics. Despite the extensive spectroscopic work on plexcitonic systems, direct understanding of the molecular geometry at the metal interface remains limited. In this work, we present a comprehensive structural characterization of one of the most widely studied plexcitons formed by the cyanine dye 5,5',6,6'-tetrachloro-1,1'-diethyl-3,3'-di(4-sulfobutyl)-benzimidazolocarbocyanine (TDBC) and silver nanoprisms using a combination of NMR, THz-Raman spectroscopy, and DFT calculations. By comparing the signals from the monomeric and aggregated forms of TDBC with that of the plexciton, we identify shared spectral fingerprints that reveal how molecular packing is modified when the aggregate adsorbs on the silver surface. We observe Raman modes specific to plexciton systems, and identify NOESY cross-peaks in the aliphatic region, that along with THz-Raman modes in the 10-400 cm$^{-1}$ region are sensitive indicators of aggregation geometry and adsorption. We find that isolated TDBC monomers adopt an asymmetric conformation in which both sulfobutyl chains lie on the same side of the chromophore, while J-aggregates adopt a symmetric up-down alternation of the chains from molecule to molecule. This work establishes the molecular geometry of a prototypical TDBC-silver plexciton, providing a structural
benchmark for understanding geometry-dependent photophysics in hybrid
exciton-plasmon systems.
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All authors J. Baños-Gutiérrez, R. Bercy, Y. García Jomaso, S. Balci, G. Pirruccio, J. Halldin Stenlid, M.J. Llansola-Portoles, D. Finkelstein-Shapiro
Materials Science
MEIDNet: Multimodal generative AI framework for inverse materials design
Anand Babu, Rogério Almeida Gouvêa, Pierre Vandergheynst et al. (+1 more)
In this work, we present
Multimodal Equivariant Inverse Design Network (MEIDNet), a framework that jointly learns structural information and materials properties through contrastive learning, while encoding structures via an equivariant graph neural network (EGNN). By combining generative inverse design with
multimodal learning, our approach accelerates the exploration of chemical-structural space and facilitates the discovery of materials that satisfy predefined property targets. MEIDNet exhibits strong latent-space
alignment with cosine similarity 0.96 by fusion of three modalities through cross-modal learning. Through implementation of curriculum learning strategies, MEIDNet achieves ~60 times higher learning efficiency than conventional training techniques. The potential of our
multimodal approach is demonstrated by generating low-bandgap perovskite structures at a stable, unique, and novel (SUN) rate of 13.6 %, which are further validated by ab initio methods. Our inverse design framework demonstrates both scalability and adaptability, paving the way for the universal learning of chemical space across diverse modalities.
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All authors Anand Babu, Rogério Almeida Gouvêa, Pierre Vandergheynst, Gian-Marco Rignanese
Materials Science
Fabrication effects on Niobium oxidation and surface contamination in Niobium-metal bilayers using X-ray photoelectron spectroscopy
Tathagata Banerjee, Maciej W. Olszewski and Valla Fatemi
Superconducting resonators and
qubits are limited by dielectric losses from surface
oxides. Surface
oxides are mitigated through various strategies such as the addition of a metal capping layer, surface passivation, and acid processing. In this study, we demonstrate the use of X-ray photoelectron spectroscopy (XPS) as a rapid characterization tool to study the effectiveness cap layers for niobium for further device fabrication. We non-destructively evaluate 17 capping layers to characterize their ability to prevent oxygen
diffusion, and the effects of standard fabrication processes – annealing, resist stripping, and acid cleaning. We downselect for resilient capping layers and test their microwave resonator performance.
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Materials Science
Watching Polarons Form in Real Time
Victor Garcia-Herrero, Christoph Emeis, Zhenbang Dai et al. (+3 more)
Polaron formation in pump-probe experiments is an inherently non-
equilibrium phenomenon, driven by the ultrafast coupled dynamics of electrons and
phonons, and culminating in the emergence of a localized quasiparticle state. In this work, we present a first-principles
quantum-kinetic theory of polaron formation that captures the real-time
evolution of electronic and
lattice degrees of freedom in presence of electron-
phonon coupling. We implement this framework to investigate the ultrafast polaron formation in the prototypical polar
insulator MgO. This approach allows us to determine the characteristic timescales of polaron localization and to identify its distinctive dynamical fingerprint. Our results establish clear and experimentally accessible criteria for identifying polaron formation in pump-probe experiments.
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All authors Victor Garcia-Herrero, Christoph Emeis, Zhenbang Dai, Jon Lafuente-Bartolome, Feliciano Giustino, Fabio Caruso
Materials Science
Rate Equation for the Transfer of Interstitials across Interfaces between Equilibrated Crystals
Jörg Weissmüller
This work inspects the thermally activated transfer of solute particles across the interface between two interstitial solid solution phases that equilibrate internally by fast
diffusion on conserved arrays of sites. When each phase is considered as an ergodic ensemble of particles, statistical mechanics predicts the occupancy of the transition states at
equilibrium to depend on the barrier energy and on the chemical potentials and vacancy fractions in each of the phases. A rate law for the non-
equilibrium interfacial transfer, based on a constant transition probability between activated states, naturally satisfies the principle of detailed balance. Contrary to Butler-Volmer-type laws, values of the particle chemical potentials enter explicitly rather than through their difference. This, along with the dependency on the vacancy fractions, implies here an exchange flux density that depends explicitly on the compositions at
equilibrium. The results can explain experimental observations of a drastic slow-down in the charging of metal hydrides near phase transformations or miscibility-gap critical points.
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Materials Science
Synthetic control over marcasite-pyrite polymorph formation in the Fe1-xCoxSe2 series
Luqman Mustafa, Susanne Kunzmann, Martin Kostka et al. (+7 more)
Transition-metal dichalcogenides of the pyrite-marcasite family are model systems of
crystal chemistry. A few of these show polymorphism. The theoretical ground state of CoSe2 is marcasite, but the material is typically synthesized in the pyrite structure. Polymorphism has been observed in nanoparticles and synthetic control of the polymorphs of CoSe2 has not been achieved. We have synthesized material libraries of the Fe1-xCoxSe2 series by combining combinatorial deposition and ex-situ selenization. The approach allows to efficiently explore substitution ranges and
crystal structures that form for different synthesis conditions. We find that higher levels of Co content x within the marcasite structure are possible when synthesizing at low temperatures. At a synthesis temperature of only 250{\deg} C, we have successfully synthesized marcasite CoSe2 as the majority phase. Density functional theory simulations reveal that the two isomorphs of CoSe2 are extremely close in energy and that the orthorhombic phase is the energetic ground state. Our experimental and theoretical data show that the marcasite structure is the
equilibrium phase of Fe1-xCoxSe2 in the entire composition range.
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All authors Luqman Mustafa, Susanne Kunzmann, Martin Kostka, Jill Fortmann, Aurelija Mockute, Alan Savan, Alfred Ludwig, Anna Grünebohm, Andreas Kreyssig, Anna E. Böhmer
Materials Science
Model density approach to Ewald summations
Chiara Ribaldone and Jacques Kontak Desmarais
The evaluation of the electrostatic potential is fundamental to the study of condensed phase systems. We discuss the calculation of the relevant
lattice summations by Ewald-type techniques. A model charge density is introduced, that cancels multipole moments of the crystalline charge distribution up to a desired order, for accelerating convergence of the Ewald sums. The method is applicable to calculations of bulk systems, employing arbitrary unit
cells in a classical or
quantum context, and with arbitrary basis functions to represent the charge density. The efficacy of the method is demonstrated on the calculation of the fundamental gap of the gallium arsenide bulk
semiconductor, as a prototype example, where significantly accelerated convergence is numerically confirmed, due to a reduction of the number of two-electron integrals that need to be computed. The approach clarifies a decades-old implementation in the
CRYSTAL code.
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Materials Science
Ultra-complex conductivity diagrams in the nearly free electron approximation
A.Ya. Maltsev
We investigate the possibility of the emergence of ultra-complex conductivity diagrams in the nearly free electron approximation for metals with cubic
symmetry. Estimates show that the emergence of such diagrams requires the
Fermi level to fall into very narrow energy intervals within the conduction band. In our view, this circumstance is mostly due to the high
symmetry and the simplest analytical form of the dispersion relations $\epsilon ({\bf p})$ under consideration.
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Materials Science
Impact of hydrogen incorporation on electronic and magnetic structure of X2CrNi18-9 stainless steel
Torben Tappe, Louis Becker, Gaurav Kanu et al. (+7 more)
Hydrogen absorption significantly alters the mechanical properties of steel. However, absorbed hydrogen also influences its electronic and magneto-structural properties, helping to interpret how hydrogen is incorporated. This study therefore investigates the influence of hydrogen incorporation on the electronic and magneto-structural properties of X2CrNi18-9 stainless steel in different microstructural states. Microstructural characterization included analytic electron microscopy mapping, X-ray diffraction and thermodynamic stability maps to evaluate grain size, dislocation density and chemical homogeneity. The electronic properties were characterized using the Seebeck coefficient, while the magneto-structural properties were investigated using diffuse
neutron scattering and small-angle
neutron scattering (SANS). Hydrogen incorporation showed clear changes in the Seebeck coefficients.
Magnetic SANS in conjunction with diffuse
neutron scattering indicates the existence of nanoscale inhomogeneities with the same fcc structure as the bulk, but with correlation lengths of a few nanometres. The size of these inhomogeneities increased with hydrogen incorporation, suggesting that hydrogen preferentially accumulates in their vicinity. However, no direct correlation between the electronic and magneto-structural properties and the dislocation density could be demonstrated. We suggest that studies such as these will lead in the medium term to the development of guidelines for material design to make steels more resistant to hydrogen.
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All authors Torben Tappe, Louis Becker, Gaurav Kanu, Thomas F. Headen, Dirk Honecker, Gabi Schierning, Santiago Benito, Sebastian Weber, Klara Lünser, Sabrina Disch
Materials Science · Cross-listed from cond-mat.supr-con
Microstructure-controlled vortex phases and two-phase superconductivity in (TaNb)0.7(HfZrTi)0.5 revealed by ac magnetostrictive coefficients
Mengju Yuan, Yuze Xu, Bin Zhang et al. (+5 more)
We investigate flux dynamics in the high-
entropy alloy superconductor (TaNb)0.7(HfZrTi)0.5 after annealing (as-cast, 500 {\deg}C, 550 {\deg}C, and 1000 {\deg}C) using a sensitive ac composite magnetoelectric method that measures the complex ac magnetostrictive coefficient (d{\lambda}/dH)ac. The resulting
vortex phase diagrams show that intermediate annealing (500-550 {\deg}C) induces nanoscale clustering, enhances pinning, and produces a pronounced fishtail effect with successive elastic- and plastic-
vortex-glass regimes. Flux-jump instabilities appear at 550 {\deg}C and persist at 1000 {\deg}C, indicating strong pinning and thermomagnetic instability in the low-temperature, low-field regime. Remarkably, the 1000 {\deg}C sample exhibits a two-step superconducting response-a double plateau or drop in d{\lambda}'/dH and two dissipation peaks in d{\lambda}”/dH-demonstrating the coexistence of two superconducting phases with distinct irreversibility and critical-field value. We further show that the resolvability of the two-step (d{\lambda}/dH)ac signature is governed by the topological connectivity of the phase-separated microstructure, which controls
magnetic shielding between the TaNb-rich network and the (TaNb)0.7(HfZrTi)0.5 parent phase. These results establish a direct microstructure-
vortex-state correlation and provide a route to tailoring flux pinning in chemically complex
superconductors via thermal processing.
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All authors Mengju Yuan, Yuze Xu, Bin Zhang, Jun-Yi Ge, Aifeng Wang, Mingquan He, Yanpeng Qi, Yisheng Chai
Materials Science · Cross-listed from cond-mat.mes-hall
Deeply nonlinear magnon-photon hybrid excitation
Dinesh Wagle, Anish Rai and M. Benjamin Jungfleisch
We investigate the microwave-power dependence of
magnon-
photon coupling in a yttrium iron garnet-sphere/split-ring-resonator hybrid system at room temperature and demonstrate that nonlinear
spin-wave interactions suppress the coupling through power-induced dissipation of magnetostatic modes. At low microwave power, the modes exhibit pronounced level repulsion, evidencing strong coupling to the microwave field. As the power increases, however,
magnon linewidth broadening progressively weakens the coupling and ultimately suppresses it entirely below a threshold external
magnetic field. We show that this behavior originates from Suhl's first-order instability: magnetostatic modes, which couple to the resonator, parametrically excites two counter-propagating
magnons at half its frequency, causing modes below the threshold external
magnetic field to vanish. In contrast,
magnon modes above the threshold field remain robust even at high power, as the instability criterion is not satisfied in that regime. These results reveal a well-defined nonlinear boundary for
magnon-
photon coupled systems and highlight a favorable regime for exploiting nonlinear magnonics for frequency conversion, switching, and other functional magnonic devices.
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Materials Science
Sustainable Materials Discovery in the Era of Artificial Intelligence
Sajid Mannan, Rupert J. Myers, Rohit Batra et al. (+3 more)
Artificial intelligence (AI) has transformed materials discovery, enabling rapid exploration of chemical space through generative models and surrogate screening. Yet current generative AI models for materials discovery, which now drive exploration of vast chemical and structural spaces, optimize candidates exclusively for structural stability and functional properties, with no integration of environmental assessment at any stage of the design loop. Prospective and ex-ante life cycle assessment methods exist and have been applied to emerging technologies, but they operate as standalone downstream analyses, not as active constraints within generative or active-learning pipelines. The result is that environmental feedback, even when produced, arrives after design decisions have been made rather than informing them. The disconnect between atomic-scale design and lifecycle assessment (LCA) reflects fundamental challenges: (i) data scarcity across heterogeneous sources, (ii) scale gaps from atoms to industrial systems, (iii) uncertainty in synthesis pathways, and (iv) the absence of frameworks that co-optimize performance with environmental impact. In this Perspective, we propose integrating upstream ML-assisted materials discovery with downstream LCA into the ML-LCA framework, comprising five components: information extraction for building materials-environment knowledge bases, harmonized databases linking properties to sustainability metrics, multi-scale models bridging atomic properties to lifecycle impacts, ensemble prediction of manufacturing pathways with uncertainty quantification, and uncertainty-aware optimization enabling simultaneous performance-sustainability
navigation. Case studies spanning
polymers, glass, photoresists, and cement demonstrate both necessity and feasibility while identifying material-specific integration challenges.
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All authors Sajid Mannan, Rupert J. Myers, Rohit Batra, Rocio Mercado, Lothar Wondraczek, N. M. Anoop Krishnan
Materials Science · Cross-listed from physics.optics
Hybrid Barium Titanate Waveguide Designs For Efficient Nonlinear Frequency Conversion
Trevor G. Vrckovnik, D. Arslan, F. Eilenberger et al. (+1 more)
Barium titanate (BaTiO$_3$) is emerging as a powerful integrated photonic material, combining strong $X^{(2)}$ and electro-optic nonlinearities with rapidly improving thin-film waveguide quality. Recent demonstrations of low-loss BaTiO$_3$ waveguides and high-Q resonators have established BaTiO$_3$-on-
insulator as a promising platform for next-generation frequency-conversion and
quantum photonic technologies. However, while BaTiO$_3$ electro-optic modulators are now well developed, nonlinear BaTiO$_3$ waveguide engineering remains comparatively immature. Techniques widely used in lithium niobate, such as periodic poling for quasi-phase-matching, are poorly suited to BaTiO$_3$ because epitaxial thin films exhibit high coercive fields, strong strain-clamping effects, multivariant domain structures, and slow, complex switching dynamics. These factors make accurate periodic poling challenging and hinder the development of efficient $X^{(2)}$ frequency converters. Here, we introduce a fabrication-robust alternative based on linear-nonlinear hybrid waveguides, where TiO$_2$ is selectively incorporated into BaTiO$_3$ ridge waveguides to enhance nonlinear mode overlap while relying solely on modal phase-matching. Using coupled-mode-theory simulations, we identify phase-matched geometries and show that the hybrid design achieves a 2.75x increase in normalized second harmonic generation efficiency over monolithic BaTiO$_3$ waveguides. The uniform, lithographically defined cross-section makes the approach highly scalable. These results position hybrid BaTiO$_3$-TiO$_2$ waveguides as a practical route to CMOS-compatible, high-efficiency $X^{(2)}$ devices for integrated
quantum photonics.
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All authors Trevor G. Vrckovnik, D. Arslan, F. Eilenberger, Sebastian W. Schmitt
Materials Science
Screening 39 billion protostructures for materials discovery
Abhijith S Parackal, Florian Trybel, Felix Andreas Faber et al. (+1 more)
Large-scale computational surveys are increasingly used to map the landscape of stable crystalline materials. We report a high-throughput energy screening of inorganic
crystals that enumerates binary and ternary compositions up to a specified unit-
cell complexity, yielding 39 billion protostructures. Candidates predicted to lie on or near the convex hull are retained, and their degrees of freedom are explored via Latin hypercube sampling followed by relaxation with machine-learned interatomic potentials. The resulting
dataset contains 81 million locally relaxed
crystal structures spanning 4495 ternary phase diagrams constructed from elements ranging from lithium to bromine and contains 88,498
crystal prototypes not present in existing
crystal-structure databases. The methods are validated both for three well-explored materials systems, Zr-Zn-N, Ti-Zn-N, and Hf-Zn-N, and by comparing with known data for structures resulting from the larger screening. The work provides a systematic map of low-energy compositional-structural space and a large, structured pool of candidates for downstream property evaluation and materials design.
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All authors Abhijith S Parackal, Florian Trybel, Felix Andreas Faber, Rickard Armiento
Materials Science
High-Pressure Torsion-Induced Transformation of Adenosine Monophosphate: Insights into Prebiotic Chemistry of RNA by Astronomical Impacts
Kaveh Edalati, Jacqueline Hidalgo-Jimenez and Thanh Tam Nguyen
The origin of life is yet a compelling scientific mystery that has sometimes been attributed to high-pressure impacts by small
solar system bodies such as comets, meteoroids, asteroids, and transitional objects. High-pressure torsion (HPT) is an innovative method with which to simulate the extreme conditions of astronomical impacts and offers insights relevant to prebiotic chemistry. In the present study, we investigated the polymerization and stability of adenosine monophosphate (AMP), a key precursor to ribonucleic acid (RNA), in dry and hydrated conditions (10 wt% water) under 6 GPa at ambient and boiling water temperatures. Comprehensive analyses with the use of X-ray diffraction, Raman spectroscopy,
Fourier-transform infrared spectroscopy,
nuclear magnetic resonance, scanning electron microscopy, and
matrix-assisted
laser desorption/ionization time-of-flight mass spectrometry revealed no evidence of polymerization, while AMP partly transformed to other organic compounds such as nucleobase-derived fragments of adenine, phosphoribose fragments, dehydrated adenosine, protonated adenosine, and oxidized adenosine. The torque measurements during HPT further highlight the mechanical behavior of AMP under extreme conditions. These findings suggest that, while HPT under the conditions tested does not facilitate polymerization, the formation of various compounds from AMP confirms the significance of astronomical impacts on the prebiotic chemistry of RNA on early Earth. Keywords: Ribonucleic acid (RNA), Origin of life; Phase transformations; Chemical reactions, Small
solar system bodies
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Materials Science
Numerical Diagonalization Study of the Phase Boundaries of the S=2 Heisenberg Antiferromagnet on the Orthogonal Dimer Lattice
Hiroki Nakano, Toru Sakai and Yuko Hosokoshi
The S=2 Heisenberg antiferromagnet on the orthogonal dimer
lattice is studied. The edges of the exact dimer and Neel-ordered phases in the ground state of the system are examined by the numerical diagonalization method. Our present results are discussed by combining them with previously obtained estimates for smaller-S cases. We find that an intermediate region between the exact dimer and Neel-ordered phases gradually widens as
spin S is increased up to S=2.
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Materials Science
Transferable mechanism of perpendicular magnetic anisotropy switching by hole doping in V$X_2$ ($X$=Te, Se, S) monolayers
John Lawrence Euste, Maha Hsouna and Nataša Stojić
The ability to tune and switch
magnetic anisotropy to a perpendicular orientation is a key challenge for implementing 2D magnets in spintronic devices. H-phase vanadium dichalcogenides V$X_2$ ($X$=Te, Se, S) are promising
ferromagnetic semiconductors with large
magnetic anisotropy energy (MAE). Recent work has shown that hole doping can switch their easy axis to out-of-plane, though the microscopic origin of this perpendicular
magnetic anisotropy (PMA) remains unclear. Using density-functional-theory calculations, we demonstrate that the PMA enhancement arises from first-order
spin-orbit coupling (SOC) acting on topmost degenerate valence states with nonzero orbital angular momentum projection ($m_l\ne 0$). In this case, the $\hat{L}_z\hat{S}_z$ term dominates for perpendicular magnetization, while in-plane orientations involve only weaker, second-order SOC contributions. The increased valence bandwidth leads to depletion of higher-energy states upon hole doping, stabilizing PMA. From this mechanism, we identify two transferable design principles for enhancing MAE under weak hole doping: (i) orbital degeneracy at the valence-band edge protected by point-group
symmetry and (ii) finite SOC in the degenerate
manifold. Notably, we identify multiple
magnetic semiconductors that meet these criteria and display enhanced MAE under hole doping. Furthermore, we show that band engineering can strategically place these degenerate orbitals at the valence band edge, significantly boosting PMA when hole-doped. We also examine trends in VTe$_2$, VSe$_2$, and VS$_2$ to determine the influence of
crystal-field splitting, exchange interaction, and orbital hybridization on the valence band edges. These results provide both a fundamental understanding of PMA switching upon hole doping and a transferable strategy for tuning
magnetic anisotropy, essential for designing high-performance spintronic materials.
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Materials Science
Dynamically training machine-learning-based force fields for strongly anharmonic materials
Martin Callsen, Tai-Ting Lee and Mei-Yin Chou
Machine learning (ML) force fields have emerged as a powerful tool for computing materials properties at finite temperatures, particularly in regimes where traditional
phonon-based perturbation theories fail or cannot be extended beyond the harmonic approximation. These approaches offer accuracy comparable to ab initio molecular dynamics (MD), but at a fraction of the computational cost. However, their reliability critically depends on the quality and representativeness of the training data. In particular, static training
datasets often lead to failure when the force field encounters previously unseen atomic configurations during MD simulations. In this work, we present a framework for dynamically training ML force fields and demonstrate its effectiveness across materials with varying degrees of anharmonicity, including cubic boron arsenide (c-BAs), silicon (Si), and tin selenide (SnSe). Our method builds on the conventional
lattice dynamics expansion of total energy and incorporates
Bayesian error estimation to guide adaptive data acquisition during simulation. Specifically, we show that trajectory-averaged
Bayesian errors enable efficient and targeted exploration of the configuration space, significantly enhancing the robustness and transferability of the resulting force fields. We further demonstrate how
Bayesian error estimation can be applied to determine the convergence of the dynamic training without requiring additional ab initio data. This proposed framework offers a practical and easily implementable scheme to improve the training process, which is the most critical step in developing reliable ML force fields.
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Materials Science
Efficient high-harmonic generation in van der Waals ferroelectric NbOI$_2$ crystals
Tianchen Hu, Feng Li, Junhan Huang et al. (+8 more)
Layered NbOX$_2$ ($X=\mathrm{Cl,\,Br,\,I}$), a member of the van der Waals ferroelectric family, exhibits intrinsic ferroelectricity and pronounced nonlinear optical responses, making it a promising candidate for integrated nanophotonics applications. While previous studies have emphasized the material's strong second-order nonlinear responses, higher-order nonlinear responses are still mostly unexplored. This work systematically investigates NbOI$_2$ using high harmonic generation (HHG) spectroscopy. Driven by an intense mid-infrared
laser field centered at $\sim4~\mu\mathrm{m}$ wavelength, highly anisotropic odd- and even-order harmonics up to the 16th order are generated at a low peak intensity of $0.4~\mathrm{TW\,cm^{-2}}$, extending beyond the material's bandgap. Both bulk and flake forms of NbOI$_2$ display pronounced harmonic emission from the near-infrared to the deep-ultraviolet spectral region, with a notably high overall conversion efficiency compared to other known materials. Polarization-resolved measurements reveal that even-order harmonics remain aligned with the
crystal polar axis regardless of the driving-field orientation, whereas odd-order harmonics are dynamically affected. First-principles calculations suggest that the flat valence band associated with Peierls dimerization enhances HHG efficiency through electron correlation. These findings provide fresh perspectives on HHG in van der Waals ferroelectric materials and facilitate the development of compact and tunable
quantum light sources.
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All authors Tianchen Hu, Feng Li, Junhan Huang, Chen Qian, Ruoxuan Ding, Hao Wang, Qiaomei Liu, Qiong Wu, Ruifeng Lu, Chunmei Zhang, Nanlin Wang
Materials Science
Metal Halide Perovskites for Violet and Ultraviolet Light Emission
Sebastian Fernández, Manchen Hu, Tyler K. Colenbrander et al. (+2 more)
Emissive metal halide perovskites (MHPs) have emerged as excellent candidates for next-generation optoelectronics due to their sharp color purity, inexpensive processing, and bandgap tunability. However, the development of violet and ultraviolet light-emitting MHPs has lagged behind due to challenges related to material and device stability, charge carrier transport, tunability into the ultraviolet spectrum, toxicity, and scalability. Here, we review the progress of both violet and ultraviolet MHP nanomaterials and light-emitting diodes, including materials synthesis and device fabrication across various
crystal structures and dimensions (e.g., bulk thin films, 2D thin films, nanoplatelets, colloidal nanocrystals, and more) as well as lead-free platforms (e.g., rare-earth metal halide perovskites). By highlighting several pathways to continue the development of violet and ultraviolet light-emitting MHPs while also proposing tactics to overcome their outstanding challenges, we demonstrate the potential of state-of-the-art violet and ultraviolet MHP materials and devices for important applications in public health, 3D printing, nanofabrication, and more.
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All authors Sebastian Fernández, Manchen Hu, Tyler K. Colenbrander, Divine Mbachu, Daniel N. Congreve
Materials Science
Model-free Analysis of Scattering and Imaging Data with Escort-Weighted Shannon Entropy and Divergence Matrices
Jared Coles, Arthur R. C. McCray, Yue Li et al. (+9 more)
We demonstrate a model-free data analysis framework that leverages escort-weighted Shannon
Entropy and several divergence
matrices to detect phase transitions in scattering and imaging
datasets. By establishing a connection between physical
entropy and informational
entropy, this approach provides a sensitive method for identifying phase transitions without an explicit physical model or order parameter. We further show that pairwise divergence
matrices, including Kullback-Leibler divergence, Jeffrey Divergence, Jensen-Shannon Divergence and antisymmetric Kullback-Leibler divergence, provide more comprehensive measures of statistical changes than scalar
entropy alone. Our approach successfully detects the onset of both long- and short-range order in
neutron and X-ray scattering data, as well as a non-trivial phase transition in
magnetic skyrmion
lattices observed through Lorentz-transition electron microscopy. These results establish a framework for automated, model-free analysis of experimental data with broad applications in materials science and condensed matter physics.
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All authors Jared Coles, Arthur R. C. McCray, Yue Li, Bryan T. Fichera, Yan Wu, Yiqing Hao, Daniel Phelan, Yue Cao, Raymond Osborn, C. Phatak, Stephan Rosenkranz, Yu Li
Materials Science · Cross-listed from cond-mat.mes-hall
One-Dimensional Electronic States in a Moiré Superlattice of Twisted Bilayer WTe2
Takuto Kawakami, Hayato Tateish, Daiki Yoshida et al. (+10 more)
One-dimensional (1D) moiré superlattices provide a new route to engineering reduced-dimensional electronic states in van der Waals materials, yet their electronic structure and microscopic origin remain largely unexplored. Here, we investigate the structural relaxation and electronic properties of a 1D moiré superlattice formed in twisted
bilayer 1T$'$-WTe$_2$ using density functional theory calculations, complemented by high-angle annular dark-field scanning transmission electron microscopy. We show that
lattice relaxation strongly reconstructs the moiré stripes, leading to stacking-dependent stripe widths that are in excellent agreement with experimental observations. The relaxed structure hosts quasi-one-dimensional electronic bands near the
Fermi level, characterized by strong dispersion along the stripe direction and nearly flat dispersion in the perpendicular direction. By comparing the full
bilayer with isolated relaxed layers, we establish that these 1D electronic states are governed predominantly by an intralayer moiré potential induced by in-plane
lattice relaxation, rather than by interlayer hybridization. We extract this position-dependent moiré potential directly from DFT calculations and construct an effective tight-binding model that reproduces both the band dispersion and the real-space localization of the electronic wave functions. Our results identify
lattice relaxation as the key mechanism underlying 1D electronic states in 1D moiré superlattices. %and establish twisted
bilayer WTe$_2$ as a promising platform for exploring emergent one-dimensional moiré physics. The framework developed here provides a unified theoretical basis for realizing and exploring one-dimensional moiré physics in a broad class of anisotropic two-dimensional materials.
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All authors Takuto Kawakami, Hayato Tateish, Daiki Yoshida, Xiaohan Yang, Naoto Nakatsuji, Limi Chen, Kohei Aso, Yukiko Yamada-Takamura, Yoshifumi Oshima, Yijin Zhang, Tomoki Machida, Koichiro Kato, Mikito Koshino
Materials Science
Bo Yuan, Yingxi Bai, Ying Dai et al. (+2 more)
Altermagnetism has attracted considerable interest, yet its associated spintronic phenomena have so far been largely confined to electronic systems. In this work, we uncover a universal
symmetry-based strategy for realizing topological altermagnets with the magnonic
quantum spin Hall effect, as evidenced by a nonzero
spin Chern number and protected helical edge states. Moreover, we demonstrate that
chiral magnon splitting in altermagnets gives rise to an intrinsically anisotropic, momentum-resolved thermal
Hall response, sharply contrasting with those in ferromagnets and antiferromagnets, thus offering enhanced flexibility for selective manipulation. As a concrete material realization, first-principles calculations and Heisenberg-DM model analysis reveal that V$_2$WS$_4$
bilayer exhibits $d$-wave altermagnetism, integer
spin Chern number with helical
magnon edge states, and the nonzero momentum-locked thermal
Hall conductivity. Our results establish a direct link between topological
magnons and altermagnetism, opening new avenues for dissipationless magnonic devices.
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All authors Bo Yuan, Yingxi Bai, Ying Dai, Baibiao Huang, Chengwang Niu
Materials Science · Cross-listed from hep-th
Electric birefringence in Euler-Heisenberg pseudo-electrodynamics
M. J. Neves
The
fermion sector of the pseudo-
quantum electrodynamics is integrated functionally to generate a non-linear electrodynamics, that it is called Euler-Heisenberg pseudo-electrodynamics. A non-local Chern-Simons topological term is added to the original lagrangian of the pseudo-
quantum electrodynamics in which a most complete electrodynamics gauge invariant in 1+2 dimensions is proposed. As consequence of the fermionic sector, we obtain a non-linear contribution in the electromagnetic fields that breaks the Lorentz
symmetry due to
Fermi velocity. From the Euler-Heisenberg pseudo-electrodynamics, we study the properties of the plane wave propagating in a planar medium under an uniform and constant electromagnetic background field. The properties of the planar material are discussed through the electric permittivity tensor and
magnetic permeability, that are functions of the frequency, wavelength and of the background fields. The dispersion relations and the refractive index are calculated in the presence of a uniform
magnetic field, and also in the case only of an electric background field. The birefringence phenomenon emerges only when the electric background field is considered.
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