Materials Science · Cross-listed from physics.chem-ph
Catalytic Resonance Theory: Kinetics and Frequency Response of Light-Promoted Catalysis
Paul J Dauenhauer
The illumination of catalytic surfaces with a continuous or pulsed stream of
photons dynamically modulates surface chemistry for faster rates, higher conversion, or product selectivity control. To establish fundamental principles of dynamic
photon-modulated catalysis, the photocatalytic conversion of a generic surface reaction was simulated to understand the kinetic implications of an independent stream of
photons promoting surface product desorption. Simulations were conducted via the microkinetic model and kinetic Monte Carlo methods for the scenarios of a Poisson distribution, constant spacing between
photons, and coordinated on/off pulsing of
photon sources. The time-averaged photocatalytic rate at differential conditions for varying
photon flux and temperatures indicated three kinetic regimes described by product thermal desorption control, surface reaction control, and an intermediate kinetic regime with a zero slope Arrhenius plot, consistent with a degree of rate control dominated by the
photon arrival frequency (i.e., per-site
photon flux). The maximum photocatalytic rate occurred orders of magnitude above the Sabatier limit at the resonance frequency, identified as the
photon arrival frequency that matched the surface reaction rate constant. Non-
equilibrium photocatalytic conversion occurred when the rate of
photon-promoted product desorption was comparable to the rate of thermal product desorption. Results indicated the general utility of
photon-promoted catalysis, with negligible benefit for rate enhancement and
quantum yield with
photon source pulsing or chopping due to the inherent dynamic nature of
photons from light sources.
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Materials Science
Electric-Field-Dependent Thermal Conductivity in Fresh and Aged Bulk Single Crystalline $\mathrm{BaTiO_3}$
Fanghao Zhang, Guanchun Rui, Yujie Quan et al. (+4 more)
Active thermal management requires advances in thermal switching materials, whose thermal conductivity responds to external stimuli. The electric field, as one of the most convenient and effective stimuli, has shown great potential in tuning the thermal conductivity of ferroelectric materials. While previous studies on electric-field-induced ferroelectric thermal switching have primarily focused on thin films and bulk solid solutions with strong extrinsic interface and defect scatterings, bulk single
crystals, which can offer clear insights into intrinsic thermal switching mechanisms, have received comparatively less
attention. Here, we demonstrate electric-field-induced thermal switching in bulk single-crystalline $\mathrm{BaTiO_3}$ (BTO) at room temperature and elucidate the critical role of domain
evolution and aging in governing heat transport. Using a customized steady-state platform with in-situ electric fields up to $\pm$10 kV/cm, we observe a modulation of thermal conductivity up to 35% in fresh BTO driven by polarization reorientation and domain restructuring. First-principles finite-temperature
lattice-dynamics calculations confirm that the switching behavior primarily originates from anisotropic
phonon transport associated with domain configuration rather than strain-induced changes in
phonon velocities. We further reveal that both ambient aging and controlled thermal aging can enhance the switching contrast through the formation and
alignment of defect dipoles that modulate
phonon-defect scattering. These results establish defect-domain interactions as a powerful design parameter for ferroelectric thermal switches and demonstrate a versatile experimental platform for exploring field-tunable heat transport and phase behavior in bulk functional materials.
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All authors Fanghao Zhang, Guanchun Rui, Yujie Quan, Shantal Adajian, Matthew Delmont, Q. M. Zhang, Bolin Liao
Materials Science · Cross-listed from cond-mat.str-el
Spin-quenching in molecule-transition-metal-dichalcogenide heterostructure through inverse proximity effect
Swagata Acharya, Dimitar Pashov, Daphne Lubert-Perquel et al. (+2 more)
A functional
heterostructure is central to integrated circuitry in
quantum photonics, optoelectronics, neuromorphic computing, spintronics, and straintronics. Recently,
heterostructures combining 2D magnets and nonmagnetic transition metal dichalcogenides (TMDs) have been explored. In these, electron and hole wavefunctions are localized in 2D magnets but delocalized in TMDs. When combined, a proximity induced
magnetic inter layer
exciton can emerge, with energy differing by 20 to 30 meV from intra layer
excitons and being two orders of magnitude darker, making it hard to detect and functionalize. Using a high fidelity ab initio many body diagrammatic approach, we show that functionality can be significantly enhanced in a transition metal molecule TMD interface. The molecular
exciton exhibits charge transfer character and is extended, unlike the localized Frenkel excitation in 2D magnets. Moreover, the degree of localization and
magnetic moment can be tuned by varying the molecular orientation relative to the TMD. This changes the proximity to the
magnetic ion, altering screening and enabling a pathway to quench the ion's
spin moment. This inverse proximity effect tunes the energies,
spin states, and brightness of molecular and inter layer
magnetic excitons, a mechanism absent in 2D magnet TMD systems. We also identify conditions under which the interlayer
exciton becomes well separated and brighter than intra layer
excitons, making it promising for protocols that probe and manipulate
magnetic excitonic states.
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All authors Swagata Acharya, Dimitar Pashov, Daphne Lubert-Perquel, Mark van Schilfgaarde, Justin C. Johnson
Materials Science
Third-Body Stabilization of Supercritical CO2 in CO Oxidation: Development and Application of a ReaxFF Force Field for the CO/O/CO2 System
Emdadul Haque Chowdhury, Masoud Aryanpour, Yun Kyung Shin et al. (+3 more)
Supercritical CO2 (scCO2) plays a crucial role as a solvent in separation processes, advanced power cycles, and materials processing. Nonetheless, the atomistic comprehension of how the dense scCO2
matrix influences the fundamental reaction of carbon monoxide (CO) is still insufficiently explored. Experimental studies and molecular dynamics (MD) simulations frequently fail to detect the highly reactive, transient intermediates, such as atomic oxygen (O), that drive these reactions. To address this issue, we have developed a novel ReaxFF reactive force field for the CO2/CO/O system. The force field parameters were calibrated using density functional theory and second-order Moller-Plesset calculations to model CO2
crystal properties, intermolecular interactions, bond dissociation curves, and reaction energy barriers. The force field reproduces the cohesive energy of the CO2
crystal, the pressure characteristics of bulk scCO2, the equation-of-state behavior over a wide pressure-density range, the pressure dependence of the C-O bond length under compression, and the structural properties of
liquid and scCO2, as documented by experiments, ab-initio MD, and prominent non-reactive models. The force field was subsequently applied to study the CO + O -> CO2 reaction. In a dilute environment, the reaction is inefficient as the newly formed CO2 rapidly dissociates due to excess kinetic and potential energy acquired from the exothermic reaction. Conversely, in a dense scCO2 environment, the surrounding
matrix acts as an efficient third body, stabilizing the emerging CO2 product via molecular collisions. Statistical analysis confirms an average excess energy dissipation of 133.9 +/- 3.6 kcal/mol over 112.4 +/- 17.9 ps. Kinetic energy decomposition reveals that approximately 92% of the excess kinetic energy is stored in internal (rotational and vibrational) degrees of freedom.
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All authors Emdadul Haque Chowdhury, Masoud Aryanpour, Yun Kyung Shin, Bladimir Ramos-Alvarado, Matthias Ihme, Adri van Duin
Materials Science · Cross-listed from cond-mat.str-el
Origin of metal-insulator transition in rare-earth Nickelates
Swagata Acharya, Brooks Tellekamp, Jerome Jackson et al. (+4 more)
Rare-earth nickelates RNiO3 (R=rare-earth element) exhibit three kinds of phase transitions with decreasing temperature: a structural transition from a pseudo-cubic to a monoclinic phase, a metal-
insulator transition (MIT), and a
magnetic transition from a paramagnetic state to an ordered one. The first two occur at the same temperature, which has led to a consensus that the MIT is driven by
lattice distortions. We show here that the primary driving force for the MIT is
magnetic; however because of the unusual d7 configuration of Ni, additional flexibility in
spin configurations are also needed which
symmetry-lowing structural deformations make possible. The latter enable Ni to disproportionate into two kinds: a high-
spin and a low-
spin configuration, which allow the system to reduce its unfavorable orbital moment and also open a gap.
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All authors Swagata Acharya, Brooks Tellekamp, Jerome Jackson, Dimitar Pashov, Jeffrey L. Blackburn, Kirstin Alberi, Mark van Schilfgaarde
Materials Science
Photoemission tomography of excitons in 2D systems: momentum-space signatures of correlated electron-hole wave functions
Siegfried Kaidisch, Amir Kleiner, Sivan Refaely-Abramson et al. (+2 more)
The momentum-space signatures of
excitons can be experimentally accessed through time-resolved (pump-probe) photoelectron spectroscopy. In this work, we develop a computational framework for
exciton photoemission orbital
tomography (exPOT) in periodic systems, enabling the simulation and interpretation of experimental observables within many-body perturbation theory. By connecting the GW +Bethe-Salpeter equation (BSE) approach to photoemission
tomography, our formalism captures
exciton photoemission in periodic systems, explicitly incorporating photoemission
matrix element effects induced by the light-matter interaction via the probe pulse. The correlated nature of electrons and holes introduces distinct consequences for excitonic photoemission. Using the prototypical two-dimensional material hexagonal boron nitride, we demonstrate these effects, including a dependence of the photoemission angular distribution on the pump pulse polarization. Moreover, our framework extends to
excitons with finite center-of-mass momentum, making it well-suited to studying momentum-dark
excitons. This provides valuable insights into the microscopic nature of excitonic phenomena in
quantum materials.
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All authors Siegfried Kaidisch, Amir Kleiner, Sivan Refaely-Abramson, Peter Puschnig, Christian S. Kern
Materials Science
Hydrothermal Synthesis of Ultra-high Aspect Ratio $\beta$-NaYF Disks via Methyliminodiacetic Acid (MIDA)
Lars Forberger, Jacob T. Baillie, Zhaojie Feng et al. (+6 more)
The hexagonal $\beta$-phase of sodium yttrium fluoride (NaYF) is a leading host material for lanthanide upconversion and anti-Stokes fluorescence
laser refrigeration based on its low
phonon energies and high upconversion efficiency. Recently experiments have been proposed to use this material as an optically-levitated sensor of high-frequency gravitational waves. In order to maximize signal-to-noise in this experiment, the NaYF sensor must have both a two-dimensional, disk-like morphology and also a large mass. Here we report a novel hydrothermal process based on the chelation ligand methylimidodiacetic acid (MIDA) to realize hexagonal $\beta$-NaYF prisms with corner-to-corner diameters up to 44 $\mathrm{\mu m}$ while keeping the height around 1 $\mathrm{\mu m}$. The surface quality is comparable to particles synthesized with EDTA based on atomic force microscopy (AFM) measurements. Unlike particles synthesized with EDTA the $\beta$-NaYF particles show no
lensing based on
curvature of the hexagonal basal plane. Single
crystal X-ray diffraction data were refined to the P-62c (#190) space group which to the best of our knowledge has not been reported in the literature. One of six 44 $\mathrm{\mu m}$ $\beta$-NaYF disks doped with 10% ytterbium showed
laser refrigeration of ($-4.9 \pm 1.0$) K suggesting future applications in both levitated optomechanics and microoptics.
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All authors Lars Forberger, Jacob T. Baillie, Zhaojie Feng, Rachel E. Gariepy, Sankhya Hirani, Daniel R. Gamelin, Shuai Zhang, Werner Kaminsky, Peter J. Pauzauskie
Materials Science
Automated laboratory x-ray diffractometer and fluorescence spectrometer for high-throughput materials characterization
Hyun Sang Park, Timothy Long, Michael Wall et al. (+8 more)
The increasing importance of artificial intelligence and machine learning in materials research has created demand for automated, high-throughput characterization techniques capable of rapidly generating large data sets. We describe here a new instrument for simultaneous X-ray diffraction and X-ray fluorescence spectroscopy, optimized for high-throughput studies of combinatorial specimens. A bright, focused, high-energy X-ray beam (24 keV) combined with a pixel array area detector allows spatially-resolved (~200 {\mu}m) transmission diffraction measurements through thick (100 {\mu}m) specimens of structural metals with exposure times as short as 1 s. Simultaneously, a silicon drift detector records X-ray fluorescence from the specimen for spatially-resolved measurement of composition. Specimen handling is fully automated, with a
robot inside the X-ray enclosure manipulating the sample for measurements at different locations. Data orchestration is also automated, with data streamed off the instrument and processed autonomously. In this paper we assess the performance of the instrument in terms of throughput, resolution, and signal-to-noise ratio, and provide an example of its capabilities through a combinatorial study of Cu-Ti
alloys to demonstrate rapid data set creation.
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All authors Hyun Sang Park, Timothy Long, Michael Wall, Alexander deJong, Ali Rachidi, Kacper Kowalik, Rohit Berlia, David Elbert, Timothy P. Weihs, Robert Drake, Todd C. Hufnagel
Materials Science · Cross-listed from cond-mat.str-el
5d-mediated indirect exchange and effective spin Hamiltonians in Ce triangular-lattice delafossites
Leonid V. Pourovskii
Anisotropic intersite exchange interactions in frustrated rare-earth magnets are difficult to assess both theoretically and experimentally. Here, we propose an ab initio force-
theorem framework combining the quasi-atomic Hubbard-I approach to 4f correlations with a static mean-field treatment of the on-site intershell Coulomb interaction between rare-earth 4f and 5d states to simultaneously capture both 4f superexchange and 5d-mediated indirect exchange. Applying it to the triangular
lattice Ce delafossites CsCeSe$_2$, KCeS$_2$, and RbCeO$_2$, we find that the indirect exchange dominates in the selenide, the superexchange in the
oxide, while both mechanisms contribute almost equally in the sulfide. The
magnetic exciation spectra of CsCeSe$_2$ and KCeS$_2$ evaluated from the calculated
spin Hamiltonains are in good qualitative and quantitative agreement with experimental data.
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Materials Science · Cross-listed from cond-mat.soft
Rheology of dense vibrated granular flows: non-monotonic response controlled by granular temperature
A. Plati, G. Petrillo, L. de Arcangelis et al. (+4 more)
We study the rheology of dense granular materials subjected to vertical vibration {by} using numerical simulations of a stress-imposed vane rheometer. The effective viscosity increases with confining pressure, decreases with vibration amplitude, and exhibits a non-monotonic dependence on frequency: weakening is observed at intermediate frequencies but is lost at high frequencies. We show that the rheological response is governed by the balance between grain-scale agitation energy and the stabilizing effect of confinement. This framework reconciles previously observed trends in viscosity and friction weakening and emphasizes the central role of energy injection and dissipation in determining granular flow properties under vibration.
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All authors A. Plati, G. Petrillo, L. de Arcangelis, A. Gnoli, A. Puglisi, A. Sarracino, E. Lippiello
Materials Science
Giant enhancement of attosecond tunnel ionization competes with disorder-driven decoherence in silicon
D. N. Purschke, D. Vick, A. Cárdenas et al. (+16 more)
High-harmonic generation (HHG) is a strong-field phenomenon that is sensitive to the attosecond dynamics of tunnel ionization and coherent transport of electron-hole pairs in solids. While the foundations of solid HHG have been established, a deep understanding into the nature of decoherence on sub-cycle timescales remains elusive. Furthermore, there is a growing need for tools to control ionization at the nanoscale. Here, we study HHG in silicon along a crystalline-to-amorphous (c-Si to a-Si) structural phase transition and observe a dramatic reshaping of the spectrum, with enhanced lower-order harmonic yield accompanied by quenching of the higher-order harmonics. Modelling the real-space
quantum dynamics links our observations to a
giant enhancement (>250 times) of tunnel ionization yield in the amorphous phase and a disorder-induced decoherence that damps the electron-hole polarization over approximately six
lattice sites. HHG spectroscopy also reveals remnant order that was not apparent with conventional probes. Finally, we observe a rapid and targeted non-resonant
laser annealing of amorphous silicon islands. Our results offer a unique insight into attosecond decoherence in strong-field phenomena, establish HHG spectroscopy as a probe of structural disorder, and pave the way for new opportunities in lightwave nanoelectronics.
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All authors D. N. Purschke, D. Vick, A. Cárdenas, N. Haram, P. Bastani, S. Gholam-Mirzaei, S. Mokhtari, V. Jelic, J. Chen, J. Canlas, J. Tordiff, Md. W. Rahman, A. Yu. Naumov, D. M. Villeneuve, A. Staudte, M. Salomons, R. E. F. Silva, Á. Jiménez-Galán, G. Vampa
Materials Science
Automated Prediction of Thermodynamic Properties via Bayesian Free-Energy Reconstruction from Molecular Dynamics
Ekaterina Spirande, Timofei Miryashkin, Andrei Kolmakov et al. (+1 more)
Accurate free-energy calculations are essential for predicting thermodynamic properties and phase stability, but existing methods are limited:
phonon-based approaches neglect anharmonicity and
liquids, while molecular dynamics (MD) is computationally demanding, neglects low-temperature
quantum effects, and often requires manual planning and post-processing of simulations. We present a unified workflow that reconstructs the Helmholtz free-energy surface from MD data using Gaussian Process Regression (GPR), augmented with zero-point energy corrections from harmonic/quasi-harmonic theory. The framework propagates statistical uncertainties, mitigates finite-size effects, and employs active learning to optimize sampling in the volume-temperature space. It applies seamlessly to both crystalline and
liquid phases. We demonstrate the methodology by computing heat capacities, thermal expansion, isothermal and adiabatic bulk
moduli, and melting properties for nine elemental FCC and BCC metals using 20 classical and machine-learned interatomic potentials, with all predictions accompanied by quantified confidence intervals. Automated, general, and uncertainty-aware, the workflow advances high-throughput thermodynamics and provides a systematic
benchmark for interatomic potentials.
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All authors Ekaterina Spirande, Timofei Miryashkin, Andrei Kolmakov, Alexander Shapeev
Materials Science · Cross-listed from physics.plasm-ph
Real-time time-dependent density functional theory for high-energy density physics
Alina Kononov, Minh Nguyen and Andrew D. Baczewski
Electronic response properties of high-energy density (HED) systems influence planetary structure, drive
evolution of fusion targets, and underpin diagnostics in laboratory astrophysics. Real-time time-dependent density functional theory (TDDFT) offers a versatile modeling framework capable of accurately predicting the dynamic response of HED materials – including free-free, bound-free, and bound-bound contributions without requiring ad hoc state partitioning; capturing both collective and non-collective behavior; and applicable within the linear-response regime and beyond. We review the theoretical formalism of real-time TDDFT as applied to HED systems, provide a practical tutorial for computing relevant response properties (dynamic structure factors, conductivity, and stopping power), and comment on avenues for further development of this powerful computational method in service of HED science.
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Materials Science · Cross-listed from cond-mat.str-el
Interlayer Coupling Driven Correlated and Charge-Ordered Electronic States in a Transition Metal Dichalcogenide Superlattice
Yiwei Li, Lixuan Xu, Shihao Zhang et al. (+11 more)
4Hb-TaS_2, a van der Waals superlattice comprising alternate stacked Ising superconducting 1H-TaS_2 and cluster Mott insulating 1T-TaS_2, exhibits emergent properties beyond those of its constituent layers. Notable phenomena include time-reversal-
symmetry-breaking superconductivity and spontaneous
vortex phases, which are driven by nontrivial interlayer interactions that remain debated. Using area-selective angle-resolved photoemission spectroscopy, we provide direct spectroscopic evidence of such interaction by systematically probing the electronic structures of 1T- and 1H-terminted surfaces of 4Hb-TaS_2. The metallic states of subsurface 1H-layers are folded to the Brillouin zone center by the sqrt(13) by sqrt(13) modulation of the surface 1T-layer, forming
chiral "windmill"
Fermi surfaces via Umklapp scattering. These conducting states further hybridize with the incipient flat band of the surface 1T-layer, producing a Kondo-like peak at the
Fermi level. Interlayer charge transfer induces distinct 3 by 3 and 2 by 2 charge orders on the surface and subsurface 1H-layers, respectively, which result in characteristic segmented
Fermi surfaces and dichotomously shift the van Hove singularities. These findings reconcile the competing Kondo and Mott-Hubbard models in this material and emphasize the interplay of flat bands, van hove singularities, charge orders, and unconventional superconductivity in correlated superlattices.
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All authors Yiwei Li, Lixuan Xu, Shihao Zhang, Lanxin Liu, Yifan Zhou, Qiang Wan, Shiwei Chen, Shiheng Liang, Yulin Chen, Yi-feng Yang, Xuan Luo, Yuping Sun, Nan Xu, Zhongkai Liu
Materials Science
Precise, efficient and flexible modeling of crystallizing elastomers based on physics-augmented neural networks
Konrad Friedrichs, Franz Dammaß, Karl A. Kalina et al. (+1 more)
We propose a precise and efficient physics-augmented neural network (PANN) to model strain-induced crystallization in rubbery
polymers. We demonstrate that the model can be flexibly employed for both unfilled and filled natural rubber (NR). The approach is based on a two potential framework, similar to the concept of generalized standard materials (GSMs). To describe the material behavior, neural network-based free energy and dissipation potentials are employed. The
evolution of crystallinity is derived from the two potentials. To ensure boundedness of the crystallinity, a novel constrained GSM-type
evolution problem is proposed. To this end, two additional Lagrange multipliers together with the corresponding Karush-Kuhn-Tucker conditions are introduced. As a result, it is guaranteed that crystallinity can be interpreted as a variable of concentration type. The neural network-based potentials ensure all physically desirable properties by construction. Most importantly, objectivity, material
symmetry and thermodynamic consistency are automatically fulfilled. In addition, an alternative derivation of the governing model equations in time-discrete form is presented based on an incremental variational framework, which also serves as the basis for a finite element implementation. We demonstrate the predictive capability of the PANN using three different experimental data sets from literature, considering both stress and crystallinity
evolution at material point level as well as the corresponding field distributions in a notched specimen. Moreover, we show that model parameterization is also possible when experimental crystallinity data is not available, still enabling suitable stress predictions.
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All authors Konrad Friedrichs, Franz Dammaß, Karl A. Kalina, Markus Kästner
Materials Science
Composition-Dependent Properties of $\mathrm{Ce_{x}La_{0.95-x}Tb_{0.05}F_{3}}$ Nanopowders Tailored for X-Ray Photodynamic Therapy and Cathodoluminescence Imaging
Xenie Lytvynenko, Marie Urbanová, Ondřej Lalinský et al. (+4 more)
This study investigates the synthesis and luminescence behavior of $\mathrm{Ce_{x}La_{0.95-x}Tb_{0.05}F_{3}}$ nanoparticles with varying $\mathrm{Ce^{3+}}$ content. The materials were prepared via a wet chemical route and thermally annealed to improve crystallinity and reduce defects. Phase composition and structural parameters were examined by X-ray diffraction (XRD), while elemental composition was determined by X-ray fluorescence (XRF). Cathodoluminescence (CL) intensity mapping was used to evaluate emission uniformity and monitor the degradation of luminescence under electron beam exposure. Photoluminescence (PL) and radioluminescence (RL) spectroscopy confirmed energy transfer from $\mathrm{Ce^{3+}}$ to $\mathrm{Tb^{3+}}$ ions. Luminescence intensities were found to depend strongly on both Ce content and thermal treatment. The results contribute to the understanding of defect-related quenching mechanisms and are relevant for the design of rare-earth-based luminescent nanomaterials for biomedical applications.
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All authors Xenie Lytvynenko, Marie Urbanová, Ondřej Lalinský, Vilém Vojta, Jan Bárta, Lenka Prouzová Procházková, Václav Čuba
Materials Science · Cross-listed from physics.optics
Reflectivity-based refractive index measurement of van der Waals materials
Xavier Zambrana-Puyalto, Alexander Johan Olsen and Søren Raza
We present a reflectivity-based method for measuring the in-plane refractive index of transparent van der Waals (vdW) materials. The approach enables the characterization of as small as $3 \times 3$~{\textmu}m$^2$ exfoliated flakes on a non-transmissive substrate without assuming any specific spectral shape of the refractive index. Exfoliated flakes are most commonly obtained through mechanical exfoliation, which generally produces vdW flakes with tens-of-micron lateral dimensions. As a result, conventional ellipsometry - which depends on large, uniform areas and specific spectral models - becomes challenging to apply. Our method determines the refractive index directly from the spectral position of reflectivity minima, provided the flake thickness and the substrate complex refractive index are known. We demonstrate the technique on hafnium disulfide (HfS$_2$), a vdW
semiconductor with high refractive index and low absorption, retrieving its in-plane refractive index across the visible range. The results both validate previous ellipsometry measurements and establish this method as an accessible and spectral-model-free alternative for refractive index characterization of vdW materials.
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Materials Science · Cross-listed from cs.LG
MiAD: Mirage Atom Diffusion for De Novo Crystal Generation
Andrey Okhotin, Maksim Nakhodnov, Nikita Kazeev et al. (+3 more)
In recent years,
diffusion-based models have demonstrated exceptional performance in searching for simultaneously stable, unique, and novel (S.U.N.) crystalline materials. However, most of these models don't have the ability to change the number of atoms in the
crystal during the generation process, which limits the variability of model sampling trajectories. In this paper, we demonstrate the severity of this restriction and introduce a simple yet powerful technique, mirage infusion, which enables
diffusion models to change the state of the atoms that make up the
crystal from existent to non-existent (mirage) and vice versa. We show that this technique improves model quality by up to x2.5 compared to the same model without this modification. The resulting model, Mirage Atom
Diffusion (MiAD), is an equivariant joint
diffusion model for de novo
crystal generation that is capable of altering the number of atoms during the generation process. MiAD achieves an 8.2% S.U.N. rate on the MP-20
dataset, which substantially exceeds existing state-of-the-art approaches. Code: https://github.com/andrey-okhotin/miad.git
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All authors Andrey Okhotin, Maksim Nakhodnov, Nikita Kazeev, Mikhail Lazarev, Andrey E Ustyuzhanin, Dmitry Vetrov
Materials Science · Cross-listed from quant-ph
Quantum Biology, Quantum Simulation and Quantum Coherent Devices
Rong-Hang Chen, Jing Dong, Wen Yang et al. (+2 more)
Many living organisms can exploit
quantum mechanical effects to gain distinct biological advantages. In plants, photosynthesis uses
quantum coherence to achieve near 100% efficiency in energy transfer. With advances in experimental techniques, two-dimensional electronic spectroscopy can reveal dynamic processes such as coherence and coupling within a system, and it plays an important role in studying energy transfer in photosynthesis. On the theory side, methods such as the generalized Bloch-Redfield theory and the hierarchical equations of motion are used to model photosynthetic systems.
Quantum simulation, as a high-efficiency and low-complexity approach, has also made progress across various platforms in the study of photosynthesis. In recent years, a series of studies has introduced
quantum coherence into artificial systems to enhance energy transfer efficiency, laying the groundwork for the design of coherent devices with efficient energy transport. Birds can use the weak geomagnetic field and
spin-dependent chemical reactions to detect direction. Theoretical frameworks for animal
navigation include magnetite-based mechanisms, magnetoreceptor genes, and the radical-pair mechanism.
Quantum simulations of
navigation have also advanced on multiple platforms. Inspired by animal
navigation, diverse
quantum effects have been applied to improve sensing and to support
navigation tasks. This paper presents a comprehensive review of progress on
quantum coherence in photosynthesis and avian
navigation, along with related theoretical methods,
quantum simulation approaches, and research on
quantum coherent devices.
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All authors Rong-Hang Chen, Jing Dong, Wen Yang, Qing Ai, Gui-Lu Long
Materials Science
Two-component anomalous Hall and Nernst effects in anisotropic Fe$_{4-x}$Ge$_x$N thin films
R.K. Paul, J. Vít, P. Levinský et al. (+18 more)
A series of thin films Fe$_{4-x}$Ge$_x$N (x=0-1) was fabricated onto MgO substrates by magnetron sputtering with the aim of studying the possible enhancement of the anomalous Nernst effect (ANE), envisaged based on Density Functional Theory (DFT) calculations. The Nernst and
Hall effects of the series were systematically analyzed, complemented with resistivity,
magnetic, electron microscopy and Mössbauer experiments, and DFT calculations including elastic properties. The Fe$_4$N phase crystallizes in the cubic
symmetry with Pm3m space group, whereas a small tetragonal distortion is realized in for x>0.35. From the comparison of the experimental isomer shift with DFT calculations, we conclude that Ge occupies the 4b site in the tetragonal I4/mcm tructure.
Ferromagnetic T$_C$ decreases rapidly from 750 K for x=0 to 100 K for x=1. The tetragonal samples with x=0.8 and 1 display two-component behavior in the
Hall and Nernst effects hysteresis loops, which can be analyzed as a sum of positive and negative loops with different saturation fields. This unusual behavior is a product of a combination of several factors. (1) Co-existence of two different crystallographic orientations in the tetragonal thin film, namely with the majority of c-axis and minority of a-axis normal to the film surface. (2) Opposite sign of the anomalous
Hall and Nernst effects for the direction of magnetization along the a and c-axis revealed by DFT calculation. (3) The magnetocrystalline anisotropy characterized by an easy ab-plane, which is responsible for the different saturation fields for a and c-axis. The maximum ANE was determined to be 0.9 $\mu$V/K for x=0 at room temperature, and -0.85 $\mu$V/K for x=1 at T=50 K. The rapid increase of ANE of Fe$_3$GeN from low temperatures indicates that, were it not for its low T$_C$, it could surpass ANE of Fe$_4$N.
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All authors R.K. Paul, J. Vít, P. Levinský, J. Hejtmánek, O. Kaman, M. Pashchenko, L. Kubíčková, K. Ahn, M. Jarošová, J. More Chevalier, S. Cichoň, T. Kmječ, J. Kohout, M. Hans, S. Mráz, J.M. Schneider, E. Adabifiroozjaei, L. Molina-Luna, O. Gutfleisch, I. Dirba, K. Knížek
Materials Science · Cross-listed from physics.optics
Record Index-Bandgap Trade-off: CdPS3 as a High-Index van der Waals Platform for Ultraviolet-Visible Nanophotonics
M. R. Povolotskiy, A. S. Slavich, G. A. Ermolaev et al. (+21 more)
The development of nanophotonics is hindered by a fundamental trade-off between a material's refractive index (n) and its electronic bandgap (Eg), which severely restricts the choice of materials for short-wavelength applications. This challenge is particularly acute in the visible and ultraviolet (UV) spectra, where high-performance devices require materials that are simultaneously highly refractive and transparent. Here, we report on the van der Waals (vdW)
crystal cadmium phosphorus trisulfide (CdPS3) as a solution to this long-standing problem. Through comprehensive optical and structural characterization, we show that CdPS3 possesses an anomalously high in-plane refractive index across the visible spectrum approaching 3 in the near-UV, combined with a wide indirect bandgap. This combination of properties, which circumvents the empirical Moss's law, is validated by first-principles calculations and direct near-field imaging of highly confined waveguide modes. These findings establish CdPS3 as a leading material for UV-visible photonics, opening a new pathway for the development of high-density integrated
circuits and metasurfaces.
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All authors M. R. Povolotskiy, A. S. Slavich, G. A. Ermolaev, D. V. Grudinin, N. V. Pak, I. A. Zavidovskiy, K. V. Kravtsov, A. A. Minnekhanov, M. K. Tatmyshevskiy, A. V. Syuy, D. I. Yakubovsky, A. Mazitov, L. A. Klimova, A. N. Toksumakov, A. V. Melentev, E. Zhukova, D. A. Ghazaryan, G. Tselikov, I. Kruglov, S. M. Novikov, A. A. Vyshnevyy, A. V. Arsenin, K. S. Novoselov, V. S. Volkov
Materials Science · Cross-listed from cond-mat.soft
Molecular dynamics simulations reveal internal tension in native state collagen fibrils
Konstantinos Steiakakis, Alan Pichard and Maxime Vassaux
Collagen fibrils are the building block of many biological tissues, which viability depend on the fibrils properties. Altered properties of collagen fibrils are central to the appearance of many diseases, while physiological or native properties must be reproduced for tissue engineering. Yet, the self-assembly, the structure, and therefore the properties of collagen fibrils remain elusive. One main reason is the extreme sensitivity of the fibrils to their environmental conditions, and in particular hydration which is only loosely bound by experimental measurements. Furthermore, mechanics are an integral part of the self-assembly process; forces exerted by
cells or osmotic pressure may result in internal stresses in collagen fibrils in native conditions. Here, we propose to investigate internal stresses in collagen fibrils by means of molecular dynamics simulations of the collagen microfibril model. Our simulations reveal the quantitative
evolution of internal stresses in collagen fibrils with hydration. We establish a value of native hydration of collagen fibrils at 0.78 g/g based on an absence of cross-sectional stresses. In turn, we determine a quantitative estimate of internal longitudinal stresses in collagen fibrils in native conditions of 210 MPa. We find that internal longitudinal stresses are caused by an over-extended
protein backbone rather than partial hydration, which appears remnant of the local forces driving collagen self-assembly. We also demonstrate the consequences of internal longitudinal stresses on the mechanical properties of collagen fibrils, which the absence of induces more than a 20% decrease in the Young's modulus. Overall, our findings provide insights into the native structure and properties of collagen fibrils. More than ever, collagen fibrils appear to be assembled via an out-of-
equilibrium process key to the synthesis of viable tissues.
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Materials Science
Heat Capacity of Thermally Reduced Graphene Oxide: Compaction and Thermal Annealing Effects
A.I. Krivchikov, A. Jezowski, M.S. Barabashko et al. (+8 more)
We present a comprehensive investigation of the low-temperature heat capacity of thermally reduced
graphene oxide (trGO) as a function of compaction pressure and annealing temperature.
Graphene oxide was synthesized using a modified Hummers method and subsequently thermally reduced at 300\,{\deg}C, 500\,{\deg}C, and 700\,{\deg}C under
vacuum to systematically vary the oxygen content and structural ordering. The specific heat data in the 2–300\,K range reveal that the thermal response is governed by
phonons, including contributions from a Schottky-type anomaly, a defect-related linear term, a Debye term, and a dispersive term with a negative coefficient associated with out-of-plane flexural (ZA)
phonons. Increasing compaction pressure alters interlayer coupling and leads to non-monotonic changes in heat capacity, while higher annealing temperatures enhance graphitization, reduce disorder, and modify
phonon dispersion. The absence of a
boson peak – similar to that observed in carbon nanotubes – supports the dominance of two-dimensional vibrational modes. These findings elucidate the relationship between dimensionality, structural disorder, and processing parameters in shaping the
phonon dynamics of trGO, providing guidance for tailoring its thermal behavior in advanced carbon-based functional materials.
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All authors A.I. Krivchikov, A. Jezowski, M.S. Barabashko, A.V. Dolbin, N.A. Vinnikov, S.V. Cherednichenko, Yu. Horbatenko, O. Korolyuk, O. Bezkrovnyi, O. Romantsova, D. Szewczyk
Materials Science
Current Switching of Topological Spin Chirality in the van der Waals Antiferromagnet Co1/3TaS2
Kai-Xuan Zhang, Seungbok Lee, Woonghee Cho et al. (+1 more)
Magnetic topology is central to modern
quantum magnet, where
spin chirality governs exotic
spin winding, real-space Berry phase, and topological
Hall effect. A key unresolved challenge is how to electrically switch topological
spin chirality and its associated gauge flux, an essential requirement for manipulating its topological
quantum properties. In this work, we propose and experimentally demonstrate the concept of current-switching
spin chirality. We identify the new vdW antiferromagnet Co1/3TaS2 as an ideal platform, hosting a topological 3Q state with a minimum chirality
cell, an ultrahigh skyrmion density, a non-centrosymmetric geometry, and a strong Berry
curvature. We discover intrinsic self-torque-induced chirality switching within Co1/3TaS2, driven purely by current, without the need of heavy metals or a
magnetic field, and with high energy efficiency. Our results establish a promising framework for electrically generating and controlling topological
spin chirality, and demonstrate a practical route toward
chiral spintronics. They can be naturally generalised to other skyrmion systems, offering new opportunities in
symmetry control, topological manipulation, and
spin-chirality-based
quantum functionalities.
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All authors Kai-Xuan Zhang, Seungbok Lee, Woonghee Cho, Je-Geun Park
Materials Science
Integrating electronic structure into generative modeling of inorganic materials
Junkil Park, Junyoung Choi and Yousung Jung
Recent advances in generative models have introduced a new paradigm for the inverse design of inorganic materials, enabling the discovery of new crystalline structures with desired properties. However, existing generative models focus solely on structural aspects of materials during generation, while overlooking the underlying electronic behavior that fundamentally governs materials' stability and functionality. In this work, we present ChargeDIFF, the first generative model for inorganic materials that explicitly incorporates electronic structure into the generation process. Specifically, ChargeDIFF leverages charge density, a direct spatial representation of a material's electronic structure, as an additional modality for generation. ChargeDIFF demonstrates exceptional performance in both unconditional and conditional generation tasks compared to baseline models, with ablation studies revealing that this improvement is directly due to its ability to capture the material's electronic structure during generation. Moreover, the ability to control charge density during generation allows ChargeDIFF to introduce a novel inverse design method based on three-dimensional charge density, illustrating the potential to generate lithium-ion battery cathode materials with desired ion migration pathways, as validated by physics-based simulations. By highlighting the importance of accounting for electronic characteristics during material generation, ChargeDIFF offers new possibilities in the generative design of stable and functional materials.
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Materials Science
Twin-boundary-induced nonrelativistic spin splitting
Kristoffer Eggestad, Marc Vila, Sverre M. Selbach et al. (+1 more)
Nonrelativistic
spin splitting (NRSS) in compensated
magnetic materials is drawing considerable
attention due to its potential impact in next-generation spintronic devices. While NRSS is typically restricted to materials with particular
symmetry constraints, here we demonstrate, using density functional theory (DFT) and tight-binding transport calculations, that twin boundaries can induce NRSS in
magnetic systems where it is otherwise forbidden. We focus on two representative material systems: the tetragonal perovskite
oxide BiCoO$_3$ with $90^{\circ}$ ferroelastic domain walls, and the rhombohedral layered delafossite-type
oxide CoO$_2$, supporting $71^{\circ}$, $109^{\circ}$, and $135^{\circ}$ twin boundaries. Our results reveal that, if these boundaries coexist with
ferromagnetic domain walls, they consistently produce NRSS similar to that of d-wave altermagnets, with nodal surfaces dictated by the underlying
symmetry of the supercell containing the twin boundary. Tight-binding models further elucidate how the NRSS and derived transport properties scale with domain size and density. Our results put forward twin boundary engineering as a versatile route to realize and control
spin splitting in a broader class of materials.
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All authors Kristoffer Eggestad, Marc Vila, Sverre M. Selbach, Sinéad M. Griffin