Materials Science
Extraction of a structural short-range order descriptor from nanobeam electron diffraction patterns using a transfer learning approach
Junjie Wu and Timothy J. Rupert
Amorphous solids exhibit structural short-range order despite lacking long-range crystalline order, with this structural descriptor found to be important for determining mechanical properties. Nanobeam electron diffraction offers a potential route for experimental characterization of structural short-range order, yet efforts to date have been primarily qualitative in nature. In this work, machine learning approaches based on transfer learning are used to enable quantitative analysis of nanobeam electron diffraction data from amorphous solids. A ResNet-18 model is trained on simulated diffraction patterns taken from different locations within simulated metallic glasses and amorphous grain boundary complexions in the Cu-Zr
alloy system that were created with hybrid molecular dynamics and Monte Carlo simulations. The disorder parameter is found to be a superior target structural descriptor compared to traditional Voronoi indices for this task. The model achieves a low validation mean absolute error across diffraction patterns corresponding to different interaction volumes, demonstrating excellent performance and potential transferability. Testing was performed using other simulated nanobeam electron diffraction data as well as experimental nanobeam electron diffraction patterns, showing that the model can reliably capture spatial variations in local structural state. As a whole, this framework is able to overcome the challenges in the quantitative experimental characterization of structural short-range order, enabling improved characterization of amorphous solids and the exploration of structure-property relationships.
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Materials Science
Accelerated Inorganic Electrides Discovery by Generative Models and Hierarchical Screening
Shuo Tao and Qiang Zhu
Electrides are exotic compounds in which excess electrons occupy interstitial regions of the
crystal lattice and serve as anions, exhibiting exceptional properties such as low work function, high electron mobility, and strong catalytic activity. Although they show promise for diverse applications, identifying new electrides remains challenging due to the difficulty of achieving energetically favorable electron localization in
crystal cavities. Here, we present an accelerated materials discovery framework that combines physical principles,
diffusion-based materials generation with hierarchical thermodynamic and electronic structure screening. Using this workflow, we systematically explored 1,510 binary and 6,654 ternary chemical compositions containing excess valence electrons from electropositive alkaline, alkaline-earth, and early transition metals, and then filtered them with a high throughput validation on both thermodynamical stability and electronic structure analysis. As a result, we have identified 264 new electron rich compounds within 0.05 eV/atom above the convex hull at the density functional theory (DFT) level, including 13 thermodynamically stable electrides. Our approach demonstrates a generalizable strategy for targeted materials discovery in a vast chemical space.
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Materials Science · Cross-listed from physics.chem-ph
Better without U: Impact of Selective Hubbard U Correction on Foundational MLIPs
Thomas Warford, Fabian L. Thiemann and Gábor Csányi
The training of foundational machine learning interatomic potentials (fMLIPs) relies on diverse databases with energies and forces calculated using ab initio methods. We show that fMLIPs trained on large
datasets such as MPtrj, Alexandria, and OMat24 encode inconsistencies from the Materials Project's selective use of the Hubbard U correction, which is applied to certain transition metals only if O or F atoms are present in the simulation
cell. This inconsistent use of +U creates two incompatible potential-energy surfaces (PES): a lower-energy GGA surface and a higher-energy GGA+U one. When trained on both, MLIPs interpolate between them, leading to systematic underbinding, or even spurious repulsion, between U-corrected metals and oxygen- or fluorine-containing species. Models such as MACE-OMAT and -MPA exhibit repulsion between U-corrected metals and their
oxides, limiting their value for studying catalysis and oxidation. We link the severity of this pathology to the oxygen number density in U-corrected training configurations. This explains why OMAT-trained models are most affected and suggests the issue might worsen as expanding future
datasets increasingly include configurations with low oxygen content, such as those generated through combinatorial exploration of multi-element or defect-containing systems. Our simple per-U-corrected-atom shift aligns PBE+U and PBE energies for identical structures, yielding a smoother PES compared to existing correction schemes, which target phase diagram accuracy. As a result, models trained on
datasets with our shift applied exhibit smaller mean absolute errors for the adsorption energies of oxygen on U-corrected elemental slabs. Since
datasets omitting +U entirely (e.g. MatPES, MP-ALOE) avoid these pathologies, we recommend excluding +U in future fMLIP
datasets. For existing
datasets, our post-hoc correction provides a low-cost improvement.
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Materials Science
Field-Induced Ferroelectric Phase Transition Dynamics in PMN-PT compositions near the Morphotropic Phase Boundary
Shivjeet Chanan, Joseph Kerchenfaut, Eduard Illin et al. (+1 more)
The dynamical behavior of field-induced ferroelectric phase transitions in compositions of PbMg1/3Nb2/3O3(1-x)-PbTiO3(x) (PMN-PT) near the morphotropic phase boundary (MPB) was investigated using several electric-field application protocols. Our results show that PMN-PT compositions near the MPB exhibit phase-transition dynamics that differ markedly from those far below the MPB. We demonstrate that electric-field history significantly affects the field-induced transition temperature Tc, zero-field-cooling (ZFC) delay time tau_ZFC, and induced polarization Pc gained or lost during the transition. Furthermore, under specific field-temperature conditions, PMN-PT retains a
memory of its electric-field history and uses it to kinetically accelerate ferroelectric ordering. We propose an explanation for the differences in phase-transition dynamics between MPB-proximal and MPB-distant compositions, contextualized within prior literature.
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All authors Shivjeet Chanan, Joseph Kerchenfaut, Eduard Illin, Eugene V. Colla
Materials Science · Cross-listed from cond-mat.supr-con
Benjamin Geisler, Philip M. Dee, James J. Hamlin et al. (+3 more)
Superconducting materials are of significant technological relevance for a broad range of applications, and intense research efforts aim at enhancing the critical temperature $T_{c}$. Intriguingly, while numerous studies have explored different computational and machine-learning routes to predict $T_{c}$, the fundamental role of the critical
magnetic field has so far been overlooked. Here we open a new frontier in
superconductor discovery by presenting a consistent computational database of critical fields $H_{c}$, $H_{c1}$, and $H_{c2}$ for over 7300 electron-
phonon-paired
superconductors covering distinct materials classes. A theoretical framework is developed that combines $\alpha^2F(\omega)$ spectral functions and highly accurate
Fermi surfaces from density functional theory with clean-limit Eliashberg theory to obtain the coherence lengths, London penetration depths, and Ginzburg-Landau parameters. We discover an unexpectedly large number of Type-I
superconductors and show that larger unit
cells generically support higher critical fields and Type-II behavior. We identify the importance of going beyond BCS theory by including strong-coupling corrections to the superconducting gap and electron-
phonon renormalizations of the effective mass for predictions of critical fields across materials. These results provide a framework for foundational AI models that realize the concept of inverse materials design for high-$T_{c}$ and high-critical-field
superconductors.
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All authors Benjamin Geisler, Philip M. Dee, James J. Hamlin, Gregory R. Stewart, Richard G. Hennig, P.J. Hirschfeld
Materials Science · Cross-listed from physics.chem-ph
StochasticGW-GPU: rapid quasi-particle energies for molecules beyond 10000 atoms
Phillip S. Thomas, Minh Nguyen, Dimitri Bazile et al. (+6 more)
$\mathtt{StochasticGW}$ is a code for computing accurate Quasi-Particle (QP) energies of molecules and material systems in the GW approximation. $\mathtt{StochasticGW}$ utilizes the
stochastic Resolution of the Identity (sROI) technique to enable a massively-parallel implementation with computational costs that scale semi-linearly with system size, allowing the method to access systems with tens of thousands of electrons. We introduce a new implementation, $\mathtt{StochasticGW-GPU}$, for which the main bottleneck steps have been ported to GPUs and which gives substantial performance improvements over previous versions of the code. We showcase the new code by computing band gaps of hydrogenated silicon clusters ($\textrm{S}\textrm{i}_{\textrm{x}}\textrm{H}_{\textrm{y}}$) containing up to 10001 atoms and 35144 electrons, and we obtain individual QP energies with a statistical precision of better than $\pm0.03$ eV with times-to-solution on the order of minutes.
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All authors Phillip S. Thomas, Minh Nguyen, Dimitri Bazile, Tucker Allen, Barry Y. Li, Wenfei Li, Mauro Del Ben, Jack Deslippe, Daniel Neuhauser
Materials Science · Cross-listed from cs.LG
MADE: Benchmark Environments for Closed-Loop Materials Discovery
Shreshth A Malik, Tiarnan Doherty, Panagiotis Tigas et al. (+4 more)
Existing
benchmarks for computational materials discovery primarily evaluate static predictive tasks or isolated computational sub-tasks. While valuable, these evaluations neglect the inherently iterative and adaptive nature of scientific discovery. We introduce MAterials Discovery Environments (MADE), a novel framework for benchmarking end-to-end autonomous materials discovery pipelines. MADE simulates closed-loop discovery campaigns in which an
agent or
algorithm proposes, evaluates, and refines candidate materials under a constrained oracle budget, capturing the sequential and resource-limited nature of real discovery workflows. We formalize discovery as a search for thermodynamically stable compounds relative to a given convex hull, and evaluate efficacy and efficiency via comparison to baseline
algorithms. The framework is flexible; users can compose discovery
agents from interchangeable components such as generative models, filters, and planners, enabling the study of arbitrary workflows ranging from fixed pipelines to fully agentic systems with tool use and adaptive decision making. We demonstrate this by conducting systematic experiments across a family of systems, enabling ablation of components in discovery pipelines, and comparison of how methods scale with system complexity.
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All authors Shreshth A Malik, Tiarnan Doherty, Panagiotis Tigas, Muhammed Razzak, Stephen J. Roberts, Aron Walsh, Yarin Gal
Materials Science · Cross-listed from cs.LG
A generative machine learning model for designing metal hydrides applied to hydrogen storage
Xiyuan Liu, Christian Hacker, Shengnian Wang et al. (+1 more)
Developing new metal hydrides is a critical step toward efficient hydrogen storage in carbon-neutral energy systems. However, existing materials databases, such as the Materials Project, contain a limited number of well-characterized hydrides, which constrains the discovery of optimal candidates. This work presents a framework that integrates causal discovery with a lightweight generative machine learning model to generate novel metal hydride candidates that may not exist in current databases. Using a
dataset of 450 samples (270 training, 90 validation, and 90 testing), the model generates 1,000 candidates. After ranking and filtering, six previously unreported chemical formulas and
crystal structures are identified, four of which are validated by density functional theory simulations and show strong potential for future experimental investigation. Overall, the proposed framework provides a scalable and time-efficient approach for expanding hydrogen storage
datasets and accelerating materials discovery.
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All authors Xiyuan Liu, Christian Hacker, Shengnian Wang, Yuhua Duan
Materials Science · Cross-listed from cond-mat.supr-con
Field induced superconductivity in a magnetically doped two-dimensional crystal
Adrian Llanos, Veronica Show, Reiley Dorrian et al. (+1 more)
Magnetic field induced superconductivity is a rare property in nature due to the sensitivity of
spin-singlet Cooper pairing to time-reversal
symmetry breaking perturbations. However, in rare cases, an interplay between
magnetic fields and ions can be engineered to bring about superconductivity at finite fields. Here we use ultra-thin LaSb$_2$ doped with dilute Ce paramagnetic
impurities to demonstrate a
magnetic field-induced superconducting dome in a two-dimensional
crystal. The reduced dimensionality of the structure enables the use of an in-plane
magnetic field to dynamically suppress
spin fluctuations on the Ce-site, which leads to an anomalous enhancement of the critical temperature with increasing field. By modelling the
spin scattering dynamics across the experimental parameter space, we reveal insight into the complex nature of paramagnetic
impurities in
magnetic fields at low temperature, and how their manipulation can result in the ability to tune between competing
magnetic pair-breaking regimes. Realizing this physics in a two-dimensional crystalline setting invites the application of similar approaches to unconventional forms of superconductivity while also highlighting new experimental standards which should be employed when studying ultra-thin materials in general.
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All authors Adrian Llanos, Veronica Show, Reiley Dorrian, Joseph Falson
Materials Science · Cross-listed from cond-mat.str-el
Stripe antiferromagnetism and chiral superconductivity in tWSe$_2$
Erekle Jmukhadze, Sam Olin, Allan H. MacDonald et al. (+1 more)
The layer-dependent
Hamiltonians of parallel-stacked MoTe$_2$ and WSe$_2$ homobilayer moiré materials are topologically non-trivial, both in real space and in momentum space, and have been shown to support integer and fractional
quantum anomalous
Hall states, as well as
antiferromagnetic and superconducting states. Here, we address the interplay between the
antiferromagnetic and superconducting states observed in tWSe$_2$ when the
Fermi level is close to its $M$-point van Hove singularity and the displacement field is small. We combine DFT with path-integrals to construct a minimal moiré band model that accounts for
lattice relaxation along the $c$-axis and perform Hartree-Fock calculations to identify competing charge and
spin ordered states. For tWSe$_2$ at $\theta=2.7^\circ$ and $\theta=3.65^\circ$, we find that a layer antiferromagnet (AFM), a stripe
spin-density-wave (SDW), and the
ferromagnetic Chern
insulator (FM) are the primary candidates for the ground state at zero displacement field, and argue that
antiferromagnetic spin interactions on the next neighbor bond $J_2$ can induce a time-reversal
symmetry breaking
chiral superconducting state.
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All authors Erekle Jmukhadze, Sam Olin, Allan H. MacDonald, Wei-Cheng Lee
Materials Science
Millisecond spin coherence of electrons in semiconducting perovskites revealed by spin mode locking
Sergey R. Meliakov, Evgeny A. Zhukov, Vasilii V. Belykh et al. (+4 more)
Long
spin coherence times of carriers are essential for implementing
quantum technologies using
semiconductor devices for which, however, a possible obstacle is
spin relaxation. For the
spin dynamics, decisive features are the band structure,
crystal symmetry, and
quantum confinement. Perovskite
semiconductors recently have come into focus of studies of their
spin states, notivated by efficient optical access and potentially long-living coherence. Here, we report an electron
spin coherence time $T_2$ of the order of 1 ms, measured for a bulk FA$_{0.95}$Cs$_{0.05}$PbI$_3$ lead halide perovskite
crystal. Using periodic
laser pulses, we synchronize the electron
spin Larmor precession about an external
magnetic field in an inhomogeneous ensemble, the effect known as
spin mode locking. It appears as a decay of the optically created ensemble
spin polarization within the dephasing time $T_2^*$ of up to 20 ns and its revival during the
spin coherence time $T_2$ reaching the millisecond range. This exceptionally long
spin coherence time in a bulk
crystal is complemented by millisecond-long longitudinal
spin relaxation times $T_1$ for electrons and holes, measured by optically-detected
magnetic resonance. These long-lasting
spin dynamics highlight perovskites as promising platform for the
quantum devices with all-optical control.
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All authors Sergey R. Meliakov, Evgeny A. Zhukov, Vasilii V. Belykh, Dmitri R. Yakovlev, Bekir Turedi, Maksym V. Kovalenko, Manfred Bayer
Materials Science
Multiscale Numerical Modelling of Ultrafast Laser-Matter Interactions: Maxwell Two Temperature Model Molecular Dynamics (M-TTM-MD)
Othmane Benhayoun and Martin E. Garcia
In this work, we present a comprehensive numerical framework that couples numerical solutions of Maxwell's equations using the Finite-Difference Time-Domain (FDTD) approach, Molecular Dynamics (MD), and the Two-Temperature Model (TTM) to describe ultrafast
laser-matter interactions in metallic systems at the atomic scale. The proposed Maxwell-Two-Temperature Model-Molecular Dynamics (M-TTM-MD) bridges the gap between electromagnetic field propagation, electron-
phonon energy exchange, and atomic motion, allowing for a self-consistent treatment of energy absorption, transport, and structural response within a unified simulation environment. The calculated electromagnetic fields incorporate dispersive dielectric properties derived using the Auxiliary Differential Equation (ADE) technique, while the electronic and
lattice subsystems are dynamically coupled through spatially and temporally resolved energy exchange terms. The changes in the material topography are then reflected in the updated grid for the FDTD scheme. The developed M-TTM-MD model provides a self-consistent numerical framework that offers insights into
laser-induced phenomena in metals, including energy transport and surface dynamics under extreme nonequilibrium conditions.
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Materials Science
Morphological Stability of Metal Anodes: Roles of Solid Electrolyte Interphases (SEIs) and Desolvation Kinetics
Jin Zhang and Peter W. Voorhees
Achieving stable lithium metal anodes requires control over the solid-electrolyte interphase (SEI) and desolvation kinetics. Here, we develop a unified theoretical framework integrating ion transport, desolvation, charge transfer, and SEI breakdown to predict morphological instabilities during electrodeposition. Using linear stability analysis, we identify six dimensionless parameters that govern the onset and
evolution of instabilities. We show that SEI transport and desolvation rate effectively modulate apparent reaction kinetics, shifting the system toward a stable, reaction-limited regime. Extending the classical limiting current concept, we demonstrate that a thick, poorly conductive SEI and sluggish desolvation significantly reduce the limiting current. We introduce an apparent Damköhler number to quantify the critical balance: suppressing
diffusion-limited instabilities by reaction rate reduction, while maintaining a high limiting current. Our theory enables predictive mapping of electrodeposition morphologies across diverse materials and operating conditions, guiding the rational design of stable lithium metal anodes.
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Materials Science
Universality of Type-II Multiferroicity in Monolayer Nickel Dihalides
Aleš Cahlík, Antti Karjasilta, Anshika Mishra et al. (+5 more)
The recent discovery of type-II multiferroicity in monolayer NiI${_2}$ indicated a new pathway for intrinsic magnetoelectric coupling in the two-dimensional limit. However, determining whether this phenomenon is a unique anomaly or a general, chemically tunable property of the material class remains unresolved. Here, we demonstrate the universality of type-II multiferroicity in the transition metal dihalides by visualizing the ferroelectric order in monolayer NiBr${_2}$. Using scanning tunneling microscopy (STM), we resolve atomic-scale ferroelectric domains and confirm their magnetoelectric origin through reciprocal manipulation experiments: reorienting
magnetic order via electric fields and suppressing the electric polarization with external
magnetic fields. Furthermore, we find that the multiferroic state in NiBr${_2}$ is energetically less robust than in its iodide counterpart, consistent with modified superexchange interactions and the reduced
spin-orbit coupling. Our results establish the transition metal dihalides as a versatile platform where the stability of magnetoelectric phases can be engineered through chemical substitution.
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All authors Aleš Cahlík, Antti Karjasilta, Anshika Mishra, Robert Drost, Mohammad Amini, Javaria Arshad, Büşra Arslan, Peter Liljeroth
Materials Science
Manipulating ferroelectricity without electrical bias: A perspective
Bixin Yan, Valentine Gillioz, Ipek Efe et al. (+1 more)
Ferroelectric materials are established candidates for beyond complementary metal-
oxide-
semiconductor technology, owing to their non-volatile spontaneous electrical polarization. The recent boom in electric dipole texture engineering and manipulation in such materials has revealed exciting routes for controlling ferroelectric polarization, offering alternatives to the classical, sometimes challenging, application of electrical fields. In this short perspective, we shed light on electrode-free external stimuli enabling control over polar states in thin films. We bring awareness to the polarizing role of chemically-engineered surface contributions and provide insights into the combination of chemical substitution and mechanical pressure, complementing the polar state tuning capabilities readily enabled by flexoelectricity. Finally, we describe recent developments in the optical modulation of polarization. Thus, our perspective aims to stimulate the advancement of alternative means to act on polarization states and facilitate the development of ferroelectric-based applications.
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All authors Bixin Yan, Valentine Gillioz, Ipek Efe, Morgan Trassin
Materials Science
Impact of O concentration on the thermal stability and decomposition mechanism of (Cr,Al)N compared to (Ti,Al)N thin films
Pauline Kümmerl, Ganesh Kumar Nayak, Felix Leinenbach et al. (+6 more)
The composition-dependent thermal stability of (Cr$_{0.47 \mp 0.03}$Al$_{0.53 \mp 0.03}$)$_{z}$(O$_{y}$N$_{1-y}$)$_{1-z}$ thin films with O concentrations of y = 0, 0.15, and 0.40 is investigated up to 1200 {\deg}C and then compared to (Ti$_{0.56}$Al$_{0.44}$)$_{z}$(O$_{y}$N$_{1-y}$)$_{1-z}$. X-ray diffraction reveals a thermal stability limit of 1150 {\deg}C independent of the O concentration, as witnessed by the formation of decomposition products, namely h-Cr$_{2}$N for (Cr$_{0.50}$Al$_{0.50}$)$_{0.49}$N$_{0.51}$ and c-Cr for both (Cr$_{0.48}$Al$_{0.52}$)$_{0.48}$(O$_{0.15}$N$_{0.85}$)$_{0.52}$ and (Cr$_{0.44}$Al$_{0.56}$)$_{0.46}$(O$_{0.40}$N$_{0.60}$)$_{0.54}$. Based on TEM and ERDA data, the thermal stability limit is extended to 1100 - 1150 {\deg}C. DFT calculations indicate that bond breaking limits the thermal stability. In (Cr,Al)N, N has the lowest activation energy for migration. Furthermore, the O vacancy formation energy is highest in (Cr,Al)(O,N). It has to be overcome to enable
diffusion on the non-metal sublattice, which is necessary for forming decomposition products like w-AlN or c-Cr. However, once Cr-N bonds break, decomposition into h-Cr$_{2}$N and subsequent c-Cr together with N$_{2}$ is triggered. This results in N evaporation, generating sufficient non-metal vacancies that greatly enhance
diffusion and render the extensive vacancy formation energies for non-metals irrelevant. This reduction of the activation energy for mass transport on the non-metal sublattice to the migration barrier causes the similar thermal stability in (Cr$_{0.47 \mp 0.03}$Al$_{0.53 \mp 0.03}$)$_{z}$(O$_{y}$N$_{1-y}$)$_{1-z}$. In contrast, Al bonds break first without creating non-metal vacancies in (Ti,Al)(O,N). Thus, the high O vacancy formation energy in (Ti,Al)(O,N) significantly increases the thermal stability compared to (Ti,Al)N as well as the here investigated films.
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All authors Pauline Kümmerl, Ganesh Kumar Nayak, Felix Leinenbach, Zsolt Czigány, Daniel Primetzhofer, Szilárd Kolozsvári, Peter Polcik, Marcus Hans, Jochen M. Schneider
Materials Science
Switchable Topological Polar Textures in Freestanding Ultrathin Ferroelectric Oxides
Franco N. Di Rino and Tim Verhagen
The remarkable advances achieved in two-dimensional materials are now being directly transposed to low-dimensional
oxides. Here we show using first-principles-based atomistic simulations that ultrathin freestanding ferroelectric layers host a rich variety of polar states, from
liquid-like ferroelectric domains with long-range orientational order to helix-wave and
chiral bubbles configurations reminiscent of those observed in twisted freestanding
oxide layers. Time-dependent electric fields enable reversible control, revealing freestanding
oxide layers as ideal platforms to explore complex polar states and their potential applications in future ferroic devices.
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Materials Science
Silicon Driven Facet Regulation Enables Tunable Micro-Diamond Architectures in Liquid Ga In
Zhi Jiang, Xueying Zhang, António José Silva Fernandes et al. (+2 more)
We report an ambient pressure
liquid metal assisted CVD strategy that enables shape programmable growth of micro scale diamond by coupling
liquid metl Ga In with ferrocene (Fe(C5H5)2) as an carbon precursor, nanodiamond seeds, and nanosilicon. Building on
liquid metal diamond synthesis, this approach pushes
liquid metal growth toward a low temperature (900 {\deg}C, 1 atm) while enabling single
crystal diamonds to be scaled from ~10 {\mu}m to several tens of micrometers with well developed faceting. Ferrocene decomposition supplies a sustained interfacial carbon flux that is captured and redistributed by the Ga In melt toward seed rich
liquid solid interfaces. Defect rich nanodiamond provides the crystallographic template required for reliable sp3 nucleation despite the intrinsically low carbon solubility of Ga In. Nanosilicon plays a distinct, complementary role by tuning interfacial kinetics and facet competition, enabling deliberate control of
crystal habit: cubic (~10 {\mu}m), truncated tetrahedral, and fully faceted octahedral diamonds are reproducibly obtained by adjusting the nanosilicon:nanodiamond ratio, with octahedral
crystals reaching ~50 {\mu}m. Importantly,
crystal size is further scaled by regulating hydrogen flow: lowering the H2 rate increases net carbon retention at the
liquid metal interface, raises effective supersaturation, and accelerates diamond deposition. Together, habit control (via nanosilicon: nanodiamond) and size scaling (via H2 flow) establish a practical route silicon driven facet regulation and size under ambient pressure, offering a pathway to tunable micro sized single
crystal diamonds under mild conditions.
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All authors Zhi Jiang, Xueying Zhang, António José Silva Fernandes, Marco Peres, Gil Gonçalves
Materials Science
Epitaxial Ni/Cu Superlattice Nanowires with Atomically Sharp Interfaces for Spin Transport
Janez Zavašnik, Sama Derakshan-Nejad, Maryam Ghaffari et al. (+6 more)
The importance of microstructure increases when decreasing the size of an object to the nanoscale, along with the complexity of controlling it. For instance, it is particularly complicated to create nano-object with controlled interfaces. Therefore, progressing towards 1D epitaxial nanostructures poses a challenge, and realization of their full potential is linked to technological issues of achieving large-scale, precise atom stacking of two or more different chemical elements. Achieving such coherent, epitaxial interfaces is a key step toward enabling spintronic phenomena in 1D objects, by minimizing interface scattering and strain-driven defects. Our results demonstrate a successful realization of controlled nanoscale heteroepitaxy in one-dimensional single-
crystal structures. We fabricated nanowires composed of alternating
magnetic (nickel) and non-
magnetic, highly conductive (copper) segments. This periodic stacking modulates electron transport under
magnetic stimuli. The epitaxial precision achieved eliminates detrimental electron scattering that has historically limited the magnetotransport properties of such 1D structures and hindered their development. Such materials are crucial for further advancements in the miniaturisation of nanosensors, actuators, and next-generation 3D spintronic devices.
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All authors Janez Zavašnik, Sama Derakshan-Nejad, Maryam Ghaffari, Amir Hassan Montazer, Mohammad Reza Mardaneh, Mohammad Almasi Kashi, Alexandre Nomine, Stephane Mangin, Uroš Cvelbar
Materials Science · Cross-listed from cond-mat.supr-con
Microscopic structure of the vortex cores in granular niobium: A coherent quantum puzzle
V. S. Stolyarov, V. Neverov, A. V. Krasavin et al. (+12 more)
When macroscopic
quantum condensates –
superconductors, superfluids, cold atoms and ions, polaritons etc. – are put in rotation, a
quantum vortex lattice forms inside. In homogeneous type-II
superconductors, each
vortex has a tiny core where the superconducting gap $\Delta(r)$ is known to smoothly vanish towards the core centre on the scale of the coherence length $\xi$. The cores host quantized quasiparticle energy levels known as Caroli-de Gennes-Matricon (CdGM) bound states [Caroli et al., Phys. Lett. v. 9, 307 (1964)]. In pure materials, the spectrum of the low-lying CdGM states has the characteristic level spacing $\sim \Delta_0^2/E_F$, where $E_F$ is the
Fermi energy and $\Delta_0$ is the bulk gap. In disordered ones, the CdGM states shift and broaden due to scattering. Here, we show, both experimentally and theoretically, that the situation is completely different in granular Nb films, which are commonly used in superconducting electronics. In these films, in which the grains are smaller than $\xi$, the gap $\Delta$ in the quasiparticle spectrum reduces towards the
vortex core centres by discrete jumps at the grain boundaries. The bound states adapt to the local environment and appear at unexpectedly high energies. Both $\Delta(r)$ and bound states form a puzzle-like spatial structure of the core, elements of which are whole grains. Our discovery shakes up the established understanding of the
quantum vortex and encourages a reconsideration of the
vortex motion and pinning mechanisms in granular
superconductors.
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All authors V. S. Stolyarov, V. Neverov, A. V. Krasavin, D. I. Kasatonov, D. Panov, D. Baranov, O. V. Skryabina, A. S. Melnikov, A. A. Golubov, M. Yu. Kupriyanov, A. A Shanenko, T. Cren, A. Yu. Aladyshkin, A. Vagov, D. Roditchev
Materials Science
Topological-transition-driven Giant Enhancement of Second-harmonic Generation in Ferroelectric Bismuth Monolayer
Wen-Zheng Chen, Hongjun Xiang and Yusheng Hou
The interplay between band
topology and light in condensed materials could unlock intriguing nonlinear optical phenomena, enabling modern photonic technologies such as
quantum light sources and sub-wavelength topological
lasers. Here, we unveil that a buckling-tuned topological transition in ferroelectric bismuth monolayer unleashes a
giant second-harmonic generation. Using first-principles calculations, we surprisingly find that ferroelectric bismuth monolayer with a buckling parameter, $\Delta h$, has a large susceptibility $\chi^{(2)}$ on the order of $10^{7}$ $\mathrm{pm}^2/\mathrm{V}$, exceeding monolayer MoS$_2$ by about two orders of magnitude. When $\Delta h$ is engineered to the critical window where Dirac electrons emerge, a low-frequency resonance appears, boosting $\chi^{(2)}$ by an additional order of magnitude. We show that this enhancement is localized on the Dirac cones and dominated by intraband modification contributions. Based on an extended Dirac model, we establish that this enhancement physically originates from the ultralight effective masses $m^{*}$ of Dirac electrons through scaling with the
Fermi velocity $v_F$ and band gap $E_g$. Our findings provide a general paradigm for achieving exceptional second-harmonic generation via engineering topological criticality, and could serve as an experimental signature of Dirac electrons in topological materials.
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Materials Science
Contrasting impurity-induced magnetism and dynamics in 2H-MoTe2
Jonas A. Krieger, Igor P. Rusinov, Sourabh Barua et al. (+13 more)
We investigate the behavior of interstitial $^8$Li$^+$ implanted near the surface of 2H-MoTe$_2$ using $\beta$-detected NMR. We find that, unlike the
muon, $^8$Li$^+$ does not show any signature of induced magnetism. This result is consistent with density functional theory, which identifies the Li stopping site at the 2a Wyckoff position in the van der Waals gap and confirms the absence of detectable Li-induced electronic
spin polarization. Both the
spin-
lattice relaxation and the resonance lines show evidence of strong
spin dynamics above $\sim 200$ K, reminiscent of local
stochastic $^8$Li$^+$ motion within a cage. The resonance line shape consists of quadrupolar satellites on top of a broad central peak. To better understand the interaction of $^8$Li$^+$ with the host material, we employ a frequency-comb measurement, by simultaneously exciting four frequencies corresponding to the first-order quadrupolar satellite transitions, $\nu_0 \pm 3\nu_{\mathrm{comb}}$ and $\nu_0 \pm\nu_{\mathrm{comb}}$ around the Larmor frequency $\nu_0$ as a function of $\nu_{\mathrm{comb}}$. This offers an enhanced sensitivity to the quadrupolar split portion of the line. Using this method, we find a small decrease of the quadrupolar frequency with increasing temperature, showing the typical behavior associated with thermally excited
phonons and the absence of any
magnetic response which was observed with other defects in 2H-MoTe$_2$.
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All authors Jonas A. Krieger, Igor P. Rusinov, Sourabh Barua, Aris Chatzichristos, Jared Croese, Derek Fujimoto, Stefan Holenstein, Victoria L. Karner, Ryan M. L. McFadden, John O. Ticknor, W. Andrew MacFarlane, Robert F. Kiefl, Geetha Balakrishnan, Evgueni V. Chulkov, Stuart S. P. Parkin, Zaher Salman
Materials Science · Cross-listed from physics.chem-ph
SITH: A Quantum-Chemical Framework for Predicting Bond Destabilization in Stretched Molecules
Daniel Sucerquia, Mikaela Farrugia, Andreas Dreuw et al. (+1 more)
Mechanical forces can selectively destabilize chemical bonds of molecular systems, particularly in biological and synthetic
polymers. While experimental and theoretical methods have advanced our understanding of mechanochemical processes, predicting where energy concentrates within a molecule remains a significant challenge. To address this, we introduce SITH (Splitting Intramolecular Tension due to stretcHing), a novel method that decomposes the total electronic energy change of a stretched molecule into contributions from individual degrees of freedom – such as bond lengths, angles, and dihedrals – using numerical integration of the work-energy
theorem. Unlike previous approaches that rely on harmonic approximations, SITH provides high accuracy and robustness to study the distribution of energies of stretched molecules up to a first bond cleavage. Although SITH uses 3N-6 degrees of freedom for the energy decomposition, we show that it can work even for ring structures like prolines. We apply SITH to a
dataset of tripeptides and demonstrate that glycine and proline exhibit significantly different energy distributions in their Ca-C backbone bonds under tension: glycine stores more energy, making it more prone to rupture, while proline has the opposite behaviour. These findings reveal intrinsic differences in mechanochemical susceptibility across amino acids, offering more accurate predictions of bond rupture in
proteins, and similarly in other (bio)
polymers. SITH thus provides a powerful, interpretable tool for understanding energy distribution at the
quantum level, with possible implications in mechanochemistry and force field validation.
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All authors Daniel Sucerquia, Mikaela Farrugia, Andreas Dreuw, Frauke Gräter
Materials Science
Tuning field amplitude to minimise heat-loss variability in magnetic hyperthermia
Necda Çam, Iago López-Vázquez, Òscar Iglesias et al. (+1 more)
In this work, we theoretically investigate how shape-induced anisotropy dispersion and
magnetic field amplitude jointly control both the magnitude and heterogeneity of heating in magnetite nanoparticle assemblies under AC
magnetic fields. Using real time Landau-Lifshitz-Gilbert simulations with thermal fluctuations, and a macrospin model that includes both the intrinsic cubic magnetocrystalline anisotropy and a shape-induced uniaxial contribution, we analyze shape-polydisperse systems under clinically and technologically relevant field conditions. We show that for relatively large particles, around 25 to 30 nm, the relative dispersion of local (single-particle) losses exhibits a well-defined minimum at moderate field amplitudes (between 4 to 12 mT), hence identifying an optimal operating regime that minimizes heating heterogeneity while maintaining substantial power dissipation. The position of this critical field depends mainly on particle size and excitation frequency, and only weakly on shape dispersion, offering practical guidelines for improving heating uniformity in realistic MFH systems.
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All authors Necda Çam, Iago López-Vázquez, Òscar Iglesias, David Serantes
Materials Science
ALD-Derived WO3-x Leads to Nearly Wake-Up-Free Ferroelectric Hf0.5Zr0.5O2 at Elevated Temperatures
Nashrah Afroze, Jihoon Choi, Salma Soliman et al. (+10 more)
Breaking the
memory wall in advanced computing architectures will require complex 3D integration of emerging
memory materials such as ferroelectrics-either within the back-end-of-line (BEOL) of CMOS front-end processes or through advanced 3D packaging technologies. Achieving this integration demands that
memory materials exhibit high thermal resilience, with the capability to operate reliably at elevated temperatures such as 125C, due to the substantial heat generated by front-end transistors. However, silicon-compatible HfO2-based ferroelectrics tend to exhibit antiferroelectric-like behavior in this temperature range, accompanied by a more pronounced wake-up effect, posing significant challenges to their thermal reliability. Here, we report that by introducing a thin tungsten
oxide (WO3-x) layer-known as an oxygen reservoir-and carefully tuning its oxygen content, ultra-thin Hf0.5Zr0.5O2 (5 nm) films can be made robust against the ferroelectric-to-antiferroelectric transition at elevated temperatures. This approach not only minimizes polarization loss in the pristine state but also effectively suppresses the wake-up effect, reducing the required wake-up cycles from 105 to only 10 at 125C- a qualifying temperature for back-end
memory integrated with front-end logic, as defined by the JEDEC standard. First-principles density functional theory calculations reveal that WO3 enhances the stability of the ferroelectric orthorhombic phase at elevated temperatures by increasing the tetragonal-to-orthorhombic phase energy gap, and promoting favorable
phonon mode
evolution, thereby supporting o-phase formation under both thermodynamic and kinetic constraints.
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All authors Nashrah Afroze, Jihoon Choi, Salma Soliman, Chang Hoon Kim, Jiayi Chen, Yu-Hsin Kuo, Mengkun Tian, Chengyang Zhang, Priyankka Gundlapudi Ravikumar, Suman Datta, Andrea Padovani, Jun Hee Lee, Asif Khan
Materials Science · Cross-listed from physics.optics
Soft X-ray Reflection Ptychography
Damian Guenzing, Dayne Y. Sasaki, Alexander S. Ditter et al. (+9 more)
Scanning transmission X-ray microscopy and ptychography have become mature tools for high-resolution, element-specific imaging of nanoscale structures. However, transmission geometries impose stringent constraints on sample thickness and preparation, thereby limiting investigations of extended or bulk specimens, especially in the soft X-ray region. Here, we demonstrate reflection geometry soft X-ray ptychography as a robust imaging mode. Instrumental feasibility and spatial resolution are established using a lithographically defined Siemens
star and barcode test pattern on a multilayer substrate. We empirically demonstrate a full-pitch spatial resolution of ca. 45 nm from
Fourier ring correlation analysis of the reconstructed object. The results highlight the potential of the reflection geometry for nondestructive X-ray studies of materials without the need for transmissive samples.
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All authors Damian Guenzing, Dayne Y. Sasaki, Alexander S. Ditter, Abraham L. Levitan, Eric M. Gullikson, Scott Dhuey, Arian Gashi, Hendrik Ohldag, Sujoy Roy, David A. Shapiro, Riccardo Comin, Sophie A. Morley
Materials Science
Vibrational and Electronic Properties of Np2O5 from Experimental Spectroscopy and First Principles Calculations
Binod K Rai, Shuxiang Zhou, Benjamin R. Heiner et al. (+7 more)
High-valence actinide
oxides are critical to understanding the behavior of 5f-electrons, yet their structural and electronic properties remain poorly understood due to challenges in synthesis and handling. We report the first Raman spectroscopic study of single-crystalline Np2O5 and the first scanning tunneling spectroscopy (STS) measurement on any neptunium-containing material. Hydrothermally synthesized
crystals were structurally verified by X-ray diffraction. Raman spectra revealed sharply resolved vibrational features, including previously unreported low-frequency modes. STS measurements revealed a band gap of 1.5 eV. Density functional theory (DFT) enables vibrational mode assignments, reveals neptunium-dominated low-frequency
phonons, oxygen-dominated high-frequency modes, and predicts an indirect band gap of 1.68 eV. This predicted value is in excellent agreement with the experimentally measured STS gap. This combined Raman, DFT, and STS approach provides a robust framework for correlating
lattice dynamics and electronic structure in actinide materials, providing
benchmark data for Np2O5, and opening new avenues for probing structure-property relationships in complex f-electron materials.
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All authors Binod K Rai, Shuxiang Zhou, Benjamin R. Heiner, Gia Thinh Tran, Jennifer E. S. Szymanowski, Santosh KC, Thomas C. Shehee, Peter C. Burns, Miles F. Beaux II, Luke R Sadergaski
Materials Science · Cross-listed from cond-mat.soft
Tunable Nanoparticle Stripe Patterns at Inclined Surfaces
Suman Bhattacharjee, Sanjoy Khawas and Sunita Srivastava
Periodic assemblies of nanoparticles are central to surface patterning, with applications in biosensing, energy conversion, and nanofabrication. Evaporation of colloidal droplets on substrates provides a simple yet effective route to achieve such assemblies. This work reports the first experimental demonstration of patterns formed through stick-slip dynamics of the three-phase contact line during evaporation of gold nanoparticle suspensions on inclined substrates. Variation in nanoparticle concentration and substrate inclination alter the balance of interfacial and gravitational forces, producing multiple stick-slip events that generate periodic stripes. Stripe density exhibits a sinusoidal dependence on inclination angle, while inter-stripe spacing remains nearly invariant. Independent control over inter-stripe spacing is achieved through adjustment of nanoparticle or surfactant concentration. These results highlight the complex interplay of gravitational and interfacial forces in directing periodic nanoparticle assembly and establish a versatile, programmable framework for surface patterning with tunable nano/microscale dimensions.
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