Materials Science · Cross-listed from physics.app-ph
SPARSE – Efficient High-Resolution SEM Imaging of Rare Microstructural Features Across Large Areas by Selective Rescanning
Tom Reclik, Jan Gerlach, Maximilian A. Wollenweber et al. (+3 more)
Characterisation of rare microstructural features in scanning electron microscopy (SEM) requires imaging large areas at high resolution. This leads to prohibitively long acquisition times. We present an open-source Python framework that addresses this bottleneck through a two-stage approach: a fast scan identifies regions of interest, which are then selectively rescanned with imaging parameters suitable for quantitative analysis. The framework defines a generic microscope interface and a modular detection interface, allowing adaptation to different microscope platforms and detection methods. Scanning, detection, and rescanning are parallelized using separate processes, ensuring that computation time does not extend acquisition time. The two processes communicate exclusively through queues, avoiding shared mutable state and eliminating the need for explicit synchronization. We validate the framework on damage detection in dual-phase DP800 steel using a Tescan Clara SEM. For a representative configuration a detection rate of 99 % is achieved at approximately 58 % of the conventional acquisition time. At 95 % detection rate, acquisition time drops to 19 %. These time savings estimates represent lower bounds based on the ratio of scanned pixels. The complete implementation will be made available upon publication and upon request during peer-review.
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All authors Tom Reclik, Jan Gerlach, Maximilian A. Wollenweber, Yannis P. Korkolis, Sandra Korte-Kerzel, Ulrich Kerzel
Materials Science
Exascale Multi-Task Graph Foundation Models for Imbalanced, Multi-Fidelity Atomistic Data
Massimiliano Lupo Pasini, Jong Youl Choi, Kshitij Mehta et al. (+8 more)
We present an exascale workflow for materials discovery using atomistic graph foundation models built on HydraGNN. We jointly train on 16 open first-principles
datasets (544+ million structures covering 85+ elements) using a multi-task architecture with per-
dataset heads and a scalable ADIOS2/DDStore data pipeline. On Frontier, we execute six large-scale DeepHyper hyperparameter optimization campaigns in FP64 and promote the top-performing message-passing models to sustained 2,048-node training, yielding a PaiNN-based lead model. The resulting model enables billion-scale screening, evaluating 1.1 billion atomistic structures in 50 seconds, compressing a workload that would require years of first-principles computation, and supports data-scarce fine-tuning across diverse downstream tasks. We quantify precision-performance tradeoffs (BF16/FP32/FP64), demonstrate transfer across twelve chemically diverse downstream tasks, and establish seamless strong- and weak-scaling across Frontier, Aurora, and Perlmutter. This work allows fast and reliable exploration of vast chemical design spaces that are otherwise inaccessible to first-principles methods.
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All authors Massimiliano Lupo Pasini, Jong Youl Choi, Kshitij Mehta, Richard Messerly, Rylie Weaver, Linda Ungerboeck, Isaac Lyngaas, Benajmin Stump, Ashwin M. Aji, Karl W. Schulz, Jorda Polo
Materials Science
Environment-dependent tight-binding models from ab initio pseudo-atomic orbital Hamiltonians
Marco Buongiorno Nardelli
Ab initio pseudo-atomic orbital (PAO)
Hamiltonians express the electronic structure of a solid in a compact, localized basis that spans the same
Hilbert space as a conventional Slater–Koster tight-binding model, thereby providing an exact ab initio representation without any loss of accuracy. Building on this correspondence, we develop an environment-dependent tight-binding (EDTB) framework in which Slater–Koster hopping integrals are augmented with bond-screening functions that capture the local coordination environment. All parameters are determined by fitting to the PAO
eigenvalue spectrum across multiple atomic configurations simultaneously, which breaks the degeneracy between screening and hopping parameters and yields physically meaningful, transferable models capable of generating
Hamiltonians for large systems with ab initio precision. We demonstrate the efficiency and accuracy of the approach on four prototypical systems: bulk platinum, silicon surfaces, Si/Ge~[001] superlattices, and twisted
bilayer graphene with up to $4{,}324$ atoms. The method is implemented in the \paoflow{} code and integrates seamlessly with its full post-processing suite, enabling the evaluation of a broad range of electronic, optical, and transport properties.
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Materials Science
Ultra-high-vacuum cluster tool for epitaxial synthesis and optical spectroscopy of reactive 2D materials
M. Dembecki, J. Schabesberger, M. Bissolo et al. (+8 more)
The large-area synthesis of high-crystalline-quality two-dimensional (2D) materials is at the core of novel material integration for
semiconductor technology. This effort relies on developing fabrication and characterization techniques that can uncover the material's intrinsic properties by preserving its pristine conditions. In this article, we present an all ultra-high-
vacuum cluster for the growth using molecular beam epitaxy of 2D
semiconductors that are unstable under ambient conditions and optical spectroscopy using low temperature (20 K) photoluminescence and Raman scattering. The optical chamber of the setup provides micrometer scale spatial resolution and the ability to scan the entire wafer. The performance of its setup regarding spatial resolution, temperature control over a temperature range of 20-300 K using a closed-cycle cryostat and long-term preservation are demonstrated using as-grown post-transition metal monochalcogenides. Furthermore, we introduce a deconvolution-based
algorithm to recover spatial information under vibration using a system-specific point-spread function. This enables in situ analysis of the structural and optoelectronic properties of as-grown materials in their pristine form, providing rich and reproducible feedback for both fundamental studies and the optimization of scalable 2D material growth toward integration in advanced devices.
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All authors M. Dembecki, J. Schabesberger, M. Bissolo, A. Thurn, A. Ulhe, P. Avdienko, J. Ulrichs, H. Riedl, G. Koblmüller, E. Zallo, J.J. Finley
Materials Science
Configuration-dependent electronic and optical properties of 2D Mo$_{1-x}$W$_x$S$_2$ alloys across the full composition range
M. Szyszko and M. Birowska
Here we analyze multiple
symmetry-inequivalent atomic configurations across the entire composition range of the isovalent and isostructural Mo$_x$W$_{1-x}$S$_2$
alloy using density-functional theory and Monte Carlo simulations. Our results show that although structural stability and energetics are largely composition-driven, the electronic and optical properties exhibit configuration dependence, with local atomic arrangements critically shaping band-edge splitting, valley structure, effective-mass anisotropy, and optical selection rules. In contrast to the pristine monolayers, even in the absence of
spin-orbit coupling (SOC), splitting of the band edges at the $K$ point is observed across the entire composition range. In particular, while the valence-band maximum (VBM) remains largely robust, the conduction-band minimum (CBM) shows strong configuration-dependent splitting from few meV up to hundredths of meV. This behaviour leads to a non-trivial dependence of the valley energetics. Configurations with well-separated conduction bands support additional optically active transitions beyond the conventional A and B
excitons in MoS$_2$ and WS$_2$ monolayers, whereas nearly degenerate cases exhibit a reduced number of allowed transitions, observed for specific configurations at $x = 1/3$ and $x = 2/3$. These results demonstrate that the number and character of optically active transitions are governed not only by composition, but also by the microscopic arrangement of atoms. Moreover, we found the hole effective masses at the VBM show configuration-dependent anisotropy, reflecting sensitivity to local
symmetry breaking and implying direction-dependent transport.
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Materials Science · Cross-listed from physics.comp-ph
Distributional Inverse Homogenization
Arnaud Vadeboncoeur, Mark Girolami, Kaushik Bhattacharya et al. (+1 more)
For many materials, macroscopic mechanical behavior is determined by an intricate microstructure. Understanding the relation between these two scales helps scientists and engineers design better materials. The relation which maps microstructure to bulk material properties can be understood via the well-established theory of homogenization. However inverting the homogenization process, to recover microstructural information from measured macroscopic properties, is fraught with difficulties because of the averaging processes that underlie homogenization. Therefore, scientists and engineers usually need recourse to more invasive, often highly localized, investigations to estimate the microstructure. In this work, we develop a noninvasive methodology by which one can leverage large collections of measured bulk material properties to infer information about the statistics of microstructure at a global level. We call this, distributional inverse homogenization. We study this problem in one and two dimensions, considering both periodic and
stochastic homogenization. We demonstrate the methodology in the context of 2D Voronoi constructions and underpin the observed empirical success with theory in 1D. We also show how the natural spatial variability of microstructure can be exploited to gather data that enables distributional inversion. And we concurrently learn a surrogate model, approximating the homogenization map, that accelerates the resulting computations in this setting. The work formulates a new class of inverse problems, bridging ideas from probability and homogenization to facilitate the inference of microstructural material variability from macroscopic measurements.
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All authors Arnaud Vadeboncoeur, Mark Girolami, Kaushik Bhattacharya, Andrew M. Stuart
Materials Science
Generative design of inorganic materials
Jose Recatala-Gomez, Haiwen Dai, Zhu Ruiming et al. (+9 more)
Materials discovery is fundamental to advance next-generation technologies as well as for sustainable and circular economy. Beyond computational screening, generative models are efficient at finding materials with desired properties, via multi-modal learning using multiscale data. This perspective examines the landscape of generative design for inorganic materials and discusses the integration of multi-modal learning with high-throughput experimental validation. We contextualize these challenges through the lens of a generative design framework as a unified approach to address the data-driven inverse design of functional materials. The central idea of the framework is constructed around a foundation AI model for inorganic materials interlinked deeply with various property databases and high-throughput experiments via a machine learning driven closed loop, which enables the framework to solve key challenges in functional materials. We argue that domain-specific implementations of such integrated workflows represent a promising pathway toward the unresolved challenge of data-driven inverse design for atom-engineered inorganic functional materials.
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All authors Jose Recatala-Gomez, Haiwen Dai, Zhu Ruiming, Nikita Kazeev, Nong Wei, Gang Wu, Maciej Koperski, Tan Teck Leong, Andrey Ustyuzhanin, Gerbrand Ceder, Kostya Novoselov, Kedar Hippalgaonkar
Materials Science
Natural Language Embeddings of Synthesis and Testing conditions Enhance Glass Dissolution Prediction
Sajid Mannan, K. Sidharth Nambudiripad, Indrajeet Mandal et al. (+2 more)
Long-term chemical durability of glass, crucial for immobilizing
nuclear waste, is governed by glass properties such as composition, surface geometry, as well as external factors like thermodynamic conditions and surrounding medium. Despite decades of research, there are no models that account for these intrinsic and extrinsic factors to predict the dissolution rates of glass compositions. To address this challenge, we evaluate the role of natural
language embeddings capturing the synthesis and testing conditions in enhancing the predictability of glass dissolution. Evaluating the approach on hand-curated ~700 datapoints extracted from the literature, we reveal that the machine learning (ML) model including natural
language embeddings (NLP-ML) outperforms classical ML model in predicting glass dissolution rate. Furthermore, we developed a generalizable ML model by transforming the compositional features to structural descriptors of glass alongside NLP-derived features, enabling extrapolation capability to glass compositions with completely new elements absent in the training data. Evaluating this model on a completely new
dataset of glass compositions 34 chemical components in contrast to the training
dataset that had only 28 components, we demonstrate that the model indeed exhibits generalizability to glass compositions that are out-of-distribution. Altogether, this integrated approach offers a pathway towards high-fidelity glass dissolution prediction and accelerate the discovery of novel glass compositions with tailored durability for sustainable
nuclear waste management.
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All authors Sajid Mannan, K. Sidharth Nambudiripad, Indrajeet Mandal, Nitya Nand Gosvami, N. M. Anoop Krishnan
Materials Science
Twist-engineering of a robust Quantum Spin Hall phase in $\beta$-/flat bismuthene bilayer from first principles
Umberto Pelliccia, Alberto M. Ruiz, Diego López-Alcalá et al. (+3 more)
Twist-engineering of topological phases in two-dimensional materials offers a powerful route to modulate electronic structure beyond conventional strain or chemical control. In particular, group 15 (pnictogens) monolayers such as bismuthene provide an ideal platform due to their strong intrinsic
spin-orbit coupling (SOC) and robust topological character. Here, we investigate a previously unexplored
heterostructure consisting of a $\beta$-bismuthene monolayer rotated by 30$^\circ$ on a planar bismuthene layer stabilized on a SiC(0001) substrate. Using first-principles calculations, we demonstrate that this specific rotational
alignment induces a unique interlayer orbital hybridization which, combined with the strong SOC and the naturally broken inversion
symmetry, gives rise to a pronounced Rashba
spin-splitting, absent in the isolated monolayers. The topological nature of the system is confirmed through the calculation of the Z2 topological invariant and
Spin Hall Conductivity (SHC), revealing a robust
Quantum Spin Hall (QSH) phase with an enhanced topological response compared to the individual layers. Furthermore, we explore the chemical tunability of this system via Sb substitution, showing that the gradual reduction of SOC systematically narrows the band gap while preserving the non-trivial
topology. Our results establish large-angle twisted group 15
heterostructures as a versatile platform for engineering
spin-orbit-driven phenomena and advancing topological spintronics.
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All authors Umberto Pelliccia, Alberto M. Ruiz, Diego López-Alcalá, Gonzalo Abellán, Rafael Gonzalez-Hernandez, José J. Baldoví
Materials Science
Symmetry-protected coexistence of a nodal surface and multiple types of Weyl fermions in $P6_3$-$\text{B}_{30}$
Xiao-Jing Gao, Yanfeng Ge and Yan Gao
The coexistence of topological states with different dimensionalities in a single crystalline system offers a unique platform to study the interplay of distinct fermionic excitations. Here, integrating first-principles calculations with
symmetry analysis, we propose the three-dimensional boron allotrope $P6_3$-$\text{B}_{30}$ as an ideal, structurally stable candidate for exploring multidimensional topological physics. Benefiting from the practically negligible
spin-orbit coupling of the light-element framework, $P6_3$-$\text{B}_{30}$ operates as a pristine spinless topological semimetal. We show that the combined time-reversal and twofold screw
symmetry ($\mathcal{T}S_{2z}$) enforces a robust two-dimensional nodal surface on the $k_z = \pi$ plane via a Kramers-like degeneracy. Concurrently, the system hosts a diverse set of zero-dimensional Weyl
fermions – including an unconventional double-Weyl point ($\mathcal{C} = -2$), conventional Type-I WPs ($\mathcal{C} = -1$), and completely tilted Type-II WPs ($\mathcal{C} = +1$) – emerging at the high-
symmetry points $\Gamma$ and K, as well as along the H-K path, protected by $C_6$ and $C_3$ crystalline rotational
symmetries. Crucially, the substantial momentum-space separation between the nodal surface and Weyl points allows for their unambiguous independent resolution. Calculations of the (100) surface states reveal distinct, nontrivial
Fermi arcs connecting Weyl nodes of opposite chirality. This work establishes $P6_3$-$\text{B}_{30}$ as a compelling material platform for investigating the physics of multidimensional hybrid topological
fermions and their interplay.
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Materials Science
Magnetic Microscopy of Skyrmions in Magnetic Thin Films with Chiral Overlayers
Buddhika Hondamuni, Théo Balland, Fabian Kammerbauer et al. (+15 more)
Topologically nontrivial
magnetic textures such as skyrmions offer promising opportunities for spintronic applications. In recent years, it has been shown that the
magnetic properties of layered materials can be affected by depositing
chiral molecules on the surface, while the influence of
chiral overlayers on skyrmion properties such as their stability and interactions remains largely unexplored. To address this challenge, we employ wide-field nitrogen-vacancy (NV) magnetometry to directly image skyrmions in
chiral-molecule-functionalized
magnetic thin films, enabling quantitative mapping of
magnetic stray fields over extended areas under ambient conditions. Using pixel-resolved optically detected
magnetic resonance (ODMR) combined with controlled
magnetic fields, we reproducibly nucleate and probe skyrmion states in CoFeB
ferromagnetic samples, enabling quantitative investigation of their properties. We find evidence for enantioselective and
magnetic-field-polarity-dependent modifications of skyrmion diameter, spacing, and shape, pointing to a possibility of molecular control of topological
spin textures via magneto-
chiral coupling.
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All authors Buddhika Hondamuni, Théo Balland, Fabian Kammerbauer, Ashish Moharana, Bindu, Amandeep Singh, Meital Ozeri, Shira Yochelis, Yossi Paltiel, Omkar Dhungel, Zeeshawn Kazi, Kai-Mei C. Fu, Hideyuki Watanabe, Mathias Kläui, Arne Wickenbrock, Nir Bar-Gill, Angela Wittmann, Dmitry Budker
Materials Science · Cross-listed from physics.optics
Twistoptics in Planar Heterostructures with an Arbitrary Number of Rotated 3D Thin Layers and 2D Conductive Sheets
Christian Lanza, José Álvarez-Cuervo, Kirill V. Voronin et al. (+5 more)
Twistoptics has recently emerged as a branch of nano-optics that explores light propagation in stacks of thin anisotropic layers rotated relative to one another. The concept is particularly relevant for polaritons – hybrid light-matter quasiparticles – in van der Waals (vdW) materials, where strong in-plane anisotropy and deep subwavelength confinement make the polaritonic dispersion highly sensitive to interlayer twist angles. This sensitivity enables exotic phenomena such as canalization, i.e., diffraction-free propagation, with potential applications ranging from thermal management to super-resolution imaging. Despite rapid progress, a general analytical framework to describe polariton propagation in twisted planar
heterostructures has been missing. Here we present an analytical model for planar stacks comprising an arbitrary number of finite-thickness anisotropic (biaxial) layers and infinitesimally thin anisotropic conductive sheets. The formalism and its high-momentum and thin-film approximations predict key polaritonic observables, such as wavelength, propagation length, and electromagnetic field distributions. We also provide open-access numerical scripts implementing the model to support their practical use. Together, these results provide a general theoretical foundation for twistoptics and should facilitate the discovery and accelerate the implementation of twist-engineered polaritonic phenomena across the electromagnetic spectrum.
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All authors Christian Lanza, José Álvarez-Cuervo, Kirill V. Voronin, Gonzalo Álvarez-Pérez, Aitana Tarazaga Martín-Luengo, Javier Martín-Sánchez, Alexey Y. Nikitin, Pablo Alonso-González
Materials Science · Cross-listed from cond-mat.mes-hall
Giant Room-Temperature Third-Order Electrical Transport in a Thin-Film Altermagnet Candidate
Hongyu Chen, Peixin Qin, Ziang Meng et al. (+14 more)
Quantum geometry, a
quantum mechanical quantity comprised of Berry
curvature and
quantum metric, describes the
geometric structure of the electronic bands in solids. The correlation between nontrivial
quantum geometry and
quantum materials leads to new findings in condensed matter systems. Here we demonstrate that altermagnets, with spontaneously broken time-reversal (T)- half-
lattice-translation and parity-time
symmetry, host both T-odd and T-even
quantum geometric quantities that simultaneously manifest themselves despite the vanishing net magnetization. Consequently,
giant room-temperature third-order electrical transport responses with sizable
quantum geometric contributions are observed in (101)-oriented RuO2 thin films, an altermagnetic candidate; in particular, the third-order
Hall effect is intimately correlated with altermagnetic order and can serve as a promising tool for detecting the Neel vector. Our work not only supports the existence of altermagnetism in 8-nm-thick RuO2 thin films, but also shows altermagnets as a versatile platform for exploring
quantum geometry and constructing
quantum electronic and spintronic devices.
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All authors Hongyu Chen, Peixin Qin, Ziang Meng, Guojian Zhao, Kai Chen, Chuanying Xi, Xiaoning Wang, Li Liu, Zhiyuan Duan, Sixu Jiang, Jingyu Li, Xiaoyang Tan, Jinghua Liu, Jianfeng Wang, Huiying Liu, Chengbao Jiang, Zhiqi Liu
Materials Science · Cross-listed from cond-mat.str-el
Low temperature Spin freezing and Diffuse Magnetic Correlations in Tb$_{2}$Zr$_{2-x}$Ti$_{x}$O$_{7}$ (x = 0, 0.5)
Sujata Singh, Leon Carstens, M. Duc Le et al. (+2 more)
Structural disorder in the magnetically frustrated pyrochlore system leads to intriguing
magnetic states. We present the thermodynamic behavior and short range
magnetic correlations in Tb$_{2}$Zr$_{2}$O$_{7}$ and Tb$_{2}$Zr$_{1.5}$Ti$_{0.5}$O$_{7}$ compounds. The parent compound Tb$_{2}$Zr$_{2}$O$_{7}$ has defect fluorite structure, which evolves toward the pyrochlore phase on Ti doping at Zr site. There is no long range
magnetic order down to 0.4 K, and a
magnetic field dependent
spin freezing evolves below 1.25 K and 1.05 K for the parent and doped compounds, respectively. The ac susceptibility measurements indicate slow
spin relaxation process below 20 K in these compounds. Inelastic
neutron scattering reveals broad diffuse scattering, indicative of short range correlations at low temperature, owing to local structural distortions and persistent
spin fluctuations. These results suggest a correlated, disorder influenced
magnetic state in Tb$_{2}$Zr$_{2}$O$_{7}$, Tb$_{2}$Zr$_{1.5}$Ti$_{0.5}$O$_{7}$ compounds.
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All authors Sujata Singh, Leon Carstens, M. Duc Le, R. Klingeler, C.S. Yadav
Materials Science · Cross-listed from physics.optics
Breakdown of spallation in multi-pulse ultrafast laser ablation
David Redka, Julian Vollmann, Nicolas Thomae et al. (+2 more)
Ultrashort-pulse
laser ablation of metals near damage threshold is governed by homogeneous spallation, in which tensile unloading releases a nanometre-thin
liquid film whose optical signatures are temporally evolving concentric Newton rings in pump–probe experiments. This well-established picture rests almost exclusively on single-pulse results obtained on ideally flat surfaces, yet application-oriented processing invariably operates in a multi-pulse regime in which each pulse irradiates a surface progressively modified by preceding pulses. Whether homogeneous spallation persists under these conditions has remained an open question. Here we resolve this question using time-resolved pump-probe interferometry applied pulse by pulse to austenitic stainless steel. We show that homogeneous spallation dominates the first pulse, while its contribution is strongly reduced for the second pulse. By the third pulse, Newton rings vanish and sustained surface bulging collapses, with the optical transients fully saturating into a phase-explosion-like signature by the fourth pulse.
Fourier-domain coherence analysis rules out roughness-induced decoherence as an optical artefact. Four independent observables, spanning time-resolved and final-state measurements, converge on the same transition after three to four pulses. Spallation-layer formation, widely invoked to explain ultrashort-pulse ablation of metals, is thus a single-pulse phenomenon rather than a multi-pulse ablation mechanism.
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All authors David Redka, Julian Vollmann, Nicolas Thomae, Maximilian Spellauge, Heinz P. Huber
Materials Science
On phase separation and crystallization of Ge-rich GeSbTe alloys from atomistic simulations with a machine learning interatomic potential
Omar Abou El Kheir, Dario Baratella and Marco Bernasconi
We developed a machine learning interatomic potential (MLIP) for Ge-rich GeSbTe
alloys of interest for applications in phase change
memories embedded in microcontrollers. The MLIP was generated by fitting with a neural network method a large database of energies and forces computed within density functional theory of elemental, binary, stoichiometric and non-stoichiometric ternary
alloys in the Ge-Sb-Te phase diagram. The MLIP is demonstrated to be highly transferable to large regions of the phase diagram around the compositions included in the
dataset. The MLIP is then exploited to simulate the crystallization with phase separation of three Ge-rich
alloys on the Ge-Sb$_2$Te$_3$ and Ge- Ge$_2$Sb$_2$Te$_5$ tie-lines that correspond to the set process of the
memory cell. The transformation on the ns time scale and at 600 K, comparable to the operation conditions of the
memory, yields crystalline cubic GeTe slightly Sb-doped and amorphous GeSb and Ge. These metastable phases differ from the thermodynamically stable products and form due to kinetics effects on the short time span of the set operation in phase change
memories.
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Materials Science
Complex surface patterning in homo- and heteroepitaxial contexts: (simultaneous) step bunching and step meandering
Vassil Ivanov, Vesselin Tonchev, Marta A. Chabowska et al. (+2 more)
We confront a meso-scale continuum model, archetypical for the heteroepitaxial context, with an atomistic Vicinal Cellular Automaton (VicCA), built as a homoepitaxial counterpart, to show that in (2+1)D complex surface instabilities are fundamental growth phenomena rather than context-specific artifacts. Our approach is to first construct a Ginzburg-Landau-type model, designed to extend the previously (1+1)D Tersoff-type models to (2+1)D. We complement the continuum approach with a discrete one - the VicCA, in which we use a novel version of the potential landscape for the diffusing particles - a double-well potential located at each step edge. Importantly, this framework also captures both step bunching and step meandering. While these behaviors are rarely treated together in earlier approaches, they naturally coexist in real materials. Thus we establish a cross-context correspondence at the level of obtained morphologies and morphology diagrams and, additionally, a multiscale perspective on the governing parameters, bridging the gap between the mesoscale and atomistic modeling.
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All authors Vassil Ivanov, Vesselin Tonchev, Marta A. Chabowska, Hristina Popova, Magdalena A. Załuska-Kotur
Materials Science · Cross-listed from physics.optics
Non-Hermitian reshaping of high-order Landau modes
Zhihao Wang, Jie Jiang, Yanji Zheng et al. (+6 more)
When charged particles are subjected to strong
magnetic fields, they form discrete energy levels known as Landau levels. The Landau levels consist of a series of degenerate states of Landau modes, making them a promising platform for large-capacity information processing. However, to date, exploiting the high-order Landau modes and control their spatial distributions has remained elusive. Here, we propose to construct
magnetic fields, electric fields, and imaginary momentum simultaneously to reshape high-order Landau modes in non-Hermitian systems. By building a non-Hermitian electric
circuit platform, we experimentally realize pseudomagnetic fields via inhomogeneous coupling and pseudoelectric fields via a gradient on-site potential, while simultaneously introducing an imaginary momentum via non-reciprocal coupling. We directly observe multi-frequency single-peak localization of high-order Landau modes. Our work provides a universal method for manipulating high-order Landau modes and exploring applications in nonHermitian systems, such as frequency multiplexing and wave packet reshaping.
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All authors Zhihao Wang, Jie Jiang, Yanji Zheng, Wen Zhao, Chenyang Wang, Zhiwei Guo, Yong-Chun Liu, Shuang Zhang, Cuicui Lu
Materials Science
Spatial deformation of a ferromagnetic elastic rod
G. R. Krishna Chand Avatar and Vivekanand Dabade
Ferromagnetic elastic slender structures offer the potential for large actuation displacements under modest external
magnetic fields, due to the magneto-mechanical coupling. This paper investigates the phase portraits of the
Hamiltonian governing the three-dimensional deformation of inextensible
ferromagnetic elastic rods subjected to combined terminal tension and twisting moment in the presence of a longitudinal
magnetic field. The total energy functional is formulated by combining the Kirchhoff elastic strain energy with micromagnetic energy contributions appropriate to soft and hard
ferromagnetic materials: magnetostatic (demagnetization) energy for the former, and exchange and Zeeman energies for the latter. Exploiting the circular cross-sectional
symmetry and the integrable structure of the governing equations, conserved Casimir invariants are identified and the
Hamiltonian is reduced to a single-degree-of-freedom system in the Euler polar angle. Analysis of the resulting phase portraits reveals that purely elastic and hard
ferromagnetic rods undergo a supercritical
Hamiltonian Hopf pitchfork bifurcation, whereas soft
ferromagnetic rods exhibit this bifurcation only within a restricted range of the magnetoelastic parameter, $0<\tilde{K}_{dM}<1/8$. Both helical and localized post-buckling configurations are analyzed, and the corresponding load-deformation relationships are systematically characterized across a range of loading scenarios. Localized buckling modes, corresponding to homoclinic orbits in the
Hamiltonian phase space, are constructed numerically. In contrast to the purely elastic case, the localized configurations of soft
ferromagnetic rods exhibit non-collinear extended straight segments, a geometrically distinctive feature arising directly from the magnetoelastic coupling.
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Materials Science · Cross-listed from physics.optics
Tuning light-matter interaction of near-infrared nanoplasmonic scintillators
Michał Makowski, Dominik Kowal and Muhammad Danang Birowosuto
Nanoplasmonic modification of scintillation has so far been explored mainly in the weak-coupling regime, where changes in the local density of optical states enhance radiative recombination via Purcell-type rate engineering. By contrast, strong light-matter coupling generates hybrid states that modify emission dynamics beyond simple decay-rate acceleration, but its implications for scintillator nanocrystals (NCs) under ionizing radiation remain poorly understood. All of these effects are beneficial for near-infrared scintillators, which are typically slow and have low brightness. Here, we present a
quantum-optical framework to investigate how near-infrared scintillator NCs coupled to nanoplasmonic
antennas evolve from weak coupling toward strong light-matter coupling. We compare broad- and narrow-
antenna platforms with single and periodic Au nanorods and
benchmark them against conductive plasmonic
antennas based on indium tin
oxide and
graphene. As representative emitters, we consider wide-band PbS NCs and narrow-band cubic Lu2O3:Er3+ scintillators. The calculations show that the onset of strong-coupling signatures is jointly governed by emitter dephasing and the
antenna linewidth, with narrow-band emitters coupled to spectrally narrow
antennas providing the most favorable conditions. Among the platforms considered,
graphene gives the lowest threshold (g = 4 meV) for observable coherent exchange owing to its ultranarrow
antenna linewidth (ąppa} = 3.5 meV). These results identify near-infrared conductive nanoantennas, particularly
graphene-based ones, as promising platforms for accessing hybrid scintillation regimes relevant to radiation detection.
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Materials Science
Anion Ordering and Phase Stability Govern Optical Band Gaps in BaZr(S,Se)3
Erik Fransson, Michael Xu, Prakriti Kayastha et al. (+6 more)
Chalcogenide perovskites have emerged as promising lead free materials for photovoltaic and thermoelectric applications. Among them, BaZrS3 has attracted particular
attention due to its thermal and chemical stability, favorable optoelectronic properties, and low thermal conductivity. Here, we combine molecular dynamics and Monte Carlo simulations based on machine learned interatomic potentials with scanning transmission electron microscopy to investigate mixing thermodynamics and phase stability in the BaZr(S,Se)3 system. We identify an unusual ordered structure that persists at room temperature, most prominently at 33% S, where S and Se atoms form alternating layers within the
crystal. Free energy calculations yield the temperature composition phase diagram, including a nonperovskite delta phase in the Se rich limit and a perovskite phase in the S rich limit, separated by a broad two phase region. Analysis of the dielectric function and the absorption coefficient demonstrates that composition,
crystal structure, and anion ordering jointly control the optical band gap. Selenium alloying enables tuning between approximately 1.6 and 1.9eV, while anion ordering within a given composition reduces the gap by about 0.12eV. Lastly, variations between structural polymorphs give rise to band gap differences of up to 0.4eV.
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All authors Erik Fransson, Michael Xu, Prakriti Kayastha, Kevin Ye, Ida Sadeghi, Rafael Jaramillo, James M. LeBeau, Lucy Whalley, Paul Erhart
Materials Science
A Generalized Method for Spatial Operations on Material Property Matrices and Its Applications to Dynamic Problems
Hongjin Xiong, Zhonghui Xia, Xuan Ye et al. (+1 more)
The physical properties of matter are described by coefficient
matrices governed by
crystal symmetry. Existing methods to apply spatial operations to these
matrices, such as direct inspection or tensor-based approaches, are cumbersome and difficult to generalize for higher-order
matrices. Furthermore, dynamic properties are often neglected due to the lack of tools for constructing dynamic operation
matrices. We present a generalized “input-coefficient-output” (ICO) approach for constructing spatial operation
matrices across diverse physical systems, including high-order nonlinear optics, elasticity, electrostriction, and magnetostriction. The ICO approach requires only the orders of input and output vectors, simplifying mathematical complexity. A Python package (the “$\chi$ program”) enables intuitive
reasoning about spatial transformations. We validate the ICO formalism by deriving reduced susceptibility
matrices for representative
crystal systems and apply it to dynamic problems. We construct dynamic models for polarized second-harmonic generation (SHG) responses under external stimuli and analyze experimental SHG data via dynamic
matrix equations. The coefficient of determination ($R^2$) shows our model fits experimental data better than conventional models. Ultimately, the ICO approach provides a concise formalism and a clear physical picture for analyzing dynamic material properties under diverse stimuli.
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All authors Hongjin Xiong, Zhonghui Xia, Xuan Ye, Teng Ma
Materials Science · Cross-listed from physics.app-ph
A Variable-Spot-Size and Multi-Frequency Square-Pulsed Source (SPS) Approach for Comprehensive Characterization of Anisotropic Thermal Transport Properties in Multilayered Thin Films
Kexin Zhang, Tao Chen, Jinlong Ma et al. (+1 more)
Multilayered thin-film structures are frequently encountered in industrial applications, where accurate thermal property characterization is essential for performance optimization. These films, typically ranging from nanometers to micrometers in thickness, often exhibit anisotropic thermal conductivity and non-bulk heat capacity, which are challenging to measure. In this study, we introduce a variable-spot-size and multi-frequency square-pulsed source (SPS) method for the simultaneous determination of anisotropic thermal conductivities, heat capacities, and interfacial thermal conductance in multilayered systems. By leveraging a broad modulation frequency range (1 Hz to 10 MHz) and tunable
laser spot sizes, the SPS method enhances sensitivity to different thermal parameters across layers. We validate this approach on a silicon-on-
insulator (SOI) sample comprising a 1.59 um Si layer, 1.03 um SiO2 layer, and a silicon substrate with a 122 nm aluminum (Al) transducer. The SPS method successfully extracts seven key thermal parameters, including the in-plane and cross-plane thermal conductivities and heat capacity of the Si film, the thermal conductivity and heat capacity of the SiO2 layer, the thermal conductivity of the substrate, and the interfacial thermal conductance between Al and Si. Temperature-dependent measurements from 80 to 500 K showed excellent agreement with literature values and first-principles predictions, confirming the method's accuracy and reliability. These results demonstrate the SPS method as a powerful tool for comprehensive thermal characterization of complex multilayered structures, with implications for both fundamental research and practical applications.
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All authors Kexin Zhang, Tao Chen, Jinlong Ma, Puqing Jiang