Materials Science · Cross-listed from physics.optics
Anisotropic Dielectric Function of Graphite Probed by Far- and Near-Field Spectroscopies
A. Toksumakov, G. Ermolaev, D. Grudinin et al. (+7 more)
Graphite is a cornerstone material for revolutionary technologies, from energy storage to the entire field of two-dimensional materials. Despite its foundational role, the predictive power required for engineering emergent optical behavior in van der Waals
heterostructures is severely constrained by persistent discrepancies in reported optical constants. We resolve this long-standing ambiguity by deploying a multi-modal approach that synergizes far-field spectroscopic ellipsometry with nanoscale near-field optical probing (s-SNOM) and micro-reflectance spectroscopy. We have established a new, self-consistent set of optical constants (n and k) for both in-plane and out-of-plane crystallographic directions across the ultraviolet-to-near-infrared spectrum. This work presents a unified set of optical constants that addresses inconsistencies in the existing literature. By establishing this definitive reference, we provide the essential foundation for the quantitative modeling and engineering of light-matter interactions in the evolving landscape of carbon-based nanophotonics.
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All authors A. Toksumakov, G. Ermolaev, D. Grudinin, A. Slavich, N. Pak, G. Tikhonowski, A. Vyshnevyy, G. Tselikov, A. Arsenin, V. Volkov
Materials Science · Cross-listed from physics.chem-ph
Interaction of Polymer of Intrinsic Microporosity PIM-1 with explosive analytes at the molecular level: Combined experiment and computational modelling
Salam Mohammed, Edward B. Ogugu, Ramakant Sharma et al. (+7 more)
This work investigates the molecular-level interactions of a fluorescent microporous
polymer (PIM-1) with nitroaromatic explosives, in the context of thin film explosive sensors. Thin films of the PIM-1 were exposed to 2,4-dinitrotoluene (DNT) and 2,4,6-trinitrotoluene (TNT), and their steady-state absorption and emission spectra measured. For comparison, the response of PIM-1 to non-explosive molecules such as benzene (BN) was also explored. Complementary electronic-structure calculations were used to predict absorption and emission spectra and to determine binding energies for the PIM-1-analyte complexes. The calculations agree well with experiment and reveal that association of nitroaromatic analyte molecules with PIM-1 alters the energy levels and the arrangements of frontier orbitals, indicating significant molecular interactions. Calculations show that the electronic properties and photo-excited electron transfer can be described by interaction with a single repeat unit of the
polymer. The molecular binding, however, involves interaction with at least three repeat units, with the DNT or TNT molecule binding into a pocket in the contorted structure of the microporous
polymer. Together, the experimental and theoretical results demonstrate that PIM-1 is a promising platform for selective nitroaromatic detection and provide molecular design principles that could improve sensitivity and selectivity in future sensor materials.
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All authors Salam Mohammed, Edward B. Ogugu, Ramakant Sharma, Dominic Taylor, Graeme Cooke, Neil McKeown, Glib Baryshnikov, Hans Ågren, Ifor D.W. Samuel, Graham A. Turnbull
Materials Science · Cross-listed from cond-mat.supr-con
Effect of substrate miscut angle on critical thickness, structural and electronic properties of MBE-grown NbN films on c-plane sapphire
Anand Ithepalli, Saumya Vashishtha, Naomi Pieczulewski et al. (+7 more)
We report the structural and electronic properties of niobium nitride (NbN) thin films grown by molecular beam epitaxy on c-plane sapphire with miscut angles of $0.5^\text{o}$, $2^\text{o}$, $4^\text{o}$, and $10^\text{o}$ towards m-axis. X-ray diffraction (XRD) scans reveal that the full width at half maximum of the rocking curves around the 1 1 1 reflection of these NbN films decreases with increasing miscut. Starting from 76 arcsecs on $0.5^\text{o}$ miscut, the FWHM reduces to almost 20 arcsecs on $10^\text{o}$ miscut sapphire indicating improved structural quality. Scanning transmission electron microscopy (STEM) images indicate that NbN on c-sapphire has around 10 nm critical thickness, irrespective of the substrate miscut, above which it turns columnar. The improved structural property is correlated with a marginal increment in superconducting transition temperature $T_\text{c}$ from 12.1 K for NbN on $0.5^\text{o}$ miscut sapphire to 12.5 K for NbN on $10^\text{o}$ miscut sapphire.
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All authors Anand Ithepalli, Saumya Vashishtha, Naomi Pieczulewski, Qiao Liu, Amit Rohan Rajapurohita, Matthew Barone, Darrell Schlom, David A. Muller, Huili Grace Xing, Debdeep Jena
Materials Science · Cross-listed from physics.class-ph
On Universal Deformations and Material Preferred Directions in Anisotropic Cauchy Elasticity
Seyedemad Motaghian and Arash Yavari
In this paper we study universal deformations in anisotropic Cauchy elasticity. We show that the universality constraints of hyperelasticity and Cauchy elasticity for transversely isotropic, orthotropic, and monoclinic solids are equivalent. This implies that for each of these
symmetry classes the universal deformations and the corresponding universal material preferred directions of hyperelastic and Cauchy elastic solids are identical. This is consistent with previous findings for isotropic solids. Universal deformations and material preferred directions are therefore independent of the existence or absence of a strain energy function.
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Materials Science · Cross-listed from cond-mat.str-el
Lessons from $\alpha$-RuCl3 for pursuing quantum spin liquid physics in atomically thin materials
Claudia Ojeda-Aristizabal, Xiaohu Zheng, Changsong Xu et al. (+20 more)
Quantum spin liquids can arise from Kitaev
magnetic interactions, and exhibit fractionalized excitations with the potential for a topological form of
quantum computation. This review surveys recent experimental and theoretical progress on the pursuit of phenomena related to Kitaev magnetism in layered and exfoliatable materials, which offer numerous opportunities to apply powerful techniques from the field of atomically thin materials. We primarily focus on the
antiferromagnetic Mott
insulator $\alpha$-RuCl3, which exhibits Kitaev couplings and is readily exfoliated to single- or few-layer sheets, and thus serves as a test bed for developing probes of Kitaev phenomena in atomically thin materials and devices. We introduce the Kitaev model and how it is realized in $\alpha$-RuCl3 and other material candidates; and cover $\alpha$-RuCl3 synthesis and fabrication into van der Waals
heterostructure devices. A key discovery is a work-function-mediated charge transfer that heavily dopes both the $\alpha$-RuCl3 and proximate materials, and can enhance Kitaev interactions by up to 50%. We further discuss a wide range of recent results in electronic transport and optical and tunneling spectroscopies of $\alpha$-RuCl3 devices. The experimental techniques and theoretical insights developed for $\alpha$-RuCl3 establish a framework for discovering and engineering superior two-dimensional Kitaev materials that may ultimately realize elusive
quantum spin liquid phases.
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All authors Claudia Ojeda-Aristizabal, Xiaohu Zheng, Changsong Xu, Zohar Nussinov, Yukitoshi Motome, Arnab Banerjee, Adam W. Tsen, Michael Knap, Rui-Rui Du, Gajadhar Joshi, Andy Mounce, Youngwook Kim, Benjamin M. Hunt, Dmitry Shcherbakov, Boyi Zhou, Ran Jing, Mengkun Liu, Hui Zhao, Bolin Liao, Martin Claassen, Onur Erten, Yong P. Chen, Erik A. Henriksen
Materials Science · Cross-listed from physics.optics
In-Situ Growth of Halide Perovskite Single Crystals and Thin Films on Optical Fiber End Facets
Yang Yu, Kanak Kanti Bhowmik, Ruan Li et al. (+4 more)
Halide perovskites exhibit significant advantages for active optical components such as light emitting diodes,
solar cells and photodetectors due to their excellent optoelectronic properties. Their nonlinear optical effects and other characteristics also make them suitable for integration into waveguide components, such as optical fibers, for applications like optical modulation. Although some efforts have been made to integrate perovskite nanomaterials with optical fibers, technological challenges have hindered reliable in-situ preparation methods. Herein, we propose an area-selective wetting strategy for optical fibers, which utilizes hydrophobic sidewalls and hydrophilic end facets to reliably hold small precursor droplets. By introducing a space confinement strategy to suppress the kinetics of solvent evaporation, Methylammonium lead bromide (MAPbBr3) perovskite single
crystals were successfully grown in-situ on the fiber end facet. The versatility of this in-situ growth method for single
crystals on fiber end facets of various sizes has also been verified. In a separate approach, the controllable in-situ preparation of CsPbBr3 polycrystalline thin films was achieved through
vacuum-assisted rapid crystallization. Our strategy provides a controllable platform for the integration of perovskite materials and optical fibers, enabling further development in optical applications.
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All authors Yang Yu, Kanak Kanti Bhowmik, Ruan Li, Kexin Li, Lin Zhu, Hai Xiao, Lianfeng Zhao
Materials Science
First Principles study of Photocatalytic Water Splitting in BO Monolayer: Effect of Strain and Surface Functionalization
Soumendra Kumar Das, Smruti Ranjan Parida, Prasanjit Samal et al. (+2 more)
Light element based two dimensional (2D) materials are promising photocatalysts for hydrogen production via water splitting. Boron
oxide (BO) is a recently synthesized 2D monolayer which has yet to be thoroughly explored for its potential applications. In this article, using first principles calculations, we report, for the first time, the visible-light photocatalytic activity of a BO monolayer for water splitting under mechanical strain and surface modification with single- and double-atom decorations (C, N, Si, Ge, P, As). The pristine BO monolayer exhibits an indirect band gap of 3.8 eV with band edges spanning the water redox potentials, but its optical absorption lies in the UV region (~ 4.5 eV). Strain engineering tunes the band gap and band
alignment with a minimal shifting in the optical absorption (~0.5 eV). Single atom decoration produces a metallic state for elements like N, P, As, and an insulating state for single C, Si, Ge with a partial shifting in optical absorption. In contrast, double atom decoration produces substantial band gap reduction, improved band
alignment, a pronounced red-shift in optical absorption into the visible range (1.6 to 3.2 eV) thus satisfying the criteria for water splitting. The stability of all the adsorbed configurations was confirmed by negative formation energy and ab-initio molecular dynamics simulations. These findings suggest BO monolayer functionalization can improve photocatalytic efficiency, providing hydrogen generation insights.
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All authors Soumendra Kumar Das, Smruti Ranjan Parida, Prasanjit Samal, Brahmananda Chakraborty, Sridhar Sahu
Materials Science
Local indirect magnetoelectric coupling at twin walls in CaMnO$_3$
Ida C. Skogvoll, Benjamin A. D. Williamson and Sverre M. Selbach
Ferroelastic twin walls in centrosymmetric perovskites can host emergent polar and
magnetic properties forbidden in the bulk. We use density functional theory calculations to study the geometry and
magnetic properties of ferroelastic domain walls in orthorhombic CaMnO$_3$, which belongs to the most common perovskite space group, $Pnma$. At the wall, the inherent inversion
symmetry-breaking induces local polar distortions dependent on the wall geometry, which couple to the
magnetic order through the octahedral distortions. Noncollinear calculations reveal enhanced out-of-plane
magnetic moments on the Mn atoms and a local, finite magnetization confined to the wall. Strain fields across twin walls thus give rise to coexistence of polarization and magnetization as well as magnetoelectric response that is absent and
symmetry-forbidden in bulk CaMnO$_3$. We propose that magnetoelectric coupling and coexisting polarization and magnetization can emerge at twin walls in bulk centrosymmetric antiferromagnets.
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Materials Science · Cross-listed from cond-mat.supr-con
Pressure-induced superconductivity in LaP2 with graphenelike phosphorus layer
Mingxin Zhang, Cuiying Pei, Bangshuai Zhu et al. (+3 more)
Materials with
graphene-like layers attract tremendous
attention due to their electronic structures and superconducting properties. In this study, we synthesized LaP2 polycrystalline and observed a superconducting transition around 30 GPa. The critical temperature Tc increases monotonically with pressure, which is nearing saturation and reaches 7.8 K at 78 GPa. The synchrotron X-ray diffraction experiments confirm the superconducting transition originates from a structure transition to the P6/mmm phase under high pressure, suggesting the observation of
graphene-like phosphorus layers in transition metal phosphides. By first-principles calculations, we provide more evidence for the stability of the
graphene-like phosphorus layers in LaP2. Our findings are helpful for the understanding of the LaP2 phase diagram under high pressure, and could shed light on the research of unique structures in transition metal phosphides under high pressure.
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All authors Mingxin Zhang, Cuiying Pei, Bangshuai Zhu, Qi Wang, Juefei Wu, Yanpeng Qi
Materials Science · Cross-listed from math.AP
Half-plane Green`s function for anti-plane elastic 1D hexagonal QCs
Tsviatko V. Rangelov, George D. Manolis and Petia S. Dineva
This paper presents an analytical derivation of a frequency-dependent fundamental solution plus a Green's function for the uni-dimensional, hexagonal quasicrystal sheet subjected to elastic waves under anti-plane strain conditions. Furthermore, closed-form solutions for the free-fields developing in this sheet for propagating shear waves are also obtained. The analysis presented here provides a foundation for understanding quasicrystal dynamic behavior and for advancing relevant computational methods.
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Materials Science · Cross-listed from cond-mat.mes-hall
Topologically nontrivial flat bands and quantum Hall crossovers in square-octagon lattice materials
Amrita Mukherjee, Rahul Verma, Pritesh Srivastava et al. (+1 more)
Coexistence of nontrivial
topology and flat electronic bands provides a fertile platform for correlated
quantum states. The square-octagon
lattice hosts Dirac nodes and flat bands at half-filling, yet the effects of intrinsic
spin-orbit coupling (SOC) and staggered
magnetic flux on its electronic and topological properties remain largely unexplored. Here, using tight-binding models incorporating SOC and staggered
magnetic flux, we uncover a rich topological phase diagram in this
lattice, comprising a
quantum spin Hall phase with
spin Chern number $C_s=1$, crossovers to
quantum anomalous
Hall phases with $C=1$ and $C=2$, and higher-order topological
insulator phases with quantized quadrupolar corner charges. The initially dispersionless flat bands evolve into quasi-flat topological bands with nearly uniform
quantum geometry and large flatness ratios, making them promising candidates for fractional Chern
insulator states. We further identify realistic materials, including octagraphene, transition-metal dichalcogenides, synthetic $\mathrm{MoSi_2N_4}$, and
magnetic $\alpha$-MnO$_2$, that may realize these tunable topological phases intertwined with flat-band physics, opening new opportunities for correlated topological matter.
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All authors Amrita Mukherjee, Rahul Verma, Pritesh Srivastava, Bahadur Singh
Materials Science
Variationally Consistent Framework for Finite-Strain Microelasticity
Tushar Jogi
Modeling microstructural
evolution at large strains requires mechanical formulations that remain thermodynamically consistent while capturing significant
lattice rotations and transformation-induced stresses. However, most existing finite-strain microelasticity and phase-field approaches apply macroscopic boundary conditions heuristically, preventing proper stress relaxation and violating the Hill-Mandel work equivalence required for homogenization. These limitations can misrepresent stress states and transformation pathways under finite strains. Here a variationally consistent finite-strain microelasticity framework is presented that couples microscopic and macroscopic mechanical
equilibrium through a single energy functional. The resulting Euler-Lagrange conditions, periodic micro-
equilibrium and macroscopic stress balance, are solved using a staggered FFT-Newton
algorithm that combines a spectral fixed-point update for local fields with a Newton step for the homogenized deformation gradient. The formulation accommodates general hyperelastic constitutive laws and arbitrary transformation gradients.
Benchmarks demonstrate accurate recovery of small-strain Eshelby solutions and systematic nonlinear deviations at large dilatations. Applied to deformation twinning in magnesium, the framework reproduces lenticular morphology, stress redistribution, and faster lateral growth consistent with experiments. This approach establishes a rigorous and scalable foundation for finite-strain phase-field simulations of coherent transformations under general stress or mixed boundary conditions.
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Materials Science
Accelerated Prediction of Temperature-Dependent Lattice Thermal Conductivity via Ensembled Machine Learning Models
Piyush Paliwal and Aftab Alam
Lattice thermal conductivity ($\kappa_L$) is a key physical property governing heat transport in solids, with direct relevance to thermoelectrics, thermal barrier coatings, and heat management applications. However, while experimental determination of $\kappa_L$ is challenging, its theoretical calculation via ab initio methods particularly using density functional theory (DFT) is computationally intensive, often more demanding than electronic transport calculations by an order of magnitude. In this work, we present a machine learning (ML) approach to predict $\kappa_L$ with DFT-level accuracy over a wide temperature range (100-1000 K). Among various models trained on DFT-calculated data obtained from literature, the Extra Trees Regressor (ETR) yielded the best performance on log-scaled $\kappa_L$, achieving an average $R^2$ of 0.9994 and a root mean square error (RMSE) of 0.0466 $W\,m^{-1}\,K^{-1}$. The ETR model also generalized well to twelve previously unseen (randomly chosen) low and high $\kappa_L$ compounds with diverse space group
symmetries, reaching an $R^2$ of 0.961 against DFT
benchmarks. Notably, the model excels in predicting $\kappa_L$ for both low- and high-
symmetry compounds, enabling efficient high-throughput screening. We also demonstrate this capability by screening ultralow and ultrahigh $\kappa_L$ candidates among 960 half-Heusler compounds and 60,000 ICSD compounds from the AFLOW database. This result shows reliability of model developed for screening of potential thermoelectric materials. At the end, we have tested model's prediction ability on systems that have experimental $\kappa_L$ available that shows model's ability to search material that has desirable experimental $\kappa_L$ for thermoelectric applications.
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Materials Science · Cross-listed from physics.atm-clus
Signatures of a bilayer structure in the photoelectron spectrum of B$_{80}^-$
Yi-Sha Chen, Jing-Jing Guo, Peng-Bo Liu et al. (+3 more)
Recent photoelectron spectroscopy of B$_{80}^-$ was interpreted in terms of a fullerene-like cage structure. During our systematic investigation of medium-sized boron clusters, we identified a $D_{3h}$-symmetric
bilayer isomer whose simulated photoelectron spectrum reproduces the principal features of the experimental photoelectron spectrum within 0.04 eV. The
bilayer is energetically competitive with previously proposed structures and remains dynamically stable up to 1400 K according to ab initio molecular dynamics and vibrational analyses. Its electronic structure exhibits a 0.72 eV HOMO-LUMO gap and strong interlayer aromaticity, reflected by a NICS(0) value of $-44.3$ ppm in the interlayer B-B bonding region. These findings reveal a stable
bilayer motif in the B$_{80}$ energy landscape and support its viability as a possible alternative structural assignment for the experimentally observed B$_{80}^-$.
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All authors Yi-Sha Chen, Jing-Jing Guo, Peng-Bo Liu, Hui-Yan Zhao, Jing Wang, Ying Liu
Materials Science · Cross-listed from nlin.CD
Multiphase transport and compositional mixing mechanisms in twin-wire laser directed energy deposition: toward process stability and graded material fabrication
Yi Li, Yuhui Li, Jianzhao Wu et al. (+4 more)
Twin-wire
laser directed energy deposition (TW-LDED) provides a promising route for alloying and fabrication of compositionally graded structures. However, inherent multiparameter coupling in twin-wire systems critically exacerbates both process instabilities and compositional inhomogeneity. This unresolved issue escalates into a fundamental technological bottleneck, as the underlying physical mechanisms remain poorly understood. This study developed a high-fidelity multi-physics and multiphase simulation framework coupled with experimental validation to reveal thermal-fluid behavior and heat-mass transfer mechanisms in TW-LDED using Inconel 718 and SS316L fine wires. Three distinct transition modes were identified: twin-wire melt droplet, twin-wire
liquid bridge, and droplet-bridge mixed transitions, with the twin-wire
liquid bridge regime delivering optimal stability and uniform mixing. Parametric analysis demonstrates that increasing wire feeding speed or decreasing wire initial height promotes stable
liquid bridge formation, while small
laser spots at low feeding speeds induce excessive volumetric energy density and bridge instability. Simulation and single-track experiments confirm that
liquid bridge transitions reduce dimensional fluctuations by 85% while enhancing compositional homogeneity. Conversely, the melt droplet-bridge transition mode creates periodic flow switching and compositional discontinuities along the scan direction. Finally, a 60 mm functionally graded ring was successfully fabricated using optimized parameters, achieving uniform elemental distribution in the transition zone without significant segregation, validating the feasibility of TW-LDED for functionally graded components.
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All authors Yi Li, Yuhui Li, Jianzhao Wu, Luxuan Zhang, Maoyuan Li, Chaochao Wu, Zhenzhong Wang
Materials Science · Cross-listed from physics.comp-ph
Orthogonal Attosecond Control of Solid-State Harmonics by Optical Waveforms and Quantum Geometry Engineering
Zhenjiang Zhao, Zhihua Zheng, Zhiyi Xu et al. (+3 more)
High-harmonic generation (HHG) in two-dimensional materials offers a compelling route toward compact extreme ultraviolet sources and probing electron dynamics on the attosecond scale. However, achieving precise control over the emission and disentangling the complex interplay between intraband and interband
quantum pathways remains a central challenge. Here, we demonstrate through first-principles simulations that HHG in monolayer WS2 can be subjected to precise, complementary control by combining all-optical two-color
laser fields with mechanical strain engineering. This dual-mode strategy provides distinct, orthogonal control over harmonic yield, polarization, and spectral features. We reveal that sculpting the two-color field's relative phase provides a sub-femtosecond switch for the
quantum coherence of electron-hole pairs, thereby optimizing harmonic emission. Crucially, we uncover that tensile strain modulates the total harmonic yield and specifically amplifies the perpendicular harmonic component by nearly a factor of two. This enhancement arises through a dual mechanism - while strain-modified band dispersion enhances the intraband current, a significant reshaping of the Berry
curvature (BC) substantially increases the anomalous velocity contribution to the interband response. This
quantum geometric effect manifests as a robust, monotonic dependence of the harmonic yield on strain and a significant amplification of the perpendicularly polarized harmonics, providing a clear experimental signature for probing
quantum geometric effects. Our findings establish a versatile framework for optimizing solid-state HHG and introduce a powerful all-optical method to map strain and
quantum geometric properties of materials, positioning monolayer WS2 as a model system for exploring attosecond physics at the nexus of bulk and atomic scales.
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All authors Zhenjiang Zhao, Zhihua Zheng, Zhiyi Xu, Xing Ran, Xiaolong Yao, Fangping Ouyang
Materials Science · Cross-listed from cond-mat.mes-hall
Signatures of magnetism in zigzag graphene nanoribbon embedded in h-BN lattice
Chengxin Jiang, Hui Shan Wang, Chen Chen et al. (+18 more)
Zigzag edges of
graphene have long been predicted to exhibit
magnetic electronic state near the
Fermi level, which can cause
spin-related phenomena and offer unique potentials for
graphene-based spintronics. However, the
magnetic conduction channels along these edges have yet been reported experimentally. Here, we report the observation on signatures of magnetism in zigzag
graphene nanoribbons (zGNRs) embedded in hexagonal boron nitride (h-BN). The in-plane bonding with BN can stabilize the edges of zGNRs, and thus enable a direct probing of the intrinsic magnetism. Firstly, the presence of magnetism of a zGNR was confirmed by scanning NV center microscopy. And then, zGNR was fabricated into a transistor with a width of ~9 nm wide and a channel length of sub-50 nm. By performing magneto-transport measurements, Fabry-Pérot interference patterns were observed in the transistor at 4 Kelvin, which indicates a coherent transport through the channel. A large magnetoresistance of ~175 {\Omega}, corresponding to a ratio of ~1.3 %, was observed at the same temperature. More importantly, such magneto-transport signal is highly anisotropic on the
magnetic field direction, and its appearance extends well above room temperature. All these evidences corroborate the existence of robust
magnetic ordering in the edge state of zGNR. The findings on zGNR embedded in h-BN provide an effective platform for the future exploration of
graphene-based spintronic devices.
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All authors Chengxin Jiang, Hui Shan Wang, Chen Chen, Lingxiu Chen, Xiujun Wang, Yibo Wang, Ziqiang Kong, Yuhan Feng, Yixin Liu, Yu Feng, Chenxi Liu, Yu Zhang, Zhipeng Wei, Maosen Guo, Aomei Tong, Gang Mu, Yumeng Yang, Kenji Watanabe, Takashi Taniguchi, Wangzhou Shi, Haomin Wang
Materials Science · Cross-listed from physics.atom-ph
Prospects for a Solid-State Nuclear Clock
Steven M. Girvin and Leo Radzihovsky
Motivated by recent experimental breakthroughs toward a realization of a solid-state Thorium-229
nuclear clock, we review the technology, basic physics motivation, and limitations of the present generation of atomic clocks. We then discuss prospects for a new generation of clocks based on an anomalous low-energy 8.4 eV
nuclear transition in Th-229, with an extremely long lifetime of 641 seconds when doped into CaF
crystals. To realize such solid-state
nuclear clocks one must confront basic
nuclear, AMO, and solid state physics questions. Key challenges are understanding and minimizing the effects of inhomogeneous broadening, associated with strains and electric field gradients due to both the Th dopants and intrinsic
crystal defects.
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Materials Science
Revealing the dynamic responses of Pb under shock loading based on DFT-accuracy machine learning potential
Enze Hou, Xiaoyang Wang and Han Wang
Lead (Pb) is a typical low-melting-point ductile metal and serves as an important model material in the study of dynamic responses. Under shock-wave loading, its dynamic mechanical behavior comprises two key phenomena: plastic deformation and shock induced phase transitions. The underlying mechanisms of these processes are still poorly understood. Revealing these mechanisms remains challenging for experimental approaches. Non-
equilibrium molecular dynamics (NEMD) simulations are an alternative theoretical tool for studying dynamic responses, as they capture atomic-scale mechanisms such as defect
evolution and deformation pathways. However, due to the limited accuracy of empirical interatomic potentials, the reliability of previous NEMD studies is questioned. Using our newly developed machine learning potential for Pb-Sn
alloys, we revisited the microstructure
evolution in response to shock loading under various shock orientations. The results reveal that shock loading along the [001] orientation of Pb exhibits a fast, reversible, and massive phase transition and stacking fault
evolution. The behavior of Pb differs from previous studies by the absence of twinning during plastic deformation. Loading along the [011] orientation leads to slow, irreversible plastic deformation, and a localized FCC-BCC phase transition in the Pitsch orientation relationship. This study provides crucial theoretical insights into the dynamic mechanical response of Pb, offering a theoretical input for understanding the microstructure-performance relationship under extreme conditions.
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Materials Science
XPS Analysis of Surface Chemical Transformations in ZBLAN Glass under Thermal and Vibrational Stimuli
Ayush Subedi, Anthony Torres and Jeff Ganley
ZBLAN glass is highly sensitive to thermal and mechanical stimuli, yet the associated surface chemical changes remain poorly understood. X-Ray Photoelectron Spectroscopy (XPS) measurements were performed on multiple ZBLAN samples representing distinct structural states: fully amorphous, incipiently crystalline, and highly crystalline, produced through thermal treatments at 250C and 350C and vibration-assisted processing at 400C under low (L2) and high (H5) vibration levels. High-resolution F 1s, Zr 3d, Hf 4f, Ba 3d, La 3d, and Na 1s spectra show progressive peak sharpening and intensity enhancement with increasing temperature and vibration, indicating reduced surface disorder and greater local structural ordering. The most pronounced changes occur under high vibration at 400C. No binding-energy shifts were detected, confirming that all elements retain their expected oxidation states and that the observed
evolution reflects structural rather than chemical changes. These results provide direct evidence that thermomechanical input enhances surface ordering in ZBLAN and clarify its role in crystallization behavior relevant to infrared optical applications.
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Materials Science · Cross-listed from cond-mat.supr-con
Enhanced Superconductivity at Quantum-Critical KTaO3 Interfaces
Jieun Kim, Muqing Yu, Ahmed Omran et al. (+6 more)
Superconductivity at
oxide interfaces has intrigued researchers for decades, yet the underlying pairing mechanism remains elusive. Here we demonstrate that proximity to a ferroelectric
quantum critical point dramatically enhances interfacial superconductivity in KTaO3. By precisely tuning KTaO3 to its
quantum critical composition through 0.8% niobium doping, we achieve a near-doubling of the superconducting transition temperature, reaching 2.9 K. Remarkably, a dome-shaped carrier density dependence emerges exclusively at the
quantum critical point, contrasting sharply with the linear scaling observed in undoped interfaces. Our findings establish ferroelectric
quantum criticality as a powerful mechanism for enhancing superconductivity and provide compelling evidence for soft-
phonon-mediated pairing in these systems.
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All authors Jieun Kim, Muqing Yu, Ahmed Omran, Jiangfeng Yang, Ranjani Ramachandran, William O. Nachlas, Patrick Irvin, Jeremy Levy, Chang-Beom Eom