Materials Science
X-ray photo-induced atomic motion in Phase Change Materials and conventional covalent chalcogenide glasses
Irene Festi, Antoine Cornet, Tomoki Fujita et al. (+10 more)
X-ray
Photon Correlation Spectroscopy (XPCS) enables direct access to atomic-scale dynamics in disordered materials, revealing both spontaneous and X-ray-induced relaxation processes. Here, we study two compositionally similar
alloy glasses near their glass transition temperatures: the phase change material (PCM) Ge15Sb85 and the non-PCM
alloy Ge15Te85. Both exhibit X-ray induced atomic motion, yet with markedly different responses. Ge15Sb85 undergoes an immediate transition to a photo-induced yielding state, characterised by stationary dynamics governed solely by the absorbed dose. In contrast, Ge15Te85 shows a progressive slowing-down of the relaxation process, accompanied by a crossover from compressed to stretched exponential decay in the density autocorrelation functions. This behaviour is consistent with the emergence of
liquid-like collective motion as supported by de Gennes narrowing in the wave-vector dependence of the dynamics at length scales comparable with the first sharp diffraction peak. Unlike Ge15Sb85, this
alloy does not reach a stationary regime within experimental timescales, implying that the yielding transition occurs only after thousands of seconds with the available dose rate. Its response is also temperature dependent: at lower temperatures, the dynamics reflects intrinsic stress relaxation processes, whereas at higher temperatures becomes dose-controlled. These findings demonstrate that the dynamical response to X-ray excitation is not determined solely by chemical composition or bonding character, but results from the interplay between irradiation effects and structural relaxation pathways.
Read the full abstract ▾
All authors Irene Festi, Antoine Cornet, Tomoki Fujita, Jens Moesggard, Alberto Ronca, Jie Shen, Michael Sprung, Shuai Wei, Fabian Westermeier, Raphael Escalier, Andrea Piarristeguy, Giacomo Baldi, Beatrice Ruta
Materials Science · Cross-listed from cond-mat.soft
Fluids at an electrostatically active surface: Optimum in interfacial friction and electrohydrodynamic drag
Cecilia Herrero, Lyderic Bocquet and Benoit Coasne
While fluids near a solid surface are at the core of applications in energy storage/conversion, electrochemistry/electrowetting and adsorption/catalysis, their nanoscale behavior remains only partially deciphered. Beyond conventional effects (e.g. adsorption/reaction, interfacial transport, phase transition shifts), recent experimental and theoretical studies on metallic surfaces have unraveled exotic peculiarities such as complex electrostatic screening, unexpected wetting transition, and interfacial
quantum friction. These novel features require developing and embarking new tools to tackle the coupling between charge relaxation in the metal and molecular behavior in the vicinal fluid. Here, using the concept of Virtual Thomas-
Fermi fluids, we employ a molecular simulation approach to investigate interfacial transport of fluid molecules and metal charge carriers at their interface–including the underlying electrostatically-driven dynamic friction and the coupling between charge current/hydrodynamic flow (the so-called electrohydrodynamic drag). While conventional numerical techniques consider either insulating materials or metallic materials described as polarizable, non-conducting media, our atom-scale strategy provides an effective yet realistic description of the solid excitation spectrum–including charge relaxation modes and conductivity. By applying this approach to water near metallic surfaces of various electrostatic screening lengths, we unveil a non-monotonous dependence of the fluid/solid friction on the
metallicity with a maximum occurring as the charge dynamic structure factors of the solid and fluid strongly overlap. Moreover, we report a direct observation of the electrohydrodynamic drag which arises from the momentum transfer between the solid and
liquid through dynamic electrostatic interactions and the underlying interfacial friction.
Read the full abstract ▾
Materials Science
Polymer-Iron Oxide Hybrid Films for Controlling Electrokinetic Properties
Austin Dick, Xiao Tong, Kim Kisslinger et al. (+2 more)
Electrokinetic phenomena at
polymer-water interfaces are central to technologies for water purification, ion separations, and energy conversion, yet the ability to systematically control
polymer surface charge and associated electrokinetic processes remains limited. Here, we demonstrate a simple
liquid-phase infiltration (LPI) method to synthesize
polymer-metal
oxide hybrid films with controllable interfacial properties. Hydroxy-terminated poly(2-vinylpyridine) (P2VP-OH) brushes grafted to silicon substrates were infiltrated with iron nitrate from ethanolic solution, followed by low-temperature thermal treatment to convert the infiltrated precursor into iron
oxide. Spectroscopic ellipsometry, X-ray photoelectron spectroscopy, and thermogravimetric analysis confirmed
oxide incorporation and hybrid film formation without
polymer degradation. Electrokinetic flow characterization reveals that the hybrid films acquire the electrokinetic properties of the infiltrated
oxide, with concentration-dependent streaming potentials and surface conductivities closely matching those of pure iron
oxide films. These results establish metal
oxide infiltration as a scalable and low-cost strategy for controlling interfacial charge in
polymer surfaces. The approach introduces new materials and design parameters for tailoring ion selectivity, transport, and energy conversion, with broad implications for the development of advanced membranes, electrokinetic harvesting devices, and
polymer-supported
oxide electrodes.
Read the full abstract ▾
All authors Austin Dick, Xiao Tong, Kim Kisslinger, Carlos E. Colosqui, Gregory Doerk
Materials Science · Cross-listed from cond-mat.str-el
Fermi Sets: Universal and interpretable neural architectures for fermions
Liang Fu
We introduce
Fermi Sets, a universal and physically interpretable neural architecture for fermionic many-body wavefunctions. Building on a “parity-graded” representation [1], we prove that any continuous fermionic wavefunction on a compact domain can be approximated to arbitrary accuracy by a linear combination of K antisymmetric basis functions–such as pairwise products or Slater determinants–multiplied by symmetric functions. A key result is that the number of required bases is provably small: K=1 suffices in one-dimensional continua (and on
lattices in any dimension), K=2 suffices in two dimensions, and in higher dimensions K grows at most linearly with particle number. The antisymmetric bases can be learned by small neural networks, while the symmetric factors are implemented by permutation-invariant networks whose width scales only linearly with particle number. Thus,
Fermi Sets achieve universal approximation of fermionic wavefunctions with minimal overhead while retaining clear physical interpretability. As a numerical illustration, a single
Fermi Sets model applied to metallic solid hydrogen in three dimensions, trained simultaneously across multiple
nuclear geometries, surpasses all
diffusion Monte Carlo
benchmarks.
Read the full abstract ▾
Materials Science
An altermagnetic materials library in intercalated transition-metal dichalcogenides
Ezra Day-Roberts, Huan Wu, Onur Erten et al. (+1 more)
Altermagnets represent a promising class of
magnetic materials owing to their distinctive
spin-split band structures in the absence of net magnetization. Here, we present a first-principles investigation of altermagnetism in magnetically intercalated transition metal dichalcogenides (TMDs) with the general formula T$_y$MX$_2$ (T= 3$d$-transition metal, M= transition-metal, X=chalcogen, $y$= 1/3 or 1/4). For a TMD host with 2H structure, compounds exhibiting A-type antiferromagnetism are $g$-wave altermagnets by
symmetry. We identify several intercalated TMDs fulfilling the conditions for altermagnetic order to be realized. Several of these candidate materials display
spin-splittings at the
Fermi level as large as 100 meV.
Read the full abstract ▾
All authors Ezra Day-Roberts, Huan Wu, Onur Erten, A. S Botana
Materials Science
Strain effects on the binding and diffusion energies of Au adatoms and CeO2 admolcules on Au, CeO2, MgO and SrTiO3 surfaces
Ahmad Ahmad, Ying-Cheng Chen, Jie Peng et al. (+1 more)
First-principles density functional theory (DFT) calculations were used to study the effects of elastic strains on the binding and
diffusion activation energies of Au adatom and CeO2 admolecule on Au (001), Ce-terminated CeO2 (001), MgO (001), SrO- and TiO2-terminationed SrTiO3 (001) surfaces. In preparation for computing these energies, normal and shear strains within the range 0.15% were applied in the plane of the surface of the supercell prior to placing the adsorbed species on the surface. Our study shows that the dependence of binding energies and
diffusion barriers of adatoms and molecules on the strain varies significantly among surfaces. The strain was found to alter the
symmetry of surface
diffusion pathways causing anisotropy of the
diffusion barriers. This strain-induced anisotropy depends on the orientation of the applied strains relative to the in-plane crystallographic directions of the free surface. The binding and
diffusion activation energies were fit linearly in terms of strain components in the range 0.15% and the extrapolated values compared favorably to DFT computed values up to 0.5%. The scheme presented here for the computation and fitting of the binding and
diffusion energies in terms of strain can be used to inform models of surface
diffusion, clustering and growth of multi-component and multi-phase thin films and investigate the effect of strain on the self-organization in such systems.
Read the full abstract ▾
All authors Ahmad Ahmad, Ying-Cheng Chen, Jie Peng, Anter El-Azab
Materials Science · Cross-listed from cond-mat.mes-hall
Anomalous Collision of Exceptional Points on Nonorientable Manifolds
Weijia Wang, Qicheng Zhang, Kun Zhang et al. (+2 more)
Band degeneracies, ranging from Hermitian Dirac points to non-Hermitian exceptional points (EPs), play a central role in topological phase transitions. Beyond the
topology of individual degeneracies, their mutual interactions yield richer phenomena. A representative example is the anomalous non-annihilating collision of pairwise-created degeneracies, previously believed to occur only in non-Abelian multiband systems. Here, we theoretically reveal and experimentally demonstrate that such an anomalous collision can emerge even in a simple two-band system without non-Abelian nature. In a two-dimensional non-Hermitian
lattice whose Brillouin zone forms a nonorientable Klein bottle, two EPs with opposite topological charges, pairwise created from a hybrid point, merge into a new
vortex point upon re-encounter, instead of annihilating. Remarkably, the hybrid point is a defective degeneracy featuring no eigenenergy braiding, whereas the
vortex point is a non-defective degeneracy yet exhibits nontrivial eigenenergy braiding. This process manifests a non-Hermitian phase transition from a gapped phase to a gapless phase, a scenario that we directly observe in a hybrid-dimensional acoustic
lattice via momentum-resolved band braid and Berry phase measurements. Our findings identify nonorientability as a new arena for engineering band degeneracies and topological phases, and pave the way for experimentally exploring the interplay between exceptional and nonorientable
topology.
Read the full abstract ▾
All authors Weijia Wang, Qicheng Zhang, Kun Zhang, Shuaishuai Tong, Chunyin Qiu
Materials Science
Analysis of the Optical Properties and Electronic Structure of Semiconductors of the Cu2NiXS4 (X = Si, Ge, Sn) Family as New Promising Materials for Optoelectronic Devices
Dilshod Nematov
In this work, the optoelectronic characteristics of kesterites of the Cu2NiXS4 system (X = Si, Ge, Sn) were studied. The electronic properties of the Cu2NiXS4 (X = Si, Ge, Sn) system were studied using first-principles calculations within the framework of density functional theory. For calculations, ab initio codes VASP and Wien2k were used. The high-precision modified Beke-Jones (mBJ) functional and the hybrid HSE06 functional were used to estimate the bandgap, electronic and optical properties. Calculations have shown that when replacing Si with Ge and Sn, the band gap decreases from 2.58 eV to 1.33 eV. Replacing Si with Ge and Sn reduces the overall density of electronic states. In addition, new deep (shallow) states are formed in the band gap of these
crystals, which is confirmed by the behavior of their optical properties. The obtained band gap values are compared with existing experimental measurements, demonstrating good agreement between HSE06 calculations and experimental data. The nature of changes in the dielectric constant, absorption capacity and optical conductivity of these systems depending on the
photon energy has also been studied. The statistical dielectric constant and refractive index of these materials were found. The results will help increase the amount of information about the properties of the materials under study and will allow the use of these compounds in a wider range of optoelectronic devices, in particular, in
solar cells and other devices that use
solar radiation to generate electric current.
Read the full abstract ▾
Materials Science
Molecular Adsorption of H2O on TiO2 and TiO2:Y Surfaces
Dilshod Nematov, Khilmirzo Kholmurodov, Mirzoaziz Husenzoda et al. (+2 more)
In this work, using theoretical calculations within the framework of the density functional theory, taking into account the dispersive VDW interaction, the processes of adsorption and interaction of a water molecule with a TiO2 surface in various configurations are investigated. At the atomic/molecular level, the interactions of a water molecule with a TiO2 surface have been studied for various orientations. The results of calculations within the framework of DFT+ VDW show that the adsorption energies of single water molecules in different initial positions on the substrate surface vary from-0.72 to-0.84 eV, and the most stable adsorbate structure is the TiO2+ H2O system upon adsorption of a molecule of water, parallel to the Y axis, because during the adsorption of H2O parallel to the Y axis, some favorable effects are observed in the band structure of titanium dioxide. On the one hand, the band gap decreases to 2.59 eV, and on the other hand, a new energy state appears in the band gap with an energy contribution of 0.17 eV, when water is physisorbed and interacts with a titanium atom at a distance of 2.12 Å and occupies a perpendicular position relative to the surface.
Read the full abstract ▾
All authors Dilshod Nematov, Khilmirzo Kholmurodov, Mirzoaziz Husenzoda, Andrey Lyubchyk, Amondulloi Burhonzoda
Materials Science
Transverse Photoresistivity from Photothermal Current Deflection in Metal Films
Piyush Sakrikar, Vincent M. Plisson, Cameron Grant et al. (+6 more)
Quantum geometry in centrosymmetric systems has motivated the search for photocurrent responses beyond second order. In particular, electric field-induced nonlinear responses may also enable intrinsic polarization-sensitive optical detectors. Despite numerous efforts, clear methods are still needed to remove experimental artifacts, separating intrinsic from extrinsic effects, and disentangling linear responses from their higher-order counterparts. Here, we provide a systematic study of fabrication and measurement techniques to remove external artifacts in photoelectronic responses. This reveals a previously hidden photothermoelectric response in the transverse photoresistivity of symmetric thin films of simple metals. We identify its origin in thermal gradients producing current deflection and determine the device design and measurement parameters to minimize extrinsic effects that arise in photoinduced electronic responses.
Read the full abstract ▾
All authors Piyush Sakrikar, Vincent M. Plisson, Cameron Grant, Dylan Rosenmerkel, Gabriel Natale, Michael Geiwitz, Ying Ran, Krzysztof Kempa, Kenneth S. Burch
Materials Science
Multi-Fidelity Predictive Model for Shock Response of Energetic Materials Using Conditional U-Net
Brian H. Lee, Chunyu Li, Aidan Pantoya et al. (+3 more)
Mapping microstructure to properties is central to materials science. Perhaps most famously, the
Hall-Petch relationship relates average grain size to strength. More challenging has been deriving relationships for properties that depend on subtle microstructural features and not average properties. One such example is the initiation of energetic materials under dynamical loading, dominated by energy localization on microstructural features such as pores, cracks, and interfaces. We propose a conditional convolutional neural network to predict the shock-induced temperature field as a function of shock strength, for a wide range of microstructures, and obtained via two different simulation methods. The proposed model, denoted MISTnet2, significantly extends prior work that was limited to a single shock strength, model, and type of microstructure. MISTnet2 can contribute to bridging atomistics with coarse-grain simulations and enable first principles predictions of detonation initiation and safety of this class of materials.
Read the full abstract ▾
All authors Brian H. Lee, Chunyu Li, Aidan Pantoya, James P. Larentzos, John K. Brennan, Alejandro Strachan
Materials Science · Cross-listed from cond-mat.str-el
Electronic correlations and topology in Kondo insulator PuB$_6$
K. Gofryk, S. Zhou, N. Poudel et al. (+4 more)
Utilizing a combination of dynamical mean field theory and density functional theory (DMFT/DFT), it has been theoretically proposed that PuB$_6$ is a strongly correlated topological
insulator characterized by nontrivial $\mathbf{Z}_{2}$ topological invariants and metallic surface states (X. Deng et al., Phys. Rev. Lett. 111, 176404 (2013)). Here, we demonstrate through low-temperature magneto-transport measurements and first-principles calculations that PuB$6$ exhibits characteristics of a topological Kondo insulating state. These features include a transition in electrical resistivity from high-temperature, thermally activated behavior with a narrow gap at the
Fermi level ($\Delta{\rho} \sim$ 20 meV) to a distinctive low-temperature plateau, as well as a surface-to-volume dependence of electrical resistivity at low temperatures. The topological nature of PuB$_6$ is further supported by the theoretical calculations, which show that GGA+$U$ is capable of capturing electronic, topological, and
lattice properties of PuB$_6$ with much lower computational cost than DMFT.
Read the full abstract ▾
All authors K. Gofryk, S. Zhou, N. Poudel, N. Dice, D. Murray, T. Pavlov, C. Marianetti
Materials Science
Morphology dependent decomposition and pore evolution during oxidation of Cr$_2$AlC coatings revealed by correlative tomography
Devi Janani Ramesh, Sameer Aman Salman and Jochen M. Schneider
Quantitative 3D characterization of materials degradation in oxidizing environments remains limited. Here, we apply a correlative
tomography-based mass balance framework to Cr$_2$AlC, a coating candidate for accident tolerant
nuclear fuel claddings and turbine blades, and show that decomposition and pore
evolution during oxidation, quantified by integrating volumetric, structural and compositional data, are strongly governed by grain morphology. The oxidation of sputtered Cr$_2$AlC coatings with equiaxed and columnar grain morphologies was analyzed. While Cr$_7$C$_3$ formed in both coating morphologies, pores formed exclusively in columnar coatings. The expected Cr$_7$C$_3$ volume was estimated by mass-balance calculations assuming that Al-deintercalation enables
oxide scale and Al-O-C-N precipitate formation, leading to complete transformation of the Al-deintercalated Cr$_2$AlC into Cr$_7$C$_3$. In equiaxed coatings, the predicted carbide volume agreed with
tomography within 3 $\pm$ 3 %, confirming Al-deintercalation-driven Cr$_7$C$_3$ formation. Despite the smaller molar volume of Cr$_7$C$_3$ relative to Cr$_2$AlC, absence of pores imply that transformation shrinkage is likely accommodated by coating thickness reduction. In columnar coatings, the predicted Cr$_7$C$_3$ volume exceeds the measured value by 22 $\pm$ 4 %, and the pore volume expected from transformation shrinkage alone is 13-16 % lower than measured, indicating partial Al deintercalation and clustering of pre-existing defects. This combined methodology provides a general route to quantitatively resolve degradation mechanisms.
Read the full abstract ▾
Materials Science · Cross-listed from quant-ph
Quantum Extreme Reservoir Computing for Phase Classification of Polymer Alloy Microstructures
Arisa Ikeda, Akitada Sakurai, Kae Nemoto et al. (+1 more)
Quantum machine learning (QML) is expected to offer new opportunities to process high-dimensional data efficiently by exploiting the exponentially large state space of
quantum systems. In this work, we apply
quantum extreme reservoir computing (QERC) to the classification of microstructure images of
polymer alloys generated using self-consistent field theory (SCFT). While previous QML efforts have primarily focused on
benchmark datasets such as MNIST, our work demonstrates the applicability of QERC to engineering data with direct materials relevance. Through numerical experiments, we examine the influence of key computational parameters-including the number of
qubits, sampling cost (the number of measurement shots), and reservoir configuration-on classification performance. The resulting phase classifications are depicted as phase diagrams that illustrate the phase transitions in
polymer morphology, establishing an understandable connection between
quantum model outputs and material behavior. These results illustrate QERC performance on realistic materials
datasets and suggest practical guidelines for
quantum encoder design and model generalization. This work establishes a foundation for integrating
quantum learning techniques into materials informatics.
Read the full abstract ▾
All authors Arisa Ikeda, Akitada Sakurai, Kae Nemoto, Mayu Muramatsu
Materials Science
Investigating the impact of copper-PEDOT:PSS matrix towards non-enzymatic electrochemical creatinine detection
Chirantan Das, Subhrajit Sikdar, Shreyas K. Vasantham et al. (+6 more)
Electrochemical creatinine sensors offer great promise towards rapid, reagent-free and point-of-care (POC) kidney-function monitoring. However, challenges related to analyte binding, data reproducibility, sensitivity, fouling and device degradation deter its widespread implementation. Here, we show how a carbon electrode modified with a combination of poly(3,4-ethylene dioxythiophene): poly(styrene sulfonate) (PEDOT:PSS) and copper nanoparticles (CuNPs) can rapidly and accurately detect creatinine (CT) in artificial urine media employing electrochemical techniques. Applying redox potential sweeps (vs Ag/AgCl) using copper sulfate (CuSO4) solution on such sensor facilitates the CuNP
embedding process inside the conjugated
polymer matrix which has been further validated by supporting techniques. We predicted and validated the formation and contribution of two Cu-CT coordination complexes corresponding to Cu(I) and Cu(II) states, which are responsible for CT detection. The fabricated CT sensor exhibits high selectivity against major artificial urine interferents and is stable for a month showing minimal degradation (0.53%) in peak current value. Such sensors can be utilized to detect and monitor different stages of renal failure in real-time patient samples.
Read the full abstract ▾
All authors Chirantan Das, Subhrajit Sikdar, Shreyas K. Vasantham, Piotr Pięta, Marcin Strawski, Marcin S. Filipiak, Paweł Borowicz, Yurii Promovych, Piotr Garstecki
Materials Science
Dynamic stress response kernels for dislocations and cracks: unified anisotropic Lagrangian formulation
Yves-Patrick Pellegrini, Marc Josien and Martin Chassard
Elastodynamic cohesive-zone models for defects such as cracks or dislocations (such as the Geubelle-Rice model for cracks, or the Dynamic Peierls Equation for flat-core dislocations), feature the same stress-response convolution kernel in space and time. It accounts for in-plane elastic wave propagation, while its associated instantaneous radiative term accounts for radiative losses in the surrounding medium. These objects are well-known for isotropic elasticity, with their space-time representations involving generalized functions. For anisotropic elasticity they were unknown. The paper presents a derivation using the Stroh formalism. Their
Fourier representation rests exclusively on the so-called prelogarithmic Lagrangian factor $L(v)$, while their space-time form involves its derivative $p(v)=L'(v)$, the prelogarithmic impulsion function. A straightforward consequence is the reformulation of the stress in the Weertman model of steadily-moving dislocations in terms of $L(v)$. Special care being paid to the causality constraint, the theory covers indifferently subsonic, intersonic and supersonic regimes of motion. The theory proposed is suitable to phase-field-type
Fourier-based numerical codes for planar systems of defects in anisotropic elastodynamics.
Read the full abstract ▾
Materials Science
Competing phases and domain structures of ferroelectric perovskites: the benefit of epitaxial (110) growth
Lan-Tien Hsu, Takeshi Nishimatsu and Anna Grünebohm
Strain and domain engineering offer powerful routes to control phase and domain stability in ferroelectric thin films. While most studies have focused on (100)-oriented growth, the impact of lower-
symmetry orientations remains underexplored. We address this gap in knowledge with first-principles based molecular dynamics simulation for the example of prototypical ferroelectric perovskites under (110) strain. Epitaxial (110) strains may indeed outperform the widely studied (100) orientation, as even modest strain values stabilize a diverse set of metastable nanoscale states with potential high functional tunability. In this regime, the films exhibit multidomain configurations with domain wall normal oriented along the clamped in-plane or the relaxed out-of-plane directions and heterophases in BaTiO$_3$ and KNbO$_3$. Besides, complex superdomain patterns and antiferroelectric-like domains are observed in PbTiO$_3$. These metastable nanoscale configurations may allow for large reversible responses.
Read the full abstract ▾
Materials Science
Predictive Design of Defect States in Hexagonal Boron Nitride for Telecommunication-Band Quantum Emission
Kerem Anar, Berna Akgenc Hanedar, Roya Kavkhani et al. (+1 more)
Defect-based single-
photon emitters (SPEs) in hexagonal boron nitride (h-BN) are promising platforms for integrated
quantum photonics; however, the absence of identified emitters operating at telecom wavelengths remains a critical limitation for fiber-based
quantum communication. Here, we investigate previously unexplored carbon- and silicon-based point defects in monolayer h-BN as SPE candidates using hybrid density functional theory, constrained excited-state relaxations, and a generating-function approach to photoluminescence. We compute zero-
phonon-line (ZPL) energies, radiative lifetimes, Huang-Rhys (HR) factors, and photoluminescence lineshapes to screen optical performance. All defects are thermodynamically stable with negative formation energies, and five candidates exhibit moderate electron-
phonon coupling (HR < 5), indicating narrow emission linewidths. These emitters span a broad spectral range from the visible to the telecom regime, including near-infrared C-based centers and, most notably, the Si2BVN defect, which is identified as the first point defect in monolayer h-BN predicted to support single-
photon emission in the telecom C band (1554 nm). Vacancy-containing complexes possess
spin-1/2 ground states, enabling
spin-
photon interfaces compatible with integrated photonic and cavity-based platforms. The combined analysis of ZPL energies, electron-
phonon coupling, and radiative lifetimes provides concrete targets for experimental realization of
spin-active single-
photon emitters in h-BN from the visible to telecom wavelengths.
Read the full abstract ▾
All authors Kerem Anar, Berna Akgenc Hanedar, Roya Kavkhani, Mehmet Cengiz Onbasli
Materials Science
FIR transmission and resistively detected cyclotron resonances in InSb
M.E. Bal, N. Deßmann, K. Saeedi et al. (+1 more)
We have developed an experimental setup to simultaneously acquire magneto-transmission spectra and measure the photoconductive response. The low-temperature ($T$=4.2 K) magneto-transmission data for weakly doped InSb in the frequency range 3-15 THz and
magnetic fields up to 25 T, shows that the AC conductivity is governed by the classical Drude response. Moreover, the resulting light-induced voltage in this system, consisting of thermoelectric and resistive contributions, both contain features that are related to cyclotron resonances. The frequency dependence of this resonance is in good agreement with $\mathbf{k\cdot p}$ perturbation theory and corresponds to transitions between the first and second Landau level with
spin-up electrons. The obtained effective mass $m^{*}(B=0)=0.014m_{e}$, is in line with the value extracted from magneto-transmission experiments. Additionally, we can observe evidence of a fluence-dependent metal-
insulator transition in the thermoelectric signal, which suggest that the electronic system becomes less sensitive to the light at higher frequencies.
Read the full abstract ▾
All authors M.E. Bal, N. Deßmann, K. Saeedi, U. Zeitler
Materials Science
Photo-induced non-thermal lattice disorder in aluminium thin-film
Fernando Rodriguez Diaz and Kasra Amini
We investigate the ultrafast dynamics of photo-induced non-thermal
lattice disorder in a polycrystalline aluminium thin film to elucidate transient short- and long-range
lattice distortions, their thermalization and electron-
phonon coupling timescales. Using a high-repetition-rate 95-keV ultrafast electron diffraction setup (UED), we measured the transient dynamics for the differential scattering signal in a momentum transfer, $q$, range longer than in conventional keV UED setups. Analysis of ten Bragg and six diffuse scattering revealed a
prompt increase in the mean-square displacement (MSD), indicating rapid energy transfer from the excited electronic system to the
lattice. The subsequent relaxation dynamics of the elastic scattering intensities exhibit a pronounced dependence on diffraction order. Lower-order reflections relax more rapidly, whereas higher-order reflections show significantly slower relaxation or near-plateau behaviour, indicating that
lattice equilibration proceeds on multiple $q$-dependent timescales. Exponential fits to the MSD dynamics reveal oscillatory residuals, indicative of coherent non-thermal
lattice motion. Power spectral density analysis of these residuals uncovers coherent
lattice oscillations with a fundamental frequency of $\omega_0 = 0.192$ THz, corresponding to the acoustic breathing (A$_{1g}$) mode of aluminium. Higher frequency components are also observed, consistent with coherent
phonon oscillations originating from a single zero-wavevector mode populated by multiple coherent
phonons. While individual
phonon branches are not directly resolved, the observed dependence on the
lattice plane of the relaxation behaviour and oscillatory signatures are consistent with a mode-selective
lattice response and non-thermal energy redistribution as described by non-thermal
lattice models.
Read the full abstract ▾
Materials Science · Cross-listed from physics.atm-clus
Quantum Study of Dispersion-Corrected Electronic and Optical Properties of syn- and anti- B18H22 Clusters with/without Sulfur Doping for Tunable Optoelectronics
Fakher Abbas, Nabil Joudieh, Habib Abboud et al. (+1 more)
This study presents a detailed
quantum chemical investigation of the electronic and excited-state properties of syn- and anti-isomers of the borane cluster B18H22 and their sulfur-doped derivatives. Using the PB86/def2-SVP level of theory with dispersion corrections, the research examines how sulfur substitution and non-covalent interactions influence cluster stability, electronic structure, spectra, and optoelectronic potential. Comparative analysis of the syn- and anti-isomers reveals the impact of molecular conformation on frontier molecular orbitals and related energetic and photophysical properties. Sulfur doping is shown to enhance charge delocalization, stabilize excited states, and improve thermal stability, which form key factors for tunable
laser applications. The inclusion of advanced dispersion correction methods proves essential for accurately capturing many-body interactions that govern electronic behavior. By elucidating the interplay between structural features, substitution patterns, and computational modeling, the work provides valuable insights into structure-property relationships critical for designing borane-based materials with tailored optoelectronic and thermal characteristics. In addition to doping and dispersion effects, functionals' effects were examined through comparison amidst various ones with different asymptotic exchange on excitation and gap energies. In summary, the computational methodology combined good DFT/Basis/dispersion set to accurately predict geometries, IR/UV spectra, NMR chemical shifts, dipole moments, polarizability and excited-state properties, thereby offering a comprehensive theoretical understanding of syn-, anti- isomers of B18H22 and its sulfur doped variants.
Read the full abstract ▾
All authors Fakher Abbas, Nabil Joudieh, Habib Abboud, Nidal Chamoun
Materials Science
Charge disproportionation as a possible mechanism towards polar antiferromagnetic metal in molecular orbital crystal
Yang Shen, Shuai Qu, Gang Li et al. (+2 more)
Polar
antiferromagnetic metals have recently garnered increasing interests due to their combined traits of both ferromagnets and antiferromagnets for spintronic applications. However, the inherently incompatible nature of antiferromagnet,
metallicity and polarity pose a significant challenge. We propose that charge disproportionation can lead to this novel state in negative charge transfer gap regime in molecular orbital
crystal by molecular orbital analyses of first-principles DFT+$U$ electronic band structure for representative Ruddlesden-Popper
bilayer perovskite
oxides Sr$_3$Co$_2$O$_7$, corroborated by Density
Matrix Renormalization Group calculation. Due to the negative charge transfer nature of Co$^{4+}$ and imposed by strong interlayer coupling, localized molecular orbitals stemming from the hybridization of Co $d_{z^2}$ and $d_{xz/yz}$ orbitals through the apical oxygen $p$ orbitals are preferably emergent within each
bilayer unit, which develop
antiferromagnetic ordering by invoking Hubbard repulsion. Charge disproportionation driven by Hund's physics, makes an occupation imbalance with broken inversion
symmetry in the remaining $d_{xy}$ and $d_{x^2-y^2}$ orbitals from distinct Co atoms within the
bilayer unit, resulting in the polar
metallicity. Meanwhile, this charge disproportionation scenario allows consequent conducting carriers to couple with interlayer local
spins via Hund's coupling, giving rise to in-plane double-exchange ferromagnetism. Our molecular orbital formulation further provides a guide towards an effective
Hamiltonian for modelling the unconventional synergy of
metallicity, polarity and antiferromagnetism in Sr$_3$Co$_2$O$_7$, which may be a unified framework widely applicable to double-layer Ruddlesden-Popper perovskite
oxides.
Read the full abstract ▾
All authors Yang Shen, Shuai Qu, Gang Li, Pu Yu, Guang-Ming Zhang
Materials Science · Cross-listed from physics.chem-ph
Theoretical Study of C36 and O@C36 Fullerene Isomers with (C1, C2, Cs, D2, D3h) symmetries: Geometry Optimization, Electrical Properties and Spectroscopic Analysis
Fouad Aljneed, Nabil Joudieh, Issam Aljghami et al. (+2 more)
In this study, we conducted a theoretical analysis of specific C36 and O@C36 Fullerene isomers, namely those with (D3h, C1, Cs, C2, D2)
symmetries, in the gaseous phase using the DFT method at B3LYP/6-31G* level. We studied geometry optimizations, relative stability, atomization energies,
Fermi energy, energy gap, electronic properties, electric dipole moment, polarizabilities, and thermodynamic analysis, along with IR and NMR spectra. Consistently, our findings revealed distinct properties and characteristics among different C36 fullerene isomers. The energetic order of C36 fullerene isomers was established as C36-D3h < C36-C1 < C36-Cs < C36-C2 < C36-D2, a trend unaffected by the encapsulation of oxygen. Notably, the D2 isomer displayed the smallest energy gap, indicating higher electrical conductivity compared to other isomers, while it exhibited the largest gap after encapsulation. Furthermore, we observed that the C1 (D2) isomer exhibited the largest (smallest) Electric dipole moment among the studied C36 isomers, whereas the C2 (D2) isomer demonstrated the largest Electric dipole moment among the O@C36 isomers studied. The encapsulation of oxygen in C36 isomers influenced their properties, including alterations in electronic properties, IR, and NMR chemical shifts. A detailed analysis of BSSE corrections showed the tininess of their impact on the analyzed observables, such that uncorrected and BSSE-corrected calculations led to nearly identical results, confirming the robustness and reliability of the B3LYP/6-31G* approach used in this work and, eventually, in other large and rigid fullerenes systems.
Read the full abstract ▾
All authors Fouad Aljneed, Nabil Joudieh, Issam Aljghami, Khansaa Hussein, Nidal Chamoun
Materials Science
Determination of bonding radii from small-molecule crystal structures
Eglė Šidlauskaitė, Andrius Merkys, Antanas Vaitkus et al. (+2 more)
X-ray crystallography rarely captures chemical bonding between atoms of a structure in question. Most of the time distance-based heuristics are applied to establish the pairs of bonded atoms. One class of such heuristics depends on a set of bonding radii that estimate the idealised size of each chemical element in a bond. This publication describes an unsupervised workflow for deriving a bonding radii set from
crystal structure data in the Crystallography Open Database.
Read the full abstract ▾
All authors Eglė Šidlauskaitė, Andrius Merkys, Antanas Vaitkus, Algirdas Grybauskas, Saulius Gražulis
Materials Science · Cross-listed from physics.plasm-ph
Photonic Interactions with Semiconducting Barrier Discharges
Ayah Soundous Taihi and David Z. Pai
Semiconducting Barrier Discharges (SeBDs) generate uniform ionization waves in air at atmospheric pressure. In this work, we investigate how externally applied irradiation synchronized with the discharge can mimic photoconductive-type coupling between the
plasma and the
semiconductor surface. By illuminating the Si-SiO$_2$ interface with nanosecond pulsed irradiation at wavelengths from 532 nm to 1064 nm, and using fast imaging, optical emission spectroscopy, and current-voltage measurements, we demonstrate that the photoexcitation of charge carriers in silicon enhances the
plasma emission and increases the reduced electric field, with no detectable change in the electrical energy. The magnitude and thresholds of these responses depend on wavelength. By comparing the SeBD to a MOS photodetector, this behaviour can be explained by the absorption length. This length determines whether carriers are photogenerated inside the depletion region at the SiO$_2$-Si interface, where they are efficiently separated and undergo impact-ionization amplification, or deeper in the silicon bulk where carrier separation is weaker and free-carrier absorption diminishes the
quantum efficiency. These results focus on the microscopic processes governing the
plasma-
semiconductor coupling and demonstrate how the optoelectronic properties of silicon can influence surface ionization waves.
Read the full abstract ▾
Materials Science
Score-based diffusion models for accurate crystal-structure inpainting and reconstruction of hydrogen positions
Timo Reents, Arianna Cantarella, Marnik Bercx et al. (+2 more)
Generative AI models, such as score-based
diffusion models, have recently advanced the field of computational materials science by enabling the generation of new materials with desired properties. In addition, these models could also be leveraged to reconstruct
crystal structures for which partial information is available. One relevant example is the reliable determination of atomic positions occupied by hydrogen atoms in hydrogen-containing crystalline materials. While crucial to the analysis and prediction of many materials properties, the identification of hydrogen positions can however be difficult and expensive, as it is challenging in X-ray scattering experiments and often requires dedicated
neutron scattering measurements. As a consequence, inorganic crystallographic databases frequently report
lattice structures where hydrogen atoms have been either omitted or inserted with heuristics or by chemical intuition. Here, we combine
diffusion models from the field of materials science with techniques originally developed in computer
vision for image inpainting. We present how this knowledge transfer across domains enables a much faster and more accurate completion of host structures, compared to unconditioned
diffusion models or previous approaches solely based on DFT. Overall, our approach exceeds a success rate of 97% in terms of finding a structural match or predicting a more stable configuration than the initial reference, when starting both from structures that were already relaxed with DFT, or directly from the experimentally determined host structures.
Read the full abstract ▾
All authors Timo Reents, Arianna Cantarella, Marnik Bercx, Pietro Bonfà, Giovanni Pizzi
Materials Science
Van der Waals CrSBr alloys with tunable magnetic and optical properties
Shalini Badola, Amit Pawbake, Bing Wu et al. (+4 more)
Van der Waals magnets are attracting a lot of
attention for their potential integration in spintronic and magnonic technologies. CrSBr is an A-type antiferromagnet that shows a coupling between its electronic band structure and
magnetic properties. This property is appealing for applications and it also offers the possibility to investigate
magnetic ground states and GHz
magnons using visible optics techniques. Using Raman scattering and (magneto)-optical experiments, we describe the
magnetic and optical properties of
alloys of CrSBr$_{(1-x)}$Cl$_x$ with $x<0.46$. Similar to CrSBr, these
alloys are direct band gap
semiconductors with a coupling of their electronic and
magnetic properties.
Exciton energies evolve weakly with composition and we describe the large changes in the saturation
magnetic fields and their implications on the
magnetic properties. We show that both the interlayer
magnetic exchange and electronic interactions are modified by the halogen mixing, offering the possibility to tune
magnon energies with
alloy composition.
Read the full abstract ▾
All authors Shalini Badola, Amit Pawbake, Bing Wu, Aljosha Söll, Zdenek Sofer, Rolf Heid, Clement Faugeras
Materials Science · Cross-listed from cond-mat.str-el
Emergent Spin Supersolids in Frustrated Quantum Materials
Yixuan Huang, Seiji Yunoki and Sadamichi Maekawa
Recent years have witnessed the emergence of
spin supersolids in frustrated
quantum magnets, establishing a material-based platform for supersolidity beyond its original context in solid helium. A
spin supersolid is characterized by the coexistence of longitudinal
spin order that breaks
lattice translational
symmetry and transverse
spin order associated with the spontaneous breaking of the
spin U(1)
symmetry. Extensive experimental investigations, together with advanced numerical studies, have now revealed a coherent and internally consistent picture of these phases, substantially deepening our understanding of supersolidity in
quantum magnetic materials. Beyond their fundamental interest as exotic
quantum states, potential applications in highly efficient demagnetization cooling have been supported by a
giant magnetocaloric effect observed in candidate materials. Moreover, the possible dissipationless
spin supercurrents could open promising perspectives for
spin transport and spintronic applications. This review summarizes recent progress on emergent
spin supersolids in frustrated triangular-
lattice quantum antiferromagnets, surveys experimental evidence from thermodynamic and spectroscopic measurements, and compares these results with theoretical studies of minimal models addressing global phase diagrams, ground state properties, and collective excitations. In addition, this review discusses characteristic
spin-transport phenomena and outlines future directions for exploring
spin supersolids as functional
quantum materials.
Read the full abstract ▾
Materials Science · Cross-listed from physics.optics
Measurement of Photocarrier Mean Free Path via Speckled Laser Pump – Transient Fourier Microscopy Probe
Zuni Luo, Yifan Zhang, Jie Wei et al. (+3 more)
The mean free path of photocarriers is a crucial parameter for material design, device optimization, and new optoelectronics applications. Currently, this parameter remains unknown for many materials, and experimental means available for its measurement are considerably lacking. Meanwhile, it remains an unclear issue whether the mean free path of the photogenerated high-energy hot carriers is significantly different from that of the localequilibrium-state carriers near the
Fermi surface or around the band edge. Based on the concept of transient grating
Fourier transform and utilizing a virtual lock-in amplification technique, we proposed and demonstrated an efficient experimental technique for measuring the mean free path of photocarriers. This method has facilitated direct observation of the photocarrier transport behavior across the transition between diffusive and ballistic motion, from which we surprisingly find that the mean free path of photogenerated hot carriers in Silicon membrane and GaAs
quantum well can reach micron scale, more than an order of magnitude larger compared to the electrically-measured one. This work provides new ideas for characterization of photoelectronic devices under operating status and is expected to greatly enhance the understanding of the photocarrier transport process in opto-electronic or photonic materials.
Read the full abstract ▾
All authors Zuni Luo, Yifan Zhang, Jie Wei, Zhikun Xie, Tianshu Lai, Ke Chen
Materials Science · Cross-listed from cond-mat.str-el
Multiple superconducting phases and order-parameter evolution in pressurized UTe$_2$
Shuo Zou, Fengrui Shi, Zhuolun Qiu et al. (+24 more)
The recently discovered heavy-
fermion spin-triplet
superconductor candidate UTe$_2$ provides a rich platform for unconventional pairing and topological phenomena. However, limited has been known about its superconducting order parameters and their
evolution with control parameters, largely due to the lack of appropriate
symmetry-sensitive detections. Here, we report comprehensive point-contact spectroscopy measurements of pressurized UTe$_2$ on the (0~0~1) surface. The observation of Andreev bound states strongly suggests the presence of a $p_z$ component in the superconducting order parameters. Quantitative analysis based on an extended Blonder-Tinkham-Klapwijk model unveils the superconducting order parameters with a finite odd-$k_z$ component (e.g. $B_{2u}$ or $B_{3u}$) for both ambient and pressurized UTe$_2$. Remarkably, the multiple superconducting phases can be distinguished by a single parameter $\langle \Delta_{z}\rangle/\langle\Delta_{x(y)}\rangle$, the relative weight between the $p_z$-wave and $p_{x(y)}$-wave pairings. These findings place stringent constraints on the pairing
symmetry and provide essential spectroscopic signatures for distinguishing pressure-induced multiple superconducting phases in UTe$_2$.
Read the full abstract ▾
All authors Shuo Zou, Fengrui Shi, Zhuolun Qiu, Jia-Long Zhang, Yan Zhang, Weilong Qiu, Zhuo Wang, Hai Zeng, Yinina Ma, Zheyu Wu, Andrej Cabala, Michal Valiska, Ning Li, Zihan Yang, Kaixin Ye, Jiawen Zhang, Yanan Zhang, Kangjian Luo, Binbin Zhang, Alexander G. Eaton, Chaofan Zhang, Gang Li, Jianlin Luo, Wen Huang, Huiqiu Yuan, Xin Lu, Yongkang Luo