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Three-dimensional construction of hyperuniform, nonhyperuniform, and antihyperuniform disordered heterogeneous materials and their transport properties via spectral density functions

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Physical Review E 2025年第3期111卷 035310-035310页

作者： Wenlong Shi Yang Jiao Salvatore Torquato Materials Science and Engineering Arizona State University Tempe Arizona 85287 USA Department of Physics Arizona State University Tempe Arizona 85287 USA Department of Chemistry Princeton University Princeton New Jersey 08544 USA Department of Physics Princeton University Princeton New Jersey 08544 USA Princeton Institute of Materials Princeton University Princeton New Jersey 08544 USA Program in Applied and Computational Mathematics Princeton University Princeton New Jersey 08544 USA

Rigorous theories connecting physical properties of a heterogeneous material to its microstructure offer a promising avenue to guide the computational material design and optimization. The spectral density function χ̃V(k), which can be obtained experimentally from scattering data, enables accurate determination of various transport and wave propagation characteristics, including the time-dependent diffusion spreadability S(t) and effective dynamic dielectric constant εe for electromagnetic wave propagation. Moreover, χ̃V(k) determines rigorous upper bounds on the fluid permeability K. Given the importance of χ̃V(k), we present here an efficient Fourier-space based computational framework to construct three-dimensional (3D) statistically isotropic two-phase heterogeneous materials corresponding to targeted spectral density functions. In particular, we employ a variety of analytical functional forms for χ̃V(k) that satisfy all known necessary conditions to construct disordered stealthy hyperuniform, standard hyperuniform, nonhyperuniform, and antihyperuniform two-phase heterogeneous material systems at varying phase volume fractions. We show that by tuning the correlations in the system across length scales via the targeted functions, one can generate a rich spectrum of distinct structures within each of the above classes of materials. Importantly, we present the first realization of antihyperuniform two-phase heterogeneous materials in 3D, which are characterized by autocovariance function χV(r) with a power-law tail, resulting in microstructures that contain clusters of dramatically different sizes and morphologies. We also determine the diffusion spreadability S(t) and estimate the fluid permeability K associated with all of the constructed materials directly from the corresponding spectral densities. Although it is well established that the long-time asymptotic scaling behavior of S(t) only depends on the functional form of χ̃V(k), with the stealthy hyperuniform a

关键词： Spectral density

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On the origin of anomalous hysteresis in graphite/boron nitride transistors

arXiv

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arXiv 2024年

作者： Waters, Dacen Waleffe, Derek Thompson, Ellis Arreguin-Martinez, Esmeralda Fonseca, Jordan Poirier, Thomas Edgar, James H. Watanabe, Kenji Taniguchi, Takashi Xu, Xiaodong Cobden, David Yankowitz, Matthew Department of Physics University of Washington SeattleWA98195 United States Intelligence Community Postdoctoral Research Fellowship Program University of Washington SeattleWA98195 United States Department of Materials Science and Engineering University of Washington SeattleWA98195 United States Tim Taylor Department of Chemical Engineering Kansas State University Durland Hall ManhattanKS United States Research Center for Electronic and Optical Materials National Institute for Materials Science 1-1 Namiki Tsukuba305-0044 Japan Research Center for Materials Nanoarchitectonics National Institute for Materials Science 1-1 Namiki Tsukuba305-0044 Japan

Field-effect devices constructed by stacking flakes of van der Waals (vdW) materials, with hexagonal boron nitride (hBN) playing the role of gate dielectric, often exhibit virtually no hysteresis in their characteristics. This permits exquisitely detailed studies of diverse gate-voltage-tuned phenomena in vdW devices. Recently, however, a dramatic form of gate hysteresis, sometimes called the "gate doesn't work" (GDW) or "electron ratchet" effect, has been seen in certain individual vdW devices that seem otherwise unexceptional [1-10]. When it occurs, this hysteresis phenomenon is striking and robust, yet it is difficult to reliably reproduce between devices and, largely as a result, its origin remains disputed. Most devices where it has been seen have a bilayer graphene channel and nominal rotational alignment between the graphene and hBN, which has engendered explanations based on properties of bilayer graphene combined with moiré effects [1, 2, 6]. Here, we report our studies of the phenomenon observed in devices that have multilayer graphene channels. We find that the effect can occur in devices with graphite channels that have many more than two graphene layers, in which case it is unambiguously associated with just one surface of the graphite. It can also survive to room temperature, occur in the absence of intentional rotational alignment with hBN, persist when a monolayer of WSe2 is inserted between the graphene and hBN, and exhibit continuous relaxation on timescales of hours or longer. These observations impose strong constraints on the origin of this puzzling phenomenon, which has exciting potential applications if it can be mastered [4, 10, 11]. Copyright © 2024, The Authors. All rights reserved.

关键词： Van der Waals forces

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Increased light-emission efficiency in disordered InGaN through the correlated reduction of recombination rates

arXiv

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arXiv 2023年

作者： Pant, Nick Kioupakis, Emmanouil Applied Physics Program University of Michigan Ann ArborMI48109 United States Department of Materials Science & Engineering University of Michigan Ann ArborMI48109 United States

Experiments have shown that the light-emission efficiency of indium gallium nitride (InGaN) light-emitting diodes improves with increasing indium concentration. It is widely thought that compositional fluctuations due to indium incorporation suppress diffusion of carriers to non-radiative centers, thus leading to defect-insensitive emission. However, recent experiments have challenged this hypothesis by revealing unexpectedly long diffusion lengths at room temperature. Here, we demonstrate an alternative mechanism involving the correlated reduction in radiative and nonradiative recombination rates that explains the increase in light-emission efficiency of InGaN with increasing indium concentration, without invoking the suppression of carrier diffusion. Our analysis challenges the notion that carrier localization gives rise to defect tolerance in InGaN. Copyright © 2023, The Authors. All rights reserved.

关键词： III-V semiconductors

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Performance Enhancement of Electrochemiluminescence with the Immunosensor Controlled Using Magnetized Masks for the Determination of Epithelial Cancer Biomarker EpCAM

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Analytical Chemistry 2023年第2期95卷 986-993页

作者： Huang, Chun-Yao Lin, Feng-Yen Chang, Chi-Jung Lu, Chien-Hsing Chen, Jem-Kun Taipei Heart Institute Taipei Medical University 250 Wu-Hsing Street Taipei110 Taiwan Division of Cardiology and Cardiovascular Research Center Taipei Medical University Hospital 252 Wu-Hsing Street Taipei110 Taiwan Department of Internal Medicine School of Medicine College of Medicine Taipei Medical University 250 Wu-Hsing Street Taipei110 Taiwan Department of Biomedical Sciences and Engineering National Central University 300 Zhongda Road Taoyuan City320317 Taiwan Department of Materials Science and Engineering National Taiwan University of Science and Technology 43 Sec. 4 Keelung Road Taipei106 Taiwan Department of Chemical Engineering Feng Chia University 100 Wenhwa Road Taichung40724 Taiwan Department of Obstetrics and Gynecology Taichung Veterans General Hospital 1650 Taiwan Boulevard Sect. 4 Taichung40705 Taiwan Institute of Biomedical Sciences Ph.D. Program in Translational Medicine Rong-Hsing Research Center for Translational Medicine National Chung-Hsing University Taichung940227 Taiwan

The performance of an electrochemiluminescence (ECL) immunosensor was improved with a particle gradient. SiO2-coated magnetic beads were adopted as nanocarriers for gradient manipulation and immobilized with the primary antibody. Cadmium telluride quantum dots were coated with a layer of protein G for conjugation and orientation of the secondary antibody as signal labels. ECL immunosensor gradients on the electrode were formed by magnetolithography (ML) with magnetized nickel masks of column and stripe arrays. The immunosensor generally aggregated as an island on the substrate, leading to a decrease of efficiency in the characteristic signals. Stripe arrays of magnetized nickel were designed to generate cylindrical magnetic flux on the substrate to improve the particle manipulation with the gradient. Various gradients of the sandwich-structured immunosensor substantially affected the electrochemical performance. Compared to the gradient-free immunosensor, the gradient of the immunosensor generated by ML using a 3 μm stripe array mask enhanced the ECL intensity ∼2.2 times. The results of quantification of epithelial cell adhesion molecules (EpCAM) with the gradient immunosensor showed a broad linear range (15-420 pg mL-1), a low limit of detection (5.5 pg mL-1), and high reliability for EpCAM-spiked serum samples, indicating that the immunosensor gradient substantially enhances the performance of the ECL assay. © 2022 American Chemical Society.

关键词： Immunosensors

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Fate of multipolar physics in 5d2 double perovskites

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Physical Review B 2023年第4期108卷 045149-045149页

作者： Ahmed Rayyan Xiaoyu Liu Hae-Young Kee Department of Physics University of Toronto Toronto Ontario Canada M5S 1A7 Department of Materials Science and Engineering University of Washington Seattle Washington 98195 USA CIFAR Program in Quantum Materials Canadian Institute for Advanced Research Toronto Ontario Canada M5G 1M1

In a cubic environment, the ground state of spin-orbit coupled 5d2 ions is a non-Kramers Eg doublet, which hosts quadrupole and octupole moments. A series of 5d2 osmium double perovskites Ba2MOsO6 (M=Mg, Ca, Zn, Cd) have recently been proposed to exhibit multipolar orders. We investigate the structural properties of these materials using ab initio calculations and find that the cubic structure is unstable for the Cd compound while the Mg, Ca, and Zn materials retain Fm3¯m symmetry. We show that Ba2CdOsO6 favors a rhombohedral R3¯ structure characterized by a−a−a− octahedral tiltings as indicated by unstable T1g phonon modes. Trigonal distortions split the excited T2g triplet into an Eg′ doublet and an Ag singlet, which may cross energy levels with the Eg doublet and suppress the multipolar physics. We find a window where Eg remains the lowest energy state under trigonal distortion, enabling the emergence of multipole phases in noncubic crystal environments.

关键词： Spin-orbit coupling Mott insulators Perovskites Crystal-field theory Density functional theory

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Cr is not an acceptor in β−Ga2O3

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Physical Review materials 2025年第5期9卷 054606-054606页

作者： Cassandra Remple Benjamin L. Dutton Joel B. Varley John S. McCloy Matthew D. McCluskey Materials Science & Engineering Program Washington State University Pullman Washington 99164-2711 USA Department of Physics and Astronomy Washington State University Pullman Washington 99164-2814 USA Institute of Materials Research Washington State University Pullman Washington 99164-2711 USA Lawrence Livermore National Laboratory Livermore California 94551-0808 USA

The intensity of red Cr3+ photoluminescence (PL) in monoclinic gallium oxide (β−Ga2O3) is suppressed by n-type conductivity, an effect that has been attributed to a Cr deep acceptor level in the bandgap. In n-type material, such an acceptor level would be occupied, resulting in the Cr2+ oxidation state and the absence of Cr3+ PL. To test this model, n-type β−Ga2O3 crystals co-doped with Cr and Zr (a donor) were grown from the melt. The samples show Cr3+ optical absorption bands and a high free-electron concentration of 4×1018cm−3. If Cr were an acceptor, then it would be fully compensated and therefore would not exhibit the Cr3+ optical signature. Hybrid functional calculations indicate that Cr occupies the substitutional octahedral Ga(II) site and that the Cr2+ state is energetically unfavorable, i.e., Cr is not an acceptor. Weak Cr3+ PL was observed in the Cr/Zr co-doped samples. The quenching of PL may be caused by a transfer of energy to free electrons, a nonradiative process that would reduce the emission intensity.

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Learning from 2D: machine learning of 3D effective properties of heterogeneous materials based on 2D microstructure sections

arXiv

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arXiv 2023年

作者： Hu, Guangyu Latypov, Marat I. Department of Materials Science and Engineering University of Arizona TucsonAZ85721 United States Graduate Interdisciplinary Program in Applied Mathematics University of Arizona TucsonAZ85721 United States

Microstructure–property relationships are key to effective design of structural materials for advanced applications. Advances in computational methods enabled modeling microstructure-sensitive properties using 3D models (e.g., finite elements) based on microstructure representative volumes. 3D microstructure data required as input to these models are typically obtained from either 3D characterization experiments or digital reconstruction based on statistics from 2D microstructure images. In this work, we present machine learning (ML) approaches to modeling effective properties of heterogeneous materials directly from 2D microstructure sections. To this end, we consider statistical learning models based on spatial correlations and convolutional neural networks as two distinct ML strategies. In both strategies, models are trained on a dataset of synthetically generated 3D microstructures and their properties obtained from micromechanical 3D simulations. Upon training, the models predict properties from 2D microstructure sections. The advantage of the presented models is that they only need 2D sections, whose experimental acquisition is more accessible compared to 3D characterization. Furthermore, the present models do not require digital reconstruction of 3D microstructures. © 2023, CC BY.

关键词： Microstructure

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Large effective magnetic fields from chiral phonons in rare-earth halides

arXiv

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arXiv 2023年

作者： Luo, Jiaming Lin, Tong Zhang, Junjie Chen, Xiaotong Blackert, Elizabeth R. Xu, Rui Yakobson, Boris I. Zhu, Hanyu Department of Materials Science and Nano Engineering Rice University HoustonTX77005 United States Applied Physics Graduate Program Rice University HoustonTX77005 United States

Time-reversal symmetry (TRS) is pivotal for materials’ optical, magnetic, topological, and transport properties. Chiral phonons, characterized by atoms rotating unidirectionally around their equilibrium positions, generate dynamic lattice structures that break TRS. Here we report that coherent chiral phonons, driven by circularly polarized terahertz light pulses, can polarize the paramagnetic spins in CeF3 like a quasi-static magnetic field on the order of 1 Tesla. Through time-resolved Faraday rotation and Kerr ellipticity, we found the transient magnetization is only excited by pulses resonant with phonons, proportional to the angular momentum of the phonons, and growing with magnetic susceptibility at cryogenic temperatures, as expected from the spin-phonon coupling model. The time-dependent effective magnetic field quantitatively agrees with that calculated from phonon dynamics. Our results may open a new route to directly investigate mode-specific spin-phonon interaction in ultrafast magnetism, energy-efficient spintronics, and non-equilibrium phases of matter with broken TRS. Copyright © 2023, The Authors. All rights reserved.

关键词： Phonons

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Anomalous elastic softening in ferroelectric hafnia under pressure

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Physical Review B 2025年第6期111卷 064106-064106页

作者： Alejandro Alvarez Niaz Abdolrahim Sobhit Singh Materials Science Program University of Rochester Rochester New York 14627 USA Department of Mechanical Engineering University of Rochester Rochester New York 14627 USA Laboratory for Laser Energetics University of Rochester Rochester New York 14627 USA Center for Coherence and Quantum Optics University of Rochester Rochester New York 14627 USA

This study employs first-principles density-functional theory (DFT) calculations to explore the elastic and mechanical properties of ferroelectric hafnia (HfO2) in its polar orthorhombic Pca21 phase under varying hydrostatic pressure conditions up to 30 GPa. Utilizing a plane-wave basis set and Perdew-Burke-Ernzerhof generalized-gradient approximation for solids in our DFT calculations, we investigate both pure and yttrium-substituted HfO2. Our findings reveal an anomalous reduction in the C33 component of the elastic tensor with increasing pressure, which becomes significant above 15 GPa and signals a potential pressure-driven structural phase transition at higher pressure. The analysis of atomic displacements under pressure sheds light on the unusual mechanical behavior and phase stability of this material. Additionally, we observe a transition from an indirect band gap to a direct band gap with increasing pressure, which could have significant implications for optical applications. The effects of yttrium substitution on the mechanical and electronic properties are further examined, revealing that yttrium substitution softens the elastic response of this material and reduces the electronic band gap. These results enhance our understanding of elastic and mechanical responses of ferroelectric hafnia and its potential for applications in microelectronics, piezoelectric devices, and nonvolatile ferroelectric random-access memories. Further experimental validation is recommended to confirm our predictions and explore the practical implications of the observed phase transitions and electronic behavior of the ferroelectric hafnia under high-pressure conditions.

关键词： Ferroelectricity

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Developments in the utilization of heterogeneous catalysts for biodiesel generation: An update on recent advancements

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Journal of the Taiwan Institute of Chemical Engineers 2024年

作者： Parameshwar, Sai Agnihotri, Mayank Bhan, Uday Nangan, Senthilkumar Verma, Deepak Rajendran, Saravanan Jain, Siddharth Department of Petroleum Engineering and Earth Sciences UPES Dehradun248007 India Metallurgy and Materials Science Research Institute Chulalongkorn University Bangkok10330 Thailand International Graduate Program of Nanoscience and Technology Chulalongkorn University Bangkok10330 Thailand Instituto de Alta Investigacion Universidad de Tarapacá Arica1000000 Chile Department of Mechanical Engineering UPES Dehradun248007 India

Background: Biodiesel is one of the ecofriendly energy sources that can be generated from edible, non-edible, waste, and algae feedstocks. Over time, the utilization of different kinds of heterogeneous catalysts has been proven critical in the manufacture of biodiesel from diverse feedstocks. They exhibit better reusability and easier separation compared to the homogenous catalysts. Methods: In this work, the advances in the use of heterogeneous catalysts for biodiesel production from 2018 to 2024 have been evaluated. The process parameters like alcohol to oil molar ratio (M/O), catalyst concentration (%), reaction time and reaction temperature (RT), reusability of the catalyst, etc. are evaluated. The catalysts derived from waste materials through the calcination process are an efficient and cost-effective substitute for conventional catalysts. Nanomaterials, due to their small size and higher aspect ratio, provide very high efficiency and reusability in catalytic reactions. Significant findings: The heterogeneous catalysts are also found to be highly reusable for multiple cycles and the leaching of active sites, clogging of pore spaces of catalyst, etc. are the major causes of catalyst deactivation. Magnetic heterogeneous catalysts have shown good biodiesel yields and high reusability. Also, naturally occurring calcium oxide and potassium compounds present in waste derived catalysts helped to give high biodiesel yields. The future direction in the path of development of heterogeneous catalysts from cheap, abundant, and environmentally benign materials. The synthesis of heterogeneous catalysts from waste materials addresses the issue of waste disposal and converting solid waste to value-added catalysts. The life cycle assessment studies, encompassing heterogeneous catalyst synthesis, feedstock oil extraction, biodiesel production, and fuel combustion may give valuable input on the environmental impact of the entire process. © 2024

关键词： Potassium compounds

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