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An inorganic liquid crystalline dispersion with 2D ferroelectric moieties

National Science Review 2024年第5期11卷 254-263页

作者： Ziyang Huang Zehao Zhang Rongjie Zhang Baofu Ding Liu Yang Keyou Wu Youan Xu Gaokuo Zhong Chuanlai Ren Jiarong Liu Yugan Hao Menghao Wu Teng Ma Bilu Liu Shenzhen Graphene Centre Shenzhen Key Laboratory of Advanced Layered Materials for Value-added ApplicationsTsinghua-Berkeley Shenzhen Institute and Institute of Materials ResearchTsinghua Shenzhen International Graduate School Tsinghua University Institute of Technology for Carbon Neutrality Faculty of Materials Science and Engineering Shenzhen Institute of Advanced Technology Chinese Academy of Sciences School of Physics and Institute for Quantum Science and Engineering School of Chemistry and Institute of Theoretical ChemistryHuazhong University of Science and Technology Xi'an Research Institute of High Technology Shenzhen Institute of Advanced Technology Chinese Academy of Sciences Department of Applied Physics Hong Kong Polytechnic University

Electro-optical effect-based liquid crystal devices have been extensively used in optical modulation techniques, in which the Kerr coefficient reflects the sensitivity of the liquid crystals and determines the strength of the device's operational electric field. The Peterlin–Stuart theory and the O'Konski model jointly indicate that a giant Kerr coefficient could be obtained in a material with both a large geometrical anisotropy and an intrinsic polarization, but such a material is not yet reported. Here we reveal a ferroelectric effect in a monolayer two-dimensional mineral vermiculite. A large geometrical anisotropy factor and a large inherent electric dipole together raise the record value of Kerr coefficient by an order of magnitude, till 3.0 × 10-4mV-2. This finding enables an ultra-low operational electric field of10～2–10～4V m-1and the fabrication of electro-optical devices with an inch-level electrode separation, which has not previously been practical. Because of its high ultraviolet stability（decay <1% under ultraviolet exposure for 1000 hours）, large-scale production, and energy efficiency, prototypical displayable billboards have been fabricated for outdoor interactive scenes. This work provides new insights for both liquid crystal optics and two-dimensional ferroelectrics.

关键词： 2D materials layered minerals vermiculite ferroelectric inorganic liquid crystal Kerr coefficient

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Realization of a spin-1/2 Kondo necklace model with magnetic field-induced coupling switch

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Physical Review Research 2025年第1期7卷 L012023-L012023页

作者： Hironori Yamaguchi Yu Tominaga Takanori Kida Koji Araki Takashi Kawakami Yoshiki Iwasaki Kenta Kimura Masayuki Hagiwara Department of Physics Osaka Metropolitan University Osaka 599-8531 Japan Innovative Quantum Material Center (IQMC) Osaka Metropolitan University Osaka 599-8531 Japan Center for Advanced High Magnetic Field Science (AHMF) Graduate School of Science Osaka University Osaka 560-0043 Japan Department of Applied Physics National Defense Academy Kanagawa 239-8686 Japan Department of Chemistry Osaka University Osaka 560-0043 Japan Department of Physics College of Humanities and Sciences Nihon University Tokyo 156-8550 Japan Department of Materials Science Osaka Metropolitan University Osaka 599-8531 Japan

The theoretical Kondo necklace model, which simplifies the Kondo lattice model by focusing on spin degrees of freedom, provides a valuable framework for understanding spin-related quantum phenomena. However, it has not been applied to real materials until now. We present a realization of a spin-1/2 anisotropic Kondo necklace model using a complex of radical and Co spins. Electron spin resonance reveals anisotropic g values and an Ising-type exchange interaction with Co spin. The specific heat measurements demonstrate Schottky-type behavior, suggesting a Kondo singlet state with an energy gap in the excitation spectrum. Our findings suggest that a magnetic field can decouple Kondo interactions, unveiling a different mechanism for controlling Kondo coupling. This offers other opportunities for quantum technologies, particularly in the development of tunable qubits for quantum computing and spintronic devices, where precise control over spin interactions is essential.

关键词： Electron spin resonance spectroscopy

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Plasmonic BICs as Biosensors with Better Detectivity

Plasmonic BICs as Biosensors with Better Detectivity

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2023 Conference on Lasers and Electro-Optics, CLEO 2023

作者： Li, Zhichao Prasad, Ciril S. Wang, Xielin Naik, Gururaj V. Applied Physics Graduate Program Smalley-Curl Institute Rice University HoustonTX77005 United States Department of Electrical and Computer Engineering Rice University HoustonTX77005 United States

Plasmonic sensors exhibit high sensitivity due to enhanced local fields. But, their detectivity is poor because of their poor Q-factors. Using a plasmonic BIC, we experimentally demonstrate enhanced Q-factors in a pla... 详细信息

ISBN: (纸本)9781957171258

关键词： Q factor measurement

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Magnetoelastic coupling driven magnon gap in a honeycomb antiferromagnet

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Physical Review B 2024年第10期110卷 104419页

作者： Jeongheon Choe Andrey Baydin Gaihua Ye Bowen Ma Cynthia Nnokwe Martin Rodriguez-Vega David Lujan Swati Chaudhary Fuyang Tay Jiaming He Hiroyuki Nojiri Jianshi Zhou Gregory A. Fiete Junichiro Kono Rui He Xiaoqin Li Department of Physics Center of Complex Quantum Systems Center for Dynamics and Control of Materials Department of Electrical and Computer Engineering Smalley–Curl Institute Department of Physics Applied Physics Graduate Program Smalley–Curl Institute Department of Mechanical Engineering Institute for Materials Research Department of Physics and Astronomy Department of Materials Science and NanoEngineering

Cobalt titanate, CoTiO3, is a honeycomb antiferromagnet recently confirmed experimentally to host Dirac magnons, topological spin-orbit excitons, and chiral phonons. Here, we investigate a magnon gap at the zone center which calls for a refined spin Hamiltonian. We propose a microscopic model for the magnon gap and attribute it to a lattice-distortion (phonon)-induced higher-order spin interaction. Strong magnetoelastic coupling in CoTiO3 is also evident in Raman spectra, in which the magnetic order exerts a stronger influence on phonons corresponding to in-plane ionic motions than those with out-of-plane motions. We further examine the evolution of the zone-center magnons in a high magnetic field up to 18.5 T via THz absorption spectroscopy measurements. Based on this field dependence, we propose a spin Hamiltonian that not only agrees with magnon dispersion measured by inelastic neutron scattering but also includes fewer exchange constants and a realistic anisotropy term. Our work highlights the broad implications of magnetoelastic coupling in the study of topologically protected bosonic excitations.

关键词： Magnetism Magnons Topological materials Raman spectroscopy Terahertz spectroscopy

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Detection of Femtomolar Amyloid-β Peptides for Early-Stage Identification of Alzheimer’s Amyloid-β Aggregation with Functionalized Gold Nanoparticles

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ACS applied Materials and Interfaces 2024年第3期16卷 3819-3828页

作者： Chang, Yu-Jen Chien, Yi-Hsin Chang, Chieh-Chun Wang, Pei-Ning Chen, Yun-Ru Chang, Yun-Chorng Genomics Research Center Academia Sinica Taipei115 Taiwan Taiwan International Graduate Program in Interdisciplinary Neuroscience National Taiwan University and Academia Sinica Taipei115 Taiwan Research Center for Applied Sciences Academia Sinica Taipei115 Taiwan Department of Physics National Taiwan University Taipei106 Taiwan Nano Science and Technology Program Taiwan International Graduate Program Academia Sinica and National Taiwan University Taipei115 Taiwan Brain Research Center National Yang Ming Chiao Tung University Taipei112 Taiwan Division of General Neurology Department of Neurological Institute Taipei Veterans General Hospital Taipei112 Taiwan

Progressive amyloid-β (Aβ) fibrillar aggregates have long been considered as the pathogenesis of Alzheimer’s disease (AD). Biocompatible and stable cysteine-Aβ peptide-conjugated gold nanoparticles (Cys-Aβ@AuNP) are demonstrated as suitable materials for detecting subfemtomolar Aβ peptides in human plasma. Incubation with Aβ peptides causes the Cys-Aβ@AuNP to aggregate and changes its absorption spectra. The spectral change is especially apparent and noticeable when detecting subfemtomolar Aβ peptides, and the aggregates contain only two or three AuNPs. Cys-Aβ@AuNP can also be used to identify early-stage Aβ oligomerization, which is not possible using the conventional method, in which the fluorescence of thioflavin-T is measured. The ability to detect Aβ oligomerization can facilitate therapeutics for AD. In addition, the binding of Aβ peptides by Cys-Aβ@AuNP in combination with centrifugation redirects the conventional Aβ aggregation pathway and can effectively inhibit the formation of toxic Aβ oligomers or fibrils. Therefore, the proposed Cys-Aβ@AuNP can also be used to develop effective therapeutic agents to inhibit Aβ aggregation. The results obtained in this study are expected to open revolutionary ways to both detect and inhibit Aβ aggregation at an early stage. © 2024 American Chemical Society

关键词： Oligomers

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Singular vectors of sums of rectangular random matrices and optimal estimation of high-rank signals: The extensive spike model

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Physical Review E 2023年第5期108卷 054129-054129页

作者： Itamar D. Landau Gabriel C. Mel Surya Ganguli Department of Applied Physics Stanford University Stanford California 94305 USA Neuroscience Graduate Program Stanford University Stanford California 94305 USA

Across many disciplines spanning from neuroscience and genomics to machine learning, atmospheric science, and finance, the problems of denoising large data matrices to recover hidden signals obscured by noise, and of estimating the structure of these signals, is of fundamental importance. A key to solving these problems lies in understanding how the singular value structure of a signal is deformed by noise. This question has been thoroughly studied in the well-known spiked matrix model, in which data matrices originate from low-rank signal matrices perturbed by additive noise matrices, in an asymptotic limit where matrix size tends to infinity but the signal rank remains finite. We first show, strikingly, that the singular value structure of large finite matrices (of size ∼1000) with even moderate-rank signals, as low as 10, is not accurately predicted by the finite-rank theory, thereby limiting the application of this theory to real data. To address these deficiencies, we analytically compute how the singular values and vectors of an arbitrary high-rank signal matrix are deformed by additive noise. We focus on an asymptotic limit corresponding to an extensive spike model, in which both the signal rank and the size of the data matrix tend to infinity at a constant ratio. We map out the phase diagram of the singular value structure of the extensive spike model as a joint function of signal strength and rank. We further exploit these analytics to derive optimal rotationally invariant denoisers to recover the hidden high-rank signal from the data, as well as optimal invariant estimators of the signal covariance structure. Our extensive-rank results yield several conceptual differences compared to the finite-rank case: (1) as signal strength increases, the singular value spectrum does not directly transition from a unimodal bulk phase to a disconnected phase, but instead there is a bimodal connected regime separating them; (2) the signal singular vectors can be partiall

关键词： Stochastic inference Data analysis Random matrix theory Statistical methods Stochastic analysis methods

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Accuracy of DFT computed oxygen-vacancy formation energies and high-throughput search of solar thermochemical water-splitting compounds

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Physical Review Materials 2023年第6期7卷 065403-065403页

作者： Bianca Baldassarri Jiangang He Xin Qian Emanuela Mastronardo Sean Griesemer Sossina M. Haile Christopher Wolverton Graduate Program in Applied Physics Northwestern University Evanston Illinois USA Department of Materials Science and Engineering Northwestern University Evanston Illinois USA

The enthalpy change involved in metal oxide reduction is a key quantity in various processes related to energy conversion and storage and is of particular interest for computational prediction. Often this prediction involves the simulation of a high-temperature reduction process with a 0-K methodology like density functional theory (DFT), and it is not infrequent for the high temperature and 0-K stable crystal structures to differ. This introduces a conundrum with regard to the choice of crystal structure to utilize in the computation, with approaches in the literature varying and experimental validation remaining scarce. In this work, we address both the crystal structure conundrum and the experimental validation, and then apply the insights we gain to guide a high-throughput search for new materials for solar thermochemical water-splitting applications. By computing the DFT+U oxygen-vacancy formation energy (ΔEvf) of a selection of ABO3 compounds and comparing different crystal structures for each composition, we highlight the issues that arise when the structure utilized in the computation is dynamically unstable at 0 K, namely the presence of an artificial lowering of ΔEvf, and the lack of convergence of ΔEvf with cell size. We solve these limitations by identifying and employing a suitable surrogate dynamically stable structure. We then validate the predictive power of our calculations against appositely generated experimental measurements of reduction enthalpy for a series of Hubbard U values, finding an accuracy ranging between 0.2–0.6 eV/O. In light of such conclusions, we revise and expand a previous a high-throughput DFT study on ABO3 perovskite oxides. We provide a list of candidate STCH materials, highlight trends with redox-active cation and structural distortion, and identify Mn4+, Mn3+, and Co3+ as the most promising redox-active cations.

关键词： Energy applications First-principles calculations Hydrogen energy

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Spray-pyrolysis synthesis of CuMnO₂ with the potential for photoelectrocatalysis

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Journal of the Chinese Chemical Society 2024年第10期71卷 1203-1210页

作者： Martinez, Benjamin Kuo, Chun-Hong Chiang, Ming-Hsi Institute of Chemistry Academia Sinica Taipei Taiwan Sustainable Chemical Science and Technology Taiwan International Graduate Program Academia Sinica and National Yang Ming Chiao Tung University Hsinchu Taiwan Department of Applied Chemistry National Yang Ming Chiao Tung University Hsinchu Taiwan Center for Emergent Functional Matter Science National Yang Ming Chiao Tung University Hsinchu Taiwan National Synchrotron Radiation Research Center Hsinchu Taiwan Department of Medicinal and Applied Chemistry Kaohsiung Medical University Kaohsiung Taiwan

Amidst the global endeavor toward sustainable energy sources, photocatalysis appears as a promising gateway toward the production of solar fuels, in particular hydrogen. Hydrogen is currently a crucial reagent for vital industries such as petrol desulfurization, iron reduction and ammonia production, so the decarbonization of its production is a major challenge. CuMnO₂ (CMO), a p-type semiconductor, has been shown to enhance the efficiency of catalysts such as TiO₂ for the photoelectrocatalytic water splitting reaction. However, since pure CMO thin films have never been reported, its potential and limitations remain elusive. We used spray pyrolysis as a low-cost synthesis technique to simplify and accelerate the synthesis of CMO thin films directly on FTO substrates. CMO prepared in this manner exhibits activity toward photoeletrocatalytic water splitting and O₂ reduction. The activity has been found to be highly dependent on synthesis conditions, especially on the ratio and volume of precursors. © 2024 The Chemical Society Located in Taipei & Wiley-VCH GmbH.

关键词： crednerite hydrogen oxygen reduction p-type semiconductor water splitting

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Synergetic effects of multiple junction and surface hydroxyl in Cu/CuO/Cu2O/TiO2 heterostructures towards highly efficient photocatalysts for hydrogen generation

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Materials Science for Energy Technologies 2025年 8卷 131-142页

作者： Subagyo, Riki Anindika, Garcelina Rizky Aufkani, Afif Akmal Zhang, Lei Ardhyananta, Hosta Burhan, R.Y. Perry Nugraheni, Zjahra Vianita Akhlus, Syafsir Bahruji, Hasliza Prasetyoko, Didik Wellia, Diana Vanda Ivansyah, Atthar Luqman Arramel Kusumawati, Yuly Department of Chemistry Faculty of Science and Analytic Data Institut Teknologi Sepuluh Nopember Surabaya60111 Indonesia Center of Excellence Applied Physics and Chemistry Nano Center Indonesia Jl PUSPIPTEK South Tangerang Banten15314 Indonesia Department of Physics National University of Singapore Singapore117551 Singapore Department of Materials and Metallurgical Engineering Faculty of Industrial Technology and Systems Engineering Institut Teknologi Sepuluh Nopember Surabaya60111 Indonesia Centre of Advanced Material and Energy Science Universiti Brunei Darussalam Jalan Tungku Link BE 1410 Brunei Department of Chemistry Faculty of Mathematics and Natural Sciences Universitas Andalas Padang25163 Indonesia Master Program in Computational Science Faculty of Mathematics and Natural Science Institut Teknologi Bandung Jalan Ganesha No. 10 Bandung40132 Indonesia Instrumentation and Computational Physics Research Group Department of Physics Faculty of Mathematics and Natural Sciences Institut Teknologi Bandung Jalan Ganesha No.10 West Java Bandung40132 Indonesia

The implementation of titanium dioxide (TiO2) as a photocatalyst material in hydrogen (H2) evolution reaction (HER) has embarked renewed interest in the past decade. Rapid electron-hole pairs recombination and wide band gap of a photo-sensitive material of TiO2 are detrimental toward the targeted catalytical reaction. In this study, we present the rational design, fabrication, photocatalytic performance of TiO2-Cu/CuO/Cu2O heterostructures (CuTi) using viable chemical reduction method. The Z-scheme and S-scheme are succesfully generated across the TiO2/CuO/Cu2O interfaces, while the Schottky junction arises on the Cu perimeters. This is evidenced from the blue shifted about 0.3 eV of Cu 2p core level determined by using X-ray photoemission spectroscopy (XPS), in combination with the formation of inverse V-shape of the Mott-Schottky plots. In addition, we find that Cu/CuO/Cu2O facilitates photon absorption range up to the visible region. The multiple heterojunction and the large number of OHsurface enhanced charge carrier transfer are associated to the suppression of photoluminescence (PL) intensity, high surface hydroxyl (OHsurface) density in CuTi probed by XPS, and fast electron transfer based on the electrochemical measurements. The presence of OHsurface inhibits the recombination of electron. A significant H2 photogeneration rate enhancement is achieved when an optimized 5 wt% Cu/CuO/Cu2O concentration is used on TiO2 to achieve 7,157.19 μmol·g−1 (1,789.30 μmol·g−1·h−1). Based on this finding, zero emission energy innitiative could be materialized under multiple heterojunctions in photocatalytic process is beneficial for enhancing the H2 production. © 2025 The Authors

关键词： Titanium dioxide

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Excitations in layered materials from a non-empirical Wannier-localized optimally-tuned screened rangeseparated hybrid functional

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npj Computational Materials 2024年第1期10卷 132-140页

作者： María Camarasa-Gómez Stephen E.Gant Guy Ohad Jeffrey B.Neaton Ashwin Ramasubramaniam Leeor Kronik Department of Molecular Chemistry and Materials Science Weizmann Institute of ScienceRehovoth7610001Israel Department of Physics University of CaliforniaBerkeleyCA94720USA Materials Sciences Division Lawrence Berkeley National LaboratoryBerkeleyCA94720USA Kavli Energy NanoSciences Institute at Berkeley University of CaliforniaBerkeleyCA94720USA Department of Mechanical and Industrial Engineering University of Massachusetts AmherstAmherstMA01003USA Materials Science and Engineering Graduate Program University of MassachusettsAmherstAmherstMA01003USA

Accurate prediction of electronic and optical excitations in van der Waals(vdW)materials is a long-standing challenge for density functional *** recent Wannier-localized optimally-tuned screened range-separated hybrid(WOT-SRSH)functional has proven successful in non-empirical determination of electronic band gaps and optical absorption spectra for covalent and ionic ***,for vdW materials the tuning of the material-and structure-dependent functional parameters has only been attained ***,we present a non-empirical WOT-SRSH approach applicable to vdW materials,with the optimal functional parameters transferable between monolayer and *** apply this methodology to prototypical vdW materials:black phosphorus,molybdenum disulfide,and hexagonal boron nitride(in the latter case including zero-point renormalization).We show that the WOT-SRSH approach consistently achieves accuracy levels comparable to experiments and many-body perturbation theory(MBPT)calculations for band structures and optical absorption spectra,both on its own and as an optimal starting point for MBPT calculations.

关键词： theory optimal functional

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