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Crystalline-symmetry-protected Majorana modes in coupled quantum dots

Physical Review Research 2025年第1期7卷 L012022-L012022页

作者： Bradraj Pandey Gonzalo Alvarez Elbio Dagotto Rui-Xing Zhang Department of Physics and Astronomy The University of Tennessee Knoxville Tennessee 37996 USA Materials Science and Technology Division Oak Ridge National Laboratory Oak Ridge Tennessee 37831 USA Computational Sciences and Engineering Division Oak Ridge Tennessee 37831 USA Department of Materials Science and Engineering The University of Tennessee Knoxville Tennessee 37996 USA

We propose a minimalist architecture for achieving various crystalline-symmetry-protected Majorana modes in an array of coupled quantum dots. Our framework is motivated by the recent experimental demonstrations of two-site and three-site artificial Kitaev chains in a similar setup. We find that introducing a π-phase domain wall in the Kitaev chain leads to a pair of mirror-protected Majorana zero modes located at or near the junction. Joining two π junctions into a closed loop, we can simulate two distinct classes of two-dimensional higher-order topological superconducting phases, both carrying symmetry-protected Majorana modes around the sample corners. As an extension of the π junction, we further consider a general vertex structure where n Kitaev chains meet, i.e., a Kitaev n vertex. We prove that such an n vertex, if respecting a dihedral symmetry group Dn, necessarily carries n vertex-bound Majorana modes protected by the Dn symmetry. Resilience of the junction and vertex Majorana bound states against disorder and correlation effects is also discussed. Our architecture paves the way for designing, constructing, and exploring a wide variety of artificial topological crystalline phases in quantum-dot experiments.

关键词： Crystalline materials

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Large anomalous Nernst effect and its bipolarity in the quaternary equiatomic Heusler alloys CrRuXGe (X=Co and Mn)

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Physical Review B 2024年第22期109卷 224415-224415页

作者： Amit Chanda Jadupati Nag Noah Schulz Aftab Alam K. G. Suresh Manh-Huong Phan Hariharan Srikanth Department of Physics Magnetic Materials Laboratory Department of Physics Materials Research Institute and Department of Materials Science and Engineering

Here we report on a comprehensive investigation of transverse magnetothermoelectric properties of the equiatomic quaternary Heusler alloys CrRuXGe (X = Co and Mn). Magnetic measurements reveal the presence of a glassy magnetic ground state owing to the energetically competing ferromagnetic and antiferromagnetic phases in CrRuCoGe at low temperatures, whereas CrRuMnGe exhibits soft ferromagnetic behavior with a weak martensitic transformation close to room temperature. The temperature-dependent anomalous Nernst coefficient (SANE) of CrRuMnGe shows noticeable changes around the martensitic transformation. While CrRuCoGe exhibits positive SANE, CrRuMnGe exhibits negative SANE throughout the measured temperature range. We demonstrate that the contribution of the anomalous transverse thermoelectric conduction dominates that of the anomalous Hall effect acting on the thermally generated carrier flow induced by the longitudinal Seebeck effect, which gives rise to the opposite polarity of SANE in these two alloys. Our detailed analysis indicates that the origin of the observed anomalous Nernst effect (ANE) in both of these alloys is dominated by the asymmetric skew scattering of charge carriers in the measured temperature regime. The sign change and tunability of ANE presented in this study provide a step forward toward the development of ANE-based efficient thermopile devices operating at room temperature utilizing the equiatomic quaternary Heusler alloys.

关键词： Magnetic interactions Magnetotransport Spintronics Thermal conductivity Thermoelectric effects Thermomagnetic effects

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Migration and proliferation drive the emergence of patterns in co-cultures of differentiating vascular progenitor cells

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Mathematical Biosciences and engineering 2024年第8期21卷 6731-6757页

作者： Zamora Alvarado, Jose E. McCloskey, Kara E. Gopinathan, Ajay School of Engineering University of California Merced MercedCA95343 United States Graduate Program in Materials and Biomaterials Science and Engineering University of California Merced MercedCA95343 United States Department of Physics University of California Merced MercedCA95343 United States

Vascular cells self-organize into unique structures guided by cell proliferation, migration, and/or differentiation from neighboring cells, mechanical factors, and/or soluble signals. However, the relative contribution of each of these factors remains unclear. Our objective was to develop a computational model to explore the different factors affecting the emerging micropatterns in 2D. This was accomplished by developing a stochastic on-lattice population-based model starting with vascular progenitor cells with the potential to proliferate, migrate, and/or differentiate into either endothelial cells or smooth muscle cells. The simulation results yielded patterns that were qualitatively and quantitatively consistent with experimental observations. Our results suggested that post-differentiation cell migration and proliferation when balanced could generate between 30–70% of each cell type enabling the formation of vascular patterns. Moreover, the cell-to-cell sensing could enhance the robustness of this patterning. These findings computationally supported that 2D patterning is mechanistically similar to current microfluidic platforms that take advantage of the migration-directed self-assembly of mature endothelial and mural cells to generate perfusable 3D vasculature in permissible hydrogel environments and suggest that stem or progenitor cells may not be fully necessary components in many tissue formations like those formed by vasculogenesis. ©2024 the Author(s)

关键词： Endothelial cells

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Rational Design of Phase-Engineered WS2/WSe2 Heterostructures by Low-Temperature Plasma-Assisted Sulfurization and Selenization toward Enhanced HER Performance

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ACS Applied materials and Interfaces 2024年第25期16卷 32490-32502页

作者： Rehman, Bushra Kimbulapitiya, K. Date, Manisha Chen, Chieh-Ting Cyu, Ruei-Hong Peng, Yu-Ren Chaudhary, Mayur Chuang, Feng-Chuan Chueh, Yu-Lun Department of Materials Science and Engineering National Tsing Hua University Hsinchu30013 Taiwan College of Semiconductor Research National Tsing Hua University Hsinchu30013 Taiwan Department of Physics National Sun Yat-Sen University Kaohsiung80424 Taiwan Department of Materials Science and Engineering Korea University Seoul02841 Korea Republic of

Efficient hydrogen generation from water splitting underpins chemistry to realize hydrogen economy. The electrocatalytic activity can be effectively modified by two-dimensional (2D) heterostructures, which offer great flexibility. Furthermore, they are useful in enhancing the exposure of the active sites for the hydrogen evolution reaction. Although the 1T-metallic phase of the transition metal dichalcogenides (TMDs) is important for the hydrogen evolution reaction (HER) catalyst, its practical application has not yet been much utilized because of the lack of stability of the 1T phase. Here, we introduce a novel approach to create a 1T-WS2/1T-WSe2 heterostructure using a low-temperature plasma-assisted chemical vapor reaction (PACVR), namely plasma-assisted sulfurization and plasma-assisted selenization processes. This heterostructure exhibits superior electrocatalytic performance due to the presence of the metallic 1T phase and the beneficial synergistic effect at the interface, which is attributed to the transfer of electrons from the underlying WS2 layer to the overlying WSe2 layer. The WS2/WSe2 heterostructure catalyst demonstrates remarkable performance in the HER as evidenced by its small Tafel slope of 57 mV dec-1 and exceptional durability. The usage of plasma helps in replacing the top S atoms with Se atoms, and this ion bombardment also increases the roughness of the thin film, thus adding another factor to enhance the HER performance. This plasma-synthesized low-temperature metallic-phase heterostructure brings out a novel method for the discovery of other catalysts. © 2024 The Authors. Published by American Chemical Society.

关键词： Selenium compounds

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Experimental measurements of the granular density of modes via impact

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Physical Review E 2024年第1期110卷 014902-014902页

作者： Sydney A. Blue Salem C. Wright Eli T. Owens Physics Department School of Materials Science and Engineering

The jamming transition is an important feature of granular materials, with prior work showing an excess of low-frequency modes in the granular analog to the density of states, the granular density of modes. In this work, we present an experimental method for acoustically measuring the granular density of modes using a single impact event to excite vibrational modes in an experimental, three-dimensional, granular material. We test three different granular materials, all of which are composed of spherical beads. The first two systems are monodisperse collections of either 6 mm or 8 mm diameter beads. The third system is a bidisperse mixture of the previous two bead sizes. During data collection, the particles are confined to a box; on top of this box, and resting on the granular material, is a light, rigid sheet onto which pressure can be applied to the system. To excite the material, a steel impactor ball is dropped on top of the system. The response of the granular material to the impact pulse is recorded by piezoelectric sensors buried throughout the material, and the density of modes is computed from the spectrum of the velocity autocorrelation of these sensors. Our measurements of the density of modes show more low-frequency modes at low pressure, consistent with previous experimental and numerical results, as well as several low-frequency peaks in the density of modes that shift with applied pressure. Our method represents an experimentally simple technique for investigating the granular density of modes and may increase the accessibility and number of such measurements.

关键词： Density of states Jamming Mechanical & acoustical properties Packing & jamming problems Dry granular materials

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Catalytically active atomically thin cuprate with periodic Cu single sites

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National science Review 2023年第1期10卷 226-235页

作者： Huimin Yang Shibo Xi Na Guo Mu Wang Lingmei Liu Pin Lyu Xiaolong Yu Jing Li Haomin Xu Xiao Hai Zejun Li Xinzhe Li Tao Sun Xiaoxu Zhao Yu Han Wei Yu Jie Wu Chun Zhang Honghan Fei Ming Joo Koh Jiong Lu Department of Chemistry National University of Singapore Institute of Chemical and Engineering Sciences Department of Physics National University of Singapore Advanced Membranes and Porous Materials Center King Abdullah University of Science and Technology SDU-ANU Joint Science College Shandong University School of Materials Science and Engineering Peking University Centre for Advanced 2D Materials and Graphene Research Centre National University of Singapore Department of Chemistry Tongji University

Rational design and synthesis of catalytically active two-dimensional（2D） materials with an abundance of atomically precise active sites in their basal planes remains a great ***,we report a ligand exchange strategy to exfoliate bulk [Cu4（OH）6] [O3S（CH2）4SO3] cuprate crystals into atomically thin 2D cuprate layers([Cu2（OH）3]+).The basal plane of 2D cuprate layers contains periodic arrays of accessible unsaturated Cu（Ⅱ） single sites（2D-CuSSs）,which are found to promote efficient oxidative Chan-Lam *** me chanistic studies reveal that the reactions proceed via coordinatively unsaturated CuO4（Ⅰ） single sites with the formation of Cu（Ⅰ） species in the rate-limiting step,as corroborated by both operando experimental and theoretical *** robust stability of 2D-CuSSs in both batch and continuous flow reactions,coupled with their recyclability and good performance in complex molecule derivatization,render 2D-CuSSs attractive catalyst candidates for broad utility in fine chemical synthesis.

关键词： exfoliation nanosheet heterogeneous catalysis

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Realization of a quadrupole topological insulator phase in a gyromagnetic photonic crystal

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National science Review 2024年第11期11卷 47-53页

作者： Peiheng Zhou Gui-Geng Liu Zihao Wang Shuwei Li Qindong Xie Yunpeng Zhang Subhaskar Mandal Xiang Xi Zhen Gao Longjiang Deng Baile Zhang National Engineering Research Center of Electromagnetic Radiation Control Materials Key Laboratory of Multi-spectral Absorbing Materials and Structures of Ministry of EducationUniversity of Electronic Science and Technology of China Division of Physics and Applied Physics School of Physical and Mathematical Sciences Nanyang Technological University School of Electrical Engineering and Intelligentization Dongguan University of Technology Department of Electronic and Electrical Engineering Southern University of Science and Technology Centre for Disruptive Photonic Technologies The Photonics InstituteNanyang Technological University

The field of topological photonics was initiated with the realization of a Chern insulator phase in a gyromagnetic photonic crystal(Ph C) with broken time-reversal symmetry(T), hosting chiral edge states that are topologically protected propagating modes. Along a separate line of research, a quadrupole topological insulator was the first higher-order topological phase supporting localized corner states, but has been so far limited to T-invariant systems, as T is a key ingredient in early models. Here we report the realization of a quadrupole topological insulator phase in a gyromagnetic Ph C, as a consequence of topological phase transition from the previously demonstrated Chern insulator phase. The phase transition has been demonstrated with microwave measurements, which characterize the evolution from propagating chiral edge states to localized corner states. We also demonstrate the migration of topological boundary states into the continuum, when the gyromagnetic Ph C is magnetically tuned. These results extend the quadrupole topological insulator phase into T-broken systems, and integrate topologically protected propagating and localized modes in a magnetically tunable photonic crystal platform.

关键词： quadrupole topological insulator time-reversal symmetry breaking corner states topological phase transition

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Advances of machine learning in materials science: Ideas and techniques

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Frontiers of physics 2024年第1期19卷 155-194页

作者： Sue Sin Chong Yi Sheng Ng Hui-Qiong Wang Jin-Cheng Zheng Department of New Energy Science and Engineering Xiamen University MalaysiaSepang 43900Malaysia Engineering Research Center of Micro-nano Optoelectronic Materials and Devices Ministry of EducationFujian Key Laboratory of Semiconductor Materials and ApplicationsCI Center for OSEDand Department of PhysicsXiamen UniversityXiamen 361005China

In this big data era, the use of large dataset in conjunction with machine learning (ML) has been increasingly popular in both industry and academia. In recent times, the field of materials science is also undergoing a big data revolution, with large database and repositories appearing everywhere. Traditionally, materials science is a trial-and-error field, in both the computational and experimental departments. With the advent of machine learning-based techniques, there has been a paradigm shift: materials can now be screened quickly using ML models and even generated based on materials with similar properties;ML has also quietly infiltrated many sub-disciplinary under materials science. However, ML remains relatively new to the field and is expanding its wing quickly. There are a plethora of readily-available big data architectures and abundance of ML models and software;The call to integrate all these elements in a comprehensive research procedure is becoming an important direction of material science research. In this review, we attempt to provide an introduction and reference of ML to materials scientists, covering as much as possible the commonly used methods and applications, and discussing the future possibilities.

关键词： machine learning materials science

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Accurate prediction of oxygen vacancy concentration with disordered A-site cations in high-entropy perovskite oxides

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npj Computational materials 2023年第1期9卷 2053-2065页

作者： Jiyun Park Boyuan Xu Jie Pan Dawei Zhang Stephan Lany Xingbo Liu Jian Luo Yue Qi School of Engineering Brown UniversityProvidenceRI 02912USA Department of Physics Brown UniversityProvidenceRI 02912USA Department of Chemical Engineering and Materials Science Michigan State UniversityEast LansingMI 48824USA Program of Materials Science and Engineering University of California San DiegoLa JollaCA 92093USA Materials Science Center National Renewable Energy LaboratoryGoldenCO 80401USA Department of Mechanical and Aerospace Engineering Benjamin M.Statler College of Engineering and Mineral ResourcesWest Virginia UniversityMorgantownWV 26506USA Department of NanoEngineering University of California San DiegoLa JollaCA 92093USA

Entropic stabilized ABO_(3) perovskite oxides promise many applications,including the two-step solar thermochemical hydrogen(STCH)*** binary and quaternary A-site mixed{A}FeO_(3) as a model system,we reveal that as more cation types,especially above four,are mixed on the A-site,the cell lattice becomes more cubic-like but the local Fe–O octahedrons are more *** comparing four different Density Functional Theory-informed statistical models with experiments,we show that the oxygen vacancy formation energies(E^(f)_(V))distribution and the vacancy interactions must be considered to predict the oxygen non-stoichiometry(δ)*** STCH applications,the E^(f)_(V) distribution,including both the average and the spread,can be optimized jointly to improveΔδ(difference ofδbetween the two-step conditions)in some hydrogen production *** model can be used to predict the range of water splitting that can be thermodynamically improved by mixing cations in{A}FeO_(3) perovskites.

关键词： perovskite vacancy oxides

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Improving the electro-optical properties of cholesteric liquid crystal devices via cellulose nanoparticle dopants

Polymer Journal

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Polymer Journal 2024年第5期56卷 541-551页

作者： Kuo, Chung-Yu Emelyanenko, A.V. Hung, Sheng-Chi Chen, Wei-Chuan Liu, Chun-Yen Department of Materials Science and Engineering National Cheng Kung University Tainan701401 Taiwan Faculty of Physics Lomonosov Moscow State University Moscow119991 Russia

In the presence of a strong electric field, helices in a cholesteric liquid crystal (CLC) phase might be unwound, leaving liquid crystal (LC) molecules parallel to the electric field, thereby realizing transparency. Previously, we developed a novel particle-doped CLC cell without alignment layers that exhibited liquid crystal display (LCD) capabilities via electro-optical properties. This ability represents a novel advancement in LCD fabrication, resulting in enhanced electro-optical characteristics. To explore the impact of chirality on LCDs, we synthesized and radially constructed cellulose particles. These were then employed as chiral dopants in the production of LCD cells. The fabricated chiral nanoparticle (CNP)-doped PC05 CLC cell showed a high transparency of 97.4% and a fast response time of 7.6 ms. For the prepared radially constructed PDAT-doped PD2T PSCLC cell, a high transmittance of 93.6% and a fast response time of 13 ms were achieved. Fabrication of LCD cells without an alignment layer on substrates was achieved by indicate adding polymeric chiral nanoparticles into CLC mixtures. Adding 2 wt% chiral CNPs promoted the transmittance of the CLCs from 3.4 to 97%. This novel chiral dopant technique enables the use of a new easy method for the fabrication of LCDs. © The Author(s), under exclusive licence to The Society of Polymer science, Japan 2024.

关键词： Cholesteric liquid crystals

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