Journal of Physics: Condensed Matter最新文献

{"title":"Polarizability, plasmons and damping in pseudospin-1 gapped materials with a flat band.","authors":"Liubov Zhemchuzhna, Andrii Iurov, Godfrey Gumbs, Danhong Huang","doi":"10.1088/1361-648X/ad9c0a","DOIUrl":"10.1088/1361-648X/ad9c0a","url":null,"abstract":"<p><p>The subject of our present investigation is the collective electronic properties of various types of pseudospin-1 Dirac-cone materials with a flat band and finite bandgaps in their low-energy spectra. Specifically, we have calculated the dynamical polarization, plasmon dispersions, as well as their decay rates due to Landau damping and presented the closed-form analytical expressions for the wave function overlaps for both the gapped dice lattice and the Lieb lattice. The gapped dice lattice is a special case of the more general<i>α</i>-T3model such that its band structure is symmetric and the flat band remains dispersionless. On the other hand, the Lieb lattice has a flat band which appears at the lowest point of its conduction band. Our results for these two materials exhibit unique features in the plasmon spectra and their damping regions, which have never been previously reported. For example, the particle-hole modes of a Lieb lattice appear as finite-size regions, while the plasmon modes exist only in areas with small wave numbers but an extended range of frequencies.</p>","PeriodicalId":16776,"journal":{"name":"Journal of Physics: Condensed Matter","volume":" ","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142801214","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Unveiling the impact of Ni doping on the structural, electronic, and magnetic properties of nanocrystalline FeCo₂O₄spinel oxide: a combined experimental and<i>ab initio</i>investigations.","authors":"Deepak Verma, Tulika Maitra, G D Varma","doi":"10.1088/1361-648X/ad9af2","DOIUrl":"10.1088/1361-648X/ad9af2","url":null,"abstract":"<p><p>In the present work, nanocrystalline samples of compositionsNixFe1-xCo2O4(x= 0.0, 0.25, 0.50, and 0.75) have been synthesized via co-precipitation method by annealing at 900 °C. The nanocrystalline samples of compositions Ni_0.25Fe_0.75Co₂O₄(D_0.25) and Ni_0.5Fe_0.5Co₂O₄(D_0.5) crystallizes in a pure spinel phase, whereas Ni_0.75Fe_0.25Co₂O₄(D_0.75) show the existence of secondary phase of NiO, as confirmed by the x-ray diffraction analysis. The particle size and lattice strain in the samples both decrease as Ni substitution has increased. The field-dependent dc magnetization<i>M</i>(<i>H</i>) virgin curve measured at 5 K for sample D_0.75shows the existence of field-induced metamagnetic transition, while this behavior is absent in samples D_0.5and D_0.25. Dynamic magnetic properties have been investigated by ac susceptibility measurement, which shows a strong frequency dependence behavior resulting from the blocking/spin-glass freezing states depending upon the amount of Ni substitution and the range of measurement temperature. High-resolution x-ray photoelectron spectroscopy analysis reveals the presence of mixed valence states of Fe²⁺/Fe³⁺, Co²⁺/Co⁺³, and Ni²⁺/Ni⁺³in all samples. Using first principles-based density functional theory calculations with HSE06 exchange-correlation functional predicts the correct description of the ground state, which is ferrimagnetic and insulating in their inverse spinel case for D_0.25, D_0.5, and D_0.75samples that agreed well with our experimental observations. A closer look at the electronic structure near the Fermi level (<i>E</i>_F) of Ni-doped samples suggests a typical Mott-Hubbard insulating state while it is found to be a mixture of charge-transfer and Mott-Hubbard insulating state for parent compound FeCo₂O₄. The obtained spin-dependent gap hierarchy can have possible applications in spintronics. We have studied a detailed correlation between experiment and theory.</p>","PeriodicalId":16776,"journal":{"name":"Journal of Physics: Condensed Matter","volume":" ","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142785714","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Crossover in atomic mobility underlying the glass transition in inorganic glasses.","authors":"Cillian Cockrell, Robin W Grimes","doi":"10.1088/1361-648X/ad9fc8","DOIUrl":"https://doi.org/10.1088/1361-648X/ad9fc8","url":null,"abstract":"<p><p>While the glass transition is easy to identify macroscopically, the underlying atomic mechanisms which facilitate the transition from amorphous solid to fluid are still poorly understood. We conduct classical molecular dynamics simulations on a variety of inorganic glasses in order to identify these mechanisms. While also modelling larger systems, we find that the essential qualities which constitute a glass and its transition to a liquid are present even in systems containing only a few hundred atoms. The transition is therefore a local phenomenon. Atomic mobility, the ability of an atom to escape its local coordination environment, is identified as a universal marker of the glass transition. In the solid state, the fraction of mobile atoms is mobile, whereas in the liquid state, effectively all atoms are mobile. The glass transition is continuous between these limiting states, with half of the network forming atoms attaining mobility exactly at the glass transition temperature, over a specific mobility half life, informed by thermodynamics. Over time, network forming atoms which were immobile may swap to become mobile and vice versa, though the population of mobile atoms remains a half.</p>","PeriodicalId":16776,"journal":{"name":"Journal of Physics: Condensed Matter","volume":" ","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142835773","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Disorder-induced phase transitions in a two-dimensional magnetic topological insulator system.","authors":"YongLiang Song, Shu-Xiu Shang, Xinlian Chen, C W Zhang, Shu-Feng Zhang","doi":"10.1088/1361-648X/ad9fc9","DOIUrl":"https://doi.org/10.1088/1361-648X/ad9fc9","url":null,"abstract":"<p><p>We investigate the phase diagram of a two-dimensional magnetic topological system in the pa&#xD;rameter space of uncorrelated Anderson disorder and Zeeman splitting energy. In the absence of&#xD; disorder, the system undergoes the phases of higher-order topological insulators (HOTIs), Chern&#xD; insulators (CIs) with Chern numbers C = 2 and C = 1, and band insulators successively with&#xD; enhancing Zeeman energy. The phase boundary separating these phases is found to be strongly&#xD; deformed by the disorder, which leads to several topological Anderson insulators. Specifically, there&#xD; exist phase transitions between CI with C = 2 and HOTI, and between CIs with C = 1 and C = 2.&#xD; For the former one, it is in fact a phase transition between first-order and second-order topological&#xD; phases. Besides, these disorder induced phase transitions are well explained by self-consistent Born&#xD; approximation.</p>","PeriodicalId":16776,"journal":{"name":"Journal of Physics: Condensed Matter","volume":" ","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142835974","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Quasi-one-dimensional alternating spin-1/2 antiferromagnetism in perovskite metal formate framework [(NH₂)₂CH]Cu(HCOO)₃.","authors":"Ying Li, Jie Wang, Yuke Li, Hanjie Guo, Xing-Liang Xu, Xing'ao Li","doi":"10.1088/1361-648X/ad9b61","DOIUrl":"10.1088/1361-648X/ad9b61","url":null,"abstract":"<p><p>The formamidinium copper formate [(NH₂)₂CH]Cu(HCOO)₃(FMD-Cu) with a perovskite-like structure based on a nonporous metal-organic framework (MOF), is presented for its synthesis and magnetic properties. The magnetic properties and their couplings to the structure are derived from detailed magnetic susceptibility and heat capacity measurements. We also discuss the spin exchange couplings based on density functional theory (DFT) calculations. As a result, FMD-Cu exhibits the unusual quasi-one-dimensional antiferromagnetic (AFM) characteristics with the Néel temperature<i>T</i>_N= 12.0 K and an intrachain coupling constant<i>J</i>/<i>k</i>_B≈ 76.3 K. We also estimate the effective interchain coupling<i>J</i>^*/<i>k</i>_B≈ 4.24 K, suggesting that FMD-Cu is close to an ideal candidate for one-dimensional magnet. Furthermore, the heat capacity shows a transition to an antiferromagnetic ordering state appears around<i>T</i>_N. Besides, the nonzero parameter<i>γ</i>= 0.089 J mol^-1K^-1obtained from the linear relationship,<i>γT</i>, to the low temperature-dependent zero-field heat capacity data, can be associated with the magnetic excitations in insulating quasi-one-dimensional AFM Heisenberg spin-1/2 chains. The experimental estimate and DFT calculations are entirely consistent with a model of FMD-Cu in which AFM exchange interactions originating from Jahn-Teller distortion of the Cu²⁺(3<i>d</i>⁹) ions, leaving a sublattice of coupled ferromagnetic (FM) chains. Hence, FMD-Cu is proposed as a canonical model of a quasi-one-dimensional Heisenberg spin-1/2 antiferromagnetic material.</p>","PeriodicalId":16776,"journal":{"name":"Journal of Physics: Condensed Matter","volume":" ","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142791861","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A symmetry-oriented crystal structure prediction method for crystals with rigid bodies.","authors":"Q I Zhang, Amitava Choudhury, Aleksandr V Chernatynskiy","doi":"10.1088/1361-648X/ad9f07","DOIUrl":"https://doi.org/10.1088/1361-648X/ad9f07","url":null,"abstract":"<p><p>We have developed an efficient crystal structure prediction (CSP) method for desired chemical compositions, specifically suited for compounds featuring recurring molecules or rigid bodies. We applied this method to two metal chalcogenides: Li₃PS₄and Na₆Ge₂Se₆, treating PS₄as a tetrahedral rigid body and Ge₂Se₆as an ethane-like dimer rigid body. Initial trials not only identified the experimentally observed structures of these compounds but also uncovered several novel phases, including a new stannite-type Li₃PS₄structure and a potential metastable structure for Na₆Ge₂Se₆that exhibits significantly lower energy than the observed phase, as evaluated by density functional theory (DFT) calculations. We compared our results with those obtained using USPEX, a popular CSP package leveraging genetic algorithms. Both methods predicted the same lowest energy structures in both compounds. However, our method demonstrated better performance in predicting metastable structures. The method is implemented with Python code which is available at https://github.com/ColdSnaap/sgrcsp.git.</p>","PeriodicalId":16776,"journal":{"name":"Journal of Physics: Condensed Matter","volume":" ","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142821818","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A high-dimensional neural network potential for Co₃O₄.","authors":"Amir Omranpour, Jörg Behler","doi":"10.1088/1361-648X/ad9f09","DOIUrl":"https://doi.org/10.1088/1361-648X/ad9f09","url":null,"abstract":"<p><p>The Co3O4 spinel is an important material in oxidation catalysis. Its properties under catalytic conditions, i.e., at finite temperatures, can be studied by molecular dynamics simulations, which critically depend on an accurate description of the atomic interactions. Due to the high complexity of Co3O4, which is related to the presence of multiple oxidation states of the cobalt ions, to date ab initio methods have been essentially the only way to reliably capture the underlying potential energy surface, while more efficient atomistic potentials are very challenging to construct. Consequently, the accessible length and time scales of computer simulations of systems containing Co3O4 are still severely limited. Rapid advances in the development of modern machine learning potentials (MLPs) trained on electronic structure data now make it possible to bridge this gap. In this work, we employ a high-dimensional neural network potential (HDNNP) to construct a MLP for bulk Co3O4 spinel based on density functional theory calculations. After a careful validation of the potential, we compute various structural, vibrational, and dynamical properties of the Co3O4 spinel with a particular focus on its temperature-dependent behavior, including the thermal expansion coefficient.</p>","PeriodicalId":16776,"journal":{"name":"Journal of Physics: Condensed Matter","volume":" ","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142822290","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Structural Evolution and Electronic Properties of Neutral Boron-Doped Nitrogen Clusters.","authors":"Meicheng Chen, Shu Huang, Peixin Fu, Bole Chen, Chen Chen, Jie Bi, Kewei Ding, Cheng Lu","doi":"10.1088/1361-648X/ad9f0b","DOIUrl":"https://doi.org/10.1088/1361-648X/ad9f0b","url":null,"abstract":"<p><p>Clusters represent intermediate states between isolated atoms and bulk solids. They serve as model systems to elucidate the physical properties of compounds from the atomic or molecular scale to the macroscopic bulk phase. Here, we perform thorough structure searches of neutral boron doped nitrogen clusters by Crystal structural anaLYsis by Particle Swarm Optimization (CALYPSO) cluster structural prediction and density functional theory (DFT) calculations. The calculated results indicate that the ground state structures of BNn (n = 4-16) clusters are evolutional from one-dimensional (1D) chains to two dimensional (2D) rings, and finally to three-dimensional (3D) geometries. Interestingly, the intriguing BN12 cluster, characterized by a 3D configuration with a central boron atom connecting four N3 chains in distinct directions, exhibits exceptional stability. The chemical bonding analysis reveals that the outstanding stability of BN12 cluster is attributed to the strong σ and π interactions between the 2p orbitals of the boron atom and the surrounding nitrogen atoms, as well as the robust σ bonds along the four nitrogen chains. The present findings offer important insights for understanding the geometries and electronic properties of neutral boron doped nitrogen clusters and provide an avenue for the design and synthesis of nitrogen-rich compounds.&#xD.</p>","PeriodicalId":16776,"journal":{"name":"Journal of Physics: Condensed Matter","volume":" ","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142822093","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Topology and PT Symmetry in a Non-Hermitian Su-Schrieffer-Heeger Chain with Periodic Hopping Modulation.","authors":"Surajit Mandal, Satyaki Kar","doi":"10.1088/1361-648X/ad9f08","DOIUrl":"https://doi.org/10.1088/1361-648X/ad9f08","url":null,"abstract":"<p><p>We study the effect of periodic hopping modulation in a Su-Schrieffer-Heeger (SSH) chain with&#xD;an additional onsite staggered imaginary potential (of strength γ). Such dissipative, non-Hermitian&#xD;(NH) extension amply modifies the features of the topological trivial phase (TTP) and the topo-&#xD;logical nontrivial phase (TNP) of the SSH chain, more so with the periodic hopping distribution.&#xD;Generally a weak NH potential can respect the parity-time (PT ) symmetry keeping the energy&#xD;eigenvalues real, while a strong potential breaks PT conservation leading to imaginary edge state&#xD;and complex bulk state energies in the system. We find that the non-zero energy in-gap states,&#xD;that appear due to periodic hopping modulations even in the γ = 0 limit, take purely real or purely&#xD;imaginary eigenvalues depending on the strength of both γ and ∆ (dimerization parameter). The&#xD;localization of topological edge states (in-gap states) at the boundaries are investigated that reveals&#xD;extended nature not only near topological transitions (further away from |∆/t| = 1) but also near&#xD;the unmodulated limit of ∆ = 0. Moreover, localization of the bulk states is observed at the max-&#xD;imally dimerized limit of |∆/t| = 1, which increases further with γ. These dissipative features can&#xD;offer additional tunability in modulating the gain-loss contrast in optical systems or in designing&#xD;various quantum information processing and storage devices.</p>","PeriodicalId":16776,"journal":{"name":"Journal of Physics: Condensed Matter","volume":" ","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142822104","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Harnessing orbital and valley thermal transport in 2D materials: The significance of inversion symmetry.","authors":"Shivam Sharma, Abir De Sarkar","doi":"10.1088/1361-648X/ad9f0a","DOIUrl":"https://doi.org/10.1088/1361-648X/ad9f0a","url":null,"abstract":"<p><p>Orbitronics and valleytronics, analogous to spintronics, leverage the&#xD;orbital degree of freedom and the valley degree of freedom of electrons to carry&#xD;information, promising significant advancements in information processing. In&#xD;this study, we disentangle the orbital and valley Nernst effect in 2D monolayers,&#xD;based on the global symmetry of the monolayers. We conduct an in-depth&#xD;analysis of the orbital (valley) Nernst effect in inversion symmetric (asymmetric)&#xD;monolayers, using an analytical tight binding model. Furthermore, we elucidate&#xD;the dependence of the two effects on various inherent materials' parameters using&#xD;the prototypical Kane-Mele model. Our calculations show that an inversion&#xD;symmetric gapped Kagome lattice shows a significant orbital Nernst effect&#xD;emerging from the interatomic contribution, even in the absence of both spin&#xD;and valley Nernst effects. Furthermore, for the inversion asymmetric 2H-phase&#xD;of TMDs, we elucidate that the valley degree of freedom encompasses the orbital&#xD;degree of freedom and the valley Nernst effect can be more accurately described&#xD;using the orbital degree of freedom, hence termed as the valley-orbital Nernst&#xD;effect.</p>","PeriodicalId":16776,"journal":{"name":"Journal of Physics: Condensed Matter","volume":" ","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142822082","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}