2,376 research outputs found

    Theory for charge and orbital density-wave states in manganite La0.5_{0.5}Sr1.5_{1.5}MnO4_4

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    We investigate the high temperature phase of layered manganites, and demonstrate that the charge-orbital phase transition without magnetic order in La0.5_{0.5}Sr1.5_{1.5}MnO4_4 can be understood in terms of the density wave instability. The orbital ordering is found to be induced by the nesting between segments of Fermi surface with different orbital characters. The simultaneous charge and orbital orderings are elaborated with a mean field theory. The ordered orbitals are shown to be dx2y2±d3z2r2d_{x^2-y^2} \pm d_{3z^2-r^2}.Comment: published versio

    Electrical Detection of Ferroelectric-like Metals through Nonlinear Hall Effect

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    Ferroelectric-like metals are a relatively rare class of materials that have ferroelectric-like distortion and metallic conductivity. LiOsO3_3 is the first demonstrated and the most investigated ferroelectric-like metal. The presence of free carriers makes them difficult to be studied by traditional ferroelectric techniques. In this paper, using the symmetry analysis and first-principles calculations, we demonstrate that the ferroelectric-like transition of LiOsO3_3 can be probed by a kind of electrical transport method based on nonlinear Hall effect. The Berry curvature dipole exists in the ferroelectric-like phase, and it can lead to a measurable nonlinear Hall conductance with a conventional experimental setup. However, the symmetry of the paraelectric-like phase LiOsO3_3 vanishes the Berry curvature dipole. The Berry curvature dipole shows a strong dependence on the polar displacement, which might be helpful for the detection of polar order. The nonlinear Hall effect provides an effective method for the detection of phase transition in the study of the ferroelectric-like metals and promotes them to be applied in the ferroelectric-like electronic devices

    Electrical detection of ferroelectriclike metals through the nonlinear Hall effect

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    Ferroelectriclike metals are a relatively rare class of materials that have ferroelectriclike distortion and metallic conductivity. LiOsO3 is the first demonstrated and the most investigated ferroelectriclike metal. The presence of free carriers makes them difficult to be studied by traditional ferroelectric techniques. In this paper, using symmetry analysis and first-principles calculations, we demonstrate that the ferroelectriclike transition of LiOsO3 can be probed by a kind of electrical transport method based on nonlinear Hall effect. The Berry curvature dipole exists in the ferroelectriclike phase and it can lead to a measurable nonlinear Hall conductance with a conventional experimental setup. However, the symmetry of the paraelectriclike phase LiOsO3 vanishes the Berry curvature dipole. The Berry curvature dipole shows a strong dependence on the polar displacement, which might be helpful for the detection of polar order. The nonlinear Hall effect provides an effective method for the detection of phase transition in the study of the ferroelectriclike metals and promotes them to be applied in ferroelectriclike electronic devices

    Thermal Analysis and Characterization of Polystyrene Initiated by Benzoyl Peroxide

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    PresentationBased on the complexity of the polystyrene polymerization mechanism initiated by benzoyl peroxide (BPO), the thermal risk of the reaction process was estimated using thermal analysis and characterization. The polymerization process was thermally analysed using an adiabatic rate calorimeter and differential scanning calorimeter. The results demonstrated that the onset reaction temperature, adiabatic temperature rise, and maximum temperature of the synthesis reaction of BPO-initiated polymerization were lower than those of thermos initiated polymerization. Moreover, nuclear magnetic resonance imaging, gel permeation chromatography, and Fourier transform infrared spectrometry were used to characterize the polymerization products obtained under the two initiation conditions. The polystyrene obtained using the two initiation methods had the same hydrogen structure; however, their molecular weight and distribution uniformity differed considerably, and the BPO-initiated process was discovered to include the effects of the thermos initiated process. Moreover, the free radicals produced by BPO decomposition participated in the chain reaction of polystyrene polymerization, accelerated instantaneous grain growth, and promoted the formation of short- chain polystyrene. In summary, the BPO-initiated polymerization process exhibited the desired thermal safety characteristics and has potential for practical use

    Elucidating the surface geometric design of hydrophobic Australian Eucalyptus leaves: experimental and modeling studies

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    Three Australian native Eucalyptus species, i.e., Eucalyptus woodwardii, Eucalyptus pachyphylla and Eucalyptus dolorosa, were investigated, for the first time, with respect to the hydrophobicity of their leaves. It is well established that these leaves exhibit exceptionally high water repellency, in addition to an extraordinary ability to retain water, albeit their specific wetting mechanisms are still poorly understood. To identify the critical factors underlying this phenomenon, the surface topography of these leaves was subjected to micro-examination (SEM). Micro- and nanometer scale surface roughness was revealed, resembling that of the quintessential “lotus effect”. Surface free energy analysis was performed on two models based on the surface topographies of the study Eucalyptus species and lotus, in order to study wetting transitions on these specific microscopic surface features. The influence of surface geometrical parameters, such as edge-to-edge distance, base radius and cylindrical height, on surface free energy with different liquid penetration depths was studied with these two models. Larger energy barriers and smaller liquid-solid contact areas were more influential in the calculations for the lotus than for Eucalyptus. The information obtained from these two models may be useful for guiding the design of novel artificial surfaces in the collection and transport of micro-volume liquids. © 2019 The Author

    Reallocation of foliicolous species of the genus Strigula into six genera (lichenized Ascomycota, Dothideomycetes, Strigulaceae)

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    Strigula sensu lato has been previously defined based on phenotype characters as a rather broad genus including tropical to temperate species growing on a wide array of substrata. In this study, based on a multilocus phylogenetic approach, we show that foliicolous species form six well-delimited clades that correlate with diagnostic phenotype features, including thallus morphology, carbonization of the involucrellum and excipulum, ascospore dimensions, and type of macroconidia. Given the topology, with five of the six clades emerging on long stem branches, and the strong phenotypical differentiation between the clades, we recognize these at the genus level, making mostly use of previously established genus names. Four genera, namely Phylloporis, Puiggariella, Raciborskiella, and Racoplaca, are resurrected for the S. phyllogena, S. nemathora, S. janeirensis, and S. subtilissima groups, respectively, whereas one new genus, Serusiauxiella gen. nov., is introduced for a novel lineage with peculiar macroconidia. The only sequenced non-foliicolous species, S. jamesii, is not closely related to these six foliicolous lineages but clusters with Flavobathelium and Phyllobathelium, revealing it as an additional undescribed genus-level lineage being treated elsewhere. Within the new genus Serusiauxiella, three new species are described: Serusiauxiella filifera sp. nov., S. flagellata sp. nov., and S. sinensis sp. nov. In addition, ten new combinations are proposed: Phylloporis austropunctata comb. nov., P. radiata comb. nov., P. vulgaris comb. nov., Puiggariella confluens comb. et stat. nov., P. nemathora comb. nov., P. nigrocincta comb. nov., Racoplaca maculata comb. nov., R. melanobapha comb. nov., R. transversoundulata, and R. tremens comb. nov. We also report on a peculiar, previously unrecognized growth behaviour of the macroconidial appendages in Strigula s.lat
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