12,545 research outputs found

    SU(3) trimer resonating-valence-bond state on the square lattice

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    We propose and study an SU(3) trimer resonating-valence-bond (tRVB) state with C4vC_{4v} point-group symmetry on the square lattice. By devising a projected entangled-pair state representation, we show that all (connected) correlation functions between local operators in this SU(3) tRVB state decay exponentially, indicating its gapped nature. We further calculate the modular SS and TT matrices by constructing all nine topological sectors on a torus and establish the existence of Z3\mathbb{Z}_3 topological order in this SU(3) tRVB state.Comment: 6 pages, 6 figure

    Carabus (Coleoptera: Carabidae) assemblages of native forests and non-native plantations in Northern China

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    The effects of non-native plantation established after clear-cutting were studied in Dongling Mountain region, Northern China. Pitfall catches of Carabus beetles from a non-native larch plantation were compared with those from two native forests, an oak forest and a mixed broad-leaved forest. More individuals were captured from the mixed broad-leaved forest and the larch plantation than from the oak forest. For the threemost abundant species in this area, C. crassesculptus peaked in abundance in the mixed broad-leaved forest; C. manifestus peaked in the larch plantation, and C. sculptipennis in the oak forest. Measured by PcoAusing Bray-Curtis index of dissimilarity, species composition of the larch plantation was different from the two native forests, but overlapped remarkably with them. All the three abundant species showed a similar positive relationship between local distribution and abundance. Captures of abundant species were clumped within the forest, but the extent of aggregation among forests was different. Monthly catches of total Carabus, and C. crassesculptus alone, peaked in June–August in all the three forests, but C. manifestus peaked in June and again in August. Our results suggest that the planting of non-native larch does not have a detrimental effect on Carabus assemblages in general, but it changes the spatial distribution and abundance compared to the native forests

    Habitat associations and seasonal activity of carabid beetles (Coleoptera: Carabidae) in Dongling Mountain, North China

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    Habitat distribution and seasonal occurrence of carabid beetles were determined using pitfall traps in 1999 and 2000 in the temperate forest zone of the Dongling Mountain, North China. Eight sites differing in vegetation and moisture were selected so as to represent four habitat types. Carabid assemblages of the six forested habitats (lowland, upland and coppice) weremore similar to each other than to the two shrub assemblages. Lowland forest had the highest species richness, and coppice forest had the highest diversity (H’) and equitability (J). Of the 41 species caught, the 18 most abundant species were divided into four distribution types: habitat generalists, forest generalists, forest specialists, and shrub (or coppice) specialists. Mean catches of all beetles showed clear peaks from May to August in nearly all habitats. The catches of the six most abundant species were more or less positively correlated during the two study years, suggesting their similar habitat preferences

    Impurity resonance states in electron-doped high T_c superconductors

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    Two scenarios, i.e., the anisotropic s-wave pairing (the s-wave scenario) and the d-wave pairing coexisting with antiferromagnetism (the coexisting scenario) have been introduced to understand some of seemingly s-wave like behaviors in electron doped cuprates. We considered the electronic structure in the presence of a nonmagnetic impurity in the coexistence scenario. We found that even if the AF order opens a full gap in quasi-particle excitation spectra, the mid-gap resonant peaks in local density of states (LDoS) around an impurity can still be observed in the presence of a d-wave pairing gap. The features of the impurity states in the coexisting phase are markedly different from the pure AF or pure d-wave pairing phases, showing the unique role of the coexisting AF and d-wave pairing orders. On the other hand, it is known that in the pure s-wave case no mid-gap states can be induced by a nonmagnetic impurity. Therefore we proposed that the response to a nonmagnetic impurity can be used to differentiate the two scenarios.Comment: 5 pages, two-column revtex4, 5 figures, author list correcte
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