8,426 research outputs found

    Tuning Hole Mobility, Concentration, and Repulsion in High-TcT_c Cuprates via Apical Atoms

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    Using a newly developed first-principles Wannier-states approach that takes into account large on-site Coulomb repulsion, we derive the effective low-energy interacting Hamiltonians for several prototypical high-TcT_c superconducting cuprates. The material dependence is found to originate primarily from the different energy of the apical atom pzp_z state. Specifically, the general properties of the low-energy hole state, namely the Zhang-Rice singlet, are significantly modified by a triplet state associated with this pzp_z state, via additional intra-sublattice hoppings, nearest-neighbor "super-repulsion", and other microscopic many-body processes. Possible implications on modulation of TcT_c, local superconducting gaps, charge distribution, hole mobility, electron-phonon interaction, and multi-layer effects are discussed.Comment: 5 pages, 3 figures, 1 tabl

    Rapid algorithm for identifying backbones in the two-dimensional percolation model

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    We present a rapid algorithm for identifying the current-carrying backbone in the percolation model. It applies to general two-dimensional graphs with open boundary conditions. Complemented by the modified Hoshen-Kopelman cluster labeling algorithm, our algorithm identifies dangling parts using their local properties. For planar graphs, it finds the backbone almost four times as fast as Tarjan's depth-first-search algorithm, and uses the memory of the same size as the modified Hoshen-Kopelman algorithm. Comparison with other algorithms for backbone identification is addressed.Comment: 5 pages with 5 eps figures. RevTeX 3.1. Clarify the origin of the hull-generating algorith

    Joint Domain Based Massive Access for Small Packets Traffic of Uplink Wireless Channel

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    The fifth generation (5G) communication scenarios such as the cellular network and the emerging machine type communications will produce massive small packets. To support massive connectivity and avoid signaling overhead caused by the transmission of those small packets, this paper proposes a novel method to improve the transmission efficiency for massive connections of wireless uplink channel. The proposed method combines compressive sensing (CS) with power domain NOMA jointly, especially neither the scheduling nor the centralized power allocation is necessary in the method. Both the analysis and simulation show that the method can support up to two or three times overloading.Comment: 6 pages, 5 figures.submitted to globecom 201

    Unified Picture for Magnetic Correlations in Iron-Based Superconductors

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    The varying metallic antiferromagnetic correlations observed in iron-based superconductors are unified in a model consisting of both itinerant electrons and localized spins. The decisive factor is found to be the sensitive competition between the superexchange antiferromagnetism and the orbital-degenerate double-exchange ferromagnetism. Our results reveal the crucial role of Hund's rule coupling for the strongly correlated nature of the system and suggest that the iron-based superconductors are closer kin to manganites than cuprates in terms of their diverse magnetism and incoherent normal-state electron transport. This unified picture would be instrumental for exploring other exotic properties and the mechanism of superconductivity in this new class of superconductors.Comment: Revised for publication. 3 figure