Results 1 - 10 of 38506
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[en] The conditions for zero-energy Andreev surface bound states to exist are found for the lattice model of d-wave superconductor with arbitrary surface orientation. Both nearest neighbors and next nearest neighbors models are considered. It is shown that the results are very sensitive to the surface orientation. In particular, for half-filled (hl0)-surface zero-energy Andreev surface states only appear under the condition that h and l are odd simultaneously
[ru]Найдены условия существования связанных состояний на поверхности Андреева нулевой энергии для решеточной модели d-волнового сверхпроводника с произвольной ориентацией поверхности. Рассматриваются различные варианты этой модели. Показана сильная зависимость полученных результатов от ориентации поверхности. В частности, определено условие появления связанных состояний поверхности Андреева нулевой энергии в зависимости от значений параметров этой поверхности
[en] Optical Feshbach resonance can induce spatially varying interactions in ultra-cold atoms. Its applications to pancake-shaped clouds of bosons and fermions enable one to study several fresh phenomena. We examine possibilities of unexplored structures such as a bosonic superfluid enclave inside a Mott insulator and a normal-gas core enclosed by a fermionic superfluid shell. We discuss feasible experimental setups and signatures of those interesting structures. While a superfluid enclave in a Mott insulator may be useful for atomic devices in atomtronics, the superconducting islands observed in scanning–tunneling microscopy of heavily underdoped high-temperature superconductors may be simulated by ultra-cold fermions. -- Highlights: ► Optical Feshbach resonance is a key technique for generating new structures. ► Bosons can have a superfluid enclave in a Mott insulator. ► Fermions can have a normal-Fermi-gas core enclosed by a superfluid. ► We propose possible experimental setups and signatures. ► Spatially varying interactions enable cold-atoms to simulate other quantum systems.
[en] A novel configuration for adjusting the relative position of transmission zeros (TZs) based on the cascaded quartet (CQ) structure filter is proposed. By simply introducing joint cross coupling (JCC) between two adjacent CQ units of the filter and changing its coupling strength, the relative position of TZs produced by the conventional CQ units can be altered easily so as to achieve better selectivity and out-of-band rejection. The filter with the proposed configuration is named a quasi-CQ (QCQ) configuration filter in this paper. The symmetrical QCQ configuration filter can obtain the frequency response of the asymmetrical filter, so the design difficulty of filters with multiple pairs of separated TZs is greatly reduced. A series of prototypes of QCQ configuration filters is given and analyzed to provide design guidance for designers in the future. Finally, the correctness and feasibility of the proposed approach are verified by fabricating and measuring a symmetrical high-temperature superconducting QCQ configuration filter, and the test results accord well with the simulated ones. (paper)
[en] In the framework of valence electrons collectivization theory, estimates of characteristic pressure values, which can cause superconductivity of hydrogen compounds (hydrides) at elevated temperatures up to room temperature, are made. The calculated values are compared with experimental data obtained in the study of compounds LaH10: Tc ≈ 250 K, P ≈ 170 GPa. (author)
[en] A prototype of a high temperature superconducting (HTS) transceiver sub-system for applications in a TD-SCDMA, one of the third generation (3G) communication standards, base station has been developed. Both the HTS sub-system and the conventional counterpart have been implemented into a TD-SCDMA commercial communication network and comparison test studies were carried out. The measured results showed that the HTS sub-system could remarkably improve the RF performance of both transmitting and receiving chains.
[en] We present a method for characterizing the propagation of the magnetic flux in an artificially drilled bulk high-temperature superconductor (HTS) during pulsed-field magnetization. As the magnetic pulse penetrates the cylindrical sample, the magnetic flux density is measured simultaneously in 16 holes by means of microcoils that are placed across the median plane, i.e. at an equal distance from the top and bottom surfaces, and close to the surface of the sample. We discuss the time evolution of the magnetic flux density in the holes during a pulse and measure the time taken by the external magnetic flux to reach each hole. Our data show that the flux front moves faster in the median plane than on the surface when penetrating the sample edge; it then proceeds faster along the surface than in the bulk as it penetrates the sample further. Once the pulse is over, the trapped flux density inside the central hole is found to be about twice as large in the median plane as on the surface. This ratio is confirmed by modelling.
[en] In the present work we theoretically investigate density-wave propagation in a superconducting medium, consisting of a finite number of layers. An electromagnetic wave interacts with superconducting electrons to set up charge-density gradients within the superconducting electron plasma. We use the London equations and a two fluid approach along with a Kronig-Penney model to describe the layered medium, in order to investigate the density wave behaviour by deriving a linear dispersion relation. It is shown that the charge density wave dissipates gradually. We numerically investigate the dependence of the complex Bloch-wave number on the propagation frequency using the standard boundary conditions of the Kronig-Penney model. Expressions of reflectivity and transmissivity are derived for a periodic layered structure consisting of a finite number of superconducting layers; these quantities are investigated numerically for a high temperature superconductor and their dependence on background parameters is discussed. (author)