Results 1 - 10 of 14650
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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] In practical application of High-Tc Superconducting (HTS) maglev, slant is an observable defect. It was caused by constantly one side on and off the vehicle by passengers. So far, this phenomenon has not been reported yet. In order to understand its influence on the stability of the HTS maglev, we experimentally studied the dynamic characteristic and slant effect of HTS maglev under center-load and side-load. It was found that load destabilizes the vehicle, and the side-load can obviously slant the vehicle body. In the end, the pre-load method was proposed to enhance the dynamic stability and suppress the slant, which proved to be considerably effective. These results are critical in practical running of HTS maglev
[en] High temperature superconducting materials (HTS) offer several advantages in magnetic field shielding applications. HTS materials have the potential of creating efficient shields by reducing the size and weight of the shielding systems. The main limitation until recently has been the difficulty of producing HTS tapes of large width. Recent developments in second-generation (2G) high temperature YBCO superconductors allow the production of 2G films on very large 4 cm wide substrates. Magnetic field shielding properties of coils and sheets fabricated from 4 cm wide YBa2Cu3O7-coated conductors are reported. Shielding properties of shields with multiple layers were measured at liquid nitrogen temperatures. Magnetic field amplitude inside the superconducting shields was measured using Hall probes with a phase-sensitive technique. Efficacy of the shields was characterized at varying field amplitude and frequency. Shielding of up to 95% of applied magnetic field was observed at magnetic field amplitudes of <10 mT. The frequency dependence of shielding properties depended on the geometry of the shields.
[en] The Holy Grail for high temperature superconducting conductors is achieving high current material in a simple and cost-effective way. The current status is encouraging but even after more than twenty years of intense worldwide research, there are still many new avenues to be explored. Innovative functional oxide materials science is central to future progress. This paper discusses three key areas of our research focusing on new directions: highly tailored flux pinning using the new core pinning additives R3TaO7 and RBa2NbO6 for control of nanostructure formation; pinning using magnetic phase additives such as RFeO3 with the potential for a magnetic contribution to the flux pinning; and the use of liquid assisted growth enabling very high growth rates leading to thick films with no critical current degradation.
[en] The pulsed field magnetization of the short-circuited soldered double pancake coil made of stabilized commercial high-Tc superconductor (HTS) tape is experimentally studied. The evolution of the shielding current induced by the pulsed field and the trapped field after the pulsed magnetization was measured at 77 K. It is shown that the trapped field in the coil is close to the value reached in the field cooling process and reduces weakly at 5-fold increasing of pulsed field amplitude. The current relaxation at t⁓2 ms after the pulse is defined by the current sharing between the tape's copper coating and the YBa2Cu3O7-d layer. In the intermediate time scale (1 s < t < 100 s) the flux creep in HTS layer dominates. At t > 100 s the current’s relaxation is defined by the resistance of soldered joint between tapes
[en] This paper presents a model taking into account moving bodies. An electrodynamic device which consists of a magnet over a superconductor shall be examined. In order to determine the mechanical behaviour of the device a coupled solution of the electromagnetic and the mechanical problem is used. (orig.)
[en] As the complexity of strongly correlated systems and high temperature superconductors increases, so does also the essential complexity of defects found in these materials and the complexity of the supercurrent pathways. It can be therefore convenient to realize a solid-state system with regular supercurrent pathways and without the disguising effects of disorder in order to capture the essential characteristics of a collective dynamics. Using a square array of superconducting islands placed on a normal metal, we observe a state in which magnetic field-induced vortices are frozen in the dimples of the egg crate potential by their strong repulsion interaction. In this system a dynamic vortex Mott insulator transition has been previously observed. In this work, we will show the symmetric dynamic behaviour with respect to field reversal and we will compare it with the asymmetric behaviour observed at the dynamic vortex Mott transition. (paper)