1,225 research outputs found
In-situ growth of superconducting NdFeAs(O,F) thin films by Molecular Beam Epitaxy
The recently discovered high temperature superconductor F-doped LaFeAsO and
related compounds represent a new class of superconductors with the highest
transition temperature (Tc) apart from the cuprates. The studies ongoing
worldwide are revealing that these Fe-based superconductors are forming a
unique class of materials that are interesting from the viewpoint of
applications. To exploit the high potential of the Fe-based superconductors for
device applications, it is indispensable to establish a process that enables
the growth of high quality thin films. Efforts of thin film preparation started
soon after the discovery of Fe-based superconductors, but none of the earlier
attempts had succeeded in an in-situ growth of a superconducting film of
LnFeAs(O,F) (Ln=lanthanide), which exhibits the highest Tc to date among the
Fe-based superconductors. Here, we report on the successful growth of
NdFeAs(O,F) thin films on GaAs substrates, which showed well-defined
superconducting transitions up to 48 K without the need of an ex-situ heat
treatment
Efficient decoherence-free entanglement distribution over lossy quantum channels
We propose and demonstrate a scheme for boosting up the efficiency of
entanglement distribution based on a decoherence-free subspace (DFS) over lossy
quantum channels. By using backward propagation of a coherent light, our scheme
achieves an entanglement-sharing rate that is proportional to the transmittance
T of the quantum channel in spite of encoding qubits in multipartite systems
for the DFS. We experimentally show that highly entangled states, which can
violate the Clauser-Horne-Shimony-Holt inequality, are distributed at a rate
proportional to T.Comment: 5pages, 5figure
Formation of Deeply Bound Kaonic Atoms in (K^-,N) Reactions
We study theoretically the (K^-,N) reactions for the formation of the deeply
bound kaonic atoms, which were predicted to be quasi--stable with narrow
widths, using the Green function method. We consider various cases with
different target nuclei and energies systematically and find the clear signals
in the theoretical spectra for all cases considered in this article. The
signals show very interesting structures, such as the instead
of the resonance peak. We discuss the origins of the interesting structures and
possibilities to get new information on the existence of the kaonic nuclei from
the spectra of the atomic state formations.Comment: 11 pages, 9 figure
Single grain (LRE)-Ba-Cu-O superconductors fabricated by top seeded melt growth in air
We have recently reported a practical processing method for the fabrication in air of large, single grain (LRE)-Ba-Cu-O [where LRE Nd, Sm, Eu and Gd] bulk superconductors that exhibit high Tc and high Jc. The process is based initially on the development of a new type of generic seed crystal that can promote effectively the epitaxial nucleation of any (RE)-Ba-Cu-O system and, secondly, by suppressing the formation of (LRE)/Ba solid solution in a controlled manner within large LRE-Ba-Cu-O grains processed in air. In this paper we investigate the degree of homogeneity of large grain Sm-Ba-Cu-O superconductors fabricated by this novel process. The technique offers a significant degree of freedom in terms of processing parameters and reproducibility in the growth of oriented single grains in air and yields bulk samples with significantly improved superconducting and field-trapping properties compared to those processed by conventional top seeded melt growth (TSMG)
Momentum dependence of the energy gap in the superconducting state of optimally doped Bi2(Sr,R)2CuOy (R=La and Eu)
The energy gap of optimally doped Bi2(Sr,R)2CuOy (R=La and Eu) was probed by
angle resolved photoemission spectroscopy (ARPES) using a vacuum ultraviolet
laser (photon energy 6.994 eV) or He I resonance line (21.218 eV) as photon
source. The results show that the gap around the node at sufficiently low
temperatures can be well described by a monotonic d-wave gap function for both
samples and the gap of the R=La sample is larger reflecting the higher Tc.
However, an abrupt deviation from the d-wave gap function and an opposite R
dependence for the gap size were observed around the antinode, which represent
a clear disentanglement between the antinodal pseudogap and the nodal
superconducting gap.Comment: Submitted as the proceedings of LT2
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