8 research outputs found
The electronic state of vortices in YBa2Cu3Oy investigated by complex surface impedance measurement
The electromagnetic response to microwaves in the mixed state of
YBa2Cu3Oy(YBCO) was measured in order to investigate the electronic state
inside and outside the vortex core. The magnetic-field dependence of the
complex surface impedance at low temperatures was in good agreement with a
general vortex dynamics description assuming that the field-independent viscous
damping force and the linear restoring force were acting on the vortices. In
other words, both real and imaginary parts of the complex resistivity, \rho_1,
and \rho_2, were linear in B. This is explained by theories for d-wave
superconductors. Using analysis based on the Coffey-Clem description of the
complex penetration depth, we estimated that the vortex viscosity \eta at 10 K
was (4 \sim 5) \times 10^{-7} Ns/m^2. This value corresponds to \omega_0 \tau
\sim 0.3 - 0.5, where \omega_0 and \tau are the minimal gap frequency and the
quasiparticle lifetime in the vortex core, respectively. These results suggest
that the vortex core in YBCO is in the moderately clean regime. Investigation
of the moderately clean vortex core in high-temperature superconductors is
significant because physically new effects may be expected due to d-wave
characteristics and to the quantum nature of cuprate superconductors. The
behavior of Z_s as a function of B across the first order transition (FOT) of
the vortex lattice was also investigated. Unlike Bi2Sr2CaCu2Oy (BSCCO), no
distinct anomaly was observed around the FOT in YBCO. Our results suggest that
the rapid increase of X_s due to the change of superfluid density at the FOT
would be observed only in highly anisotropic two-dimensional vortex systems
like BSCCO. We discuss these results in terms of the difference of the
interlayer coupling and the energy scale between the two materials.Comment: 10 pages, 6 figures, to be published in Phys. Rev. B, one reference
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GATA2 Mutations in Pediatric Acute Myeloid Leukemia: A Study of the Japanese Childhood AML Cooperative Study Group.
Double Pion Photoproduction on Deuteron(I. Nuclear Physics)
Exclusive cross sections for double-pion photoproductions on proton and deuteron were measured in an energy range from 0.8 to 1.1GeV using tagged photons at Laboratory of Nuclear Science, Tohoku University. We employed the Neutral Kaon Spectrometer (NKS) to detect two pions in the final state, and deduced the cross section for the π^+π^- photoproduction on the "free" and "bound" proton. We have discriminated between the quasi-free and non-quasi-free process applying the kinematical cut on the missing momentum. We found that the total cross section for the γ"p"→pπ^+π^- reaction was about 60% of that for the "free" proton, and this is consistent with the previously obtained data. The one of the dominant part of the non-quasi-free process was found to be the double Δ production. Its cross section is smaller than the previous investigations
Photoproduction of Neutral Kaons on Liquid Deuterium Target(I. Nuclear Physics)
We have performed the experiment of K^0 photoproduction on the liquid deuterium target with Neutral Kaon Spectrometer (NKS) at LNS-Tohoku. The K^0s were measured via K^0_S→π^+π^- decay channel in the threshold region. The momentum spectra of K^0 photoproduction cross sections were derived and compared with the calculations using representative models
Study of Strangeness Photo-production in the Threshold Region at LNS-Tohoku(I. Nuclear Physics)
Study of Strangeness Photo-production in the Threshold Region at LNS-Tohoku(I. Nuclear Physics)
We have successfully measured neutral kaons, bombarding a liquid deuterium target with a photon beam in the threshold region from 0.8 to 1.1GeV. It was the first data for K^0 photoproduction on the deuteron in this energy region. The momentum spectra of K^0 production were compared with theoretical spectra calculated assuming isobar models for the elementary process and a realistic deuteron wave function for the target The present experiment has demonstrated a usefulness of the neutral kaon measurement for the investigation of photo strangeness production reactions