2,524 research outputs found
Cluster-orbital shell model approach and developments for study of neutron-rich systems
We develop an m-scheme approach of the cluster-orbital shell model (COSM). By using the Gaussian as the radial part of the basis function, components of the unbound states are correctly taken into account. We apply the m-scheme COSM to oxygen isotopes and study the energies and r.m.s.radii
Superconducting gap of overdoped Tl2Ba2CuO6+d observed by Raman scattering
We report Raman scattering spectra for single crystals of overdoped
Tl2Ba2CuO6+d (Tl-2201) at low temperatures. It was observed that the
pair-breaking peaks in A1g and B1g spectra radically shift to lower energy with
carrier doping. We interpret it as s-wave component mixing into d-wave,
although the crystal structure is tetragonal. Since similar phenomena were
observed also in YBa2Cu3Oy and Bi2Sr2CaCu2Oz, we conclude that s-wave mixing is
a common property for overdoped high-Tc superconductors.Comment: 8 pages, 3 figures, proceedings of SNS200
Mott gap excitations in twin-free YBa2Cu3O7-d (Tc = 93 K) studied by RIXS
Mott gap excitations in the high-Tc superconductor of the optimal doped
YBa2Cu3O7-d (Tc = 93 K) have been studied by the resonant inelastic x-ray
scattering method. Anisotropic spectra in the ab-plane are observed in a
twin-free crystal. The excitation from the one-dimensional CuO chain is
enhanced at 2 eV near the zone boundary of the b* direction, while the
excitation from the CuO2 plane is broad at 1.5-4 eV and almost independent of
the momentum transfer. Theoretical calculation based on the one-dimensional and
two-dimensional Hubbard model reproduces the observed spectra by taking the
different parameters of the on-site Coulomb energy. The fact of the Mott gap of
the CuO chain site is much smaller than that of CuO2 plane site is observed for
the first time
Buried double CuO chains in YBaCuO uncovered by nano-ARPES
The electron dynamics in the CuO chains has been elusive in Y-Ba-Cu-O cuprate
systems by means of standard angle-resolved photoemission spectroscopy (ARPES);
cleaved sample exhibits areas terminated by both CuO-chain or BaO layers, and
the size of a typical beam results in ARPES signals that are superposed from
both terminations. Here, we employ spatially-resolved ARPES with submicrometric
beam (nano-ARPES) to reveal the surface-termination-dependent electronic
structures of the double CuO chains in YBaCuO. We present the first
observation of sharp metallic dispersions and Fermi surfaces of the double CuO
chains buried underneath the CuO-plane block on the BaO terminated surface.
While the observed Fermi surfaces of the CuO chains are highly one-dimensional,
the electrons in the CuO-chains do not undergo significant electron
correlations and no signature of a Tomonaga-Luttinger liquid nor a marginal
Fermi liquid is found. Our works represent an important experimental step
toward understanding of the charge dynamics and provides a starting basis for
modelling the high- superconductivity in YBCO cuprate systems.Comment: 10 pages, 5 figures including supplementary material (4 pages, 2
figures
Simplified method to include the tensor contribution in cluster model
We propose a simplified model to directly take into account the contribution of the tensor interaction SMT for light nuclei by extending the cluster model. In 8Be, the energy curve with respect to the relative distance between the two 4He clusters suggests that the cluster structure persists even though the tensor interaction contributes strongly. In addition to SMT, a simplified method to take into account the strong spin orbit contributions is introduced and the coupling effects of these two models is shown to be important in 12C, in contrast to 8B
Universal observation of multiple order parameters in cuprate superconductors
The temperature dependence of the London penetration depth \lambda was
measured for an untwined single crystal of YBa_2Cu_3O_{7-\delta} along the
three principal crystallographic directions (a, b, and c). Both in-plane
components (\lambda_a and \lambda_b) show an inflection point in their
temperature dependence which is absent in the component along the c-direction
(\lambda_c). The data provide convincing evidence that the in-plane
superconducting order parameter is a mixture of s+d-wave symmetry whereas it is
exclusively s-wave along the c-direction. In conjunction with previous results
it is concluded that coupled s+d-order parameters are universal and intrinsic
to cuprate superconductors.Comment: 5 pages, 3 figure
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