14,731 research outputs found
Origin of Middle-Infrared Peaks in Cerium Compounds
We have demonstrated that the middle-infrared (mid-IR) peaks in the optical
conductivity spectra of Ce ( = Pd, Sn, In) can be explained by
first-principle band structure calculation with the spin-orbit interaction. The
mid-IR peak shapes in these materials are not identical to one another:
CePd, CeSn, and CeIn have a triple-peak structure, double-peak
structure and broad single-peak structure, respectively. These peaks can be
theoretically explained by the optical transition from the occupied state to
the spin-orbit splitted Ce state. This result indicates that the mid-IR
peaks originate from the simple band picture with the Ce state near the
Fermi level, not from the conventional cf hybridization gap based on the
periodic Anderson model.Comment: 5 pages, 6 figures. To be published in J. Phys. Soc. Jpn. 78(1)
(2009
Structural effect on the static spin and charge correlations in LaBaSrCuO
We report the results of elastic neutron scattering measurements performed on
1/8-hole doped LaBaSrCuO single crystals with
{\it x}=0.05, 0.06, 0.075 and 0.085. In the low-temperature less-orthorhombic
(LTLO, {\it Pccn} symmetry) phase, the charge-density-wave (CDW) and
spin-density-wave (SDW) wavevectors were found to tilt in a low-symmetric
direction with one-dimensional anisotropy in the CuO plane, while they
were aligned along the high-symmetry axis in the low-temperature tetragonal
(LTT, {\it P}4/{\it ncm} symmetry) phase. The coincident direction of two
wavevectors suggests a close relation between CDW and SDW orders. The SDW
wavevector systematically deviates from the Cu-O bond direction in the LTLO
phase upon Sr substitution and the tilt angle in the LTLO phase is smaller than
that in the low-temperature orthorhombic phase (LTO, {\it B}{\it mab} symmetry)
with comparable in-plane orthorhombic distortion. These results demonstrate a
correlation between the corrugated pattern of CuO plane and the
deviations.Comment: 6 pages, 7figure
Narrow band imaging in [OIII] and Halpha to search for ICPNe in the Virgo cluster
We have identified intracluster planetary nebulae in a Virgo cluster core
field by imaging with the Subaru Suprime-Cam through two narrow band filters
centered at the redshifted wavelengths of the [OIII] \AA and the
H \AA lines; broad-band images in V and R were
acquired to check for emission in the adjacent continuum. Emission line objects
in Virgo are then selected from the two-color diagram ([OIII] -- Halpha) vs.
([OIII] -- (V+R)), which is calibrated using PNe in M84 (Jacoby et al. 1990).
Using both [OIII] and Halpha allows us to distinguish bona-fide planetary
nebulae from high redshift emission-line galaxies at the bright end of the
[OIII] luminosity function. Spectroscopic observations of a subsample of these
objects were made at the TNG and at the VLT, in a region around M84 and in an
intracluster field respectively. The observations confirm the efficiency of the
combined [OIII]+H imaging to identify true PNe. We also obtained the
first spectrum of an intracluster PN which shows the [OIII] doublet with S/N >
10 and its Halpha emission. From the results based on the spectroscopic
follow-up, we derive a lower limit to the fraction of the Virgo cluster light
contributed by the intracluster stars at the surveyed position in the cluster
core: it amounts to 10%.Comment: 32 pages,11 figures, in press on AJ, February 200
Magnetic properties of single-crystalline CeCuGa3
The magnetic behavior of single-crystalline CeCuGa3 has been investigated.
The compound forms in a tetragonal BaAl4-type structure consisting of
rare-earth planes separated by Cu-Ga layers. If the Cu-Ga site disorder is
reduced, CeCuGa3 adopts the related, likewise tetragonal BaNiSn3-type
structure, in which the Ce ion are surrounded by different Cu and Ga layers and
the inversion symmetry is lost. In the literature conflicting reports about the
magnetic order of CeCuGa3 have been published. Single crystals with the
centrosymmetric structure variant exhibit ferromagnetic order below approx. 4 K
with a strong planar anisotropy. The magnetic behavior above the transition
temperature can be well understood by the crystal-field splitting of the 4f
Hund's rule ground-state multiplet of the Ce ions
A Trial to Establish an Archival Finding Aid Utilizing the Encoded Archival Description - 1 -
Cascade of Complexity in Evolving Predator-Prey Dynamics
We simulate an individual-based model that represents both the phenotype and
genome of digital organisms with predator-prey interactions. We show how
open-ended growth of complexity arises from the invariance of genetic evolution
operators with respect to changes in the complexity, and that the dynamics
which emerges is controlled by a non-equilibrium critical point. The mechanism
is analogous to the development of the cascade in fluid turbulence.Comment: 5 pages, 3 figures; added comments on system size scaling and
turbulence analogy, added error estimates of data collapse parameters.
Slightly enhanced from the version which will appear in PR
Incommensurate lattice distortion in the high temperature tetragonal phase of La(Sr,Ba)CuO
We report incommensurate diffuse (ICD) scattering appearing in the
high-temperature-tetragonal (HTT) phase of La(Sr,Ba)CuO
with observed by the neutron diffraction technique. For
all compositions, a sharp superlattice peak of the low-temperature-orthorhombic
(LTO) structure is replaced by a pair of ICD peaks with the modulation vector
parallel to the CuO octahedral tilting direction, that is, the diagonal
Cu-Cu direction of the CuO plane, above the LTO-HTT transition temperature
. The temperature dependences of the incommensurability for all
samples scale approximately as , while those of the integrated intensity
of the ICD peaks scale as . These observations together with
absence of ICD peaks in the non-superconducting sample evince a
universal incommensurate lattice instability of hole-doped 214 cuprates in the
superconducting regime.Comment: 6 pages, 6 figure
Slater to Mott crossover in the metal to insulator transition of Nd2Ir2O7
We present an angle-resolved photoemission study of the electronic structure
of the three-dimensional pyrochlore iridate Nd2Ir2O7 through its magnetic
metal-insulator transition. Our data reveal that metallic Nd2Ir2O7 has a
quadratic band, touching the Fermi level at the Gamma point, similarly to that
of Pr2Ir2O7. The Fermi node state is, therefore, a common feature of the
metallic phase of the pyrochlore iridates. Upon cooling below the transition
temperature, this compound exhibits a gap opening with an energy shift of
quasiparticle peaks like a band gap insulator. The quasiparticle peaks are
strongly suppressed, however, with further decrease of temperature, and
eventually vanish at the lowest temperature, leaving a non-dispersive flat band
lacking long-lived electrons. We thereby identify a remarkable crossover from
Slater to Mott insulators with decreasing temperature. These observations
explain the puzzling absence of Weyl points in this material, despite its
proximity to the zero temperature metal-insulator transition
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