3,764 research outputs found
Orbital Degeneracy and Peierls Instability in Triangular Lattice Superconductor IrPtTe
We have studied electronic structure of triangular lattice
IrPtTe superconductor using photoemission spectroscopy and
model calculations. Ir core-level photoemission spectra show that Ir
charge modulation established in the low temperature phase of IrTe
is suppressed by Pt doping. This observation indicates that the suppression of
charge modulation is related to the emergence of superconductivity.
Valence-band photoemission spectra of IrTe suggest that the Ir charge
modulation is accompanied by Ir orbital reconstruction. Based on the
photoemission results and model calculations, we argue that the
orbitally-induced Peierls effect governs the charge and orbital instability in
the IrPtTe.Comment: 5 pages,4 figure
Electronic structure reconstruction by orbital symmetry breaking in IrTe2
We report an angle-resolved photoemission spectroscopy (ARPES) study on IrTe2
which exhibits an interesting lattice distortion below 270 K and becomes
triangular lattice superconductors by suppressing the distortion via chemical
substitution or intercalation. ARPES results at 300 K show multi-band Fermi
surfaces with six-fold symmetry which are basically consistent with band
structure calculations. At 20 K in the distorted phase, whereas the flower
shape of the outermost Fermi surface does not change from that at 300 K,
topology of the inner Fermi surfaces is strongly modified by the lattice
distortion. The Fermi surface reconstruction by the distortion depends on the
orbital character of the Fermi surfaces, suggesting importance of Ir 5d and/or
Te 5p orbital symmetry breaking.Comment: 4pages, 4figure
Important Roles of Te 5p and Ir 5d Spin-orbit Interactions on the Multi-band Electronic Structure of Triangular Lattice Superconductor Ir1-xPtxTe2
We report an angle-resolved photoemission spectroscopy (ARPES) study on a
triangular lattice superconductor IrPtTe in which the Ir-Ir
or Te-Te bond formation, the band Jahn-Teller effect, and the spin-orbit
interaction are cooperating and competing with one another. The Fermi surfaces
of the substituted system are qualitatively similar to the band structure
calculations for the undistorted IrTe with an upward chemical potential
shift due to electron doping. A combination of the ARPES and the band structure
calculations indicates that the Te spin-orbit interaction removes the
orbital degeneracy and induces type spin-orbit
coupling near the A point. The inner and outer Fermi surfaces are entangled by
the Te and Ir spin-orbit interactions which may provide exotic
superconductivity with singlet-triplet mixing.Comment: 10 pages, 4 figure
Radio and millimeter properties of Ly emitters in the COSMOS field: limits on radio AGN, submm galaxies, and dust obscuration
We present observations at 1.4 and 250 GHz of the Ly
emitters (LAE) in the COSMOS field found by Murayama et al.. At 1.4 GHz there
are 99 LAEs in the lower noise regions of the radio field. We do not detect any
individual source down to 3 limits of Jy beam at 1.4
GHz, nor do we detect a source in a stacking analysis, to a 2 limit of
Jy beam. At 250 GHz we do not detect any of the 10 LAEs that are
located within the central regions of the COSMOS field covered by MAMBO () to a typical 2 limit of mJy. The radio data
imply that there are no low luminosity radio AGN with W Hz in the LAE sample. The radio and millimeter observations
also rule out any highly obscured, extreme starbursts in the sample, ie. any
galaxies with massive star formation rates M year in
the full sample (based on the radio data), or 500 M year for the
10% of the LAE sample that fall in the central MAMBO field. The stacking
analysis implies an upper limit to the mean massive star formation rate of
M year.Comment: 11 pages AAStex format 3 figures. ApJ COSMOS Special Issue. Changes:
Added 'Note added in proof' to reflect nine new sources in the LAE sampl
Disorder Effect on the Vortex Pinning by the Cooling Process Control in the Organic Superconductor -(BEDT-TTF)Cu[N(CN)]Br
We investigate the influence of disorders in terminal ethylene groups of
BEDT-TTF molecules (ethylene-disorders) on the vortex pinning of the organic
superconductor -(BEDT-TTF)Cu[N(CN)]Br. Magnetization
measurements are performed under different cooling-processes. The second peak
in the magnetization hysteresis curve is observed for all samples studied, and
the hysteresis width of the magnetization becomes narrower by cooling faster.
In contradiction to the simple pinning effect of disorder, this result shows
the suppression of the vortex pinning force by introducing more
ethylene-disorders. The ethylene-disorder domain model is proposed for
explaining the observed result. In the case of the system containing a moderate
number of the ethylene-disorders, the disordered molecules form a domain
structure and it works as an effective pinning site. On the contrary, an excess
number of the ethylene-disorders may weaken the effect of the domain structure,
which results in the less effective pinning force on the vortices.Comment: 6 pages, 6 figure
A New Superwind Wolf-Rayet Galaxy Mrk 1259
We report the discovery of a starburst-driven wind (superwind) from the
starburst nucleus galaxy Mrk 1259. The estimated number ratio of Wolf-Rayet
(WR) to O stars amounts to ~0.09. While the nuclear emission-line region is due
to usual photoionization by massive stars, the circumnuclear emission-line
regions show anomalous line ratios that can be due to cooling shocks. Since the
host galaxy seems to be a face-on disk galaxy and the excitation conditions of
the circumnuclear emission-line regions show the spatial symmetry, we consider
that we are seeing the superwind nearly from a pole-on view. Cooling shock
models may explain the observed emission line ratios of the circumnuclear
regions although a factor of 2 overabundance of nitrogen is necessary. All
these suggest that the high-mass enhanced starburst occurred ~5X10^6 years ago
in the nuclear region of Mrk 1259.Comment: To be published in the Astrophysical Journal Letters, 15 pages, 4
figure
Gravitational signals emitted by a point mass orbiting a neutron star: effects of stellar structure
The effects that the structure of a neutron star would have on the
gravitational emission of a binary system are studied in a perturbative regime,
and in the frequency domain. Assuming that a neutron star is perturbed by a
point mass moving on a close, circular orbit, we solve the equations of stellar
perturbations in general relativity to evaluate the energy lost by the system
in gravitational waves. We compare the energy output obtained for different
stellar models with that found by assuming that the perturbed object is a black
hole with the same mass, and we discuss the role played by the excitation of
the stellar modes. Ouresults indicate that the stellar structure begins to
affect the emitted power when the orbital velocity is v >0.2c (about 185 Hz for
a binary system composed of two canonical neutron stars). We show that the
differences between different stellar models and a black hole are due mainly to
the excitation of the quasinormal modes of the star. Finally, we discuss to
what extent and up to which distance the perturbative approach can be used to
describe the interaction of a star and a pointlike massive body.Comment: 22 pages, 6 figures, to appear in Phys. Rev. D. Revised version,
added one table and extended discussio
Hierarchical Object Formation in the Peculiar Velocity Field
Using the initial peculiar velocity field, we analytically study the
hierarchical formation of gravitationally bound objects. The field is smoothed
over a scale that corresponds to the mass of a given class of objects. Through
the Zel'dovich approximation, the smoothed field determines how the objects
cluster together to form a new class of more massive objects. The standard
cosmological parameters lead to the evolution of primordial clouds with 10^6
M(sun) -> galaxies with 10^12 M(sun) -> clusters of galaxies with 10^15 M(sun)
-> superclusters of galaxies with 10^16 M(sun). The epochs obtained for the
formation of these classes of objects are consistent with observations.Comment: 16 pages; This version corrects errors in equations and figures of
the published version; The errors are also corrected in the erratum (ApJ,
659, 1792 [2007]
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