268 research outputs found
The effect of thiophene sequence separation on air-stable organic thin-film transistor materials
ArticleORGANIC ELECTRONICS. 9(4): 425-431(2008)journal articl
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
The Discovery of a Very Narrow-Line Star Forming Obat a Redshift of 5.66ject
We report on the discovery of a very narrow-line star forming object beyond
redshift of 5. Using the prime-focus camera, Suprime-Cam, on the 8.2 m Subaru
telescope together with a narrow-passband filter centered at
= 8150 \AA with passband of = 120 \AA, we have obtained a very
deep image of the field surrounding the quasar SDSSp J104433.04012502.2 at a
redshift of 5.74. Comparing this image with optical broad-band images, we have
found an object with a very strong emission line. Our follow-up optical
spectroscopy has revealed that this source is at a redshift of
, forming stars at a rate
yr. Remarkably, the velocity dispersion of Ly-emitting gas is
only 22 km s. Since a blue half of the Ly emission could be
absorbed by neutral hydrogen gas, perhaps in the system, a modest estimate of
the velocity dispersion may be 44 km s. Together with a linear
size of 7.7 kpc, we estimate a lower limit of the dynamical mass
of this object to be . It is thus suggested that
LAE J10440123 is a star-forming dwarf galaxy (i.e., a subgalactic object or
a building block) beyond redshift 5 although we cannot exclude a possibility
that most Ly emission is absorbed by the red damping wing of neutral
intergalactic matter.Comment: 6 pages, 2 figures. ApJ Letters, in pres
Observation of Spin-Dependent Charge Symmetry Breaking in Interaction: Gamma-Ray Spectroscopy of He
The energy spacing between the ground-state spin doublet of He(1,0) was determined to be keV, by measuring
rays for the transition with a high efficiency germanium
detector array in coincidence with the He He
reaction at J-PARC. In comparison to the corresponding energy spacing in the
mirror hypernucleus H, the present result clearly indicates the
existence of charge symmetry breaking (CSB) in interaction. It is
also found that the CSB effect is large in the ground state but is by one
order of magnitude smaller in the excited state, demonstrating that the
CSB interaction has spin dependence
Bond-Stretching-Phonon Anomalies in Stripe-Ordered La(1.69)Sr(0.31)NiO(4)
We report a neutron scattering study of bond-stretching phonons in
La(1.69)Sr(0.31)NiO(4), a doped antiferromagnet in which the added holes order
in diagonal stripes at 45 deg to the Ni-O bonds. For the highest-energy
longitudinal optical mode along the bonds, a softening of 20% is observed
between the Brillouin zone center and zone boundary. At 45 deg to the bonds, a
splitting of the same magnitude is found across much of the zone. Surprisingly,
the charge-ordering wave vector plays no apparent role in the anomalous
dispersions. The implications for related anomalies in the cuprates are
discussed.Comment: 4 two-col pages, including 4 figures (2 in color); references added
and updated Final version, accepted for publication in PR
Nernst Effect of stripe ordering LaEuSrCuO
We investigate the transport properties of
LaEuSrCuO (, 0.08, 0.125, 0.15, 0.2) with a
special focus on the Nernst effect in the normal state. Various anomalous
features are present in the data. For and 0.15 a kink-like anomaly is
present in the vicinity of the onset of charge stripe order in the LTT phase,
suggestive of enhanced positive quasiparticle Nernst response in the stripe
ordered phase. At higher temperature, all doping levels except exhibit
a further kink anomaly in the LTO phase which cannot unambiguously be related
to stripe order. Moreover, a direct comparison between the Nernst coefficients
of stripe ordering LaEuSrCuO and superconducting
LaSrCuO at the doping levels and reveals
only weak differences. Our findings make high demands on any scenario
interpreting the Nernst response in hole-doped cuprates
Magnetic neutron scattering in hole doped cuprate superconductors
A review is presented of the static and dynamic magnetic properties of
hole-doped cuprate superconductors measured with neutron scattering. A wide
variety of experiments are described with emphasis on the monolayer
La_{2-x}(Sr,Ba)_{x}CuO_{4} and bilayer YBa_{2}Cu_{3}O_{6+x} cuprates. At zero
hole doping, both classes of materials are antiferromagnetic insulators with
large superexchange constants of J > 100 meV. For increasing hole doping, the
cuprates become superconducting at a critical hole concentration of
x_{c}=0.055. The development of new instrumentation at neutron beam sources
coupled with the improvement in materials has lead to a better understanding of
these materials and the underlying spin dynamics over a broad range of hole
dopings. We will describe how the spin dispersion changes across the insulating
to superconducting boundary as well as the static magnetic properties which are
directly coupled with the superconductivity. Experiments directly probing the
competing magnetic and superconducting order parameters involving magnetic
fields, impurity doping, and structural order will be examined. Correlations
between superconductivity and magnetism will also be discussed.Comment: 14 pages, 18 figures. To be published in Journal of the Physical
Society of Japa
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