649 research outputs found
Electronic phase diagram of LaBaSrCuO
We performed systematic measurements of magnetic susceptibility on single
crystals of LaBaSrCuO. The dependence of the
superconducting transition temperature on Sr-concentration demonstrates a
step-like pattern upon doping at {\it x}0.08 as the crystal structure
changes from low-temperature tetragonal (LTT) to low-temperature orthorhombic
(LTO) phase at low temperature. Upon cooling, an anomalous upturn in the
susceptibility was observed at the structural phase transition between the
LTT-LTO phases under the magnetic field parallel to {\it c}-axis.Comment: 6 pages, 4 figures, Proceeding paper of the Stripes2000 conference in
Roma, Ital
Electronic inhomogeneity and competing phases in electron-doped superconducting Pr0.88LaCe0.12CuO4
We use neutron scattering to demonstrate that electron-doped superconducting
Pr0.88LaCe0.12CuO4 in the underdoped regime is electronically phase separated
in the ground state, showing the coexistence of a superconducting phase with a
three-dimensional antiferromagnetically ordered phase and a
quasi-two-dimensional spin density wave modulation. The Neel temperature of
both antiferromagnetic phases decreases linearly with increasing
superconducting transition temperature (Tc) and vanishes when optimal
superconductivity is achieved. These results indicate that the electron-doped
copper oxides are close to a quantum critical point, where the delicate
energetic balance between different competing states leads to microscopic
heterogeneity.Comment: 14 pages, 4 figures, accepted to Phys. Rev. B as a rapid
communicatio
Syntheses, structures, and mesomorphism of a series of Cu(II) salen complexes with 4-substituted long alkoxy chains
This is a preprint of an article whose final and definitive form has been published in the MOLECULAR CRYSTALS AND LIQUID CRYSTALS © 2007 copyright Taylor & Francis; MOLECULAR CRYSTALS AND LIQUID CRYSTALS is available online at : http://www.informaworld.com/openurl?genre=article&issn=1542-1406&volume=466&issue=1&spage=129ArticleMOLECULAR CRYSTALS AND LIQUID CRYSTALS. 466(1): 129-147 (2007)journal articl
NMR relaxation time around a vortex in stripe superconductors
Site-dependent NMR relaxation time is calculated in the vortex
state using the Bogoliubov-de Gennes theory, taking account of possible
"field-induced stripe'' states in which the magnetism arises locally around a
vortex core in d-wave superconductivity. The recently observed huge enhancement
below at a core site in TlBaCuO is
explained. The field-induced stripe picture explains consistently other
relevant STM and neutron experiments.Comment: 4 pages, 4 figure
Neutron Scattering Study of Temperature-Concentration Phase Diagram of (Cu1-xMgx)GeO3
In doped CuGeO3 systems, such as (Cu1-xZnx)GeO3 and Cu(Ge1-xSix)O3, the
spin-Peierls (SP) ordering (T<Tsp) coexists with the antiferromagnetic (AF)
phase (T<TN<Tsp). Tsp decreases while TN increases with increasing x in low
doping region. For higher x, however, the SP state disappears and only the AF
state remains. These features are common for all the doped CuGeO3 systems so
far studied, indicating the existence of universal T-x phase diagram. Recently,
Masuda et al. carried out comprehensive magnetic susceptibility (chi)
measurements of (Cu1-xMgx)GeO3, in which doping concentration can be controlled
significantly better than the Zn doped systems. They found that TN suddenly
jumps from 3.43 to 3.98K at the critical concentration xc sim 0.023 and that a
drop in chi corresponding to the SP ordering also disappears at x>xc. They thus
concluded that there is a compositional phase boundary between two distinct
magnetic phases. To clarify the nature of two phases, we performed
neutron-scattering measurements on (Cu1-xMgx)GeO3 single crystals with various
x. Analysis of the data at fixed temperature points as a function of doping
concentration has revealed sudden changes of order parameters at the critical
concentration xc=0.027 +- 0.001. At finite temperatures below TN, the drastic
increase of the AF moment takes place at xc. The spin-Peierls order parameter
delta associated with lattice dimerization shows a precipitous decrease at all
temperature below Tsp. However, it goes to zero above xc only at the low
temperature limit.Comment: 9 pages, 9 figure
Gigantic anisotropic uniaxial pressure effect on superconductivity within the CuO2 plane of La1.64Eu0.2Sr0.16CuO4 - strain control of stripe criticality
The effect of uniaxial pressure on superconductivity was examined for a
high-Tc cuprate La1.64Eu0.2Sr0.16CuO4, which is located at the boundary between
the superconducting and stripe phases. We found remarkably large anisotropy of
the uniaxial pressure effect not only between the in-plane and out-of-plane
pressures but also within the CuO2-plane. When the pressure is applied along
the tetragonal [110] direction, we found the largest pressure effect ever
observed in cuprates, dTc/dP - 2.5 K/kbar, while the change of Tc was not
appreciable when applied along [100]. This substantial in-plane anisotropy is
attributed to an intimate link between the symmetry of the one-dimensional
stripes and that of the strain produced within the CuO2 plane.Comment: 4 pages including 3 figure
AKARI-CAS --- Online Service for AKARI All-Sky Catalogues
The AKARI All-Sky Catalogues are an important infrared astronomical database
for next-generation astronomy that take over the IRAS catalog. We have
developed an online service, AKARI Catalogue Archive Server (AKARI-CAS), for
astronomers. The service includes useful and attractive search tools and visual
tools.
One of the new features of AKARI-CAS is cached SIMBAD/NED entries, which can
match AKARI catalogs with other catalogs stored in SIMBAD or NED. To allow
advanced queries to the databases, direct input of SQL is also supported. In
those queries, fast dynamic cross-identification between registered catalogs is
a remarkable feature. In addition, multiwavelength quick-look images are
displayed in the visualization tools, which will increase the value of the
service.
In the construction of our service, we considered a wide variety of
astronomers' requirements. As a result of our discussion, we concluded that
supporting users' SQL submissions is the best solution for the requirements.
Therefore, we implemented an RDBMS layer so that it covered important
facilities including the whole processing of tables. We found that PostgreSQL
is the best open-source RDBMS products for such purpose, and we wrote codes for
both simple and advanced searches into the SQL stored functions. To implement
such stored functions for fast radial search and cross-identification with
minimum cost, we applied a simple technique that is not based on dividing
celestial sphere such as HTM or HEALPix. In contrast, the Web application layer
became compact, and was written in simple procedural PHP codes. In total, our
system realizes cost-effective maintenance and enhancements.Comment: Yamauchi, C. et al. 2011, PASP..123..852
Absence of magnetic field effect on static magnetic order in electron-doped superconductor Nd_{1.86}Ce_{0.14}CuO_4
Neutron-scattering experiments were performed to study the magnetic field
effect on the electron-doped cuprate superconductor Nd_{1.86}Ce_{0.14}CuO_4,
which shows the coexistence of magnetic order and superconductivity. The (1/2
3/2 0) magnetic Bragg intensity, which mainly originates from the order of both
the Cu and Nd moments at low temperatures, shows no magnetic field dependence
when the field is applied perpendicular to the CuO_{2} plane up to 10 T above
the upper critical field. This result is significantly different from that
reported for the hole-doped cuprate superconductors, in which the quasi-static
magnetic order is noticeably enhanced under a magnetic field.Comment: 4 pages, 3 figure
Translational Symmetry Breaking in the Superconducting State of the Cuprates: Analysis of the Quasiparticle Density of States
Motivated by the recent STM experiments of J.E. Hoffman et.al. and C. Howald
et.al., we study the effects of weak translational symmetry breaking on the
quasiparticle spectrum of a d-wave superconductor. We develop a general
formalism to discuss periodic charge order, as well as quasiparticle scattering
off localized defects. We argue that the STM experiments in
cannot be explained using a simple charge density
wave order parameter, but are consistent with the presence of a periodic
modulation in the electron hopping or pairing amplitude. We review the effects
of randomness and pinning of the charge order and compare it to the impurity
scattering of quasiparticles. We also discuss implications of weak
translational symmetry breaking for ARPES experiments.Comment: 12 pages, 9 figs; (v2) minor corrections to formalism, discussions of
dispersion, structure factors and sum rules added; (v3) discussion of
space-dependent normalization added. To be published in PR
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