256 research outputs found
Linear dependence of peak width in \chi(\bq, \omega) vs T_c for YBCO superconductors
It is shown that the momentum space width of the peak in the spin
susceptibility, Im, is linearly proportional to the
superconducting : with \AA. This relation is similar to the linear relation between incommensurate
peak splitting and in LaSrCuO superconductors, as first proposed by
Yamada et al. (Phys. Rev. B 57, 6165, (1998)). The velocity is
smaller than Fermi velocity or the spin-wave velocity of the parent compound
and remains the same for a wide doping range. This result points towards strong
similarities in magnetic state of YBCO and LaSrCuO.Comment: 5 pages, 3 figures, latex fil
Testing of a novel web browser interface for the Chinese market
This paper compares the perspicacity, appropriateness and preference of web browser icons from leading software providers with those of a culture-specific design. This online study was conducted in Taiwan and involved 103 participants, who were given three sets of web browser icons to review, namely Microsoft Internet Explorer, Macintosh Safari, and culturally specific icons created using the Culture-Centred Design methodology. The findings of the study show that all three sets have generally high recognition rates, but that some icon functions (e.g. Go/Visit and Favourite) in all three sets have poor recognition rates and are considered inappropriate
Neutron scattering study of ferroelectric Sn2P2S6 under pressure
Ferroelectric phase transition in the semiconductor Sn2P2S6 single crystal
has been studied by means of neutron scattering in the pressure-temperature
range adjacent to the anticipated tricritical Lifshitz point (p=0.18GPa,
T=296K). The observations reveal a direct ferroelectric-paraelectric phase
transition in the whole investigated pressure range (0.18 - 0.6GPa). These
results are in a clear disagreement with phase diagrams assumed in numerous
earlier works, according to which a hypothetical intermediate incommensurate
phase extends over several or even tens of degrees in the 0.5GPa pressure
range. Temperature dependence of the anisotropic quasielastic diffuse
scattering suggests that polarization fluctuations present above TC are
strongly reduced in the ordered phase. Still, the temperature dependence of the
(200) Bragg reflection intensity at p=0.18GPa can be remarkably well modeled
assuming the order-parameter amplitude growth according to the power law with
logarithmic corrections predicted for a uniaxial ferroelectric transition at
the tricritical Lifshitz point
Bulk and surface low-energy excitations in YBa2Cu3O7-d studied by high-resolution angle-resolved photoemission spectroscopy
We have performed high-resolution angle-resolved photoemission spectroscopy
on YBa2Cu3O7-delta (Y123; delta = 0.06; Tc = 92 K). By accurately determining
the Fermi surface and energy band dispersion, we solve long-standing
controversial issues as to the anomalous electronic states of Y-based high-Tc
cuprates. We unambiguously identified surface-bilayer-derived bonding and
antibonding bands, together with their bulk counterparts. The surface bands are
highly overdoped (hole concentration x = 0.29), showing no evidence for the gap
opening or the dispersion anomaly in the antinodal region, while the bulk bands
show a clear dx2-y2-wave superconducting gap and the Bogoliubov
quasiparticle-like behavior with a characteristic energy scale of 50-60 meV
indicative of a strong electron-boson coupling in the superconducting state.
All these results suggest that the metallic and superconducting states coexist
at the adjacent bilayer of Y123 surface.Comment: Accepted for publication in Phys. Rev.
2D orbital-like magnetic order in
In high temperature copper oxides superconductors, a novel magnetic order
associated with the pseudogap phase has been identified in two different
cuprate families over a wide region of temperature and doping. We here report
the observation below 120 K of a similar magnetic ordering in the archetypal
cuprate (LSCO) system for x=0.085. In contrast to the
previous reports, the magnetic ordering in LSCO is {\it\bf only} short range
with an in-plane correlation length of 10 \AA\ and is bidimensional
(2D). Such a less pronounced order suggests an interaction with other
electronic instabilities. In particular, LSCO also exhibits a strong tendency
towards stripes ordering at the expense of the superconducting state.Comment: 4 figures, submitted to Phys. Rev. Let
Quantum Statistics of Interacting Dimer Spin Systems
The compound TlCuCl3 represents a model system of dimerized quantum spins
with strong interdimer interactions. We investigate the triplet dispersion as a
function of temperature by inelastic neutron scattering experiments on single
crystals. By comparison with a number of theoretical approaches we demonstrate
that the description of Troyer, Tsunetsugu, and Wuertz [Phys. Rev. B 50, 13515
(1994)] provides an appropriate quantum statistical model for dimer spin
systems at finite temperatures, where many-body correlations become
particularly important.Comment: 4 pages, 4 figures, to appear in Physical Review Letter
Charge Segregation and Antiferromagnetism in High-Tc Superconductors
Local antiferromagnetism coexists with superconductivity in the cuprates.
Charge segregation provides a way to reconcile these properties. Direct
evidence for modulated spin and charge densities has been found in neutron and
X-ray scattering studies of Nd-doped La(2-x)Sr(x)CuO(4). Here we discuss the
nature of the modulation, and present some new results for a Zn-doped sample.
Some of the open questions concerning the connections between segregation and
superconductivity are described.Comment: 9 pp using elsart.sty, 3 eps figures included with psfig.sty, for
Proc. of ISSP-7, to be published in J. Phys. Chem. Solid
Stripe order, depinning, and fluctuations in LaBaCuO and LaBaSrCuO
We present a neutron scattering study of stripe correlations measured on a
single crystal of LaBaCuO. Within the
low-temperature-tetragonal (LTT) phase, superlattice peaks indicative of spin
and charge stripe order are observed below 50 K. For excitation energies
meV, we have characterized the magnetic excitations that
emerge from the incommensurate magnetic superlattice peaks. In the ordered
state, these excitations are similar to spin waves. Following these excitations
as a function of temperature, we find that there is relatively little change in
the {\bf Q}-integrated dynamical spin susceptibility for
meV as stripe order disappears and then as the structure transforms from LTT to
the low-temperature-orthorhombic (LTO) phase. The {\bf Q}-integrated signal at
lower energies changes more dramatically through these transitions, as it must
in a transformation from an ordered to a disordered state. We argue that the
continuous evolution through the transitions provides direct evidence that the
incommensurate spin excitations in the disordered state are an indicator of
dynamical charge stripes. An interesting feature of the thermal evolution is a
variation in the incommensurability of the magnetic scattering. Similar
behavior is observed in measurements on a single crystal of
LaBaSrCuO; maps of the scattered intensity
in a region centered on the antiferromagnetic wave vector and measured at
meV are well reproduced by a model of disordered stripes with a
temperature-dependent mixture of stripe spacings. We discuss the relevance of
our results to understanding the magnetic excitations in cuprate
superconductors.Comment: 12 pages, 11 figures, 1 tabl
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