65,679 research outputs found
Universal behavior of giant electroresistance in epitaxial La0.67Ca0.33MnO3 thin films
We report a giant resistance drop induced by dc electrical currents in
La0.67Ca0.33MnO3 epitaxial thin films. Resistance of the patterned thin films
decreases exponentially with increasing current and a maximum drop shows at the
temperature of resistance peak Tp. Variation of resistance with current
densities can be scaled below and above Tp, respectively. This work can be
useful for the future applications of electroresistance.Comment: 13 pages, 4 figure
Level-one Highest Weight Representation of and Bosonization of the Multi-component Super t-J Model
We study the level-one irreducible highest weight representations of the
quantum affine superalgebra , and calculate their
characters and supercharacters. We obtain bosonized q-vertex operators acting
on the irreducible -modules and derive the exchange
relations satisfied by the vertex operators. We give the bosonization of the
multi-component super model by using the bosonized vertex operators.Comment: LaTex file 21 page
Vertex Operators, Screen Currents and Correlation Functions at Arbitrary Level
Bosonized q-vertex operators related to the 4-dimensional evaluation modules
of the quantum affine superalgebra are constructed for
arbitrary level , where is a complex parameter
appearing in the 4-dimensional evaluation representations. They are
intertwiners among the level- highest weight Fock-Wakimoto modules.
Screen currents which commute with the action of up to
total differences are presented. Integral formulae for N-point functions of
type I and type II q-vertex operators are proposed.Comment: Latex file 18 page
Structural, magnetic and transport properties in the Cu-doped manganites La0.85Te0.15Mn1-xCuxO3 (0 \leq x \leq 0.20)
The effect of Cu-doping at Mn-site on structural, magnetic and transport
properties in electron-doped manganites La0.85Te0.15Mn1-xCuxO3 has been
investigated. Based on the analysis of structural parameter variations, the
valence state of the Cu ion in Cu-doped manganites is suggested to be +2. All
samples undergo the paramagnetic-ferromagnetic (PM-FM) phase transition. The
Curie temperature decreases and the transition becomes broader with increasing
Cu-doping level, in contrast, the magnetization magnitude of Cu-doping samples
at low temperatures increase as x \leq 0.15. The insulator-metal (I-M)
transition moves to lower temperatures with increasing Cu-doping content and
disappears as x > 0.1. In addition, the higher temperature resistivity r peak
in double-peak-like r(T) curves observed in no Cu-doping sample is completely
suppressed as Cu-doping level x = 0.1 and r(T) curve only shows single I-M
transition at the low temperature well below . The results are discussed
according to the change of magnetic exchange interaction caused by Cu-doping.Comment: 17 pages, 5 figures. Phys.Rev.B (to be published
A magnetar-powered X-ray transient as the aftermath of a binary neutron-star merger
Neutron star-neutron star mergers are known to be associated with short
gamma-ray bursts. If the neutron star equation of state is sufficiently stiff,
at least some of such mergers will leave behind a supramassive or even a stable
neutron star that spins rapidly with a strong magnetic field (i.e., a
magnetar). Such a magnetar signature may have been observed as the X-ray
plateau following a good fraction (up to 50%) of short gamma-ray bursts, and it
has been expected that one may observe short gamma-ray burst-less X-ray
transients powered by double neutron star mergers. A fast X-ray transient
(CDF-S XT1) was recently found to be associated with a faint host galaxy whose
redshift is unknown. Its X-ray and host-galaxy properties allow several
possibleexplanations including a short gamma-ray burst seen off axis, a
low-luminosity gamma-ray burst at high redshift, or a tidal disruption event
involving an intermediate mass black hole and a white dwarf. Here we report a
second X-ray transient, CDF-S XT2, that is associated with a galaxy at redshift
z = 0.738. The light curve is fully consistent with being powered by a
millisecond magnetar. More intriguingly, CDF-S XT2 lies in the outskirts of its
star-forming host galaxy with a moderate offset from the galaxy center, as
short bursts often do. The estimated event rate density of similar X-ray
transients, when corrected to the local value, is consistent with the double
neutron star merger rate density inferred from the detection of GW170817.Comment: 29 pages, 4 figures, 3 tables, published in Nature on 11 April 201
A fast input/output library for high-resolution climate models
We describe the design and implementation of climate fast input/output
(CFIO), a fast input/output (I/O) library for high-resolution climate models.
CFIO provides a simple method for modelers to overlap the I/O phase with the
computing phase automatically, so as to shorten the running time of numerical
simulations. To minimize the code modifications required for porting, CFIO
provides similar interfaces and features to parallel Network Common Data Form
(PnetCDF), which is one of the most widely used I/O libraries in climate
models. We deployed CFIO in three high-resolution climate models, including
two ocean models (POP and LICOM) and one sea ice model (CICE). The
experimental results show that CFIO improves the performance of climate
models significantly versus the original serial I/O approach. When running
with CFIO at 0.1° resolution with about 1000 CPU cores, we managed
to reduce the running time by factors of 7.9, 4.6 and 2.0 for POP, CICE, and
LICOM, respectively. We also compared the performance of CFIO against two
existing libraries, PnetCDF and parallel I/O (PIO), in different scenarios.
For scenarios with both data output and computations, CFIO decreases the I/O
overhead compared to PnetCDF and PIO
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