5,074 research outputs found
Underlying Pairing States in Cuprate Superconductors
In this Letter, we develop a microscopic theory to describe the close
proximity between the insulating antiferromagnetic (AF) order and the d-wave
superconducting (dSC) order in cuprates. We show that the cuprate ground states
form a configuration of coherent pairing states consisting of extended singlet
Cooper pairs and triplet pairs, which can simultaneously describe AF and
dSC orders.Comment: 4 papes, 1 figur
New mechanism to cross the phantom divide
Recently, type Ia supernovae data appear to support a dark energy whose
equation of state crosses -1, which is a much more amazing problem than the
acceleration of the universe. We show that it is possible for the equation of
state to cross the phantom divide by a scalar field in the gravity with an
additional inverse power-law term of Ricci scalar in the Lagrangian. The
necessary and sufficient condition for a universe in which the dark energy can
cross the phantom divide is obtained. Some analytical solutions with or
are obtained. A minimal coupled scalar with different potentials,
including quadratic, cubic, quantic, exponential and logarithmic potentials are
investigated via numerical methods, respectively. All these potentials lead to
the crossing behavior. We show that it is a robust result which is hardly
dependent on the concrete form of the potential of the scalar.Comment: 11 pages, 5 figs, v3: several references added, to match the
published versio
Effects of electrojet turbulence on a magnetosphere-ionosphere simulation of a geomagnetic storm
Ionospheric conductance plays an important role in regulating the response of the magnetosphereâionosphere system to solar wind driving. Typically, models of magnetosphereâionosphere coupling include changes to ionospheric conductance driven by extreme ultraviolet ionization and electron precipitation. This paper shows that effects driven by the FarleyâBuneman instability can also create significant enhancements in the ionospheric conductance, with substantial impacts on geospace. We have implemented a method of including electrojet turbulence (ET) effects into the ionospheric conductance model utilized within geospace simulations. Our particular implementation is tested with simulations of the LyonâFedderâMobarry global magnetosphere model coupled with the Rice Convection Model of the inner magnetosphere. We examine the impact of including ETâmodified conductances in a case study of the geomagnetic storm of 17 March 2013. Simulations with ET show a 13% reduction in the cross polar cap potential at the beginning of the storm and up to 20% increases in the Pedersen and Hall conductance. These simulation results show better agreement with Defense Meteorological Satellite Program observations, including capturing features of subauroral polarization streams. The fieldâaligned current (FAC) patterns show little differences during the peak of storm and agree well with Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) reconstructions. Typically, the simulated FAC densities are stronger and at slightly higher latitudes than shown by AMPERE. The inner magnetospheric pressures derived from TsyganenkoâSitnov empirical magnetic field model show that the inclusion of the ET effects increases the peak pressure and brings the results into better agreement with the empirical model.This material is based upon work supported by NASA grants NNX14AI13G, NNX13AF92G, and NNX16AB80G. The National Center for Atmospheric Research is sponsored by the National Science Foundation. This work used the XSEDE and TACC computational facilities, supported by National Science Foundation grant ACI-1053575. We would like to acknowledge high-performance computing support from Yellowstone (ark:/85065/d7wd3xhc) provided by NCAR's Computational and Information Systems Laboratory, sponsored by the National Science Foundation. We thank the AMPERE team and the AMPERE Science Center for providing the Iridium derived data products. All model output, simulation codes, and analysis routines are being preserved on the NCAR High-Performance Storage System and will be made available upon written request to the lead author of this publication. (NNX14AI13G - NASA; NNX13AF92G - NASA; NNX16AB80G - NASA; National Science Foundation; ACI-1053575 - National Science Foundation
Superconductivity and non-metallicity induced by doping the topological insulators Bi2Se3 and Bi2Te3
We show that by Ca-doping the Bi2Se3 topological insulator, the Fermi level
can be fine tuned to fall inside the band gap and therefore suppress the bulk
conductivity. Non-metallic Bi2Se3 crystals are obtained. On the other hand, the
Bi2Se3 topological insulator can also be induced to become a bulk
superconductor, with Tc ~ 3.8 K, by copper intercalation in the van der Waals
gaps between the Bi2Se3 layers. Likewise, an as-grown crystal of metallic
Bi2Te3 can be turned into a non-metallic crystal by slight variation of the Te
content. The Bi2Te3 topological insulator shows small amounts of
superconductivity with Tc ~ 5.5 K when reacted with Pd to form materials of the
type PdxBi2Te3
Failure regime in (1+1) dimensions in fibrous materials
In this paper, we introduce a model for fracture in fibrous materials that
takes into account the rupture height of the fibers, in contrast with previous
models. Thus, we obtain the profile of the fracture and calculate its
roughness, defined as the variance around the mean height. We investigate the
relationship between the fracture roughness and the fracture toughness.Comment: 4 pages, 4 figures.eps, Revte
Probing Pulsar Winds Using Inverse Compton Scattering
We investigate the effects of inverse Compton scattering by electrons and
positrons in the unshocked winds of rotationally-powered binary pulsars. This
process can scatter low energy target photons to produce gamma rays with
energies from MeV to TeV. The binary radio pulsars PSR B1259-63 and PSR
J0045-73 are both in close eccentric orbits around bright main sequence stars
which provide a huge density of low energy target photons. The inverse Compton
scattering process transfers momentum from the pulsar wind to the scattered
photons, and therefore provides a drag which tends to decelerate the pulsar
wind. We present detailed calculations of the dynamics of a pulsar wind which
is undergoing inverse Compton scattering, showing that the deceleration of the
wind of PSR B1259-63 due to `inverse Compton drag' is small, but that this
process may confine the wind of PSR J0045-73 before it attains pressure balance
with the outflow of its companion star. We calculate the spectra and light
curves of the resulting inverse Compton emission from PSR B1259-63 and show
that if the size of the pulsar wind nebula is comparable to the binary
separation, then the gamma-ray emission from the unshocked wind may be
detectable by atmospheric Cerenkov detectors or by the new generation of
satellite-borne gamma-ray detectors such as INTEGRAL and GLAST. This mechanism
may therefore provide a direct probe of the freely-expanding regions of pulsar
winds, previously thought to be invisible.Comment: To be published in Astroparticle Physics. 27 pages, 5 figure
Faithful remote state preparation using finite classical bits and a non-maximally entangled state
We present many ensembles of states that can be remotely prepared by using
minimum classical bits from Alice to Bob and their previously shared entangled
state and prove that we have found all the ensembles in two-dimensional case.
Furthermore we show that any pure quantum state can be remotely and faithfully
prepared by using finite classical bits from Alice to Bob and their previously
shared nonmaximally entangled state though no faithful quantum teleportation
protocols can be achieved by using a nonmaximally entangled state.Comment: 6 page
Thermal stability of sputter-deposited 330 austenitic stainless-steel thin films with nanoscale growth twins
We have explored the thermal stability of nanoscale growth twins in sputter-deposited 330 stainless-steel (SS) films by vacuum annealing up to 500 °C. In spite of an average twin spacing of only 4 nm in the as-deposited films, no detectable variation in the twin spacing or orientation of twin interfaces was observed after annealing. An increase in the average columnar grain size was observed after annealing. The hardness of 330 SS films increases after annealing, from 7 GPa for as-deposited films to around 8 GPa for annealed films, while the electrical resistivity decreases slightly after annealing. The changes in mechanical and electrical properties after annealing are interpreted in terms of the corresponding changes in the residual stress and microstructure of the films
Laser-noise-induced correlations and anti-correlations in Electromagnetically Induced Transparency
High degrees of intensity correlation between two independent lasers were
observed after propagation through a rubidium vapor cell in which they generate
Electromagnetically Induced Transparency (EIT). As the optical field
intensities are increased, the correlation changes sign (becoming
anti-correlation). The experiment was performed in a room temperature rubidium
cell, using two diode lasers tuned to the Rb line (nm). The cross-correlation spectral function for the pump and probe fields
is numerically obtained by modeling the temporal dynamics of both field phases
as diffusing processes. We explored the dependence of the atomic response on
the atom-field Rabi frequencies, optical detuning and Doppler width. The
results show that resonant phase-noise to amplitude-noise conversion is at the
origin of the observed signal and the change in sign for the correlation
coefficient can be explained as a consequence of the competition between EIT
and Raman resonance processes.Comment: Accepted for publication in EPJ
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