43,937 research outputs found
Long-Range Coulomb Effect on the Antiferromagnetism in Electron-doped Cuprates
Using mean-field theory, we illustrate the long-range Coulomb effect on the
antiferromagnetism in the electron-doped cuprates. Because of the Coulomb
exchange effect, the magnitude of the effective next nearest neighbor hopping
parameter increases appreciably with increasing the electron doping
concentration, raising the frustration to the antiferromagnetic ordering. The
Fermi surface evolution in the electron-doped cuprate NdCeCuO
and the doping dependence of the onset temperature of the antiferromagnetic
pseudogap can be reasonably explained by the present consideration.Comment: 4 pages, 4 figure
Localized gap soliton trains of Bose-Einstein condensates in an optical lattice
We develop a systematic analytical approach to study the linear and nonlinear
solitary excitations of quasi-one-dimensional Bose-Einstein condensates trapped
in an optical lattice. For the linear case, the Bloch wave in the energy
band is a linear superposition of Mathieu's functions and ;
and the Bloch wave in the band gap is a linear superposition of
and . For the nonlinear case, only solitons inside the band gaps are
likely to be generated and there are two types of solitons -- fundamental
solitons (which is a localized and stable state) and sub-fundamental solitons
(which is a lacalized but unstable state). In addition, we find that the
pinning position and the amplitude of the fundamental soliton in the lattice
can be controlled by adjusting both the lattice depth and spacing. Our
numerical results on fundamental solitons are in quantitative agreement with
those of the experimental observation [Phys. Rev. Lett. {\bf92}, 230401
(2004)]. Furthermore, we predict that a localized gap soliton train consisting
of several fundamental solitons can be realized by increasing the length of the
condensate in currently experimental conditions.Comment: 9 pages, 6 figures, accepted for publicaiton in PR
A parity-breaking electronic nematic phase transition in the spin-orbit coupled metal CdReO
Strong electron interactions can drive metallic systems toward a variety of
well-known symmetry-broken phases, but the instabilities of correlated metals
with strong spin-orbit coupling have only recently begun to be explored. We
uncovered a multipolar nematic phase of matter in the metallic pyrochlore
CdReO using spatially resolved second-harmonic optical anisotropy
measurements. Like previously discovered electronic nematic phases, this
multipolar phase spontaneously breaks rotational symmetry while preserving
translational invariance. However, it has the distinguishing property of being
odd under spatial inversion, which is allowed only in the presence of
spin-orbit coupling. By examining the critical behavior of the multipolar
nematic order parameter, we show that it drives the thermal phase transition
near 200 kelvin in CdReO and induces a parity-breaking lattice
distortion as a secondary order.Comment: 9 pages main text, 4 figures, 10 pages supplementary informatio
Density matrix renormalization group study of conjugated polymers with transverse pi-conjugation
We report accurate numerical studies of excited state orderings in long
hypothetical pi-conjugated oligomers in which the hydrogen atoms of
trans-polyacetylene are replaced with conjugated sidegroups, within modified
Hubbard models. There exists a range of the bare Coulomb repulsion for which
the excited state ordering is conducive to photoluminescence in the substituted
systems, even as this ordering is opposite in the unsubstituted polyenes of the
same lengths. Our work provides motivation to study real pi-conjugated polymers
with transverse conjugation and small optical gaps.Comment: 5 pages, 4 fig
Particle Swarm Optimization and gravitational wave data analysis: Performance on a binary inspiral testbed
The detection and estimation of gravitational wave (GW) signals belonging to
a parameterized family of waveforms requires, in general, the numerical
maximization of a data-dependent function of the signal parameters. Due to
noise in the data, the function to be maximized is often highly multi-modal
with numerous local maxima. Searching for the global maximum then becomes
computationally expensive, which in turn can limit the scientific scope of the
search. Stochastic optimization is one possible approach to reducing
computational costs in such applications. We report results from a first
investigation of the Particle Swarm Optimization (PSO) method in this context.
The method is applied to a testbed motivated by the problem of detection and
estimation of a binary inspiral signal. Our results show that PSO works well in
the presence of high multi-modality, making it a viable candidate method for
further applications in GW data analysis.Comment: 13 pages, 5 figure
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