5,706 research outputs found
Non-linear response to electric field in extended Hubbard models
The electric-field response of a one-dimensional ring of interacting
fermions, where the interactions are described by the extended Hubbard model,
is investigated. By using an accurate real-time propagation scheme based on the
Chebyshev expansion of the evolution operator, we uncover various non-linear
regimes for a range of interaction parameters that allows modeling of metallic
and insulating (either charge density wave or spin density wave insulators)
rings. The metallic regime appears at the phase boundary between the two
insulating phases and provides the opportunity to describe either weakly or
strongly correlated metals. We find that the {\it fidelity susceptibility} of
the ground state as a function of magnetic flux piercing the ring provides a
very good measure of the short-time response. Even completely different
interacting regimes behave in a similar manner at short time-scales as long as
the fidelity susceptibility is the same. Depending on the strength of the
electric field we find various types of responses: persistent currents in the
insulating regime, dissipative regime or damped Bloch-like oscillations with
varying frequencies or even irregular in nature. Furthermore, we also consider
the dimerization of the ring and describe the response of a correlated band
insulator. In this case the distribution of the energy levels is more clustered
and the Bloch-like oscillations become even more irregular
Field effect on surface states in a doped Mott-Insulator thin film
Surface effects of a doped thin film made of a strongly correlated material
are investigated both in the absence and presence of a perpendicular electric
field. We use an inhomogeneous Gutzwiller approximation for a single band
Hubbard model in order to describe correlation effects. For low doping, the
bulk value of the quasiparticle weight is recovered exponentially deep into the
slab, but with increasing doping, additional Friedel oscillations appear near
the surface. We show that the inverse correlation length has a power-law
dependence on the doping level. In the presence of an electrical field,
considerable changes in the quasiparticle weight can be realized throughout the
system. We observe a large difference (as large as five orders of magnitude) in
the quasiparticle weight near the opposite sides of the slab. This effect can
be significant in switching devices that use the surface states for transport
Electrical field induced shift of the Mott Metal-Insulator transition in thin films
The ground state properties of a paramagnetic Mott insulator are investigated
in the presence of an external electrical field using the inhomogeneous
Gutzwiller approximation for a single band Hubbard model in a slab geometry.
The metal insulator transition is shifted towards higher Hubbard repulsions by
applying an electric field perpendicular to the slab. The spatial distribution
of site dependent quasiparticle weight shows that the quasiparticle weight is
maximum in few layers beneath the surface. Moreover only at higher Hubbard
repulsion, larger than the bulk critical U, the electric field will be totally
screened only for centeral cites. Our results show that by presence of an
electric field perpendicular to a thin film made of a strongly correlated
material, states near the surface will remain metallic while the bulk becomes
insulating after some critical U. In contrast, in the absence of the electric
field the surface becomes insulating before the bulk
Spin Fidelity for Three-qubit Greenberger-Horne-Zeilinger and W States Under Lorentz Transformations
Constructing the reduced density matrix for a system of three massive
spin particles described by a wave packet with Gaussian momentum
distribution and a spin part in the form of GHZ or W state, the fidelity for
the spin part of the system is investigated from the viewpoint of moving
observers in the jargon of special relativity. Using a numerical approach, it
turns out that by increasing the boost speed, the spin fidelity decreases and
reaches to a non-zero asymptotic value that depends on the momentum
distribution and the amount of momentum entanglement.Comment: 12pages, 2 figure
Synthesis, structural elucidation, spectroscopic and Hirshfeld surface analysis of a new organic cyclohexaphosphate, (C12H19N2)4(Li)2(P6O18)(H2O)4
International audienc
Influence of the drought on antioxidant and enzymatic activities of two Pinus species in humid and sub-humid climate
Pinus genus is widespread in the Mediterranean region and the most common in Tunisia. The impact of high temperatures in the mid-summer period (July 2015 and July 2016) on phenols and biological properties were examined in vitro. The study was carried out in two arboreta, in humid and sub-humid climates, dry needles of Pinus pinea and Pinus pinaster were used for secondary metabolites, antioxidant activities, and enzymatic inhibitory activities. The amount of all measured parameters increased from 2015 to 2016 in the two pine species in the two arboreta. Pinus pinea produced more phenols and showed higher antioxidant activity and a-amylase and lipoxygenase inhibitory activities than Pinus pinaster. Besides, both species generally presented better biological activities and higher phenol amounts in 2016 than in 2015, being 2016 warmer and drier than 2015 in both harvest zones. It was evident that both species in every bioclimatic zones adapted to the new climate conditions producing more secondary metabolites that rendered better antioxidant and inhibitory enzymatic activities. These findings confirmed the impact of mid-summer water deficits on pine species in the context of climate change and help to select the most resistant species for future reforestation.info:eu-repo/semantics/publishedVersio
Immune heterogeneity of head and tail pancreatic lymph nodes in non-obese diabetic mice
The pancreatic lymph node is critical to the pathogenesis of autoimmune diabetes, as it constitutes the initial site for the priming of autoreactive T cells. In this study, we compared the histopathology of the head pancreatic lymph node (HPLN) to the tail pancreatic lymph node (TPLN) in NOD mice. HPLNs and TPLNs were harvested from 4 week-, 8 week-, and 12 week-old NOD mice, and their microvasculature, extracellular matrix, and immune cell subsets were characterized. The percentages of B cells and antigen-presenting cells (APCs) were much higher in the HPLN, as compared to the TPLN. Notably, the HPLNs of 12 week-old mice were characterized by greater expansion of high endothelial venules (HEVs) and lymphatic vessels in comparison to the TPLNs. Finally, we observed a higher density of extracellular matrix (ECM) fibers surrounding the lymphatic vasculature in the HPLNs than in the TPLNs. These data for the first time demonstrate that the HPLN possesses a different immune microanatomy and organization from the TPLN. These novel observations unveil a major phenotypic difference between two types of LNs from the same organ and may highlight an independent fundamental role played by each PLN during the establishment of T1D
Concurrent Acquisition of a Single Nucleotide Polymorphism in Diverse Influenza H5N1 Clade 2.2 Sub-clades
Highly pathogenic Influenza A H5N1 was first identified in Guangdong Province in 1996, followed by human cases in Hong Kong in 1997. The number of confirmed human cases now exceeds 300, and the associated Case Fatality Rate exceeds 60%. The genetic diversity of the serotype continues to increase. Four distinct clades or sub-clades have been linked to human cases. The gradual genetic changes identified in the sub-clades have been attributed to copy errors by viral encoded polymerases that lack an editing function, thereby resulting in antigenic drift. We report here the concurrent acquisition of the same polymorphism by multiple, genetically distinct, clade 2.2 sub-clades in Egypt, Russia, and Ghana. These changes are not easily explained by the current theory of “random mutation” through copy error, and are more easily explained by recombination with a common source. This conclusion is supported by additional polymorphisms shared by clade 2.2 isolates in Egypt and Germany
Demonstration of the Complementarity of One- and Two-Photon Interference
The visibilities of second-order (single-photon) and fourth-order
(two-photon) interference have been observed in a Young's double-slit
experiment using light generated by spontaneous parametric down-conversion and
a photon-counting intensified CCD camera. Coherence and entanglement underlie
one-and two-photon interference, respectively. As the effective source size is
increased, coherence is diminished while entanglement is enhanced, so that the
visibility of single-photon interference decreases while that of two-photon
interference increases. This is the first experimental demonstration of the
complementarity between single- and two-photon interference (coherence and
entanglement) in the spatial domain.Comment: 21 pages, 7 figure
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