2,758 research outputs found
Temperature effects on the magnetization of quasi-one-dimensional Peierls distorted materials
It is shown that temperature acts to disrupt the magnetization of Peierls
distorted quasi-one-dimensional materials (Q1DM). The mean-field finite
temperature phase diagram for the field theory model employed is obtained by
considering both homogeneous and inhomogeneous condensates. The tricritical
points of the second order transition lines of the gap parameter and
magnetization are explicitly calculated. It is also shown that in the absence
of an external static magnetic field the magnetization is always zero, at any
temperature. As expected, temperature does not induce any magnetization effect
on Peierls distorted Q1DM.Comment: 11 pages, 2 figure
Literacy: A cultural influence on functional left-right differences in the inferior parietal cortex
The current understanding of hemispheric interaction is limited. Functional hemispheric specialization is likely to depend on both genetic and environmental factors. In the present study we investigated the importance of one factor, literacy, for the functional lateralization in the inferior parietal cortex in two independent samples of literate and illiterate subjects. The results show that the illiterate group are consistently more right-lateralized than their literate controls. In contrast, the two groups showed a similar degree of left-right differences in early speech-related regions of the superior temporal cortex. These results provide evidence suggesting that a cultural factor, literacy, influences the functional hemispheric balance in reading and verbal working memory-related regions. In a third sample, we investigated grey and white matter with voxel-based morphometry. The results showed differences between literacy groups in white matter intensities related to the mid-body region of the corpus callosum and the inferior parietal and parietotemporal regions (literate > illiterate). There were no corresponding differences in the grey matter. This suggests that the influence of literacy on brain structure related to reading and verbal working memory is affecting large-scale brain connectivity more than grey matter per se
Characterization in bi-parameter space of a non-ideal oscillator
The authors thank scientific agencies CAPES, CNPq (112952/2015-1), and FAPESP (2011/ 19269-11). M. S. Baptista also thanks EPSRC (EP/I03 2606/1).Peer reviewedPostprin
First principle theory of correlated transport through nano-junctions
We report the inclusion of electron-electron correlation in the calculation
of transport properties within an ab initio scheme. A key step is the
reformulation of Landauer's approach in terms of an effective transmittance for
the interacting electron system. We apply this framework to analyze the effect
of short range interactions on Pt atomic wires and discuss the coherent and
incoherent correction to the mean-field approach.Comment: 5 pages, 3 figure
Surface nano-patterning through styrene adsorption on Si(100)
We present an ab initio study of the structural and electronic properties of
styrene molecules adsorbed on the dimerized Si(100) surface at different
coverages, ranging from the single-molecule to the full monolayer. The
adsorption mechanism primarily involves the vinyl group via a [2+2]
cycloaddition process that leads to the formation of covalent Si-C bonds and a
local surface derelaxation, while it leaves the phenyl group almost
unperturbed. The investigation of the functionalized surface as a function of
the coverage (e.g. 0.5 -- 1 ML) and of the substrate reconstruction reveals two
major effects. The first results from Si dimer-vinyl interaction and concerns
the controlled variation of the energy bandgap of the interface. The second is
associated to phenyl-phenyl interactions, which gives rise to a regular pattern
of electronic wires at surface, stemming from the pi-pi coupling. These
findings suggest a rationale for tailoring the surface nano-patterning of the
surface, in a controlled way.Comment: 19 pages (preprint), 4 figures, supplementary materia
Alternate islands of multiple isochronous chains in wave-particle interactions
We analyze the dynamics of a relativistic particle moving in a uniform
magnetic field and perturbed by a standing electrostatic wave. We show that a
pulsed wave produces an infinite number of perturbative terms with the same
winding number, which may generate islands in the same region of phase space.
As a consequence, the number of isochronous island chains varies as a function
of the wave parameters. We observe that in all the resonances, the number of
chains is related to the amplitude of the various resonant terms. We determine
analytically the position of the periodic points and the number of island
chains as a function of the wave number and wave period. Such information is
very important when one is concerned with regular particle acceleration, since
it is necessary to adjust the initial conditions of the particle to obtain the
maximum acceleration.Comment: Submitte
Quantum normal-to-inhomogeneous superconductor phase transition in nearly two-dimensional metals
In multi-band systems, electrons from different orbitals coexist at the Fermi
surface. An attractive interaction among these quasi-particles gives rise to
inter-band or hybrid pairs which eventually condense in a superconducting
state. These quasi-particles have a natural mismatch of their Fermi
wave-vectors, , which depends on the strength of the hybridization
between their orbitals. The existence of this natural scale suggests the
possibility of inhomogeneous superconducting ground states in these systems,
even in the absence of an applied magnetic field. Furthermore, since
hybridization depends on pressure, this provides an external parameter to
control the wave-vectors mismatch at the Fermi surface. In this work, we study
the phase diagram of a two-dimensional, two-band metal with inter-band pairing.
We show that as the mismatch between the Fermi wave-vectors of the two hybrid
bands is reduced, the system presents a normal-to-inhomogeneous superconductor
quantum phase transition at a critical value of the hybridization
. The superconducting ground state for is characterized
by a wave-vector with magnitude . Here
is the superconducting gap in the homogeneous state and
the average Fermi velocity. We discuss the nature of the quantum critical point
(QCP) at and obtain the associated quantum critical exponents.Comment: 6 pages, 4 figure
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