29,476 research outputs found
Anderson localization on the Falicov-Kimball model with Coulomb disorder
The role of Coulomb disorder is analysed in the Anderson-Falicov-Kimball
model. Phase diagrams of correlated and disordered electron systems are
calculated within dynamical mean-field theory applied to the Bethe lattice, in
which metal-insulator transitions led by structural and Coulomb disorders and
correlation can be identified. Metallic, Mott insulator, and Anderson insulator
phases, as well as the crossover between them are studied in this perspective.
We show that Coulomb disorder has a relevant role in the phase-transition
behavior as the system is led towards the insulator regime
Anomalous Lattice Response at the Mott Transition in a Quasi-2D Organic Conductor
Discontinuous changes of the lattice parameters at the Mott metal-insulator
transition are detected by high-resolution dilatometry on deuterated crystals
of the layered organic conductor -(BEDT-TTF)Cu[N(CN)]Br.
The uniaxial expansivities uncover a striking and unexpected anisotropy,
notably a zero-effect along the in-plane c-axis along which the electronic
interactions are relatively strong. A huge thermal expansion anomaly is
observed near the end-point of the first-order transition line enabling to
explore the critical behavior with very high sensitivity. The analysis yields
critical fluctuations with an exponent 0.8 0.15
at odds with the novel criticality recently proposed for these materials
[Kagawa \textit{et al.}, Nature \textbf{436}, 534 (2005)]. Our data suggest an
intricate role of the lattice degrees of freedom in the Mott transition for the
present materials.Comment: 4 pages, 4 figure
Vacuumless kinks systems from vacuum ones, an example
Some years ago, Cho and Vilenkin, introduced a model which presents
topological solutions, despite not having degenerate vacua as is usually
expected. Here we present a new model with topological defects, connecting
degenerate vacua but which in a certain limit recovers precisely the one
proposed originally by Cho and Vilenkin. In other words, we found a kind of
parent model for the so called vacuumless model. Then the idea is extended to a
model recently introduced by Bazeia et al. Finally, we trace some comments the
case of the Liouville model.Comment: 11 pages, 4 figure
Alterações nas propriedades fÃsicas de um Latossolo Amarelo Distrocoeso em função da aplicação de carvão vegetal.
A necessidade de adequação dos sistemas de produção agrÃcola tem estimulado a busca de novos manejos do solo. A evolução tem procurado uma maior capacidade para diminuir a emissão e aumentar a conversão do carbono do solo
Components of multifractality in the Central England Temperature anomaly series
We study the multifractal nature of the Central England Temperature (CET)
anomaly, a time series that spans more than 200 years. The series is analyzed
as a complete data set and considering a sliding window of 11 years. In both
cases, we quantify the broadness of the multifractal spectrum as well as its
components defined by the deviations from the Gaussian distribution and the
influence of the dependence between measurements. The results show that the
chief contribution to the multifractal structure comes from the dynamical
dependencies, mainly the weak ones, followed by a residual contribution of the
deviations from Gaussianity. However, using the sliding window, we verify that
the spikes in the non-Gaussian contribution occur at very close dates
associated with climate changes determined in previous works by component
analysis methods. Moreover, the strong non-Gaussian contribution found in the
multifractal measures from the 1960s onwards is in agreement with global
results very recently proposed in the literature.Comment: 21 pages, 10 figure
Tipo de estaca e concentração de ácido indol butÃrico no enraizamento de alecrim da chapada.
Suplemento. Edição dos Anais do 52 Congresso Brasileiro de Olericultura, Salvador, jul. 2012
Spin-polarized current and shot noise in the presence of spin flip in a quantum dot via nonequilibrium Green's functions
Using non-equilibrium Green functions we calculate the spin-polarized current
and shot noise in a ferromagnet--quantum-dot--ferromagnet (FM-QD-FM) system.
Both parallel (P) and antiparallel (AP) magnetic configurations are considered.
Coulomb interaction and coherent spin-flip (similar to a transverse magnetic
field) are taken into account within the dot. We find that the interplay
between Coulomb interaction and spin accumulation in the dot can result in a
bias-dependent current polarization . In particular, can be
suppressed in the P alignment and enhanced in the AP case depending on the bias
voltage. The coherent spin-flip can also result in a switch of the current
polarization from the emitter to the collector lead. Interestingly, for a
particular set of parameters it is possible to have a polarized current in the
collector and an unpolarized current in the emitter lead. We also found a
suppression of the Fano factor to values well below 0.5.Comment: Published version. 13 pages, 7 figure
- …