601 research outputs found
Effect of magnetic fluctuations on the normal state properties of Sr_2RuO_4
We investigate the normal state transport properties of SrRuO and we
show that a consistent explanation of the experimental results can be obtained
assuming that the system is near a quantum phase transition. Within the
framework of a self-consistent spin fluctuation theory, we calculate the
temperature variation of some relevant physical quantities and we discuss a
possible microscopic origin of the quantum phase transition.Comment: 5 pages, 4 figures, to appear on Europhysics Letter
Field-induced Orbital Patterns in Ferromagnetic Layered Ruthenates
We study the evolution of orbital patterns in ferromagnetic layered
ruthenates due to the competition of Coulomb interactions, compressive c axis
and orthorhombic distortions in the presence of a polarizing orbital field
coupled to the angular momentum. By means of the exact diagonalization on a 2x2
cluster and a cluster embedded analysis where inter-plaquette interaction is
treated on mean field level, we determine the ground-state phase diagram.
Specifically, we demonstrate that, via the activation of two or three of t_2g
local orbital configurations, an external field applied along different
symmetry directions can lead to inequivalent orbital correlated states.
Starting from an antiferro-orbital pattern, for the easy axis case an orbital
ordered phase is induced, having strong next nearest neighbors ferro-orbital
correlations. Otherwise, a field applied along the hard axis leads a reduction
of local orbital moment in a way to suppress the orbital order.Comment: 11 page
Does degradation from selective logging and illegal activities differently impact forest resources? A case study in Ghana
Degradation, a reduction of the ecosystem’s capacity to supply goods and services, is widespread in tropical forests and mainly caused by human disturbance. To maintain the full range of forest ecosystem services and support the development of effective conservation policies, we must understand the overall impact of degradation on different forest resources. This research investigates the response to disturbance of forest structure using several indicators: soil carbon content, arboreal richness and biodiversity, functional composition (guild and wood density), and productivity. We drew upon large field and remote sensing datasets from different forest types in Ghana, characterized by varied protection status, to investigate impacts of selective logging, and of illegal land use and resources extraction, which are the main disturbance causes in West Africa. Results indicate that functional composition and the overall number of species are less affected by degradation, while forest structure, soil carbon content and species abundance are seriously impacted, with resources distribution reflecting the protection level of the areas. Remote sensing analysis showed an increase in productivity in the last three decades, with higher resiliency to change in drier forest types, and stronger productivity correlation with solar radiation in the short dry season. The study region is affected by growing anthropogenic pressure on natural resources and by an increased climate variability: possible interactions of disturbance with climate are also discussed, together with the urgency to reduce degradation in order to preserve the full range of ecosystem functions
Coexistence of ferromagnetism and singlet superconductivity via kinetic exchange
We propose a novel mechanism for the coexistence of metallic ferromagnetism
and singlet superconductivity assuming that the magnetic instability is due to
kinetic exchange. Within this scenario, the unpaired electrons which contribute
to the magnetization have a positive feedback on the gain of the kinetic energy
in the coexisting phase by undressing the effective mass of the carriers
involved into the pairing. The evolution of the magnetization and pairing
amplitude, and the phase diagram are first analyzed for a generic kinetic
exchange model and then are determined within a specific case with spin
dependent bond-charge occupation.Comment: 4 pages, 2 figure
Anomalous metamagnetic-like transition in a FeRh/FePt interface occurring at T120 K in the field-cooled-cooling curves for low magnetic fields
We report on the magnetic properties of a special configuration of a FeRh
thin film. An anomalous behavior on the magnetisation vs. temperature was
observed when low magnetic fields are applied in the plane of a thin layer of
FeRh deposited on ordered FePt. The anomalous effect resembles a
metamagnetic transition and occur only in the field-cooled-cooling
magnetisation curve at temperatures near 120 K in samples without any heat
treatment.Comment: 7 pages, 5 figures. arXiv admin note: text overlap with
arXiv:1008.195
Plaquette operators used in the rigorous study of ground-states of the Periodic Anderson Model in dimensions
The derivation procedure of exact ground-states for the periodic Anderson
model (PAM) in restricted regions of the parameter space and D=2 dimensions
using plaquette operators is presented in detail. Using this procedure, we are
reporting for the first time exact ground-states for PAM in 2D and finite value
of the interaction, whose presence do not require the next to nearest neighbor
extension terms in the Hamiltonian. In order to do this, a completely new type
of plaquette operator is introduced for PAM, based on which a new localized
phase is deduced whose physical properties are analyzed in detail. The obtained
results provide exact theoretical data which can be used for the understanding
of system properties leading to metal-insulator transitions, strongly debated
in recent publications in the frame of PAM. In the described case, the lost of
the localization character is connected to the break-down of the long-range
density-density correlations rather than Kondo physics.Comment: 34 pages, 5 figure
Application of a portable instrument for rapid and reliable detection of SARS-CoV-2 infection in any environment
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