886 research outputs found
Bose-Einstein condensation of semi-hard bosons in S=1 dimerized organic compound F2PNNNO
An analysis of the energy spectrum and the magnetization curve of
two-dimensional organic antiferromagnet F2PNNNO with a spin-one dimerized
structure shows that a behavior of the compound in an external magnetic field
can be explained within a lattice boson model with an extended Pauli's
exclusion principle, i.e. no more than two bosons per a dimer. The unusual
magnetization curve observed experimentally in the compound reflects a sequence
of phase transitions intrinsic for a lattice boson system with strong on-site
and inter-site repulsions due to a tuning of magnon density by the applied
magnetic field
On the diel rhythm of motor activity in perch [Translation from: Informatsionnyi Byulleten Biologiya Vnutrennikh Vod No.30, 12-14, 1976]
The river perch (Perca fluviatilis L.) is most active in the daytime hours, and displays seasonal changes of diel rhythm with a break of the rhythm in spring and autumn. In the present work data were obtained on the motor activity of 3 perch measuring l8-20 cm, caught by net in the littoral of a reservoir and spawned under laboratory conditions. The degree of intensity of movement of perch was judged by special experiments. The results are summarised in this short paper
Effects of fluctuations and Coulomb interaction on the transition temperature of granular superconductors
We investigate the suppression of superconducting transition temperature in
granular metallic systems due to (i) fluctuations of the order parameter
(bosonic mechanism) and (ii) Coulomb repulsion (fermionic mechanism) assuming
large tunneling conductance between the grains . We find the
correction to the superconducting transition temperature for 3 granular
samples and films. We demonstrate that if the critical temperature , where is the mean level spacing in a single grain the bosonic
mechanism is the dominant mechanism of the superconductivity suppression, while
for critical temperatures the suppression of
superconductivity is due to the fermionic mechanism.Comment: 12 pages, 9 figures, several sections clarifying the details of our
calculations are adde
Suppression of superconductivity in granular metals
We investigate the suppression of the superconducting transition temperature
due to Coulomb repulsion in granular metallic systems at large tunneling
conductance between the grains, . We find the correction to the
superconducting transition temperature for 3 granular samples and films. We
demonstrate that depending on the parameters of superconducting grains, the
corresponding granular samples can be divided into two groups: (i) the granular
samples that belong to the first group may have only insulating or
superconducting states at zero temperature depending on the bare intergranular
tunneling conductance , while (ii) the granular samples that belong to the
second group in addition have an intermediate metallic phase where
superconductivity is suppressed while the effects of the Coulomb blockade are
not yet strong.Comment: 4 pages, 3 figure
Identification of Transformer Defects via Analyzing Gases Dissolved in Oil
A description of almost all the current widely used methods used for the interpretation of the results obtained in analyzing gases dissolved in oil (AGDO) is presented. In addition, a new method for identifying defect types, an algorithm for its application, and the advantages thereof over other methods are described. A technique for testing the reliability of the AGDO interpretation methods and results obtained upon testing these methods are presented. The quality of the detection provided by the considered methods has been compared with respect to various types of defects. In the course of the testing, special attention was paid to examining the issue that different methods of AGDO interpretation can identify different number of defect types. The evaluation of the quality of the methods and the testing of their reliability have been performed for a test sample containing 134 cases of transformer damage. For each case, there is a detailed description of the defect development process (the results of analyzing and testing of a transformer for the preceding period and the records in the operational documentation), as well as the results of transformer investigation, in the course of which the cause of damage done to it has been established. © 2019, Allerton Press, Inc
Electronic theory for itinerant in-plane magnetic fluctuations in NaCoO
Starting from {\it ab-initio} band structure for NaCoO, we derive the
single-electron energies and the effective tight-binding description for the
bands using a projection procedure. We find that due to the presence
of the next-nearest-neighbor hoppings a local minimum in the electronic
dispersion close to the point of the first Brillouin zone forms.
Therefore, in addition to a large Fermi surface an electron pocket close to the
point emerges at high doping concentrations. The latter yields the new
scattering channel resulting in a peak structure of the itinerant magnetic
susceptibility at small momenta. This indicates itinerant in-plane
ferromagnetic state above certain critical concentration , in agreement
with neutron scattering data. Below the magnetic susceptibility shows a
tendency towards the antiferromagnetic fluctuations. We estimate the value of
within the rigid band model and within the Hubbard model
with infinite on-site Coulomb repulsion consistent with the experimental phase
diagram.Comment: 4 pages, 4 figures; LDA calculations were done with Na in the
symmetric 2d position contrary to the 6h position in a previous version of
this pape
Granular Electronic Systems
A granular metal is an array of metallic nano-particles imbedded into an
insulating matrix. Tuning the intergranular coupling strength a granular system
can be transformed into either a good metal or an insulator and, in case of
superconducting particles, experience superconductor-insulator transition. The
ease of adjusting electronic properties of granular metals makes them most
suitable for fundamental studies of disordered solids and assures them a
fundamental role for nanotechnological applications. This Review discusses
recent important theoretical advances in the study of granular metals,
emphasizing on the interplay of disorder, quantum effects, fluctuations and
effects of confinement in formation of electronic transport and thermodynamic
properties of granular materials.Comment: 51 pages, 23 figures, submitted to Reviews of Modern Physic
Hall Effect in the mixed state of moderately clean superconductors
The Hall conductivity in the mixed state of a clean () type-II
s-wave superconductor is determined from a microscopic calculation within a
quasiclassical approximation. We find that below the superconducting transition
the contribution to the transverse conductivity due to dynamical fluctuations
of the order parameter is compensated by the modification of the quasiparticle
contribution. In this regime the nonlinear behaviour of the Hall angle is
governed by the change in the effective quasiparticle scattering rate due to
the reduction in the density of states at the Fermi level. The connection with
experimental results is discussed
Electrodynamics of Fulde-Ferrell-Larkin-Ovchinnikov superconducting state
We develop the Ginzburg-Landau theory of the vortex lattice in clean
isotropic three-dimensional superconductors at large Maki parameter, when
inhomogeneous Fulde-Ferrell-Larkin-Ovchinnikov state is favored. We show that
diamagnetic superfluid currents mainly come from paramagnetic interaction of
electron spins with local magnetic field, and not from kinetic energy response
to the external field as usual. We find that the stable vortex lattice keeps
its triangular structure as in usual Abrikosov mixed state, while the internal
magnetic field acquires components perpendicular to applied magnetic field.
Experimental possibilities related to this prediction are discussed.Comment: 5 pages, 1 figur
Universal description of the rotational-vibrational spectrum of three particles with zero-range interactions
A comprehensive universal description of the rotational-vibrational spectrum
for two identical particles of mass and the third particle of the mass
in the zero-range limit of the interaction between different particles is
given for arbitrary values of the mass ratio and the total angular
momentum . If the two-body scattering length is positive, a number of
vibrational states is finite for , zero for
, and infinite for . If the two-body scattering
length is negative, a number of states is either zero for or
infinite for . For a finite number of vibrational states, all the
binding energies are described by the universal function , where ,
,and is the vibrational
quantum number. This scaling dependence is in agreement with the numerical
calculations for and only slightly deviates from those for .
The universal description implies that the critical values and
increase as and ,
respectively, while a number of vibrational states for is
within the range
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