28 research outputs found
Description of hysteretic current-voltage characteristics of SNS junctions
Simplified model for current-voltage characteristics of weak links is
suggested. It is based on an approach considering the multiple Andreev
reflection in metallic Josephson junction. The model allows to calculate
current-voltage characteristics of the superconductor - normal metal -
superconductor junctions with different thicknesses of normal layer at
different temperatures. A hysteretic peculiarity of dependence is
described as result of the negative differential resistance. The
current-voltage characteristic of high- composite YBCO +BaPbO were
computed.Comment: 9 pages, 5 figures, submited to Supercond. Sci. Technol, replased
Fig.5 for more correct comparison with experimen
High-frequency longitudinal oscillations of quasi-two-dimensional electron liquid
The specific character of longitudinal collective electromagnetic
oscillations in a layered conductor with the quasi-two-dimensional electron
energy spectrum has been analyzed.Comment: 7 page
Characteristics of the electric field accompanying a longitudinal acoustic wave in a metal. Anomaly in the superconducting phase
The temperature dependence of the amplitude and phase of the electric
potential arising at a plane boundary of a conductor when a longitudinal
acoustic wave is incident normally on it is investigated theoretically and
experimentally. The surface potential is formed by two contributions, one of
which is spatially periodic inside the sample, with the period of the acoustic
field; the second is aperiodic and arises as a result of an additional
nonuniformity of the electron distribution in a surface layer of the metal. In
the nonlocal region the second contribution is dominant. The phases of these
contributions are shifted by approximately \pi /2. For metals in the normal
state the experiment is in qualitative agreement with the theory. The
superconducting transition is accompanied by catastrophically rapid vanishing
of the electric potential, in sharp contrast to the theoretical estimates,
which predict behavior similar to the BCS dependence of the attenuation
coefficient for a longitudinal sound.Comment: 9 pages, 6 figure
Anisotropy and crystallite misalignment in textured superconductors
A misalignment of anisotropic crystallites causes small values of anisotropy
and decreases the critical current density of textured polycrystalline
superconductors. To relate the crystallite misalignment and out-plane
anisotropy, the magnetic properties of the textured Bi2223 polycrystalline
superconductor were investigated. A distribution of orientation angles of
crystallites was determined using different data: scanning electron microscopy
images and hysteresis magnetization loops when an external magnetic field was
applied at different angles with respect to the texturing plane of the sample.
It was demonstrated that the standard deviation of the distribution and the
magnetic disorder angle of crystallites in textured samples can be determined
from the magnetization data in perpendicular directions. These data may be
either the irreversible magnetization measured for two different orientations
of the sample or the simultaneously measured magnetization projections parallel
and perpendicular to the magnetic field.Comment: 11 pages, 6 figure
Acoustic Cyclotron Resonance and Giant High Frequency Magnetoacoustic Oscillations in Metals with Locally Flattened Fermi Surface
We consider the effect of local flattening on the Fermi surface (FS) of a
metal upon geometric oscillations of the velocity and attenuation of ultrasonic
waves in the neighborhood of the acoustic cyclotron resonance. It is shown that
such peculiarities of the local geometry of the FS can lead to a significant
enhancement of both cyclotron resonance and geometric oscillations.
Characteristic features of the coupling of ultrasound to shortwave cyclotron
waves arising due to the local flattening of the FS are analyzed.
PACS numbers 71.18.+y; 72.15.Gd; 72.15.-vComment: 8 pages, 3 figures, text revise
Tuning the peak effect in the Y1−xNdxBa2Cu3O7−δ compound
Polycrystalline Y1−xNdxBa2Cu3O7−δ (x=0.02, 0.11, and 0.25) superconductors are synthesized. Nd atoms are uniformly distributed over grains. The magnetization loops of the samples have a pronounced second peak in a wide temperature range. The magnetization data are analyzed using the extended critical state model. It is found that the order-disorder transition of the vortex lattice is affected by doping with neodymium and temperature; the second-peak field and width decrease monotonically with increasing x value. The undoped polycrystalline YBa2Cu3O7−δ compound is assumed to exhibit the peak effect in higher magnetic fields
Tuning the peak effect in the Y1−xNdxBa2Cu3O7−δ compound
Текст статьи не публикуется в открытом доступе в соответствии с политикой журнала.Polycrystalline Y1−xNdxBa2Cu3O7−δ (x=0.02, 0.11, and 0.25) superconductors are synthesized. Nd atoms are uniformly distributed over grains. The magnetization loops of the samples have a pronounced second peak in a wide temperature range. The magnetization data are analyzed using the extended critical state model. It is found that the order-disorder transition of the vortex lattice is affected by doping with neodymium and temperature; the second-peak field and width decrease monotonically with increasing x value. The undoped polycrystalline YBa2Cu3O7−δ compound is assumed to exhibit the peak effect in higher magnetic fields