1,702 research outputs found
Giant Magnetoresistance in Nanogranular Magnets
We study the giant magnetoresistance of nanogranular magnets in the presence
of an external magnetic field and finite temperature. We show that the
magnetization of arrays of nanogranular magnets has hysteretic behaviour at low
temperatures leading to a double peak in the magnetoresistance which coalesces
at high temperatures into a single peak. We numerically calculate the
magnetization of magnetic domains and the motion of domain walls in this system
using a combined mean-field approach and a model for an elastic membrane moving
in a random medium, respectively. From the obtained results, we calculate the
electric resistivity as a function of magnetic field and temperature. Our
findings show excellent agreement with various experimental data.Comment: 4 pages, 3 figure
Thermoelectric performance of weakly coupled granular materials
We study thermoelectric properties of inhomogeneous nanogranular materials
for weak tunneling conductance between the grains, g_t < 1. We calculate the
thermopower and figure of merit taking into account the shift of the chemical
potential and the asymmetry of the density of states in the vicinity of the
Fermi surface. We show that the weak coupling between the grains leads to a
high thermopower and low thermal conductivity resulting in relatively high
values of the figure of merit on the order of one. We estimate the temperature
at which the figure of merit has its maximum value for two- and
three-dimensional samples. Our results are applicable for many emerging
materials, including artificially self-assembled nanoparticle arrays.Comment: 4 pages, 3 figure
Social -psychological training as a method for the formation of emotional intelligence of students –Psychology
This paper presents the results of an empirical study of emotional intelligence in a sample of psychology students 1 course, described the features of the socio-psychological training as a method of formation of emotional intelligence.В статье представлены результаты эмпирического исследования эмоционального интеллекта на выборке студентов-психологов 1-го курса обучения, описаны особенности социально-психологического тренинга как метода формирования эмоционального интеллекта
Universal Description of Granular Metals at Low Temperatures: Granular Fermi Liquid
We present a unified description of the low temperature phase of granular
metals that reveals a striking generality of the low temperature behaviors. Our
model explains the universality of the low-temperature conductivity that
coincides exactly with that of the homogeneously disordered systems and enables
a straightforward derivation of low temperature characteristics of disordered
conductors.Comment: 4 pages, 1 figur
Single-electron latch with granular film charge leakage suppressor
A single-electron latch is a device that can be used as a building block for
Quantum-dot Cellular Automata (QCA) circuits. It consists of three nanoscale
metal "dots" connected in series by tunnel junctions; charging of the dots is
controlled by three electrostatic gates. One very important feature of a
single-electron latch is its ability to store ("latch") information represented
by the location of a single electron within the three dots. To obtain latching,
the undesired leakage of charge during the retention time must be suppressed.
Previously, to achieve this goal, multiple tunnel junctions were used to
connect the three dots. However, this method of charge leakage suppression
requires an additional compensation of the background charges affecting each
parasitic dot in the array of junctions. We report a single-electron latch
where a granular metal film is used to fabricate the middle dot in the latch
which concurrently acts as a charge leakage suppressor. This latch has no
parasitic dots, therefore the background charge compensation procedure is
greatly simplified. We discuss the origins of charge leakage suppression and
possible applications of granular metal dots for various single-electron
circuits.Comment: 21 pages, 4 figure
Thermal transport in granular metals
We study the electron thermal transport in granular metals at large tunnel
conductance between the grains, and not too low a temperature , where is the mean energy level spacing for a single grain.
Taking into account the electron-electron interaction effects we calculate the
thermal conductivity and show that the Wiedemann-Franz law is violated for
granular metals. We find that interaction effects suppress the thermal
conductivity less than the electrical conductivity.Comment: Replaced with published versio
Quantum charge diffusion in underdamped Josephson junctions and superconducting nanowires
The effect of quantum fluctuations on the current-voltage characteristics of
Josephson junctions and superconducting nanowires is studied in the underdamped
limit. Quantum fluctuations induce transitions between a Coulomb--blockade and
a supercurrent branch, and can significantly modify the shape of
current-voltage characteristics in the case of a highly resistive environment.
Owing to the phase-charge duality, our results can be directly extended to the
opposite overdamped limit.Comment: 6 pages, 2 figures, replaced with published versio
Quantum interference and Coulomb interaction in arrays of tunnel junctions
We study the electronic properties of an array of small metallic grains
connected by tunnel junctions. Such an array serves as a model for a granular
metal. Previous theoretical studies of junction arrays were based on models of
quantum dissipation which did not take into account the diffusive motion of
electrons within the grains. We demonstrate that these models break down at
sufficiently low temperatures: for a correct description of the screening
properties of a granular metal at low energies the diffusive nature of the
electronic motion within the grains is crucial. We present both a diagrammatic
and a functional integral approach to analyse the properties of junction
arrays. In particular, a new effective action is obtained which enables us to
describe the array at arbitrary temperature. In the low temperature limit, our
theory yields the correct, dynamically screened Coulomb interaction of a normal
metal, whereas at high temperatures the standard description in terms of
quantum dissipation is recovered.Comment: 14 pages, 7 figure
Localization and Capacitance Fluctuations in Disordered Au Nano-junctions
Nano-junctions, containing atomic-scale gold contacts between strongly
disordered leads, exhibit different transport properties at room temperature
and at low temperature. At room temperature, the nano-junctions exhibit
conductance quantization effects. At low temperatures, the contacts exhibit
Coulomb-Blockade. We show that the differences between the room-temperature and
low temperature properties arise from the localization of electronic states in
the leads. The charging energy and capacitance of the nano-junctions exhibit
strong fluctuations with applied magnetic field at low temperature, as
predicted theoretically.Comment: 20 pages 8 figure
Magnetoresistance of Granular Superconducting Metals in a Strong Magnetic Field
The magnetoresistance of a granular superconductor in a strong magnetic field
is considered. It is assumed that this field destroys the superconducting gap
in each grain, such that all interesting effects considered in the paper are
due to superconducting fluctuations. The conductance of the system is assumed
to be large, which allows us to neglect all localization effects as well as the
Coulomb interaction. It is shown that at low temperatures the superconducting
fluctuations reduce the one-particle density of states but do not contribute to
transport. As a result, the resistivity of the normal state exceeds the
classical resistivity approaching the latter only in the limit of extremely
strong magnetic fields, and this leads to a negative magnetoresistance. We
present detailed calculations of physical quatities relevant for describing the
effect and make a comparison with existing experiments.Comment: 24 pages, 10 figure
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