252 research outputs found
Josephson current in unconventional superconductors through an Anderson impurity
Josephson current for a system consisting of an Anderson impurity weakly
coupled to two unconventional superconductors is studied and shown to be driven
by a surface zero energy (mid-gap) bound-state. The repulsive Coulomb
interaction in the dot can turn a junction into a 0-junction. This effect
is more pronounced in p-wave superconductors while in high-temperature
superconductors with symmetry it can exit for rather large
artificial centers at which tunneling occurs within a finite region.Comment: 4 pages 3.eps figure
Kinky Behavior in Josephson Junctions
We analyze nonperturbatively the behavior of a Josephson junction in which
two BCS superconductors are coupled through an Anderson impurity. We recover
earlier perturbative results which found that a phase difference
is preferred when the impurity is singly occupied and the on-site Coulomb
interaction is large. We find a novel intermediate phase in which one of
and is stable while the other is metastable, with the
energy having a kink somewhere in between. As a consequence of the
kink, the characteristics of the junction are modified at low voltages.Comment: 7 pages, 7 encapsulated PostScript figures; figure 3 correcte
Loss of Pi-Junction Behaviour in an Interacting Impurity Josephson Junction
Using a generalization of the non-crossing approximation which incorporates
Andreev reflection, we study the properties of an infinite-U Anderson impurity
coupled to two superconducting leads. In the regime where and
are comparable, we find that the position of the sub-gap resonance in the
impurity spectral function develops a strong anomalous phase dependence-- its
energy is a minimum when the phase difference between the superconductors is
equal to . Calculating the Josephson current through the impurity, we find
that -junction behaviour is lost as the position of the bound-state moves
above the Fermi energy.Comment: 4 pages, 4 figures; labelling of Fig. 3 corrected; final published
form, only trivial change
Study Of Mass Losses Of Cauliflower At Storage Depending On A Packing Way
Tissues of fresh vegetables are characterized by the high quantity of moisture (80…96 %), active metabolism, low resistance to mechanical lesions, are spoiled fast. Metabolism in cells of tissues, so mass losses, depends on the content of water and dry substances.It is impossible to manage abiotic factors under conditions of open soil. So, there appears a necessity to study the influence of abiotic factors on the process of mass decrease at cauliflower storage that gives a possibility to prognosticate its mass losses and aptitude to storage.The aim of the study was to analyze the influence of weather conditions of the vegetation period of cauliflower, volume, specific mass and porosity of heads and packing methods on the intensity of natural mass losses of cauliflower at storage. The research gives a possibility to decrease natural losses of cauliflower heads and to prolong the storage duration of it. Cauliflower mass losses at the expanse of water evaporation depend on weather conditions of the vegetation period of the plant. It has been established, that there is a middle force reverse connection with the coefficient correlation r=–0,465 between the intensity of water evaporation at cauliflower heads storage and GTC, middle force connection with the coefficient correlation r=0,437 – with the average day temperature, and strong reverse connection r=–0,776 with the relative air humidity. There was elaborated the regression equation that gives an understanding about mass losses of cauliflower heads, packed in PF, at the expanse of water evaporation.The intensity of water evaporation of cauliflower at storage depends on package method. At packing in a stretch-film (SF), the intensity of moisture decrease, % a day, was the least, equal to 0,30–0,31. The ratio between moisture losses to ones of dry substances was 0,45–0,68. At packing in a performed stretch-film (PSF), the intensity of moisture decrease, % a day, was higher a little – 0,37–0,43.The more storage duration of cauliflower of late ripeness was provided by individual packing of heads in a polyethylene stretch-film. This packing type provided less total natural losses of products: in Skywoker F1– 6,0 %, in Kasper F1 and Santamaria F1 – 6,3 %. Natural losses for a day in variants with using a stretch-film were within 0,05–0,06 % depending on hybrid
Strong quantum fluctuation of vortices in the new superconductor
By using transport and magnetic measurement, the upper critical field
and the irreversibility line has been determined. A
big separation between and has been found showing the
existence of a quantum vortex liquid state induced by quantum fluctuation of
vortices in the new superconductor . Further investigation on the
magnetic relaxation shows that both the quantum tunneling and the thermally
activated flux creep weakly depends on temperature. But when the melting field
is approached, a drastic rising of the relaxation rate is observed.
This may imply that the melting of the vortex matter at a finite temperature is
also induced by the quantum fluctuation of vortices.Comment: 4 pages, 4 figure
Variance of transmitted power in multichannel dissipative ergodic structures invariant under time reversal
We use random matrix theory (RMT) to study the first two moments of the wave
power transmitted in time reversal invariant systems having ergodic motion.
Dissipation is modeled by a number of loss channels of variable coupling
strength. To make a connection with ultrasonic experiments on ergodic
elastodynamic billiards, the channels injecting and collecting the waves are
assumed to be negligibly coupled to the medium, and to contribute essentially
no dissipation. Within the RMT model we calculate the quantities of interest
exactly, employing the supersymmetry technique. This approach is found to be
more accurate than another method based on simplifying naive assumptions for
the statistics of the eigenfrequencies and the eigenfunctions. The results of
the supersymmetric method are confirmed by Monte Carlo numerical simulation and
are used to reveal a possible source of the disagreement between the
predictions of the naive theory and ultrasonic measurements.Comment: 10 pages, 2 figure
Quantum phase transition in a minimal model for the Kondo effect in a Josephson junction
We propose a minimal model for the Josephson current through a quantum dot in
a Kondo regime. We start with the model that consists of an Anderson impurity
connected to two superconducting (SC) leads with the gaps
, where for the lead at left and right. We show that, when one of the SC gaps is
much larger than the others , the starting model can
be mapped exactly onto the single-channel model, which consists of the right
lead of and the Anderson impurity with an extra onsite SC gap of
. Here and are
defined with respect to the starting model, and is the level width
due to the coupling with the left lead. Based on this simplified model, we
study the ground-state properties for the asymmetric gap, , using the numerical renormalization group (NRG) method. The
results show that the phase difference of the SC gaps , which induces the Josephson current, disturbs the screening of the
local moment to destabilize the singlet ground state typical of the Kondo
system. It can also drive the quantum phase transition to a magnetic doublet
ground state, and at the critical point the Josephson current shows a
discontinuous change. The asymmetry of the two SC gaps causes a re-entrant
magnetic phase, in which the in-gap bound state lies close to the Fermi level.Comment: 23 pages, 13 figures, typos are correcte
Patterning graphene nanostripes in substrate-supported functionalized graphene: A promising route to integrated, robust, and superior transistors
It is promising to apply quantum-mechanically confined graphene systems in
field-effect transistors. High stability, superior performance, and large-scale
integration are the main challenges facing the practical application of
graphene transistors. Our understandings of the adatom-graphene interaction
combined with recent progress in the nanofabrication technology indicate that
very stable and high-quality graphene nanostripes could be integrated in
substrate-supported functionalized (hydrogenated or fluorinated) graphene using
electron-beam lithography. We also propose that parallelizing a couple of
graphene nanostripes in a transistor should be preferred for practical
application, which is also very useful for transistors based on graphene
nanoribbon.Comment: Frontiers of Physics (2012) to be publishe
Assessment of the nephroprotective properties of the erythropoietin mimetic peptide and infliximab in kidney ischemia-reperfusion injury in rat
The present study aimed to investigate the protective effects of erythropoietin mimetic peptide (pHBSP) and infliximab on ischemic renal reperfusion injur. The experiment was performed on 70 white male Wistar laboratory rats which received recombinant erythropoietin, pHBSP, and inflixima
Superinsulator Phase of Two-Dimensional Superconductors
Using path-integral Quantum Monte Carlo we study the low-temperature phase
diagram of a two-dimensional superconductor within a phenomenological model,
where vortices have a finite mass and move in a dissipative environment modeled
by a Caldeira-Leggett term. The quantum vortex liquid at high magnetic fields
exhibits superfluidity and thus corresponds to a {\em superinsulating} phase
which is characterized by a nonlinear voltage-current law for an infinite
system in the absence of pinning. This superinsulating phase is shifted to
higher magnetic fields in the presence of dissipation.Comment: 8 pages, 3 figures, to appear in Phys. Rev. Lett. (Oktober 1998
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