241 research outputs found
Quasi-one-dimensional system as a high-temperature superconductor
It is well-known that quasi-one-dimensional superconductors suffer from the
pairing fluctuations that significantly reduce the superconducting temperature
or even completely suppress any coherent behavior. Here we demonstrate that a
coupling to a robust pair condensate changes the situation dramatically. In
this case the quasi-one-dimensional system can be a high temperature
superconductor governed by the proximity to the Lifshitz transition at which
the Fermi level approaches the lower edge of the single-particle spectrum.Comment: 5 pages, 1 figur
Competitive 0 and {\pi} states in S/F multilayers: multimode approach
We have investigated the critical temperature behavior in periodic
superconductor/ ferromagnet (S/F) multilayers as a function of the
ferromagnetic layer thickness and the interface transparency. The
critical temperature exhibits a damped oscillatory behavior in these
systems due to an exchange field in the ferromagnetic material. In this work we
have performed calculations using the self-consistent multimode approach,
which is considered to be exact solving method. Using this approach we have
derived the conditions of 0 or state realization in periodic S/F
multilayers. Moreover, we have presented the comparison between the single-mode
and multimode approaches and established the limits of applicability of the
single-mode approximation, frequently used by experimentalists
Spatially-resolved probing of a non-equilibrium superconductor
Spatially resolved relaxation of non-equilibrium quasiparticles in a
superconductor at ultra-low temperatures was experimentally studied. It was
found that the quasiparticle injection through a tunnel junction results in
modification of the shape of I-V characteristic of a remote `detector'
junction. The effect depends on temperature, injection current and proximity to
the injector. The phenomena can be understood in terms of creation of
quasiparticle charge and energy disequilibrium characterized by two different
length scales m and
m. The findings are in good agreement with existing phenomenological
models, while more elaborated microscopic theory is mandatory for detailed
quantitative comparison with experiment. The results are of fundamental
importance for understanding electron transport phenomena in various
nanoelectronic circuits.Comment: 7 pages, 5 figure
Andreev current enhancement and subgap conductance of superconducting hybrid structures in the presence of a small spin-splitting field
We investigate the subgap transport properties of a S-F-Ne structure. Here S
(Ne) is a superconducting (normal) electrode, and F is either a ferromagnet or
a normal wire in the presence of an exchange or a spin- splitting Zeeman field
respectively. By solving the quasiclassical equations we first analyze the
behavior of the subgap current, known as the Andreev current, as a function of
the field strength for different values of the voltage, temperature and length
of the junction. We show that there is a critical value of the bias voltage V *
above which the Andreev current is enhanced by the spin-splitting field. This
unexpected behavior can be explained as the competition between two-particle
tunneling processes and decoherence mechanisms originated from the temperature,
voltage and exchange field respectively. We also show that at finite
temperature the Andreev current has a peak for values of the exchange field
close to the superconducting gap. Finally, we compute the differential
conductance and show that its measurement can be used as an accurate way of
determining the strength of spin-splitting fields smaller than the
superconducting gap.Comment: 5 pages, 4 figure
Formation of 24Mg* in the Splitting of 28Si Nuclei by 1-GeV Protons
The 28Si(p, p' gamma)24Mg reaction has been studied at the ITEP accelerator
by the hadron-gamma coincidence method for a proton energy of 1 GeV. Two
reaction products are detected: a 1368.6-keV gamma-ray photon accompanying the
transition of the 24Mg* nucleus from the first excited state to the ground
state and a proton p' whose momentum is measured in a magnetic spectrometer.
The measured distribution in the energy lost by the proton in interaction is
attributed to five processes: the direct knockout of a nuclear alpha cluster,
the knockout of four nucleons with a total charge number of 2, the formation of
the DeltaSi isobaric nucleus, the formation of the Delta isobar in the
interaction of the incident proton with a nuclear nucleon, and the production
of a pi meson, which is at rest in the nuclear reference frame. The last
process likely corresponds to the reaction of the formation of a deeply bound
pion state in the 28P nucleus. Such states were previously observed only on
heavy nuclei. The cross sections for the listed processes have been estimated.Comment: 14 pages, 3 figures submitted to JETP Letter
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