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Josephson effect in SXS junctions
We investigate the Josephson effect in SXS junctions,
where S is a superconducting material with a ferromagnetic exchange
field, and X a weak link. The critical current increases with the
(antiparallel) exchange fields if the distribution of transmission eigenvalues
of the X-layer has its maximum weight at small values. This exchange field
enhancement of the supercurrent does not exist if X is a diffusive normal
metal. At low temperatures, there is a correspondence between the critical
current in an SIS junction with collinear orientations of
the two exchange fields, and the AC supercurrent amplitude in an SIS tunnel
junction. The difference of the exchange fields in an SIS junction corresponds to the potential difference in
an SIS junction; i.e., the singularity in [in an SIS
junction] at is the analogue of the Riedel peak.
We also discuss the AC Josephson effect in SIS junctions.Comment: 5 pages, 5 figure
Proximity effect in atomic-scaled hybrid superconductor/ferromagnet structures: crucial role of electron spectra
We study the influence of the configuration of the majority and minority spin
subbands of electron spectra on the properties of atomic-scaled
superconductor-ferromagnet S-F-S and F-S-F hybrid structures. At low
temperatures, the S/F/S junction is either a 0 or junction depending on the
energy shift between S and F materials and the anisotropy of the Fermi
surfaces. We found that the spin switch effect in F/S/F system can be reversed
if the minority spin electron spectra in F metal is of the hole-like type
Invariant Peano curves of expanding Thurston maps
We consider Thurston maps, i.e., branched covering maps
that are postcritically finite. In addition, we assume that is expanding in
a suitable sense. It is shown that each sufficiently high iterate of
is semi-conjugate to , where is equal to the
degree of . More precisely, for such an we construct a Peano curve
(onto), such that
(for all ).Comment: 63 pages, 12 figure
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