7 research outputs found
Unconventional superconducting states induced in a ferromagnet by a d-wave superconductor
We develop a quasi-classical theory for the superconducting proximity effect
in a ballistic ferromagnetic layer in contact with a d-wave superconductor. In
agreement with recent experiments we find that the density of states oscillate
around the normal state value with varying the thickness of the ferromagnetic
layer. We show that the phase, the amplitude, and the period of these
oscillations depend on the orientation of the superconductor. This effect
reveals spatial oscillations and anisotropy of the induced superconducting
correlations in the ferromagnet.Comment: 4 pages, 4 figures (included
Magnetic field effect in hybrid nanostructures
We examine the effect of the magnetic field on the proximity effect in
nanostructures, self consistently using the Bogoliubov-deGennes formalism
within the two dimensional extended Hubbard model. We calculate the local
density of states and the pair amplitude. We study several nanostructures:
superconductor - two dimensional electron gas, superconductor - ferromagnet. In
these structures the magnetic field can be considered as a modulation parameter
for the proximity effect.Comment: 9 pages, 9 figure
Andreev bound states in normal and ferromagnet/high-Tc superconducting tunnel junctions
Ag/BSCCO and Fe/Ag/BSCCO planar tunnel junctions were constructed in order to
study experimentally the effect of an exchange potential on the spin polarized
current transported through Andreev bound states appearing at the interface
with a superconductor with broken time reversal pairing symmetry. The zero bias
conductance peak (ZBCP) resulting from the Andreev bound states (ABS) is split
into two symmetric peaks shifted at finite energies when the counterlectrode is
normal. Four asymmetric peaks are observed when the ferromagnetic spin
polarized charge reservoir is added, due to the combined effect of a
spin-filtering exchange energy in the barrier, which is a spin dependent
phenomenon, and the spin independent effect of a broken time reversal symmetry
(BTRS). The polarization in the iron layer leads to asymmetry. Due to the shift
of ABS peaks to finite energies, the conductance at zero energy behaves as
predicted by recent theoretical developments for pure d-wave junctions without
Andreev reflections.Comment: 4 pages, 2 figures. Submitted to Physica
Local Density of States and Order Parameter Configurations in Layered Ferromagnet-Superconductor Structures
We analyze the local density of states (LDOS) of heterostructures consisting
of alternating ferromagnet, , and superconductor, , layers. We consider
structures of the and type, with thin nanometer scale and
layers, within the ballistic regime. The spin-splitting effects of the
ferromagnet and the mutual coupling between the regions, yield several
nontrivial stable and metastable pair amplitude configurations, and we find
that the details of the spatial behavior of the pair amplitude govern the
calculated electronic spectra. These are reflected in discernible signatures of
the LDOS. The roles that the magnetic exchange energy, interface scattering
strength, and the Fermi wavevector mismatch each have on the LDOS for the
different allowed junction configurations, are systematically investigated.Comment: 20 pages, 10 figures. Figures are screen captures, high resolution
figures are available from either autho
Superconductor-Ferromagnet Bi-Layers: a Comparison of s-Wave and d-Wave Order Parameters
We study superconductor-ferromagnet bi-layers, not only for s-wave but also
for d-wave superconductors. We observe oscillations of the critical temperature
when varying the thickness of the ferromagnetic layer for both s-wave and
d-wave superconductors. However, for a rotated d-wave order parameter the
critical temperature differs considerably from that for the unrotated case. In
addition we calculate the density of states for different thicknesses of the
ferromagnetic layer; the results reflect the oscillatory behaviour of the
superconducting correlations.Comment: 11 pages, 5 figures, accepted for publication in J. Phys.: Condens.
Matte
Spin polarized transport in the weak-link between -wave superconductors
The spin current in the Josephson junction as a weak link (interface) between
misorientated triplet superconductors is investigated theoretically for the
models of the order parameter in . Green functions of the system are
obtained from the quasiclassical Eilenberger equations. The analytical results
for the charge and spin currents are illustrated by numerical calculations for
the certain misorientation angles of gap vector of superconductors. As the main
result of this paper, it is found that, at some values of the phase difference,
at which the charge current is exactly zero, the spin current has its maximum
value. Furthermore, it is shown that the origin of spin current is the
misorientation between gap vectors of triplet superconductors.Comment: 7pages, 9 figure