158 research outputs found
Charge current in ferromagnet - triplet superconductor junctions
We calculate the tunneling conductance spectra of a ferromagnetic metal /
insulator / triplet superconductor from the reflection amplitudes using the
Blonder-Tinkham-Klapwijk (BTK) formula. For the triplet superconductor, we
assume one special -wave order parameter, having line nodes, and two two
dimensional -wave order parameters with line nodes, breaking the time
reversal symmetry. Also we examine nodeless pairing potentials. The evolution
of the spectra with the exchange potential depends solely on the topology of
the gap. The weak Andreev reflection within the ferromagnet results in the
suppression of the tunneling conductance and eliminates the resonances due to
the anisotropy of the pairing potential. The tunneling spectra splits
asymmetrically with respect to under the influence of an external
magnetic field. The results can be used to distinguish between the possible
candidate pairing states of the superconductor SrRuO.Comment: 15 pages with 8 figure
Local density of states for the corner geometry interface of d-wave superconductors, within the extended Hubbard model
The spatial variations of the order parameter, and the local density of
states (LDOS) on the corner of s-wave or -wave superconductors, as
well as in superconductor-insulator-normal metal interfaces, are calculated
self consistently using the Bogoliubov-deGennes formalism within the two
dimensional extended Hubbard model. The exact diagonalization method is used.
Due to the suppression of the dominant d-wave order parameter, the extended
s-wave order parameter is induced near the surface, that alternates its sign
for the topmost sites at adjacent edges of the lattice and decays to zero in
the bulk. The presence of surface roughness results into the appearance of the
zero band conduction peak (ZBCP) near the corner surface which lacks from the
predictions of the quasiclassical theory.Comment: 13 pages with 17 figure
Charge current in ferromagnet-superconductor junction with pairing state of broken time-reversal symmetry
We calculate the tunneling conductance spectra of a ferromagnetic
metal/insulator/superconductor using the Blonder-Tinkham-Klapwijk (BTK)
formulation. Two possible states for the superconductor are considered with the
time reversal symmetry () broken, i.e., , or
. In both cases the tunneling conductance within the gap
is suppressed with the increase of the exchange interaction due to the
suppression of the Andreev reflection. In the -wave case the
peaks that exist when the ferromagnet is a normal metal in the amplitude of the
s-wave component due to the bound state formation are reduced symmetrically,
with the increase of the exchange field, while in the
-wave case the residual density of states within the gap
develops a dip around E=0 with the increase of the exchange field. These
results would be useful to discriminate between -broken pairing states
near the surface in high- superconductorsComment: 17 pages with 11 figure
Resonant flux motion and I-V -characteristics in frustrated Josephson junctions
We describe the dynamics of fluxons moving in a frustrated Josephson junction
with p, d, and f-wave symmetry and calculate the I-V characteristics. The
behavior of fluxons is quite distinct in the long and short length junction
limit. For long junctions the intrinsic flux is bound at the center and the
moving integer fluxon or antifluxon interacts with it only when it approaches
the junction's center. For small junctions the intrinsic flux can move as a
bunched type fluxon introducing additional steps in the I-V characteristics.
Possible realization in quantum computation is presented.Comment: 21 pages, 8 figure
Fluxon-semifluxon interaction in an annular long Josephson 0-pi-junction
We investigate theoretically the interaction between integer and half-integer
Josephson vortices (fluxons and semifluxons) in an annular Josephson junction.
Semifluxons usually appear at the 0--boundary where there is a
-discontinuity of the Josephson phase. We study the simplest, but the most
interesting case of one -discontinuity in a loop, which can be created
only artificially. We show that measuring the current-voltage characteristic
after injection of an integer fluxon, one can determine the polarity of a
semifluxon. Depending on the relative polarity of fluxon and semifluxon the
static configuration may be stable or unstable, but in the dynamic state both
configurations are stable. We also calculate the depinning current of
fluxons pinned by an arbitrary fractional vortex.Comment: 8pages, 6 figures, submitted to PR
Critical currents in Josephson junctions, with unconventional pairing symmetry: versus
Phenomenological Ginzburg-Landau theory is used to calculate the possible
spontaneous vortex states that may exist at corner junctions of
-wave, (where or ) and s-wave superconductors.
We study the magnetic flux and the critical current modulation with the
junction orientation angle , the magnitude of the order parameter, and
the magnetic field . It is seen that the critical current versus the
magnetic flux relation is symmetric / asymmetric for when
the orientation is exactly such that the lobes of the dominant
-wave order parameter points towards the two junctions, which are
at right angles for the corner junction. The conclusion is that a measurement
of the relation may distinguish which symmetry ( or
) the order parameter has.Comment: 11 pages with 11 figures, Changed conten
Josephson effect test for triplet pairing symmetry
The critical current modulation and the spontaneous flux of the vortex states
in corner Josephson junctions between SrRuO and a conventional s-wave
superconductor are calculated as a function of the crystal orientation, and the
magnetic field. For SrRuO we assume two nodeless p-wave pairing states.
Also we use the nodal -wave states and , and one special p-wave state having line nodes. It is seen that the
critical current depends solely on the topology of the gap.Comment: 22 pages, 12 figure
Stability analysis of static solutions in a Josephson junction
We present all the possible solutions of a Josephson junction with bias
current and magnetic field with both inline and overlap geometry, and examine
their stability. We follow the bifurcation of new solutions as we increase the
junction length. The analytical results, in terms of elliptic functions in the
case of inline geometry, are in agreement with the numerical calculations and
explain the strong hysteretic phenomena typically seen in the calculation of
the maximum tunneling current. This suggests a different experimental approach
based on the use, instead of the external magnetic field the modulus of the
elliptic function or the related quantity the total magnetic flux to avoid
hysteretic behavior and unfold the overlapping curves.Comment: 36 pages with 17 figure
Transport properties of ferromagnet/d-wave superconductor/ferromagnet double junctions
We investigate transport properties of a trilayer made of a d-wave
superconductor connected to two ferromagnetic electrodes. Using Keldysh
formalism we show that crossed Andreev reflection and elastic cotunneling exist
also with d-wave superconductors. Their properties are controlled by the
existence of zero energy states due to the anisotropy of the d-wave pair
potential.Comment: 16 pages, 4 figures, revised versio
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