319 research outputs found
Theory of tunneling spectroscopy in superconducting Sr2RuO4
A theory for tunneling spectroscopy in normal metal /insulator/triplet
superconductor junction is presented. We assume two kinds of non-unitary
triplet superconducting states which are the most promising states for
SrRuO. The calculated conductance spectra showzero-bias peaks as
well as gap structures. The existences of residual components in the spectra
reflect the non-unitary properties of superconducting states.Comment: 5pages, 4figures(included), to be published in Phys.Rev.B 56, (1997
Theory of magnetotunneling spectroscopy in spin triplet p-wave superconductors
We study the influence of a magnetic field on the zero-bias conductance
peak (ZBCP) due to zero-energy Andreev bound state (ZES) in normal metal /
unconventional superconductor. For p-wave junctions, ZBCP does not split into
two by even for sufficiently low transparent junctions, where ZBCP clearly
splits for d-wave. This unique property originates from the fact that for
p-wave superconductors, perpendicularly injected quasiparticle form ZES, which
contribute most dominantly on the tunneling conductance. In addition, we show
that for +i-wave superconductor junctions, the height of ZBCP is
sensitive to due to the formation of broken time reversal symmetry state.
We propose that tunneling spectroscopy in the presence of magnetic field,
, , is an promising method to determine the pairing
symmetry of unconventional superconductors.Comment: 4 pages, 6 figures, using jpsj2.cl
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
Spin current in ferromagnet/insulator/superconductor junctions
A theory of spin polarized tunneling spectroscopy based on a scattering
theory is given for tunneling junctions between ferromagnets and d-wave
superconductors. The spin filtering effect of an exchange field in the
insulator is also treated. We clarify that the properties of the Andreev
reflection are largely modified due to a presence of an exchange field in the
ferromagnets, and consequently the Andreev reflected quasiparticle shows an
evanescent-wave behavior depending on the injection angle of the quasiparticle.
Conductance formulas for the spin current as well as the charge current are
given as a function of the applied voltage and the spin-polarization in the
ferromagnet for arbitrary barrier heights. It is shown that the surface bound
states do not contribute to the spin current and that the zero-bias conductance
peak expected for a d-wave superconductor splits into two peaks under the
influence of the exchange interaction in the insulator.Comment: 14 pages, 11 figure
Directional tunnelling spectroscopy of a normal metal--wave superconductor junction
We calculate the normal metal--wave superconductor tunnelling spectrum
for various junction orientations and for two forms of the superconducting gap,
one which allows for point nodes and the other which allows for line nodes. For
a junction oriented with its normal parallel to the ab plane of the tetragonal
superconductor, we find that the tunnelling spectrum is strongly dependent on
orientation in the plane. The spectrum contains two peaks at energies
equivalent to the magnitudes of the gap function in the direction parallel to
the interface normal and in the direction making a angle with the
normal. These two peaks appear in both superconductors with point nodes and
line nodes, but are more prominent in the latter. For the tunnelling along the
c axis, we find a sharp peak at the gap maximum in the conductance spectrum of
the superconductor with line nodes, whereas with point nodes we find a peak
occurring at the value of the gap function along the c axis. We discuss the
relevance of our result to borocarbide systems.Comment: 16 pages, 10 figure
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