556 research outputs found
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
Beware the Boojum: Caveats and Strengths of Avian Radar
Radar provides a useful and powerful tool to wildlife biologists and ornithologists. However, radar also has the potential for errors on a scale not previously possible. In this paper, we focus on the strengths and limitations of avian surveillance radars that use marine radar front-ends integrated with digital radar processors to provide 360° of coverage. Modern digital radar processors automatically extract target information, including such various target attributes as location, speed, heading, intensity, and radar cross-section (size) as functions of time. Such data can be stored indefinitely, providing a rich resource for ornithologists and wildlife managers. Interpreting these attributes in view of the sensor’s characteristics from which they are generated is the key to correctly deriving and exploiting application-specific information about birds and bats. We also discuss (1) weather radars and air-traffic control surveillance radars that could be used to monitor birds on larger, coarser spatial scales; (2) other nonsurveillance radar configurations, such as vertically scanning radars used for vertical profiling of birds along a particular corridor; and (3) Doppler, single-target tracking radars used for extracting radial velocity and wing-beat frequency information from individual birds for species identification purposes
Josephson effect in a weak link between borocarbides
A stationary Josephson effect is analyzed theoretically for a weak link
between borocarbide superconductors. It is shown that different models of the
order parameter result in qualitatively different current-phase relations
Theoretical study of electronic Raman scattering of Borocarbide superconductors
The electronic Raman scattering of Borocarbide superconductors is studied
based on the weak coupling theory with -wave gap symmetry. The low energy
behaviors and the relative peak positions can be naturally understood, while
the explanation of the detailed shape of the peak seems to require a
strong inelastic interaction not present in the weak coupling theory.Comment: Revtex 4 file, 9 pages and 5 figure
Dispersive Gap Mode of Phonons in Anisotropic Superconductors
We estimate the effect of the superconducting gap anisotropy in the
dispersive gap mode of phonons, which is observed by the neutron scattering on
borocarbide superconductors. We numerically analyze the phonon spectrum
considering the electron-phonon coupling, and examine contributions coming from
the gap suppression and the sign change of the pairing function on the Fermi
surface. When the sign of the pairing function is changed by the nesting
translation, the gap mode does not appear. We also discuss the suppression of
the phonon softening of the Kohn anomaly due to the onset of superconductivity.
We demonstrate that observation of the gap dispersive mode is useful for
sorting out the underlying superconducting pairing function.Comment: 7 pages, 12 figures, to be published in J. Phys. Soc. Jp
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