7 research outputs found
The importance of self-consistency in determining interface properties of S-I-N and D-I-N structures
We develop a method to solve the Bogoliubov de Gennes equation for
superconductors self-consistently, using the recursion method. The method
allows the pairing interaction to be either local or non-local corresponding to
and --wave superconductivity, respectively. Using this method we examine
the properties of various and interfaces. In particular we
self-consistently calculate the spatially varying density of states and the
superconducting order parameter. We see that changing the strength of the
insulating barrier, at the interface, does not, in the case of an --wave
superconductor, dramatically, change the low energy local density of states, in
the superconducting region near the interface. This is in stark contrast to
what we see in the case of a interface where the local particle density
of states is changed dramatically. Hence we deduce that in calculating such
properties as the conductance of and structures it is far more
important to carry out a self-consistent calculations in the --wave case.Comment: 14 pages, 8 figures, submitted to special issue of "Superlattices and
Microstructures
Two photon decay of the pseudoscalars, the chiral symmetry breaking corrections
The extrapolation of the decay amplitudes of the pseudoscalar mesons into two
photons from the soft meson limit where it is obtained from the axial-anomaly
to the mass shell involves the contribution of the 0^ - continuum. These chiral
symmetry breaking corrections turn out to be large. The effects of these
corrections on the calculated pi ^0 decay rate, on the values of the
singlet-octet mixing angle and on the ratios f_8 / f_pi and f_0 / f_pi are
discussed. The implications for the transition form factors gamma gamma* -->
pseudoscalars are also evaluated and confronted with the available experimental
data.Comment: Computational errors straightened and study of the implications on
the form factors of the transitions gamma gamma* --> pseudoscalars adde
Self-consistent interface properties of d and s-wave superconductors
We develop a method to solve the Bogoliubov de Gennes equation for
superconductors self-consistently, using the recursion method. The method
allows the pairing interaction to be either local or non-local corresponding to
s and d-wave superconductivity, respectively. Using this method we examine the
properties of various S-N and S-S interfaces. In particular we calculate the
spatially varying density of states and order parameter for the following
geometries (i) s-wave superconductor to normal metal, (ii) d-wave
superconductor to normal metal, (iii) d-wave superconductor to s-wave
superconductor. We show that the density of states at the interface has a
complex structure including the effects of normal surface Friedel oscillations,
the spatially varying gap and Andeev states within the gap, and the subtle
effects associated with the interplay of the gap and the normal van Hove peaks
in the density of states. In the case of bulk d-wave superconductors the
surface leads to mixing of different order parameter symmetries near the
interface and substantial local filling in of the gap.Comment: 20 pages, Latex and 8 figure