Prof. Ora Entin-Wohlman (Department of Physics, Ben
Gurion University, Beer Sheva, Israel)
"The conductance of superconducting-normal hybrid structures"
The dc conductance of normal-superconducting hybrid structures is
discussed. It is shown that since the Bogoliubov-DeGennes (BDG) equation
does not conserve charge, its application to create a Landauer-type
approach for the conductance of the NSN system is problematic. We `mend'
this deficiency by calculating the conductance from the Kubo formula for
a ring configuration (for this geometry the solutions of the BDG
equation conserve charge). We show that the presence of a superconductor
segment within an otherwise normal metal may reduce the overall
conductance of the composite structure. This reduction enhances the
tendency of the NS composite to become insulating.
ref. arXiv:0807.4029