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SUMMARY:Transition from metallic to tunneling regimes in superconducting m
 icroconstrictions: Excess current\, charge imbalance\, and supercurrent co
 nversion - Marianne Bauer (TCM)
DTSTART:20101105T160000Z
DTEND:20101105T163000Z
UID:TALK27260@talks.cam.ac.uk
CONTACT:Daniel Cole
DESCRIPTION:"G. E. Blonder\, M. Tinkham\, and T. M. Klapwijk\, Phys. Rev. 
 B 25\, 4515 (1982) ":http://prb.aps.org/abstract/PRB/v25/i7/p4515_1\n\nWe 
 propose a simple theory for the I-V curves of normal-superconducting micro
 constriction contacts which describes the crossover from metallic to tunne
 l junction behavior. The detailed calculations are performed within a gene
 ralized semiconductor model\, with the use of the Bogoliubov equations to 
 treat the transmission and reflection of particles at the N-S interface. B
 y including a barrier of arbitrary strength at the interface\, we have com
 puted a family of I-V curves ranging from the tunnel junction to the metal
 lic limit. Excess current\, generated by Andreev reflection\, is found to 
 vary smoothly from 4Δ/3eRN in the metallic case to zero for the tunnel ju
 nction. Charge-imbalance generation\, previously calculated only for tunne
 l barriers\, has been recalculated for an arbitrary barrier strength\, and
  detailed insight into the conversion of normal current to supercurrent at
  the interface is obtained. We emphasize that the calculated differential 
 conductance offers a particularly direct experimental test of the predicti
 ons of the model.
LOCATION:TCM Seminar Room\, Cavendish Laboratory
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