Josephson effect in hybrid superconductor-normal metal structures
Author
Çakır, Özgür
Advisor
Kulik, Igor
Date
2000Publisher
Bilkent University
Language
English
Type
ThesisItem Usage Stats
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Abstract
The clean SNS junction, with a phase difference x across the normal metal
barrier and without Fermi level mismatch between the components, is modeled
by a step like pair potential. The quasiclassical equations are obtained from the
Gorkov equations by the elimination of crystal momenta and are valid in the
existence of only the off-diagonal potential(pair potential). Then for the SNS
junction, the quasiclassical Green functions are obtained. At zero temperature, in
the long barrier limit(d ^ ^o)> the current is found to have a sawtooth dependence
on the phase difference, the amplitude of which is inversely proportional to the
thickness of the normal layer. At finite temperatures in the limits d and
Tc T, the current is found to have exponential dependence on the thickness of
the normal layer, T exp(—d/^7’) sin y, .where = vfI2ttT.
An extension of single SNS structures is the periodic SNS structure which
may as well exhibit Josephson effect. It is simulated by a periodic step-wise pair
potential, where the phase of the pair potential changes by some constant value
in subsequent superconducting islands. Bogoliubov equations in the semicla.ssical limit are employed, yielding the density of states(DOS). In the DOS, there
appears some forbidden energy regions, which point out to a band structure.
Keywords
SuperconductivityJosephson Effect
Hybrid Structures
Weak Links
Proximity Effect
Quasiclassical Green Functions
Bogoliubov-de Gennes Equations