Yong-Jihn Kim
A New Approach to the Josephson Effect
(266K, La Tex with 3 eps files)

ABSTRACT.  We introduce a new approach to the Josephson effect 
in SIS tunnel junctions. 
The Josephson coupling energy is calculated from 
the overlap of real space Cooper pair wavefunctions in two 
superconductors through an insulating barrier. 
It is shown that the Josephson tunneling is limited by the 
size of the Cooper pair and its shrinking during the tunneling. 
Therefore, the Josephson coupling energy and the critical 
current become extremely small in high $T_{c}$ superconductors, including $MgB_{2}$. 
This shrinking also causes the observed DC supercurrent in low $T_{c}$ superconductors, such as Pb and Sn, to fall off much faster than $1/R_{n}$ for tunneling resistance $R_{n}$ above several ohms. 
Consequently there is a material-dependent threshold resistance, above which 
the supercurrent decreases much faster with increasing resistance. 
The impurity-induced shrinking is also shown to limit the critical current. 
Furthermore, the (weak) temperature dependence of the Cooper pair size is 
found to contribute to the temperature dependence of the DC supercurrent.