Ka. Delin et Aw. Kleinsasser, STATIONARY PROPERTIES OF HIGH-CRITICAL-TEMPERATURE PROXIMITY EFFECT JOSEPHSON-JUNCTIONS, Superconductor science and technology, 9(4), 1996, pp. 227-269
The discovery of superconductors with high critical temperatures (T-c)
has led to a considerable effort to fabricate Josephson junctions ope
rating at temperatures approaching, or even exceeding, 77 K for both s
cientific investigations and potential applications. Superconductor-no
rmal-superconductor (SNS) devices, with noble or oxide metals as norma
l interlayers, are perhaps the most widely explored high-T-c junction
type at present. Although demonstrations of individual high-T-c SNS de
vices exhibiting excellent current-voltage characteristics, high criti
cal current-resistance products, and low noise behaviour have been mad
e, reproducible devices suitable for electronic applications are elusi
ve. It is therefore important to ask how well these nominally SNS high
-T-c junctions are understood. We review the available data, with emph
asis on junction critical currents, and conclude that there is little
evidence supporting a conventional proximity effect interpretation in
the majority of reported high-T-c devices. The strongest candidates fo
r SNS behaviour are junctions in which N is a superconductor above its
transition temperature. We discuss the present experimental and theor
etical understanding of SNS junctions with emphasis on the implication
s for future research and development of these devices.