The d-wave pairing symmetry of the high-Tc superconductors
provides the opportunity to realize novel Josephson
quantum-structures, characterized by built-in π-phase shifts.
Such elements are of interest for basic studies and have also been
proposed as new components in superconducting
Using thin-film ramp-type Josephson contacts between a high-Tc
and a low-Tc superconductor, experiments to study the
d-wave-induced π-phase-shift effects in planar Josephson
arrays have been enabled. Based on this, various novel
quantum-structures have been realized, including 1-D and 2-D
arrays of corner junctions and π-rings.
The investigations were first performed on 1-D Josephson arrays
with a zigzag configuration. Apart from demonstrating the
experimental realization of high-quality complex Josephson-arrays
comprising the high-Tc cuprate YBCO, the zigzag Josephson
junctions were shown to be viable structures to resolve
controversial issues regarding the pairing symmetry in the
high-Tc cuprate superconductors. This was further demonstrated
by the order parameter symmetry test experiments performed based
on NCCO/Au/Nb zigzag junctions.
Another interesting aspect of the zigzag junctions is that, under
certain conditions, the lowest-energy ground state of the system
is characterized by a spontaneous generation of a half-integer
magnetic-flux quantum at each corner. The half flux quanta effects
in zigzag junctions have been studied using scanning SQUID
To study the magnetic coupling between the half magnetic-flux
quanta, arrays of electrically isolated π-rings have been
realized. A preferentially antiferromagnetic ordering of
half-integer magnetic-flux quanta was observed for electrically
isolated Josephson structures, when sufficiently closely spaced.
This presents an analogue to the antiferromagnetic Ising-spin
system, and opens a possibility to realize various two-dimensional
Ising antiferromagnetic systems.
Finally, the work described in this thesis will provide a diverse
basis for both fundamental studies and potential applications,
including further investigations on details of the order parameter
symmetry in the high-Tc cuprates, half-integer magnetic-flux
quantum effects, correlation in two-dimensional Ising models, and
to realize the theoretically proposed elements for superconducting
(quantum) electronics such as complementary Josephson circuits and