Ten Years of High-Temperature Superconductivity - Years of Challenges and Surprises for Science and Technology
While writing this address to young Japanese scientists, I
recall that exactly 10 years ago my colleague K. Alex Mueller
and I were making the final revisions on our manuscript about
"Possible High-Temperature Superconductivity in the Ba-La-Cu-O
System", which marked the beginning of a new and fascinating
epoch in superconductivity research.
When continuing our research on the magnetic properties of
the cuprate superconductor, we were almost certain that our
results would meet substantial skepticism in the scientific
community; the greater was our surprise when by the end of
1986 we learned that numerous groups throughout the world
had started to follow our approach in the search for high-temperature
superconductors.
Chemical modification of the original compound led to the
discovery of new cuprate phases with the record transition
temperatures rising at a rapid pace. This, however, also increased
the level of expectation concerning the time scale for the
realization of practical applications. As scientists and engineers
were facing numerous technical problems arising from the specific
properties of the cuprates, applications could not keep up
with the speed at which new compounds were discovered. The
list of achievements made in the past decade is impressive,
and the continuous progress reflects a concentrated effort
worldwide.
We recall obstacles caused by the specific material properties,
which initially seemed to rule out any meaningful application
of the ceramic layered cuprates. With the fabrication of epitaxial
films, however, it was possible to demonstrate critical current
densities of several million Amperes per cubic centimeter
as compared to a few hundred in bulk ceramics. Subsequently,
thin films became increasingly important as model systems
to study various effects due to the material properties.
experiments had significant impact on the methods of processing
bulk superconductors, in which customization on the atomic
level could enhance the critical current densities up to a
few thousand Amperes per cubic centimeter. Today, bulk high-temperature
superconductors in the form of massive components are used
for a host of prototypes ranging from current leads, current
limiters, magnetic bearings and - in form of tapes and wires
- to magnets, motors, generators, transformers and flexible
cables for power transmission.
Much closer to the market are applications based on thin epitaxial
films. So-called SQUIDs (Superconducting Quantum Interference
Devices) for the detection of very weak magnetic fields, for
example, turned out to be superior to low-temperature superconductor
versions. The highest market share, however, could have high-temperature
superconductor microwave components, such as high-quality
resonators, stable oscillators, antennas, filters and delay
lines.
With all these achievements, the role of high-temperature
superconductors in future technology seems evident. But beyond
this, customized cuprates and their specific properties may
play a significant role in impacting new technologies, probably
with applications that at present lie beyond our imagination.
Why should we be prepared for new surprises? Well, because
the subject of high-temperature superconductivity has changed
our scientific and technical environment. On the one hand,
with the cuprates as a vehicle, we are improving our skills
in creating materials by "engineering" on the atomic
scale and in performing ultrasensitive analysis. The methods
we employ to grow thin films of artificial superlattices can
easily be applied to a larger class of oxides as can the experiments
originally designed for the superconductors.
On the other hand, and possibly even more important, we have
changed our way of collaboration. With the high-temperature
superconductors as a stimulus and a point of common interest,
collaborative efforts were established across all disciplines
in solid-state sciences, and - despite a strong competitive
element in the field - with so far unprecedented intensity
on an international level. The example of high-temperature
superconductivity shows the vast potential that can be activated
when multidisciplinary and multicultural thinking is involved.
The success should create the desire not only to preserve
the current status of collaborative efforts but to extend
these to further scientific and technological topics.
Ten Years of High-Temperature Superconductivity - Years of Challenges and Surprises for Science and Technology
