NEWS of a scientific breakthrough delights the press and public. But too often, justified elation over an addition to knowledge is overshadowed by false hopes for the practical goodies it may bring. So it is proving to be with the famous high-temperature superconductors. Their discovery three years ago amazed physicists and tantalized commercial and political leaders. But instead of appearing in new products, the materials are challenging scientists to understand how they work.
The wonder materials are called superconductors because, below a ``critical'' temperature, they lose all electrical resistance - that is, they conduct electric currents with no losses. The key point about them is that their critical temperatures are some 10 to 30 times as high as those of any superconductor known before.
Traditional superconductors operate within a few degrees of absolute zero (minus 273.15 degrees C or minus 459.67 degrees F). They have to be cooled by hard-to-handle liquid helium. Some of the new materials have critical temperatures as high as, or higher than, liquid nitrogen's boiling point of 77 degrees above absolute zero. Liquid nitrogen is much easier to handle than liquid helium. This raised hopes for large-scale use of nitrogen-cooled superconductors or even for finding superconductors that work at room temperature.
Enthusiasts have predicted such wonders as magnetically levitated trains or long-distance loss-free transmission of electric power. Many nations targeted high-temperature superconductor research as essential to economic progress.
Former President Reagan considered this a top technological priority for the United States. The commission he established has recommended cooperative efforts to pursue practical development of these materials. The recently announced Consortium for Superconducting Electronics formed by AT&T, IBM, and the Massachusetts Institute of Technology is one response to this call. Membership in the consortium is open to other companies, academic groups, or government agencies.
So far, the new materials have found only a few specialized uses. What researchers have discovered is how little they understand what they are working with.
The physics involved is arcane. Physicists still don't know exactly how the materials transmit electric currents. It has to do with the interactions of electrons and atoms as they are arranged in the various materials and the role of any impurities present. Untested theories abound.
It has also become clear this year that physicists don't adequately understand the role of magnetic fields. Some superconductors (Type I) exclude magnetic fields entirely. The new materials generally are Type II superconductors. They let magnetic fields penetrate their interiors. The fields are organized into a lattice of narrow so-called flux tubes. Researchers have found that, at temperatures well below the critical temperature, this lattice becomes disorganized. Physicists say it ``melts.'' This destroys the superconducting state.
Thus the magnetic lattice ``melting'' temperature is more important than the critical temperature in determining a superconductor's utility. In many cases this may rule out liquid nitrogen as a coolant. Until this problem is understood and dealt with, ``mag-lev'' trains or loss-free power lines - to say nothing of room-temperature superconductors - will remain a speculative dream.
Scientific breakthroughs are interesting. But when the next one makes news, remember, its most likely consequence will be more work for the scientists.