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The headline on this is misleading. The fact is that since "high-temperature" superconductivity was discovered in 1986 (critical temperature 35 kelvins at first) and improved on (topping out at about 130 kelvins or a still frigid -143C), no one has been able to come up with a theory to explain the behavior.

This finding looks like an important step on the way to understanding how high-temperature superconductivity is like ordinary superconductivity (explained by "BCS" theory in 1957, or 46 years after its discovery, as an exchange of quanta of vibrational energy between paired electrons--Cooper pairs) and how it differs.

Then even if someone develops a full BCS-like theory, it is unlikely to lead to room temperature superconductivity. That will almost certainly require a new class of materials, and will, I suspect, be discovered by serendipity rather than design.

Perhaps this excerpt from my 20th-century history Physics: Decade by Decade will offer some insight in the reason we still face a long road to room-temperature superconductivity. The book discusses superconductivity in detail in the chapters on the 1910s, the 1950s, and the 1980s (from which the excerpt is drawn).

So why did Bednorz and Müller look at ceramics rather than alloys? Part of it was simple curiosity, wondering whether the BCS theory applied to other materials as well as alloys. They soon found that it didn't. One of the ceramics they were looking at had a superconducting transition temperature significantly higher than that predicted by BCS theory. Since the transition temperature was still very low, the difference measured in kelvins was tiny; but it was significant on a percentage basis. They saw that result as a hint of a different route to superconductivity beyond Cooper pairs and phonons, and they began looking for other ceramics with significantly higher transition points. In early 1986, they discovered superconductivity in a class of ceramics called perovskites. One in particular, lanthium-barium-copper oxide, was superconducting up to 35K, a 50% increase above any previously discovered superconductor. That set off a race to find ceramics that were superconducting at above the temperature of liquid nitrogen. Within months, materials scientists succeeded. Suddenly, the new goal was room temperature (roughly 300K), but progress stalled again at about 130K, not far above the maximum transition temperature that had been achieved when Bednorz and Müller accepted the 1987 Nobel Prize for physics.


Because ceramics are brittle, they are hard to form into wires, which has limited their practical applications to date. Room temperature superconductivity still seems to be an unreachable goal for two reasons. First, physicists have yet to develop a new theory or a refinement of the BCS theory to explain what is happening in these ceramics. Second, there has been no progress toward superconductivity at higher temperatures since the late 1980s. Based on the history of superconductivity, the field may well yield more Nobel Prizes if someone makes a breakthrough in either of those two areas.


(Copyright 2007, Alfred B. Bortz)

Fred Bortz -- Science and technology books for young readers (www.fredbortz.com) and Science book reviews (www.scienceshelf.com)