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Santa Clara Rotary Visits the Superconducting Future

Many of us remember the Jetsons–the cartoon family of the future that was just like us except that they drove an aero-car, shuttled to the moon for the weekend and got to London in an hour via transport tubes.

We haven’t seen any of these things yet. But the physics and chemistry to do them has been understood for more than a century; and recent physics advances make it more likely we’ll see them in our lifetime, and very likely our children will in theirs.

Last week, Santa Clara University physics professor Dr. Richard Barber gave Santa Clara Rotary club members a compact tutorial in the physics that might power some of these futuristic marvels: superconductors, materials that transmit electricity perfectly, with zero resistance, losing no energy as heat.

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Superconductors, however, require mind-bogglingly cold temperatures to exhibit their magical properties.

Atoms form solids by consolidating into a lattice structure, something like a jungle gym. But because the electrons are always moving, the structure is vibrating, and electrons trying to move through it to transmit electricity collide with the vibrating atoms. This is called “resistance” and the current loses energy in the form of heat.

When the atoms of a superconducting substance are chilled to a critical transformation temperature (Tc), the atomic vibration is slowed and electrons form pairs–instead of repelling each other–that carry current through the lattice. Resistance is gone and no energy is lost in heat.

Superconductors also block magnetic fields, causing a piece of superconducting material to levitate if it’s placed over a magnet. Research has shown that applying a magnetic field stronger than the repelling force of the superconductor instantly stops the superconducting.

It’s still a matter of discussion whether the ultra-cold temperature, magnetic field repulsion, or something else yet to be discovered produces the electron pairing that creates the superconductivity.

Dutch physicist Heike Kamerlingh Onnes discovered the first superconductor around 1910. The first to liquefy helium, Onnes began using it to study the effects of super-chilling materials.

He discovered that a temperature of 4 Kelvin (-452 Fahrenheit) eliminated the element mercury’s resistance to electrical current.

Subsequent researchers discovered other superconducting materials–elements, alloys, compounds–whose critical transformation points (Tc) occurred at higher temperatures. But none were practical for use in the real world.

That changed in 1987, with the discovery of “high Tc” superconductors by researchers Karl Müller and Georg Bednorz. The pair discovered a compound with a Tc almost double what scientists then believed was possible.

“They didn’t believe it themselves,” said Barber. “That’s why they wrote ‘possible high Tc.'”

Müller and Bednorz received a Nobel Prize the same year–the shortest time ever between discovery and award–and touched off the American Physical Society’s “Physics Woodstock of 1987.”

This scientific grassroots confab featured some 50 presentations on the science of high-temperature superconductors. Some of the research was so new that the papers hadn’t been completed for the printed proceedings, according to Barber, who was one of about 500 participants.

High Tc superconductors became an “exploding field” overnight, and research like Barber’s has taken the state of the art up to 200 K (-99.67 F), which can by achieved by refrigerating substances with liquid nitrogen.

This discovery has led to practical applications of superconductors in magnetic resonance medical imaging and particle accelerators where superconductors create the very high currents needed to create very strong magnetic fields. In 2015 a Japanese maglev train built with superconducting electromagnets achieved a rail speed record of 375 mph.

But the tanks of liquid helium or nitrogen needed to keep superconductors at those critically frigid temperatures limit their real-world application.

So it’s no surprise that a room-temperature superconductor is the field’s Holy Grail.

Room-temperature superconductors would make it practical to use them in any electrical device to dramatically reduce energy use and eliminate components and space needed for heat dissipation.

The economics of energy-hungry processes like water desalinization would be transformed. Superconductor power lines would increase the practicality of transporting energy over very long distances–for example, sending electricity from solar farms in the Sahara desert to northern Europe.

“Power lines made of superconductors would lose no energy,” said Barber. “Cell towers would have better resolution of signals, which would allow more calls per frequency band.”

“Superconductors are old,” concluded Barber, “but we still don’t understand them.”

In other words, those Jetson-age marvels may be closer, or further away, than we know.

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