For more than a century, the story about the flow of electricity through materials known as superconductors has been a saga about ice — and the pursuit of fire.
Superconductors are materials that convey electricity without the dissipation of energy. To date, scientists have been able to witness the phenomenon only under conditions in which superconducting materials are plunged to unimaginable subzero temperatures — the ice of superconductivity.
If scientists can achieve the “fire” — developing a material that superconducts at room temperature — they then would begin unlocking a world in which electrical power could flow for hundreds, possibly thousands of miles from a single source without the need for relay stations along the way.
Now, a Long Island scientist, working with an international team of collaborators, has moved a tantalizing step closer to the long-sought holy grail of room-temperature superconductivity. They have found one “twin” in a pair of electrons first predicted more than 50 years ago. The twin is part of a so-called Cooper pair and was seen for the first time with a device called a scanning tunneling microscope.
If these researchers, who are led by a Brookhaven National Laboratory scientist, are correct, they may be headed toward a breakthrough.
“With a superconductor, your computer would be 1,000 times faster,” said J.C. Séamus Davis, a senior physicist at Brookhaven and a professor of physics at Cornell University.
Room temperature is preferred because operating at subzero temperatures just for the sake of superconductivity would be an expensive and cumbersome process, experts say.
Few who study in this arcane field can resist envisioning the possibilities that may unfold if their research allows them to achieve genuine warmth.
In a world where energy is governed by superconductors, Davis said, “You could get rid of transmission lines everywhere. You wouldn’t need them.” Entire cities could be powered from small superconducting sites.
What seems a wish list of magical things is actually foreseen as possible innovations by scientists pursuing room-temperature superconductors: faster, higher, smoother, magnetically levitated trains and signal transmissions occurring at nearly the speed of light.
Although maglev trains exist now in Germany, China and Japan, all skimming along magnetic rails, the energy powering them is not derived from superconductors, but rather from conventional electrical power underlying the magnets.
Davis and his collaborators have not found the materials that can be manipulated into flying trains and smarter computers, but instead have laid eyes on electrons capable of existing in two possible states, one of which could be a room-temperature superconductor.
The Cooper pair was first theorized in 1964 by physicist Leon Cooper, who shared the 1972 Nobel Prize with two other investigators who demonstrated mathematically that Cooper pairing underlies superconductivity. Think of the pair as siblings — fraternal twins — that are very similar but not exactly alike. “One of them is what we want, a room-temperature superconductor. The other is this fairly exotic state,” Davis said, referring to what he and his colleagues actually discovered.
The electron was seen in a copper-like compound, a modified form of copper and oxide known as cuprate.
Davis and other physicists have been trying to tease superconducting secrets from cuprates for years and are well aware that they superconduct electricity at the ultrafrigid temperature of liquid nitrogen, about minus 321 degrees Fahrenheit. The trick is to warm up the cuprate without losing the superconducting capacity.
A decade ago when Davis was also researching cuprate, he found that at the atomic level, electron pairing in these compounds occurs because of magnetic interactions. So finding one twin in the pair was a major step forward, he said.
The 1964 prediction also suggested that a Cooper pair of electrons might form a “superfluid,” which means all particles are in the same quantum state, and all move as a single entity, carrying electrical current with zero resistance: in essence, a superconductor.
For years, Long Island has been home base for scientists trying to crack the confounding superconductivity puzzle. Davis has been a key contributor to the scientific literature. But some, such as Stony Brook astrophysicist James Lattimer, have looked beyond Earth for possible evidence of the phenomenon in space.
Four years ago, Lattimer found evidence of a so-called superfluid at the core of a neutron star, a discovery he nailed before a team of competing Russians were able to do so. But it was not the race itself that was important, but the confirmation that superfluids — and superconductivity — are properties of the broader, deeper universe of which Earth is a small part.
Now, having securely captured one twin, Davis said his finding not only confirms that Cooper and his colleagues were correct, but also assures the existence of the other one, the holy grail: a room-temperature superconductor.
Scientists have been chasing superconductors since 1911, when Dutch physicist Heike Kamerlingh Onnes first observed the phenomenon of superconductivity while studying the properties of mercury. Still, the inevitable question looms: How close are scientists to room-temperature superconductors?
“If you had asked me that question 20 years ago, I would have said we were very close. And if you asked me now, I would say that we are very close,” Davis said.