Warming up the world of superconductors

February 25, 2015, University of Southern California

A superconductor that works at room temperature was long thought impossible, but scientists at USC may have discovered a family of materials that could make it reality.

A team led by Vitaly Kresin, professor of physics at USC, found that aluminum "superatoms"—homogenous clusters of atoms—appear to form Cooper pairs of (one of the key elements of ) at temperatures around 100 Kelvin.

Though 100 Kelvin is still pretty chilly—that's about -280 degrees Fahrenheit—this is an enormous increase compared to bulk aluminum metal, which turns superconductive only near 1 Kelvin (-457 degrees Fahrenheit).

"This may be the discovery of a new family of superconductors, and raises the possibility that other types of superatoms will be capable of superconductivity at even warmer temperatures," said Kresin, corresponding author of a paper on the finding that was published by Nano Letters on Jan. 28. USC graduate student Avik Halder and former USC postdoctoral researcher Anthony Liang are co-authors.

The future of electronics and energy transmission

Superconductivity is the ability to transmit electricity without any resistance, meaning that no energy is lost in the transmission.

The reason your laptop heats up when you leave it on for a long time is that electricity meets resistance as it courses through the machine's circuits, generating heat—wasted energy.

Beyond the specific applications that superconductors are already used for—MRI machines, powerful electromagnets that levitate maglev trains, particle accelerators and ultrasensitive magnetic field sensors, to name a few—a room-temperature superconductor would allow engineers to make all electronic devices ultraefficient.

Cooper pairs: electron dance partners

First predicted in 1956 by Leon Cooper, Cooper pairs are two electrons that attract one another in some materials under certain conditions, such as extreme low temperatures.

"Imagine you have a ballroom full of paired-up dancers, only the partners are scattered randomly throughout the room. Your partner might be over by the punch bowl, while you're in the center of the dance floor. But your motions are done in tandem—you are in step with one another," Kresin said. "Now imagine everyone changes dance partners every few moments. This is a commonly used analogy for how Cooper pairing works."

When electrons flow through a material, they bump into various imperfections that knock them off course. That's the resistance that causes energy loss in the form of heat.

If the electrons are mated up into Cooper pairs, however, that connection is just strong enough to keep them on course regardless of what they bump into. Cooper pairs are what make superconductivity work.

Superconductivity in superatoms

Superatoms actually behave in some ways like a giant atom. Electrons flow inside them in a predictable shell structure, as if in a single atom's electron cloud.

Electron shells are the result of a quantum effect—a physical property described by the special laws of quantum mechanics. The shells are the orbits of increasing size at which electrons can be found around an atom. They occur in a predictable fashion: Two electrons zip around the nucleus in the closest orbit, eight in the next highest orbit, 18 in the third and so on.

The fact that superatoms are not just solid particles but also possess a giant set of electron shells made scientists suspect that they might also exhibit another quantum effect: Cooper pairing.

To test that hypothesis, Kresin and his team painstakingly built aluminum superatoms of specific sizes (from 32 to 95 atoms large) and then zapped them with a laser at various temperatures. They recorded how many electrons they were able to knock off of the superatom as they dialed up the energy level of the laser.

The subsequent plot on a graph should have been a simple upward curve—as the energy of the laser increases, more electrons should be knocked off in a smoothly proportional manner.

For superatoms containing 37, 44, 66 and 68 aluminum atoms, the graph instead showed odd bulges indicating that at certain energy levels, the electrons were resisting the laser's effort to knock them away from the group—possibly because Cooper pairing was helping the electrons to cling to each other.

The bulge appears as temperature decreases—with the threshold for its appearance occurring somewhere around 100 Kelvin, giving evidence that the electrons were forming Cooper pairs.

The future of superconductors

Superatoms that form Cooper pairs represent an entirely new frontier in the field of superconductivity. Scientists can explore the superconductivity of various sizes of superatoms and various elements to make them.

"One-hundred Kelvin might not be the upper-temperature barrier," Kresin said. "It might just be the beginning."

Kresin envisions a future in which electronic circuits could be built by placing superatoms in a chain along a substrate material, allowing electricity to flow unhindered along the chain.

Explore further: Electron spin could be the key to high-temperature superconductivity

More information: Nano Lett., 2015, 15 (2), pp 1410–1413. DOI: 10.1021/nl5048175

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1 / 5 (6) Feb 25, 2015
Ultraconductors, polymer equivalents of room temperature superconductors are well proven.

The development of tape and wire from these remarkable polymer materials is now on the horizon. See ULTRACONDUCTORS at aesopinstitute.org

Tape is perhaps a year in the future. Wire might be achieved in two years. Either would provide the needed material to open huge new markets.

Energy storage rings perhaps 8 feet in diameter were patented some time ago by Los Alamos National Laboratory. They would be reinforced with Kevlar or a similar material.

Such rings could be stacked by utilities for energy storage.

Thin films of this materials may open a path to tiny generators, initially able to replace batteries in hearing aids. They may prove scalable.

Four SBIR contracts were completed some years ago. The Final Reports are available upon request. A Phase I & Phase II were with the USAF. The others were with Ballistic Missile Defense.

1 / 5 (6) Feb 25, 2015
Cooper pairs are what make superconductivity work
It can be hardly true for high Tc materials, like the ultraconductors. An independent researcher Joe Eck announced material, exhibiting Meissner effect at 120 °C
3 / 5 (1) Feb 26, 2015
How are civilized people supposed to read these articles, when they aren't in metric. Why can't the USA get with the 21st century already.
Keyto Clearskies
4.8 / 5 (4) Feb 26, 2015
Learn the truth about Mark Goldes' "Ultraconductor" fraud:


(The linked article contains links to the four SBIR reports written by Goldes' fraudulent company MPI - so you can judge for yourself whether the grant projects were "successful" in any way other than in tranferring tax revenue from the USAF to Mark Goldes' company.)
Keyto Clearskies
5 / 5 (3) Feb 26, 2015
For five years at Chava Energy LLC, Goldes carried on the very same false pretense he now continues at AESOP Institute: that "Ultraconductor" development "is resuming." After Goldes was ejected from Chava Energy in July 2014, all mention of the "Ultraconductor" pretense was suddenly removed from the Chava Energy website. It was nothing but a pretense, since no work at all on "Ultraconductors" was ever done at Chava Energy. Ultraconductor "development" never resumed at Chava Energy during the five years Goldes pretended otherwise, and "Ultraconductor" development will not be resuming at his so-called AESOP Institute, either. It is only a fraudulent pretense and nothing more.

Learn the truth about Mark Goldes' "Ultraconductor" fraud:

1 / 5 (5) Feb 26, 2015
The Troll who posts "pathological criticism" lies and distorts in every comment he makes about me or Ultraconductors. The SBIR Final Reports refute his comments as do numerous refereed papers listed under ULTRACONDUCTORS at aesopinstitute.org

It is true that the work was suspended following the dot.com crash. Funding was not available for a decade. The work has resumed. If the newly invented tiny generator mentioned above proves practical it will be clear to anyone interested that polymer equivalents to room temperature superconductors are real. Ultraconductors a micron or two in diameter can carry 50 amperes and are useful to 200 degrees C. Once in the market these materials will speak for themselves.
1 / 5 (2) Feb 26, 2015
If you grow a one-atom thick honeycomb graphene lattice on a substrate, you have a potential superconductor and a potential 10,000 faster transistor, to name a few applications. The challenge right now is being able to mass produce "usable" one-atom thick graphene layers.

Also, to this day, science does not know the source of the "Strong Nuclear Force" in atoms.
5 / 5 (1) Feb 26, 2015
>Also, to this day, science does not know the source of the "Strong Nuclear Force" in atoms.

wth are you on about, mate? This was resolved like... half a century ago. To roughly the same degree as we know the source of the electromagnetic force. There's a field that coordinates the momenta of several particles that are charged with respect to that field.
1 / 5 (2) Feb 26, 2015
Say what now? Who is this?!

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