Physicists unlock nature of high-temperature superconductivity

Jul 28, 2014

Physicists have identified the "quantum glue" that underlies a promising type of superconductivity—a crucial step towards the creation of energy superhighways that conduct electricity without current loss.

The research, published online in the Proceedings of the National Academy of Sciences, is a collaboration between theoretical physicists led by Dirk Morr, professor of physics at the University of Illinois at Chicago, and experimentalists led by Seamus J.C. Davis of Cornell University and Brookhaven National Laboratory.

The earliest superconducting materials required operating temperatures near absolute zero, or −459.67 degrees Fahrenheit. Newer unconventional or "high-temperature" superconductors function at slightly elevated temperatures and seemed to work differently from the first materials. Scientists hoped this difference hinted at the possibility of superconductors that could work at room temperature and be used to create energy superhighways.

Superconductivity arises when two electrons in a material become bound together, forming what is called a Cooper pair. Groundbreaking experiments performed by Freek Massee and Milan Allan in Davis's group were analyzed using a new theoretical framework developed at UIC by Morr and graduate student John Van Dyke, who is first author on the report. Their results pointed to magnetism as the force underlying the superconductivity in an unconventional superconductor consisting of cerium, cobalt and indium, with the molecular formula CeCoIn5.

"For a long time, we were unable to develop a detailed theoretical understanding of this unconventional superconductor," said Morr, who is principal investigator on the study. Two crucial insights into the complex electronic structure of CeCoIn5 were missing, he said: the relation between the momentum and energy of electrons moving through the material, and the 'quantum glue' that binds the electrons into a Cooper pair.

Those questions were answered after the Davis group developed high-precision measurements of CeCoIn5 using a scanning tunneling spectroscopy technique called quasi-particle interference spectroscopy. Analysis of the spectra using a novel developed by Morr and Van Dyke allowed the researchers to extract the missing pieces of the puzzle.

The new insight allowed them to explore the 30-year-old hypothesis that the quantum glue of superconductivity is the magnetic force.

Magnetism is highly directional, Morr said.

"Knowing the directional dependence of the quantum glue, we were able, for the first time, to quantitatively predict the material's superconducting properties using a series of mathematical equations," he said.

"Our calculations showed that the gap possesses what's called a d-wave symmetry, implying that for certain directions the electrons were bound together very strongly, while they were not bound at all for other directions," Morr said. Directional dependence is one of the hallmarks of unconventional .

"We concluded that magnetism is the quantum glue underlying the emergence of unconventional superconductivity in CeCoIn5."

The finding has "lifted the fog of complexity" surrounding the material, Morr said, and was only made possible by "the close collaboration of theory and experiment, which is so crucial in advancing our understanding of complex systems."

"We now have an excellent starting point to explore how works in other complex material," Morr said. "With a working theory, we can now investigate how we have to tweak the system to raise the critical temperature—ideally, all the way up to room temperature."

Explore further: Superconducting secrets solved after 30 years

More information: PNAS DOI: 10.1073/pnas.1400062111

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Superconducting secrets solved after 30 years

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Steve 200mph Cruiz
4.4 / 5 (7) Jul 28, 2014
Holy crap this is big news, well done guys.
I wonder if this model of electromagnetic effects within lattices will open the door to other novel materials that aren't super conducting as well, maybe this will have some applications in meta materials or something in the future.
supamark23
4.3 / 5 (6) Jul 28, 2014
It'll be interesting to see if their findings hold for other high temp superconductors like YBCO. It'd be pretty damn cool, and insanely useful, to have superconductors that operate above 270K (assuming it's even possible).
TechnoCreed
5 / 5 (7) Jul 28, 2014
The paper is freely available on arXiv: http://arxiv.org/...5883.pdf
Arties
1.3 / 5 (15) Jul 28, 2014
Physicists unlock nature of high-temperature superconductivity
Such an interpretation is bogus. The room temperature superconductivity arises even in the systems, which have no f-orbitals and magnetic interactions at all, Cooper pairs the less (1, 2). What the physicists observed instead is rather special aspect of special type superconductivity, involving magnetic pairing inside of heavy fermions materials.
Arties
1 / 5 (15) Jul 28, 2014
It'd be pretty damn cool, and insanely useful, to have superconductors that operate above 270K (assuming it's even possible)
Of course it's possible (another examples are linked above) - but it's not researched in peer-reviewed journals, just because these materials don't play well with existing theories well. Instead of what the researchers are doing is the cherry picking of data, i.e. selectively studying the materials and systems (f-wave superconductors), which seem to support the existing theories at least a bit - as the above example indicates. Of course, such a materials aren't efficient from practical perspective, because the Cooper pairing applies only to Type-I superconductors, which work at low temperatures only. The higher temperature is, the less important the pairing and spin-spin interactions are.
Arties
1 / 5 (14) Jul 28, 2014
The CeCoIn5 is interesting material from theoretical perspective, being a superconductor composed of ferromagnetic atoms, which enables to control its superconductivity with external magnetic field in the bulk, which could enable some sensor applications. But its superconductivity transition is pretty low (2.3 K) for oxidic superconductor, which is just the result of its strong magnetic interactions of Co atoms. In this sense, the strong magnetic pairing kills the superconductivity instead and what the physicists consider as a mechanism of superconductivity is its competing effect - and quite rare in addition. We don't know about many superconductors with ferromagnetic atoms.
Arties
1 / 5 (14) Jul 28, 2014
The magnetic field effectively kills the superconductivity and the CeCoIn5 is the material, which has already it in itself - it behaves like the Type-2 i.e. HT superconductor loaded already with high current and magnetic field, so it's on the verge of superconductivity and its temperature of superconductive transition is greatly lowered in this way. It behaves like the cuprate Type I superconductor mixed with magnetic powder. Just the presence of ferromagnetic cobalt atoms and their magnetic pairing is what makes it a superconductor of I-type from oxidic superconductor, i.e. low temperature type one. In such material the low-temperature effects of superconductivity, like the Coper pairing naturally arises. Which is great for those, who do want to demonstrate this mechanism of superconductivity with respect to older theories - but it's bad for those, who just seek the practical applications of superconductors at highest possible temperatures. The magnetic pairing is bad for them.
alfie_null
5 / 5 (3) Jul 29, 2014
. . . but it's not researched in peer-reviewed journals, just because these materials don't play well with existing theories well.

Or rather, you disagree with the rest of the science world, and this is why you couldn't possibly be wrong.
Lex Talonis
1 / 5 (6) Jul 29, 2014
When I can buy super conducting fridge magnets for $2 each - then wake me so I can start the party.

Otherwise.....
swordsman
1 / 5 (2) Jul 29, 2014
More likely to be the Coulomb forces acting between unlike charges in their orbits, although the electromagnetic forces also come into play. See my paper: "Analyzing Atoms Using the SPICE Computer Program", Computing in Science and Engineering, May/June 2012.
thefurlong
3.5 / 5 (4) Jul 29, 2014
When I can buy super conducting fridge magnets for $2 each - then wake me so I can start the party.

Otherwise.....


Don't be so small minded. You aren't the one doing this crucial research. If what this article says is true, then this is a humongous step towards getting to your coveted $2 fridge magnets. We have to start some where. You want things to go faster? Then, learn enough about superconductivity and related physics fields, become a researcher, and contribute to the field yourself.
mooster75
2 / 5 (4) Jul 30, 2014
When I can buy super conducting fridge magnets for $2 each - then wake me so I can start the party.

Otherwise.....


Don't be so small minded.

You must be fun at parties...
Macksb
2.3 / 5 (3) Jul 30, 2014
Arties is right in emphasizing that the experiment involves CeCoIn5. Not a cuprate or pnictide (iron) superconductor. Quite different from them, for reasons mentioned by Arties.

The work by Prof. Morr (theory) and Davis (experiment) is important, yes. But its importance lies in establishing a good toehold in understanding one of the several new forms of superconductivity: this one, cuprate, pnictide, and mag diboride, and old BCS supers. This is a step forward in comparative theoretical analysis, informed by the powerful tools in the adept hands of Prof. Davis and his team--that would be a better theme for this article. Progress on one front; a light to shine on other fronts.

I have proposed my own unified theory of superconductivity in other Physorg posts.
swordsman
1 / 5 (1) Aug 04, 2014
The superconductivity is not only magnetic in nature, it is also a Coulomb force effect. As the temperature decreases, a point is reached where the electrical "noise" becomes near minimal and can be controlled by external Coulomb forces.
Captain Stumpy
3.7 / 5 (3) Aug 04, 2014
but it's not researched in peer-reviewed journals, just because these materials don't play well with existing theories well
@arties-zephir
OR it is pseudoscience? if it was legitimate science, it would be in a journal
Instead of what the researchers are doing is the cherry picking of data, i.e. selectively studying the materials and systems (f-wave superconductors), which seem to support the existing theories at least a bit - as the above example indicates
so basically you can't refute the science in the paper liked above so you will just call the whole thing cherrypicked? WTF? do you have (legitimate) evidence that this is cherry-picked and that refutes the paper linked? I didn't think so...
such a materials aren't efficient from practical perspective
Read Furlong's reply to Lex's TROLL post
YOU are not a part of the solution. you don't have the ability to do the research, but you can "advise" everyone here about the science?

yeah... right

prove the study wrong
El_Nose
3.7 / 5 (3) Aug 04, 2014
@Captian Stumpy

if it was legitimate science, it would be in a journal


I do not agree with that statement. 90% of what are in the leading journals are produced, authored or co-authored by a very very small group of people. It is such a small group of contributers that it can be argued that those journals in fact only promote a select sub group of people to the spot light, as a large percentage of those people also help choose what will be written in those same journals.

- My disagreement : if it is real science then a good journal will publish the paper

if it is real science and you can get someone who has been previously published in a journal to co-author your work - then it might get published in a journal.

Take the recent NASA experiment with the EmDrive. The inventor has been trying for years to get published... NASA finally said - hey we will test your device to prove it doesn't work cause you been bothering us for a decade... and then the results.. hey it works
El_Nose
3.7 / 5 (3) Aug 04, 2014
@Captian Stumpy

I am not defending arties-zephir -- just to be clear
Captain Stumpy
3 / 5 (2) Aug 04, 2014
@Captian Stumpy
I am not defending arties-zephir -- just to be clear
@El_Nose
i didn't think you were... but I also agree with what you say (as quoted below). as well as with the argument you used. Thank you for posting that. It really clarifies it.
it is pretty much what I was trying (BUT FAILED) to properly say...

It is also relevant to my post against zephir and I hope he gets it... because you are correct IMHO
if it is real science then a good journal will publish the paper
it is also correct to say that most of what zeph pushes is NOT good science.

Thank you for the clarification and I apologize to everyone else for not being more concise and properly descriptive. The gist of what I MEANT to say was as El_Nose points out:
if it is real science then a good journal will publish the paper
-El_Nose
Arties
2.3 / 5 (3) Aug 04, 2014
NASA finally said - hey we will test your device to prove it doesn't work cause you been bothering us for a decade... and then the results.. hey it works
You're fabling way too much here (in addition you're off-topic with it).
sirchick
not rated yet Aug 05, 2014

Take the recent NASA experiment with the EmDrive. The inventor has been trying for years to get published... NASA finally said - hey we will test your device to prove it doesn't work cause you been bothering us for a decade... and then the results.. hey it works


Is it me or do the British always seem to do well in science, surprised NASA didn't believe him, given their history in science is impressive.
thefurlong
5 / 5 (1) Aug 05, 2014
Take the recent NASA experiment with the EmDrive....hey it works

Actually, no, that's not what they actually said. If you look at the paper, they merely say they detected an anomalous thrust, on the order of micro Newtons (which is extremely small). That is not equivalent to claiming that it works. Here's why. NASA actually tested two drives: one designed to work (the EmDrive) and one designed not to work (the Cannae Drive), as the control. Each demonstrated a comparable amount of thrust. The fact that a drive designed not to work still showed an anomalous thrust suggests an experimental error somewhere. That does not mean that neither drive actually works, but NASA would be crazy to infer from their experiment that the EmDrive actually works.

Here is a relevant blog posting with a more thorough critique:
https://plus.goog...x2G85kr4
Arties
1 / 5 (1) Aug 05, 2014
It's not that simple. NASA did use the low power (17 watts), so they did achieve 30 microNewton thrust only. When Chinese did use 2,5 kW, they did achieve 720 mN thrust. The best ionic motors achieve 70 mN thrust under 700 W power (and lost of fuel), which is quite comparable with Chinese replication.

The NASA results are still convincing from scientific perspective, but they're lower than original Shawyer's or Chinese data by factor 50, so that they may not be usable from practical POV. IMO it's because the NASA didn't actually replicate the original EMDrive well, which is always a problem, if you don't understand the system. By AWT the anomalous thrust should manifest most significantly at 160 GHz, which is the frequency of CMBR. But NASA didn't use a magnetron, but fully harmonic artificial RF source of 200 times lower frequency. Also, the NASA did use a different geometry (Q-Drive), which is based on solely different theory and which could be suboptimal.
Arties
1 / 5 (2) Aug 05, 2014
Here is a relevant blog posting with a more thorough critique
The mainstream theorists are generally very good with their critique, when the phenomena doesn't fit their theories. They're much worse in attempts for replication of such anomalous findings, which is why the progress in physics stalls in certain areas systematically during last fifty years.

R. Feynman: "It doesn't matter how beautiful your theory is, it doesn't matter how smart you are. If it doesn't agree with experiment, it's wrong." Is it so difficult to understand it? The opinion of disappointed theorists doesn't count in physics - it's the experiment, which decides what is relevant and what is not.