Superconductivity's third side unmasked

June 17, 2011, RIKEN
Figure 1: The three types of glue for superconducting electrons: lattice vibrations (top), electron spin (middle), and fluctuations between two electron orbitals (zx and yz) (bottom). The yellow spheres represent Cooper pairs of electrons. © 2011 Shik Shin

The debate over the mechanism that causes superconductivity in a class of materials called the pnictides has been settled by a research team from Japan and China. Superconductivity was discovered in the pnictides only recently, and they belong to the class of so-called 'high-temperature superconductors'. Despite their name, the temperature at which they function as superconductors is still well below room temperature. Realizing superconductivity at room temperature remains a key challenge in physics; it would revolutionize electronics since electrical devices could operate without losing energy.

Superconductivity in a material arises when two electrons bind together into so-called Cooper pairs. This pairing leads to a gap in the energy spectrum of the , which makes the electrons insensitive to the mechanisms causing . Electrons can bind into Cooper pairs in different ways, leading to different categories of superconductors.

Until the work of Takahiro Shimojima from The University of Tokyo and his colleagues, including researchers from the RIKEN SPring-8 Center in Harima, superconducting materials were classified into two broad categories. In classical superconductors, which function at very low temperatures, vibrations of atoms in the of the material provide the necessary glue for the pairing. In cuprates, the original high-temperature superconductor compounds, based on an electron’s spin generate the superconductive pairing (Fig. 1). In the pnictide , physicists assumed that the underlying mechanism was similar to that for the cuprates, but conflicting experimental results meant that the precise mechanism was controversial.

To investigate this debated pairing mechanism of pnictides, the researchers studied the properties of the material’s electronic gap. Thanks to a unique set of high-energy lasers based on very rare laser crystals available to only a few laboratories, their experiments resolved these states with unprecedented detail.

Shimojima and colleagues were surprised to discover that interactions between electron spins do not cause the electrons to form in the pnictides. Instead, the coupling is mediated by the electron clouds surrounding the atomic cores. Some of these so-called orbitals have the same energy, which causes interactions and electron fluctuations that are sufficiently strong to mediate superconductivity.

This could spur the discovery of new superconductors based on this mechanism. “Our work establishes the electron orbitals as a third kind of pairing glue for electron pairs in superconductors, next to lattice vibrations and electron spins,” explains Shimojima. “We believe that this finding is a step towards the dream of achieving room-temperature superconductivity,” he concludes.

Explore further: Iron-pnictide electron orbital pairing promises higher-temperature superconductors

More information: Shimojima, T., Sakaguchi, F., Ishizaka, K., Ishida, Y., Kiss, T., Okawa, M., Togashi, T., Chen, C.-T., Watanabe, S., Arita, M., et al. Orbital-independent superconducting gaps in iron-pnictides. Science published online 7 April 2011 (doi: 10.1126/science.1202150).

Related Stories

Superconductivity: Which one of these is not like the other?

July 13, 2009

Superconductivity appears to rely on very different mechanisms in two varieties of iron-based superconductors. The insight comes from research groups that are making bold statements about the correct description of superconductivity ...

Recommended for you

Tunable diamond string may hold key to quantum memory

May 22, 2018

A quantum internet promises completely secure communication. But using quantum bits or qubits to carry information requires a radically new piece of hardware—a quantum memory. This atomic-scale device needs to store quantum ...

Research reveals how order first appears in liquid crystals

May 22, 2018

Liquid crystals undergo a peculiar type of phase change. At a certain temperature, their cigar-shaped molecules go from a disordered jumble to a more orderly arrangement in which they all point more or less in the same direction. ...


Adjust slider to filter visible comments by rank

Display comments: newest first

1 / 5 (9) Jun 17, 2011
The solid state physics still suffers with cognitive bias of BCS theory in concept of "gluing". These electrons are repulsive, they must be compressed mutually and just this compression is, what makes the pairing and gluing of electrons in various orbitals. For example J.F.Prins revealed, above surface of semiconductor the free electrons can be compressed with electric field into superfluid even at room temperature.

In general, when some phenomena manifests with at least three different reasons, then it's already apparent, the common deeper origin of these three mechanisms is somewhere else. The causality arrow must be traced in direction from many to single explanation.

Mainstream physics is not particularly good in mutual reconciliation of its theories from psychosocial reasons: the theorists have strong egos and the more theories they maintain, the more people can keep their jobs (as R. Wilson, a former president of APS recognized before many years).
1.4 / 5 (9) Jun 17, 2011
IMO the finding of Prins is analogous to finding of cold fusion of hydrogen at nickel with S. Foccardi before twenty years. The twenty years, which we wasted in useless research, while burning the rest of fossil fuel sources.


The finding of Prins opened whole new way, how to think about superconductivity. The important is, this way is much more opened to practical applications, then the theoretical studies above. For example, we could prepare a superconductive layer of electrons just with attracting them to the well insulated wire with high external voltage. The electrons will form a compact layer above the surface of insulator, which can be even switched on and off with external voltage. We shouldn't bother with some superconductors at all - we just need a sufficiently compact insulator. J.F.Prins used the diamond layers by accident, but his finding was never attempted to reproduce in peer-reviewed press.
1 / 5 (7) Jun 17, 2011
The above model explains for example, why sodium metal never gets superconductive even at high pressure, although the surface of his atoms is full of free electrons. The BCS theory cannot explain this behavior, but the explanation is quite simple: the electrons cannot be compressed between sodium atoms, because there are no other attractive forces to bind them together.

Many other metals have additional orbitals available. These orbitals are larger and they can exert attractive forces, which held atoms together into firm cage. When some excessive electrons exists between these orbitals, they can be compressed significantly. And this is just the third mechanism, described above.

But as we can see, this mechanism is not special for some type of pnictides - but it must be present inside of ALL superconductors, or they couldn't work at all. The example of sodium illustrates, the phonon coupling and/or spin-spin interactions aren't enough - they're rather consequence of third mechanism.
1 / 5 (7) Jun 17, 2011
The compression of electrons between atoms can be the higher, the higher attractive force we will use for compression of these atoms together. This is the reason, why the metals with many various types of orbitals are better, then those with few ones (like the sodium). There is an apparent limit in number of orbitals though, which is given with electron structure of atoms. But the solution is simple: we can squeeze the redundant electrons between more atoms, which are attracted mutually. We can simply replace orbital cage with the cage formed with whole atom layers. And this is the conceptual difference between first and second group superconductors.

The semiempirical Rosser equation says, the temperature of superconductive transition will be the higher, the higher number of binding layers we use for compression of one layer with redundant electrons. The problem is, how to prepare such strongly irregular crystal, because the layers of attractive and repulsive atoms tend to alternate.
1 / 5 (7) Jun 17, 2011
There is one guy (E. Joe Eck), who is not twaddling about high Tc superconductors, but he is actually cooking them in systematic way.


He uses for example the trick, which is known from preparation of metallic glasses. These glasses are supposed to be as irregular crystals, as possible. They're prepared from mixture of many atoms, the diameter of which differs in only subtle way. Such atoms therefore cannot form a regular lattice, so they're forming an aperiodic one. His superconductors work at 18.5 °C.

But just the fact, one superconductive layer is surrounded with many nonconductive ones makes a problem, because these layers don't form a continuum phase within atom lattice. Such material is rather composed of many superconductive pieces, which have no ohmic contact mutually. So that the superconductive effect is quite inexpressive for these materials. So we should think about some better ways.
1 / 5 (5) Jun 17, 2011
Two points:

First, this is a repeat, worded somewhat differently, of an article that appeared in Phys Org on May 17.

Second, this research is consistent with a theory I have posted many times in Phys Org. All three mechanisms cited in this article--lattice vibrations in BCS, magnetic interactions (spin) and "so called orbitals that have the same energy..." involve oscillations. In the 1960s, Art Winfree proved that oscillators have a tendency to synchronize their oscillations. See Strogatz, Sync. The simplest example that Winfree specified is exactly antisynchronous pairing. Cooper pairs are exactly antisynchronous--paired by spin and by orbit. BCS pairing by lattice vibrations could occur as a result of synchronized lattice vibrations, which could mediate the pairing of electrons. That's essentially the BCS theory, but restated in Winfree's terms. Winfree's theory can be the Occam's Razor that explains all forms of superconductors. Winfree's theory not yet tried by physicists.
1 / 5 (6) Jun 18, 2011
Of course, when you're compressing electrons mutually in different orbitals, these electron will share some their properties, including phase of vibrations. At low temperature, only formation of pairs is sufficient for superconductivity. Higher temperatures need the collaboration of more electrons.

But Winfree's theory doesn't explain, why these 'synchronized lattice vibrations" occur and when. It replaces causes for consequence. From certain point of view it handles superconductivity phenomenologically in the same way, like the approaches, which are focusing on different ways of electron interactions within superconductors. But such approach doesn't solve, why these interactions occur as such.

If you don't follow the underlying cause, then you cannot prepare superconductor in targeted way, because you're still forced to guessing. In particular, the Winfree's theory doesn't provide a clue, which materials we should prepare and how such materials should appear.
4.6 / 5 (11) Jun 18, 2011
Someone is in love with the sound of their own voice.
2 / 5 (6) Jun 18, 2011
Stuff happens during free association
Why not, but you should have something to associate first (like the encyclopedic knowledge of the subject, for example). If you believe, it's so easy, just try to bring up some associations of yours - and we'll compare it...;-)

Anyway, it would be still better, than the OT babbling and spiteful resorting to personal attacks.
1.5 / 5 (4) Jun 18, 2011
I never know if my corrections alter your original thoughts
Can you demonstrate it by example, or are you're just theorizing loudly? Just an example of some sentence of mine, which would allow multiple interpretations...

I believe associations are easy.
What you believe is not relevant is matter of facts discussions.. Just show me some association(s) of yours, which wouldn't appear fringe at the very first sight - and we'll see... ;-)
1 / 5 (4) Jun 19, 2011
One last question. Why do you need this demonstration?
You didn't understand me... You told us, my posts about superconductors are ambiguous and incomprehensible, because of their poor grammar. I can admit without problem, English is not my first, neither favorite language. But just because I'm using rather basic English, I'd expect, these problems will not change the meaning of my posts significantly.

Now you're talking about deep history, when asked for some evidence of your stance...
1 / 5 (4) Jun 19, 2011
It's the same problem: if you believe, my posts are free associations instead of based on firm logics, you're welcomed to prove it first. Or you'll be ignored from my side.

(Hint: not all things, which you don't understand after first reading are free associations. You should have robust logical reasoning, how to recognize them - or we could label every new insight a "Rorschach test". I'm missing such reasoning at your case, so I've evidence, your labeling of my ideas is just a free association of yours. In another words, you're demonstrating exactly the approach, which you're criticizing at the case of other posters here.)
1 / 5 (4) Jun 19, 2011
.....for me, "these problems" "change the meaning" of your posts significantly..
The subjective opinion of yours may be completely real, but it still has nothing to do in matter of fact discussion. You should prove first, my claims and deductions are violating the logics in objective way. If you're not able to do, then you're in the role of ignorant, who is refusing relativity and/or string theory just because he cannot understand it after first reading.

So, if you don't understand something in the first five posts of mine, you're welcomed to cite the first sentence, which you didn't understand. I can try to solve your problem and explain it deeper, after then. If you will not do it, your subjective opinion will be ignored from my side next time.
1 / 5 (4) Jun 19, 2011
.. I think I can safely say that nobody understands quantum mechanics.
You see: the fact, somebody doesn't understand the theory is not evidence of its invalidity at all...;-) Confirmed by example of quantum mechanics.

Anyway, if you don't understand something from my first posts, you may feel free to ask about it. Everything else is an off-topic discussion for me from now and it has nothing to do with article subject.
not rated yet Jun 19, 2011
"In the 1960s, Art Winfree proved that oscillators have a tendency to synchronize their oscillations. See Strogatz, Sync. The simplest example that Winfree specified is exactly antisynchronous pairing. Cooper pairs are exactly antisynchronous--paired by spin and by orbit. BCS pairing by lattice vibrations could occur as a result of synchronized lattice vibrations, which could mediate the pairing of electrons."

Seems to me you are talking about frequency harmonics of the electrons, whether orbital, spin or a combination I can't tell from the info provided.
1 / 5 (1) Jun 19, 2011
SteveL: Best starting place is December 1993 Scientific American, in which Steve Strogatz and Ian Stewart describe Winfree's theory, which Winfree applied to biology. Think heart cells, Malaysian fireflies, gaits of a horse.
Winfree said all "limit cycle oscillators" (LCO) have a tendency to synchronize their oscillations, and when they do, they do so only in certain exact patterns, which Winfree described.

Quantum physics is a world of LCO--nothing else. Planck's quantum is a limit cycle; Planck's harmonic oscillations are LCOs. The perioic table is comprised exclusively of LCOs. Electrons are LCOs, and Maxwell's equations describe the behavior and implications of these LCOs. My notion is that the waves (LCOs) may mesh in Winfree patterns, which necessitates pairing by the electrons, inevitably. Lattice oscillations help coordinate--see the Millenium Bridge article by Strogatz, Abrams (Nature 2005). There, the bridge is the lattice, and the human feet are the electrons.
2 / 5 (2) Jun 20, 2011
Hush1: Consider superfluidity, as it might be explained in Winfree terms. Helium superfluidity (3 and 4) both involve coupled oscillations. The coupled oscillations seem synchronized throughout the material. They have quantized responses to rotation, in the form of vortices: The seamless fabric of synchronized oscillations may shed the energy of rotation as its best response--equivalent to the diamagnetic response in superconductivity. And the bubbles in the liquid disappear as the liquid approaches the superfluid state--perhaps because the highly interconnected oscillations knit themselves together so completely and precisely that the bubbles are squeezed out. The liquid becomes crystal clear--perhaps for the same reason. Zero viscosity (like superconductivity) may also be due to perfectly synchronized oscillations. Wave equations express as oscillations.

Conjecture in every case, to be sure. But the Winfree theory is plausible in superfluids as well as in BCS, HTS.
1 / 5 (1) Jun 20, 2011
So, Hush1, your statement that "quantum physics' world is a wave equation--and more" dovetails nicely with my effort to apply Art Winfree's theory to superconductivity and superfluidity. Wave equations in physics typically involve periodic waveforms, such as sine waves. Those are the only raw ingredients in Winfree's theory--they are limit cycle oscillations, to use Winfree's phrase. And there is more: Winfree said that the coupling interactions of LCO's vary with the frequencies and proximity of the oscillators. That's similar to phase transitions generally, which vary mainly by temperature (which affects frequencies) and pressure (which affects proximity). These similarities may be entirely superficial, of course, but there is enough to suggest that Winfree's theory of coupled oscillators could be relevant to physics. It's the only theory I know that has the potential to explain all three instances of superconductivity. Occam's Razor says that itself justifies the inquiry.

1 / 5 (3) Jun 21, 2011
Cooper pairs not needed
When you compress electrons, their condensation occurs in steps: at low temperatures the pairs are formed in accordance to BCS theory, at higher temperatures the electrons forms spin oriented cluster pairs, described with Collin Humprey's theory. Yes, their vibrations are synchronized in certain extent, so that even the Winfree's theory takes place. The common denominator is still the mutual compression of electrons with lattice, i.e. orbital-orbital interactions.

Briefly speaking, at low temperatures the classical theories of superconductivity hold truth, at higher the J.F.Prins is more correct. Schematic thinking simply has no place inside of complex multiparticle interactions. I'd rather test the J.F.Prins experiments with room temperature superconductors, rather than his theories, which are still biased in the same way, like the classical theories of superconductivity.
3 / 5 (2) Jun 21, 2011
This is the first experimental result that proves that Cooper Pairs do NOT exist: This is true for ALL SC's.
Firstly, when a current is not flowing through any superconductor, this material is a Mott-type insulator As is well-known in the literature, these insulators consist of localised orbitals. These orbitals, when their density is high enough, move by quantum fluctuations subject to Heisenberg's (NOT UNCERTAINTY) relationship for energy and time. This causes SC.
In the metals superconduction sets in immediately when the Fermi-level moves through a mobility edge which causes a metal-to-insulator transition. In the ceramics the Mott-type insulator builds up gradually and not by the movement of the Fermi-level through a mobility-edge. Therefore a pseudogap is observed which is a Mott-insulator that has too low a density of orbitals to superconduct.

phonon glue and spin-glue do not exist at all.

For updates: see
1 / 5 (2) Jun 21, 2011
Hello, prof. Prins, I'm glad you're still following these discussions. Regarding Cooper pairs in low temperature superconductors, their complete absence has no good meaning from physical perspective due the apparent existence of spin-spin interactions of electrons in many condensed systems including the helium surface. After all, their existence has been proven experimentally too in independent way, see for example here - and the experiment always goes first in physics.

Feynman: No matter how smart your theory is or how smart you are: if it doesn't agree with experiment it's wrong.
3.7 / 5 (3) Jun 21, 2011
[quote] Regarding Cooper pairs in low temperature superconductors, their complete absence has no good meaning from physical perspective due the apparent existence of spin-spin interactions etc. [/quote] Obviously if you have an array of localised fermion orbitals forming a Mott-type insulator you can have spin-spin interactions between adjacent orbitals. This does NOT prove electron pairs being glued together by spins. Furthermore Wigner already predicted in the 1930's that in non-ideal metals the loclaised orbitals will be pseudo-electrons "vibrating" through induced positive charges. This explains the isotope effect perfectly without requiring Cooper pairs. I have tried to pub;ish this for more than 7 years but has been censored consistently.
The "puppies" of Pippard, like Josephson and Archie Campbell are acting like Cardinals of the Vatican in the time of Galileo was. At present the Royal Society of London is far worse
3 / 5 (2) Jun 21, 2011
Oh yes I was wrong to sxay that this experiment was the first to prove that Cooper pairs do not exist. I have tried to publish results for the last 7 years that prove this conclusively, but was censored by our "experts" on superconduction: Especially the %!&*'s at Cambridge University.

I have some server problems and am at present using my cellphone (too expensive!!). I will thus return too this topic on Sarurday.
1 / 5 (1) Jun 21, 2011
Hush 1

Is your comment (6 posts above) meant to express your views of my idea? If so, here are my comments. Yes, I believe that one underlying principle explains all superconductivity. Namely, Art Winfree's theory of coupled oscillators. It easily incorporates BCS theory while at the same time making it broader. This is the usual progress of theoretical physics. Think Occam; or think plate tectonics. Second, I do not discard Cooper pairs. Quite the contrary: My Winfree theory shows how oscillations of electrons, once synchronized in a Winfree pattern, would inevitably form Cooper pairs--without some special, and mysterious, glue. Third, gravity is not relevant at this level, to address the issue you raise 8 posts above. But if you must know how coupled pairs would uncouple, simply read the 1993 Sci Am article I cite in one of my prior posts (11 posts above). Fourth, my theory does not have any connection to Mr. Prins, who is now, I believe, warming up just offstage.
1 / 5 (1) Jun 21, 2011
Whether or not my theory is correct, I believe that one principle will explain all of superconductivity. Nature is quite efficient--one (deep) explanation usually will suffice. Are we to expect 3 unrelated theories for superconductivity(BCS, cuprates, pnictides), and even more when other forms of superconductivity are discovered? Each theory to predict that no other superconductivity is possible, as BCS did? Sounds like the ancients, who had to invent many gods to explain the various things that perplexed them.
2.5 / 5 (2) Jun 22, 2011
Feynman: No matter how smart your theory is or how smart you are: if it doesn't agree with experiment it's wrong.

I obviously have to comment on this: Although it is correct that a theory must agree with experiment, it is also possible to have a totally incorrect theory that seems to agree with experiment. Friar Ockham already knew this 800 years ago.
many existing theories, like Feynman's QED only seems to agree with experiment because the theory has been fudged and cooked to get the answer you want. In this regard Feynman was an expert with his "renormalisation": i.e. subtracting infinity from infinity to get the experimental results you want to obtain. I believe that any physics based on Feynman diagram (like BCS), is not physics at all; and that in future this will become more and more evident that this is so.

My model does not just fit all the results that seems to be modelled b y BCS but also all the results which BCS CANNOT model. See SingleMechanism.pdf on my WEB
1 / 5 (2) Jun 22, 2011
See SingleMechanism.pdf on my WEB
You're saying there, the superconductive phase is formed with Mott-insulator, in which each orbital is polarized, so it allows superconductivity. It violates another assumption of yours, i.e. the fact, there is no apparent voltage drop on the superconductor. Such polarization would form zones of space charge, which would lead into voltage drop and the dissipation of energy in similar way, like at the case of space charge zones inside of semiconductor junction. You see: no voltage, no polarization, no conductivity mechanism for Mott insulator.
Can't download any of your .pdfs
It just works for me, see for example http://www.cathod...nism.pdf
1 / 5 (1) Jun 25, 2011
Can't download any of your .pdfs
Suggestion or work-a-round?
Done so in the past, though, without problem.

Go to my website and click on the book "The Physics Delusion"; At the bottom of that page are pdf extracts. Let me know if you cannot find them. They should download since I have just now downloaded them.
1 / 5 (1) Jun 25, 2011
You're saying there, the superconductive phase is formed with Mott-insulator, in which each orbital is polarized, so it allows superconductivity. It violates another assumption of yours, i.e. the fact, there is no apparent voltage drop on the superconductor. [/quote]
Maybe I was not stating my case clearly in this regard: Obviously, when a current flows through a superconductor, there is no electric-field and thus no polarisation. But there must also be no acceleration: Thus when applying an electric-field without injecting charge carriers, the charge-carriers within the superconductor must not accelerate, or else they cannot be superconductying charge-carriers. Therefore, under these conditions, they must polarise: And if you keep on increasing the electric-field their polarisation will become high enough so that the localised orbitals will "depin": i.e. an insulator to metal transition will occur.
1 / 5 (1) Jun 25, 2011
You see: no voltage, no polarization, no conductivity mechanism for Mott insulator.

When the orbitals in a Mott-insulator have a low density, electrical conduction above T=0 occurs by hopping which is driven by temperature fluctuations. When the density of orbitals becomes high enough, the current flows by hopping which is driven by quantum fluctuations: This means that (delta)E*(delta)t=g(hbar) allows superconduction to occur. g is determined by the shape of the orbital-wave and the flux quantum can be derived to be given by (gh)/e. Since it is measured to be h/(2e), it means that the value of g is 1/2 and the charge of the charge-carrier is e: It is a fermion. Wigner-orbitals are Gaussian orbitals and for such orbitals one expects that g=1/2. These orbitals also model the isotope effect perfectly.
Note that any "free" charge-carrier (like a Cooper pair) can be accelerated and can therefore not transport a SC-current. To generate a SC you must have an MI phase change!

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.