Surprising competition found in high-temperature superconductors

Nov 15, 2012 by Mike Ross
Surprising competition found in high-temperature superconductors
From left: SLAC staff scientist Makoto Hashimoto, Stanford graduate student Inna Vishik and SLAC Chief Scientist and Stanford Professor Zhi-Xun Shen. Credit: Brad Plummer

(Phys.org)—A team led by SLAC and Stanford scientists has made an important discovery toward understanding how a large group of complex copper oxide materials lose their electrical resistance at remarkably high temperatures.

The materials in question are high-temperature superconductors, which conduct electricity perfectly with no resistance when cooled below minus 100 degrees Celsius. 

In a report published last week in the (PNAS), researchers led by SLAC Chief Scientist and Stanford Professor Zhi-Xun Shen describe the surprisingly complex and dynamic way that the electrons organize themselves within one group of superconductors, known as cuprates. They created a complete phase diagram of the material – a roadmap of its properties – over a range of compositions and temperatures that are ideal for superconductivity.

Earlier experiments had shown that non-superconducting behavior – the so-called pseudogap phase – can occur within . In this study, the researchers were surprised to discover that this pseudogap phase actually coexists and competes with the superconducting phase over a wide range of temperatures and compositions. 

"The pseudogap is one of the biggest mysteries in high-temperature superconductivity," said Inna Vishik, a Stanford graduate student in Shen's group who is first author on the PNAS paper. "We had thought that the pseudogap did not notice the onset of superconductivity. But that is not the case. As temperature decreases, superconductivity actually suppresses the pseudogap phase."

Learning the details of this competition between the pseudogap and superconducting phases should aid researchers in their ultimate goal of creating new that operate above room temperature – an advancement that would revolutionize myriad modern technologies, from tiny computer chips to miles-long power-transmission lines.

"Twenty-five years after the discovery of in cuprates, this experiment has brought out important new aspects of the phase diagram that had been hidden," Shen said. "Since the is fundamental to understanding matter, describing the nature of the phases and the intricate relationship among them, this work is an important step forward."

The complex electronic structure of cuprate superconductors has made it very difficult for scientists to determine exactly how these materials lose their , let alone how to modify them to make this transition occur above room temperature.

In recent years, Shen's research group has helped develop a technique called angle-resolved photoemission spectroscopy (ARPES), which enables scientists to see electron interactions in much more detail than before.

To explore the properties of the pseudogap and superconducting states, Vishik systematically varied the composition of a superconducting cuprate containing bismuth, strontium and calcium and performed hundreds of ARPES measurements on those samples in Shen's Stanford lab and at SLAC's Stanford Synchrotron Radiation Lightsource.

Future research is aimed at nailing down the exact electron behavior of the pseudogap phase and the details of its competition with the superconducting phase, as well as determining exactly how electrons pair up to create superconductivity in the copper oxides.

Explore further: Finding the 'heart' of an obstacle to superconductivity

More information: www.pnas.org/content/109/45/18332.full.pdf+html

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johanfprins
1.7 / 5 (6) Nov 15, 2012
The pseudogap consists of the SAME charge-carriers which are responsible for superconduction: The only difference is that the distances between these self-same charge-carriers are larger when they form the so-called "pseudogap" state.

Of COURSE there will be "competition" between the "pseudogap" phase and the SC-phase, since in areas where the distances are smaller than the critical distance, superconduction is possible, while in those regions where the distances are larger, SC cannot occur: But the fools who believe in BCS assume that there is a pseudogap. It has NOTHING to do with a pseudogap at all.

A Mott-phase is the precurser to superconduction which starts when the distances between the Mott-orbitals become small enough so that they can move coherently by means of resonance: NOT BY FORMING A BOSE-EINSTEIN CONDENSATE! If they could have formed a BEC, they would not be separate distinguishable entities which can act as charge-carriers.
chromosome2
3.7 / 5 (3) Nov 15, 2012
Every step towards superconductivity above 0 C thrills me completely :D And really... even if we never hit 0 C, every step is still huge progress, since the cost of cooling something decreases a lot as the thermal differential lessens.
ValeriaT
1 / 5 (4) Nov 15, 2012
This finding is nothing new for me, I explained it before four years already. Technically, you can have a superconductor full of pseudogap phase - but when its islands will not be connected together, it will still remain effectively an insulator. We already have a superconductors having pseudogap stable well above room temperature (despite the physicists are ignoring obstinately every finding, which isn't supported with mainstream lobby and which can reveal, that the actual progress is possible without billions of dollars spent into grants and salaries without apparent progress). The actual trick is, how to create the continuous superconductive phase across whole bulk of material and no theory of superconductivity will help you with it.
ValeriaT
1 / 5 (3) Nov 15, 2012
Before some time I proposed a trick, which is used in Damascus steel production. It consists of repeated molding and elongating of ceramic precursor mixed with dopant atoms. Joe Eck is using another trick, which is similar to production of metallic glasses: it bakes a mixtures of many metal oxides, which have slightly different atom radius. Such a mixture tends to form sparse crystals or possibly quasicrystals with heterolattice of low periodicity (large doping distance). But just such materials crystallize quite poorly. If this method will not work, then we would be forced to use a atom beam lithography, which places the atoms layer by layer into heterostructures. Such an materials will probably work well as a HT superconductors, but they will be very expensive, because this method is very slow.
ValeriaT
1 / 5 (4) Nov 15, 2012
We shouldn't forget the finding of J.F.Prins, who has found, that the surface of doped diamond becomes superconductive in vacuum even at room temperature. As usually for each such a fundamental finding, his experiments were never attempted to replicate in peer-reviewed press (if at all). The principle of his finding is, the electrons are strongly attracted to oxygen holes implanted beneath surface of diamond layer like the hens to the feeder. The dense phase of electrons is supposed to be superconductive and if we apply a voltage across it, it's superconductivity can be switched on and off. This method opens a way for creation of artificial superconductors, which are switchable with external electric field in similar way like FET transistors, but without ohmic resistance in switched state. Such a transistor would behave like ideal switching element with infinite gain. If the physicists would study J.F.Prins's finding consequentially, we could have such a prototypes already.
johanfprins
1.8 / 5 (5) Nov 16, 2012
Every step towards superconductivity above 0 C thrills me completely :D And really... even if we never hit 0 C, every step is still huge progress, since the cost of cooling something decreases a lot as the thermal differential lessens.


I have already hit 600 K in the year 2000! But since this proves that the BCS model based on Cooper Pairs is wrong, nobody wants to pursue it further, and I can get no funding to pursue it further on my own. I am, however, slowly using my own money when I have some left, to build a prototype SMES (Superconducting Magnetic Energy storage) battery; which will work at room and higher temperatures. So far the results are good.But with the lack of funding and assistance, it will take a longer time than is necessary.
johanfprins
1.8 / 5 (5) Nov 16, 2012
@ ValeriaT,

What I cannot understand is that you can post common sense when it comes to superconduction (even though you still do not completely understand the real mechanism that is responsible), but can lose all common sense when it comes to "wave-particle" duality.

"Wave-particle duality", "complementarity", "Cooper Pairs", the mainstream explanation for the "Aharonov-Bohm effect". the mainstream model for "Josephson-tunnelling", the "Higgs-boson", "Anyons", etc. etc. etc.' are all based on the same WRONG assumption; and are therefore all hallucinations.
johanfprins
1.8 / 5 (5) Nov 16, 2012
@johanprins: Recently the wave particle duality for photon was proven experimentally.
Nope! This experiment only proves that a photon-wave has a centre-of-mass, as it MUST have since its EM energy is distributed dynamic mass.

Believe it or not, even the physicists who believe in particle-wave duality cannot be easily convinced, that these two aspects can manifest at the same moment or even alternate during single experiment. They believed, that the photon can form particle or wave in separated experiments only.
Obviously they will reason such since this is what the position MUST be according to the postulates "wave-particle duality" and "complementarity"; just as you believe must be the case, but are too stupid to understand.

johanfprins
2.3 / 5 (6) Nov 16, 2012
But in 2004 Afshar proved, that the photon can be observed both in particle, both in wave state at the same moment and now it was confirmed,
Afshar proved NOTHING of the sort. He proved that the photon moves through BOTH slits simultaneously and thus form a diffraction pattern which he measured by wires on the lens without collapsing the diffracted intensity. He then found that this wave, when subsequently reaching two detectors after having moved through the lees, has a 50/50 probability to be recorded by the detector with which it first resonates. NO "particle" involved whatsoever!
johanfprins
1.8 / 5 (5) Nov 16, 2012
I can assure you, I do understand the superconductor mechanism well.
No you do not! You still believe that pair-formation is necessary for SC to occur!
So if you feel, you're thinking about it differently, you should check your opinion again.
It is not "my opinion", since my model is verified by the fact that sofar it explains (by URVE-FITTING) every suoperconducting material; from the low-temp metals, to the ceramics, to the semiconductors like p-type diamond etc.
The physicists who are extrapolating one or few experiments can get biased easily,
Exactly just what you are doing! And if in addition, you argue in terms of a duck on a pond and water vapour drifting past, you are completely insane!
but I'm not doing a mistakes in conceptual things, because I do maintain an extensive databasis of experiments and I don't accept some idea, until it fits them all.
Show me curves generated by your model which fit the data for YBCO and p-type diamond!
johanfprins
2.3 / 5 (6) Nov 16, 2012
@johanprins:
One of Afshar's assertions is that, in his experiment, it is possible to check for interference fringes of a photon stream (a measurement of the wave nature of the photons) while at the same time observing each photon's path
Wikipedia quoted
Wrong assertion, since he is NOT "observing each photons's path". He is only observing where each photon ends up after it collapses. How does he know from this how the photon reached the detctor? Is it totally impossible for you to think logically?
It has no meaning to continue with discussion about it, because you're apparent ignorant troll,
In your case it is not just "apparent". You ARE a troll AND a very stupid one at that.
johanfprins
2.3 / 5 (6) Nov 16, 2012
I'm not doing a mistakes in conceptual things, because I do maintain an extensive databasis of experiments and I don't accept some idea, until it fits them all.
Here is your chance to prove that you are not lying:
Fit your model to the following YBCO data

Segawa and Ando, Phys. Rev. Lett.86 (2001) 4907

and diamond data in:

Klein et al. Phys. Rev. B 75 (2007) 165323-1

I want REAL quantitative equations: Not ducks swimming on a pond: Or two persons pulling one another across a hump by their bootstraps!
johanfprins
1.8 / 5 (5) Nov 16, 2012
From perspective of quantitative equations even the epicycle system of Ptolemy worked well.
A person who thinks that a duck swimming on a pond models physics quantitatvely will reason like this. I can now understand why the crackpots in charge of mainstream physics can claim that those with other insights are crackpots. YOU make it easy for them!

Do you see? You're fighting against mainstream science - but you're using the same methods,
I am not: I think that YOU are!
like its proponents whenever possible: personal invectives, ignorance of logical arguments,
I am still waiting to see a single logical argument from your side.
censorship
If you were in the position to censor you would have been the censor of censors!
and "proof" based on coincidence with formal models.
Coincidence? What do you mean? You are not even able to write down a SINGLE quantitative equation. You are so outrageously arrogant that you cannot even see your own stupidity.
johanfprins
1.8 / 5 (5) Nov 16, 2012
In addition, you're just confused heavily: for example, http://i46.tinypi...kbbd.gif
This is why you are such a dangerous loose cannon. You do not first do your homework
before you shoot your mouth off. If you did you would have studied http://www.cathod...nism.pdf

YES, the SC phase that I have discovered by extracting electrons with an anode from n-type diamond IS a condensate, but NOT a Bose-Einstein condensate. It forms INDEPENDENTLY of what the temperature is; just as a light wave forms within a laser cavity owing to resonance with the size of the cavity.

This DOES NOT happen WITHIN a superconducting material, since the charge-carriers are spaced too far apart to form a simular condensate. And they form an impurity band LONG before they can reach this density.

FrankHerbert
2 / 5 (4) Nov 16, 2012
Dr. Prins, have you ever developed a demonstration of your superconducting technology? Something like a self sustaining room-temperature meissner effect demonstrator?

I'm just a layman, please don't tear me apart.
johanfprins
1.8 / 5 (5) Nov 16, 2012
have you ever developed a demonstration of your superconducting technology?
yes I have
room-temperature meissner effect demonstrator?


Not I, but someone else has: He does not want to publish since he is too scared of the mainstream! BUT, That there is NOT an electric field, follows logically and directly from the physics that is used every day to design and manufacture solid state electronic devices. In fact, in my case, you do not need any other measurements to prove that a current is flowing while there is no electric-field present: It is the best proof ever since 1911, that a current can flow without an electric field being present.
ValeriaT
1 / 5 (2) Nov 16, 2012
Current cannot flow without electric field induced with magnetic field. That is to say, neither current in superconductor can arise spontaneously. BTW You're not required to present your name for being able to publish video at YouTube, for example.
daywalk3r
3 / 5 (8) Nov 17, 2012
Current cannot flow without electric field induced with magnetic field.
Word salad.

Although it is correct that a potential difference is usually required for current to flow, this potential difference does NOT occur within/along the conduction path of a SC itself.

Zero resistance -> zero voltage drop -> zero potential difference -> no "electric field" -> Meissner effect -> etc..

On another note, Cooper pair formation is most probably a consequence rather than the cause, so I would better not put much money on BCS becomming the long sought Holy Grail after all..
johanfprins
1.8 / 5 (5) Nov 17, 2012
Current cannot flow without electric field induced with magnetic field.

This is the BS that the London brothers concluded because they were too stupid to understand Ohm's law.
That is to say, neither current in superconductor can arise spontaneously.
Oh it can when an applied magnetic field becomes high enough to destroy the SC phase. The SC phase can then remain within type II superconductors by the formation of circular currents. This does not happen within a type I superconductor:

However, when forming a ring out of both types of superconductors, a current starts when the magnetic-field reaches a critical value. Before it reaches this value, no current is flowing even when the magnetic field induces an electric-field around the ring. Thus the onset of the current has NOTHING to do with such an induced electric-field. The SC charge-carriers do not even see an electric-field and do not respond to such a field at all.
johanfprins
1.8 / 5 (5) Nov 17, 2012
On another note, Cooper pair formation is most probably a consequence rather than the cause, so I would better not put much money on BCS becomming the long sought Holy Grail after all..
Although electron pairs can form, this is NOT possible via the Cooper mechanism.

The latter is based on quantum field theory which is deeply flawed since it is based on Dirac's SINGLE ELECTRON equation which is a fudged equation:

Firstly Dirac replaced a square root with matrices, and, secondly, he then found a physically impossible solution for such a single electron: The electron MUST have an energy of minus infinity.

Dirac then fudged further by declaring that there is an infinite sea of electrons: If the latter is possible he should have derived a "multi-electron" wave equation.

Furthermore, as I have posted on this discussion forum, if Dirac did not fudge he would have found Maxwell's wave equation for which the EM energy of the single electron is moving with a speed v less than c.
visual
not rated yet Nov 19, 2012
I don't know what you all are talking about but she is hot.
Minich
2 / 5 (4) Nov 23, 2012
<<< Earlier experiments had shown that non-superconducting behavior – the so-called pseudogap phase – can occur within cuprate superconductors. In this study, the researchers were surprised to discover that this pseudogap phase actually coexists and competes with the superconducting phase over a wide range of temperatures and compositions. >>>

It is not NEW! See, for example, exellent rewiew by Uchida:
http://frolih.narod.ru/

<<<<"The pseudogap is one of the biggest mysteries in high-temperature superconductivity," said Inna Vishik >>>>

No!!! The pseudogap is one of the most simple features in band theory of semimetals!!!

<<<< As temperature decreases, superconductivity actually suppresses the pseudogap phase.>>>>

No!!! Pseudogap, as a rule, promotes superconductivity in underdoped insulators!!!
johanfprins
1 / 5 (3) Nov 24, 2012
<<<< As temperature decreases, superconductivity actually suppresses the pseudogap phase.>>>> No!!! Pseudogap, as a rule, promotes superconductivity in underdoped insulators!!!


Both statements are correct.

The so-called pseudogap phase IS the SAME as the superconducting phase except that the density of charge-carriers is too low to allow SC to occur through the whole material.

As the doping level increases the density of charge-carriers increases. Thus, in this respect, the "pseudogap" "promotes" SC in underdoped insulators.

As the temperature decreases the density of charge-carriers increases: More and more regions become superconducting so that the onset of superconductivity does "actually suppress the pseudogap phase.