Physicists explain why superconductors fail to produce super currents

Jun 27, 2010

When high-temperature superconductors were first announced in the late 1980s, it was thought that they would lead to ultra-efficient magnetic trains and other paradigm-shifting technologies.

That didn't happen. Now, a University of Florida scientist is among a team of physicists to help explain why.

In a paper set to appear Sunday in the online edition of , Peter Hirschfeld, a UF professor of physics, and five other researchers for the first time describe precisely how the atomic-level structural elements of high-temperature ceramic serve to impede electrical current. Their explanation for how "" separating rows of atoms within superconductors impede current is the first to fit a phenomenon that has helped keep the superconductors from reaching their vaunted potential - and puzzled experimental physicists for more than two decades.

"Nobody understood why it was such a strong effect, or why the current was so limited by these grain boundaries," Hirschfeld said. "And that is what we have explained in this paper."

High-temperature superconducting ceramic wires are composed of rows of atoms arranged slightly askew to each other, as though one piece of graph paper had been melded atop another with the horizontal and vertical lines at less-than-perfect alignment. Lumps of build up at the angles where the lines meet, acting like dams to interrupt the flow of electricity.

Hirschfeld and his colleagues' contribution was to conceive and construct a that fit these observations "very nicely," he said. "We abstracted a very theoretical model of a single boundary" that can be applied to all such boundaries, he said.

Unfortunately the model does not suggest a way to break down the barriers, although Hirschfeld said it will give researchers a better tool to interpret results of past and future experiments. This gives the team hope that their model could, over time, lead to high-temperature superconductors with less restrictive grain boundaries. That would be a step toward helping the superconductors, which have found limited applications in areas such as powerful research magnets, reach their heralded potential.

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

Related Stories

Stripes offer clues to superconductivity

May 17, 2010

New images of iron-based superconductors are providing telltale clues to the origin of superconductivity in a class of ceramic materials known as pnictides. The images reveal that electrons responsible for ...

Secrets behind high temperature superconductors revealed

Feb 22, 2009

(PhysOrg.com) -- Scientists from Queen Mary, University of London and the University of Fribourg (Switzerland) have found evidence that magnetism is involved in the mechanism behind high temperature superconductivity.

Superconductors on the nanoscale

Mar 15, 2010

Superconductors, materials in which current flows without resistance, have tantalizing applications. But even the highest-temperature superconductors require extreme cooling before the effect kicks in, so researchers want ...

Strain Has Major Effect on High-Temp Superconductors

Feb 15, 2007

Just a little mechanical strain can cause a large drop in the maximum current carried by high-temperature superconductors, according to novel measurements carried out by the National Institute of Standards ...

Race for better superconductors heats up

Oct 20, 2008

Scientists have discovered a new family of superconductors -- materials that carry electricity more efficiently than copper and other metals -- whose properties rekindle enthusiasm about the possibility that these exotic ...

Recommended for you

Nike krypton laser achieves spot in Guinness World Records

1 hour ago

A set of experiments conducted on the Nike krypton fluoride (KrF) laser at the U.S. Naval Research Laboratory (NRL) nearly five years ago has, at long last, earned the coveted Guinness World Records title for achieving "Highest ...

Unleashing the power of quantum dot triplets

5 hours ago

Quantum computers have yet to materialise. Yet, scientists are making progress in devising suitable means of making such computers faster. One such approach relies on quantum dots—a kind of artificial atom, ...

Chemist develops X-ray vision for quality assurance

5 hours ago

It is seldom sufficient to read the declaration of contents if you need to know precisely what substances a product contains. In fact, to do this you need to be a highly skilled chemist or to have genuine ...

The future of ultrashort laser pulses

6 hours ago

Rapid advances in techniques for the creation of ultra-short laser pulses promise to boost our knowledge of electron motions to an unprecedented level.

IHEP in China has ambitions for Higgs factory

23 hours ago

Who will lay claim to having the world's largest particle smasher?. Could China become the collider capital of the world? Questions tease answers, following a news story in Nature on Tuesday. Proposals for ...

User comments : 19

Adjust slider to filter visible comments by rank

Display comments: newest first

fmfbrestel
2.6 / 5 (7) Jun 27, 2010
Great example of articles on this site ignoring any potential pitfalls or down sides to the break-through being touted -- I didnt even know there were major current restrictions on these materials. That drawback was only news worthy AFTER someone had come up with an explanation for it.
I like this site for its broad range of topics. However the editors here need to start doing more then just rubber-stamping "Approved" on every single submission they receive.
Jigga
2.3 / 5 (6) Jun 27, 2010
Practical limit of superconductor current is given by the fact, every moving charged object generates magnetic field. The cluster of co-moving electrons is behaving like bunch of magnets, which are oriented concurrently. Such magnets will always repel mutually. Because superconductivity is dependent on existence of Cooper electron pairs (in low temperature superconductors) or densely packed electron clusters (at the case of these "high" Tc ones), the magnetic field produced by superconductor current ALWAYS destroys superconductivity by itself.

This is the true reason of current limit at LHC supermagnets, where the grain boundaries plays no role at all. This mechanism is known from very beginning of superconductor research and it doesn't depend on superconductor structure very much - in this sense the above article is misleading for laymans.
johanfprins
2.6 / 5 (5) Jun 27, 2010
A superconductor IS an insulator which consists of an array of localised orbitals. These orbitals are formed by donor electrons which come from a higher energy state. In order to increase a current a larger electric-field is required. This field increases the energy of the orbitals by polarisation; and since the energy-difference between the donor-electrons and the orbitals thus decreases, the density of orbitals decreases for non-zero temperatures.

When this density becomes too low to allow coherent movement by quantum fluctuations, superconduction STOPS. This is the primary reason why a superconductor has a maximum current. Obviously grain boundaries etc. will play a role, but these effects are secondary compared to the primary effect which is also present within a "perfect" superconsuctor.
sender
1 / 5 (1) Jun 27, 2010
possibly this would mean photoexcitation by bosons would allow for potential holes to harness the superconductor grain boundaries almost like a corkscrew
sean_c_ohman
1 / 5 (3) Jun 27, 2010
Can we use modern teleportation technology to build better semi-conductors? I mean their entire field of research is on aligning atoms right? perhaps they could use the money to further their research... :-p
johanfprins
3 / 5 (6) Jun 28, 2010
Can we use modern teleportation technology to build better semi-conductors? I mean their entire field of research is on aligning atoms right?

Yes we can. In fact it is possible to generate a single macro-wave consisting only of electrons (A macro "chemical bond") across which another electron can be teleported. Obviously this phase is a special type of superconductor. I have demonstrated this already 10 years ago, but the bozos in charge of superconductor reseach wants to believe in non-existent Cooper pairs and have been ridiculing and suppressing this incontrovertible evidence.
SteveL
1 / 5 (3) Jun 28, 2010
You know; if no "solutions" are found then the research funding continues to flow. It would be like a drug company selling a cure - it puts them out of business eventually. If science figures out how to mass produce high temp superconductors, how many researchers are put out of work?
hbar_squared
5 / 5 (5) Jun 28, 2010
You know; if no "solutions" are found then the research funding continues to flow. It would be like a drug company selling a cure - it puts them out of business eventually. If science figures out how to mass produce high temp superconductors, how many researchers are put out of work?

Exactly none. High-temperature currently means above -170C or so (maybe even lower). There is so much room for improvement. If there is a breakthrough, then it frees the scientists to work on room-temperature superconductivity, or ductile superconductors, or any of the millions of available research paths that are currently unexplored.

I'm sorry, but there really is no "Big Science" hoarding your tax dollars. Peer review is like capitalism - it gives incentives to the first to solve a problem, and creates competition among peers. First one to solve current limiting will get massive financial rewards, huge amounts of professional respect, and lifelong tenure. And a Nobel prize.
DaveGee
5 / 5 (4) Jun 28, 2010
Believe what you will, but I've known A LOT of research scientists over the years (some Nobel Laureates) and they are NOT big on the idea of covering up something they themselves discovered.

Research is all about learning/discovering something that nobody else on the entire planet knew before! And that my friend is something you'd NEVER keep secret not for a million dollars or all the tea in China.

It's perhaps the biggest driving force for any real researcher or anyone involved in the sciences.
johanfprins
2.5 / 5 (8) Jun 28, 2010
Peer review is like capitalism - it gives incentives to the first to solve a problem, and creates competition among peers. First one to solve current limiting will get massive financial rewards, huge amounts of professional respect, and lifelong tenure. And a Nobel prize.

I can prove to you incontrovertibly that what you wrote here is a blatant LIE of garguantan proportions. Our present peer review system is geared to protect accepted dogma NOT to promote new paradigms.

I have solved the current limiting on higher critical temperatures for superconductors more than 7 years ago. Where is my "massive financial rewards" and my Nobel Prize. It is amazing how physicists are holding back progress by believing exactly the poppycock you have just posted.
Jigga
2 / 5 (7) Jun 28, 2010
..Our present peer review system is geared to protect accepted dogma NOT to promote new paradigms. ..
"Just suppose, even though it is probably a logical impossibility, that some smart aleck came up with a simple self-evident, closed theory of everything. I---and so many others---have had a perfectly wonderful life pursuing the will-o'-the-wisp of unification. I have dreamed of my children, their children and their children's children all having this same beautiful experience.

All that would end.

APS membership would drop precipitously. Fellow members, could we afford this catastrophe? We must prepare a crisis-management plan for this eventuality, however remote. First we must voice a hearty denial. Then we should ostracize the culprit and hold up for years any publication by the use of our well-practiced referees. Just to be safe, we should put the paper on our Index---I mean in our index--- where it can be lost for centuries..."

A quote of the president of APS mafia...
Jigga
1 / 5 (4) Jun 28, 2010
This memo was presented by Prof. Dr. Robert Wilson in 1986 in the July issue of Physics Today, 39, 26.

But he didn't realize the possibility of Internet existence.
johanfprins
2.6 / 5 (5) Jun 28, 2010
This memo was presented by Prof. Dr. Robert Wilson in 1986 in the July issue of Physics Today, 39, 26.

But he didn't realize the possibility of Internet existence.

Amazing. But it fits what is happening. It is, however, still an open question whether the internet will break this sick mentality which is controlling most, if not all, institutions on our planet: Not just physics.
Jigga
1.8 / 5 (5) Jun 28, 2010
..It is, however, still an open question whether the internet will break this sick mentality which is controlling most, if not all, institutions on our planet..
I'm sure it will, but don't forget, it's just you, who is fighting against all opponents in the same way, like proponents of mainstream.

For effective fight against mainstream you should always remain more clear, logical & consistent and opened to critique, then the mainstream, you're attempting to criticize.

Or you will just add the arguments to the opponent's camp. I'm not always sure, whether you're realizing it in full depth.
johanfprins
2 / 5 (4) Jun 29, 2010
For effective fight against mainstream you should always remain more clear, logical & consistent and opened to critique, then the mainstream, you're attempting to criticize.

Quite funny! I am of the opinion that this advice applies more to you than to me.

I am NOT fighting opponents: Only stating physics as I have found it to be experimentally. If there is any opposition it is against me from the mainstream: They do not tolerate any viewpoint which contradicts what they WANT to believe: Just like you are doing. You should note that I have kept on asking questions from the mainstream (and from you), which they and you just refuse to answer: For example, to define what is meant by a "particle" to justify the concept of "wave-particle" duality. So far no intelligent answer!

There is no duality since waves can morph into different shapes and sizes. To conclude that a wave of small size is a particle, while not even defining what is meant by a "particle" is insane physics.
johanfprins
2.3 / 5 (3) Jun 29, 2010
...into shapes of particles...

When the boundary conditions change, a wave can "collapse" to occupy a smaller region in space. To interpret this smaller wave as a "particle" is stupid. It is still a field!
From technical POV, waves cannot have a "shape". Wave is simply a solution of wave equation, i.e. an infinite sinusoide without beginning or end.

Show me where such a wave can physically manifest in our universe. I am not an airy-fairy mathematician like Dirac. A physical wave ALWAYS EXIST subject to boundary conditions: If you solve a wave equation by ignoring the physical boundary conditions, you are doing voodoo.
general relativity has a problem with wave concept from its very beginning - no gravitational waves were observed yet.

Intensity of matter wave = mass: "tunnelling tail" = curvature of space. Since a matter wave can morph instantaneously it is doubtfull that g-waves will be observed. Einstein did not allow for instantaneous interactions
johanfprins
2.6 / 5 (5) Jun 30, 2010
... they can imagine, no wave can apparently exist without underlying particle environment like the ripples at the water surface cannot exist without underwater composed of molecules -

This proves that you do not have a the faintest clue what the debate in quantum mechanics about wave-particle duality is all about. This also proves that you are Jigga, Seneca, Alexa, Aliseev, and whatever. Where do you really live? And please start to learn some basic physics! Since most chairmen of physics departments do not even understand first year physics, I suggest that you should start at primary school level.
KBK
not rated yet Jul 06, 2010
Audiophiles and audio grade cable and wire manufacturing companies have been working with grain boundary issues for over 20 years.

In that time, they've been doing everything, up to and including, -THE- absolute cutting edge work in those areas.

All in order to get rid of the last bit of transient noise or '1/f' diode like noise that can be heard in the audio signal as what is literally and truly a molecular level 'grain boundary' effect.

Exactly the issue being dealt with here.

So... if superconductor designing scientists, researchers and theoreticians want to know the cutting edge concerns in making practical solutions to such issues as grain boundaries, then they have to go and start bugging the audio wire design people for their most protected assets, which are the information on how to get rid of grain boundary issues as much as is humanly possible.

I DO know what I'm talking about, I hold a patent that deals -very specifically now-....with this exact issue.
Skeptic_Heretic
1 / 5 (1) Jul 21, 2010
You know; if no "solutions" are found then the research funding continues to flow. It would be like a drug company selling a cure - it puts them out of business eventually. If science figures out how to mass produce high temp superconductors, how many researchers are put out of work?

You mean after they collect their Nobel prizes and receive high paying jobs as professors at colleges and universities?