Superconducting secrets solved after 30 years

Jun 17, 2014
Map of superconducting copper oxide structure. Credit: Nicolle R Fuller

(Phys.org) —A breakthrough has been made in identifying the origin of superconductivity in high-temperature superconductors, which has puzzled researchers for the past three decades.

Harnessing the enormous technological potential of – which could be used in lossless electrical grids, next-generation supercomputers and levitating trains – could be much more straightforward in future, as the origin of in these materials has finally been identified.

Superconductors, materials which can carry electric current with zero resistance, could be used in a huge range of applications, but a lack of understanding about where their properties originate from has meant that the process of identifying new materials has been rather haphazard.

Researchers from the University of Cambridge have found that ripples of electrons, known as or charge order, create twisted 'pockets' of electrons in these materials, from which superconductivity emerges. The results are published in the June 15th issue of the journal Nature.

Low-temperature, or conventional, were first identified in the early 20th century, but they need to be cooled close to absolute zero (zero degrees on the Kelvin scale, or -273 degrees Celsius) before they start to display superconductivity. So-called high-temperature superconductors however, can display the same properties at temperatures up to 138 Kelvin (-135 degrees Celsius), making them much more suitable for practical applications.

Since they were first identified in the mid-1980s, the process of discovering new high-temperature superconductors could be best described as random. While researchers have identified the ingredients that make for a good low-temperature superconductor, high-temperature superconductors have been more reluctant to give up their secrets.

In a superconductor, as in any electronic device, current is carried via the charge on an electron. What is different about superconductors is that the electrons travel in tightly bound pairs. When travelling on their own, electrons tend to bump into each other, resulting in a loss of energy. But when paired up, the electrons move smoothly through a superconductor's structure, which is why superconductors can carry current with no resistance. As long as the temperature is kept sufficiently low, the electron pairs will keep moving through the superconductor indefinitely.

Key to are the interactions of electrons with the lattice structure of the material. These interactions generate a type of 'glue' which holds the electrons together. The strength of the glue is directly related to the strength of the superconductor, and when the superconductor is exposed to an increase in temperature or strength, the glue is weakened, the electron pairs break apart and superconductivity is lost.

"One of the problems with high-temperature superconductors is that we don't know how to find new ones, because we don't actually know what the ingredients are that are responsible for creating in the first place," said Dr Suchitra Sebastian of the Cavendish Laboratory, lead author of the paper. "We know there's some sort of glue which causes the electrons to pair up, but we don't know what that glue is."

In order to decode what makes high-temperature superconductors tick, the researchers worked backwards: by determining what properties the materials have in their normal, non-superconducting state, they might be able to figure out what was causing superconductivity.

"We're trying to understand what sorts of interactions were happening in the material before the electrons paired up, because one of those interactions must be responsible for creating the glue," said Dr Sebastian. "Once the electrons are already paired up, it's hard to know what made them pair up. But if we can break the pairs apart, then we can see what the electrons are doing and hopefully understand where the superconductivity came from."

Superconductivity tends to override other properties. For example, if in its normal state a superconductor was a magnet, suppressing that magnetism has been found to result in superconductivity. "So by determining the normal state of a superconductor, it would make the process of identifying new ones much less random, as we'd know what sorts of materials to be looking for in the first place," said Dr Sebastian.

Working with extremely strong magnetic fields, the researchers were able to kill the superconducting effect in cuprates - thin sheets of copper and oxygen separated by more complex types of atoms.

Previous attempts to determine the origins of superconductivity by determining the normal state have used temperature instead of magnetic field to break the apart, which has led to inconclusive results.

As cuprates are such good superconductors, it took the strongest magnetic fields in the world – 100 Tesla, or roughly one million times stronger than the Earth's magnetic field – in order to suppress their superconducting properties.

These experiments were finally able to solve the mystery surrounding the origin of pockets of electrons in the normal state that pair to create superconductivity. It was previously widely held that electron pockets were located in the region of strongest superconductivity. Instead, the present experiments using strong magnetic fields revealed a peculiar undulating twisted pocket geometry -similar to Jenga bricks where each layer goes in a different direction to the one above or beneath it.

These results pinpointed the pocket locations to be where superconductivity is weakest, and their origin to be ripples of known as charge density waves, or charge order. It is this normal state that is overridden to yield superconductivity in the family of studied.

"By identifying other materials which have similar properties, hopefully it will help us find new superconductors at higher and higher temperatures, even perhaps materials which are superconductors at room temperature, which would open up a huge range of applications," said Dr Sebastian.

Explore further: Insights into the stages of high-temperature superconductivity

More information: "Normal-state nodal electronic structure in underdoped high-Tc copper oxides." Suchitra E. Sebastian, et al. Nature (2014) DOI: 10.1038/nature13326. Received 12 January 2014 Accepted 02 April 2014 Published online 15 June 2014

add to favorites email to friend print save as pdf

Related Stories

Superconductivity's third side unmasked

Jun 17, 2011

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 ...

Recommended for you

And so they beat on, flagella against the cantilever

4 hours ago

A team of researchers at Boston University and Stanford University School of Medicine has developed a new model to study the motion patterns of bacteria in real time and to determine how these motions relate ...

Tandem microwave destroys hazmat, disinfects

8 hours ago

Dangerous materials can be destroyed, bacteria spores can be disinfected, and information can be collected that reveals the country of origin of radiological isotopes - all of this due to a commercial microwave ...

Physicists design zero-friction quantum engine

8 hours ago

(Phys.org) —In real physical processes, some energy is always lost any time work is produced. The lost energy almost always occurs due to friction, especially in processes that involve mechanical motion. ...

Cornell theorists continue the search for supersymmetry

10 hours ago

(Phys.org) —It was a breakthrough with profound implications for the world as we know it: the Higgs boson, the elementary particle that gives all other particles their mass, discovered at the Large Hadron ...

User comments : 21

Adjust slider to filter visible comments by rank

Display comments: newest first

verkle
4.5 / 5 (16) Jun 17, 2014
That last statement captures it all:

By identifying other materials which have similar properties, hopefully it will help us find new superconductors at higher and higher temperatures, even perhaps materials which are superconductors at room temperature, which would open up a huge range of applications.


This kind of work is true science. Well done!

h20dr
4.6 / 5 (8) Jun 17, 2014
Awesome. Hope it leads to amazing new discoveries and products that will change how we live for the better.
Sikla
Jun 17, 2014
This comment has been removed by a moderator.
Sikla
Jun 17, 2014
This comment has been removed by a moderator.
Dr_toad
Jun 17, 2014
This comment has been removed by a moderator.
Sikla
Jun 17, 2014
This comment has been removed by a moderator.
Sikla
Jun 17, 2014
This comment has been removed by a moderator.
Sikla
Jun 17, 2014
This comment has been removed by a moderator.
Sikla
Jun 17, 2014
This comment has been removed by a moderator.
Sikla
Jun 17, 2014
This comment has been removed by a moderator.
FMA
1 / 5 (13) Jun 17, 2014
Very soon, people on earth can create anti-gravity aircraft (not a UFO any more) and travel to other part of the universe.
katesisco
1 / 5 (11) Jun 17, 2014
Excellent work but I doubt the anti gravity as it would probably depend on our current state of the monopole sun's unique energy being longer lasting than the temporary state it currently displays.
This is perhaps the reason for NASA proposal of launch this coming fall to be sited where our Earth's magnetosphere intercepts the solar emissions. If this energy---wonderfully strong and unlimited can be stored and manipulated--- then such futuristic concepts may actually be possible.
Jantoo
1 / 5 (8) Jun 17, 2014
Note that the electron squeezing is actually even the underlying principle of low temperature superconductors too. The BCS theory based on electron pairing model is nice and all, but it doesn't explain, why the superconductivity occurs in niobium but not sodium - despite the sodium has lotta movable electrons available. The actual reason is, the sodium atom has only one type of electron orbitals around itself, but the niobium has both large both short bonds. The long bonds are attractive and they do squeeze the electrons within short bonds between them. The mutual balance of attractive and repulsive forces is what makes the good superconductors so brittle. The superconductors of I type just realize the squeezing of electrons between orbitals of atoms (orbital cage), whereas the superconductors of II type utilize the whole atom lattice for it (lattice cage). And the ultraconductors do utilize the macroscopic (supramolecular and even larger cages) structures for squeezing of electrons.
betterexists
5 / 5 (1) Jun 17, 2014
Works of India's/Cal. TalyarKhan & a U.S Scientist of mid 1980's in this field come to mind.
So much work behind the curtain, it seems.
Rusi P. Taleyarkhan is a faculty member in the Department of Nuclear Engineering at Purdue University since 2003
Jantoo
2.2 / 5 (5) Jun 17, 2014
So much work behind the curtain, it seems.
Yep, every just a bit more interesting finding gets classified for not to help the other "enemies". The boring publicly available research presented here at PhysOrg is just screenshow for masses required for occupation of people involved.
sandler
5 / 5 (1) Jun 17, 2014
When travelling on their own, electrons tend to bump into each other, resulting in a loss of energy. But when paired up, the electrons move smoothly through a superconductor's structure.

I wonder why the above happens. May be pairing stops electrons sideways rotation but preserves forward flow. If so would it be possible to entangle the pairs together like carts in a freight train, and if it will allow superconductivity at normal temperatures.
sandler
5 / 5 (1) Jun 17, 2014
In other words using some structure resembling a rail to hold them together.
dedereu
not rated yet Jun 17, 2014
This experimental difficult work at very high field measures precisely the normal state Fermi surface of the high temperature superconductors as modified by two charges density waves vectors.
But the physical origin of theses density waves, likely slowly fluctuating and the detailed origin of the high superconductivity temperature remains to be solved.
Other similar materials, will have different properties, in particular if the slow charge density waves fluctuations are essential for this superconductivity.
The room temperature superconductivity remains a pure dream.
George_Rajna
Jun 18, 2014
This comment has been removed by a moderator.
Mark_Goldes
1 / 5 (3) Jun 18, 2014
Ultraconductors are proprietary polymer equivalents of room temperature superconductors.

They have been proven capable of conducting electricity at least 100,000 times better than gold, silver or copper, at temperatures near absolute zero to as high as 200 degrees C (390 degrees F),

Four SBIRs, including a Phase II with the USAF, were completed before work was interrupted for lack of capital. Almost 1,000 samples were independently made for the Air Force.

A number of papers have been published in refereed journals. Development is in the process of resuming. See ULTRACONDUCTORS at www.aesopinstitute.org

johanfprins
5 / 5 (2) Jun 18, 2014
"We know there's some sort of glue which causes the electrons to pair up, but we don't know what that glue is."

They know NOTHING of the sort since electrons need not to be "glued together" in order for super-conduction to occur.

Sikla
Jun 18, 2014
This comment has been removed by a moderator.
EnricM
5 / 5 (4) Jun 18, 2014
Excellent work but I doubt the anti gravity as it would probably depend on our current state of the monopole sun's unique energy being longer lasting than the temporary state it currently displays.


I read the US government has started a lawsuite based on the Clayton Act 1914 against the sun.

theon
not rated yet Jun 20, 2014
Excellent work but I doubt the anti gravity as it would probably depend on our current state of the monopole sun's unique energy being longer lasting than the temporary state it currently displays.


I read the US government has started a lawsuite based on the Clayton Act 1914 against the sun.


Great! Can I sign it?
sirchick
5 / 5 (1) Jun 20, 2014
I will crap bricks in excitement if we find room temp super conductors
otero
Jun 20, 2014
This comment has been removed by a moderator.
sandler
not rated yet Jun 20, 2014
If they can use strong magnetic fields to create a stable pair of electrons why can't they do the same with atoms and create cold fusion energy? http://tinyurl.com/lnu4ely
russell_russell
not rated yet Jun 21, 2014
Any furrow (trough) offers potential railing.
@sandler
otero
Jun 21, 2014
This comment has been removed by a moderator.
Mark_Goldes
1 / 5 (1) Jun 23, 2014
Re: Ultraconductors, the polymer equivalents of room temperature superconductors mentioned earlier, the Final Reports from the four SBIR contracts are available free upon request.

See Ultraconductors at www.aesopinstitute.org and contact me if you would like a copy.
George_Rajna
Jun 23, 2014
This comment has been removed by a moderator.
TimLong2001
not rated yet Jun 23, 2014
Of course the "glue" is the charge attraction between the electron and the positive component contained in the conductor. Rotation keeps them apart at a specific radius which determines the wavelength. High stability is the key for this photon-like "pair" to propagate efficiently, which low temperature achieves more easily.
FMA
not rated yet Jun 23, 2014
I found a clip that shows anti-gravity is related to the superconductivity.

https://www.youtu...sEO5t-TM

vtology
not rated yet Jul 01, 2014
Dr. Deborah D. L. Chung discovered and published technology for effective, practical room temperature superconductivity in the year 2000. Why is the scientific community seemingly pretending otherwise? Quoting from Dr. Chung's abstract: "Apparent negative electrical resistance was observed, quantified, and controlled through composite engineering." See: http://wings.buff...ymer.pdf . I would not ask for a finder's fee, but I am completely broke and unemployed. Would someone please take this seriously.