Light touch transforms material into a superconductor

Jan 14, 2011
Andrea Cavalleri used laser light to transform a material into a superconductor

(PhysOrg.com) -- A non-superconducting material has been transformed into a superconductor using light, Oxford University researchers report.

One hundred years after was first observed in 1911, the team from Oxford, Germany and Japan observed conclusive signatures of superconductivity after hitting a non-superconductor with a strong burst of .

‘We have used light to turn a normal insulator into a superconductor,’ says Professor Andrea Cavalleri of the Department of Physics at Oxford University and the Max Planck Department for Structural Dynamics, Hamburg. ‘That’s already exciting in terms of what it tells us about this class of materials. But the question now is can we take a material to a much higher temperature and make it a superconductor?’

The material the researchers used is closely related to high-temperature copper oxide , but the arrangement of electrons and atoms normally act to frustrate any electronic current.

In the journal Science, they describe how a strong infrared laser pulse was used to perturb the positions of some of the atoms in the material. The compound, held at a temperature just 20 degrees above absolute zero, almost instantaneously became a superconductor for a fraction of a second, before relaxing back to its normal state.

Superconductivity describes the phenomenon where an electric current is able to travel through a material without any resistance – the material is a perfect electrical conductor without any energy loss.

High-temperature superconductors can be found among a class of materials made up of layers of copper oxide, and typically superconduct up to a temperature of around –170°C. They are complex materials where the right interplay of the atoms and electrons is thought to ‘line up’ the electrons in a state where they collectively move through the material with no resistance.

‘We have shown that the non-superconducting state and the superconducting one are not that different in these materials, in that it takes only a millionth of a millionth of a second to make the electrons “synch up” and superconduct,’ says Professor Cavalleri. ‘This must mean that they were essentially already synched in the non-superconductor, but something was preventing them from sliding around with zero resistance. The precisely tuned laser light removes the frustration, unlocking the superconductivity.’

The advance immediately offers a new way to probe with great control how superconductivity arises in this class of materials, a puzzle ever since high-temperature superconductors were first discovered in 1986.

But the researchers are hopeful it could also offer a new route to obtaining superconductivity at higher temperatures. If superconductors that work at room temperature could be achieved, it would open up many more technological applications.

‘There is a school of thought that it should be possible to achieve superconductivity at much higher temperatures, but that some competing type of order in the material gets in the way,’ says Professor Cavalleri. ‘We should be able to explore this idea and see if we can disrupt the competing order to reveal superconductivity at higher temperatures. It’s certainly worth trying!’

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gmurphy
5 / 5 (3) Jan 14, 2011
I'm a little bit stunned by this, what were the dimensions of the sample?, did the light only have to hit the exterior of the sample of the effective?, how long did the sample remain superconducting once the light had been removed?, surely the addition of light energy should have increased the inherent energy of the sample?, physicists have the coolest jobs :D
Nik_2213
5 / 5 (1) Jan 14, 2011
How weird !!

At least it offers a new, elegant way to study the complex transition between 'normal' and 'superconductor'...
electrodynamic
5 / 5 (1) Jan 14, 2011
That's a good point you can watch the transition, and get a lot of clues to the mechanics involved. I wonder if there isn't some direct interactions between the light, and electrons, maybe getting all of them to look in the same direction for example.
Macksb
1 / 5 (1) Jan 14, 2011
This is additional evidence in favor of a theory that I have posted in other Phys Org comments on superconductivity. Superconductivity arises from synchronized oscillations. Think of Huygens' pendulum clocks. See Art Winfree's work on coupled oscillators, in biology, in the late 1960s. Read Sync by Steve Strogatz.

Laser light is itself synchronized oscillations. These light oscillations synchronize the oscillations of the electrons, pairing them. This is the same as synchronized phonons (which are oscillations) creating Cooper pairs of electrons in BCS theory.

This theory (the Macksb - Winfree theory) has the additional virtue of unifying our understanding of several types of superconductivity that are generally, and improperly, thought to be quite different from each other.

Incidentally, my guess is that the electrons were not "essentially synched" immediately before the application of the laser light, contrary to the speculation in the article.
hush1
not rated yet Jan 14, 2011
"...strong infrared laser pulse was used to perturb the positions of some of the atoms in the material."

lol

"High-Tc superconductors plug ‘terahertz gap’

Nov 23, 2007 (@ Physicsworlddotcom) 'Old' news.

Wedlock? Josephson junctions and laser?
Superconducting resonating cavities?
Are the Coopers (pair) getting a divorce?

Stay tuned - As the world turns. :)
kz1300club
1 / 5 (1) Jan 15, 2011
We can make electrical conductors superconductive right now - kz1300(dot)com/hfgc

At least one company I know of has said the way we've been making electric motors has been wrong from the beginning. Harmonic frequencies is a game changer. Check google for some of these terms and you'll see what I mean.
Macksb
1 / 5 (1) Jan 15, 2011
Elaborating on my prior post above, Cavalleri says:

"This must mean that they were essentially already synched in the non-superconductor, but something was preventing them from sliding around with zero resistance. The precisely tuned laser light removes the frustration...."

As to the first clause, synch had not yet occurred, as I mentioned above. The synched oscillations of the laser light were the tipping factor first at and near the surface, then more deeply inside the material.

As to the second clause, sliding around with zero resistance becomes possible when all the electrons are woven together by their orbits and spins--their electromagnetic waves. These wave oscillations synched (four ways, I believe...two by two d wave symmetry). That creates a superfluid of electrons, in double Cooper pairs, all in mass synchrony. They flow for an instant, but the flow itself creates turbulence. See the Phys Org article on superfluid laser light, two months ago.
Macksb
1 / 5 (1) Jan 16, 2011
Let me put it this way:

BCS theory: phonons (organized) interacting with electrons = superconductivity

This experiment: photons (organized) interacting with electrons = superconductivity

phonons = quanta = oscillations
photons = quanta = oscillations

Art Winfree: all limit cycle oscillations have a tendency to synchronize

Superconductivity, superfluidity = synchronized oscillations

Fully synchronized. Thus zero viscosity, diamagnetic.

Macksb
3 / 5 (2) Jan 17, 2011
Here is how it works:

The laser photons act like a metronome, or better yet, a million perfect drummers all beatng their drums at exactly the same time.

This causes the electrons in the material to modify their oscillations. Some advance their phase a little, in varying degrees, and some retard their phase a little, in varying degrees. Soon (and here I mean in nanoseconds) the electrons all oscillate to the synchronized beat.

By oscillations, I mean the two oscillations in the electromagnetic waves--spin and orbit.

This creates a perfectly woven fabric of electomagnetic oscillations. Warp and weft all in a perfect basketweave of oscillations. That magic carpet is the essence of superconductivity.

If you want to think in waves and particles, the waves weave together perfectly; and that forces the particles into one, and only one, possible position, in which all the fermions pair and so become bosons.