Ray of light could lead to next generation of superconductors

August 27, 2012
Proffesor Yoram Dagan works in Tel Aviv University's Department of Physics and Center for Nanoscience and Nanotechnology. Credit: American Friends of Tel Aviv University (AFTAU)

A superconductor, which can move electrical energy with no wasteful resistance, is the holy grail of cost-effective, efficient, and "green" power production. Unlike traditional conductors such as copper or silver, which waste power resources and lose energy when they heat up, an ideal superconductor would continuously carry electrical current without losing any power.

But creating a true superconductor is tricky. Though the concept of is more than two decades old, finding and controlling the right materials has been a challenge. Now Prof. Yoram Dagan of Tel Aviv University's Department of Physics and Center for Nanoscience and Nanotechnology has discovered an innovative way to manipulate superconducting materials.

Temperature is a crucial element for , explains Prof. Dagan—each material has a critical temperature when it becomes superconducting. But by manipulating different types of light, including UV and visible light, he and his fellow researchers are able to alter the critical temperatures of superconducting materials. This finding adds to a growing toolbox for controlling and improving the technology.

The research has been published in Angewandte Chemie and featured in Nature Nanotechnology.

Shining a light

Scientists have long sought ways to alter the temperature of superconducting materials, making them more practical. One of these methods includes chemical doping, removing or adding ions such as oxygen to alter the critical temperature of the material. But Prof. Dagan said that he and his fellow researchers were inspired to find a simpler way.

In the lab, they put a , one thick, atop a superconducting film, approximately 50 thick. When researchers shined a light on these molecules, the molecules stretched and changed shape, altering the properties of the superconducting film—most importantly, altering the critical temperature at which the material acted as a superconductor.

The researchers tested three separate molecules. The first was able to increase the critical temperature of the superconducting film. With the second molecule, they found that shining an ultraviolet light heightened the material's critical temperature, while visible light lowered it. Finally, with the third molecule, they found that simply by turning a light on, was raised—and lowered again when the light was switched off. Prof. Dagan calls this discovery a new "knob" for controlling the temperature of .

Small changes, big impact

The power of this finding is that instead of changing the temperature of the material itself, a more complicated process, the material can remain at the same temperature when the film is altered. This is a small change that results in very large responses from devices, says Prof. Dagan: "It's a strong response for a small amount of light."

One of the potential future applications of this finding might be a "non-dissipated memory," which would be able to save data and run continuously without generating heat and wasting energy.

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5 / 5 (3) Aug 27, 2012
So shining a light to this film changes the critical temperature of the superconducting part. But how much is the change? 1 degree, 10 degrees? Probably not enough to raise the temperature to practical temps.
1 / 5 (6) Aug 27, 2012
The article reference is here. You're right, the change in Tc is quite minute, bellow one Kelvin only. The photoelectrons released with organic matter probably contribute to the compression of electrons within hole stripes inside of underlying superconductor layer. It similar effect to the doping of graphene films with electron donors, which makes them superconductive as well. It's an interesting effect, but many of such effects can be actually observed in this field - they do serve well as a grant and salary generators for physicists involved - but we have way more significant findings (Prins, Eck) ignored in this field anyway. The physicists know quite well, which findings are important up to level, which could threat their own research in this field and they avoid them systematically in similar way, like the cold fusion findings. Such a silly ignorance is actually intentional and strategical behavior.
not rated yet Aug 30, 2012
It is interesting effect. I intend to suggest anologous experiments in Chernogolovka to get room temperature superconductor by excitations of electrons to higher band, to the point where are levels of large effective negative electron mass. At this neiborhood there is superconducting instability of electronic levels.
The lamp is the question, and i think that i can solve this question.
not rated yet Aug 30, 2012
Excuse, LIGHT negative effective mass electronic Bloch levels
1 / 5 (1) Sep 03, 2012
This is not an unsuspected result. Superconduction initiates when a Mott-array of localised states reaches a critical density. Usually this requires a lowering in temperature: But as is well known you can can also manipulate the density of localised states with light.

A better way is to increase the density of electrons by extracting them by an anode from a suitably n-type doped substrate. The substrate and anode act as a one-dimensional cavity within which the extracted electron-waves fuse to form a superconductor. A critical temperature is not required in this case since the condensate is formed in the same way that photons condense within a laser cavity to form a SINGLE stationary light wave.

Thus the extracted condensate of electrons can SC at any temperature at which the properties of the substrate and anode remains the same. In the case of oxygen-doped n-type diamond and a gold-plated anode, SC can be routinely obtained up to and even above 400 Celsius.
1 / 5 (1) Sep 04, 2012
The opposite effect, when the laser light induced superconductivity is described here. Again, it's minute effect, working just under fraction of second.
1 / 5 (1) Sep 05, 2012
The opposite effect, when the laser light induced superconductivity is http://www.ox.ac....01.html. Again, it's minute effect, working just under fraction of second.

What do you mean by "opposite effect". Light excites electron-states and can either increase or decrease states with the same energy. Superconduction occurs when stationary Mott-states reach a critical density and exceeds this density. Wnen light increases the density of these states the critical temperature will increase. When light decreases the density of these states the critical temperature decreases: QED
not rated yet Sep 07, 2012
The opposite effect, when the laser light induced superconductivity is http://www.ox.ac....01.html. Again, it's minute effect, working just under fraction of second.
There is more impressive example: fire-ball!!!

I eyewitnessed the experiment with our low energy laser of 500 Watt. It took the laser 30 seconds to make circular hole in the glass the same diameter as of fire-ball. So the energy of fire-ball can be estimated as 500Watt*30 seconds :)
It was in 1975 (may be 1976).
not rated yet Sep 07, 2012
To my mind fire-ball is condensed gas of rydberg atoms with delocalised electrons. Due to excited electrons form a band in gas and due to dispersion of electron levels with "hole-like" law fire-ball gets "superconducting" levels for excited electrons and fire-ball becomes superconducting and flyes in atmosfere above the earth.
not rated yet Sep 07, 2012
"the laser light induced superconductivity" is not effective if there is only one frequency laser light.
The wave function of "superconducting" electron level has rather specific form. And as i see nobody knows this wave function :)

More effective may be TWO laser light with THE different coherent frequences :) OR unlaser light lamp.
1 / 5 (1) Sep 07, 2012
"The wave function of "superconducting" electron level has rather specific form. And as i see nobody knows this wave function :)

Not correct.

Within the low temperature metals the wave-function of a superconducting charge-carrier is in most cases a 3D localised Wigner-state with a Gaussian shape, anchored by an induced positive charge at the center of the orbital. Hence the strong isotope effect in most of these metals.

In the ceramics, these localised states are two dimensional localised Wigner-states between the crystallographic layers. The positive charges anchoring them are within the crystallographic layers: Therefore the isotopic effect is subdued.

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