• Atoms of niobium and nitrogen in an ultrathin superconducting film that helped MIT researchers discover a universal law of superconductivity.

    Atoms of niobium and nitrogen in an ultrathin superconducting film that helped MIT researchers discover a universal law of superconductivity.

    Image: Yachin Ivry

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New law for superconductors

Atoms of niobium and nitrogen in an ultrathin superconducting film that helped MIT researchers discover a universal law of superconductivity.

Mathematical description of relationship between thickness, temperature, and resistivity could spur advances.


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MIT researchers have discovered a new mathematical relationship — between material thickness, temperature, and electrical resistance — that appears to hold in all superconductors. They describe their findings in the latest issue of Physical Review B.

The result could shed light on the nature of superconductivity and could also lead to better-engineered superconducting circuits for applications like quantum computing and ultralow-power computing.

“We were able to use this knowledge to make larger-area devices, which were not really possible to do previously, and the yield of the devices increased significantly,” says Yachin Ivry, a postdoc in MIT’s Research Laboratory of Electronics, and the first author on the paper.

Ivry works in the Quantum Nanostructures and Nanofabrication Group, which is led by Karl Berggren, a professor of electrical engineering and one of Ivry’s co-authors on the paper. Among other things, the group studies thin films of superconductors.

Superconductors are materials that, at temperatures near absolute zero, exhibit no electrical resistance; this means that it takes very little energy to induce an electrical current in them. A single photon will do the trick, which is why they’re useful as quantum photodetectors. And a computer chip built from superconducting circuits would, in principle, consume about one-hundredth as much energy as a conventional chip.

“Thin films are interesting scientifically because they allow you to get closer to what we call the superconducting-to-insulating transition,” Ivry says. “Superconductivity is a phenomenon that relies on the collective behavior of the electrons. So if you go to smaller and smaller dimensions, you get to the onset of the collective behavior.”

Vexing variation

Specifically, Ivry studied niobium nitride, a material favored by researchers because, in its bulk form, it has a relatively high “critical temperature” — the temperature at which it switches from an ordinary metal to a superconductor. But like most superconductors, it has a lower critical temperature when it’s deposited in the thin films on which nanodevices rely.

Previous theoretical work had characterized niobium nitride’s critical temperature as a function of either the thickness of the film or its measured resistivity at room temperature. But neither theory seemed to explain the results Ivry was getting. “We saw large scatter and no clear trend,” he says. “It made no sense, because we grew them in the lab under the same conditions.”

So the researchers conducted a series of experiments in which they held constant either thickness or “sheet resistance,” the material’s resistance per unit area, while varying the other parameter; they then measured the ensuing changes in critical temperature. A clear pattern emerged: Thickness times critical temperature equaled a constant — call it A — divided by sheet resistance raised to a particular power — call it B.

After deriving that formula, Ivry checked it against other results reported in the superconductor literature. His initial excitement evaporated, however, with the first outside paper he consulted. Though most of the results it reported fit his formula perfectly, two of them were dramatically awry. Then a colleague who was familiar with the paper pointed out that its authors had acknowledged in a footnote that those two measurements might reflect experimental error: When building their test device, the researchers had forgotten to turn on one of the gases they used to deposit their films.

Broadening the scope

The other niobium nitride papers Ivry consulted bore out his predictions, so he began to expand to other superconductors. Each new material he investigated required him to adjust the formula’s constants — A and B. But the general form of the equation held across results reported for roughly three dozen different superconductors.

It wasn’t necessarily surprising that each superconductor should have its own associated constant, but Ivry and Berggren weren’t happy that their equation required two of them. When Ivry graphed A against B for all the materials he’d investigated, however, the results fell on a straight line.

Finding a direct relationship between the constants allowed him to rely on only one of them in the general form of his equation. But perhaps more interestingly, the materials at either end of the line had distinct physical properties. Those at the top had highly disordered — or, technically, “amorphous” — crystalline structures; those at the bottom were more orderly, or “granular.” So Ivry’s initial attempt to banish an inelegance in his equation may already provide some insight into the physics of superconductors at small scales.

“None of the admitted theory up to now explains with such a broad class of materials the relation of critical temperature with sheet resistance and thickness,” says Claude Chapelier, a superconductivity researcher at France’s Alternative Energies and Atomic Energy Commission. “There are several models that do not predict the same things.”

Chapelier says he would like to see a theoretical explanation for that relationship. But in the meantime, “this is very convenient for technical applications,” he says, “because there is a lot of spreading of the results, and nobody knows whether they will get good films for superconducting devices. By putting a material into this law, you know already whether it’s a good superconducting film or not.”


Topics: Physics, Electrical Engineering & Computer Science (eecs), Superconductors, School of Engineering, Research, Nanoscience and nanotechnology

Comments

Try reading "Magnetism and the Atom". Written by Peter Gruich in 1967 and published by Exposition Press, this just adds more credibility to his theory.

Why doesn't this article link to the paper in question?

If I understand these results correctly, this is as important as the discovery of Ohm's law.

Ultraconductors are polymer equivalents of room temperature superconductors, useful up to 200 degrees C. The theory was published some years ago in Philosopgical Research B by Grigorov. It matches the lab experiments very well, but is distinct from theories that apply to metals and ceramics. See Ultraconductors at www.aesopinstitute.org Four SBIR contracts were completed on these materials and the Final Reports have been cleared by the DOD for public release. Any or all are available as pdf files upon request. The email address is on the website.

I just wanted to see the actual equation

In physics, laws usually come long before theoretical explanations.

The great high points of Mark Goldes’ career in fraudcraft were the obtaining of four Small Business Innovative Research grants from the Unites States Air Force, which cost taxpayers roughly a half million dollars. In the fourteen years since the conclusion of the fourth project, Goldes’ companies have evidently made no further progress in this area, at all – but that has not stopped Goldes from pretending that Magnetic Power Inc, or Chava Energy LLC, or “Aesop Institute” will be making Revolutionary Breakthroughs involving “Ultraconductors” as soon as you give them your money. In fact, MPI’s own reports on the Ultraconductor grant projects consist of a succession of rosy and wonderful claims and predictions which went entirely unfulfilled by following projects, and remain unfulfilled today.

It is important to understand that the “Ultraconductor” film was only “ultraconductive” to current across the thin dimension of the film – and not along the extensive dimensions. MPI asserted that they would develop a way to make the thin “ultraconductive” film thicker – and never did so. MPI asserted that they would develop a way to make “ultraconductive” wire – and never did so. MPI asserted that their enrichment method would become the key to making thicker film and wire – but the method never did so. MPI asserted that their “Ultraconductor” film would surely prove wonderfully useful for making thermoelectric devices – but once again, the rosy claims went unfulfilled. MPI asserted that they would obtain “ultraconductivity” along the plane of the film, instead of merely across the thin dimension, by repositioning the supposedly “ultraconductive” channels. They never did so.

The USAF never “validated” Goldes’ so-called “Ultraconductors” at all, and the USAF never gave Goldes any procurement contract for any “Ultraconductors” at all. The four research grants that Goldes obtained from the USAF were a waste of taxpayer money which never resulted in the development of anything of any value. Goldes’ degree of honesty in the matter of the “Ultraconductor” grants is just the same as his degree of honesty regarding all of his other make-believe “breakthroughs.” It is zero. Zero honesty. Zero “breakthroughs.” Zero fulfilment of his endless empty claims – as usual.

Chava Energy’s “Ultraconductor” fraudcraft was fraudulent first of all because Chava Energy has never done any development work with the so-called “Ultraconductor” film and therefore has never “continued to develop” the film at all, even though they pretended otherwise for five years. Just as Goldes had done at MPI, Chava Energy misrepresented the true prospects of the “Ultraconductor” material, which had never been found or made useful for any purpose, despite the substantial research funding that MPI had received in the nineties.

Mark Goldes was ejected from Chava Energy LLC during the fall of 2014 by Chava Energy’s other co-founder, Hagen Ruff; and all the rosy fraudcraft regarding “Ultraconductors” and “Ultraconductor Magnetic Energy Storage” was suddenly removed from the Chava Energy website. Hagen Ruff had chosen to drop the fraudulent empty pretense of ongoing “Ultraconductor” development that he and Goldes had carried on at Chava Energy for five years – along with several other fraudulent empty pretenses.

But although the partnership ended, the fraud still continues – at Mark Goldes' so-called "AESOP Institute," where it is still one of Mark Goldes' three favorite frauds - along with his pretended "NO FUEL PISTON ENGINE" and equally worthless "FUEL-FREE TURBINE."

https://goldesrufffraudcraftjo...

Why do atoms look like small solid ball bearings in pictures like the one in this article? Is it the outermost electron shell cloud that is seen? Do they look solid because the electrons are zipping around at nearly the speed of light?

I know that anything that comes out of MIT is irrationally "sexy"
according to many people, but we should all recognize that the authors
merely produced a correlation based on experimental data (theirs and
from the literature). This is not equivalent to inventing Ohm's law. Experimental correlations have great value, but it is hardly "inventing an equation", like this press release states. Mr. Ivry should be bothered by this misrepresentation, since it makes his work look less serious than it is. Hype is a disservice to science.

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