Team introduces breakthrough in understanding of high-temperature superconductivity

June 18, 2012, University of Miami

Researchers from the University of Miami (UM) are unveiling a novel theory for high-temperature superconductivity. The team hopes the new finding gives insight into the process, and brings the scientific community closer to achieving superconductivity at higher temperatures than currently possible. This is a breakthrough that could transform our world.

Superconductors are composed of specific metals or mixtures of metals that at very low temperatures allow a current to flow without resistance. They are used in everything from electric devices, to medical imaging machines, to . Although they have a wide range of applications, the possibilities are limited by temperature constraints.

"Understanding how superconductivity works at higher temperatures will make it easier to know how to look for such , how to engineer them, and then how to integrate them into new technologies," says Josef Ashkenazi, associate professor of physics at the UM College of Arts and Sciences and first author of the study. "It's always been like this when it comes to science: once you understand it, the technological applications follow."

University of Miami physics professor Josef Ashkenazi discusses supercooling with liquid nitrogen and superconductors. Credit: University of Miami

At room temperature, behave like typical metals, but when the temperature is lowered toward absolute zero (at around -273oC, or -460oF), resistance to suddenly drops to zero, making it ultra-efficient in terms of . Although is unachievable, substances such as and can be used to cool materials to temperatures approaching it.

Researchers are also working on creating materials that yield superconductivity in a less frigid environment. The point at which a matter becomes a superconductor is called critical or . So far, the highest critical temperature of a superconducting material is about -130oC (-200oF).

"But just 'cooking' that produce superconductivity at higher temperatures can be very tedious and expensive, when one doesn't know exactly how the process works," says Neil Johnson, professor of physics in the UM College of Arts and Sciences and co-author of the study.

To understand the problem, the UM team studied what happens in a metal at the exact moment when it stops being a superconductor. "At that point, there are great fluctuations in the sea of electrons, and the material jumps back and forth between being a superconductor and not being one," Johnson says.

The key to understanding what happens at that critical point lies in the unique world of quantum particles. In this diminutive universe, matter behaves in ways that are impossible to replicate in the macroscopic world. It is governed not by the laws of classical physics, but by the laws of quantum mechanics.

One of the most perplexing features of quantum mechanics is that a system can be described by the combination or 'superposition' of many possible states, with each possible state being present in the system at the same time. Raising the critical temperature of superconductors is prevented in common cases, because it creates a fragmentation of the system into separate states; this act suppresses high-temperature superconductivity.

What Ashkenazi and Johnson found is that just above the specific quantum effects can come to the floor and generate superpositions of individual states. This superposition of states provides an effective "glue," which helps repair the system, allowing superconducting behavior to emerge once again. This model provides a mechanism for high temperature superconductivity.

"Finding a path to high-temperature superconductivity is currently one of the most challenging problems in physics," says Ashkenazi. "We present for the first time, a unified approach to this problem by combining what has prevented scientists from achieving high-temperature superconductivity in the past, with what we now know is permitted under the quantum laws of nature."

"The new model combines elements at two levels: physically pulling together the fragments of the system at the quantum level, and theoretically threading together components of many other existing theories about superconductivity," Johnson says.

Understanding how is pushed beyond the present critical temperatures will help researchers recreate the phenomenon at a wider temperature range, in different materials, and could spur the development of smaller, more powerful and energy efficient technologies that would benefit society.

Explore further: Closing the 'Pseudogap' on Superconductivity

More information: The study, titled "Pairing Glue Activation in Curates within the Quantum Critical Regime," is published online ahead of print by the journal Europhysics Letters.

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4 / 5 (1) Jun 18, 2012
Well, this told me absolutely nothing about the actual model they've come up with, but I'm excited to be alive right now anyways. I dream of a scientific regime, one day, where normal people actually have free access to journal articles like that so they can understand what's actually going on. Until then, long live PLoS ONE, keep boycotting Elsevier, and may our species frontier of knowledge be ever advancing.
not rated yet Jun 18, 2012
"come to the floor" what does that mean?
5 / 5 (2) Jun 18, 2012
A generic model for the phase transition, nice.

@ chromosome2: From physics studies, what I note above is about what you get without reading the articles. Superconductors have some generic behaviors when they loose superconductivity (previously called type I and II, dunno if its changed).

@ GldfrdEng: From the context roughly "acts visibly" ("take the floor" (dance), "have the floor" (speaker)), I would guess.
1 / 5 (1) Jun 18, 2012
At first glance, it might be this...

arXiv:1111.5033 [pdf, other]

Pairing Glue Activation in Cuprates within the Quantum Critical Regime

Josef Ashkenazi, Neil F. Johnson

Comments: 4 pages, 3 figures; modified version, including clarifications, accepted for publication in EPL

Journal-ref: EPL 98, 47011 (2012)

Subjects: Superconductivity (cond-mat.supr-con); Strongly Correlated Electrons (cond-mat.str-el)

(Submitted on 21 Nov 2011 (v1), last revised 29 May 2012 (this version, v3))
1 / 5 (1) Jun 19, 2012
once you understand it, the technological applications follow.
I do understand it (electrons are compressed within lattice), because it's principally very simple effect - but it doesn't mean, we will be able to prepare the HT superconductors automatically. It's like the preparation of materials in organic chemistry: the fact we know, how the molecule should appear doesn't mean, we know how to prepare it. Even better, what the physicists mean with "understanding" is the finding of mathematical model which would describe it faithfully, but this model may not be still able to explain the principle of superconductivity intuitively. In the same way, like the finding of Newtonian law for gravity doesn't mean, we understand how this gravity is working on background. It's essentially the other league.
1 / 5 (1) Jun 19, 2012
Currently here are people, who really understand the HT superconductivity and they're able to prepare HT superconductors working at arbitrary temperature (J. Eck or J.F.Prins) - but these people are partisans for the other physicists and despite their undeniable success they're ignored with mainstream. So we can say, the approach to the mainstream science is essentially similar to cold fusion with the only difference: it doesn't attempt for denial of this effect.

If I would work at field of HT superconductivity, I'd attempt to replicate most successful experiments first - but this attempt never happened. Therefore the mainstream science is risking the very same situation like at the case of cold fusion: the first room temperature superconductor will be commercialized BEFORE the mainstream physics will admit, it even exists - which is indeed a sign of deepest ignorance.
1 / 5 (1) Jun 19, 2012
Article preprint (it does contain minimum of math, so it's essentially the same blurb, like any other qualitative description), list of articles of prof. Joseph Ashkenazi.

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