Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Locationg crucial atoms in superconductors

29.08.2005


With an advanced imaging technique and a savvy strategy, researchers at Cornell University’s Laboratory of Atomic and Solid State Physics (LAASP) have shown how adding charge-carrying atoms like oxygen to a superconductor can increase the material’s ability to conduct electricity overall and -- paradoxically -- to decrease it in localized spots.



The discovery, published in the Aug. 12 issue of Science, could lead to the eventual development of more effective superconductors.

The scientists, led by Cornell professor of physics J.C. Séamus Davis, used a specialized scanning tunneling microscope (STM) in the basement of Cornell’s Clark Hall for the research. They identified for the first time the locations of individual oxygen atoms within a particular superconductor’s molecular structure and used that information to examine how the atoms affect current flow in their immediate vicinity. It’s a small but vital step, they say, toward understanding how superconductors work.


Superconductors are materials that conduct electricity with virtually no resistance. The materials, in this case copper-based compounds (cuprates) doped with charge-carrying atoms like oxygen and cooled to extremely low temperatures, are widely used in fields from medicine to the military. But the physics behind them is still not well understood, making the ultimate goal of creating a room-temperature superconductor elusive.

Researchers have long suspected that dopant atoms -- crucial for conductivity because they attract electrons and leave the positively charged gaps that allow current to flow without resistance -- are actually counterproductive because they create electronic disorder at the atomic level. But until now, no one had been able to look closely enough at the atomic structure to confirm the correlation.

The researchers at Cornell tackled the problem by preparing samples of a cuprate superconductor doped with different concentrations of oxygen atoms. Using the STM, which can measure current in areas less than a nanometer wide -- the width of three silicon atoms -- they mapped the materials according to how well or poorly current flowed in each point on the plane. The locations of the oxygen atoms, they found, correlated with the areas of energy disorder they had already identified.

"Now we can put the dopant atoms into the image and ask, are they correlated with the electronic disorder directly?" said Davis. "When the dopants are far away, electron waves are homogeneous." When the dopant atoms are near the conducting plane, though, the waves become drastically heterogeneous, causing the superconductivity to break down.

Think of the compound’s electrons as dancers moving together in a carefully choreographed production, Davis said.

"Superconductivity is made by pairing two electrons. It’s like a dance -- not a waltz, but a distributed dance like a contra dance," Davis said. "If you put stones in the middle of the dance floor you disturb the pattern. And once you’ve destroyed all the pairs, you’ve destroyed the superconductivity."

But (and here the contra dance analogy breaks down a little) the stones -- in this case, the dopant atoms -- are prerequisites for the dance. So taking them out isn’t an option.

"These atoms have to be working in two different ways -- one way on average and another way locally," said Kyle McElroy, a postdoctoral researcher at the University of California-Berkeley and co-author of the paper. "One of the big questions is why different cuprate families superconduct at different temperatures. There’s a spread of four to five times the transition temperature. Why do these transition temperatures change so much, and what is governing that?"

Experts predict that the worldwide market for superconductors will reach $5 billion by the year 2010 from about half that in 2000 -- if growth continues linearly. But if scientists can learn to make materials that superconduct at higher temperatures, the market could skyrocket.

"This kind of information is a necessary step toward understanding first the mechanism of high temperature superconductivity and, next, how to raise the transition temperatures," said James Slezak, co-author of the paper and a graduate student in physics at Cornell.

The paper’s other authors include D.H. Lee of the University of California-Berkeley, H. Eisaki of the National Institute of Advanced Industrial Science and Technology, Ibaraki, Japan, and S. Uchida of the University of Tokyo.

Blaine P. Friedlander | EurekAlert!
Further information:
http://www.cornell.edu

More articles from Physics and Astronomy:

nachricht APEX takes a glimpse into the heart of darkness
25.05.2018 | Max-Planck-Institut für Radioastronomie

nachricht First chip-scale broadband optical system that can sense molecules in the mid-IR
24.05.2018 | Columbia University School of Engineering and Applied Science

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Powerful IT security for the car of the future – research alliance develops new approaches

The more electronics steer, accelerate and brake cars, the more important it is to protect them against cyber-attacks. That is why 15 partners from industry and academia will work together over the next three years on new approaches to IT security in self-driving cars. The joint project goes by the name Security For Connected, Autonomous Cars (SecForCARs) and has funding of €7.2 million from the German Federal Ministry of Education and Research. Infineon is leading the project.

Vehicles already offer diverse communication interfaces and more and more automated functions, such as distance and lane-keeping assist systems. At the same...

Im Focus: Molecular switch will facilitate the development of pioneering electro-optical devices

A research team led by physicists at the Technical University of Munich (TUM) has developed molecular nanoswitches that can be toggled between two structurally different states using an applied voltage. They can serve as the basis for a pioneering class of devices that could replace silicon-based components with organic molecules.

The development of new electronic technologies drives the incessant reduction of functional component sizes. In the context of an international collaborative...

Im Focus: LZH showcases laser material processing of tomorrow at the LASYS 2018

At the LASYS 2018, from June 5th to 7th, the Laser Zentrum Hannover e.V. (LZH) will be showcasing processes for the laser material processing of tomorrow in hall 4 at stand 4E75. With blown bomb shells the LZH will present first results of a research project on civil security.

At this year's LASYS, the LZH will exhibit light-based processes such as cutting, welding, ablation and structuring as well as additive manufacturing for...

Im Focus: Self-illuminating pixels for a new display generation

There are videos on the internet that can make one marvel at technology. For example, a smartphone is casually bent around the arm or a thin-film display is rolled in all directions and with almost every diameter. From the user's point of view, this looks fantastic. From a professional point of view, however, the question arises: Is that already possible?

At Display Week 2018, scientists from the Fraunhofer Institute for Applied Polymer Research IAP will be demonstrating today’s technological possibilities and...

Im Focus: Explanation for puzzling quantum oscillations has been found

So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics

Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

In focus: Climate adapted plants

25.05.2018 | Event News

Save the date: Forum European Neuroscience – 07-11 July 2018 in Berlin, Germany

02.05.2018 | Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

 
Latest News

In focus: Climate adapted plants

25.05.2018 | Event News

Flow probes from the 3D printer

25.05.2018 | Machine Engineering

Less is more? Gene switch for healthy aging found

25.05.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>