Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

'Stripes' and superconductivity -- Two faces of the same coin?

12.12.2006
Researchers at Brookhaven National Laboratory and Cornell have made a surprising discovery about the behavior of high-temperature superconductors that could be a further step toward understanding how these valuable materials work.

Previous experiments have shown that in high-temperature superconductors known as cuprates, electrons bind together in pairs. The energy required to pull a pair apart -- called the energy gap -- is different in different directions; a plot of energy vs. direction forms a cloverleaf pattern. The explanation for this so-called "pseudogap" has so far eluded physicists.

The new work finds that in a cuprate that is not a superconductor at any temperature the same cloverleaf-shaped energy gap appears. The surprise for physicists is that the same materials in two very different states apparently have identical energy-gap structures.

"This may provide a key to understanding the superconducting phenomenon," said J.C. Séamus Davis, Cornell professor of physics, who collaborated in the work with Brookhaven physicist Tonica Valla. "This is the first time that it has been possible to measure the electronic structure of this very important material. The big surprise is that we go to this state where it's not superconducting, and we measure the electronic structure, and lo and behold, it's the same [as the superconductor]."

Their experiments were described Nov. 16 in the online journal Science Express and will appear in a future print edition of Science.

Superconductors conduct electricity with virtually no resistance. The phenomenon was first discovered in materials cooled to near absolute zero by immersion in liquid helium. Certain oxides of copper called cuprates that have been "doped" with small amounts of other elements become superconducting at temperatures up to 134 kelvins (degrees above absolute zero) or more, depending on pressure. These materials can be cooled with much less expensive liquid nitrogen and are in wide use in industry.

"Doping" disrupts the crystal structure of the copper oxide, creating "holes" where electrons ought to be, and this somehow facilitates superconductivity. Physicists have been puzzled by the fact that at a certain low level of doping, many cuprates cease to superconduct, yet at levels above and below this, superconductivity returns.

Valla, Davis and co-workers studied a version of a cuprate known as LBCO that ceases to superconduct when just one-eighth of its electrons have been removed. Previous measurements have shown that in this material the electrons arrange themselves in alternating "stripes" about four atoms wide, and this somehow seems to inhibit superconductivity.

The researchers studied samples cooled to near absolute zero -- where the material is still not a superconductor -- to observe the simplest or "ground" state. This was, the researchers said, the first measurement of the electronic structure of a cuprate in which the material's superconductivity did not interfere.

Valla's group measured the energy and momentum of the electrons in the non-superconducting LBCO by photoemission spectroscopy, in which X-rays are used to knock electrons off the surface for measurement. Davis and colleagues at Cornell studied a piece of the same crystal with a specially built scanning tunneling microscope so sensitive that it can detect the arrangement of electrons in the material. They were amazed to find that in both kinds of measurements, all low-energy electronic signatures were the same in the "striped" material as in superconducting cuprates.

Valla speculated that the difference lies in the way electrons form pairs, that they might sometimes pair too strongly for superconductivity to work. Davis declined to speculate, simply saying, "The electronic structure we observe ... appears to indicate that the 'striped' state is intimately related to the superconducting state -- perhaps they are two sides of the same coin."

It will be up to theorists, he said, to revise their theories to account for these results.

The research was supported by the U.S. Department of Energy, the Office of Naval Research and Cornell.

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

More articles from Power and Electrical Engineering:

nachricht Waste from paper and pulp industry supplies raw material for development of new redox flow batteries
12.10.2017 | Johannes Gutenberg-Universität Mainz

nachricht Low-cost battery from waste graphite
11.10.2017 | Empa - Eidgenössische Materialprüfungs- und Forschungsanstalt

All articles from Power and Electrical Engineering >>>

The most recent press releases about innovation >>>

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

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Terahertz spectroscopy goes nano

20.10.2017 | Information Technology

Strange but true: Turning a material upside down can sometimes make it softer

20.10.2017 | Materials Sciences

NRL clarifies valley polarization for electronic and optoelectronic technologies

20.10.2017 | Interdisciplinary Research

VideoLinks
B2B-VideoLinks
More VideoLinks >>>