Featured Research

from universities, journals, and other organizations

Fluid 'Stripes' May Be Essential For High-temperature Superconductivity

Date:
June 4, 2004
Source:
Brookhaven National Laboratory
Summary:
Scientists at the U.S. Department of Energy's Brookhaven National Laboratory, in collaboration with researchers at the Rutherford Appleton Laboratory in the United Kingdom and Tohoku University in Japan, have discovered evidence supporting a possible mechanism for high-temperature superconductivity that had previously appeared incompatible with certain experimental observations.

UPTON, NY -- Scientists at the U.S. Department of Energy's Brookhaven National Laboratory, in collaboration with researchers at the Rutherford Appleton Laboratory in the United Kingdom and Tohoku University in Japan, have discovered evidence supporting a possible mechanism for high-temperature superconductivity that had previously appeared incompatible with certain experimental observations. The finding, which hinges paradoxically on what the scientists observed in a particular material that loses its superconductivity for a special composition of atoms, is bound to be controversial in this dynamic field. It is described in the June 3, 2004 issue of Nature.

"We definitely expect some controversy," said Brookhaven physicist John Tranquada, lead author on the paper, "because our data suggest that some popular ideas are wrong."

The scientists were studying a material composed of lanthanum, barium, copper and oxygen (LBCO). The parent compound, LCO, which lacks the barium, is not a superconductor (a material through which current moves with no resistance), nor even a regular conductor. This is because the repulsive forces between the like-charged electrons on adjacent copper atoms keep them separated and somewhat locked into position -- unable to carry a current. In this arrangement, the electrons on adjacent atoms align themselves so that their spins alternate in an up, down, up, down fashion, producing a condition scientists call antiferromagnetism.

When barium is substituted for some of the lanthanum atoms, however, the material starts to exhibit superconductivity. Barium has one fewer electron than lanthanum to contribute to atomic interactions, so adding barium adds electron "holes," or the absence of electrons, to the system. The more barium, the more holes, and the greater the superconductivity -- until the composition reaches a point where there is exactly one barium atom for every eight copper atoms: Then the superconductivity disappears. Above this point, as more "holes" (barium atoms) are added, the superconductivity reappears but then gradually declines.

From previous experiments, the scientists know that, at the point where the superconductivity disappears, narrow antiferromagnetic regions of the material are separated by regions with holes, forming alternating "stripes." Other scientists have proposed that such stripes might be important for superconductivity if the stripes could flow -- that is, if the stripes made of electron holes could wiggle through the crystal lattice. But trying to study these materials in their superconducting form is "like looking at the stripes on a waving flag from a great distance using soda bottles as binoculars," Tranquada said. Because everything is fluid, the pattern is hard to identify.

But when the scientists measured the magnetic excitations of the static, non-superconducting form of LBCO (the one with the 1:8 ratio), which they know has stripes, they came upon a surprise. The pattern of magnetic excitations -- how much energy it takes to flip the spins of the electrons -- looked remarkably similar to that observed in another well-known copper-oxide superconductor made with yttrium in place of lanthanum (YBCO). Some scientists had predicted such a pattern would not be possible for a material with stripes.

The finding that the striped material produces magnetic excitations so similar to the well-known superconductor suggests that the stripes might very well be there all along when the materials act as superconductors, not just in the static case of LBCO 1:8.

"The magnetic excitations are almost like fingerprints that say these things must be similar in some way," Tranquada said. "In fact, our results support the concept that stripe correlations might be essential to high-transition-temperature superconductivity."

The scientists have not yet demonstrated experimentally how the stripes contribute to the high-temperature superconductivity, but Tranquada says the quest for such evidence is likely to generate great interest in the field.

For this study, the crystals of LBCO were grown at Brookhaven Lab and analyzed using neutron scattering at the ISIS facility at the Rutherford Appleton Lab. By scattering a beam of neutrons off the crystalline sample, the scientists can measure the positions of the atoms, the alignment of the electron spins, the energy it takes to "flip" a spin, and how the spins interact.

"Without the unique capabilities of the MAPS experiment at the ISIS neutron source, these observations would have been impossible," said Toby Perring, project leader of the MAPS experiment and a co-author on the Nature paper. "The 100 million detector pixels give us an unmatched clarity of vision into the interior world of superconductors."

###

The research was funded by the Office of Basic Energy Sciences within the U.S. Department of Energy's Office of Science, the U.S.-Japan Cooperative Research Program on Neutron Scattering, and the Japanese Ministry of Education, Culture, Sports, Science, and Technology.

One of the ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. Brookhaven is operated and managed for DOE's Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization. Visit Brookhaven Lab's electronic newsroom for links, news archives, graphics, and more: http://www.bnl.gov/newsroom.


Story Source:

The above story is based on materials provided by Brookhaven National Laboratory. Note: Materials may be edited for content and length.


Cite This Page:

Brookhaven National Laboratory. "Fluid 'Stripes' May Be Essential For High-temperature Superconductivity." ScienceDaily. ScienceDaily, 4 June 2004. <www.sciencedaily.com/releases/2004/06/040603065833.htm>.
Brookhaven National Laboratory. (2004, June 4). Fluid 'Stripes' May Be Essential For High-temperature Superconductivity. ScienceDaily. Retrieved October 1, 2014 from www.sciencedaily.com/releases/2004/06/040603065833.htm
Brookhaven National Laboratory. "Fluid 'Stripes' May Be Essential For High-temperature Superconductivity." ScienceDaily. www.sciencedaily.com/releases/2004/06/040603065833.htm (accessed October 1, 2014).

Share This



More Matter & Energy News

Wednesday, October 1, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Japan Looks To Faster Future As Bullet Train Turns 50

Japan Looks To Faster Future As Bullet Train Turns 50

Newsy (Oct. 1, 2014) Japan's bullet train turns 50 Wednesday. Here's a look at how it's changed over half a century — and the changes it's inspired globally. Video provided by Newsy
Powered by NewsLook.com
US Police Put Body Cameras to the Test

US Police Put Body Cameras to the Test

AFP (Oct. 1, 2014) Police body cameras are gradually being rolled out across the US, with interest surging after the fatal police shooting in August of an unarmed black teenager. Duration: 02:18 Video provided by AFP
Powered by NewsLook.com
Raw: Japan Celebrates 'bullet Train' Anniversary

Raw: Japan Celebrates 'bullet Train' Anniversary

AP (Oct. 1, 2014) A ceremony marking 50 years since Japan launched its Shinkansen bullet train was held on Wednesday in Tokyo. The latest model can travel from Tokyo to Osaka, a distance of 319 miles, in two hours and 25 minutes. (Oct. 1) Video provided by AP
Powered by NewsLook.com
Robotic Hair Restoration

Robotic Hair Restoration

Ivanhoe (Oct. 1, 2014) A new robotic procedure is changing the way we transplant hair. The ARTAS robot leaves no linear scarring and provides more natural results. Video provided by Ivanhoe
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins