Featured Research

from universities, journals, and other organizations

Neutrons Provide Clues To High Temperature Superconductivity

Date:
April 15, 1999
Source:
Max Planck Society
Summary:
More than a dozen years after the discovery of high temperature superconductivity, the microscopic mechanism responsible for this phenomenon is still mysterious. An international group of researchers led by the Max Planck Institute of Solid State Research in Stuttgart (Germany) and Princeton University (USA) reports neutron scattering experiments providing incisive new information about the behavior of electron spins that will be crucial for models of high temperature superconductivity.

More than a dozen years after the discovery of high temperature superconductivity, the microscopic mechanism responsible for this phenomenon is still mysterious. An international group of researchers led by the Max Planck Institute of Solid State Research in Stuttgart (Germany) and Princeton University (USA) reports neutron scattering experiments providing incisive new information about the behavior of electron spins that will be crucial for models of high temperature superconductivity (Nature, April 15, 1999). Superconductivity was discovered in 1911 and occurs in many ordinary metals such as lead and aluminum at very low temperatures (below about 5 degrees above absolute zero, or about 290 degrees below room temperature). In the superconducting state, electrons can flow through the material without any resistance. Electrical currents in a superconductor therefore do not decay by heating up the material, as they would in a nonsuperconducting metal. In principle, superconductors can therefore be used to transmit currents without any losses. Despite these advantages, traditional superconductors have found few practical applications, as a lot of energy has to be invested to cool them down to the required temperatures. The discovery in 1986 of chemical compounds that superconduct at much higher temperatures has therefore caused much excitement. The current record (at ambient pressure) stands at about 135 degrees above absolute zero (or about 160 degrees below room temperature), so that much less cooling is required to initiate superconductivity. In these "high temperature" superconductors, the chemical elements copper and oxygen are arranged in a layered structure, with other elements sandwiched between the layers. The complex chemistry and materials physics of high temperature superconductors has slowed down the development of technological applications. Nevertheless, promising applications ranging from radio-frequency filters and magnetic field sensors to electrical motors are now beginning to emerge. What is missing so far is a theoretical understanding of the origin of high temperature superconductivity in the copper oxides. The theory of low temperature superconductivity in ordinary metals was developed in 1956 and is now well accepted. Electrons which normally move through the material individually and lose energy by colliding with impurities and other electrons are paired up in the superconducting state. Electrons also carry a tiny magnetic moment (the so-called "spin"), but the spins of two electrons in a pair are oriented in an antiparallel fashion so that the pair is actually nonmagnetic. Such electron pairs, which can move through the material without dissipating energy, also exist in high temperature superconductors. The "glue" that keeps the pairs together in the copper oxides, however, is still mysterious. Most theorists now agree that the mechanism that leads to pairing in traditional superconductors, vibrations of the atomic nuclei, cannot be responsible for high temperature superconductivity. The experiment reported in Nature provides important clues to what may take the place of atomic vibrations in pairing up the electrons. The researchers used neutrons produced in research reactors in Saclay and Grenoble, France, to excite and detect fluctuations of the electron spins in a particular high temperature superconductor of chemical formula Bi2Sr2CaCu2O8. Since neutrons carry a magnetic moment and penetrate deeply into most materials, neutron scattering is a powerful probe of magnetism in solids. The neutron scattering experiment revealed a "collective" spin excitation in Bi2Sr2CaCu2O8, that is, in the superconducting state all of the electron spins suddenly begin to move in unison. Such collective spin excitations are normally found only in magnetically ordered materials such as iron (see figure). The fact that similar excitations also exist in high temperature superconductors points towards a magnetic pairing mechanism. Efforts to develop a theoretical description of such a mechanism are still controversial, but the neutron experiments are an important step forward. It is to be hoped that a comprehensive theory of high temperature superconductivity will lead to the design of materials which superconduct at even higher temperatures, perhaps eventually room temperature.


Story Source:

The above story is based on materials provided by Max Planck Society. Note: Materials may be edited for content and length.


Cite This Page:

Max Planck Society. "Neutrons Provide Clues To High Temperature Superconductivity." ScienceDaily. ScienceDaily, 15 April 1999. <www.sciencedaily.com/releases/1999/04/990415065141.htm>.
Max Planck Society. (1999, April 15). Neutrons Provide Clues To High Temperature Superconductivity. ScienceDaily. Retrieved September 30, 2014 from www.sciencedaily.com/releases/1999/04/990415065141.htm
Max Planck Society. "Neutrons Provide Clues To High Temperature Superconductivity." ScienceDaily. www.sciencedaily.com/releases/1999/04/990415065141.htm (accessed September 30, 2014).

Share This



More Matter & Energy News

Tuesday, September 30, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Argentina's Tax Evaders Detected, Hunted Down by Drones

Argentina's Tax Evaders Detected, Hunted Down by Drones

AFP (Sep. 30, 2014) Argentina doesn't only have Lionel Messi the footballer, it has now also acquired "Mesi" the drone system which monitors undeclared mansions, swimming pools and soy fields to curb tax evasion in the country. Duration: 01:18 Video provided by AFP
Powered by NewsLook.com
Do Video Games Trump Brain Training For Cognitive Boosts?

Do Video Games Trump Brain Training For Cognitive Boosts?

Newsy (Sep. 29, 2014) More and more studies are showing positive benefits to playing video games, but the jury is still out on brain training programs. Video provided by Newsy
Powered by NewsLook.com
CERN Celebrates 60 Years of Science

CERN Celebrates 60 Years of Science

Reuters - Business Video Online (Sep. 29, 2014) CERN, the European Organisation for Nuclear Research, celebrates 60 years of bringing nations together through science. As Joanna Partridge reports from inside the famous science centre it's also planning to turn the Large Hadron Collider particle accelerator back on after an upgrade. Video provided by Reuters
Powered by NewsLook.com
This 'Invisibility Cloak' Is Simpler Than Most

This 'Invisibility Cloak' Is Simpler Than Most

Newsy (Sep. 28, 2014) Researchers from the University of Rochester have created a type of invisibility cloak with simple focal lenses. Video provided by Newsy
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