Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

French-German Group Verifies High-Temperature Superconductivity Theory Proposed by UCR Physicist

18.05.2006


Experimental results could point the way to fabricating room temperature superconductors and solving a major mystery in physics


A 1996 theory by UCR’s Chandra Varma notes that in copper oxide materials superconductivity is associated with the formation of a new state of matter in which electric current loops form spontaneously, going from copper to oxygen atoms and back to copper. Recently, a French-German team of experimental scientists directly observed the current loops. Credit: C. Varma



A French-German team of experimental scientists, led by Philippe Bourges of the Commissariat à l’Energie Atomique, France, reports that it has verified the central prediction of a theory on high-temperature superconductivity developed by Chandra Varma, distinguished professor of physics at UC Riverside. The verification ultimately could assist in the fabrication of materials that are superconducting at room temperature and help settle a contentious, international debate on the fundamental physics of superconductivity and emergent states of matter.

Varma’s initial theory, which he proposed in 1989 when he was at Bell Laboratories, stated the radical idea that high temperature superconductivity and related phenomena occur in certain materials because quantum-mechanical fluctuations in these materials increase as temperature decreases. Usually such fluctuations, which determine the properties of all matter in the universe, decrease as temperature decreases.


Varma’s theory did not explain the nature of the fluctuations; he accomplished this in a theory he proposed in 1996, while still at Bell Labs, in which he noted that in copper oxide materials, also known as cuprates, superconductivity is associated with the formation of a new state of matter in which electric current loops form spontaneously, going from copper to oxygen atoms and back to copper. His theory concluded that the quantum-mechanical fluctuations are the fluctuations of these current loops. Physicists consider these fluctuations in the current loops to be fluctuations of time.

Bourges’s group directly observed the current loops in experiments involving the diffraction of polarized neutrons. In these experiments a beam of neutrons changes direction as well as the direction of its magnetization in a manner that is closely related to the geometrical arrangement of the current loops inside the material in which the beam is made to pass.

"Currently, there is much debate among researchers working on superconductivity about what exactly happens in cuprates," said Varma, who joined UCR in 2003 and was a Bell Labs researcher from 1969 to 2001. "Further experiments of the kind by Bourges’s group should help bring a consensus in the scientific community about the fundamental physics involved in cuprates."

The results of Bourges’s experiments appear in the May 19 issue of Physical Review Letters.

"Chandra Varma has been a pioneer in the theory of high-temperature superconductivity since its discovery 20 years ago, and Bell Labs is delighted to see confirmation of his microscopic theory by the neutron scattering experiments of Bourges and coworkers," said Arthur Ramirez, director of Device Physics Research at Lucent Technologies Bell Labs. "The confirmation of this theory could become a turning point for research we and other laboratories are performing on high-temperature superconductivity."

Before Bourges’s group observed the current loops Varma predicted, an experiment performed in 2002 by a group of scientists at Argonne National Laboratory and the University of Illinois, Chicago, discovered the current loops in an indirect way by using an experimental technique Varma suggested in 2000.

"The fact that two experiments came to the same conclusion with different techniques and in different cuprate compounds lends great confidence in the results," said Harry Tom, chair of the Department of Physics at UCR. "A microscopic theory of high temperature superconductivity might also suggest ways of fabricating room temperature superconductors, possibly with materials more amenable to industrial fabrication than the cuprates."

Superconductors are materials that conduct electricity with near-zero resistance below a specific temperature, known as the critical temperature. Superconductors typically find use in electric power transformers and magnetic resonance imaging machines. Conventional metallic superconductors must be cooled below -424 F to become superconducting.

High-temperature superconductors, which are almost always some type of cuprate ceramic doped with a variety of elements, conduct electricity with near-zero resistance at temperatures as high as -226 F.

High-temperature superconductivity in compounds of copper, oxygen and other elements were discovered in 1986 by Swiss scientists, Georg Bednorz and Alex Müller. Both scientists were awarded the 1987 Nobel Prize in physics "for their important break-through in the discovery of superconductivity in ceramic materials."

"While our results are exciting, our specific approach needs to be checked by another neutron group," said Bourges. "My group plans to design refined experiments to improve the data and verify the theory in more detail."

Iqbal Pittalwala | EurekAlert!
Further information:
http://www.ucr.edu

More articles from Physics and Astronomy:

nachricht Molecule flash mob
19.01.2017 | Technische Universität Wien

nachricht Magnetic moment of a single antiproton determined with greatest precision ever
19.01.2017 | Johannes Gutenberg-Universität Mainz

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: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

New Study Will Help Find the Best Locations for Thermal Power Stations in Iceland

19.01.2017 | Earth Sciences

Not of Divided Mind

19.01.2017 | Life Sciences

Molecule flash mob

19.01.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>