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 Researchers discover link between magnetic field strength and temperature
21.08.2018 | American Institute of Physics

nachricht Smallest transistor worldwide switches current with a single atom in solid electrolyte
17.08.2018 | Karlsruher Institut für Technologie (KIT)

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: It’s All in the Mix: Jülich Researchers are Developing Fast-Charging Solid-State Batteries

There are currently great hopes for solid-state batteries. They contain no liquid parts that could leak or catch fire. For this reason, they do not require cooling and are considered to be much safer, more reliable, and longer lasting than traditional lithium-ion batteries. Jülich scientists have now introduced a new concept that allows currents up to ten times greater during charging and discharging than previously described in the literature. The improvement was achieved by a “clever” choice of materials with a focus on consistently good compatibility. All components were made from phosphate compounds, which are well matched both chemically and mechanically.

The low current is considered one of the biggest hurdles in the development of solid-state batteries. It is the reason why the batteries take a relatively long...

Im Focus: Color effects from transparent 3D-printed nanostructures

New design tool automatically creates nanostructure 3D-print templates for user-given colors
Scientists present work at prestigious SIGGRAPH conference

Most of the objects we see are colored by pigments, but using pigments has disadvantages: such colors can fade, industrial pigments are often toxic, and...

Im Focus: Unraveling the nature of 'whistlers' from space in the lab

A new study sheds light on how ultralow frequency radio waves and plasmas interact

Scientists at the University of California, Los Angeles present new research on a curious cosmic phenomenon known as "whistlers" -- very low frequency packets...

Im Focus: New interactive machine learning tool makes car designs more aerodynamic

Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.

When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...

Im Focus: Robots as 'pump attendants': TU Graz develops robot-controlled rapid charging system for e-vehicles

Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.

Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

LaserForum 2018 deals with 3D production of components

17.08.2018 | Event News

Within reach of the Universe

08.08.2018 | Event News

A journey through the history of microscopy – new exhibition opens at the MDC

27.07.2018 | Event News

 
Latest News

A paper battery powered by bacteria

21.08.2018 | Power and Electrical Engineering

Protein interaction helps Yersinia cause disease

21.08.2018 | Life Sciences

Biosensor allows real-time oxygen monitoring for 'organs-on-a-chip'

21.08.2018 | Medical Engineering

VideoLinks
Science & Research
Overview of more VideoLinks >>>