Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New wrinkle in the mystery of high-Tc superconductors

17.03.2006


In the twenty years since the discovery of high-temperature (Tc) superconductors, scientists have been trying to understand the mechanism by which electrons pair up and move coherently to carry electrical current with no resistance. "We are still at the beginning," says Tonica Valla, a physicist at the U.S. Department of Energy’s Brookhaven National Laboratory, who will give a talk on his group’s latest results at the American Physical Society meeting in Baltimore, Maryland on Thursday, March 16, 2006. "If anything," he adds, "it looks like the story is getting more complicated."


In 1999, Valla’s group was the first to observe a "kink" in the energy level of electrons in high-Tc superconductors just as they went through the transition temperature from their normal to superconducting state. The kink was the first clue to explaining what the mechanism of electron pairing might be.

"The kink gave us the hope that we could identify the interaction that was responsible for the electron pairing," said Valla. Some groups hold that the mechanism is the same as in conventional superconductors -- that is, that phonons, or vibrations in the crystal lattice, are responsible for electron pairing. Other scientists believe that changes in the spin alignment, or magnetic polarity, of adjacent electrons -- known as magnons -- are responsible. "The problem is that there are both phonons and magnons in the crystal with the energy where we see the kink, so it is still not clear," Valla says.

The latest wrinkle uncovered by Valla’s group is the observation of similar energy scales and gaps in a material that is not a superconductor. The material is a special form of a compound made of lanthanum, barium, copper, and oxygen, where there is exactly one barium atom for every eight copper atoms. With less or more barium, the material acts as a high-Tc superconductor (in fact, this was the very first high-Tc superconductor discovered). But at the 1:8 ratio, the material momentarily loses its superconductivity.



"The fact that this system, which is not a superconductor, has similar properties to the superconducting system is not helping to solve the mystery," Valla says. But then he notes that 20 years since the discovery of high-Tc superconductors is still not that long. "For conventional superconductors," he says, "it took about 50 years to come up with a good explanation for the behavior."

Valla’s talk is part of a session on the use of angle-resolved photoemission spectroscopy in the study of high-Tc superconductors. It will include a discussion of advances in this technique. His group uses bright beams of ultraviolet light at the National Synchrotron Light Source, one of Brookhaven Lab’s premiere research facilities, to emit electrons from the samples they are studying. Using high-resolution spectrometers, the scientists measure the energy and the angle at which the electrons exit the crystal, allowing them to reconstruct the electrons’ state while in the crystal -- their energy level and whether they had any interactions with phonons/magnons.

The talk will take place on Thursday, March 16, 2006 at 3:06 p.m. in Ballroom IV of the Baltimore Convention Center.

Karen McNulty Walsh | EurekAlert!
Further information:
http://www.bnl.gov

More articles from Power and Electrical Engineering:

nachricht Did you know that the wrapping of Easter eggs benefits from specialty light sources?
13.04.2017 | Heraeus Noblelight GmbH

nachricht To e-, or not to e-, the question for the exotic 'Si-III' phase of silicon
05.04.2017 | Carnegie Institution for Science

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: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

Im Focus: Quantum-physical Model System

Computer-assisted methods aid Heidelberg physicists in reproducing experiment with ultracold atoms

Two researchers at Heidelberg University have developed a model system that enables a better understanding of the processes in a quantum-physical experiment...

Im Focus: Glacier bacteria’s contribution to carbon cycling

Glaciers might seem rather inhospitable environments. However, they are home to a diverse and vibrant microbial community. It’s becoming increasingly clear that they play a bigger role in the carbon cycle than previously thought.

A new study, now published in the journal Nature Geoscience, shows how microbial communities in melting glaciers contribute to the Earth’s carbon cycle, a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

New quantum liquid crystals may play role in future of computers

21.04.2017 | Physics and Astronomy

A promising target for kidney fibrosis

21.04.2017 | Health and Medicine

Light rays from a supernova bent by the curvature of space-time around a galaxy

21.04.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>