Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Unusual Ceramics Could Expand Possibilities For Superconductors

26.06.2002


Ceramic materials with "split personalities" could lead to new high-temperature superconductors, according to physicists at Ohio State University and their colleagues.



Researchers here have learned that these ceramic materials, called cuprates (pronounced KOOP-rates), switch between two different kinds of superconductivity under certain circumstances.

The finding could settle a growing controversy among scientists and point the way to buckyball-like superconductivity in ceramics.


Scientists have been arguing for years whether cuprates exhibit one type of superconductivity, called d-wave, or another type, called s-wave, explained Thomas Lemberger, professor of physics.

The difference depends on how the electrons are arranged within the material, he said. Materials with s-wave behavior are more desirable, because they should have better technical properties at high temperatures. Unfortunately, most of the high-temperature cuprate compounds seem to exhibit d-wave behavior. S-wave superconductivity at high temperatures is still a possibility and is a goal of current research, Lemberger said.

For instance, buckyballs -- soccer-ball-shaped carbon molecules discovered at Bell Labs in 1991 -- exhibit s-wave superconductivity at 40° Kelvin (-388°F, -233°C), a very high temperature for superconductors. To achieve this, the Bell Labs scientists mixed, or "doped," the buckyballs with potassium.

Now Lemberger and his colleagues have found they can change the behavior of a certain class of cuprates from d-wave to s-wave if they dope it with sufficient amounts of the element cerium -- a common ingredient in glassware.

"It seems that the mechanisms for both kinds of behavior are always present in these materials," Lemberger said. "So if you do something to suppress one behavior, a cuprate will automatically switch to the other."

They report their results in two papers in a recent issue of the journal Physical Review Letters. Lemberger, doctoral student John Skinta and postdoctoral researcher Mun-Seog Kim collaborated with Tine Greibe and Michio Naito, both materials scientists at NTT Basic Research Laboratories in Japan.

Since their discovery in 1986, cuprates have puzzled scientists. Ceramics are normally insulators, but when doped with atoms of elements like lanthanum or cerium, cuprates suddenly become excellent conductors.

"That’s what’s so amazing about these materials," Lemberger said. "A cuprate could start out as a very good insulator; you could subject it to thousands of volts and it won’t conduct electricity at all. But change the composition just a little, and you’ve turned it into a superconductor. With the tiniest wisp of voltage, you’ll get huge currents flowing."

Normal doping involves adding small quantities of a secondary material in order to boost the number of mobile electrons in a sample. Over-doping, as the Ohio State physicists and their colleagues did, is roughly equivalent to over-stuffing the material with electrons -- as many electrons as the cuprate would hold while still maintaining its unique crystal structure.

They created thin films of cuprates with different amounts of cerium, and studied how the electrons arranged themselves within the material. They did this by measuring how deeply a magnetic field could penetrate each film.

As the researchers pushed the cerium content of the cuprates to the limit, the magnetic field measurements suggested that the electrons had changed their formation from d-wave to s-wave.

Scientists have speculated that cuprates could sustain s-wave superconductivity at temperatures as high as 90° Kelvin
(-298°F, -183°C). That would make the materials useful conductors for commercial electronics. If metal conductors were replaced with superconducting ceramics, devices would be more efficient, and new types of devices would become possible. And 90° Kelvin, while very cold, is still easier and less expensive to achieve than 10° Kelvin (-442°F, -263°C), the operating temperature of conventional metallic superconductors.

Lemberger said the scientific controversy surrounding the nature of superconductivity in cuprates will come to a head this summer, as researchers gather in Taiwan to debate which of the two "personalities," d-wave or s-wave, is the true state of the material.

"Our work bridges the gap between the two camps," Lemberger said. "We propose that it’s just a matter of composition."

"The question now is, how high can we push s-wave superconductivity?" he added.

The National Science Foundation funded this work.


Contact: Thomas Lemberger, (614) 292-7799; Lemberger.1@osu.edu

Written by Pam Frost Gorder, (614) 292-9475; Gorder.1@osu.edu

Thomas Lemberger | EurekAlert!
Further information:
http://prl.aps.org/
http://www.nsf.gov/

More articles from Physics and Astronomy:

nachricht What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin

nachricht Subaru Telescope helps pinpoint origin of ultra-high energy neutrino
16.07.2018 | National Institutes of Natural Sciences

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: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

Im Focus: Chemical reactions in the light of ultrashort X-ray pulses from free-electron lasers

Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.

Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

Global study of world's beaches shows threat to protected areas

19.07.2018 | Earth Sciences

New creepy, crawly search and rescue robot developed at Ben-Gurion U

19.07.2018 | Power and Electrical Engineering

Metal too 'gummy' to cut? Draw on it with a Sharpie or glue stick, science says

19.07.2018 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>