Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

‘Broken Symmetry’ Discovery in High-Temperature Superconductors Opens New Research Path

19.07.2010
In a major step toward understanding the mysterious “pseudogap” state in high-temperature cuprate superconductors, a team of Cornell, Binghamton University and Brookhaven National Laboratory scientists have found a “broken symmetry,” where electrons act like molecules in a liquid crystal: Electrons between copper and oxygen atoms arrange themselves differently “north-south” than “east-west.”

This simple discovery opens a door to new research that could lead to room-temperature superconductors.

“Cornell has the world’s best, if not the universe’s best scanning tunneling microscope (STM) facility; combining that with a new theoretical idea enabled this discovery,” said Eun-Ah Kim, assistant professor of physics at Cornell and corresponding author of a report published July 15 in the journal Nature.

“We know if you identify the broken symmetries, you are close to understanding how a material works,” said J.C. Séamus Davis, Cornell’s J.D. White Distinguished Professor of Physical Sciences and director of the Center for Emergent Superconductivity at Brookhaven National Laboratory. He said the discovery is analogous to learning that a key to controlling liquid crystals (found in the LCD displays in watches, calculators and computer monitors) was that the molecules can arrange into an asymmetrical state.

Broken symmetries are seen in many materials when they undergo a “phase transition” like that of water freezing into ice, or liquid crystals becoming opaque. A material going into a superconducting state – conducting electricity with zero resistance – is another kind of phase transition.

Superconductivity was first discovered in pure metals cooled very close to absolute zero (-273 degrees Celsius). Ceramic materials called cuprates superconduct at temperatures as “high” as 150 Kelvins (degrees above absolute zero). Cuprates are made up of copper oxide layers alternating with layers of other elements. Each copper oxide layer is a checkerboard sheet formed by repeating an L-shaped unit of one copper and two oxygens, with one oxygen atom to the “north” and the other to the “east” of each copper. The presence of other elements between the copper oxide sheets nudges electrons in the copper oxide sheet around and, at the right combinations of temperature and chemical content, creates a condition for superconductivity.

Davis and his experimental group study these materials using an exceptionally precise STM that can map the location of atoms and energy levels of the electrons around them. In the superconducting phase, an “energy gap” appears – electrons that ought to be in certain energy levels associated with atoms disappear to form “Cooper pairs” that travel without resistance. But above the superconducting temperature there is a range where the energy gap is still seen, but superconductivity is not.

This “pseudogap” phase may extend all the way to room temperature in some materials, so learning to overcome its limitations could lead to room-temperature superconductors.

The broken symmetry has been present but hidden in existing data from STM experiments including ones from the Davis group, said Kim, who, with colleagues at Cornell and Binghamton, proposed a new theoretical perspective and mathematical procedure to reveal the broken symmetry from the data.

Previously, Kim said, theorists had focused only on the arrangement of the copper atoms, and experimentalists had been averaging signals over all the oxygen atoms in a sample, rather than comparing “east-west” and “north-south” signals.

Kim said the finding presents “an opportunity for a whole new stage of research. We have a map of this broken symmetry, now we can experimentally study how it affects superconductivity. Further, the importance of oxygen sites for the broken symmetry points to a theoretical model that may explain the mechanism of pseudogap and high Tc [critical temperature] superconductivity.“

The research was supported primarily by the National Science Foundation and Department of Energy. Additional funding was provided by the U.S. Army Research Office and University of British Columbia.

Text written by Bill Steele, Cornell University Chronicle

Blaine Friedlander | Newswise Science News
Further information:
http://www.cornell.edu

More articles from Power and Electrical Engineering:

nachricht A big nano boost for solar cells
18.01.2017 | Kyoto University and Osaka Gas effort doubles current efficiencies

nachricht Multiregional brain on a chip
16.01.2017 | Harvard John A. Paulson School of Engineering and Applied Sciences

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: 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 >>>