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 Supersonic waves may help electronics beat the heat
18.05.2018 | DOE/Oak Ridge National Laboratory

nachricht Researchers control the properties of graphene transistors using pressure
17.05.2018 | Columbia University

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: Explanation for puzzling quantum oscillations has been found

So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics

Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...

Im Focus: Dozens of binaries from Milky Way's globular clusters could be detectable by LISA

Next-generation gravitational wave detector in space will complement LIGO on Earth

The historic first detection of gravitational waves from colliding black holes far outside our galaxy opened a new window to understanding the universe. A...

Im Focus: Entangled atoms shine in unison

A team led by Austrian experimental physicist Rainer Blatt has succeeded in characterizing the quantum entanglement of two spatially separated atoms by observing their light emission. This fundamental demonstration could lead to the development of highly sensitive optical gradiometers for the precise measurement of the gravitational field or the earth's magnetic field.

The age of quantum technology has long been heralded. Decades of research into the quantum world have led to the development of methods that make it possible...

Im Focus: Computer-Designed Customized Regenerative Heart Valves

Cardiovascular tissue engineering aims to treat heart disease with prostheses that grow and regenerate. Now, researchers from the University of Zurich, the Technical University Eindhoven and the Charité Berlin have successfully implanted regenerative heart valves, designed with the aid of computer simulations, into sheep for the first time.

Producing living tissue or organs based on human cells is one of the main research fields in regenerative medicine. Tissue engineering, which involves growing...

Im Focus: Light-induced superconductivity under high pressure

A team of scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg investigated optically-induced superconductivity in the alkali-doped fulleride K3C60under high external pressures. This study allowed, on one hand, to uniquely assess the nature of the transient state as a superconducting phase. In addition, it unveiled the possibility to induce superconductivity in K3C60 at temperatures far above the -170 degrees Celsius hypothesized previously, and rather all the way to room temperature. The paper by Cantaluppi et al has been published in Nature Physics.

Unlike ordinary metals, superconductors have the unique capability of transporting electrical currents without any loss. Nowadays, their technological...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Save the date: Forum European Neuroscience – 07-11 July 2018 in Berlin, Germany

02.05.2018 | Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

 
Latest News

Supersonic waves may help electronics beat the heat

18.05.2018 | Power and Electrical Engineering

Keeping a Close Eye on Ice Loss

18.05.2018 | Information Technology

CrowdWater: An App for Flood Research

18.05.2018 | Information Technology

VideoLinks
Science & Research
Overview of more VideoLinks >>>