Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


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

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:

More articles from Power and Electrical Engineering:

nachricht 'Super yeast' has the power to improve economics of biofuels
18.10.2016 | University of Wisconsin-Madison

nachricht Engineers reveal fabrication process for revolutionary transparent sensors
14.10.2016 | University of Wisconsin-Madison

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: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

Im Focus: New Products - Highlights of COMPAMED 2016

COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.

In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...

Im Focus: Ultra-thin ferroelectric material for next-generation electronics

'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.

Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Resolving the mystery of preeclampsia

21.10.2016 | Health and Medicine

Stanford researchers create new special-purpose computer that may someday save us billions

21.10.2016 | Information Technology

From ancient fossils to future cars

21.10.2016 | Materials Sciences

More VideoLinks >>>