Nanotechnology Now

Our NanoNews Digest Sponsors

Heifer International

Wikipedia Affiliate Button

Home > Press > 'Long-awaited explanation' for mysterious effects in high-temperature superconductors: 2 orders for electrons

At each copper atom (grey balls) there is a quadrupole moment. All together, these form a kind of chessboard pattern, whereby the individual squares of the chessboard differ in the orientation of the positively and negatively charged areas (green: positive areas left and right; grey: positive areas top and bottom). At the boundaries between green and grey surfaces, the signs change. Copper atoms close to the boundary have a smaller quadrupole moment than copper atoms in the middle of the areas.

© Konstantin Efetov und Hendrik Meier (Institut für Theoretische Physik III)
At each copper atom (grey balls) there is a quadrupole moment. All together, these form a kind of chessboard pattern, whereby the individual squares of the chessboard differ in the orientation of the positively and negatively charged areas (green: positive areas left and right; grey: positive areas top and bottom). At the boundaries between green and grey surfaces, the signs change. Copper atoms close to the boundary have a smaller quadrupole moment than copper atoms in the middle of the areas.

© Konstantin Efetov und Hendrik Meier (Institut für Theoretische Physik III)

Abstract:
A German-French research team has constructed a new model that explains how the so-called pseudogap state forms in high-temperature superconductors. The calculations predict two coexisting electron orders. Below a certain temperature, superconductors lose their electrical resistance and can conduct electricity without loss. "It is not to be excluded that the new pseudogap theory also provides the long-awaited explanation for why, in contrast to conventional metallic superconductors, certain ceramic copper oxide bonds lose their electrical resistance at such unusually high temperatures", say Prof. Dr. Konstantin Efetov and Dr. Hendrik Meier of the Chair of Theoretical Solid State Physics at the Ruhr-Universität Bochum. They obtained the findings in close cooperation with Dr. Catherine Pépin from the Institute for Theoretical Physics in Saclay near Paris. The team reports in the journal Nature Physics.

'Long-awaited explanation' for mysterious effects in high-temperature superconductors: 2 orders for electrons

Bochum, Germany | Posted on June 8th, 2013

Transition temperature much higher in ceramic than in metallic superconductors

Superconductivity only occurs at very low temperatures below the so-called transition temperature. In metallic superconductors, this is close to the absolute zero point of 0 Kelvin, which corresponds to about -273 degrees Celsius. However, crystalline ceramic materials can be superconductive at temperatures up to 138 Kelvin. For 25 years, researchers puzzled over the physical bases of this high-temperature superconductivity.

Pseudogap: energy gap above the transition temperature

In the superconducting state, electrons travel in so-called Cooper pairs through the crystal lattice of a material. In order to break up a Cooper pair so that two free electrons are created, a certain amount of energy is needed. This difference in the energy of the Cooper electrons and the so-called free electrons is called an energy gap. In cuprate superconductors, compounds based on copper oxide bonds, a similar energy gap also occurs under certain circumstances above the transition temperature - the pseudogap. Characteristically the pseudogap is only perceived by electrons with certain velocity directions. The model constructed by the German-French team now allows new insights into the physical inside of the pseudogap state.

Two competing electron orders in the pseudogap state

According to the model, the pseudogap state simultaneously contains two electron orders: d-wave superconductivity, in which the electrons of a Cooper pair revolve around each other in a cloverleaf shape, and a quadrupole density wave. The latter is a special electrostatic structure in which every copper atom in the two-dimensional crystal lattice has a quadrupole moment, i.e. two opposite regions of negative charge, and two opposite regions of positive charge. d-wave superconductivity and quadrupole density wave compete with each other in the pseudogap state. Due to thermal fluctuations, neither of the two systems can assert itself. However, if the system is cooled down, the thermal fluctuations become weaker and one of the two systems prevails: superconductivity. The critical temperature at which this occurs can, in the model, be considerably higher than the transition temperature of conventional metallic superconductors. The model could thus explain why the transition temperature in the ceramic superconductors is so much higher.

Cuprates

High-temperature copper oxide superconductors are also called cuprates. In addition to copper and oxygen, they can, for example, contain the elements yttrium and barium (YBa2Cu3O7). To make the material superconducting, researchers introduce "positive holes", i.e. electron holes into the crystal lattice. Through these, the electrons can "flow" in Cooper pairs. This is known as hole doping. The pseudogap state only sets in when the hole doping of the cuprate is neither too low nor too high.

Bibliographic record

K.B. Efetov, H. Meier, C. Pépin (2013): Pseudogap state near a quantum critical point, Nature Physics, DOI: 10.1038/NPHYS2641

####

For more information, please click here

Contacts:
Konstantin Efetov

49-234-322-4844

Dr. Hendrik Meier, Chair of Theoretical Solid State Physics, Institute of Physics III at the Ruhr-Universität, 44780 Bochum, Germany,
Tel. +49/234/32-23744

Copyright © Ruhr-University Bochum

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related News Press

News and information

Researchers use sound waves to advance optical communication January 22nd, 2018

Piecework at the nano assembly line: Electric fields drive nano-motors a 100,000 times faster than previous methods January 22nd, 2018

Thanks for the memory: NIST takes a deep look at memristors January 20th, 2018

Arrowhead Pharmaceuticals Announces Pricing of Underwritten Public Offering of Common Stock January 18th, 2018

Physics

New exotic phenomena seen in photonic crystals: Researchers observe, for the first time, topological effects unique to an “open” system January 12th, 2018

Columbia engineers create artificial graphene in a nanofabricated semiconductor structure: Researchers are the first to observe the electronic structure of graphene in an engineered semiconductor; finding could lead to progress in advanced optoelectronics and data processing December 13th, 2017

Leti Develops World’s First Micro-Coolers for CERN Particle Detectors: Leti Design, Fabrication and Packaging Expertise Extends to Very Large Scientific Instruments December 11th, 2017

Inorganic-organic halide perovskites for new photovoltaic technology November 6th, 2017

Halas wins American Physical Society's Lilienfeld Prize: Rice University nanoscientist honored for pioneering research in plasmonics October 23rd, 2017

Superconductivity

Ames Laboratory, UConn discover superconductor with bounce October 25th, 2017

Nagoya physicists resolve long-standing mystery of structure-less transition: Nagoya University-led team of physicists use a synchrotron radiation X-ray source to probe a so-called 'structure-less' transition and develop a new understanding of molecular conductors August 21st, 2017

Strange electrons break the crystal symmetry of high-temperature superconductors: Brookhaven Lab scientists discover spontaneous voltage perpendicular to applied current that may help unravel the mystery of high-temperature superconductors July 27th, 2017

Discoveries

Researchers use sound waves to advance optical communication January 22nd, 2018

Piecework at the nano assembly line: Electric fields drive nano-motors a 100,000 times faster than previous methods January 22nd, 2018

Thanks for the memory: NIST takes a deep look at memristors January 20th, 2018

New Method Uses DNA, Nanoparticles and Top-Down Lithography to Make Optically Active Structures: Technique could lead to new classes of materials that can bend light, such as for those used in cloaking devices January 18th, 2018

Announcements

Researchers use sound waves to advance optical communication January 22nd, 2018

Piecework at the nano assembly line: Electric fields drive nano-motors a 100,000 times faster than previous methods January 22nd, 2018

Thanks for the memory: NIST takes a deep look at memristors January 20th, 2018

Arrowhead Pharmaceuticals Announces Pricing of Underwritten Public Offering of Common Stock January 18th, 2018

Interviews/Book Reviews/Essays/Reports/Podcasts/Journals/White papers

Researchers use sound waves to advance optical communication January 22nd, 2018

Piecework at the nano assembly line: Electric fields drive nano-motors a 100,000 times faster than previous methods January 22nd, 2018

Thanks for the memory: NIST takes a deep look at memristors January 20th, 2018

Nanowrinkles could save billions in shipping and aquaculture Surfaces inspired by carnivorous plants delay degradation by marine fouling January 17th, 2018

Energy

Ultrathin black phosphorus for solar-driven hydrogen economy: Osaka University researchers use sunlight to make hydrogen with a new nanostructured catalyst based on nanosheets of black phosphorus and bismuth vanadate January 17th, 2018

New catalyst for hydrogen production is a step toward clean fuel: Carbon-based nanocomposite with embedded metal ions yields impressive performance as catalyst for electrolysis of water to generate hydrogen January 16th, 2018

Rice U.'s one-step catalyst turns nitrates into water and air: NSF-funded NEWT Center aims for catalytic converter for nitrate-polluted water January 5th, 2018

Tweaking quantum dots powers-up double-pane solar windows: Engineered quantum dots could bring down the cost of solar electricity January 2nd, 2018

NanoNews-Digest
The latest news from around the world, FREE



  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More











ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project