ZPE_Logo
  
Search        
  Create an account Home  ·  Topics  ·  Downloads  ·  Your Account  ·  Submit News  ·  Top 10  
Mission Statement

Modules
· Home
· Forum
· LATEST COMMENTS
· Special Sections
· SUPPORT ZPEnergy
· Advertising
· AvantGo
· Books
· Downloads
· Events
· Feedback
· Link to us
· Private Messages
· Search
· Stories Archive
· Submit News
· Surveys
· Top 10
· Topics
· Web Links
· Your Account

Who's Online
There are currently, 146 guest(s) and 1 member(s) that are online.

You are Anonymous user. You can register for free by clicking here

Events
  • (June 9, 2021 - June 11, 2021) ICCF-23 online

  • Hot Links
    Aetherometry

    American Antigravity

    AESOP Institute

    Closeminded Science

    EarthTech

    Innoplaza

    Integrity Research Institute

    New Energy Movement

    New Energy Times

    The Orion Proj.

    Panacea-BOCAF

    QVac_Eng

    RexResearch

    Science Hobbyist

    Tom Bearden's Page

    USPTO

    Want to Know

    Other Info-Sources
    NE News Sites
    AER_Network
    Alternative Energy News
    E-Cat World
    NexusNewsfeed ZPE
    FringeEnergy News
    NE Discussion Groups
    Energetic Forum
    Energy21 YT Channel
    EMediaPress
    Energy Science Forum
    Free_Energy FB Group
    The KeelyNet Blog
    OverUnity
    Sarfatti_Physics
    Tesla Science Foundation (FB)
    Vortex (old Interact)
    Magazine Sites
    Electrifying Times (FB)
    ExtraOrdinary Technology
    IE Magazine
    New Energy Times

    Interesting Links

    Click Here for the DISCLOSURE PROJECT
    SciTech Daily Review
    NEXUS Magazine
    Find Jobs

    Imaging 'Gridlock' in High-temperature Superconductors
    Posted on Monday, March 05, 2007 @ 21:32:14 MST by vlad

    Science Superconductivity -- the conduction of electricity with zero resistance -- sometimes can, it seems, become stalled by a form of electronic "gridlock."

    A possible explanation why is offered by new research at Cornell University. The research, reported March 5 at the annual meeting of the American Physical Society in Denver, concerns certain copper oxides -- known as cuprates -- that can become high-temperature superconductors, but also can, in a slightly different configuration, become stalled by the "gridlock."



    Understanding how and why that transition takes place is a crucial question for cuprate superconductivity research because, if it did not, the maximum temperatures for superconductivity could conceivably be much higher.

    Scanning lightly hole-doped cuprate crystals with a highly precise scanning tunneling microscope (STM) has revealed strong variations in electronic structure with some copper-oxygen-copper (Cu-O-Cu) bonds distributed randomly through the crystal apparently exhibiting "holes" where electrons are missing. The researchers also found larger rectangular regions with missing electrons that were spaced four units of the crystal lattice apart, and may represent the first direct observation of long-sought electronic "stripes" in cuprates.

    Yuhki Kohsaka, a postdoctoral researcher working with J.C. Sťamus Davis, Cornell professor of physics, reported on the research. A paper on the work by Kohsaka, Davis and others is the cover story in the March 9 edition of Science.

    The superconducting phenomenon was first discovered in metals cooled to less than about 4 degrees Celsius above absolute zero (-273 degrees Celsius or -459 degrees Fahrenheit) with liquid helium. Recently, superconductivity at much higher temperatures was discovered in cuprates. Pure cuprates are normally insulators, but when doped with small numbers of other atoms they become superconductors at temperatures as high as 148 degrees above absolute zero (-125 Celsius). The impurities break up the orderly crystal structure and create "holes" where electrons ought to be.

    At 16 percent hole-density the cuprates display the highest temperature superconductivity of any known material. But if hole-density is reduced by just a few percent, the superconductivity vanishes precipitously and the materials become highly resistant.

    Previous experiments have given evidence that long-range patterns of "stripes" of alternating high- and low-charge density, spaced four units of the crystal lattice apart, exist in doped cuprates, but no imaging technique had been able to detect them.

    An STM uses an atom-sized tip that moves in atom-sized steps across a surface. When a voltage is applied between the tip and the surface, a small current known as a "tunneling current" flows between them. By adjusting the height of the tip above the surface to produce a constant current, researchers can see the shapes of individual atoms. And with the exceptional precision of the STM operated by Davis and colleagues at Cornell, the spatial arrangement of electronic states can be imaged. However, the researchers explain in their paper, this technique has serious limitations in imaging the distribution of holes.

    The innovation in the new research, based on a suggestion by Nobel laureate Philip W. Anderson, professor emeritus at Princeton University, is to compare current flow in opposite directions at each point in the scan. In simple terms, at regions of the crystal containing fewer electrons (more holes), more electrons can flow down from the tip into these voids than up. The process is called TA-imaging, for tunneling asymmetry.

    The Cornell researchers studied cuprate crystals in which about 10 percent of the electrons in the crystal lattice were removed and replaced by holes. The researchers imaged two cuprates with very different chemistry, crystal structure and doping characteristics and found virtually identical results, which they attribute entirely to the spatial arrangement of electrons in the crystal. The areas where TA-imaging suggests that there are holes appear to be centered on oxygen atoms within the Cu-O-Cu bond. This is what has long been expected based on X-ray scattering studies. But "the big surprise," Davis said, "is that when you map this stuff for large distances across the surface no orderly patterns are observed. We had no picture of this before." Perhaps even more exciting, he said, is the discovery that over larger areas the holes do appear to be arranged in patterns that are rectangular and exactly four crystal lattice spaces wide. These so called "nanostripes" are aligned with the crystal lattice but otherwise distributed at random.

    "It's plausible that when you increase the number of holes these 'nanostripes' will combine into the orderly stripes seen in other experiments," Davis said. A next step, he said, is to use TA-imaging on more heavily doped materials that exhibit such stripes to see if they are made up of these oxygen-centered holes. But the key challenge, he added, is to understand precisely how the process of hole localization into the patterns seen here suppresses superconductivity.

    Source: Cornell University

    Story from: http://www.physorg.com/news92334606.html

     
    Login
    Nickname

    Password

    Security Code: Security Code
    Type Security Code

    Don't have an account yet? You can create one. As a registered user you have some advantages like theme manager, comments configuration and post comments with your name.

    Related Links
    · More about Science
    · News by vlad


    Most read story about Science:
    100 miles on 4 ounces of water?


    Article Rating
    Average Score: 0
    Votes: 0

    Please take a second and vote for this article:

    Excellent
    Very Good
    Good
    Regular
    Bad


    Options

     Printer Friendly Printer Friendly


    "Imaging 'Gridlock' in High-temperature Superconductors" | Login/Create an Account | 2 comments | Search Discussion
    The comments are owned by the poster. We aren't responsible for their content.

    No Comments Allowed for Anonymous, please register

    Looking for 'Stripes' in High-Tc superconductors (Score: 1)
    by vlad on Saturday, March 10, 2007 @ 13:20:01 MST
    (User Info | Send a Message) http://www.zpenergy.com
    In LBCO, as in all materials, negatively charged electrons repel one another. But by trying to stay as far apart as possible, each individual electron is confined to a limited space, which costs energy. To achieve a lower-energy state, the electrons arrange themselves with their spins aligned in alternating directions on adjacent atoms, a configuration known as antiferromagnetic order.

    Full story at http://www.physorg.com/news92501702.html [www.physorg.com]





     

    All logos and trademarks in this site are property of their respective owner. The comments are property of their posters, all the rest © 2002-2016 by ZPEnergy. Disclaimer: No content, on or affiliated with ZPEnergy should be construed as or relied upon as investment advice. While every effort is made to ensure that the information contained on ZPEnergy is correct, the operators of ZPEnergy make no warranties as to its accuracy. In all respects visitors should seek independent verification and investment advice.
    Keywords: ZPE, ZPF, Zero Point Energy, Zero Point Fluctuations, ZPEnergy, New Energy Technology, Small Scale Implementation, Energy Storage Technology, Space-Energy, Space Energy, Natural Potential, Investors, Investing, Vacuum Energy, Electromagnetic, Over Unity, Overunity, Over-Unity, Free Energy, Free-Energy, Ether, Aether, Cold Fusion, Cold-Fusion, Fuel Cell, Quantum Mechanics, Van der Waals, Casimir, Advanced Physics, Vibrations, Advanced Energy Conversion, Rotational Magnetics, Vortex Mechanics, Rotational Electromagnetics, Earth Electromagnetics, Gyroscopes, Gyroscopic Effects

    PHP-Nuke Copyright © 2005 by Francisco Burzi. This is free software, and you may redistribute it under the GPL. PHP-Nuke comes with absolutely no warranty, for details, see the license.