Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Imaging electron pairing in a simple magnetic superconductor

Findings and resulting theory could reveal mechanism behind zero-energy-loss current-carrying capability

In the search for understanding how some magnetic materials can be transformed to carry electric current with no energy loss, scientists at the U.S. Department of Energy's Brookhaven National Laboratory, Cornell University, and collaborators have made an important advance: Using an experimental technique they developed to measure the energy required for electrons to pair up and how that energy varies with direction, they've identified the factors needed for magnetically mediated superconductivity-as well as those that aren't.

"Our measurements distinguish energy levels as small as one ten-thousandth the energy of a single photon of light-an unprecedented level of precision for electronic matter visualization," said Séamus Davis, Senior Physicist at Brookhaven the J.G. White Distinguished Professor of Physical Sciences at Cornell, who led the research described in Nature Physics. "This precision was essential to writing down the mathematical equations of a theory that should help us discover the mechanism of magnetic superconductivity, and make it possible to search for or design materials for zero-loss energy applications."

The material Davis and his collaborators studied was discovered in part by Brookhaven physicist Cedomir Petrovic ten years ago, when he was a graduate student working at the National High Magnetic Field Laboratory. It's a compound of cerium, cobalt, and indium that many believe may be the simplest form of an unconventional superconductor-one that doesn't rely on vibrations of its crystal lattice to pair up current-carrying electrons. Unlike conventional superconductors employing that mechanism, which must be chilled to near absolute zero (-273 degrees Celsius) to operate, many unconventional superconductors operate at higher temperatures-as high as -130°C. Figuring out what makes electrons pair in these so-called high-temperature superconductors could one day lead to room-temperature varieties that would transform our energy landscape.

The main benefit of CeCoIn5, which has a chilly operating temperature (-271°C), is that it can act as the "hydrogen atom" of magnetically mediated superconductors, Davis said-a test bed for developing theoretical descriptions of magnetic superconductivity the way hydrogen, the simplest atom, helped scientists derive mathematical equations for the quantum mechanical rules by which all atoms operate.

"Scientists have thought this material might be 'the one,' a compound that would give us access to the fundamentals of magnetic superconductivity in a controllable way," Davis said. "But we didn't have the tools to directly study the process of electron pairing. This paper announces the successful invention of the techniques and the first examination of how that material works to form a magnetic superconductor."

The method, called quasiparticle scattering interference, uses a spectroscopic imaging scanning tunneling microscope designed by Davis to measure the strength of the "glue" holding electron pairs together as a function of the direction in which they are moving. If magnetism is the true source of electron pairing, the scientists should find a specific directional dependence in the strength of the glue, because magnetism is highly directional (think of the north and south poles on a typical bar magnet). Electron pairs moving in one direction should be very strongly bound while in other directions the pairing should be non-existent, Davis explained.

To search for this effect, Davis group members Milan P. Allan and Freek Massee used samples of the material made by Petrovic. "To make these experiments work, you have to get the materials exactly right," Davis said. "Petrovic synthesized atomically perfect samples."

With the samples held in the microscope far below their superconducting temperature, the scientists sent in bursts of energy to break apart the electron pairs. The amount of energy it takes to break up the pair is known as the superconducting energy gap.

"When the pairs break up, the two electrons move off in opposite directions. When they hit an impurity in the sample, that makes a kind of interference, like waves scattering off a lighthouse," Davis explained. "We make movies of those standing waves. The interference patterns tell us the direction the electron was traveling for each energy level we send into the system, and how much energy it takes to break apart the pairs for each direction of travel."

The instrument uses the finest energy resolution for electronic matter visualization of any experiment ever achieved to tease out incredibly small energy differences-increments that are a tiny fraction of the energy of a single photon of light. The precision measurements revealed the directional dependence the scientists were looking for in the superconducting energy gap.

"Our job as scientists is to write down an equation and solve it to give a quantitative description of what we observed, and then use it to describe how magnetic superconductivity works and make and test predictions about how certain new materials will behave," Davis said.

One of the most important things the theory will do, he explained, will be to help separate the "epiphenomena," or side effects, from the true phenomena-the fundamental elements essential for superconductivity.

"Once you know the fundamental issues, which is what these studies reveal, it greatly enhances the probability of discovering a new material with the correct characteristics because you know what you are looking for-and you know what to avoid. We are very enthusiastic that we will be able to provide the theoretical tools for identifying the stuff to avoid when trying to make magnetic superconductors with improved properties," Davis said.

Davis and Petrovic worked with additional collaborators at Brookhaven, Cornell, and St. Andrews. The research was funded by the DOE Office of Science and the U.K. Engineering and Physical Sciences Research Council.

DOE's Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit

Related links

Scientific Paper: "Imaging Cooper pairing of heavy fermions in CeCoIn5"

Note that this link to the paper will not be active until after the embargo lifts on Sunday, July 14, 2013, 1 p.m. U.S. Eastern Time. Prior to that reporters can request a copy of the paper from the Nature press office.

One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry, and government researchers. Brookhaven is operated and managed for DOE's Office of Science by Brookhaven Science Associates, a limited-liability company founded by the Research Foundation of the State University of New York, for and on behalf of Stony Brook University, the largest academic user of Laboratory facilities; and Battelle Memorial Institute, a nonprofit, applied science and technology organization. Visit Brookhaven Lab's electronic newsroom for links, news archives, graphics, and more or follow Brookhaven Lab on Twitter.

Karen McNulty Walsh | EurekAlert!
Further information:

More articles from Physics and Astronomy:

nachricht Scientists discover particles similar to Majorana fermions
25.10.2016 | Chinese Academy of Sciences Headquarters

nachricht Light-driven atomic rotations excite magnetic waves
24.10.2016 | Max-Planck-Institut für Struktur und Dynamik der Materie

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Etching Microstructures with Lasers

Ultrafast lasers have introduced new possibilities in engraving ultrafine structures, and scientists are now also investigating how to use them to etch microstructures into thin glass. There are possible applications in analytics (lab on a chip) and especially in electronics and the consumer sector, where great interest has been shown.

This new method was born of a surprising phenomenon: irradiating glass in a particular way with an ultrafast laser has the effect of making the glass up to a...

Im Focus: Light-driven atomic rotations excite magnetic waves

Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion

Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how...

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...

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

Ice shelf vibrations cause unusual waves in Antarctic atmosphere

25.10.2016 | Earth Sciences

Fluorescent holography: Upending the world of biological imaging

25.10.2016 | Power and Electrical Engineering

Etching Microstructures with Lasers

25.10.2016 | Process Engineering

More VideoLinks >>>