Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Superconductivity in Orbit: Scientists Find New Path to Loss-Free Electricity

17.02.2014
Brookhaven Lab researchers captured the distribution of multiple orbital electrons to help explain the emergence of superconductivity in iron-based materials

Armed with just the right atomic arrangements, superconductors allow electricity to flow without loss and radically enhance energy generation, delivery, and storage.

Scientists tweak these superconductor recipes by swapping out elements or manipulating the valence electrons in an atom’s outermost orbital shell to strike the perfect conductive balance. Most high-temperature superconductors contain atoms with only one orbital impacting performance—but what about mixing those elements with more complex configurations?

Now, researchers at the U.S. Department of Energy’s Brookhaven National Laboratory have combined atoms with multiple orbitals and precisely pinned down their electron distributions. Using advanced electron diffraction techniques, the scientists discovered that orbital fluctuations in iron-based compounds induce strongly coupled polarizations that can enhance electron pairing—the essential mechanism behind superconductivity. The study, set to publish soon in the journal Physical Review Letters, provides a breakthrough method for exploring and improving superconductivity in a wide range of new materials.

“For the first time, we obtained direct experimental evidence of the subtle changes in electron orbitals by comparing an unaltered, non-superconducting material with its doped, superconducting twin,” said Brookhaven Lab physicist and project leader Yimei Zhu.

While the effect of doping the multi-orbital barium iron arsenic—customizing its crucial outer electron count by adding cobalt—mirrors the emergence of high-temperature superconductivity in simpler systems, the mechanism itself may be entirely different.

“Now superconductor theory can incorporate proof of strong coupling between iron and arsenic in these dense electron cloud interactions,” said Brookhaven Lab physicist and study coauthor Weiguo Yin. “This unexpected discovery brings together both orbital fluctuation theory and the 50-year-old ‘excitonic’ theory for high-temperature superconductivity, opening a new frontier for condensed matter physics.”

Atomic Jungle Gym

Imagine a child playing inside a jungle gym, weaving through holes in the multicolored metal matrix in much the same way that electricity flows through materials. This particular kid happens to be wearing a powerful magnetic belt that repels the metal bars as she climbs. This causes the jungle gym’s grid-like structure to transform into an open tunnel, allowing the child to slide along effortlessly. The real bonus, however, is that this action attracts any nearby belt-wearing children, who can then blaze through that perfect path.

Flowing electricity can have a similar effect on the atomic lattices of superconductors, repelling the negatively charged valence electrons in the surrounding atoms. In the right material, that repulsion actually creates a positively charged pocket, drawing in other electrons as part of the pairing mechanism that enables the loss-free flow of current—the so-called excitonic mechanism. To design an atomic jungle gym that warps just enough to form a channel, scientists audition different combinations of elements and tweak their quantum properties.

“High-temperature copper-oxide superconductors, or cuprates, contain in effect a single orbital and lack the degree of freedom to accommodate strong enough interactions between electricity and the lattice,” Yin said. “But the barium iron arsenic we tested has multi-orbital electrons that push and pull the lattice in much more flexible and complex ways, for example by inter-orbital electron redistribution. This feature is especially promising because electricity can shift arsenic’s electron cloud much more easily than oxygen’s.”

In the case of the atomic jungle gym, this complexity demands new theoretical models and experimental data, considering that even a simple lattice made of north-south bar magnets can become a multidimensional dance of attraction and repulsion. To control the doping effects and flow of electricity, scientists needed a window into the orbital interactions.

Tracking Orbits

“Consider measuring waves crashing across the ocean’s surface,” Zhu said. “We needed to pinpoint those complex fluctuations without having the data obscured by the deep water underneath. The waves represent the all-important electrons in the outer orbital shells, which are barely distinguishable from the layers of inner electrons. For example, each barium atom alone has 56 electrons, but we’re only concerned with the two in the outermost layer.”

The Brookhaven researchers used a technique called quantitative convergent beam electron diffraction (CBED) to reveal the orbital clouds with subatomic precision. After an electron beam strikes the sample, it bounces off the charged particles to reveal the configuration of the atomic lattice, or the exact arrays of nuclei orbited by electrons. The scientists took thousands of these measurements, subtracted the inner electrons, and converted the data into probabilities—balloon-shaped areas where the valence electrons were most likely to be found.

Shape-Shifting Atoms

The researchers first examined the electron clouds of non-superconducting samples of barium iron arsenic. The CBED data revealed that the arsenic atoms—placed above and below the iron in a sandwich-like shape (see image)—exhibited little shift or polarization of valence electrons. However, when the scientists transformed the compound into a superconductor by doping it with cobalt, the electron distribution radically changed.

“Cobalt doping pushed the orbital electrons in the arsenic outward, concentrating the negative charge on the outside of the ‘sandwich' and creating a positively charged pocket closer to the central layer of iron,” Zhu said. “We created very precise electronic and atomic displacement that might actually drive the critical temperature of these superconductors higher.”

Added Yin, “What’s really exciting is that this electron polarization exhibits strong coupling. The quadrupole polarization of the iron, which indicates the orbital fluctuation, couples intimately with the arsenic dipole polarization—this mechanism may be key to the emergence of high-temperature superconductivity in these iron-based compounds. And our results may guide the design of new materials.”

This study explored the orbital fluctuations at room temperature under static conditions, but future experiments will apply dynamic diffraction methods to super-cold samples and explore alternative material compositions.

The experimental work at Brookhaven Lab was supported by DOE’s Office of Science. The materials synthesis was carried out at the Chinese Academy of Sciences’ Institute of Physics. Brookhaven Lab coauthors of the study also include Chao Ma, Lijun Wu, and Chris Homes.

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 the Office of Science website at science.energy.gov.

***

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 for the State University of New York on behalf of Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.

Visit Brookhaven Lab's electronic newsroom for links, news archives, graphics, and more at http://www.bnl.gov/newsroom. Follow Brookhaven Lab on Twitter, http://twitter.com/BrookhavenLab, and find us on Facebook, http://www.facebook.com/BrookhavenLab/.

Justin Eure | Newswise
Further information:
http://www.bnl.gov

More articles from Physics and Astronomy:

nachricht NASA scientist suggests possible link between primordial black holes and dark matter
25.05.2016 | NASA/Goddard Space Flight Center

nachricht The dark side of the fluffiest galaxies
24.05.2016 | Instituto de Astrofísica de Canarias (IAC)

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: Computational high-throughput screening finds hard magnets containing less rare earth elements

Permanent magnets are very important for technologies of the future like electromobility and renewable energy, and rare earth elements (REE) are necessary for their manufacture. The Fraunhofer Institute for Mechanics of Materials IWM in Freiburg, Germany, has now succeeded in identifying promising approaches and materials for new permanent magnets through use of an in-house simulation process based on high-throughput screening (HTS). The team was able to improve magnetic properties this way and at the same time replaced REE with elements that are less expensive and readily available. The results were published in the online technical journal “Scientific Reports”.

The starting point for IWM researchers Wolfgang Körner, Georg Krugel, and Christian Elsässer was a neodymium-iron-nitrogen compound based on a type of...

Im Focus: Atomic precision: technologies for the next-but-one generation of microchips

In the Beyond EUV project, the Fraunhofer Institutes for Laser Technology ILT in Aachen and for Applied Optics and Precision Engineering IOF in Jena are developing key technologies for the manufacture of a new generation of microchips using EUV radiation at a wavelength of 6.7 nm. The resulting structures are barely thicker than single atoms, and they make it possible to produce extremely integrated circuits for such items as wearables or mind-controlled prosthetic limbs.

In 1965 Gordon Moore formulated the law that came to be named after him, which states that the complexity of integrated circuits doubles every one to two...

Im Focus: Researchers demonstrate size quantization of Dirac fermions in graphene

Characterization of high-quality material reveals important details relevant to next generation nanoelectronic devices

Quantum mechanics is the field of physics governing the behavior of things on atomic scales, where things work very differently from our everyday world.

Im Focus: Graphene: A quantum of current

When current comes in discrete packages: Viennese scientists unravel the quantum properties of the carbon material graphene

In 2010 the Nobel Prize in physics was awarded for the discovery of the exceptional material graphene, which consists of a single layer of carbon atoms...

Im Focus: Transparent - Flexible - Printable: Key technologies for tomorrow’s displays

The trend-forward world of display technology relies on innovative materials and novel approaches to steadily advance the visual experience, for example through higher pixel densities, better contrast, larger formats or user-friendler design. Fraunhofer ISC’s newly developed materials for optics and electronics now broaden the application potential of next generation displays. Learn about lower cost-effective wet-chemical printing procedures and the new materials at the Fraunhofer ISC booth # 1021 in North Hall D during the SID International Symposium on Information Display held from 22 to 27 May 2016 at San Francisco’s Moscone Center.

Economical processing

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Networking 4.0: International Laser Technology Congress AKL’16 Shows New Ways of Cooperations

24.05.2016 | Event News

Challenges of rural labor markets

20.05.2016 | Event News

International expert meeting “Health Business Connect” in France

19.05.2016 | Event News

 
Latest News

LZH shows the potential of the laser for industrial manufacturing at the LASYS 2016

25.05.2016 | Trade Fair News

Great apes communicate cooperatively

25.05.2016 | Life Sciences

Thermo-Optical Measuring method (TOM) could save several million tons of CO2 in coal-fired plants

25.05.2016 | Power and Electrical Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>