Nanotechnology Now







Heifer International

Wikipedia Affiliate Button


DHgate

Home > Press > Impurity Atoms Introduce Waves of Disorder in Exotic Electronic Material: Sophisticated electron-imaging technique reveals widespread "destruction," offering clues to how material works as a superconductor

Top: Visualization of nanoscale disruptions in electron interactions in a Kondo-hole doped heavy-fermion compound. The black-and-white inset shows directly how oscillations in electron behavior are centered on the Thorium impurities, "rippling" outward like disturbances caused by drops of water on a still pond. The rippling oscillations in electron energy are shown in more detail in the close-up view (bottom), where the bands of different shades of blue represent the distance between the ripples.
Top: Visualization of nanoscale disruptions in electron interactions in a Kondo-hole doped heavy-fermion compound. The black-and-white inset shows directly how oscillations in electron behavior are centered on the Thorium impurities, "rippling" outward like disturbances caused by drops of water on a still pond. The rippling oscillations in electron energy are shown in more detail in the close-up view (bottom), where the bands of different shades of blue represent the distance between the ripples.

Abstract:
It's a basic technique learned early, maybe even before kindergarten: Pulling things apart - from toy cars to complicated electronic materials - can reveal a lot about how they work. "That's one way physicists study the things that they love; they do it by destroying them," said Séamus Davis, a physicist at the U.S. Department of Energy's (DOE) Brookhaven National Laboratory and the J.G. White Distinguished Professor of Physical Sciences at Cornell University.

Impurity Atoms Introduce Waves of Disorder in Exotic Electronic Material: Sophisticated electron-imaging technique reveals widespread "destruction," offering clues to how material works as a superconductor

Upton, NY | Posted on October 18th, 2011

Davis and colleagues recently turned this destructive approach - and a sophisticated tool for "seeing" the effects - on a material they've been studying for its own intrinsic beauty, and for the clues it may offer about superconductivity, the ability of some materials to carry electric current with no resistance. The findings, published in the Proceedings of the National Academy of Sciences the week of October 17, 2011, reveal how substituting just a few atoms can cause widespread disruption of the delicate interactions that give the material its unique properties, including superconductivity.

The material, a compound of uranium, ruthenium, and silicon, is known as a "heavy-fermion" system. "It's a system where the electrons zooming through the material stop periodically to interact with electrons localized on the uranium atoms that make up the lattice, or framework of the crystal," Davis said. These stop-and-go magnetic interactions slow down the electrons, making them appear as if they've taken on extra mass, but also contribute to the material's superconductivity.

In 2010*, Davis and a group of collaborators visualized these heavy fermions for the first time using a technique developed by Davis, known as spectroscopic imaging scanning tunneling microscopy (SI-STM), which measures the wavelength of electrons of the material in relation to their energy.

The idea of the present study was to "destroy" the heavy fermion system by substituting thorium for some of the uranium atoms. Thorium, unlike uranium, is non-magnetic, so in theory, the electrons should be able to move freely around the thorium atoms, instead of stopping for the brief magnetic encounters they have at each uranium atom. These areas where the electrons should flow freely are known as "Kondo holes," named for the physicist who first described the scattering of conductive electrons due to magnetic impurities.

Free-flowing electrons might sound like a good thing if you want a material that can carry current with no resistance. But Kondo holes turn out to be quite destructive to superconductivity. By visualizing the behavior of electrons around Kondo holes for the first time, Davis' current research helps to explain why.

"There have been beautiful theories that predict the effects of Kondo holes, but no one knew how to look at the behavior of the electrons, until now," Davis said.

Working with thorium-doped samples made by physicist Graeme Luke at McMaster University in Ontario, Davis' team used SI-STM to visualize the electron behavior.

"First we identified the sites of the thorium atoms in the lattice, then we looked at the quantum mechanical wave functions of the electrons surrounding those sites," Davis said.

The SI-STM measurements bore out many of the theoretical predictions, including the idea proposed just last year by physicist Dirk Morr of the University of Illinois that the electron waves would oscillate wildly around the Kondo holes, like ocean waves hitting a lighthouse.

"Our measurements revealed waves of disturbance in the 'quantum glue' holding the heavy fermions together," Davis said.

So, by destroying the heavy fermions - which must pair up for the material to act as a superconductor - the Kondo holes disrupt the material's superconductivity.

Davis' visualization technique also reveals how just a few Kondo holes can cause such widespread destruction: "The waves of disturbance surrounding each thorium atom are like the ripples that emanate from raindrops suddenly hitting a still pond on a calm day," he said. "And like those ripples, the electronic disturbances travel out quite a distance, interacting with one another. So it takes a tiny number of these impurities to make a lot of disorder."

What the scientists learn by studying the exotic heavy fermion system may also pertain to the mechanism of other superconductors that can operate at warmer temperatures.

"The interactions in high-temperature superconductors are horribly complicated," Davis said. "But understanding the magnetic mechanism that leads to pairing in heavy fermion superconductors - and how it can so easily be disrupted - may offer clues to how similar magnetic interactions might contribute to superconductivity in other materials."

This research was supported by the DOE's Office of Science, the Natural Sciences and Engineering Research Council of Canada, and the Canadian Institute for Advanced Research. Additional collaborators included Mohammad Hamidian and Ines Firmo of Brookhaven Lab and Cornell, and Andy Schmidt now at the University of California, Berkeley.

####

About Brookhaven National Laboratory
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 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 www.bnl.gov/newsroom , or follow Brookhaven Lab on Twitter, twitter.com/BrookhavenLab .

For more information, please click here

Contacts:
Karen McNulty Walsh

(631) 344-8350
or
Peter Genzer

(631) 344-3174

Copyright © Brookhaven National Laboratory

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 Links

First Images of Heavy Electrons in Action:

Related News Press

News and information

From brittle to plastic in 1 breath: Rice University theorists show environments can alter 2-D materials' basic properties May 4th, 2015

Nanoparticles in consumer products can significantly alter normal gut microbiome May 4th, 2015

New Nanodrug Produced in Iran from Milk Thistle May 4th, 2015

Antibacterial Ceramic Nanoparticles, Appropriate Material for Medical Devices May 3rd, 2015

Production of Industrial Nano-Membrane for Water, Wastewater Purification Device in Iran May 2nd, 2015

Superconductivity

Oxford Instruments announces winners of the 2015 Sir Martin Wood Science Prize for China May 2nd, 2015

Novel superconducting undulator provides first x-ray light at ANKA May 1st, 2015

Physics

Oxford Instruments announces winners of the 2015 Sir Martin Wood Science Prize for China May 2nd, 2015

Imaging

Time Dependant Spectroscopy of Microscopic Samples: CRAIC TimePro™ software is used with CRAIC Technologies microspectrometers to measure the kinetic UV-visible-NIR, Raman and fluorescence spectra of microscopic sample areas May 2nd, 2015

ORNL researchers probe chemistry, topography and mechanics with one instrument May 2nd, 2015

Laboratories

ORNL researchers probe chemistry, topography and mechanics with one instrument May 2nd, 2015

Govt.-Legislation/Regulation/Funding/Policy

From brittle to plastic in 1 breath: Rice University theorists show environments can alter 2-D materials' basic properties May 4th, 2015

ORNL researchers probe chemistry, topography and mechanics with one instrument May 2nd, 2015

Making robots more human April 29th, 2015

Artificial photosynthesis could help make fuels, plastics and medicine April 29th, 2015

Discoveries

From brittle to plastic in 1 breath: Rice University theorists show environments can alter 2-D materials' basic properties May 4th, 2015

Nanoparticles in consumer products can significantly alter normal gut microbiome May 4th, 2015

Antibacterial Ceramic Nanoparticles, Appropriate Material for Medical Devices May 3rd, 2015

ORNL researchers probe chemistry, topography and mechanics with one instrument May 2nd, 2015

Announcements

From brittle to plastic in 1 breath: Rice University theorists show environments can alter 2-D materials' basic properties May 4th, 2015

Nanoparticles in consumer products can significantly alter normal gut microbiome May 4th, 2015

New Nanodrug Produced in Iran from Milk Thistle May 4th, 2015

Antibacterial Ceramic Nanoparticles, Appropriate Material for Medical Devices May 3rd, 2015

Research partnerships

Electron chirp: Cyclotron radiation from single electrons measured directly for first time: Method has potential to measure neutrino mass and look beyond the Standard Model of the universe April 29th, 2015

Weighing -- and imaging -- molecules one at a time April 28th, 2015

SUNY Poly and Sematech Announce Air Products Joins Cutting-Edge CMP Center At Albany Nanotech Complex April 28th, 2015

When mediated by superconductivity, light pushes matter million times more April 28th, 2015

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