my.chemeurope.com
With an accout for my.chemeurope.com you can always see everything at a glance – and you can configure your own website and individual newsletter.
06-08-2010: Scientists have captured the first images of electrons that appear to take on extraordinary mass under certain extreme conditions, thus solving a 25-year mystery about how electrons behave in metals. The discovery could help with the design of new materials for high-temperature superconductors.
The findings by scientists from McMaster University, Cornell University, the U.S. Department of Energy's Brookhaven and Los Alamos National Laboratories, are published in the current issue of Nature.
"When electrons interact in materials unpredictable things can happen," says Graeme Luke, professor in the Department of Physics & Astronomy at McMaster University. "Heavy fermion behavior—where electrons behave as if they weigh 1,000 times or more their actual mass—is one of the most fascinating examples of these phenomena. In this case, they were doing a kind of wave-like dance that changes the form and very nature of the electrons."
Using properties in a crystal composed of uranium, ruthenium and silicon— synthesized by doctoral candidate Travis Williams and staff member Jim Garrett in Luke's group using the facilities of the Centre for Crystal Growth at McMaster's Brockhouse Institute for Materials Research — the effects of heavy fermions began to appear as the material was cooled below 55 Kelvin (-218 °C). But an even more unusual electronic phase transition occurred below 17.5K.
Using a technique developed specifically for their experiment known as spectroscopic imaging scanning tunneling microscopy (SI-STM), the team was able to track the arrangement and interactions of electrons in the crystals, and watch how they react at different temperatures and see what happens when they passed through the mysterious phase transition.
"For 25 years we have known that there's a phase transition occurring in this material but we've never been able to identify what kind of order was occurring. It wasn't magnetic order or superconductivity," says Luke. "We didn't know if it was related to the way electrons were behaving in a group or whether it was the result of interactions between individual electrons and uranium atoms. The microscope, however, allowed us to actually see a change in the microscopic electron states."
"Imagine flying over a body of water where standing waves are moving up and down, but not propagating toward the shore," said study leader Séamus Davis, a physicist at Brookhaven and the J.D. White Distinguished Professor of Physical Sciences at Cornell University. "When you pass over high points, you can touch the water; over low points, you can't. This is similar to what our microscope does. It images how many electrons can jump to the tip of our probe at every point on the surface."
Based on these wavelength and energy measurements, scientists can calculate the effective electron mass for specific electron bands.
The researchers are continuing to probe a variety of related compounds with this new approach to further their understanding of heavy fermion systems.
Watchlist
This is where you can add this news to your personal favourites
Some chemicals could make you fat
Could persistent pollutants like DDT and PCBs or chemicals found in plastics be making you fat or diabetic? The answer may depend on what sort of bacteria you have churning around in your gut, according to Cornell scientists.In a paper published in Environmental Health Perspectives, Suzanne ... more
Brewery waste is scientific fodder for producing liquid biofuels
Anyone cracking open a cold beer is probably not considering the wastewater left over after the beer was brewed. But for Cornell researchers, that vinegary effluent is a scientific playground for devising ways to transform wastewater into biofuels.Employing powerful genome sequencing tools, ... more
SUSS MicroTec Announces Collaboration in Nano Research with Cornell University
SUSS MicroTec announced a strategic collaboration with the Cornell NanoScale Science & Technology Facility (CNF), a university nanofab based in North America. As part of the cooperation, Cornell staff will perform research using SUSS lithography equipment, including enhanced contact aligne ... more
Scientists capture secret dance of electrons that causes them to change form
Scientists have captured the first images of electrons that appear to take on extraordinary mass under certain extreme conditions, thus solving a 25-year mystery about how electrons behave in metals. The discovery could help with the design of new materials for high-temperature superconduct ... more
An inexpensive 'dipstick' test for pesticides in foods
Scientists in Canada are reporting the development of a fast, inexpensive "dipstick" test to identify small amounts of pesticides that may exist in foods and beverages. Their paper-strip test is more practical than conventional pesticide tests, producing results in minutes rather than hours ... more
Toxin detection as close as an inkjet printer
If that office inkjet printer has become just another fixture, it's time to take a fresh look at it. Similar technology may soon be used to develop paper-based biosensors that can detect certain harmful toxins that can cause food poisoning or be used as bioterrorism agents. In a paper publ ... more
Fleeting fluctuations in superconductivity disappear close to transition temperature
As part of an ongoing effort to uncover details of how high-temperature superconductors carry electrical current with no resistance, scientists at Johns Hopkins University and the U.S. Department of Energy's Brookhaven National Laboratory have measured fluctuations in superconductivity acro ... more
New highly stable fuel-cell catalyst gets strength from its nano core
Stop-and-go driving can wear on your nerves, but it really does a number on the precious platinum that drives reactions in automotive fuel cells. Before large fleets of fuel-cell-powered vehicles can hit the road, scientists will have to find a way to protect the platinum, the most expensiv ... more
Scientists produce transparent, light-harvesting material
Scientists at the U.S. Department of Energy's Los Alamos National Laboratory and Brookhaven National Laboratory have fabricated transparent thin films capable of absorbing light and generating electric charge over a relatively large area. The material, described in the journal Chemistry of ... more
Say hello to cheaper hydrogen fuel cells
Los Alamos National Laboratory scientists have developed a way to avoid the use of expensive platinum in hydrogen fuel cells, the environmentally friendly devices that might replace current power sources in everything from personal data devices to automobiles. In a paper published in Scienc ... more
Scientists produce transparent, light-harvesting material
Scientists at the U.S. Department of Energy's Los Alamos National Laboratory and Brookhaven National Laboratory have fabricated transparent thin films capable of absorbing light and generating electric charge over a relatively large area. The material, described in the journal Chemistry of ... more
Scientists capture secret dance of electrons that causes them to change form
Scientists have captured the first images of electrons that appear to take on extraordinary mass under certain extreme conditions, thus solving a 25-year mystery about how electrons behave in metals. The discovery could help with the design of new materials for high-temperature superconduct ... more
About CHEMIE.DE
CHEMIE.DE Information Service GmbH runs specialist scientific internet portals. The secret to our success? We are familiar with what we publish.
Advertising at CHEMIE.DE
Our advertising formats support you in getting your message across to a clearly defined target audience.
© 1997-2011 CHEMIE.DE Information Service GmbH, All rights reserved
