Using new technique, scientists uncover a delicate magnetic balance for superconductivity

 A new imaging technology is giving scientists unprecedented views of the processes that affect the flow of electrons through materials.

By modifying a familiar tool in nanoscience -- the scanning tunneling microscope -- a team at Cornell University's Laboratory for Atomic and Solid State Physics have been able to visualize what happens when they change the electronic structure of a "heavy fermion" compound made of uranium, ruthenium and silicon. What they found sheds light on superconductivity -- the movement of electrons without resistance -which typically occurs at extremely low temperatures and that researchers hope one day to achieve at something close to room temperature, which would revolutionize electronics.

What they found was that, while at higher-temperatures magnetism is detrimental to superconductivity, at low temperatures in heavy fermion materials, magnetic atoms are a necessity. "We found that removing the magnetic atoms proved detrimental to the flow [of electrons]," said researcher Mohammad Hamidian. This is important, Hamidian explains, because "if we can resolve how superconductivity can co-exist with magnetism, then we have a whole new understanding of superconductivity, which could be applied toward creating high-temperature superconductors. In fact, magnetism at the atomic scale could become a new tuning parameter of how you can change the behavior of new superconducting materials that we make."

To make things finding, the researchers modified a scanning microscope that lets you pull or push electrons into a material. With the modification, the microscope could also measure how hard it was to push and pull -- a development that Hamidian explains is also significant. "By doing this, we actually learn a lot about the material's electronic structure. Then by mapping that structure out over a wide area, we can start seeing variations in those electronic states, which come about for quantum-mechanical reasons. Our newest advance, crucial to this paper, was the ability to see at each atom the strength of the interactions that make the electrons 'heavy.'"

The Cornell experiment and its results are presented this week by the Proceedings of the National Academy of Sciences. The research team included J.C. Séamus Davis, a member of the Kavli Institute at Cornell for Nanoscale Science and developer of the SI-STM technique. Working with synthesized samples created by Graeme Luke from McMaster University (Canada), the experiment was designed by Hamidian, a post-doctoral fellow in Davis' research group, along with Andrew R. Schmidt, a former student of Davis at Cornell and now a post-doctoral fellow in physics at UC Berkeley. 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 Ines Firmo of Brookhaven Lab and Cornell, and Andy Schmidt now at the University of California, Berkeley.

For the complete interview with Hamidian, visit: http://www.kavlifoundation.org/science-spotlights/Cornell-disturbing-nanosphere-superconductivity

Story Source:

The above story is reprinted from materials provided by The Kavli Foundation.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

M. H. Hamidian, A. R. Schmidt, I. A. Firmo, M. P. Allan, P. Bradley, J. D. Garrett, T. J. Williams, G. M. Luke, Y. Dubi, A. V. Balatsky, J. C. Davis. How Kondo-holes create intense nanoscale heavy-fermion hybridization disorder. Proceedings of the National Academy of Sciences, 2011; DOI: 10.1073/pnas.1115027108

Water channels in the body help cells remain in balance

microscopical water channels are also present in the cells of the body, where they ensure that water can be transported through the protective surface of the cell. Scientists at the University of Gothenburg, Sweden, have discovered that one type of the body's water channels can be modified such that it becomes more stable , which may be significant in the treatment of several diseases.

"It's important to understand how the water channels, which are known as 'aquaporins', in the body work, since they control many of the processes in our cells and tissues. They also determine what is to be transported into and out of the cell, and they are thus highly significant in the development of new treatments for various diseases, such as eczema, cerebral oedema, obesity and cancer", says Kristina Hedfalk of the Department of Chemistry at the University of Gothenburg.

Aquaporins are vital

There are 13 different types of aquaporins in the human body. One of these, AQP2, is found in the kidney where it is responsible for a large-volume recirculation of water from the primary urine every day. Without this, we would urinate nearly 10 litres every day. Another variant, AQP4, is found in the brain where it contributes to regulation of the osmotic pressure in the sensitive brain tissue. This regulation is particularly important in those who are affected by cerebral oedema, which is a life-threatening condition that can follow a blow to the head or a stroke.

The research group, which consists of Fredrik Öberg, Jennie Sjöhamn, Gerhard Fischer, Andreas Moberg, Anders Pedersen, Richard Neutze and Kristina Hedfalk, describes their studies of one of the most recently discovered aquaporins in an article in the scientific journal The Journal of Biological Chemistry. This aquaporin, AQP10, is preferentially found in the intestine, and is particularly interesting since it transports both water and sugar alcohols.

Carbohydrates stabilise the water channel

"AQP10 differs from other aquaporins by having a large carbohydrate structure of branched sugar molecules, somewhat similar to a tree, attached on its outer surface. This makes it significantly more stable. This may be because aquaporins in the intestine need to be particularly stable. What we have shown is that AQP10 retains its transport ability, even if the carbohydrate structure is removed."

More information: The article 'Glycosylation Increases the Thermostability of Human Aquaporin 10 Protein' has been published in the September edition of The Journal of Biological Chemistry.

Provided by University of Gothenburg (news : web)