Unlocking the secret of the Kondo Effect

September 22nd, 2008

(PhysOrg.com) -- A team of scientists including researchers from the London Centre for Nanotechnology at UCL (University College London) and the IBM Almaden Research Center has forged a breakthrough in understanding an intriguing phenomenon in fundamental physics: the Kondo effect. The findings are reported online today in the scientific journal Nature Physics.

The Kondo effect, one of the few examples in physics where many particles collectively behave as one object (a single quantum-mechanical body), has intrigued scientists around the world for decades. When a single magnetic atom is located inside a metal, the free electrons of the metal ‘screen’ the atom. That way, a cloud of many electrons around the atom becomes magnetized.

Sometimes, if the metal is cooled down to very low temperatures, the atomic spin enters a so-called ‘quantum superposition’ state. In this state its north-pole points in two opposite directions at the same time. As a result, the entire electron cloud around the spin will also be simultaneously magnetized in two directions.

Now, using a technique that was developed by the same team in 2007, the researchers have shown that it is possible to predict when the Kondo effect will occur – and to understand why. The key turns out to be in the geometry of a magnetic atom’s immediate surroundings. By carefully studying how this geometry influences the magnetic moment (or “spin”) of the atom, the emergence of the Kondo effect can now be predicted and understood.

Dr. Cyrus Hirjibehedin, a member of the IBM team who is now a Lecturer at UCL (University College London) and a part of the academic staff of the LCN, said: “This result represents a major advance in our understanding of this fundamental physical phenomenon and could have important consequences for future nanoscale magnetic devices.”

Citation: 'The role of magnetic anisotropy in the Kondo effect', by A. F. Otte, M. Ternes, K. von Bergmann, S. Loth, H. Brune, C.P. Lutz, C.F. Hirjibehedin and A.J. Heinrich, is published in the journal Nature Physics.

Provided by University College London

• phystic - Sep 22, 2008
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  for some reason it brings to mind the story from a few days ago:
  
  http://www.physor...122.html
  
  Researchers discover unexpected properties of materials in lowermost mantle:
  ""We were surprised to find partially paired electrons," said Lin. "That doesn't normally occur in other geological materials that we know about."
  
  oh the good ole' physorg comments section ;-)
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• D666 - Sep 22, 2008
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  Kondo Effect as the explanation for telepathy, teleportation, and as the "active ingredient" in cures for impotence, indigestion, gout, cancer, high blood pressure, and social awkwardness in 3..2..1..
  
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• Bob_B - Sep 22, 2008
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  Huh?
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• Question - Sep 22, 2008
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  Wouldn't a much simpler explanation be that at a low enough temperature (energy level) the atoms fall into opposite spins? Opposite atomic spins would create two opposite magnetic fields.
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• D666 - Sep 23, 2008
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  Huh?

  
  
  Have you not noticed that every nut-bar cure and wacky bit of pseudo-science includes valid scientific terms? Tossed around in a manner that would make real scientists grab their throats and fall to the ground. This Kondo Effect sounds like just the perfect fodder for something like "The R-bracelet! Made of COLD steel! It'll increase your intelligence using QUANTUM STATES! Based on REAL SCIENCE!"
  
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