Tuesday, November 9, 2010

There is still a Kondo problem

It was nice having Peter Wolfle visit UQ the past few days and give a colloquium style talk on the Kondo effect.
A nice accessible article which discusses the basics of the Kondo effect and how it occurs in quantum dots, carbon nanotubes, and "quantum corrals" is this 2001 Physics World article by Leo Kouwenhoven and Leonid Glazman.
In his talk Peter gave a nice discussion of the problem of the Kondo lattice (a lattice of localised spins interacting with a band of itinerant electrons). There is still an open question (originally posed by Doniach) of what happens in between the two limits of weak coupling (one expects magnetic ordering of the spins due to the RKKY interaction mediated by the itinerant electrons) and strong coupling (where the individual spins are Kondo screened by the itinerant electrons). Is there a quantum critical point? Does a non-Fermi liquid occur near it?
All of this is discussed in a nice review article Peter co-authored, Fermi liquid instabilities at magnetic phase transitions. It was very useful to Michael Smith and I when we wrote a PRL about possible Weidemann-Franz violations at a quantum critical point.
If you want a discussion of the RKKY-Kondo competition from the point of view of quantum entanglement, see this PRA paper  Sam Cho and I wrote.

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