Tuesday, June 25, 2013

Nernst effect as a probe of quasi-particle coherence

There is an interesting PRL

Nernst Effect: Evidence of Local Kondo Scattering in Heavy Fermions

by Peijie Sun and Frank Steglich 

They measure the temperature dependence of the Nernst coefficient for two different heavy fermion compounds and compare them to an isostructural compound without 4f electrons.
The temperature dependence is correlated with that of the thermoelectric power. 
An important question is Nernst signal is related to the coherence temperature associated with the formation of quasi-particles associated with the Fermi liquid.
But there is a complexity associated with this identification.

They argue that Nernst effect is largely a reflection of the single-ion Kondo effect and is measuring the strong energy dependence of the scattering rate.

They suggest the low temperature minimum and the high temperature maximum should be respectively identified with the Kondo temperature for the doublet ground state of the crystal effective field
and the Kondo temperature of the Hund's rule J=5/2 state of Ce3+.

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