Thursday, January 12, 2012

Thermopower reveals destruction of quasi-particles

There is a nice preprint, Thermoelectric Power of the YbT2Zn20 (T = Fe, Ru, Os, Ir, Rh, and Co) Heavy Fermions by E. D. Mun, S. Jia, S. L. Bud’ko, and P. C. Canfield

The figure below shows the temperature dependence of the thermoelectric power for the title compounds. Note that it non-monotonic, being linear at low temperatures, reaching a maximum magnitude of order k_B/e ~ 80 microV/K at a temperature T_min.
 The next figure shows that T_min (left scale) is correlated with the single ion Kondo temperature (horizontal scale) and the temperature at which the resistivity is a maximum (right scale).
 The magnitude of the linear temperature dependence at low temperatures is simply related to that for the specific heat (see also this earlier post) as shown in the Figure below.

Aside: the inset on the lower right considers the Kadowaki-Woods ratio but does not make use of recent work concerning its universality.
All of the above features seem to be characteristic of broad classes of strongly correlated electron metals, as emphasized by Jaime Merino and I, in a PRB published in 2000. The temperature scales in the middle figure are characteristic of that at which there is a crossover from a Fermi liquid at low temperature to a bad metal at higher temperatures.

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