Friday, August 8, 2014

Large thermal conductivity of correlated semiconductors

Previously I posted about the challenge of understanding the colossal thermoelectric effect in FeSb2 and the puzzles of the classic Kondo insulator FeSi.

I talked about the former yesterday at the cake meeting [take 7 minutes to convince everyone they should read a particular paper]. I noticed for the first time just how large the thermal conductivity is, actually comparable to diamond at low temperatures.

The red curve is FeSb2 and the black curve FeAs2, which is less correlated.

This is of interest for at least two reasons.

1. The large thermal conductivity is bad for thermoelectric applications as it will significantly reduce the thermoelectric figure of merit.

2. It needs to be explained theoretically, including the large difference between FeSb2 and FeAs2. [Presumably the phonons are similar in the two compounds].

3?. Does this make reliable thermoelectric measurements harder or easier?

For comparison below I show the temperature dependence of the  thermal conductivity of diamond and copper, taken from here. [n.b. the vertical scale is different by a factor of 100 compared to the above graph].

I welcome comments.

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