Theory of Huge Thermoelectric Effect Based on Magnon Drag Mechanism:\n Application to Thin-Film Heusler Alloy

Abstract

To understand the unexpectedly high thermoelectric performance observed in\nthe thin-film Heusler alloy Fe$_2$V$_{0.8}$W$_{0.2}$Al, we study the magnon\ndrag effect, generated by the tungsten based impurity band, as a possible\nsource of this enhancement, in analogy to the phonon drag observed in FeSb$_2$.\nAssuming that the thin-film Heusler alloy has a conduction band integrating\nwith the impurity band, originated by the tungsten substitution, we derive the\nelectrical conductivity $L_{11}$ based on the self-consistent t-matrix\napproximation and the thermoelectric conductivity $L_{12}$ due to magnon drag,\nbased on the linear response theory, and estimate the temperature dependent\nelectrical resistivity, Seebeck coefficient and power factor. Finally, we\ncompare the theoretical results with the experimental results of the thin-film\nHeusler alloy to show that the origin of the exceptional thermoelectric\nproperties is likely to be due to the magnon drag related with the\ntungsten-based impurity band.\n