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arXiv · 1210.3379

Thermopower of the Correlated Narrow Gap Semiconductor FeSi and Comparison to RuSi

Jan M. Tomczak·K. Haule·G. Kotliar
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Abstract

Iron based narrow gap semiconductors such as FeSi, FeSb2, or FeGa3 have received a lot of attention because they exhibit a large thermopower, as well as striking similarities to heavy fermion Kondo insulators. Many proposals have been advanced, however, lacking quantitative methodologies applied to this problem, a consensus remained elusive to date. Here, we employ realistic many-body calculations to elucidate the impact of electronic correlation effects on FeSi. Our methodology accounts for all substantial anomalies observed in FeSi: the metallization, the lack of conservation of spectral weight in optical spectroscopy, and the Curie susceptibility. In particular we find a very good agreement for the anomalous thermoelectric power. Validated by this congruence with experiment, we further discuss a new physical picture of the microscopic nature of the insulator-to-metal crossover. Indeed, we find the suppression of the Seebeck coefficient to be driven by correlation induced incoherence. Finally, we compare FeSi to its iso-structural and iso-electronic homologue RuSi, and predict that partially substituted Fe(1-x)Ru(x)Si will exhibit an increased thermopower at intermediate temperatures.

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Jan M. Tomczak, K. Haule, G. Kotliar. 2012-10-11. Thermopower of the Correlated Narrow Gap Semiconductor FeSi and Comparison to RuSi. https://doi.org/10.1007/978-94-007-4984-9_4

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