Large Seebeck effect in electron-doped FeAs2 driven by a quasi-one-dimensional pudding-mold-type band

Hidetomo Usui, Katsuhiro Suzuki, Kazuhiko Kuroki, Seiya Nakano, Kazutaka Kudo, Minoru Nohara

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25 Citations (Scopus)

Abstract

We investigate the thermoelectric properties of the electron-doped FeAs2 both experimentally and theoretically. Electrons are doped by partially substituting Se for As, which leads to a metallic behavior in the resistivity. A Seebeck coefficient of about -200 μV/K is reached at 300 K for 1% doping, and about -120 μV/K even at 5% doping. The origin of this large Seebeck coefficient, despite the metallic conductivity, is analyzed from a band structure point of view. The first-principles band calculation reveals the presence of a pudding-mold-type band just above the band gap, somewhat similar to NaxCoO2, but with a quasi-one-dimensional nature. We calculate the Seebeck coefficient using a tight-binding model that correctly reproduces this band structure, and this gives results roughly in agreement with the experiments. Moreover, a consideration of electron correlations beyond the generalized gradient approximation by the fluctuation exchange method gives even better agreement. The origin of this peculiar band shape is also discussed. Combined with previous studies, we now have good thermoelectric materials with quasi-one-, two-, and three-dimensional band structures that have partially flat portions. The present study reinforces the general efficiency of this peculiar band shape in thermoelectric materials.

Original languageEnglish
Article number075140
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume88
Issue number7
DOIs
Publication statusPublished - Aug 26 2013

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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