We investigate the thermoelectric propeties 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 tightbinding model that correctly reproduces this band structure, and this gives results close to the experimental observations. The origin of this peculiar band shape is also discussed.
@article{arxiv.1211.7176,
title = {Large Seebeck effect in the electron-doped FeAs$_2$ driven by quasi one dimensional pudding-mold type band},
author = {Hidetomo Usui and Kazuhiko Kuroki and Seiya Nakano and Kazutaka Kudo and Minoru Nohara},
journal= {arXiv preprint arXiv:1211.7176},
year = {2013}
}