Eur. Phys. J. B (2012) 85: 203
https://doi.org/10.1140/epjb/e2012-30060-0

Regular Article

Thermoelectric properties of the Kondo insulator FeSb₂

¹ Instituto de Física, Universidade Federal Fluminense, Av. Litorânea s/n, 24210-346 Niterói, Rio de Janeiro, Brazil
² Departamento de Física, Universidad Nacional de Colombia, 5997 Bogotá, Colombia

^a e-mail: figueira@if.uff.br

Received: 24 January 2012
Published online: 20 June 2012

Abstract

Recently it was shown [A. Bentien, S. Johnsen, G.K.H. Madsen, B.B. Iversen, F. Steglich, Europhys. Lett. 80, 17008 (2007)], that the strongly correlated Kondo insulator FeSb₂ exhibits a colossal Seebeck coefficient; however, due to its large lattice thermal conductivity, the dimensionless thermoelectric figure of merit (zT) is only 0.005 at 12 K. This experimental result motivate us to perform a theoretical study of the thermoelectric properties of Kondo insulators, within the framework of the X-boson approach [R. Franco, M.S. Figueira, M.E. Foglio, Phys. Rev. B 66, 045112 (2002)] for the periodic Anderson model. We consider a set of parameters adequate for describing the compound FeSb₂, and we calculate the resistivity, the thermoelectric power (Seebeck coefficient), the charge carrier thermal conductance, the thermoelectric factor power (zT), the Wiedemann-Franz law, the specific heat, and the Sommerfeld’s γ coefficient. The result of the colossal maximum of the Seebeck coefficient, at low temperatures, has the same order of magnitude as the experimental result [A. Bentien, S. Johnsen, G.K.H. Madsen, B.B. Iversen, F. Steglich, Europhys. Lett. 80, 17008 (2007)]. We also show that those temperature region presents an intermediate valence behavior, characterized by a moderate increase of the Sommerfeld’s γ coefficient.