Berlin 2008 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 6: Correlated Electrons: Heavy Fermions

TT 6.12: Talk

Monday, February 25, 2008, 12:30–12:45, EB 202

Optical Studies on the Strongly Correlated Semiconductor FeSb₂ and on RuSb₂ — •Alexander Herzog¹, Michael Marutzky¹, Jörg Sichelschmidt¹, Anders Bentien¹, Frank Steglich¹, Shin-ichi Kimura², Simon Johnsen³, and Bo Iversen³ — ¹MPI Chemical Physics of Solids, 01187 Dresden, Germany — ²UVSOR, Institute for Molecular Science, Okazaki 444-8585, Japan — ³Dep. of Chemistry, University of Aarhus, 8000 Århus C, Denmark

The narrow band gap semiconductor FeSb₂ has similar properties to FeSi and both materials are discussed in the framework of a Kondo insulator model. We measured the optical conductivity of single crystals of FeSb₂ from 3 meV up to 30 eV by means of reflectivity spectroscopy. We compare the spectra of FeSb₂ with those of its non-magnetic homologue RuSb₂. In contrast to previous reports [1], our samples of FeSb₂ are semiconducting for all crystal axes. The far-infrared optical spectra are characterized by both phononic and electronic contributions. The phononic part displays a strong electron-phonon coupling at elevated temperatures whereas the electronic part presents an indirect gap of 30 meV which agrees well with the value inferred from transport measurements [2]. Another gap feature at 6 meV is probably related to the extraordinary large Seebeck coefficient of FeSb₂ [2]. We observed a temperature dependent spectral weight redistribution within a large energy range which clearly extends 1 eV indicating the presence of strong electronic correlations.

[1] A. Perucchi et al., Eur. Phys. J. B 54, 175 (2006)

[2] A. Bentien et al., Europhys. Lett. 80, 39901 (2007)