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Dresden 2009 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 6: Postersession Correlated Electrons: (General) Theory, Low-Dimensional Systems, Kondo Physics, Heavy Fermions, Quantum-Critical Phenomena

TT 6.58: Poster

Monday, March 23, 2009, 13:00–16:45, P1A

Strong electron correlations in FeSb2: An optical investigation and comparison with RuSb2 — •Alexander Herzog1, Michael Marutzky1, Jörg Sichelschmidt1, Anders Bentien1, Frank Steglich1, Shin-Ichi Kimura2, Simon Johnsen3, and Bo Iversen31MPI Chemical Physics of Solids, 01187 Dresden, Germany — 2UVSOR, Institute for Molecular Science, Okazaki 444-8585, Japan — 3Dep. of Chemistry, University of Aarhus, 8000 Aarhus, Denmark

We investigated the far-infrared optical conductivity of FeSb2, being a possible d electron Kondo semiconductor, and its non magnetic homologue RuSb2. For FeSb2 we found an indirect gap of 30 meV and semiconducting behavior for all crystal axes. Another gap feature at 6 meV, appearing below T=100 K, possibly corresponds to the colossal Seebeck coefficient [1] and may therefore be related to strong electronic correlations. However, we found a clear decrease of the reflectivity around 6 meV upon applying a magnetic field which demonstrates contradictory behavior to a common Kondo semiconductor scenario. We propose multiple absorptions due to disordered Fe atoms to be the origin of this gap feature. Furthermore, we discuss a possible relation of an anomalous change in the phonon spectrum of RuSb2 below 100 K to the opening of a 6 meV gap in the isostructural FeSb2. Nevertheless, strong electronic correlations are indicated by a temperature dependent spectral weight redistribution up to energies as large as 1 eV.

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

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