Dresden 2009 – wissenschaftliches Programm

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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

Montag, 23. März 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 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 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).