Berlin 2008 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 6: Correlated Electrons: Heavy Fermions
TT 6.7: Vortrag
Montag, 25. Februar 2008, 11:15–11:30, EB 202
Relevance of the pseudogap for the thermopower of CeNiSn — •Ulrike Köhler1, Peijie Sun1, Toshiro Takabatake2, Silke Paschen3, Niels Oeschler1, and Frank Steglich1 — 1MPI for Chemical Physics of Solids, Dresden, Germany — 2Hiroshima University, Japan — 3Vienna University of Technology, Austria
CeNiSn has been classified as a correlated semimetal with a low charge carrier concentration. The opening of an anisotropic pseudogap below 10 K has been confirmed from various experimental probes. The gap formation can be suppressed significantly by application of magnetic fields of 10 T along the easy a axis.
We performed thermopower and Nernst effect measurements on high-purity single crystals of CeNiSn in the temperature range between 1.5 K and 200 K and in magnetic fields up to 7 T. Special care has been taken to correct the thermopower S for contributions from transverse components in a magnetic field. Our data clearly demonstrate the relevance of the pseudogap for the low-T thermopower. S(T) exhibits a large negative minimum below the temperature, at which the gap opens. Upon increasing magnetic field the minimum shifts to lower T wheras the absolute values at the minimum increase. We apply a simple model to describe this unusual field dependence of the thermopower.