Dresden 2009 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 39: Correlated Electrons: Heavy Fermions 1
TT 39.3: Talk
Thursday, March 26, 2009, 10:15–10:30, HSZ 304
Do heavy charge carriers entail a large Nernst coefficient? — •Ulrike Köhler1,2, Cornelius Krellner1, Niels Oeschler1, Christoph Geibel1, and Frank Steglich1 — 1MPI for Chemical Physics of Solids, Dresden, Germany — 2present address: Leibniz Institute for Solid State and Materials Research (IFW) Dresden, Germany
The Nernst effect is the development of a transverse thermal voltage in a magnetic field perpendicular to a heat current. During the past years unusually large Nernst coefficients ν have been observed in several Ce- and U-based heavy-fermion (HF) compounds. It has been speculated, that the huge Nernst signals are related to the enhanced effective charge carrier masses m⋆ of these systems. So far, however, investigations on Yb-based HF metals are lacking to corroborate this picture. We therefore studied the Nernst effect in YbRh2Si2, an archetype non-Fermi-liquid compound with a Kondo temperature TK of 20 K. The Nernst coefficient is presented between 6 K and 200 K, i.e. covering the crossover from low effective charge carrier masses above TK to the HF regime at T ≪ TK. ν is found to be negative with a minimum close to TK, thus supporting the speculation about a relation between large ν and enhanced m⋆. The absolute values of the Nernst coefficient, however, are more than one order of magnitude smaller than in other HF systems. We discuss our findings in consideration of recent investigations on the correlated semiconductor CeNiSn, which point to a predominant importance of a low charge carrier density instead of a large m⋆ for the occurrence of a strong Nernst effect.