Dresden 2009 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 39: Correlated Electrons: Heavy Fermions 1

TT 39.3: Vortrag

Donnerstag, 26. März 2009, 10:15–10:30, HSZ 304

Do heavy charge carriers entail a large Nernst coefficient? — •Ulrike Köhler^1,2, 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 T_K 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 T_K to the HF regime at T ≪ T_K. ν is found to be negative with a minimum close to T_K, 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.