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TT: Fachverband Tiefe Temperaturen

TT 3: Correlated Electrons: Heavy Fermions

TT 3.9: Talk

Monday, March 26, 2012, 11:45–12:00, H 3005

High-field thermoelectric transport in YbRh₂Si₂ — R. Daou, •H. Pfau, M. Brando, C. Krellner, C. Geibel, and F. Steglich — MPI CPfS, Nöthnitzer Str. 40, 01187 Dresden, Germany

The heavy fermion compound YbRh₂Si₂ has attracted much interest providing an example of an unconventional quantum critical point that can be approached using very small magnetic fields. However, there are also anomalous features at higher fields that have not been well explored, and these may give us further insights into the electronic state of this unusual material. We report thermopower measurements on the best available single crystals of YbRh₂Si₂ at temperatures down to 0.1 K and magnetic fields up to 12 T applied along the ab-plane. We find two step-like features in the field dependence at 9 T and 11 T, the region where a suppression of the heavy fermion state was reported [1]. Additionally, another step appears at 3.5 T. These steps in thermopower correspond to features found in electrical transport [2]. The experimental results are supported by recently published renormalized bandstructure calculations [3] which show two features in the field dependent quasiparticle density of states at around 4 T and at 10 T. In these calculation, the anomalies at 10T in various quantities are caused by a van-Hove-type singularity below the Fermi energy. However, the separation into two features in thermopower and in resistivity remains unexplained as well as the origin of the clear 3.5 T-signature.
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