Regensburg 2007 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 2: Quantum-Critical Phenomena
TT 2.12: Vortrag
Montag, 26. März 2007, 12:30–12:45, H19
Electric transport at the quantum critical point in YbRh2Si2 — •Sven Friedemann1, Niels Oeschler1, Cornelius Krellner1, Christoph Geibel1, Silke Paschen1,2, and Frank Steglich1 — 1Max Planck Institute for Chemical Physics of Solids, Noethnitzer Strasse 40, 01187 Dresden, Germany — 2Vienna University of Technology, Karlsplatz 13, 1040 Wien, Austria
The heavy-fermion metal YbRh2Si2 exhibits pronounced non-Fermi liquid (NFL) behavior due to its vicinity to a quantum critical point (QCP). By applying small magnetic fields, YbRh2Si2 is driven from an antiferromagnetic state through the QCP towards the paramagnetic state. Currently, two scenarios for a system at this type of QCP are discussed: The spin-density-wave scenario at which heavy electrons are present on both sides of the QCP and the locally QCP at which the heavy electrons on the paramagnetic side disintegrate into localized magnetic moments and light conduction electrons on the magnetic side of the QCP. The field-dependent Hall effect as a measure of the Fermi volume is assumed to be the appropriate method to characterize the QCP in YbRh2Si2. As an extension to previous results [1] we present low temperature Hall-effect data of new high-quality samples which confirm a step in RH for T→ 0 and thus support the local scenario. The T dependence of the height and the width of the crossover are discussed. Corresponding features are also observed in the magnetoresistance. Furthermore, the maximum of the Hall-effect at T ≈ 1 K is presumably due to the spin fluctuations in the NFL region.
([1] S. Paschen et al., Nature 432, 881 (2004))