Regensburg 2004 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 10: FV-internes Symposium ”Quantum Phase Transitions”

TT 10.2: Fachvortrag

Dienstag, 9. März 2004, 10:35–11:05, H18

Singular Behavior Near a Quantum Critical Point: YbRh₂(Si,Ge)₂ — •P. Gegenwart — Max-Planck-Institut für Chemische Physik fester Stoffe, 01187 Dresden

By discussing resistive, calorimetric, dilatometric and ESR data on YbRh₂(Si_1−xGe_x)₂ with 0≤ x < 0.05 we argue that these materials represent systems exhibiting a qualitatively new class of quantum critical point that cannot be described by the frequently adopted itinerant (3D or 2D) spin-density-wave scenario. Upon approaching the quantum critical point we observe large (“unscreened”, i.e., not reduced by the Kondo effect) magnetic Yb³⁺ moments in the static bulk susceptibility and recently in ESR, disparate behavior in the T-dependences of the electrical resistivity and the electronic specific heat as well as a fractional scaling exponent in the T-dependence of the thermal expansion. These findings seem to be compatible with a local-moment scenario for the quantum critical point.

In collaboration with J. Custers, J. Ferstl, C. Geibel, R. Küchler, T. Lühmann, K. Neumaier, S. Paschen, J. Sichelschmidt, G. Sparn, F. Steglich, Y. Tokiwa, H. Wilhelm, S. Wirth, P. Coleman, C. Pepin, and Q. Si.