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Regensburg 2004 – scientific programme

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TT: Tiefe Temperaturen

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

TT 10.2: Fachvortrag

Tuesday, March 9, 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(Si1−xGex)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.

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