Regensburg 2007 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 2: Quantum-Critical Phenomena

TT 2.11: Talk

Monday, March 26, 2007, 12:15–12:30, H19

Multiple energy scales at a quantum critical point — •P. Gegenwart¹, T. Westerkamp², C. Krellner², Y. Tokiwa³, S. Paschen⁴, C. Geibel², F. Steglich², E. Abrahams⁵, and Q. Si⁶ — ¹I. Physikalisches Institut, Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen — ²Max-Planck Institute for Chemical Physics of Solids, 01187 Dresden — ³Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA — ⁴Institute for Solid State Physics, Vienna University of Technology, 1004 Vienna, Austria — ⁵Center for Materials Theory, Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08855, USA — ⁶Department of Physics & Astronomy, Rice University, Houston, TX 77005, USA

We report thermodynamic and transport measurements at the magnetic-field-driven quantum critical point in the heavy fermion metal YbRh₂Si₂. The data define a new energy scale, which approaches zero as the quantum critical point (QCP) is reached. This scale is distinct from the crossover scale below which Fermi liquid behavior is established. The collapse of multiple energy scales provides evidence for a new type of quantum criticality, with critical excitations in addition to the slow fluctuations of the order parameter.