Regensburg 2013 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 59: Correlated Electrons: Quantum-Critical Phenomena - Experiments

TT 59.6: Talk

Thursday, March 14, 2013, 16:15–16:30, H6

Heat and charge transport study of quantum critical behavior in heavy fermion YbAgGe — •Jinkui Dong¹, Yoshi Tokiwa¹, Maik Schubert¹, Sergey L. Bud’ko², Paul C. Canfield², and Philipp Gegenwart¹ — ¹I. Physikalisches Institut, Georg-August-Universität Göttingen, 37077 Göttingen, Germany — ²Ames Laboratory and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA

We have performed electrical resistivity and thermal conductivity measurements on the heavy fermion metal YbAgGe to investigate quantum critical behavior and the validity of Wiedemann-Franz law. A power law analysis of electrical resistivity ρ (T), ρ (T) = ρ₀ + ATⁿ showed that NFL behavior with n < 2 persists in fields up to 9 T. A broad maximum of ρ(H) appeared in the vicinity of critical field H_c ≃ 4.5 T, where a field-induced quantum critical end point (QCEP) was expected. Far away from this critical region, the Lorenz ratio L(T)/L₀ converges to unity in the limit of T → 0. However, near the QCEP, the extrapolation of L(T)/L₀ gives L(T → 0)/L₀ ≃ 0.91. We associate this moderate violation of Wiedemann-Franz law at 4.5 T with the strong inelastic scattering of electrons from the quantum critical fluctuations.