Anomalous reduction of the Lorenz ratio at the quantum critical point in YbAgGe

We report measurements of the electrical and thermal transport on the hexagonal heavy-fermion metal YbAgGe for temperatures T ≥ 40  mK and in magnetic fields H∥ab up to 14 T. This distorted kagome-lattice system displays a series of magnetic states and a quantum critical point at H(c) = 4.5  T. The...

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Bibliographic Details
Published in:Physical review letters 2013-04, Vol.110 (17), p.176402-176402, Article 176402
Main Authors: Dong, J K, Tokiwa, Y, Bud'ko, S L, Canfield, P C, Gegenwart, P
Format: Article
Language:English
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Summary:We report measurements of the electrical and thermal transport on the hexagonal heavy-fermion metal YbAgGe for temperatures T ≥ 40  mK and in magnetic fields H∥ab up to 14 T. This distorted kagome-lattice system displays a series of magnetic states and a quantum critical point at H(c) = 4.5  T. The Lorenz ratio L(T)/L0 displays a marked reduction only close to H(c). A T-linear contribution below 120 mK, present at all different fields, allows us to extrapolate the Lorenz ratio towards T = 0. At the critical field this yields L/L0 = 0.92±0.03, suggesting a violation of the Wiedemann-Franz law due to strong inelastic scattering.
ISSN:0031-9007
1079-7114
DOI:10.1103/physrevlett.110.176402