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| VOLUME 96 (2012) | ISSUE 6 | PAGE 436 |
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Nature of the quantum critical point as disclosed by extraordinary behavior of magnetotransport and the Lorentz number in the heavy-fermion metal YbRh2Si2
V. R. Shaginyan+*, A. Z. Msezane*, K. G. Popov×, J. W. Clark°, M. V. Zverev
 , V. A. Khodel∇°+Petersburg Nuclear Physics Institute, 188300 Gatchina, Russia *Clark Atlanta University, GA 30314 Atlanta, USA ×Komi Science Center UD of the RAS, 167982 Syktyvkar, Russia °McDonnell Center for the Space Sciences & Department of Physics, Washington University, St. Louis, MO 63130, USA ∇Russian Research Centre "Kurchatov Institute", 123182 Moscow, Russia  Moscow Institute of Physics and Technology, 123098 Moscow, Russia
Abstract
Physicists are engaged in vigorous debate on the nature of the quantum critical points (QCP) governing the low-temperature properties of heavy-fermion (HF) metals. Recent experimental observations of the much-studied compound YbRh2Si2 in the regime of vanishing temperature incisively probe the nature of its magnetic-field-tuned QCP. The jumps revealed both in the residual resistivity ρ0 and the Hall resistivity R H, along with violation of the Wiedemann-Franz law, provide vital clues to the origin of such non-Fermi-liquid behavior. The empirical facts point unambiguously to association of the observed QCP with a fermion-condensation phase transition. Based on this insight, the resistivities ρ0 and R H are predicted to show jumps at the crossing of the QCP produced by application of a magnetic field, with attendant violation of the Wiedemann-Franz law. It is further demonstrated that experimentally identifiable multiple energy scales are related to the scaling behavior of the effective mass of the quasiparticles responsible for the low-temperature properties of such HF metals. |