Non-Fermi Liquid Behavior of U-impurity with f^2-Singlet Ground State

概要

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It is shown by the Wilson numerical renormalization-group approach that a U-impurity with an f^2-singlet ground state exhibits an unstable non-Fermi liquid (NFL) fixed point due to the balance between Kondo singlet and crystalline-electric-field singlet ground state. The puzzling behavior of R_<1-x>U_xRu_2Si_2 (R=Th, Y and La, x≤0.07) can be explained if we assume that the singlet ground state is realized and the Kondo temperatures in each orbital are of different orders of magnitude. For a wide region in parameter space, the system shows the NFL behavior as a transient phenomenon in a experimentally possible temperature range. Results for the temperature dependence of resistivity, magnetic susceptibility and the Sommerfeld coefficient with and without a magnetic field reproduce the behavior observed in Th_<1-x>U_xRu_2Si_2. Less anomalous properties of R_<1-x>U_xRu_2Si_2 (R=Y and La) can be understood in the same scenario provided that these compounds have different sets of parameters.
2002-02-15