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Hidden non-Fermi liquid behavior due to crystal field quartet

Mikito Koga
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Abstract

We study a realistic Kondo model for crystal field quartet ground states having magnetic and non-magnetic (quadrupolar) exchange couplings with conduction electrons, using the numerical renormalization group method. We focus on a local effect dependent on singlet excited states coupled to the quartet, which reduces the non-magnetic coupling significantly and drives non-Fermi liquid behavior observed in the calculated quadrupolar susceptibility. A crossover from the non-Fermi liquid state to the Fermi liquid state is characterized by a small energy scale very sensitive to the non-magnetic coupling. On the other hand, the Kondo temperature observed in the magnetic susceptibility is less sensitive. The different crystal-field dependence of the two exchange couplings may be related to the different $x$ dependence of quadrupolar and magnetic ordering temperatures in Ce$_x$La$_{1-x}$B$_6$.

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Mikito Koga. 1999-07-09. Hidden non-Fermi liquid behavior due to crystal field quartet. https://doi.org/10.1103/physrevb.61.395

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