Competition between Kondo effect and RKKY interactions in heavy-fermion systems: Specific heat

Abstract

The excess electronic specific heat for a Ce-based system ${\mathrm{CeCu}}_{2}{\mathrm{Si}}_{2}$ is calculated using the Kondo and Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction Hamiltonian within the framework of Abrikosov's pseudofermion representation in the presence of crystalline electric field (CEF) split levels. The spin-flip scattering of the electrons caused by the indirect exchange interaction of a pair of magnetic impurities has been considered. It is found that for Ce-based compounds in general, the competition between the Kondo and RKKY interactions, along with the effect of the CEF splitting, yields a behavior varying from a minimum at low temperatures to a monotonically decreasing behavior in $\ensuremath{\Delta}C/T$ vs ${T}^{2}$ towards higher $T.$ The overall behavior of $\ensuremath{\Delta}C/T$ is found to be quite sensitive to the RKKY coupling and CEF splitting \ensuremath{\delta} in the lowest doublet scheme. The results are found to be consistent with the experimental data.