The Kondo effect versus the RKKY interaction: a transport property study

L. COSTA RIBEIRO; I. J. HAMAD; E. V. ANDA; G. CHIAPPE

Aguas de Lindoia

Encuentro; XXXV Encontro Nacional de Física da Matéria Condensada; 2012

Sociedade Brasileira de Fisica

Two magnetic impurities interacting between themselves via conduction electrons give rise to physical phenomena, often encountered in experiments with two or more quantum dots that are basically dominated by the competition between Kondo physics and the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction. We study the transport properties of a system compo- sed of two quantum dots (magnetic S= 1/2 impurities) laterally coupled to an infinite chain of conduction electrons, using both slaves bosons in the mean field approximation and the Logarithmic-discretizationembedded-cluster approximation (LDECA), applied to the Anderson Hamiltonian with finite U. This allows us to study the RKKY interaction without arbitrarily incorporating a magnetic term JRKKY as an independent parameter as is usually done in the literature. We calculate the conductance G , the density of states at the impurities and at the intermediate conductions electrons between them, and the spin-spin correlation between the dots, as a function of the state of charge of the two impurities and of the coupling of them with the chain. These quantities exhibit different characteristic behaviors that manifest the competition of Kondo and RKKY physics. We discuss different scenarios and possible relations with experiments. It is shown that a measurement of the conductance is the appropriate experiment to be done to study these tworegimes and the crossover region between them.