RKKY interaction for strongly correlated electrons

Reinhold Egger, Herbert Schoeller

The RKKY law and the Kondo screening cloud around a magnetic impurity are investigated for correlated electrons in one dimension (Luttinger liquid). We find slow algebraic distance dependences, with a crossover between both types of behavior. Monte Carlo simulations have been developed to study this crossover. In the strong-coupling regime, the Knight shift is shown to increase with distance due to correlations. \textcopyright{} 1996 The American Physical Society.

David Sénéchal, A.–M. S. Tremblay, C. Bourbonnais

Tomás Bortolin, C. J. Bolech, Nayana Shah +1 more

We address the physics of a regular arrangement of independent magnetic impurities embedded in a band of interacting electrons. We focus on the one-dimensional case that can be studied using bosonization and in which the electron bulk is described by a Luttinger liquid. The impurity spins interact with the electrons via magnetic exchange that introduces the possibility of Kondo and Ruderman-Kittel-Kasuya-Yosida (RKKY) physics. We find that for two special values of the interactions, the model can be refermionized as a noninteracting electron band hybridized with a regular array of resonant levels. These solvable limits provide access to impurity correlators that correspond to either extended algebraic order or local screening. A physical picture emerges of how the interelectron interactions can stabilize either Kondo or RKKY physics depending on the sign of the interaction.

J. J. Quinn, George Simion

Lidia Stocker, Oded Zilberberg

Quantum dots exhibit a variety of strongly correlated effects, e.g., they can emulate localized magnetic impurities that form a Kondo singlet with their surrounding environment. Interestingly, in double-dot setups, such magnetic impurities couple to each other by direct Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction, which wins over the Kondo physics. In this work, we investigate a double-dot device where the dots are coupled via off-resonant ballistic modes, dubbed electronic cavity modes. Within this cavity-double-dot system, we study, using variational matrix product state techniques, the competition between Kondo formation and the combined coherent orbital hybridization and RKKY-like interaction that the cavity facilitates. Specifically, we find that Kondo can form on each dot individually whereby the cavity can either (i) destroy the Kondo via the RKKY that mediates a singlet state on the two dots, or (ii) lead to an exotic orbital macrsoscopic superposition of the Kondo forming on each of the dots. We dub the latter “Kondo cat”. En route to this key finding, we rigorously study the many-body phase diagram of the system, as well as compare it with the case of coupling the dots via an incoherent RKKY channel. The realization of a Kondo cat can facilitate applications in metrology, and reveal the spin coherence length in mesoscopic devices. Published by the American Physical Society 2024