Tunable "Doniach Phase Diagram" for strongly-correlated nanoclusters

TL;DR

This paper demonstrates how the energy level spacing in nanoclusters influences the competition between Kondo and RKKY interactions, creating a tunable phase diagram relevant for quantum dot and nanoring experiments.

Contribution

It introduces a tunable Doniach phase diagram for nanoclusters, showing how energy spacing and electron parity affect magnetic correlations.

Findings

Energy spacing tunes Kondo-RKKY competition.

Parity of electron number affects magnetic interactions.

Below a critical hybridization, susceptibility shows exponential activation.

Abstract

Exact diagonalization calculations reveal that the energy spacing $\Delta$ in the conduction band tunes the interplay between the {\it local} Kondo and {\it non local} RKKY interactions, giving rise to a "Doniach phase diagram" for a nanocluster with regions of prevailing Kondo or RKKY correlations. The parity of the total number of electrons alters the competition between the Kondo and RKKY correlations. This interplay may be relevant to experimental realizations of small rings or quantum dots with tunable magnetic properties. Below a critical value V$_c$ of the hybridization the susceptibility exhibits a low-T exponential activation behavior determined by the interplay of the spin gap and $\Delta$.