Effect of topology on the transport properties of two interacting dots

TL;DR

This paper investigates how the topology of a two-dot system influences its transport properties, revealing richer physics in side-coupled configurations, including Kondo states, Coulomb blockade, and interference effects affecting conductance.

Contribution

It provides a comparative analysis of transport behaviors in side-coupled versus aligned double-dot systems, highlighting the impact of topology on many-body interactions and conductance.

Findings

Side-coupled dots exhibit a Kondo state and Coulomb blockade.

Topology affects spin correlations, switching from antiferromagnetic to ferromagnetic.

Conductance suppression arises from interference effects at resonance.

Abstract

The transport properties of a system of two interacting dots, one of them directly connected to the leads constituting a side-coupled configuration (SCD), are studied in the weak and strong tunnel-coupling limits. The conductance behavior of the SCD structure has new and richer physics than the better studied system of two dots aligned with the leads (ACD). In the weak coupling regime and in the case of one electron per dot, the ACD configuration gives rise to two mostly independent Kondo states. In the SCD topology, the inserted dot is in a Kondo state while the side-connected one presents Coulomb blockade properties. Moreover, the dot spins change their behavior, from an antiferromagnetic coupling to a ferromagnetic correlation, as a consequence of the interaction with the conduction electrons. The system is governed by the Kondo effect related to the dot that is embedded into the leads. The role of the side-connected dot is to introduce, when at resonance, a new path for the electrons to go through giving rise to the interferences responsible for the suppression of the conductance. These results depend on the values of the intra-dot Coulomb interactions. In the case where the many-body interaction is restricted to the side-connected dot, its Kondo correlation is responsible for the scattering of the conduction electrons giving rise to the conductance suppression.