Effect of topology on the transport properties of two interacting dots

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 intradot 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.

Spin-polarized conductance in double quantum dots: Interplay of Kondo, Zeeman, and interference effects

“…In this context, double-quantum-dot arrangements exhibit striking manifestations of Kondo physics, with conductance signatures of these effects predicted to show up in realistic experimental setups. A telling example is the interplay of Kondo physics and quantum interference in "side-coupled" or "hanging-dot" configurations, [11][12][13][14][15][16][17][18][19] leading to a variety of interesting "Fano-Kondo" effects. 20 A rather unexpected situation arises when a small, strongly interacting "dot 1" is connected to external leads via a large "dot 2" that is tuned to have a single-particle level in resonance with the com-mon Fermi energy of the leads.…”

Effect of the dot-dot interaction strength on the conductance of side-connected quantum dots

“…This is expected since the energy spacing between the peaks is approximately proportional to t 12 . Current cancellation at the Fermi level has also been obtained for this same system in a calculation using the embedded cluster method [5].…”

“…In the limit of weak tunneling interaction the electrons are localized on the individual dots while in the strong limit the delocalized electronic charge is no longer quantized. The transport properties depend also on the topology of the double-dot system [5]. For the case of the two dots aligned with the leads, in the weak coupling limit the interaction of each dot with the conduction electrons of the nearby lead gives rise to the Kondo in both dots.…”

“…Another system of two-interacting dots in the side-connected configuration has special interest since it permits the control of the current along the leads by changing the state of charge of the side-connected dot. The conductance of this system has been studied as a function of the gate potentials applied to the dots, using the embedded cluster method [5] and the numerical renormalization group technique [6]. In these two works the T=0 dependence of the conductance on the gate potential applied to the dots present different behaviors.…”

Enhanced conductance through side-coupled double quantum dots

“…1), connected to a single conduction-electron channel. Systems of this type were studied previously using non-crossing approximation 14 , embedding technique 15 and slaveboson mean field theory 13,16 . Numerical renormalization group (NRG) calculations were also performed recently 17 , where only narrow regimes of enhanced conductance were found at low temperatures.…”