Maria A. Davidovich

Transport in coupled quantum dots: Kondo effect versus antiferromagnetic correlation

The interplay between the Kondo effect and the interdot magnetic interaction in a coupled-dot system is studied. An exact result for the transport properties at zero temperature is obtained by diagonalizing a cluster, composed by the double dot and its vicinity, which is connected to leads. It is shown that the system goes continuously from the Kondo regime to an antiferromagnetic state as the interdot interaction is increased. The conductance, the charge at the dots, and the spin-spin correlation are obtained as a function of the gate potential.

KONDO RESONANCE EFFECT ON PERSISTENT CURRENTS THROUGH A QUANTUM DOT IN A MESOSCOPIC RING

The persistent current through a quantum dot inserted in a mesoscopic ring of length L is studied. A cluster representing the dot and its vicinity is exactly diagonalized and embedded into the rest of the ring. The Kondo resonance provides a new channel for the current to flow. It is shown that due to scaling properties, the persistent current at the Kondo regime is enhanced relative to the current flowing either when the dot is at resonance or along a perfect ring of same length. In the Kondo regime the current scales as

Method to study highly correlated nanostructures: The logarithmic-discretization embedded-cluster approximation

L^{-1/2}

Phase effects on the conductance through parallel double dots

, unlike the

Correlation effects in metastable (Ga As)1−x Ge2x alloys

L^{-1}

Renormalization group treatment for the electronic spectrum of partially ordered one-dimensional alloys

scaling of a perfect ring. We discuss the possibility of detection of the Kondo effect by means of a persistent current measurement.

Effect of topology on the transport properties of two interacting dots

This work proposes an approach to study transport properties of highly correlated local structures. The method, dubbed the logarithmic discretization embedded cluster approximation LDECA, consists of diagonalizing a finite cluster containing the many-body terms of the Hamiltonian and embedding it into the rest of the system, combined with Wilson s idea of a logarithmic discretization of the representation of the Hamiltonian. The physics associated with both one embedded dot and a double-dot side coupled to leads is discussed in detail. In the former case, the results perfectly agree with Bethe ansatz data, while in the latter, the physics obtained is framed in the conceptual background of a two-stage Kondo problem. A many-body formalism provides a solid theoretical foundation to the method. We argue that LDECA is well suited to study complicated problems such as transport through molecules or quantum dot structures with complex ground states.

Kondo effect and persistent currents in a mesoscopic ring: Numerically exact results

Phase effects on the conductance of a double-dot system in a ring structure threaded by a magnetic flux are studied. The Aharonov-Bohm effect combined with the dot many-body charging effects determine the phases of the currents going through each arm of the ring. The cases for zero magnetic flux or half a quantum of flux are discussed in detail. It is shown that, depending upon the magnetic flux and the state of charge of the dots, controlled by gate potentials, the dephasing of the upper and lower arm current gives rise to a

Coupled quantum dots: effect of inter-dot interactions

S=1∕2

Persistent currents in a mesoscopic ring with a side connected quantum dot

or