M. S. Figueira

Fano resonance in electronic transport through a quantum wire with a side-coupled quantum dot: X -boson treatment

The transport through a quantum wire with a side-coupled quantum dot is studied. We use the X-boson treatment for the Anderson single impurity model in the limit of

Thermodynamic potential of the periodic Anderson model with the X-boson method: chain approximation

U=\ensuremath{\infty}.

Kondo effect in a quantum dot—the atomic approach

The conductance presents a minimum for values of

X-slave boson approach to the periodic Anderson model

T=0

Unveiling Majorana quasiparticles by a quantum phase transition: Proposal of a current switch

in the crossover from mixed valence to Kondo regime due to a destructive interference between the ballistic channel associated with the quantum wire and the quantum dot channel. We obtain the experimentally studied Fano behavior of the resonance. The conductance as a function of temperature exhibits a logarithmic and universal behavior, that agrees with recent experimental results.

Thermopower and thermal conductance through parallel coupled quantum dots

The periodic Anderson model (PAM) in the U→∞ limit has been studied in a previous work employing the cumulant expansion with the hybridization as perturbation (Figueira et al., Phys. Rev. B 50 (1994) 17933). When the total number of electrons Nt is calculated as a function of the chemical potential μ in the “chain approximation” (CHA), there are three values of the chemical potential μ for each Nt in a small interval of Nt at low T (Physica A 208 (1994) 279). We have recently introduced the “X-boson” method, inspired in the slave boson technique of Coleman, that solves the problem of nonconservation of probability (completeness) in the CHA as well as removing the spurious phase transitions that appear with the slave boson method in the mean field approximation. In the present paper, we show that the X-boson method solves also the problem of the multiple roots of Nt(μ) that appear in the CHA.

Thermodynamic properties of the periodic Anderson model: X-boson treatment

We describe the Kondo resonance in quantum dots employing the atomic approach for the Anderson impurity. The starting point of this approach is the exact solution of the Anderson impurity in the zero-bandwidth limit, and we choose the level of the atomic conduction band so that the completeness relation be satisfied. There are two or more solutions close to the chemical potential that satisfy this condition at low temperatures, and we choose the one with minimum Helmholtz free energy, considering that this corresponds to the Kondo solution. At low temperatures we obtain a density of states that characterizes well the structure of the Kondo peak. The results obtained for both the localized density of states at the chemical potential and for dynamical properties (like the conductance) agree very well with those obtained by the numerical renormalization group formalism and by the slave boson mean field approach, respectively. This result is a consequence of the satisfaction of the Friedel sum rule by the atomic approach in the Kondo limit. As a simple application we calculate the conductance of a side-coupled quantum dot.

Phase Evolution of the Electronic Transmission Through a Kondo Correlated Quantum Dot

Abstract The periodic anderson model (PAM) in the limit U=∞, can be studied by employing the Hubbard X operators to project out the unwanted states. In a previous work, we have studied the cumulant expansion of this Hamiltonian employing the hybridization as a perturbation, but probability conservation of the local states (completeness) is not usually satisfied when partial expansions like the “chain approximation (CHA)” are employed. To consider this problem, we use a technique similar to the one employed by Coleman to treat the same problem with slave-bosons in the mean-field approximation. Assuming a particular renormalization for hybridization, we obtain a description that avoids an unwanted phase transition that appears in the mean-field slave-boson method at intermediate temperatures.

Non-Zeeman splitting for a spin-resolved STM with a Kondo adatom in a spin-polarized two-dimensional electron gas

We propose a theoretical approach based on an interferometer composed by two quantum dots asymmetrically coupled to isolated Majorana quasiparticles (MQPs), lying on the edges of two topological Kitaev chains, respectively, via couplings

Electronic Transport Through a QuantumWire with a Side-Coupled Quantum Dot

(t+\mathrm{\ensuremath{\Delta}})