Francisco Claro

Controlling Fano and Dicke effects via a magnetic flux in a two-site Anderson model

The electronic transport through a parallel double quantum-dot molecule attached asymmetrically to leads is studied under a magnetic field. We model the system by means of a non interacting two-impurity Anderson Hamiltonian. We find that the conductance shows Fano and Dicke effects that can be controlled by the magnetic flux.

A Terahertz Molecular Switch

We present time-dependent results describing the current through a molecular device, modeled as a complex with two active centers connected to leads under bias. We show that, at a properly adjusted external voltage, a passing terahertz electromagnetic pulse may cause a transition between states of finite and negligible current, suggesting that the system might be useful as a nanoscopic switch in the terahertz range. A phase diagram defining the bias region in which the transition takes place within a short time is given. As described, the physical processes involved are of an entirely different nature than those in ordinary photodetectors.

Delocalization and conductance quantization in one-dimensional systems attached to leads

We investigate the delocalization and conductance quantization in finite one-dimensional chains with only off-diagonal disorder coupled to leads. It is shown that the appearance of delocalized states at the middle of the band under correlated disorder is strongly dependent upon the even-odd parity of the number of sites in the system. In samples with inversion symmetry the conductance equals

Fano resonances and Aharonov-Bohm effects in transport through a square quantum dot molecule

{2e}^{2}/h

Exact random walk distributions using noncommutative geometry

for odd samples and is smaller for even parity. This result suggests that this even-odd behavior found previously in the presence of electron correlations may be unrelated to charging effects in the sample.

Transient heat transport in solids

We study the Aharonov-Bohm effect in a coupled 232 quantum dot array with two terminals. A striking conductance dip arising from the Fano interference is found as the energy levels of the intermediate dots are mismatched, which is lifted in the presence of a magnetic flux. A five peak structure is observed in the conductance for large mismatch. The Aharonov-Bohm evolution of the linear conductance strongly depends on the configuration of dot levels and interdot and dot-lead coupling strengths. In addition, the magnetic flux and asymmetry between dot-lead couplings can induce the splitting and combination of the conductance peak~s!.

Multipolar effects in particulate matter

Using the results obtained by the non-commutative geometry techniques applied to the Harper equation, we derive the areas distribution of random walks of length N on a two-dimensional square lattice for large N , taking into account finite-size contributions.

On the fractional quantum Hall effect

It is shown that heat flow is severely decreased in transient phenomena, due to nonlocal effects. The case of phonon transport in a steep temperature gradient is discussed in detail for semiconductors. Fixed end temperatures and an initial heat pulse propagating in a homogeneous sample are considered as boundary conditions. The temperature profile evolves in all cases significantly slower than local theories predict.

Magnetic-Field-Induced Directional Localization in a 2D Rectangular Lattice

Abstract The effect of induced multipoles on the surface modes of particulate matter in the quasistatic regime are discussed. Numerical evidence suggests that the dipole approximation fails for an interparticle distance σ of 1.5 particle diameters. At smaller separations high multipole terms have dramatic effects on the absorption spectrum and provide an enhancement of dispersion forces. A criterion for the approximation required in terms of σ is provided.

DYNAMIC INSTABILITIES IN RESONANT TUNNELING INDUCED BY A MAGNETIC FIELD

Abstract We show in the Hartree-Fock approximation that the formation of a two dimensional electron lattice allows for a natural explanation of the anomalous fractional quantum Hall effect. Landau levels are broadened and split in a number of bands in such a way that if the number of electrons per unit cell is a half odd integer the Fermi energy is in a gap for an odd filling fraction denominator, and at the center of a band if the denominator is even.