Llorens Serra

Orbital current mode in elliptical quantum dots

An orbital current mode peculiar to deformed quantum dots is theoretically investigated; first by using a simple model that allows to interpret analytically its main characteristics, and second, by numerically solving the microscopic equations of time evolution after an initial perturbation within the time-dependent local-spin-density approximation. Results for different deformations and sizes are shown.

Rashba interaction in quantum wires with in-plane magnetic fields

We analyze the spectral and transport properties of ballistic quasi one-dimensional systems in the presence of spin-orbit coupling and in-plane agnetic fields. Our results demonstrate that Rashba precession and intersubband coupling must be treated on equal footing for wavevectors near the magnetic field induced gaps. We find that intersubband coupling limits the occurrence of negative effective masses at the gap edges and modifies the linear conductance curves in the strong coupling limit. The effect of the magnetic field on the spin textured orientation of the wire magnetization is discussed.

Spin splitting and precession in quantum dots with spin-orbit coupling: The role of spatial deformation

Extending a previous work on spin precession in GaAs/AlGaAs quantum dots with spin-orbit coupling, we study the role of deformation in the external confinement. Small elliptical deformations are enough to alter the precessional characteristics at low magnetic fields. We obtain approximate expressions for the modified g factor including weak Rashba and Dresselhaus spin-orbit terms. For more intense couplings numerical calculations are performed. We also study the influence of the magnetic-field orientation on the spin splitting and the related anisotropy of the g factor. Spin-orbit coupling effects can reproduce the experimental spin splittings reported by Hanson et al. [Phys. Rev. Lett. 91, 196802 (2003)] for a one-electron dot. For dots containing more electrons, Coulomb interaction effects are estimated within the local-spin-density approximation, showing that many features of the noninteracting system are qualitatively preserved.

OSCILLATION MODES OF TWO-DIMENSIONAL NANOSTRUCTURES WITHIN THE TIME-DEPENDENT LOCAL-SPIN-DENSITY APPROXIMATION

We apply the time-dependent local-spin-density approximation to describe ground states and spin-density oscillations in the linear response regime of two-dimensional nanostructures of arbitrary shape. For this purpose, a frequency analysis of the simulated real-time evolution is performed. It is shown that the recently proposed spin-density waves in the ground state of certain parabolic quantum dots lead to the prediction of a novel class of excitations, soft spin-twist modes with energies well below that of the spin dipole oscillation.

Current-density-functional approach to large quantum dots in intense magnetic fields

Within current-density-functional theory, we have studied a quantum dot made of 210 electrons confined in a disk geometry. The ground state of this large dot exhibits some features as a function of the magnetic field (B) that can be attributed in a clear way to the formation of compressible and incompressible states of the system. The orbital and spin angular momenta, the total energy, ionization and electron chemical potentials of the ground state, as well as the frequencies of far-infrared edge modes are calculated as a function of B , and compared with available experimental and theoretical results. @S0163-1829~98!01923-7#

Electronic spin precession in semiconductor quantum dots with spin-orbit coupling

The electronic spin precession in semiconductor dots is strongly affected by the spin-orbit coupling. We present a theory of the electronic spin resonance at low magnetic fields that predicts a strong dependence on the dot occupation, the magnetic field and the spin-orbit coupling strength. Coulomb interaction effects are also taken into account in a numerical approach.

Magnetic-field instability of Majorana modes in multiband semiconductor wires

This work was supported by Grants No. FIS2008-00781, No. FIS2009-08744, No. FIS2011-23526, and No. CSD2007- 00042 (CPAN) of the Spanish Government.

Transport through Majorana nanowires attached to normal leads

This paper presents a coupled channel model for transport in two-dimensional semiconductor Majorana nanowires coupled to normal leads. When the nanowire hosts a zero-mode pair, conspicuous signatures of the linear conductance are predicted. An effective model in second quantization allowing a fully analytical solution is used to clarify the physics. We also discuss the nonlinear current response (dI/dV ).

Zeeman energy and anomalous spin splitting in lateral GaAs quantum dots

Abstract.The level splittings induced by a horizontal magnetic field in a parabolic two-dimensional quantum dot with spin-orbit interaction are obtained. Characteristic features induced by the spin-orbit coupling are the appearance of zero-field gaps as well as energy splittings that depend on the electronic state and the orientation of the magnetic field in the quantum-dot plane. It is suggested that these quantum-dot properties could be used to determine the Rashba and Dresselhaus spin-orbit intensities

Role of spin-orbit coupling in the far-infrared absorption of lateral semiconductor dots

We investigate the relevance of the spin-orbit coupling to the far-infrared absorption of two-dimensional semiconductor dots. Varying the strength of the Dresselhaus term, a mechanism feasible in experiment by changing the dot width, distinctive splittings of the Kohn peak as well as additional low-energy modes are predicted in a noninteracting model. Each mode has a spatial distribution of charge, perpendicular and in-plane spin densities that correlate in a peculiar way with the frequency and polarization of the external field. We study the robustness of these features against electron-electron interactions as well as the appearance of interaction-induced additional characteristics.