22 research outputs found
Zeeman energy and anomalous spin splitting in lateral GaAs quantum dots
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 intensitiesComment: 6 pages, 6 figures. To be published in Eur. Phys. J. B (2004
Interplay between Zeeman interaction and spin-orbit coupling in a two-dimensional semiconductor system
We analyse the interplay between Dresselhaus, Bychkov-Rashba, and Zeeman
interactions in a two-dimensional semiconductor quantum system under the action
of a magnetic field. When a vertical magnetic field is considered, we predict
that the interplay results in an effective cyclotron frequency that depends on
a spin-dependent contribution. For in-plane magnetic fields, we found that the
interplay induces an anisotropic effective gyromagnetic factor that depends on
the orientation of the applied field as well as on the orientation of the
electron momentum.Comment: 5 page
Quantum dots based on spin properties of semiconductor heterostructures
The possibility of a novel type of semiconductor quantum dots obtained by
spatially modulating the spin-orbit coupling intensity in III-V
heterostructures is discussed. Using the effective mass model we predict
confined one-electron states having peculiar spin properties. Furthermore, from
mean field calculations (local-spin-density and Hartree-Fock) we find that even
two electrons could form a bound state in these dots.Comment: 9 pages, 3 figures. Accepted in PRB (Brief Report) (2004
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 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 factor. Using realistic spin-orbit strengths our
model calculations can reproduce the experimental spin-splittings reported by
Hanson et al. (cond-mat/0303139) 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
non-iteracting system are qualitatively preserved.Comment: 7 pages, 7 figure
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.Comment: 5 pages, 4 figure
Spin control in semiconductor quantum wires
We show that spin-flip rotation in a semiconductor quantum wire, caused by
the Rashba and the Dresselhaus interactions (both of arbitrary strengths), can
be suppressed by dint of an in-plane magnetic field. We found a new type of
symmetry, which arises at a particular set of intensity and orientation of the
magnetic field and explains this suppression. Based on our findings, we propose
a transport experiment to measure the strengths of the Rashba and the
Dresselhaus interactions.Comment: 4 pages, 4 figure
Predicted signatures of the intrinsic spin Hall effect in closed systems
We study a two-dimensional electron system in the presence of spin-orbit
interaction. It is shown analytically that the spin-orbit interaction acts as a
transversal effective electric field, whose orientation depends on the sign of
the -axis spin projection. This effect doesn't require any driving
external field and is inherent to the spin-orbit interactions present in
semiconductor materials. Therefore, it should manifest in both closed and open
systems. It is proposed an experiment to observe the intrinsic spin Hall effect
in the far infrared absorption of an asymmetric semiconductor nanostructure.Comment: accepted for publication in Physical Review Letter
Tratamiento con talidomida en estomatitis aftosa recurrente en una paciente pediátrica
El uso de talidomia es controvertido y especialmente en población pediátrica, si bien es cierto las publicaciones disponibles avalan su uso en determinadas condiciones en las que la presencia de aftas bucales comprometa la calidad de vida de los pacientes y éstas no hayan sido resueltas con los tratamientos habituales.
En nuestro caso nos encontramos ante una paciente pediátrica donde la estomatitis aftosa condicionaba incluso su correcta alimentación, por este motivo y tras realizar las pruebas oportunas para determinar las causas de las mismas se decide comenzar el tratamiento con talidomida. Los resultados fueron muy positivos en cuanto a reducción de episodios aftosos pero los efectos adversos observados en la paciente condicionaron la suspensión del tratamiento.
La implicación farmacéutica hizo posible una coordinación entre atención primaria y especializada, un asesoramiento tanto a personal sanitario como a la paciente y tutores legales, la adquisición del fármaco y la elaboración de una fórmula magistral adaptada a los cambios posológicos. Por otro lado el estrecho seguimiento de la paciente y de los efectos adversos hizo posible su suspensión en el momento en el que la relación beneficio/riesgo ya no era favorable.
Tratamiento con talidomida en estomatitis aftosa recurrente en una paciente pediátrica
El uso de talidomia es controvertido y especialmente en población pediátrica, si bien es cierto las publicaciones disponibles avalan su uso en determinadas condiciones en las que la presencia de aftas bucales comprometa la calidad de vida de los pacientes y éstas no hayan sido resueltas con los tratamientos habituales.
En nuestro caso nos encontramos ante una paciente pediátrica donde la estomatitis aftosa condicionaba incluso su correcta alimentación, por este motivo y tras realizar las pruebas oportunas para determinar las causas de las mismas se decide comenzar el tratamiento con talidomida. Los resultados fueron muy positivos en cuanto a reducción de episodios aftosos pero los efectos adversos observados en la paciente condicionaron la suspensión del tratamiento.
La implicación farmacéutica hizo posible una coordinación entre atención primaria y especializada, un asesoramiento tanto a personal sanitario como a la paciente y tutores legales, la adquisición del fármaco y la elaboración de una fórmula magistral adaptada a los cambios posológicos. Por otro lado el estrecho seguimiento de la paciente y de los efectos adversos hizo posible su suspensión en el momento en el que la relación beneficio/riesgo ya no era favorable.