12,498 research outputs found
Spin-orbit effects on the Larmor dispersion relation in GaAs quantum wells
We have studied the relevance of spin-orbit coupling to the dispersion 00009
relation of the Larmor resonance observed in inelastic light scattering and
electron-spin resonance experiments on GaAs quantum wells. We show that the
spin-orbit interaction, here described by a sum of Dresselhaus and
Bychkov-Rashba terms, couples Zeeman and spin-density excitations. We have
evaluated its contribution to the spin splitting as a function of the magnetic
field , and have found that in the small limit, the spin-orbit
interaction does not contribute to the spin splitting, whereas at high magnetic
fields it yields a independent contribution to the spin splitting given by
, with being the intensity of the
Bychkov-Rashba and Dresselhaus spin-orbit terms.Comment: To be published in Physical Review
Vertically coupled double quantum rings at zero magnetic field
Within local-spin-density functional theory, we have investigated the
`dissociation' of few-electron circular vertical semiconductor double quantum
ring artificial molecules at zero magnetic field as a function of inter-ring
distance. In a first step, the molecules are constituted by two identical
quantum rings. When the rings are quantum mechanically strongly coupled, the
electronic states are substantially delocalized, and the addition energy
spectra of the artificial molecule resemble those of a single quantum ring in
the few-electron limit. When the rings are quantum mechanically weakly coupled,
the electronic states in the molecule are substantially localized in one ring
or the other, although the rings can be electrostatically coupled. The effect
of a slight mismatch introduced in the molecules from nominally identical
quantum wells, or from changes in the inner radius of the constituent rings,
induces localization by offsetting the energy levels in the quantum rings. This
plays a crucial role in the appearance of the addition spectra as a function of
coupling strength particularly in the weak coupling limit.Comment: 18 pages, 8 figures, submitted to Physical Review
Metallic and Insulating Adsorbates on Graphene
We directly compare the effect of metallic titanium (Ti) and insulating
titanium dioxide (TiO2) on the transport properties of single layer graphene.
The deposition of Ti results in substantial n-type doping and a reduction of
graphene mobility by charged impurity scattering. Subsequent exposure to oxygen
largely reduces the doping and scattering by converting Ti into TiO2. In
addition, we observe evidence for short-range scattering by TiO2 impurities.
These results illustrate the contrasting scattering mechanisms for identical
spatial distributions of metallic and insulating adsorbates
Finite size effects in adsorption of helium mixtures by alkali substrates
We investigate the behavior of mixed 3He-4He droplets on alkali surfaces at
zero temperature, within the frame of Finite Range Density Functional theory.
The properties of one single 3He atom on 4He_N4 droplets on different alkali
surfaces are addressed, and the energetics and structure of 4He_N4+3He_N3
systems on Cs surfaces, for nanoscopic 4He drops, are analyzed through the
solutions of the mean field equations for varying number N3 of 3He atoms. We
discuss the size effects on the single particle spectrum of 3He atoms and on
the shapes of both helium distributions.Comment: 12 pages, and 12 figures (PNG format
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