28 research outputs found
Anisotropic electron g-factor in quantum dots with spin-orbit interaction
g-factor tuning of electrons in quantum dots is studied as function of
in-plane and perpendicular magnetic fields for different confinements. Rashba
and Dresselhaus effects are considered, and comparison is made between wide-
and narrow-gap materials. The interplay between magnetic fields and intrinsic
spin-orbit coupling is analyzed, with two distinct phases found in the spectrum
for GaAs in perpendicular field. The anisotropy of the g-factor is reported,
and good agreement with available experimental findings is obtained.Comment: 5 pages, 4 figs. (higher resol. figs. under request
Transport properties of nano-devices: One-dimensional model study
A 1D model study of charge transport in nano-devices is made by comparing
multi-configuration time dependent Hartree-Fock and frozen core calculations.
The influence of exchange and Coulomb correlation on the tunneling current is
determined. We identify the shape of the tunneling barrier and the resonance
structure of the nano-device as the two dominant parameters determining the
electron transport. Whereas the barrier shape determines the size of the
tunneling current, the resonances determine the structure of the current.Comment: 4 page
The violation of the Hund's rule in semiconductor artificial atoms
The unrestricted Pople-Nesbet approach for real atoms is adapted to quantum
dots, the man-made artificial atoms, under applied magnetic field. Gaussian
basis sets are used instead of the exact single-particle orbitals in the
construction of the appropriated Slater determinants. Both system chemical
potential and charging energy are calculated, as also the expected values for
total and z-component in spin states. We have verified the validity of the
energy shell structure as well as the Hund's rule state population at zero
magnetic field. Above given fields, we have observed a violation of the Hund's
rule by the suppression of triplets and quartets states at the 1p energy shell,
taken as an example. We also compare our present results with those obtained
using the LS-coupling scheme for low electronic occupations. We have focused
our attention to ground-state properties for GaAs quantum dots populated up to
forty electrons.Comment: 5 pages, 2 figures, submitted to Semic. Sci. Techno
Spin-orbit coupling and intrinsic spin mixing in quantum dots
Spin-orbit coupling effects are studied in quantum dots in InSb, a narrow-gap
material. Competition between different Rashba and Dresselhaus terms is shown
to produce wholesale changes in the spectrum. The large (and negative)
-factor and the Rashba field produce states where spin is no longer a good
quantum number and intrinsic flips occur at moderate magnetic fields. For dots
with two electrons, a singlet-triplet mixing occurs in the ground state, with
observable signatures in intraband FIR absorption, and possible importance in
quantum computation.Comment: REVTEX4 text with 3 figures (high resolution figs available by
request). Submitted to PR