104 research outputs found
Charged excitons and biexcitons in laterally coupled InGaAs quantum dots
We present results of atomistic empirical pseudopotential calculations and
configuration interaction for excitons, positive and negative trions (X\pm),
positive and negative quartons (X2\pm) and biexcitons. The structure
investigated are laterally aligned InGaAs quantum dot molecules embedded in
GaAs under a lateral electric field. The rather simple energetic of excitons
becomes more complex in the case of charged quasiparticles but remains
tractable. The negative trion spectrum shows four anticrossings in the
presently available range of fields while the positive trion shows two. The
magnitude of the anticrossings reveals many-body effects in the carrier
tunneling process that should be experimentally accessible.Comment: 9 Pages, 9 Figures, 3 Pages. High quality figures at
http://www.fkf.mpg.de/bester/publications.htm
Effects of charged defects on the electronic and optical properties of self-assembled quantum dots
We investigate the effects of point charge defects on the single particle
electronic structure, emission energies, fine structure splitting and
oscillator strengths of excitonic transitions in strained
InGaAs/GaAs and strain-free GaAs/AlGaAs quantum
dots. We find that the charged defects significantly modify the single particle
electronic structure and excitonic spectra in both strained and strain-free
structures. However, the excitonic fine structure splitting, polarization
anisotropy and polarization direction in strained quantum dots remain nearly
unaffected, while significant changes are observed for strain-free quantum
dots.Comment: Submitted to PR
Asymmetry in self-assembled quantum dot-molecules made of identical InAs/GaAs quantum dots
We show that a diatomic dot molecule made of two identical, vertically
stacked, strained InAs/GaAs self-assembled dots exhibits an asymmetry in its
single-particle and may-particle wavefunctions. The single-particle wave
function is asymmetric due to the inhomogeneous strain, while the asymmetry of
the many-particle wavefunctions is caused by the correlation induced
localization: the lowest singlet and triplet states
show that the two electrons are each localized on different dots within the
molecule, for the next singlet states both electrons are localized
on the same (bottom) dot for interdot separation 8 nm. The singlet-triplet
splitting is found to be meV at inter-dot separation =9 nm and as
large as 100 meV for =4 nm, orders of magnitude larger than the few meV
found in the large (50 - 100 nm) electrostatically confined dots
Ab-initio investigation of the covalent bond energies in the metallic covalent superconductor MgB2 and in AlB2
The contributions of the covalent bond energies of various atom pairs to the
cohesive energy of MgB2 and AlB2 are analysed with a variant of our recently
developed energy-partitioning scheme for the density-functional total energy.
The covalent bond energies are strongest for the intralayer B-B pairs. In
contrast to the general belief, there is also a considerable covalent bonding
between the layers, mediated by the metal atom. The bond energies between the
various atom pairs are analysed in terms of orbital- and energy-resolved
contributions.Comment: 6 pages, 1 figure, 2 tables, submitted to PR
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