12 research outputs found
Nucleus-mediated spin-flip transitions in GaAs quantum dots
Spin-flip rates in GaAs quantum dots can be quite slow, thus opening up the
possibilities to manipulate spin states in the dots. We present here
estimations of inelastic spin-flip rates mediated by hyperfine interaction with
nuclei. Under general assumptions the nucleus mediated rate is proportional to
the phonon relaxation rate for the corresponding non-spin-flip transitions. The
rate can be accelerated in the vicinity of a singlet-triplet excited states
crossing. The small proportionality coefficient depends inversely on the number
of nuclei in the quantum dot. We compare our results with known mechanisms of
spin-flip in quantum dot.Comment: RevTex 4 pages, 1 figure, submitted to Phys. Rev.
Electronic transport through nuclear-spin-polarization-induced quantum wire
Electron transport in a new low-dimensional structure - the nuclear spin
polarization induced quantum wire (NSPI QW) is theoretically studied. In the
proposed system the local nuclear spin polarization creates the effective
hyperfine field which confines the electrons with the spins opposite to the
hyperfine field to the regions of maximal nuclear spin polarization. The
influence of the nuclear spin relaxation and diffusion on the electron energy
spectrum and on the conductance of the quantum wire is calculated and the
experimental feasibility is discussed.Comment: 5 pages, 4 figure
Hyperfine-driven persistent currents in mesoscopic rings based on a 2D electron gas with Rashba spin-orbit interaction
We present a detailed theory of induced persistent current (PC) produced by hyperfine interaction in mesoscopic rings based on a 2 D electron (hole) gas in the absence of external magnetic field. PC emerges due to combined action of the hyperfine interaction of charge carriers with polarized nuclei, spin-orbit interaction and Berry phase
Quantum Computation in Quantum-Hall Systems
We describe a quantum information processor (quantum computer) based on the
hyperfine interactions between the conduction electrons and nuclear spins
embedded in a two-dimensional electron system in the quantum-Hall regime.
Nuclear spins can be controlled individually by electromagnetic pulses. Their
interactions, which are of the spin-exchange type, can be possibly switched on
and off pair-wise dynamically, for nearest neighbors, by controlling
impurities. We also propose the way to feed in the initial data and explore
ideas for reading off the final results.Comment: 12 pages in LaTeX + 1 PostScript figur
Localized states in 2D semiconductors doped with magnetic impurities in quantizing magnetic field
A theory of magnetic impurities in a 2D electron gas quantized by a strong
magnetic field is formulated in terms of Friedel-Anderson theory of resonance
impurity scattering. It is shown that this scattering results in an appearance
of bound Landau states with zero angular moment between the Landau subbands.
The resonance scattering is spin selective, and it results in a strong spin
polarization of Landau states, as well as in a noticeable magnetic field
dependence of the factor and the crystal field splitting of the impurity
levels.Comment: 12 pages, 4 figures Submitted to Physical Review B This version is
edited and updated in accordance with recent experimental dat
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
Hyperfine-interaction-driven Aharonov-Bohm effect in mesoscopic rings
It is shown qualitatively that lifting of the electron spin degeneracy by a hyperfine field, which is
generated by a nonequilibrium nuclear spin distribution, and breaking of the left-right symmetry by the
spin-orbit interaction in a closed ring produces under certain conditions a persistent current, which
demonstrates the Aharonov-Bohm-like oscillations with time in GaAs / AlGaAs-based mesoscopic rings
even m the absence of an external magnetic field. The typical time interval of these (mesonucleospinic)
oscillations is of the order of several seconds, which is typical of the nuclear spin relaxation times in
heterojunctions
High field magnetotransport in low dimensional interacting electron systems Final report
Available from TIB Hannover: F98B1576 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEGerman-Israeli Foundation for Scientific Research and Development (GIF), Oberschleissheim (Germany)DEGerman