1,503 research outputs found
Theory of Single Electron Spin Relaxation in Si/SiGe Lateral Coupled Quantum Dots
We investigate the spin relaxation induced by acoustic phonons in the
presence of spin-orbit interactions in single electron Si/SiGe lateral coupled
quantum dots. The relaxation rates are computed numerically in single and
double quantum dots, in in-plane and perpendicular magnetic fields. The
deformation potential of acoustic phonons is taken into account for both
transverse and longitudinal polarizations and their contributions to the total
relaxation rate are discussed with respect to the dilatation and shear
potential constants. We find that in single dots the spin relaxation rate
scales approximately with the seventh power of the magnetic field, in line with
a recent experiment. In double dots the relaxation rate is much more sensitive
to the dot spectrum structure, as it is often dominated by a spin hot spot. The
anisotropy of the spin-orbit interactions gives rise to easy passages, special
directions of the magnetic field for which the relaxation is strongly
suppressed. Quantitatively, the spin relaxation rates in Si are typically 2
orders of magnitude smaller than in GaAs due to the absence of the
piezoelectric phonon potential and generally weaker spin-orbit interactions.Comment: 10 pages, 9 figure
Stenochrus portoricensis new to the Czech Republic (Schizomida, Hubbardiidae)
A schizomid, Stenochrus portoricensis Chamberlin, 1922 (family Hubbardiidae), was collected in a greenhouse in Brno. This is the first discovery of a schizomid from the Czech Republic
Theory of anisotropic exchange in laterally coupled quantum dots
The effects of spin-orbit coupling on the two-electron spectra in lateral
coupled quantum dots are investigated analytically and numerically. It is
demonstrated that in the absence of magnetic field the exchange interaction is
practically unaffected by spin-orbit coupling, for any interdot coupling,
boosting prospects for spin-based quantum computing. The anisotropic exchange
appears at finite magnetic fields. A numerically accurate effective spin
Hamiltonian for modeling spin-orbit-induced two-electron spin dynamics in the
presence of magnetic field is proposed.Comment: 4 pages, 3 figures; paper rewritte
Helical nuclear spin order in a strip of stripes in the Quantum Hall regime
We investigate nuclear spin effects in a two-dimensional electron gas in the
quantum Hall regime modeled by a weakly coupled array of interacting quantum
wires. We show that the presence of hyperfine interaction between electron and
nuclear spins in such wires can induce a phase transition, ordering electrons
and nuclear spins into a helix in each wire. Electron-electron interaction
effects, pronounced within the one-dimensional stripes, boost the transition
temperature up to tens to hundreds of millikelvins in GaAs. We predict specific
experimental signatures of the existence of nuclear spin order, for instance
for the resistivity of the system at transitions between different quantum Hall
plateaus.Comment: 16+ pages, 6 figures, updated reference
Majorana bound states in magnetic skyrmions
Magnetic skyrmions are highly mobile nanoscale topological spin textures. We
show, both analytically and numerically, that a magnetic skyrmion of an even
azimuthal winding number placed in proximity to an s-wave superconductor hosts
a zero-energy Majorana bound state in its core, when the exchange coupling
between the itinerant electrons and the skyrmion is strong. This Majorana bound
state is stabilized by the presence of a spin-orbit interaction. We propose the
use of a superconducting tri-junction to realize non-Abelian statistics of such
Majorana bound states.Comment: published versio
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