457 research outputs found
Violation of Onsager symmetry for a ballistic channel Coulomb coupled to a quantum ring
We investigate a scattering of electron which is injected individually into
an empty ballistic channel containing a cavity that is Coulomb coupled to a
quantum ring charged with a single-electron.
We solve the time-dependent Schr\"odinger equation for the electron pair with
an exact account for the electron-electron correlation. Absorption of energy
and angular momentum by the quantum ring is not an even function of the
external magnetic field. As a consequence we find that the electron
backscattering probability is asymmetric in the magnetic field and thus
violates Onsager symmetry.Comment: submitted to EP
Magnetic forces and localized resonances in electron transfer through quantum rings
We study the current flow through semiconductor quantum rings. In high
magnetic field the current is usually injected to the arm of the ring preferred
by classical magnetic forces. However, for narrow magnetic field intervals that
appear periodically on the magnetic field scale the current is injected to the
other arm of the ring. We indicate that the appearance of the anomalous --
non-classical -- current circulation results from Fano interference involving
localized resonant states. The identification of the Fano interference is based
on the comparison of the solution of the scattering problem with the results of
the stabilization method. The latter employs the bound-state type calculations
and allows to extract both the energy of metastable states localized within the
ring and the width of resonances by analysis of the energy spectrum of a finite
size system in function of its length. The Fano resonances involving states of
anomalous current circulation become extremely narrow on both magnetic field
and energy scales. This is consistent with the orientation of the Lorentz force
that tends to keep the electron within the ring and thus increases the lifetime
of the electron localization within the ring. Absence of periodic Fano
resonances in electron transfer probability through a quantum ring containing
an elastic scatterer is also explained.Comment: This paper explains the origins of anomalous (non-classical) current
circulation reported in http://arxiv.org/abs/1004.219
Singlet-triplet avoided crossings and effective factor versus spatial orientation of spin-orbit-coupled quantum dots
We study avoided crossings opened by spin-orbit interaction in the energy
spectra of one- and two-electron anisotropic quantum dots in perpendicular
magnetic field. We find that for simultaneously present Rashba and Dresselhaus
interactions the width of avoided crossings and the effective factor depend
on the dot orientation within (001) crystal plane. The extreme values of these
quantities are obtained for [110] and [10] orientations of the dot.
The width of singlet-triplet avoided crossing changes between these two
orientations by as much as two orders of magnitude. The discussed modulation
results from orientation-dependent strength of the Zeeman interaction which
tends to polarize the spins in the direction of the external magnetic field and
thus remove the spin-orbit coupling effects
Time dependent configuration interaction simulations of spin swap in spin orbit coupled double quantum dots
We perform time-dependent simulations of spin exchange for an electron pair
in laterally coupled quantum dots. The calculation is based on configuration
interaction scheme accounting for spin-orbit (SO) coupling and
electron-electron interaction in a numerically exact way. Noninteracting
electrons exchange orientations of their spins in a manner that can be
understood by interdot tunneling associated with spin precession in an
effective SO magnetic field that results in anisotropy of the spin swap. The
Coulomb interaction blocks the electron transfer between the dots but the spin
transfer and spin precession due to SO coupling is still observed. The
electron-electron interaction additionally induces an appearance of spin
components in the direction of the effective SO magnetic field which are
opposite in both dots. Simulations indicate that the isotropy of the spin swap
is restored for equal Dresselhaus and Rashba constants and properly oriented
dots
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