Workshop book - Physikzentrum der RWTH Aachen - RWTH Aachen ...

Posters Monday February 4
Poster 17:
Rashba spin-orbit interaction in a quantum wire superlattice
Sigurdur I. Erlingsson
We study the effects of a longitudinal periodic potential on a parabolic
quantum wire, and long quantum point contacts, defined in a two-dimensional
electron gas with Rashba spin-orbit interaction. For an infinite wire
superlattice we find that the energy gaps are shifted away from the usual
Bragg planes due to the Rashba spin-orbit interaction. We have also calculated
the charge conductance through a periodic potential of a finite length
via the nonequilibrium Green’s function method combined with the Landauer
formalism. We find dips in the conductance that correspond well to
the energy gaps of the infinite wire superlattice. From the infinite wire energy
dispersion, we derive an equation relating the location of the conductance
dips as a function of the Fermi energy to the Rashba spin-orbit coupling
strength. We propose that the strength of the Rashba spin-orbit interaction
can be extracted via a charge conductance measurement.
Poster 18:
Electronic states in a cylindrical nanowire in magnetic and electric fields
Andrei Manolescu
Single particle states of electrons situated on a closed cylindrical surface of
radius 30-100 nm are calculated. The length of the cylinder may be either
infinite or finite. In the presence of a magnetic field uniform in space, but perpendicular
to the longitudinal axis of the cylinder, the orbital effects depend
on the radial component of the magnetic field. For a sufficiently strong field,
when the magnetic length becomes comparable to the radius of the cylinder,
the orbital motion corresponds to closed cyclotron orbits in the regions with
strong radial field, but to open quasi one-dimensional snaking orbits in the
regions where the radial field vanishes and changes sign. The energy of the
cyclotron states increases with the magnetic field relatively to the energy of
the snaking states such that at high magnetic fields the electrons concentrate
around the snaking orbits. The spin of the electron is included via Zeeman
and Rashba spin-orbit effects. A uniform electric field perpendicular to the
cylinder is also considered, as being produced by a metallic electrode placed
near the cylinder. In this case the spin-orbit coupling becomes anisotropic.
Attempts to include Coulomb effects in the Hartree-Fock approximation are
discussed.
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