7,145 research outputs found
Optical properties of (In,Ga)As capped InAs quantum dots grown on [11k] substrates
Using three-dimensional k.p calculation including strain and
piezoelectricity, we showed that the size of the quantum dot (QD) in the growth
direction determines the influence of the (In,Ga)As capping layer on the
optical properties of [11k] grown InAs QDs, where k=1,2,3. For flat dots,
increase of In concentration in the capping layer leads to a decrease of the
transition energy, as is the case of [001] grown QDs, whereas for large dots an
increase of the In concentration in the capping layer is followed by an
increase of the transition energy up to a critical concentration of In, after
which the optical transition energy starts to decrease
Klein paradox for a pn junction in multilayer graphene
Charge carriers in single and multilayered graphene systems behave as chiral
particles due to the particular lattice symmetry of the crystal. We show that
the interplay between the meta-material properties of graphene multilayers and
the pseudospinorial properties of the charge carriers result in the occurrence
of Klein and anti-Klein tunneling for rhombohedral stacked multilayers. We
derive an algebraic formula predicting the angles at which these phenomena
occur and support this with numerical calculations for systems up to four
layers. We present a decomposition of an arbitrarily stacked multilayer into
pseudospin doublets that have the same properties as rhombohedral systems with
a lower number of layers.Comment: 5 pages, 4 figure
Ballistic spin transport through electronic stub tuners: spin precession, selection, and square-wave transmission
Ballistic spin transport is studied through electronic tuners with double
stubs attached to them. The spins precess due to the spin-orbit interaction.
Injected polarized spins can exit the structure polarized in the opposite
direction. A nearly square-wave spin transmission, with values 1 and 0, can be
obtained using a periodic system of symmetric stubs and changing their length
or width. The gaps in the transmission can be widened using asymmetric stubs.
An additional modulation is obtained upon combining stub structures with
different values of the spin-orbit strength.Comment: 3 pages, 4 figure
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