1,035 research outputs found
InGaAs/GaAs/alkanethiolate radial superlattices: Experimental
A radial InGaAs/GaAs/1-hexadecanethiol superlattice is fabricated by the
roll-up of a strained InGaAs/GaAs bilayer passivated with a molecular
self-assembled monolayer. Our technique allows the formation of multi-period
inorganic/organic hybrid heterostructures. This paper contains the detailed
experimental description of how to fabricate these structures.Comment: 2 pages, no figures, Version 2; minor changes (fixed typos and update
references
Asymmetric I-V characteristics and magnetoresistance in magnetic point contacts
We present a theoretical study of the transport properties of magnetic point
contacts under bias. Our calculations are based on the Keldish's
non-equilibrium Green's function formalism combined with a self-consistent
empirical tight-binding Hamiltonian, which describes both strong ferromagnetism
and charging effects. We demonstrate that large magnetoresistance solely due to
electronic effects can be found when a sharp domain wall forms inside a
magnetic atomic-scale point contact. Moreover we show that the symmetry of the
- characteristic depends on the position of the domain wall in the
constriction. In particular diode-like curves can arise when the domain wall is
placed off-center within the point contact, although the whole structure does
not present any structural asymmetry.Comment: 7 figures, submitted to PR
Control of spin in quantum dots with non-Fermi liquid correlations
Spin effects in the transport properties of a quantum dot with spin-charge
separation are investigated. It is found that the non-linear transport spectra
are dominated by spin dynamics. Strong spin polarization effects are observed
in a magnetic field. They can be controlled by varying gate and bias voltages.
Complete polarization is stable against interactions. When polarization is not
complete, it is power-law enhanced by non-Fermi liquid effects.Comment: 4 pages, 4 figure
Structural and magnetic properties of an InGaAs/FeSi superlattice in cylindrical geometry
The structure and the magnetic properties of an InGaAs/Fe3Si superlattice in
a cylindrical geometry are investigated by electron microscopy techniques,
x-ray diffraction and magnetometry. To form a radial superlattice, a
pseudomorphic InGaAs/Fe3As bilayer has been released from its substrate
self-forming into a rolled-up microtube. Oxide-free interfaces as well as areas
of crystalline bonding are observed and an overall lattice mismatch between
succeeding layers is determined. The cylindrical symmetry of the final radial
superlattice shows a significant effect on the magnetization behavior of the
rolled-up layers
Electron Spin Decoherence in Bulk and Quantum Well Zincblende Semiconductors
A theory for longitudinal (T1) and transverse (T2) electron spin coherence
times in zincblende semiconductor quantum wells is developed based on a
non-perturbative nanostructure model solved in a fourteen-band restricted basis
set. Distinctly different dependences of coherence times on mobility,
quantization energy, and temperature are found from previous calculations.
Quantitative agreement between our calculations and measurements is found for
GaAs/AlGaAs, InGaAs/InP, and GaSb/AlSb quantum wells.Comment: 11 pages, 3 figure
Coordination and chemical effects on the structural, electronic and magnetic properties in Mn pnictides
Simple structures of MnX binary compounds, namely hexagonal NiAs and
zincblende, are studied as a function of the anion (X = Sb, As, P) by means of
the all-electron FLAPW method within local spin density and generalized
gradient approximations. An accurate analysis of the structural, electronic and
magnetic properties reveals that the cubic structure greatly favours the
magnetic alignment in these compounds leading to high magnetic moments and
nearly half-metallic behaviour for MnSb and MnAs. The effect of the anion
chemical species is related to both its size and the possible hybridization
with the Mn states; both contributions are seen to hinder the magnitude of
the magnetic moment for small and light anions. Our results are in very good
agreement with experiment - where available - and show that the generalized
gradient approximation is essential to correctly recover both the equilibrium
volume and magnetic moment.Comment: 18 pages and 4 figures, Latex-file, submitted to Phys.Rev.
Towards New Half-Metallic Systems: Zinc-Blende Compounds of Transition Elements with N, P, As, Sb, S, Se, and Te
We report systematic first-principles calculations for ordered zinc-blende
compounds of the transition metal elements V, Cr, Mn with the sp elements N, P,
As, Sb, S, Se, Te, motivated by recent fabrication of zinc-blende CrAs, CrSb,
and MnAs. They show ferromagnetic half-metallic behavior for a wide range of
lattice constants. We discuss the origin and trends of half-metallicity,
present the calculated equilibrium lattice constants, and examine the
half-metallic behavior of their transition element terminated (001) surfaces.Comment: 2nd Version: lattice constants calculations added, text revise
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