2,739 research outputs found
Interface relaxation and electrostatic charge depletion in the oxide heterostructure LaAlO3/SrTiO3
Performing an analysis within density functional theory, we develop insight
into the structural and electronic properties of the oxide heterostructure
LaAlO3/SrTiO3. Electrostatic surface effects are decomposed from the internal
lattice distortion in order to clarify their interplay. We first study the
interface relaxation by a multi-layer system without surface, and the surface
effects, separately, by a substrate-film system. While elongation of the TiO6
octahedra at the interface enhances the metallicity, reduction of the film
thickness has the opposite effect due to a growing charge depletion. The
interplay of these two effects, as reflected by the full lattice relaxation in
the substrate-film system, however, strongly depends on the film thickness. An
inversion of the TiO6 distortion pattern for films thinner than four LaAlO3
layers results in an insulating state.Comment: 10 pages, 7 figures, accepted by Europhysics Letter
Self-assembled Pt nanowires on Ge(001): Relaxation effects
Absorption of Pt on the Ge(001) surface results in stable self-organized Pt
nanowires, extending over some hundred nanometers. Based on band structure
calculations within density functional theory and the generalized gradient
approximation, the structural relaxation of the Ge--Pt surface is investigated.
The surface reconstruction pattern obtained agrees well with findings from
scanning tunneling microscopy. In particular, strong Pt--Pt dimerization is
characteristical for the nanowires. The surface electronic structure is
significantly perturbed due to Ge--Pt interaction, which induces remarkable
shifts of Ge states towards the Fermi energy. As a consequence, the topmost Ge
layers are subject to a metal-insulator transition.Comment: 4 pages, 2 figures, final version accepted by Europhys. Lett., minor
modifications of the tex
Magnetic ordering in the striped nickelate La5/3Sr1/3NiO4: A band structure point of view
We report on a comprehensive study of the electronic and magnetic structure
of the striped nickelate La5/3Sr1/3NiO4. The investigation is carried out using
band structure calculations based on density functional theory. A magnetic
structure compatible with experiment is obtained from spin-polarized
calculations within the generalized gradient approximation (GGA), whereas
inclusion of a local Coulomb interaction in the LDA+U framework results in a
different ground state. The influence of the various interaction parameters is
discussed in detail.Comment: 5 pages, 4 figures, 2 tables, accepted by Europhys. Let
Stationary distributions of sums of marginally chaotic variables as renormalization group fixed points
We determine the limit distributions of sums of deterministic chaotic
variables in unimodal maps assisted by a novel renormalization group (RG)
framework associated to the operation of increment of summands and rescaling.
In this framework the difference in control parameter from its value at the
transition to chaos is the only relevant variable, the trivial fixed point is
the Gaussian distribution and a nontrivial fixed point is a multifractal
distribution with features similar to those of the Feigenbaum attractor. The
crossover between the two fixed points is discussed and the flow toward the
trivial fixed point is seen to consist of a sequence of chaotic band mergers.Comment: 7 pages, 2 figures, to appear in Journal of Physics: Conf.Series
(IOP, 2010
Chemical Bonding and Charge Distribution at Metallic Nanocontacts
We present results of electronic structure calculations for aluminium
contacts of atomic size, based on density functional theory and the local
density approximation. Addressing the atomic orbitals at the neck of the
nanocontact, we find that the local band structure deviates strongly from bulk
fcc aluminium. In particular, hybridization between Al 3s and 3p states is
fully suppressed due to directed bonds at the contact. Moreover, a charge
transfer of 0.6 electrons off the contact aluminium site is found. Both the
suppressed hybridization and the violated charge neutrality are characteristic
features of metallic nanocontacts. This fact has serious consequences for
models aiming at a microscopic description of transport properties.Comment: 6 pages, 3 figures, accepted by Chemical Physics Letter
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