An adaptive algorithm for n-body field expansions
Weinberg, Martin D.
1998-05-28
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Comment: 3 pages, 2 figures, presented in ICPS-2006
Comment: 4 pages, 3 figures, LaTex Wiley-VCH style (class files included),
accepted for publication in proceedings of PASPS-IV
We have developed a fast, yet highly reproducible method to fabricate
metallic electrodes with nanometer separation using electromigration (EM). We
employ four-terminal instead of two-terminal devices in combination with an
analog feedback to maintain the voltage $U$ over the junction constant. After
the initialization phase ($U < 0.2V), during which the temperature $T$
increases by 80-150 degs C, EM sets in shrinking the wire locally. This quickly
leads to a transition from the diffusive to a quasi-ballistic regime ($0.2V < U
< 0.6V). At the end of this second regime, a gap forms (U > 0.6V). Remarkably,
controlled electromigration is still possible in the quasi-ballistic regime.
Comment: 9 pages, two-column Revtex, 6 figures included
Comment: 33 pages, 17 figures (Review article, 2008 conference of ultrafast
electron microscopy conference and ultrafast sciences)
Comment: 8 pages - minor differences with published version
Comment: Special issue on (nano)characterization of semiconductor materials
and structures
Analytical multi-domain solutions to the dynamical (Landau-Lifshitz-Gilbert)
equation of a one-dimensional ferromagnet including an external magnetic field
and spin-polarized electric current are found using the Hirota bilinearization
method. A standard approach to solve the Landau-Lifshitz equation (without the
Gilbert term) is modified in order to treat the dissipative dynamics. I
establish the relations between the spin interaction parameters (the constants
of exchange, anisotropy, dissipation, external-field intensity, and
electric-current intensity) and the domain-wall parameters (width and velocity)
and compare them to the results of the Walker approximation and micromagnetic
simulations. The domain-wall motion driven by a longitudinal external field is
analyzed with especial relevance to the field-induced collision of two doma...
We report the observation of a reentrant quantum Hall state at the Landau
level filling factor nu = 1 in a two-dimensional hole system confined to a
35-nm-wide (001) GaAs quantum well. The reentrant behavior is characterized by
a weakening and eventual collapse of the nu = 1 quantum Hall state in the
presence of a parallel magnetic field component B||, followed by a
strengthening and reemergence as B|| is further increased. The robustness of
the nu = 1 quantum Hall state during the transition depends strongly on the
charge distribution symmetry of the quantum well, while the magnitude of B||
needed to invoke the transition increases with the total density of the system.
