227,501 research outputs found
Epitaxial Ferromagnetic Nanoislands of Cubic GdN in Hexagonal GaN
Periodic structures of GdN particles encapsulated in a single crystalline GaN
matrix were prepared by plasma assisted molecular beam epitaxy. High resolution
X-ray diffractometery shows that GdN islands, with rock salt structure are
epitaxially oriented to the wurtzite GaN matrix. Scanning transmission electron
microscopy combined with in-situ reflection high energy electron diffraction
allows for the study of island formation dynamics, which occurs after 1.2
monolayers of GdN coverage. Magnetometry reveals two ferromagnetic phases, one
due to GdN particles with Curie temperature of 70K and a second, anomalous room
temperature phase.Comment: 4 pages, 3 figure
Quantum steering of electron wave function in an InAs Y-branch switch
We report experiments on gated Y-branch switches made from InAs ballistic
electron wave guides. We demonstrate that gating modifies the electron wave
functions as well as their interference pattern, causing the anti-correlated,
oscillatory transconductances. Such previously unexpected phenomenon provides
evidence of steering the electron wave function in a multi-channel transistor
structure.Comment: 15 pages, including 3 figure
Sudden jumps and plateaus in the quench dynamics of a Bloch state
We take a one-dimensional tight binding chain with periodic boundary
condition and put a particle in an arbitrary Bloch state, then quench it by
suddenly changing the potential of an arbitrary site. In the ensuing time
evolution, the probability density of the wave function at an arbitrary site
\emph{jumps indefinitely between plateaus}. This phenomenon adds to a former
one in which the survival probability of the particle in the initial Bloch
state shows \emph{cusps} periodically, which was found in the same scenario
[Zhang J. M. and Yang H.-T., EPL, \textbf{114} (2016) 60001]. The plateaus
support the scattering wave picture of the quench dynamics of the Bloch state.
Underlying the cusps and jumps is the exactly solvable, nonanalytic dynamics of
a Luttinger-like model, based on which, the locations of the jumps and the
heights of the plateaus are accurately predicted.Comment: final versio
Asymmetric vortex solitons in nonlinear periodic lattices
We reveal the existence of asymmetric vortex solitons in ideally symmetric
periodic lattices, and show how such nonlinear localized structures describing
elementary circular flows can be analyzed systematically using the
energy-balance relations. We present the examples of rhomboid, rectangular, and
triangular vortex solitons on a square lattice, and also describe novel
coherent states where the populations of clockwise and anti-clockwise vortex
modes change periodically due to a nonlinearity-induced momentum exchange
through the lattice. Asymmetric vortex solitons are expected to exist in
different nonlinear lattice systems including optically-induced photonic
lattices, nonlinear photonic crystals, and Bose-Einstein condensates in optical
lattices.Comment: 4 pages, 5 figure
Differential Phase-contrast Interior Tomography
Differential phase contrast interior tomography allows for reconstruction of
a refractive index distribution over a region of interest (ROI) for
visualization and analysis of internal structures inside a large biological
specimen. In this imaging mode, x-ray beams target the ROI with a narrow beam
aperture, offering more imaging flexibility at less ionizing radiation.
Inspired by recently developed compressive sensing theory, in numerical
analysis framework, we prove that exact interior reconstruction can be achieved
on an ROI via the total variation minimization from truncated differential
projection data through the ROI, assuming a piecewise constant distribution of
the refractive index in the ROI. Then, we develop an iterative algorithm for
the interior reconstruction and perform numerical simulation experiments to
demonstrate the feasibility of our proposed approach
On the bound of first excursion probability
Boundary values for first excursion probability as related to reliability and safe performance of mechanical and structural system
- …