28,463 research outputs found
Electron Band Structure in a Two Dimensional Periodic Magnetic Field
In this paper we study the energy spectrum of a two dimensional electron gas
(2DEG) in a two dimensional periodic magnetic field. Both a square magnetic
lattice and a triangular one are considered. We consider the general case where
the magnetic field in a cell can be of any shape. A general feature of the band
structure is bandwidth oscillation as a function of the Landau index. A
triangular magnetic lattice on a 2DEG can be realized by the vortex lattice of
a superconductor film coated on top of a heterojunction. Our calculation
indicates a way of relating the energy spectrum of the 2DEG to the vortex
structure. We have also derived conditions under which the effects of a weak
magnetic modulation, periodic or not, may be reproduced by an electric
potential modulation, and vice versa.Comment: 16 pages in TeX and 5 uuencoded figure
Two-component model for the chemical evolution of the Galactic disk
In the present paper, we introduce a two-component model of the Galactic disk
to investigate its chemical evolution. The formation of the thick and thin
disks occur in two main accretion episodes with both infall rates to be
Gaussian. Both the pre-thin and post-thin scenarios for the formation of the
Galactic disk are considered. The best-fitting is obtained through
-test between the models and the new observed metallicity distribution
function of G dwarfs in the solar neighbourhood (Hou et al 1998). Our results
show that post-thin disk scenario for the formation of the Galactic disk should
be preferred. Still, other comparison between model predictions and
observations are given.Comment: 23 pages, 7 figure
Anisotropic superconducting properties of aligned SmLaFeAsOF microcrystalline powder
The SmLaFeAsOF compound is a quasi-2D
layered superconductor with a superconducting transition temperature T = 52
K. Due to the Fe spin-orbital related anisotropic exchange coupling
(antiferromagnetic or ferromagnetic fluctuation), the tetragonal
microcrystalline powder can be aligned at room temperature using the
field-rotation method where the tetragonal -plane is parallel to the
aligned magnetic field B and -axis along the rotation axis.
Anisotropic superconducting properties with anisotropic diamagnetic ratio
2.4 + 0.6 was observed from low field susceptibility
(T) and magnetization M(B). The anisotropic low-field phase diagram
with the variation of lower critical field gives a zero-temperature penetration
depth (0) = 280 nm and (0) = 120 nm. The magnetic
fluctuation used for powder alignment at 300 K may be related with the pairing
mechanism of superconductivity at lower temperature.Comment: 4 pages, 6 figure
Parallel Computing on a PC Cluster
The tremendous advance in computer technology in the past decade has made it
possible to achieve the performance of a supercomputer on a very small budget.
We have built a multi-CPU cluster of Pentium PC capable of parallel
computations using the Message Passing Interface (MPI). We will discuss the
configuration, performance, and application of the cluster to our work in
physics.Comment: 3 pages, uses Latex and aipproc.cl
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