Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Nonuniform current density and spin accumulation in a 1 {\mu}m thick
  n-GaAs channel   The spin accumulation in an n-GaAs channel produced by spin extraction into a
(Ga,Mn)As contact is measured by cross-sectional imaging of the spin
polarization in GaAs. The spin polarization is observed in a 1 \mum thick
n-GaAs channel with the maximum polarization near the contact edge opposite to
the maximum current density. The one-dimensional model of electron drift and
spin diffusion frequently used cannot explain this observation. It also leads
to incorrect spin lifetimes from Hanle curves with a strong bias and distance
dependence. Numerical simulations based on a two-dimensional drift-diffusion
model, however, reproduce the observed spin distribution quite well and lead to
realistic spin lifetimes.

23
The categories of this paper are: solv-int
25
The categories of this paper are: patt-sol
6
The categories of this paper are: astro-ph
24
The categories of this paper are: dg-ga
13
The categories of this paper are: quant-ph
30
The categories of this paper are: q-alg
18
The categories of this paper are: econ
29
The categories of this paper are: funct-an
3
The categories of this paper are: physics
10
The categories of this paper are: q-bio
14
The categories of this paper are: math-ph
37
The categories of this paper are: supr-con
22
The categories of this paper are: chao-dyn
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The categories of this paper are: alg-geom
27
The categories of this paper are: comp-gas
21
The categories of this paper are: adap-org