Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Ultrafast Spin Dynamics in Optically Excited Bulk GaAs at Low
  Temperatures   This paper presents a study of electron spin dynamics in bulk GaAs at low
temperatures for elevated optical excitation conditions. Our time-resolved
Faraday rotation measurements yield sub-nanosecond electron spin
dephasing-times over a wide range of n-doping concentrations in quantitative
agreement with a microscopic treatment of electron spin dynamics. The
calculation shows the occurrence and breakdown of motional narrowing for spin
dephasing under elevated excitation conditions. We also find a peak of the spin
dephasing time around a doping density for which, under lower excitation
conditions, a metal-insulator transition occurs. However, the experimental
results for high excitation can be explained without a metal-insulator
transition. We therefore attribute the peak in spin-dephasing times to the
influence of screening and scattering on the spin-dynamics of the excited
electrons.

35
The categories of this paper are: mtrl-th
21
The categories of this paper are: adap-org
25
The categories of this paper are: patt-sol
28
The categories of this paper are: alg-geom
29
The categories of this paper are: funct-an
32
The categories of this paper are: atom-ph
11
The categories of this paper are: hep-lat
22
The categories of this paper are: chao-dyn
12
The categories of this paper are: nucl-th
3
The categories of this paper are: physics
27
The categories of this paper are: comp-gas
30
The categories of this paper are: q-alg
15
The categories of this paper are: nucl-ex
10
The categories of this paper are: q-bio
8
The categories of this paper are: hep-ex
2
The categories of this paper are: math