Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Electron charge and spin delocalization revealed in the optically probed
  longitudinal and transverse spin dynamics in $n$-GaAs   The evolution of the electron spin dynamics as consequence of carrier
delocalization in $n$-type GaAs is investigated by the recently developed
extended pump-probe Kerr/Faraday rotation spectroscopy. We find that isolated
electrons localized on donors demonstrate a prominent difference between the
longitudinal and transverse spin relaxation rates in magnetic field, which is
almost absent in the metallic phase. The inhomogeneous transverse dephasing
time $T_2^*$ of the spin ensemble strongly increases upon electron
delocalization as a result of motional narrowing that can be induced by
increasing either the donor concentration or the temperature. An unexpected
relation between $T_2^*$ and the longitudinal spin relaxation time $T_1$ is
found, namely that their product is about constant, as explained by the
magnetic field effect on the spin diffusion. We observe a two-stage
longitudinal spin relaxation which suggests the establishment of spin
temperature in the system of exchange-coupled donor-bound electrons.

25
The categories of this paper are: patt-sol
11
The categories of this paper are: hep-lat
19
The categories of this paper are: eess
23
The categories of this paper are: solv-int
29
The categories of this paper are: funct-an
7
The categories of this paper are: hep-th
1
The categories of this paper are: cs
20
The categories of this paper are: acc-phys
37
The categories of this paper are: supr-con
14
The categories of this paper are: math-ph
36
The categories of this paper are: cmp-lg
22
The categories of this paper are: chao-dyn
8
The categories of this paper are: hep-ex
2
The categories of this paper are: math
26
The categories of this paper are: bayes-an
28
The categories of this paper are: alg-geom