Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Spin transport of indirect excitons   Spin transport of indirect excitons in GaAs/AlGaAs coupled quantum wells was
observed by measuring the spatially resolved circular polarization of exciton
emission. Exciton spin transport over several microns originates from a long
spin relaxation time and long lifetime of indirect excitons.

20
The categories of this paper are: acc-phys
13
The categories of this paper are: quant-ph
16
The categories of this paper are: stat
35
The categories of this paper are: mtrl-th
25
The categories of this paper are: patt-sol
2
The categories of this paper are: math
21
The categories of this paper are: adap-org
10
The categories of this paper are: q-bio
7
The categories of this paper are: hep-th
12
The categories of this paper are: nucl-th
22
The categories of this paper are: chao-dyn
32
The categories of this paper are: atom-ph
37
The categories of this paper are: supr-con
33
The categories of this paper are: plasm-ph
18
The categories of this paper are: econ
23
The categories of this paper are: solv-int