Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Nuclear magnetization in gallium arsenide quantum dots at zero magnetic
  field   Optical and electrical control of the nuclear spin system allows enhancing
the sensitivity of NMR applications and spin-based information storage and
processing. Dynamic nuclear polarization in semiconductors is commonly achieved
in the presence of a stabilizing external magnetic field. Here we report
efficient optical pumping of nuclear spins at zero magnetic field in strain
free GaAs quantum dots. The strong interaction of a single, optically injected
electron spin with the nuclear spins acts as a stabilizing, effective magnetic
field (Knight field) on the nuclei. We optically tune the Knight field
amplitude and direction. In combination with a small transverse magnetic field,
we are able to control the longitudinal and transverse component of the nuclear
spin polarization in the absence of lattice strain i.e. nuclear quadrupole
effects, as reproduced by our model calculations.

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The categories of this paper are: astro-ph
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The categories of this paper are: q-fin
13
The categories of this paper are: quant-ph
22
The categories of this paper are: chao-dyn
25
The categories of this paper are: patt-sol
21
The categories of this paper are: adap-org
32
The categories of this paper are: atom-ph
28
The categories of this paper are: alg-geom
33
The categories of this paper are: plasm-ph
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The categories of this paper are: gr-qc
30
The categories of this paper are: q-alg
31
The categories of this paper are: ao-sci
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The categories of this paper are: stat
36
The categories of this paper are: cmp-lg
29
The categories of this paper are: funct-an
24
The categories of this paper are: dg-ga