Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Electrical polarization of nuclear spins in a breakdown regime of
  quantum Hall effect   We have developed a method for electrical polarization of nuclear spins in
quantum Hall systems. In a breakdown regime of odd-integer quantum Hall effect
(QHE), excitation of electrons to the upper Landau subband with opposite spin
polarity dynamically polarizes nuclear spins through the hyperfine interaction.
The polarized nuclear spins in turn accelerate the QHE breakdown, leading to
hysteretic voltage-current characteristics of the quantum Hall conductor.

9
The categories of this paper are: nlin
34
The categories of this paper are: chem-ph
22
The categories of this paper are: chao-dyn
7
The categories of this paper are: hep-th
13
The categories of this paper are: quant-ph
19
The categories of this paper are: eess
29
The categories of this paper are: funct-an
3
The categories of this paper are: physics
33
The categories of this paper are: plasm-ph
37
The categories of this paper are: supr-con
24
The categories of this paper are: dg-ga
11
The categories of this paper are: hep-lat
15
The categories of this paper are: nucl-ex
1
The categories of this paper are: cs
18
The categories of this paper are: econ
28
The categories of this paper are: alg-geom