Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Importance of anisotropic exchange interactions in honeycomb iridates.
  Minimal model for zigzag antiferromagnetic order in Na$_2$IrO$_3$   In this work, we investigate the microscopic nature of the magnetism in
honeycomb iridium-based systems by performing a systematic study of how the
effective magnetic interactions in these compounds depend on various electronic
microscopic parameters. We show that the minimal model describing the magnetism
in A$_2$IrO$_3$ includes both isotropic and anisotropic Kitaev-type
spin-exchange interactions between nearest and next-nearest neighbor Ir ions,
and that the magnitude of the Kitaev interaction between next-nearest neighbor
Ir magnetic moments is comparable with nearest neighbor interactions. We also
find that, while the Heisenberg and the Kitaev interactions between nearest
neighbors are correspondingly antiferro- and ferromagnetic, they both change
sign for the next-nearest neighbors. Using classical Monte Carlo simulations we
examine the magnetic phase diagram of the derived super-exchange model.
Zigzag-type antiferromagnetic order is found to occupy a large part of the
phase diagram of the model and, for ferromagnetic next-nearest neighbor
Heisenberg interaction relevant for Na$_2$IrO$_3$, it can be stabilized even in
the absence of third nearest neighbor coupling. Our results suggest that a
natural physical origin of the zigzag phase experimentally observed in
Na$_2$IrO$_3$ is due to the interplay of the Kitaev anisotropic interactions
between nearest and next-nearest neighbors.

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The categories of this paper are: astro-ph
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The categories of this paper are: math
23
The categories of this paper are: solv-int
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The categories of this paper are: cmp-lg
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The categories of this paper are: acc-phys
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The categories of this paper are: dg-ga
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The categories of this paper are: nlin
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The categories of this paper are: hep-ex
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The categories of this paper are: physics
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The categories of this paper are: supr-con
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The categories of this paper are: atom-ph
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The categories of this paper are: hep-ph
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The categories of this paper are: math-ph
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The categories of this paper are: q-fin
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The categories of this paper are: stat
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The categories of this paper are: adap-org