Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Order-by-disorder and spin-orbital liquids in a distorted
  Heisenberg-Kitaev model   The microscopic modeling of spin-orbit entangled $j=1/2$ Mott insulators such
as the layered hexagonal Iridates Na$_2$IrO$_3$ and Li$_2$IrO$_3$ has spurred
an interest in the physics of Heisenberg-Kitaev models. Here we explore the
effect of lattice distortions on the formation of the collective spin-orbital
states which include not only conventionally ordered phases but also gapped and
gapless spin-orbital liquids. In particular, we demonstrate that in the
presence of spatial anisotropies of the exchange couplings conventionally
ordered states are formed through an order-by-disorder selection which is not
only sensitive to the type of exchange anisotropy but also to the relative
strength of the Heisenberg and Kitaev couplings. The spin-orbital liquid phases
of the Kitaev limit -- a gapless phase in the vicinity of spatially isotropic
couplings and a gapped Z$_2$ phase for a dominant spatial anisotropy of the
exchange couplings -- show vastly different sensitivities to the inclusion of a
Heisenberg exchange. While the gapless phase is remarkably stable, the gapped
Z$_2$ phase quickly breaks down in what might be a rather unconventional phase
transition driven by the simultaneous condensation of its elementary
excitations.

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The categories of this paper are: solv-int
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The categories of this paper are: hep-lat
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The categories of this paper are: eess
34
The categories of this paper are: chem-ph
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The categories of this paper are: comp-gas
36
The categories of this paper are: cmp-lg
8
The categories of this paper are: hep-ex
0
The categories of this paper are: hep-ph
32
The categories of this paper are: atom-ph
5
The categories of this paper are: gr-qc
17
The categories of this paper are: q-fin
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The categories of this paper are: acc-phys
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The categories of this paper are: math-ph
7
The categories of this paper are: hep-th
9
The categories of this paper are: nlin
28
The categories of this paper are: alg-geom