Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Quasiclassical magnetic order and its loss in a spin-1/2 Heisenberg
  antiferromagnet on a triangular lattice with competing bonds   We use the coupled cluster method (CCM) to study the zero-temperature
ground-state (GS) properties of a spin-1/2 $J_{1}$--$J_{2}$ Heisenberg
antiferromagnet on a triangular lattice with competing nearest-neighbor and
next-nearest-neighbor exchange couplings $J_{1}>0$ and $J_{2} \equiv \kappa
J_{1}>0$, respectively, in the window $0 \leq \kappa < 1$. The classical
version of the model has a single GS phase transition at $\kappa^{cl}=$1/8 in
this window from a phase with 3-sublattice antiferromagnetic (AFM)
120$^{\circ}$ N\'{e}el order for $\kappa < \kappa^{cl}$ to an infinitely
degenerate family of 4-sublattice AFM N\'{e}el phases for $\kappa >
\kappa^{cl}$. This classical accidental degeneracy is lifted by quantum
fluctuations, which favor a 2-sublattice AFM striped phase. For the quantum
model we work directly in the thermodynamic limit of an infinite number of
spins, with no consequent need for any finite-size scaling analysis of our
results. We perform high-order CCM calculations within a well-controlled
hierarchy of approximations, which we show how to extrapolate to the exact
limit. In this way we find results for the case $\kappa = 0$ of the spin-1/2
model for the GS energy per spin, $E/N=-0.5521(2)J_{1}$, and the GS magnetic
order parameter, $M=0.198(5)$, which are among the best available. For the
spin-1/2 $J_{1}$--$J_{2}$ model we find that the classical transition at
$\kappa=\kappa^{cl}$ is split into two quantum phase transition at
$\kappa^{c}_{1}=0.060(10)$ and $\kappa^{c}_{2}=0.165(5)$. The two
quasiclassical AFM states (viz., the 120$^{\circ}$ N\'{e}el state and the
striped state) are found to be the stable GS phases in the regime $\kappa <
\kappa^{c}_{1}$ and $\kappa > \kappa^{c}_{2}$, respectively, while in the
intermediate regimes $\kappa^{c}_{1} < \kappa < \kappa^{c}_{2}$ the stable GS
phase has no evident long-range magnetic order.

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The categories of this paper are: quant-ph
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The categories of this paper are: q-bio
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The categories of this paper are: q-alg
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The categories of this paper are: hep-ex
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The categories of this paper are: ao-sci
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The categories of this paper are: funct-an
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The categories of this paper are: astro-ph
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The categories of this paper are: nucl-th
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The categories of this paper are: acc-phys
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The categories of this paper are: physics
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The categories of this paper are: q-fin
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The categories of this paper are: cmp-lg
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The categories of this paper are: math
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The categories of this paper are: atom-ph
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The categories of this paper are: supr-con
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The categories of this paper are: chao-dyn