Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Spin Wave Theory of Spin 1/2 XY Model with Ring Exchange on a Triangular
  Lattice   We present the linear spin wave theory calculation of the superfluid phase of
a hard-core boson $J$-$K$ model with nearest neighbour exchange $J$ and
four-particle ring-exchange $K$ at half filling on the triangular lattice, as
well as the phase diagrams of the system at zero and finite temperatures. We
find that the pure $J$ model (XY model) which has a well known uniform
superfluid phase with an ordered parameter $M_x=<S_i^x>\neq 0$ at zero
temperature is quickly destroyed by the inclusion of a negative-$K$
ring-exchange interactions, favouring a state with a $(\frac{4\pi}{3}, 0)$
ordering wavevector. We further study the behaviour of the finite-temperature
Kosterlitz-Thouless phase transition ($T_{KT}$) in the uniform superfluid
phase, by forcing the universal quantum jump condition on the
finite-temperature spin wave superfluid density. We find that for $K \textless
0$, the phase boundary monotonically decreases to T=0 at $K/J = -4/3$, where a
phase transition is expected and $T_{KT}$ decreases rapidly while for positive
$K$, $T_{KT}$ reaches a maximum at some $K\neq 0$. It has been shown on a
square lattice using quantum Monte Carlo(QMC) simulations that for small
$K\textgreater 0$ away from the XY point, the zero-temperature spin stiffness
value of the XY model is decreased\cite{F}. Our result seems to agree with this
trend found in QMC simulations.

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The categories of this paper are: chem-ph
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The categories of this paper are: nucl-th
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The categories of this paper are: bayes-an
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The categories of this paper are: cmp-lg
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The categories of this paper are: nlin
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The categories of this paper are: math-ph
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The categories of this paper are: solv-int
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The categories of this paper are: adap-org
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The categories of this paper are: nucl-ex
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The categories of this paper are: alg-geom
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The categories of this paper are: ao-sci
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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: q-bio
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The categories of this paper are: plasm-ph
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The categories of this paper are: acc-phys