Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Bose-Einstein condensation of triplons in the S=1 tetramer
  antiferromagnet K2Ni2(MoO4)3: A compound close to quantum critical point   The structure of K2Ni2(MoO4)3 consists of S=1 tetramers formed by Ni^{2+}
ions. The magnetic susceptibility chi(T) and specific heat Cp(T) data on a
single crystal show a broad maximum due to the low-dimensionality of the system
with short-range spin correlations. A sharp peak is seen in chi(T) and Cp(T) at
about 1.13 K, well below the broad maximum. This is an indication of magnetic
long-range order i.e., the absence of spin-gap in the ground state.
Interestingly, the application of a small magnetic field (H>0.1 T) induces
magnetic behavior akin to Bose-Einstein condensation (BEC) of triplon
excitations observed in some spin-gap materials. Our results demonstrate that
the temperature-field (T-H) phase boundary follows a power-law
(T-T_{N})propotional to H^(1/alpha) with the exponent 1/alpha close to 2/3, as
predicted for BEC scenario. The observation of BEC of triplon excitations in
small H infers that K2Ni2(MoO4)3 is located in the proximity of a quantum
critical point, which separates the magnetically ordered and spin-gap regions
of the phase diagram.

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The categories of this paper are: eess
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The categories of this paper are: adap-org
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The categories of this paper are: math-ph
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The categories of this paper are: q-alg
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The categories of this paper are: cs
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The categories of this paper are: nucl-th
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The categories of this paper are: hep-th
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The categories of this paper are: supr-con
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The categories of this paper are: solv-int
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The categories of this paper are: q-bio
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The categories of this paper are: comp-gas
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The categories of this paper are: funct-an
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The categories of this paper are: quant-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: econ
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The categories of this paper are: cmp-lg