Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Quantum fluctuations in the effective pseudospin-1/2 model for magnetic
  pyrochlore oxides   The effective quantum pseudospin-1/2 model for interacting rare-earth
magnetic moments, which are locally described with atomic doublets, is studied
theoretically for magnetic pyrochlore oxides. It is derived microscopically for
localized Pr^{3+} 4f moments in Pr_2TM_2O_7 (TM = Zr, Sn, Hf, and Ir) by
starting from the atomic non-Kramers magnetic doublets and performing the
strong-coupling perturbation expansion of the virtual electron transfer between
the Pr 4f and O 2p electrons. The most generic form of the nearest-neighbor
anisotropic superexchange pseudospin-1/2 Hamiltonian is also constructed from
the symmetry properties, which is applicable to Kramers ions Nd^{3+}, Sm^{3+},
and Yb^{3+} potentially showing large quantum effects. The effective model is
then studied by means of a classical mean-field theory and the exact
diagonalization on a single tetrahedron and on a 16-site cluster. These
calculations reveal appreciable quantum fluctuations leading to quantum phase
transitions to a quadrupolar state as a melting of spin ice for the Pr^{3+}
case. The model also shows a formation of cooperative quadrupole moment and
pseudospin chirality on tetrahedrons. A sign of a singlet quantum spin ice is
also found in a finite region in the space of coupling constants. The relevance
to the experiments is discussed.

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The categories of this paper are: chem-ph
28
The categories of this paper are: alg-geom
1
The categories of this paper are: cs
27
The categories of this paper are: comp-gas
18
The categories of this paper are: econ
19
The categories of this paper are: eess
15
The categories of this paper are: nucl-ex
33
The categories of this paper are: plasm-ph
14
The categories of this paper are: math-ph
32
The categories of this paper are: atom-ph
17
The categories of this paper are: q-fin
12
The categories of this paper are: nucl-th
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The categories of this paper are: mtrl-th
30
The categories of this paper are: q-alg
3
The categories of this paper are: physics
36
The categories of this paper are: cmp-lg