Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Nematic ferromagnetism on the Lieb lattice   We discuss the properties of possible ferromagnetic orders on the Lieb
lattice. We show that the presence of a quadratic-flat band crossing point
(QFBCP) at half filling will dramatically affect the magnetic ordering. In the
presence of a weak on-site repulsive interaction, we find the ground state is a
nematic ferromagnetic order with simultaneously broken of time-reversal and
rotational symmetries. When the interaction strength increases, the rotational
symmetry will restore at some critical value, and the system enters a
conventional ferromagnetic regime. We also point out that the spin gap in both
the nematic and conventional ferromagnetic phases is of the order of
interaction. This observation suggests that these magnetic orders can be
realized and detected in cold atomic systems with present technology.

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The categories of this paper are: quant-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: nucl-th
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The categories of this paper are: econ
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The categories of this paper are: solv-int
35
The categories of this paper are: mtrl-th
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The categories of this paper are: math-ph
36
The categories of this paper are: cmp-lg
26
The categories of this paper are: bayes-an
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The categories of this paper are: hep-lat
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The categories of this paper are: comp-gas
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The categories of this paper are: dg-ga
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The categories of this paper are: q-alg
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The categories of this paper are: alg-geom
0
The categories of this paper are: hep-ph
33
The categories of this paper are: plasm-ph