Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Low-energy Majorana states in spin-liquid transitions in a
  three-dimensional Kitaev model   A three-dimensional Kitaev model on a hyperhoneycomb lattice is investigated
numerically at finite temperature. The Kitaev model is one of the solvable
quantum spin models, where the ground state is given by gapped and gapless spin
liquids, depending on the anisotropy of the interactions. This model can be
rewritten as a free Majorana fermion system coupled with $Z_2$ variables. The
density of states of Majorana fermions shows an excitation gap in the gapped
region, while it is semimetallic in the gapless region reflecting the Dirac
node. Performing the Monte Carlo simulation, we calculate the temperature
dependence of the Majorana spectra. We find that the semimetallic dip is filled
up as temperature increases in the gapless region, but surprisingly, the
spectrum develops an excitation gap in the region near the gapless-gapped
boundary. Such changes of the low-energy spectrum appear sharply at the
transition temperature from the spin liquid to the paramagnetic state. The
results indicate that thermal fluctuations of the $Z_2$ fields significantly
influence the low-energy state of Majorana fermions, especially in the spin
liquid formation.

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The categories of this paper are: nlin
13
The categories of this paper are: quant-ph
19
The categories of this paper are: eess
37
The categories of this paper are: supr-con
27
The categories of this paper are: comp-gas
30
The categories of this paper are: q-alg
24
The categories of this paper are: dg-ga
10
The categories of this paper are: q-bio
25
The categories of this paper are: patt-sol
32
The categories of this paper are: atom-ph
16
The categories of this paper are: stat
18
The categories of this paper are: econ
3
The categories of this paper are: physics
22
The categories of this paper are: chao-dyn
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The categories of this paper are: math
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The categories of this paper are: hep-ex