Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Are the double Fermi arcs of Dirac semimetals topologically protected?   Motivated by recent experiments probing anomalous surface states of Dirac
semimetals (DSMs) Na$_3$Bi and Cd$_3$As$_2$, we raise the question posed in the
title. We find that, in marked contrast to Weyl semimetals, the gapless surface
states of DSMs are not topologically protected in general, except on
time-reversal-invariant planes of surface Brillouin zone. We first demonstrate
this in a minimal $4$-band model with a pair of Dirac nodes at ${\bf
k}=(0,0,\pm Q)$, where gapless states on the side surfaces are protected only
near $k_z=0$. We then validate our conclusions about the absence of a
topological invariant protecting double Fermi arcs in DSMs using a K-theory
analysis for space groups of Na$_3$Bi and Cd$_3$As$_2$. Generically, the arcs
deform into a Fermi pocket, similar to {{the surface states of a topological
insulator (TI), and this can merge into the}} projection of bulk Dirac Fermi
surfaces as the chemical potential is varied. We make sharp predictions for the
doping-dependence of the surface states of a DSM that can be tested by ARPES
and quantum oscillation experiments.

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The categories of this paper are: atom-ph
6
The categories of this paper are: astro-ph
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The categories of this paper are: funct-an
10
The categories of this paper are: q-bio
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The categories of this paper are: acc-phys
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The categories of this paper are: nucl-ex
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The categories of this paper are: dg-ga
1
The categories of this paper are: cs
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The categories of this paper are: bayes-an
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The categories of this paper are: supr-con
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The categories of this paper are: econ
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The categories of this paper are: physics
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The categories of this paper are: patt-sol
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The categories of this paper are: cmp-lg
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The categories of this paper are: plasm-ph
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The categories of this paper are: solv-int