3D quantum anomalous Hall effect in a node-line semimetal

We address the role of interactions for spinless fermions
in the hyperhoneycomb lattice, a three dimensional (3D) structure
where all sites have a planar trigonal connectivity. For weak repulsion,
the system is a node-line semimetal. In the presence of strong interactions,
we show that the system can be unstable to a 3D quantum anomalous
Hall phase with loop currents that break time reversal symmetry, as
in the Haldane model. We find that the low energy excitations of this
state are Weyl fermions connected by surface Fermi arcs [1]. We show that
the 3D anomalous Hall conductivity is $e^{2}/(\sqrt{3}ah)$, with
$a$ the lattice constant.
[1] S. W. Kim et al. arXiv:1708.02965 (2017).