  Topological Weyl semimetals (TWS) can be classified as type-I TWS, in which
the density of states vanishes at the Weyl nodes, and type-II TWS where an
electron and a hole pocket meet with finite density of states at the nodal
energy. The dispersions of type-II Weyl nodes are tilted and break Lorentz
invariance, allowing for physical properties distinct from those in a type-I
TWS. We present minimal lattice models for both time-reversal-breaking and
inversion-breaking type-II Weyl semimetals, and investigate their bulk
properties and topological surface states. These lattice models capture the
extended Fermi pockets and the connectivities of Fermi arcs. In addition to the
Fermi arcs, which are topologically protected, we identify surface "track
states" that arise out of the topological Fermi arc states at the transition
from type-I to type-II with multiple Weyl nodes, and persist in the type-II
TWS.
