  The type-II Weyl/Dirac fermions are a generalization of conventional or
type-I Weyl/Dirac fermions, whose conic spectrum is tilted such that the Fermi
surface becomes lines in two dimensions, and surface in three dimensions rather
than discrete points of the conventional Weyl/Dirac fermions. The
mass-independent renormalization group calculations show that the tilting
parameter decreases monotonically with respect to the length scale, which leads
to a transition from two dimensional type-II Weyl/Dirac fermions to the type-I
ones. Because of the non-trivial Fermi surface, a photon gains a finite mass
partially via the chiral anomaly, leading to the strong screening effect of the
Weyl/Dirac fermions. Consequently, anisotropic type-II Dirac semimetals become
stable against the Coulomb interaction. This work provides deep insight into
the interplay between the geometry of Fermi surface and the Coulomb
interaction.
