  There is an interesting proposal that the long-range Coulomb interaction in
suspended graphene can generate a dynamical gap, which leads to a
semimetal-insulator phase transition. We revisit this problem by solving the
self-consistent Dyson-Schwinger equations of wave function renormalization and
fermion gap. In order to satisfy the Ward identity, a suitable vertex function
is introduced. The impacts of singular velocity renormalization and dynamical
screening on gap generation are both included in this formalism, and prove to
be very important. We obtain a critical interaction strength, $3.2 < \alpha_{c}
< 3.3$, which is larger than the physical value $\alpha = 2.16$ for suspended
graphene. It therefore turns out that suspended graphene is a semimetal, rather
than insulator, at zero temperature.
