  In this work, we identify a new class of Z2 topological insulator protected
by non-symmorphic crystalline symmetry, dubbed a "topological non-symmorphic
crystalline insulator". We construct a concrete tight-binding model with the
non-symmorphic space group pmg and confirm the topological nature of this model
by calculating topological surface states and defining a Z2 topological
invariant. Based on the projective representation theory, we extend our
discussion to other non-symmorphic space groups that allows to host topological
non-symmorphic crystalline insulators.
