  The search for large band gap systems with dissipationless edge states is
essential to developing materials that function under a wide range of
temperatures. Two-dimensional (2D) topological insulators (TIs) have recently
attracted significant attention due to their dissipationless transport, robust
properties and excellent compatibility with device integration. However, a
major barrier of 2D TIs is their small bulk band gap, which allows for
applications only in extremely low temperatures. In this work, first principle
calculations were used to analyze the geometric, electronic, and topological
properties of PbC2X and BiC2X (X = H, Cl, F, Br, I) compounds. The band gap
values are remarkably large, ranging from 0.79eV to 0.99eV. The nanoribbons of
these compounds exhibited nontrivial topological order in the simulation, thus
proving ethynyl-derivative functionalized Pb and Bi films to be new classes of
giant band gap 2D TIs. In addition, these findings indicate that chemical
functionalization with ethynyl-derivatives is an effective method to tune the
band gap and preserve the nontrivial topological order. These novel materials
that are applicable at both room temperature and high temperatures open the
door to a new generation of electronics.
