  Two-dimensional (2D) topological insulators (TIs), a new state of quantum
matter, are promising for achieving the low-power-consuming electronic devices
owning to the remarkable robustness of their conducting edge states against
backscattering. Currently, the major challenge to further studies and possible
applications is the lack of suitable materials, which should be with high
feasibility of fabrication and sizeable nontrivial gaps. Here, we demonstrate
through first-principles calculations that SiTe 2D crystal is a promising 2D TI
with a sizeable nontrivial gap of 0.220 eV. This material is dynamically and
thermally stable. Most importantly, it could be easily exfoliated from its
three-dimensional superlattice due to the weakly bonded layered structure.
Moreover, strain engineering can effectively control its nontrivial gap and
even induce a topological phase transition. Our results provide a realistic
candidate for experimental explorations and potential applications of 2D TIs.
