Topological exciton condensation and superstructures in semimetallic monolayer transition metal dichalcogenides

Two-dimensional materials, such as monolayer transition metal dichalcogenides, provide excellent platform to study the interplay of topology, spin-orbit coupling and interaction effect. Recently it is proposed that 1T' WTe$_2$ and MoTe$_2$ may be topological semimetals under a Peierls-like distortion. In this work, we study the semimetal-insulator transition in such type of materials driven by excitonic instability. We find a regime of topological exciton condensation in the presence of spin-orbit coupling and strong anisotropy. New superstructure is generated, which allows possible experimental detection. This work is supported by DOE Basic Energy Sciences Grant No. DE- SC0012509