  By using first-principles calculation, we have found that a family of 2D
transition metal dichalcogenide haeckelites with square-octagonal lattice
$MX_2$-4-8 ($M$=Mo, W and $X$=S, Se and Te) can host quantum spin hall effect.
The phonon spectra indicate that they are dynamically stable and the largest
band gap is predicted to be around 54 meV, higher than room temperature. These
will pave the way to potential applications of topological insulators. We have
also established a simple tight-binding model on a square-like lattice to
achieve topological nontrivial quantum states, which extends the study from
honeycomb lattice to square-like lattice and broads the potential topological
material system greatly.
