  Based on density functional theory and Berry curvature calculations, we
predict that p-p band inversion type quantum spin Hall effect (QSHE) can be
realized in a series of two dimensional (2D) bilayer honeycomb TlM (M = N, P,
As, Sb), which can be effectively equivalent to bilayer triangular lattice for
low energy electrons. Further topological analysis reveals that the band
inversion between pz- and px,y of M atom contributes to the nontrivial
topological nature of TlM. The band inversion is independent of spin-orbit
coupling which is distinctive from conventional topological insulators (TIs). A
tight binding model based on triangle lattice is constructed to describe the
QSH states in the systems. Besides the interesting 2D triangular lattice $p-p$
type inversion for the topological mechanism, the maximal local band gap of the
systems can reach 550 meV (TlSb), which provides a new choice for future room
temperature quantum spin Hall Insulator (QSHI). Considering the advance of the
technology of van der Waals passivation, combining with hexagonal materials,
such as h-BN, TlMs show great potential for future 2D topological electronic
devices.
