Band gap opening induced by vanishing interlayer interaction in intercalated 1T′-MoTe2

A substantial energy gap is essential for quantum spin Hall (QSH) insulators in devices and fundamental research. Monolayer 1T′-MoTe2 is recognized as a promising candidate, featuring a potentially large energy gap. However, despite extensive efforts including molecular beam epitaxy growth, mechanical exfoliation, and chemical vapor deposition techniques, achieving stable 1T′-MoTe2 with a well-defined energy gap has proven elusive. Here, we successfully open a band gap of approximately 70 meV in bulk 1T′-MoTe2 by reducing the interlayer interaction through the intercalation of organic cations HMIM+. Both resistivity measurements and infrared spectroscopy confirm distinct semiconducting behaviors. Band structure calculations show that the gap emerges from the absence of interlayer coupling, and that the intercalated 1T′-MoTe2 is topologically nontrivial with Z2=1. This work not only demonstrates a bulk 1T′-MoTe2 possible QSH insulator with a sizable gap, but also provides a different approach to realizing clean, stable platforms for exploring the QSH effect and designing low-power quantum electronic and spintronic devices.