Phase transition and electronic structure evolution of MoTe2 induced by W substitution

The transition-metal dichalcogenide compounds MoTe2 and WTe2 are polymorphic with both semiconducting and metallic phases. The thermodynamically stable phase of WTe2 at room temperature is orthorhombic and metallic and displays a wide range of interesting phenomena including type-II Weyl fermions, titanic magnetoresistance and superconductivity in bulk, and quantum spin Hall insulator behavior in the monolayer case. On the other hand, the stable phase of MoTe2 at room temperature is a trigonal prismatic semiconductor that has a direct gap in the monolayer with strong spin-orbit coupling. The alloy series Mo1-x W-x Te-2 thus offers the possibility for tuning the structural and, consequently, electronic phases via tuning of the composition. Here, we report comprehensive studies of the electronic structure of Mo1-x W-x Te-2 alloys using angle-resolved photoemission spectroscopy and first-principles calculations as a function of composition. At room temperature, we find a sharp boundary between the orthorhombic and the trigonal prismatic phases at x = 0.10 using structural characterization. We also show that by compositional tuning it is possible to control the band inversion in this series of compounds thus yielding important consequences for topological surface states.