Van Hove singularities in large angle twisted bilayer transition metal dichalcogenides

Twisted bilayer transition metal dichalcogenides are known to host flat electronic bands for small twist angles (close to 0° or 60°). These flat bands generally owe their origin to structural reconstructions in the large-area moiré patterns. Here, using first principles calculations we study the emergence of unique Van Hove singularities in large twist-angle bilayers where structural reconstruction is absent. These singularities originate from band flattening in a region of the moiré Brillouin zone and potentially occur only at certain twist-angles. We study the evolution of the electronic band structure with twist-angle in various transition metal dichalcogenide bilayer systems to arrive at a predictive model for these Van Hove singularities.