Blueshift of the A-exciton peak in folded monolayer 1H-MoS sub(2)

The large family of layered transition-metal dichalcogenides is widely believed to constitute a second family of two-dimensional (2D) semiconducting materials that can be used to create novel devices that complement those based on graphene. In many cases these materials have shown a transition from an indirect band gap in the bulk to a direct band gap in monolayer systems. In this work we experimentally show that folding a 1H molybdenum disulfide (MoS sub(2)) layer results in a turbostratic stack with enhanced photoluminescence quantum yield and a significant shift to the blue by ~90 meV. This is in contrast to the expected 2H-MoS sub(2) band-structure characteristics, which include an indirect gap and quenched photoluminescence. We present a theoretical explanation for the origin of this behavior in terms of exciton screening.