Temperature dependence of photoluminescence in twisted heterobilayers of transition-metal dichalcogenides

Abstract

Two-dimensional (2D) van der Waals transition metal dichalcogenides (TMDCs) are highly attractive due to their novel phenomena and potential device applications. Especially, twisted heterojunction of different 2D TMDC monolayers for various twist angles (θ) is one of the hot issues in the area of 2D TMDCs because they exhibit exotic quantum behaviors. Here, we report the effect of temperature (T) on the θ-dependent variation of photoluminescence (PL) spectra of MoS2/WS2 heterobilayers. The PL peak-vs-T variations are divided into three θ regions. Near θ = 0 and 60°, the PL peak energies show almost monotonically-decreasing behaviors with increasing T, caused by stronger electron-phonon interactions at higher T. However, in the intermediate θ range, the PL peaks show similar red shifts over almost full T range except anomalous blue shifts in a short T range near ∼150 K. We discuss this anomalous PL behaviors based on hybridization of interlayer and intralayer excitons, resulting in the formation of hybridized excitons, correlated with structural transition.