The optical response of artificially twisted MoS 2 bilayers

Abstract

Two-dimensional layered materials offer the possibility to create artificial vertically stacked structures possessing an additional degree of freedom—theinterlayertwist. We present a comprehensive optical study of artificially stacked bilayers (BLs) MoS2 encapsulated in hexagonal BN with interlayer twist angle ranging from 0∘ to 60∘ using Raman scattering and photoluminescence spectroscopies. It is found that the strength of the interlayer coupling in the studied BLs can be estimated using the energy dependence of indirect emission versus the A1g–E2g1 energy separation. Due to the hybridization of electronic states in the valence band, the emission line related to the interlayer exciton is apparent in both the natural (2H) and artificial (62∘) MoS2 BLs, while it is absent in the structures with other twist angles. The interlayer coupling energy is estimated to be of about 50 meV. The effect of temperature on energies and intensities of the direct and indirect emission lines in MoS2 BLs is also quantified.