Optical spectroscopy of interlayer coupling in artificially stacked MoS ₂ layers

We perform an optical spectroscopy study to investigate the properties of different artificial MoS 2 bi- and trilayer stacks created from individual monolayers by a deterministic transfer process. These twisted bi- and trilayers differ from the common 2H stacking in mineral MoS 2 in the relative stacking angle of adjacent layers and the interlayer distance. The combination of Raman spectroscopy, second-harmonic-generation microscopy and photoluminescence measurements allows us to determine the degree of interlayer coupling in our samples. We find that even for electronically decoupled artificial structures, which show the same valley polarization degree as the constituent MoS 2 monolayers at low temperatures, there is a resonant energy transfer between individual layers which acts as an effective luminescence quenching mechanism.