Temperature activation of indirect exciton in nanostructures based on MoS2

Micro-photoluminescence studies of MoS2 nanotubes have shown that both direct and indirect excitonic transitions contribute to the emission spectra despite the fact that dozens of monolayers are inside their walls and, therefore, only indirect exciton emission would be expected. In addition, the intensity of the indirect exciton band increases with temperature in contrast to the direct exciton band, the intensity of which decreases. The same effects are observed for MoS2 flakes. To describe these phenomena, we propose a theoretical model that considers the balance between exciton transitions taking into account the spin-forbidden exciton states.