Phonon and exciton temperature-dependent properties of twisted MoS_2

In the present work, Raman and photoluminescence spectroscopies were used to study the dynamics of phonons and different excitons of MoS_2 bilayer under a rotation of 29^∘ dependent of the temperature. The twisted bilayer (T-2L) of MoS_2 was obtained through mechanical exfoliation, and subsequently rotated using a dimethyl polysiloxane (PDMS) substrate and deterministic transferred to a SiO_2 substrate. The Raman spectrum of the twisted bilayer presents three peaks E' (386 cm^-1), A'_1 (405 cm^-1) and an FA' peak at approximately 409 cm^-1 linked to the A'_1 mode, which is attributed to a Moiré pattern phonon. Both modes (A'_1 and FA') are dependent of light polarization in a way that demonstrates an effective coupling between the layers. It was also verified through the Grüneisen parameter, an increase in the anharmonicity of the mode in the E' plane and a decrease the same for A'_1. In the PL measurements, the appearance of an exciton in T-2L was verified, which generated a second shoulder measured at ≈1.58 eV attributed to an indirect transition of an I trion. The interaction between the rotated monolayers of MoS_2 proved to be an important parameter for possible fine-tuning of the properties of bilayer samples.