Two-dimensional (2D) transition metal dichalcogenides (TMDs) have great potential for valleytronics due to their ability to host excitons with valley degrees of freedom [1]. They possess distinct valleys that can be controlled with circularly polarized light, and coherent valley superpositions can be generated with linearly polarized light. However, the coherence of valleys faces challenges due to rapid decoherence [2]. To improve coherence time, zero-dimensional confinement in moiré superlattices, like twisted bilayer TMDs, can be employed. Polarization-resolved photoluminescence spectroscopy shows linearly polarized PL with linearly polarized excitation. However, we have observed that the polarization direction does not depend on the excitation laser. This suggests the presence of strain that disrupts the three-fold rotational symmetry of the moire potential. To comprehend the strain effect, we conducted polarization-resolved mapping at 3 K. As shown in Figure 1, the polarization direction strongly varies with positions. We also found that positions exhibiting polarization close to the incident polarization can respond to changes in excitation polarization directions. These findings provide insight into the relationship between strain and manipulating the valley degree of freedom.
