Intrinsic circularly polarized exciton emission in a twisted van der Waals heterostructure

We report the emergence of a significant degree of intrinsic circular polarization of exciton photoluminescence in a twisted MoSe₂/WSe₂ heterostructure upon nonresonant driving with a linearly polarized laser. The effect is not related to the polarization of the incident light. Moreover, it is present at zero magnetic field, and reacts perceptibly to a perpendicularly applied magnetic field that, unexpectedly, can strongly diminish this effect. The giant magnitude of the polarization, which cannot be explained by natural optical activity or circular dichroism of the twisted lattice, suggests a kinematic origin arising from an emergent pyromagnetic symmetry in our structure, which we exploit to gain insight into the microscopic optical processes of our device.