Polarisation switching and electrical control of interlayer excitons in two-dimensional van der Waals heterostructures

Interlayer excitons in van der Waals heterostructures of transition metal dichalcogenides are of great interest due to their fascinating spin-valley and moiré physics. These aspects could be implemented to realize next-generation photonic and valleytronic devices, as well as exploring new physical phenomena. However, the efficient manipulation of the exciton valley-state, a necessary requirement for valley information encoding, is still lacking. In this talk, we will demonstrate electrical control of interlayer excitons in a MoSe₂/WSe₂ heterostructure. Encapsulation of aligned monolayers with boron nitride allows to resolve two separate interlayer transitions with opposite helicities under circularly polarized excitation, either preserving or reversing the polarization of incoming light. By electrically modulating these resonances, we realize a polarization switch with tuneable emission intensity and wavelength in the near-infrared. By applying magnetic fields, we assign the origin of the effect to the moiré-induced brightening of forbidden optical transitions, as also predicted by recent theoretical works. The ability to control the polarization of interlayer excitons is a step forward towards the practical manipulation of the valley degree-of-freedom in device applications.