Interlayer exciton valleytronics in bilayer heterostructures interfaced with a phase gradient metasurface

Interlayer excitons in bilayer heterostructures of two-dimensional semiconductors have opened a new platform for valley physics and optoelectronic applications owing to several unique properties. Here, we theoretically demonstrate the coherent manipulation of the interlayer excitonic valley degree of freedom in a transition metal dichalcogenide heterobilayer interfaced with a phase gradient metasurface. We harness the peculiar out-of-plane component of polarization of interlayer excitons in conjunction with the anisotropy of the vacuum of the electromagnetic field enabled by the metasurface to induce coherent coupling between mutually orthogonal interlayer excitonic optical selection rule. This coupling leads to a much larger domain within the valley psuedo-spin Bloch sphere being accessible in these heterostructures. Our proposed route to coherent manipulation of interlayer excitons in bilayer heterostructures with structured interfaces such as a metasurface may pave the way for engineering an array of interacting quantum emitters in Moiré heterostructures for chip-scale quantum information science.