Valley Selective Optical Routing in Hyperbolic Metamaterials*

At the monolayer limit, the 2D transition metal dichalcogenides materials such as WS₂, WSe₂, and MoS₂ etc., are endowed with direct bandgap and high binding energy excitons at individually addressable two degenerate valleys in momentum space at K and K' points in the first Brillouin zone. In recent years, there has been growing interest in achieving control over the selective valley excitation/emission by means of optical, electrical, and magnetic fields and explore this valley degree of freedom as an efficient way of data transfer, computing and storage technology, called valleytronics. We describe and experimentally demonstrate the optical control on selective valley excitation and emission routing through spatially confined subwavelength electromagnetic modes in an anisotropic metamaterial with hyperbolic dispersion. The directionality of selective valley exciton emission depends on the handedness of that valley’s circular polarization emission. The demonstrated capability of our hyperbolic metamaterial -TMD hybrid system is free from precise nanoscale structural dimensions and most importantly broadband response and shows great potential to develop prototype devices such as valley filters or valley-based qubits for quantum computing/communications.