Trapped photons: Transverse plasmons in layered semiconducting heterostructures

We elucidate the properties of a robust transverse polarization mode in heterostructures of transition metal dichalcogenides. This trapped-photon mode arises from strong interband light-matter coupling, but its nature is fundamentally distinct from extensively studied exciton polaritons, as well as photon-cavity modes. It can be viewed as a transverse counterpart to the longitudinal two-dimensional Dirac plasmon mode found in doped graphene, characterized by much greater oscillatory strength. Furthermore, the trapped photon is easily tunable by adjusting the number of semiconducting layers, allowing for enhanced photon-electron-hole binding strength. In addition, we devise a near-field microscopy simulation that paves the way for future experimental characterization, which could lead to exciting applications in optoelectronics, sensing, and quantum information processing.