Noble metal / 2D semiconducting material multilayer structure: a platform to achieve the strong coupling regime

The light-matter interaction is important for various practical photonic applications. Multi-level photon sources, quantum emitters (QEs), are used to emit and store light and are important for quantum applications. By smart placement of the QEs close to a nanostructure, their relaxation rate can be accelerated, leading to high Purcell factors. Usually the light-matter interaction is described in the weak coupling regime; at high Purcell factor values, the QE/environment interaction needs to be described in the strong coupling regime. We show that the noble metal /2D semiconducting material (WS₂) multilayer structure can be used in order to achieve the strong coupling regime [1]. The noble metal layer supports surface plasmon modes and the WS₂ layer hosts excitons with high oscillation strengths. A QE placed in their proximity features an energy splitting in its emission spectrum, a sign of the strong coupling regime. Different noble metal materials (Au, Ag, Cu and Al) are considered; when an Au layer is sandwiched between two WS₂ layers, a Rabi-splitting of 257 meV occurs when the transition energy of the QE is 2.02 eV. This effect shows that the light-matter interaction approaches the ultra-strong coupling regime.

[1] V. Karanikolas et. al, Phys. Rev. Research 2, 033141 (2020).