Fano resonance and photoluminescence enhancement in WS₂-integrated topological insulator metasurfaces

Plasmon-exciton coupling effect plays a crucial role in light emission and quantum control, which, however, has not been reported in nonmetallic systems until now. Topological insulators (TIs), with breaking through the limitations of traditional metallic materials on the operating frequency range and photonic integration, offer a new platform for exploring surface plasmons and their interaction with matter. Herein, we experimentally demonstrate the scattering resonance response of surface plasmons in the antimony telluride (Sb₂Te₃) TI metasurfaces with focused ion beam (FIB)-fabricated nanowells as well as the coupling behaviors between the plasmons and excitons in atomic-layer tungsten disulfide (WS₂) semiconductors. The measured results show that the wavelength of scattering resonance presents a redshift with increasing the depth and pitch of TI nanowells. In WS₂/TI metasurface heterostructures, we observe the obvious coupling effect between the TI plasmons and excitons in WS₂ atomic layers. The theoretical analysis reveals that the plasmon-exciton interaction is located in the weak coupling regime with the generation of Fano resonance, inducing strong photoluminescence (PL) enhancement of WS₂ atomic layers. This work will open a new door for plasmon-exciton coupling and applications of TIs in compact optoelectronic devices.