Magnetic plasmon resonances in nanostructured topological insulators for strongly enhanced light–MoS2 interactions

Abstract

Magnetic resonances not only play crucial roles in artificial magnetic materials but also offer a promising way for light control and interaction with matter. Recently, magnetic resonance effects have attracted special attention in plasmonic systems for overcoming magnetic response saturation at high frequencies and realizing high-performance optical functionalities. As novel states of matter, topological insulators (TIs) present topologically protected conducting surfaces and insulating bulks in a broad optical range, providing new building blocks for plasmonics. However, until now, high-frequency (e.g. visible range) magnetic resonances and related applications have not been demonstrated in TI systems. Herein, we report for the first time, to our knowledge, a kind of visible range magnetic plasmon resonances (MPRs) in TI structures composed of nanofabricated Sb₂Te₃ nanogrooves. The experimental results show that the MPR response can be tailored by adjusting the nanogroove height, width, and pitch, which agrees well with the simulations and theoretical calculations. Moreover, we innovatively integrated monolayer MoS₂ onto a TI nanostructure and observed strongly reinforced light–MoS₂ interactions induced by a significant MPR-induced electric field enhancement, remarkable compared with TI-based electric plasmon resonances (EPRs). The MoS₂ photoluminescence can be flexibly tuned by controlling the incident light polarization. These results enrich TI optical physics and applications in highly efficient optical functionalities as well as artificial magnetic materials at high frequencies.

Topological insulators: visible range magnetic resonances

Nanostructured antimony telluride (Sb₂Te₃) can support visible range magnetic resonances and dramatically enhance the weak interactions of light with 2D materials. Hua Lu and workers from China and Australia used focused ion beam milling to write a grating of periodic nanogrooves into single-crystalline Sb₂Te₃, a well-known topological insulator. They then placed a flake of the 2D material MoS₂ on top. Characterization showed the existence of a kind of magnetic plasmon resonances (MPRs) with a resonant wavelength that redshifts with increasing nanogroove height and pitch and blueshifts with increasing nanogroove width. Visible photoluminescence experiments showed that the MPRs can dramatically increase the emission from the MoS₂, which could be tuned by changing the polarization angle of the incident excitation light. The findings are expected to aid the development of nanoscale optical devices made from layered nanomaterials.