Self-assembled plasmonic metamaterials with unnaturally high optical refraction

High refractive index provides various benefits such as miniaturization of optical elements, enhancement of resolution for imaging techniques and utilization for transformative optics. In line with this, a lot of efforts have been taken to engineer and increase the refractive index (n). Especially, metamaterials have enabled to extremely increase the refractive index beyond the naturally occurring materials [1,2]. However, the high-index metamaterials, developed thus far, has been mainly limited to the regime of the relatively low frequency due to their easy-to-craft features (e.g., n of 38.64 at THz and ~1800 at microwave) [3,4]; an increase in n beyond the natural limit is yet to be achieved at optical regimes. The monolithic lithography, which has been a major tool for the development of the metamaterials, would be difficult to satisfy the requirements for achieving unnaturally high n at optical range, including the arraying of sub-100 nm building blocks with a few nm-gaps over the