Towards negative index self-assembled metamaterials

We investigate the magnetic response of meta-atoms that can be fabricated by a bottom-up technique. Usually such meta-atoms consist of a dielectric core surrounded by a large number of solid metallic nanoparticles. In contrast to those meta-atoms considered thus far, here we study hollow metallic nanoparticles (shells). In doing so, we solve one of the most pertinent problems of current self-assembled metamaterials, namely, implementing meta-atoms with sufficiently large resonance strength and small absorption. Both conditions have to be met for deep subwavelength meta-atoms to obtain effectively homogeneous metamaterials which may be meaningfully described by negative material parameters. Eventually we show that by using these findings, self-assembled negative index materials come within reach.