Tunable optical resonators and metamaterials through Casimir self-assembly

Self-assembly plays a vital role in a great variety of phenomena in nature, ranging from atomic and molecular systems to living matter, climate, and even gravitational galaxy formation.

In this project, we will study how quantum electrodynamics Casimir forces can lead to self-assembly at unusually long separation distances and at normal experimental conditions – an aqueous solution of gold nanoflakes at room temperature.

In this process, remarkably stable gold nanoflake pairs can be formed in which a top flake “levitates” above the bottom one.

Because of the unusually long-range interactions, such an arrangement also supports pronounced optical Fabry-Pérot resonances in the technologically relevant visible spectral range.

As opposed to the standard short-range van der Waals forces, the long-range Casimir interactions require accurate inclusion of retardation effects, which eventually lead to the appearance of stable equilibria in our system at long separation distances (100 nm) – long enough for affecting resonant modes of the visible light.A deeper understanding of Casimir forces, which is at the core of this project, promises new directions in contact-free nanomachinery, polaritonic chemistry, and light-matter interactions in general.

Moreover, Casimir self-assembly can be scaled up to macroscopic dimensions and form an entirely new class of “soft” metamaterials, tunable by external stimuli, such as light pressure, electrical bias, or solution composition.