Moire Chiral Metamaterials

Plasmonic chiral metamaterials are promising for applications in chiral sensors and photonic devices due to their strong optical chirality and light-matter interactions at the subwavelength scale. However, most of current plasmonic chiral metamaterials rely on local structural chirality or site-specific symmetry breaking, which has limited their optical activity, tunability, and scalable fabrication for practical applications. Here, this paper reports a new type of chiral metamaterials consisted of two layers of identical achiral Au nanohole arrays stacked into moire patterns. The chiroptical responses of the moire chiral metamaterials can be precisely tuned by the in-plane rotation between the two layers of nanohole arrays. Furthermore, the moire chiral metamaterials are applied to achieve label-free enantiodiscrimination of biomolecules and drug molecules at the picogram level. With their ultrathin thickness (approximate to 70 nm, which is only approximate to 1/10 of the operation wavelength), strong chirality, and high tunability, the moire chiral metamaterials will advance a variety of photonic and optoelectronic applications.