Although chirality is recognized as the universal asymmetry, which plays a fundamental role in chemistry, biology, physics, and life on earth, its rigorous quantification remains illusive. Since Lord Kelvin's definition of structural chirality as broken mirror symmetry, there has been significant deliberation on the notion. It is understood that achiral objects may generate chiral response; handedness may dependent on orientation; left- to right-handed response may be continuously connected without going through an achiral state; and handedness has continuous measure that can be quantified. These manifestations are realized in the chiroptical response of the prototypical nano-antenna consisting of a plasmonic nanosphere dimer: Nominally achiral dimers show giant Raman optical activity and orientation dependent handedness (ODH) that can be continuously interconverted while maintaining chirality. The phenomenon can be rigorously understood to arise from the symmetries of the vectorial light-matter interaction, and nonlocality to first order in spatial dispersion is sufficient to reproduce all observations. The measurements demonstrate that the nanosphere dimer sustains chiral plasmons with well-defined angular momentum states, the familiar Σ, π, Δ states of diatomics, which arise naturally in the irreducible spherical representation of dipole-dipole tensor. More generally, the nanodumbbell can be recognized as a flexible building block of metamaterials, capable to sustain designer optical properties, such as negative index, anisotropic and nonreciprocal and Tellegen response. And the same principles can be extended through conformal transformations to nanorods, nanocrescents and their arrays.<br/>

How to turn a right hand into left: Chiral plasmons and more

253rd National Meeting (2017)

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