There is a well-established link between the spin angular momentum of light, which is manifest in circular or elliptical polarizations, and chiral interactions with matter. However, any inference of such a simple connection between chirality and angular momentum in general is unwarranted. The pursuit of any parallels in chiroptical effects with vortex structured light, which convey orbital angular momentum, has until recently proved problematic, whilst the consideration of multipole aspects for the individual photon has elicited a variety of views. This Keynote review details the resolution of such issues based on a fundamental symmetry analysis of a generalized interaction between matter and structured light, revealing mechanisms that can support the long-sought connection indicated by the latest experiments.
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