  Nonradiating current configurations attract attention of physicists for many
years as possible models of stable atoms in the field theories. One intriguing
example of such a nonradiating source is known as anapole (which means without
poles in Greek), and it was originally proposed by Yakov Zeldovich in nuclear
physics. Recently, an anapole was suggested as a model of elementary particles
describing dark matter in the Universe. Classically, an anapole mode can be
viewed as a composition of electric and toroidal dipole moments, resulting in
destructive interference of the radiation fields due to similarity of their
far-field scattering patterns. Here we demonstrate experimentally that
dielectric nanoparticles can exhibit a radiationless anapole mode in visible.
We achieve the spectral overlap of the toroidal and electric dipole modes
through a geometry tuning, and observe a highly pronounced dip in the far-field
scattering accompanied by the specific near-field distribution associated with
the anapole mode. The anapole physics provides a unique playground for the
study of electromagnetic properties of nontrivial excitations of complex
fields, reciprocity violation, and Aharonov-Bohm like phenomena at optical
frequencies.
