  We demonstrate how to create all-dielectric metasurfaces with a strong
toroidal response by arranging two types of nanodisks into asymmetric quadrumer
clusters. We demonstrate that a strong axial toroidal response of the
metasurface is related to conditions of the trapped (dark) mode that is excited
due the symmetry breaking in the cluster. We study the correlation between the
toroidal response and asymmetry in the metasurface and nanocluster geometries,
which appears from the different diameters of nanodisks or notches introduced
into the nanodisks.
