  Laser irradiation of various materials including metals, polymers and
semiconductors with vortex beams was previously shown to twist transiently
molten matter providing the direct easy-to-implement way to obtain chiral
surface relief. Specifically for metals, this effect was attributed to transfer
of an optical angular momentum (OAM) carrying by the vortex beam. In this
Letter, we report the formation of twisted metal nanoneedles on the surface of
silver and gold metal films under their irradiation with zero-OAM laser beam
having spiral-shape lateral intensity distribution. Our comparative experiments
clearly demonstrate, for the first time, that the formation process of chiral
nanoneedles on the surface of plasmonic-active metals is mainly governed by the
temperature-gradient induced chiral thermocapillary mass transfer rather that
the OAM driven rotation of the transiently molten matter.
