  Conventional spin-degenerated surface electrons have been effectively
manipulated by using organic and inorganic self-assembled nanoarrays as
resonators. Step superlattices naturally assembled in vicinal surfaces are a
particularly interesting case since they represent simple one-dimensional (1D)
models for fundamental studies, and can imprint strong anisotropies in surface
electron transport in real devices. Here we present the first realization of
periodic resonator arrays on the BiAg2 atom-thick surface alloy with
unprecedented atomic precision, and demonstrate their potential ability for
tuning helical Rashba states. By employing curved crystals to select local
vicinal planes we achieve tunable arrays of monoatomic steps with different
morphology and orientation. Scanning the ultraviolet light beam on the curved
surface during angle-resolved photoemission experiments allows one to unveil
the scattering behavior of spin-textured helical states. In this way, we find
coherent scattering of helical Rashba states from the step arrays, as well as
step-density-dependent Rashba band shifts and spin-orbit splitting compared to
the extended BiAg2 plane.
