Suppression of Ion Transport due to Long-Lived Subwavelength Localization by an Optical Lattice

We report the localization of an ion by a one-dimensional optical lattice in the presence of an applied external force. The ion is confined radially by a radio frequency trap and axially by a combined electrostatic and optical-lattice potential. Using a resolved Raman sideband technique, one or several ions are cooled to a mean vibrational number $⟨n⟩=(0.1\pm 0.1)$ along the optical lattice. We measure the average position of a periodically driven ion with a resolution down to $\lambda /40$, and demonstrate localization to a single lattice site for up to 10 ms. This opens new possibilities for studying many-body systems with long-range interactions in periodic potentials, as well as fundamental models of friction.