Ballistic spin locking in a two-dimensional Rashba system

Abstract

Coherent spin rotation is a prerequisite for processing spin information in spintronics and for acquiring quantum information. The spin state is typically controlled by applying an external magnetic field to induce spin precessional motion around the field axis. While electrical spin control is possible using the effective magnetic field induced by the spin-orbit (SO) interaction, the functionality of spin manipulation is still based on rotation around this field. Here we report a new concept of spin manipulation by controlling electron orbital motion at the nanoscale: electron spin rotates in a circular orbital motion while spin orientation is locked towards the SO field rather than the spin precession. This effect, which we have termed “ballistic spin locking”, illustrates the interconnectivity of the electron spin and orbital motion in a ballistic regime and allows us to extend control of the spin states beyond the limits imposed by rotation around the magnetic field.