Phase-Locked Rotation of Crystallized Non-neutral Plasmas by Rotating Electric Fields

We report the precise control of the rotation frequency of strongly coupled non-neutral plasmas by rotating electric fields. These plasmas of up to 10⁶ ⁹Be⁺ ions are trapped in a Penning trap and laser cooled into crystallized structures which undergo a rigid-body rotation. Bragg diffraction shows that the crystalline lattice can be stable for longer than $30$ min ( ~10⁸ rotations), and that the plasma rotation can be phase locked to the applied field without any slip. These corotating plasmas are in a novel global thermal equilibrium whose asymmetric surface shape (triaxial ellipsoid) has been measured.