Electric dipole moment oscillations in Aharonov-Bohm quantum rings
  Magneto-oscillations of the electric dipole moment are predicted and analyzed for a single-electron nanoscale ring pierced by a magnetic flux (an Aharonov-Bohm ring) and subjected to an electric field in the ring's plane. These oscillations are accompanied by periodic changes in the selection rules for inter-level optical transitions in the ring allowing control of polarization properties of the associated terahertz radiation. 
A. M. Alexeev, M. E. Portnoi
cond-mat.mes-hall