Optical vibrations on microscopic rings in a magnetic field

We show that on microscopic rings, such as cyclic polymer molecules, or on quantum dots the frequency of some vibrations depends on the magnetic field and on the electron filling factor. The effect is related to the existence of orbital currents on the ring, which induce a frequency change of the vibrational mode. Each increase in single-electron current induces a change in the vibrational frequency. The magnetic field may also create an equilibrium distortion of atoms. The extent of atomic distortions changes with the magnetic field. The latter effect is characterized by a huge electric polarizability and hyperpolarizability of cyclic molecules, discovered recently. The relation of persistent current on rings and on quantum dots to the frequency-change effect is discussed; possible experiments are proposed.