Single-photon and two-photon decay channels of superfluid current in thin rings irradiated by a low-frequency coherent electromagnetic field

The decay of a superconducting current in thin rings irradiated by a low-frequency coherent electromagnetic field has been predicted. Coherent oscillations induced in the superconducting condensate by this field lead to the emission of photons with the energy predominantly determined by discrete values of the energy of the superconducting ring. The thickness of the ring should be smaller than the skin depth of this field and than the London penetration depth. The discrete decay of the superconducting current accompanied by emission of one and two photons has been investigated for the first time. Numerical results have been presented for the angular and energy distributions of photons, as well as for the lifetime of the supercurrent states as a function of the size of the superconducting ring and the number of fluxoids in the initial state.