We study the effects of infrared radiation on a two-dimensionai Bardeen-Cooper-Schrieffer superconductor coupled with a normal metal substrate through a tunneling barrier.The phase transition is analyzed by inspecting the stability of the system against perturbations of pairing potentials.We find an oscillating gap phase with a frequency not directly related to the radiation frequency,but instead resulting from the asymmetry of electron density of states of the system as well as the tunneling amplitude.When such a superconductor is in contact with another superconductor,gives rise to an unusual alternating Josephson current.
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