Modification of superfluidity in a resonantly strongly driven Bose-Einstein condensate

We investigate the spectrum of elementary excitations for T=0 of a resonantly strongly driven two-component Bose-Einstein condensate (BEC) taking account of the Rabi oscillations. It is shown that the spectrum has two phononlike branches. Due to the inequality of the scattering lengths the Bogoliubov speed of sound of both branches differs from the Bogoliubov speed of sound for nondriven BEC, which leads to a modification of superfluidity. We have shown that the proposal to apply an additional resonant magnetic field in a scheme of the Feshbach resonance makes it possible to attain a very high sweep rate of the Feshbach resonance.