Dynamic response of an ultracold Fermi gas near the Feshbach resonance

Abstract

We investigate the dynamical response of strongly interacting ultra-cold fermionic atoms near Feshbach resonance to varying magnetic fields. Following the experimental practices, we calculate the response of the atoms to oscillating and to linearly ramped magnetic fields respectively. For oscillating magnetic fields, depending on the frequencies and the amplitudes of the oscillations, the response of the pair excitation gap shows either linear or rich non-linear behaviour. In addition, both the spectral studies through the linear response theory and the time-domain simulations suggest the existence of a resonant frequency corresponding to the pair dissociation threshold. For linearly ramped magnetic fields, the response of the excitation gap shows damped oscillations. The final value of the excitation gap depends on the rate of the field sweep.