Linear response in Fermionic Superfluids

When a fermionic superfluid is perturbed by a time dependent potential with small enough amplitude, then we expect the response to be linear with respect to the strength of the potential. However, in recent experiments by Nir et. al. and simulations by our group, we have noticed a stark non-linearity. Moreover, the peak of the response function over the spectrum shifts with the amplitude. This is where we explore and propose a reason behind such behaviour. The work would shed light on dynamics of driven condensates in greater depth and can even allow us to leverage the amplifying effects of resonance.