“Cosmological” quasiparticle production in harmonically trapped superfluid gases

We show that a variety of cosmologically motivated effective quasiparticle space-times can be produced in harmonically trapped superfluid Bose and Fermi gases. We study the analog of cosmological particle production in these effective space-times, induced by trapping potentials and coupling constants possessing an arbitrary time dependence. The WKB probabilities for phonon creation from the superfluid vacuum are calculated, and an experimental procedure to detect quasiparticle production by measuring density-density correlation functions is proposed.

Figure 1

Exponential expansion of a two-component Bose-Einstein condensate with effective spin $F=1∕2$, to create a de Sitter quasiparticle universe close to its center. The trapping potential is inverted by applying a radio frequency $\left(\text{rf}\right)$ pulse, which transfers the atoms to their untrapped hyperfine state.