, , Theodore Jacobson, ,
We study the dynamics of a supersonically expanding Bose-Einstein ring condensate both experimentally and theoretically using simulations. Such expansion shows a redshift of long-wavelength excitations, similar to those seen in the standard cosmological picture of an expanding universe. After the expansion ceases, we then observe the creation of large numbers of azimuthal phonon excitations in the ring and topological excitations in the form of persistent currents. The process through which these excitations are produced involves short length scales where the Bogolyubov spectrum becomes non-linear (i.e., Lorentz symmetry fails). Bulk topological excitations -- solitons and vortices -- drive the production the azimuthal phonons and, at late times, cause stochastic persistent currents.
Physical Review X
Bose-Einstein condensation, cosmology, phonons, superfluidity, ultracold atoms, solitons, vortices