Time-of-flight roton spectroscopy in dipolar Bose-Einstein condensates

Dipolar Bose-Einstein condensates may present a rotonlike dispersion minimum, which has yet to be observed in experiments. We discuss a simple method to reveal roton excitations based on the response of quasi-two-dimensional dipolar condensates against a weak lattice potential. By employing numerical simulations for realistic scenarios, we analyze the response of the system as a function of both the lattice spacing and the s-wave scattering length, showing that the rotonminimum may be readily revealed in current experiments by the resonant population of Bragg peaks in time-of-flight measurements.