Time-of-Flight Roton Spectroscopy in Dipolar Bose-Einstein Condensates

摘要

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