Collective Excitations of a Dipolar Bose-Einstein Condensate in an Anharmonic Trap

The collective excitations of a one-dimensional dipolar BoseEinstein condensate trapped in an anharmonic potential are investigated theoretically.Using the variational approach,we obtain the coupled equations of motion for the center-of-mass coordinate of the condensate and its width.In particular,analytical expressions for the low-lying excitation modes are given.The results show that dipole-dipole interactions reduce the frequency shift induced by quartic distortion.The interplay between dipole-dipole interactions and anharmonic distortion for the collapse and revival of the collective excitations originating from the nonlinear coupling between the two modes are also discussed.