Eur. Phys. J. D 31, 439-445 (2004)
https://doi.org/10.1140/epjd/e2004-00146-7

Instabilities and the roton spectrum of a quasi-1D Bose-Einstein condensed gas with dipole-dipole interactions

¹ School of Physics & Astronomy, University of St Andrews, North Haugh, St Andrews KY16 9SS, Scotland
² Dept of Physics & Astronomy, University of Sussex, Falmer, Brighton BN1 9QH, England

Corresponding author: ^a stevbolz@yahoo.it

Received: 26 August 2004
Published online: 26 October 2004

Abstract

We point out the possibility of having a roton-type excitation spectrum in a quasi-1D Bose-Einstein condensate with dipole-dipole interactions. Normally such a system is quite unstable due to the attractive portion of the dipolar interaction. However, by reversing the sign of the dipolar interaction using either a rotating magnetic field or a laser with circular polarization, a stable cigar-shaped configuration can be achieved whose spectrum contains a `roton' minimum analogous to that found in helium II. Dipolar gases also offer the exciting prospect of tuning the depth of this `roton' minimum by directly controlling the interparticle interaction strength. When the minimum touches the zero-energy axis the system is once again unstable, possibly to the formation of a density wave.