New Journal of Physics
We show that, under achievable experimental conditions, a Bose–Einstein condensate of polar molecules can exhibit dielectric character. In particular, we derive a set of self-consistent mean-field equations that couple the condensate density to its electric dipole field, leading to the emergence of polarization modes that are coupled to the rich quasi-particle spectrum of the condensate. While the usual roton instability is suppressed in this system, the coupling can give rise to a phonon-like instability that is characteristic of a dielectric material with a negative static dielectric function.
Wilson, Ryan M.; Rittenhouse, Seth T.; and Bohn, John L., "A dielectric superfluid of polar molecules" (2012). JILA Faculty Contributions. 1.