title: Particle-hole asymmetry and brightening of solitons in a strongly repulsive Bose-Einstein condensate.
abstract: We study solitary wave propagation in the condensate of a system of hard-core bosons with nearest-neighbor interactions. For this strongly repulsive system, the evolution equation for the condensate order parameter of the system, obtained using spin-coherent state averages, is different from the usual Gross-Pitaevskii equation (GPE). The system is found to support two kinds of solitons when there is a particle-hole imbalance: a dark soliton that dies out as the velocity approaches the sound velocity and a new type of soliton which brightens and persists all the way up to the sound velocity, transforming into a periodic wave train at supersonic speed. Analogous to the GPE soliton, the energy-momentum dispersion for both solitons is characterized by Lieb II modes.
authors.affiliation: The Institute of Mathematical Sciences, Chennai 600113, India.
authors.forename: Radha
authors.initials: R
authors.lastname: Balakrishnan
authors.forename: Indubala I
authors.initials: II
authors.lastname: Satija
authors.forename: Charles W
authors.initials: CW
authors.lastname: Clark