Density wave and supersolid phases of correlated bosons in an optical latticeD. L. Kovrizhin1, 2, G. Venketeswara Pai1 and S. Sinha1
1 Max-Planck-Institut für Physik komplexer Systeme Nöthnitzer Straße 38, 01187 Dresden, Germany
2 RRC Kurchatov Institute - Kurchatov Sq. 1, 123182 Moscow, Russia
received 3 May 2005; accepted in final form 23 August 2005
published online 14 September 2005
Motivated by the recent experiment on the Bose-Einstein condensation of atoms with long-range dipolar interactions (WERNER J. et al., Phys. Rev. Lett., 94 (2005) 183201), we consider a system of bosons with repulsive nearest and next-nearest neighbor interactions in an optical lattice. The ground-state phase diagram, calculated using the Gutzwiller ansatz, shows, apart from the superfluid (SF) and the Mott insulator (MI), two modulated phases, i.e., the charge density wave (CDW) and the supersolid (SS). Excitation spectra are also calculated which show a gap in the insulators, gapless, phonon mode in the superfluid and the supersolid, and a mode softening of superfluid excitations in the vicinity of the modulated phases. We discuss the possibility of observing these phases in cold dipolar atoms and propose experiments to detect them.
05.30.Jp - Boson systems.
03.75.Lm - Tunneling, Josephson effect, Bose-Einstein condensates in periodic potentials, solitons, vortices, and topological excitations.
03.75.Nt - Other Bose-Einstein condensation phenomena.
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