Density wave and supersolid phases of correlated bosons in an optical lattice

TL;DR

This paper investigates the phase diagram of correlated bosons with long-range interactions in an optical lattice, revealing density wave and supersolid phases, and discusses experimental detection methods.

Contribution

It introduces a theoretical analysis of density wave and supersolid phases in dipolar bosons using the Gutzwiller ansatz, extending understanding of quantum phases in optical lattices.

Findings

Identification of charge density wave and supersolid phases.

Calculation of excitation spectra showing characteristic gaps and modes.

Proposal of experimental methods to observe these phases.

Abstract

Motivated by the recent experiment on the Bose-Einstein condensation of $^{52}$Cr 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, \textit{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.