Canonical trajectories and critical coupling of the Bose-Hubbard Hamiltonian in a harmonic trap

Abstract

Quantum Monte Carlo (QMC) simulations and the local density approximation (LDA) are used to map the constant particle number (canonical) trajectories of the Bose-Hubbard Hamiltonian confined in a harmonic trap onto the $(\ensuremath{\mu}∕U,t∕U)$ phase diagram of the uniform system. Generically, these curves do not intercept the tips of the Mott insulator lobes of the uniform system. This observation necessitates a clarification of the appropriate comparison between critical couplings obtained in experiments on trapped systems with those obtained in QMC simulations. The density profiles and visibility are also obtained along these trajectories. Density profiles from QMC in the confined case are compared with LDA results.