We study the Bose-Hubbard model with an external harmonic field, which is effective for modeling a cold atomic Bose gas trapped in an optical lattice. We modify the directed-loop algorithm to simulate large systems efficiently. As a demonstration we carry out the simulation of a system consisting of 1.8×105 particles on a 643 lattice. These numbers are comparable to those in the pioneering experimental work by Greiner et al. [Nature (London) 415, 39 (2002)]. Furthermore, we observe coherence between two superfluid spheres separated by a Mott insulator region in a “wedding-cake” structure.
(by Yasuyuki Kato)
Reference
Yasuyuki Kato and Naoki Kawashima, “Quantum Monte Carlo method for the Bose-Hubbard model with harmonic confining potential” Phys. Rev. E. 79, 021104 (2009).
