We investigate a strongly correlated Bose gas in an optical lattice. Extending the standard-basis operator method developed by Haley and Erdös to a boson Hubbard model, we calculate excitation spectra in the superfluid phase, as well as in the Mott insulating phase, at T=0. In the Mott phase, the excitation spectrum has a finite energy gap, reflecting the localized character of atoms. In the superfluid phase, the excitation spectrum is shown to have an itinerant-localized dual structure, where the gapless Bogoliubov mode (which describes the itinerant character of superfluid atoms) and a band with a finite energy gap coexist. We also show that the rf-tunneling current measurement would give useful information about the duality of a strongly correlated superfluid Bose gas near the superfluid-insulator transition.
|Journal||Physical Review A - Atomic, Molecular, and Optical Physics|
|Publication status||Published - 2006|
ASJC Scopus subject areas
- Atomic and Molecular Physics, and Optics