Itinerantlocalized dual character of a strongly correlated superfluid Bose gas in an optical lattice
Abstract
We investigate a strongly correlated Bose gas in an optical lattice. Extending the standardbasis operator method developed by Haley and Erdoes 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 itinerantlocalized 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 rftunneling current measurement would give useful information about the duality of a strongly correlated superfluid Bose gas near the superfluidinsulator transition.
 Authors:
 Institute of Physics, University of Tsukuba, Tsukuba, Ibaraki 305 (Japan)
 Publication Date:
 OSTI Identifier:
 20786975
 Resource Type:
 Journal Article
 Resource Relation:
 Journal Name: Physical Review. A; Journal Volume: 73; Journal Issue: 3; Other Information: DOI: 10.1103/PhysRevA.73.033617; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 74 ATOMIC AND MOLECULAR PHYSICS; ABSORPTION SPECTRA; ATOMS; BOSEEINSTEIN GAS; BOSONS; DUALITY; ENERGY GAP; EXCITATION; HUBBARD MODEL; SUPERFLUIDITY; TUNNEL EFFECT
Citation Formats
Ohashi, Y., Kitaura, M., and Matsumoto, H. Itinerantlocalized dual character of a strongly correlated superfluid Bose gas in an optical lattice. United States: N. p., 2006.
Web. doi:10.1103/PHYSREVA.73.0.
Ohashi, Y., Kitaura, M., & Matsumoto, H. Itinerantlocalized dual character of a strongly correlated superfluid Bose gas in an optical lattice. United States. doi:10.1103/PHYSREVA.73.0.
Ohashi, Y., Kitaura, M., and Matsumoto, H. Wed .
"Itinerantlocalized dual character of a strongly correlated superfluid Bose gas in an optical lattice". United States.
doi:10.1103/PHYSREVA.73.0.
@article{osti_20786975,
title = {Itinerantlocalized dual character of a strongly correlated superfluid Bose gas in an optical lattice},
author = {Ohashi, Y. and Kitaura, M. and Matsumoto, H.},
abstractNote = {We investigate a strongly correlated Bose gas in an optical lattice. Extending the standardbasis operator method developed by Haley and Erdoes 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 itinerantlocalized 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 rftunneling current measurement would give useful information about the duality of a strongly correlated superfluid Bose gas near the superfluidinsulator transition.},
doi = {10.1103/PHYSREVA.73.0},
journal = {Physical Review. A},
number = 3,
volume = 73,
place = {United States},
year = {Wed Mar 15 00:00:00 EST 2006},
month = {Wed Mar 15 00:00:00 EST 2006}
}

We extend the variational cluster approach to deal with strongly correlated lattice bosons in the superfluid phase. To this end, we reformulate the approach within a pseudoparticle formalism, whereby cluster excitations are described by particlelike excitations. The approximation amounts to solving a multicomponent noninteracting bosonic system by means of a multimode Bogoliubov approximation. A sourceanddrain term is introduced in order to break U(1) symmetry at the cluster level. We provide an expression for the grand potential, the singleparticle normal and anomalous Green's functions, the condensate density, and other static quantities. As a first nontrivial application of the method we choosemore »

Extended selfenergy functional approach for strongly correlated lattice bosons in the superfluid phase
Among the various numerical techniques to study the physics of strongly correlated quantum manybody systems, the selfenergy functional approach (SFA) has become increasingly important. In its previous form, however, SFA is not applicable to BoseEinstein condensation or superfluidity. In this paper, we show how to overcome this shortcoming. To this end, we identify an appropriate quantity, which we term D, that represents the correlation correction of the condensate order parameter, as it does the selfenergy for Green's function. An appropriate functional is derived, which is stationary at the exact physical realization of D and of the selfenergy. Its derivation ismore » 
Beyond the TonksGirardeau Gas: Strongly Correlated Regime in QuasiOneDimensional Bose Gases
We consider a homogeneous 1D Bose gas with contact interactions and a large attractive coupling constant. This system can be realized in tight waveguides by exploiting a confinement induced resonance of the effective 1D scattering amplitude. By using the diffusion Monte Carlo method we show that, for small densities, the gaslike state is well described by a gas of hard rods. The critical density for cluster formation is estimated using the variational Monte Carlo method. The behavior of the correlation functions and of the frequency of the lowest breathing mode for harmonically trapped systems shows that the gas is moremore » 
PhotonAssisted Tunneling in a Biased Strongly Correlated Bose Gas
We study the impact of coherently generated lattice photons on an atomic Mott insulator subjected to a uniform force. Analogous to an array of tunnelcoupled and biased quantum dots, we observe sharp, interactionshifted photonassisted tunneling resonances corresponding to tunneling one and two lattice sites either with or against the force and resolve multiorbital shifts of these resonances. By driving a LandauZener sweep across such a resonance, we realize a quantum phase transition between a paramagnet and an antiferromagnet and observe quench dynamics when the system is tuned to the critical point. Direct extensions will produce gauge fields and siteresolved spinmore »