%0 Journal Article
%J Phys. Rev. A
%D 2011
%T Disordered spinor Bose-Hubbard model
%A M. Lacki
%A S. Paganelli
%A V. Ahufinger
%A A. Sanpera
%A J. Zakrzewski
%X We study the zero-temperature phase diagram of the disordered spin-1 Bose-Hubbard model in a two-dimensional square lattice. To this aim, we use a mean-field Gutzwiller ansatz and a probabilistic mean-field perturbation theory. The spin interaction induces two different regimes, corresponding to a ferromagnetic and antiferromagnetic order. In the ferromagnetic case, the introduction of disorder reproduces analogous features of the disordered scalar Bose-Hubbard model, consisting in the formation of a Bose glass phase between Mott insulator lobes. In the antiferromagnetic regime, the phase diagram differs more from the scalar case. Disorder in the chemical potential can lead to the disappearance of Mott insulator lobes with an odd-integer filling factor and, for sufficiently strong spin coupling, to Bose glass of singlets between even-filling Mott insulator lobes. Disorder in the spinor coupling parameter results in the appearance of a Bose glass phase only between the n and the n+1 lobes for n odd. Disorder in the scalar Hubbard interaction inhibits Mott insulator regions for occupation larger than a critical value.
%B Phys. Rev. A
%I American Physical Society
%V 83
%P 013605
%8 Jan
%U http://link.aps.org/doi/10.1103/PhysRevA.83.013605
%R 10.1103/PhysRevA.83.013605
%0 Journal Article
%J Journal of Low Temperature Physics
%D 2011
%T Spin Effects in Bose-Glass Phases
%A S. Paganelli
%A M. Lacki
%A V. Ahufinger
%A J. Zakrzewski
%A A. Sanpera
%K Bose glass
%K Spin-1 Bose Hubbard model
%K Ultracold atoms
%X We study the mechanism of formation of Bose glass (BG) phases in the spin-1 Bose Hubbard model when diagonal disorder is introduced. To this aim, we analyze first the phase diagram in the zero-hopping limit, there disorder induces superposition between Mott insulator (MI) phases with different filling numbers. Then BG appears as a compressible insulating phase (its compressibility marking the distinction with respect to a more common Mott insulator). The phase diagram for finite hopping is also calculated with the Gutzwiller approximation. The bosons' spin degrees of freedom introduce another scattering channel in the two-body interaction modifying the stability of MI regions with respect to the action of disorder. This leads to some peculiar phenomena such as the creation of BG of singlets, for very strong spin correlation, or the disappearance of BG phase in some particular cases where fluctuations are not able to mix different MI regions.
%B Journal of Low Temperature Physics
%I {SPRINGER/PLENUM PUBLISHERS}
%C {233 SPRING ST, NEW YORK, NY 10013 USA}
%V 165
%P 227-238
%8 DEC
%R 10.1007/s10909-011-0392-7