Bose-Hubbard model with occupation-parity couplings

Abstract

We study a Bose-Hubbard model having on-site repulsion, nearest-neighbor tunneling, and ferromagneticlike coupling between occupation parities of nearest-neighbor sites. For a uniform system in any dimension at zero tunneling, we obtain an exact phase diagram characterized by Mott-insulator (MI) and pair liquid phases and regions of phase separation of two MIs. For a general trapped system in one and two dimensions with finite tunneling, we perform quantum Monte Carlo and Gutzwiller mean-field calculations, both of which show the evolution of the system, as the parity coupling increases, from a superfluid to wedding-cake-structure MIs with their occupations jumping by 2. We also identify an exotic pair superfluid at relatively large tunneling strength. Our model ought to effectively describe recent findings in imbalanced Fermi gases in two-dimensional optical lattices and also potentially apply to an anisotropic version of bilinear-biquadratic spin systems.

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“…Away from one dimension, sharp phase boundaries could emerge (as well as many other exotic effects predicted and observed for fermion mixtures; cf. [20,21,22,23,24] and [25,26,27]).…”

Magnetic impurities make superconductivity in 3D Dirac semi-metal triplet

“…Electronic-structure calculations of the compound under pressure [11] reveal a single bulk three-dimensional Dirac cone like in Bi with large spin-orbit coupling. In addition, very recently there has been an indication that pnictide superconductors also possess 3D Dirac points [12].…”