Quantum phases of hard-core bosons in a frustrated honeycomb lattice
  Using exact diagonalization calculations, we investigate the ground-state phase diagram of the hard-core Bose-Hubbard-Haldane model on the honeycomb lattice. This allows us to probe the stability of the Bose-metal phase proposed in Varney et al (2011 Phys. Rev. Lett. 107 077201), against various changes in the originally studied Hamiltonian. 
Christopher N. Varney, Kai Sun, Victor Galitski, and Marcos Rigol
cond-mat.str-el