arXiv:cond-mat/0701476 · Physical Review B
Superfluid insulator transitions of hard-core bosons on the checkerboard lattice
Arnab Sen, Kedar Damle, T. Senthil
Abstract
We study hard-core bosons on the checkerboard lattice with nearest-neighbor unfrustrated hopping $t$ and ``tetrahedral'' plaquette charging energy $U$. Analytical arguments and quantum Monte Carlo simulations lead us to the conclusion that the system undergoes a zero temperature $(T)$ quantum phase transition from a superfluid phase at small $U∕t$ to a large $U∕t$ Mott insulator phase with $\ensuremath{\rho}=1∕4$ for a range of values of the chemical potential $\ensuremath{\mu}$. Further, the quarter-filled insulator breaks lattice translation symmetry in a characteristic fourfold ordering pattern and occupies a lobe of finite extent in the $\ensuremath{\mu}\text{\ensuremath{-}}U∕t$ phase diagram. A quantum Monte Carlo study slightly away from the tip of the lobe provides evidence for a direct weakly first-order superfluid insulator transition away from the tip of the lobe. While analytical arguments lead us to conclude that the transition at the tip of the lobe belongs to a different Landau-forbidden second-order universality class, an extrapolation of our numerical results suggests that the size of the first-order jump does not go to zero even at the tip of the lobe.