Checkerboard-supersolidity in a two-dimensional Bose-Holstein model

Exploring supersolidity in naturally occurring and artificially designed systems has been and will continue to be an area of immense interest. Here we study the cooperation/competition of the superfluid and charge-density-wave (CDW) orders in a two-dimensional Bose-Holstein (BH) model where hard-core-bosons (HCBs) are coupled locally to optical phonons. In the parameter regimes of strong HCB-phonon coupling and nonadiabaticity, we find a novel mechanism for lattice-supersolidity (namely, sizeable same-sublattice tunneling in presence of large nearest-neighbor repulsion) in the system. The ground state phase diagram is obtained using Quantum Monte Carlo simulation involving stochastic-series-expansion technique. At densities not far from half filling and in the parameter regime where the double-hopping terms are non-negligible (negligible) compared to the nearest-neighbor hopping, we get checkerboard-supersolidity (phase separation) with CDW being characterized by ordering wavevector Q→=(π,π).