Quantum phase transitions in a dimerized Bose-Hubbard model: A DMRG study

We investigate the phase diagram of a dimerized Bose-Hubbard model, using a density matrix renormalization group technique. We find a new phase, which is the coexistence of superfluid and bond-wave phases, due to the effect of dimerization. Experimentally dimerization in optical lattice can be realized by using two counterpropagating laser beams of different wavelengths. Apart from the conventional superfluid$\hbox{--} $to$\hbox{--} $Mott-insulator transition, we find a new quantum phase transition: from superfluid-bond-wave to Mott-insulator-bond wave phase. Our study suggests a rich phase diagram which can be easily probed.