Phase diagram of a bosonic ladder with two coupled chains

We study a bosonic ladder with two coupled chains using the finite-size density-matrix renormalization group method. We show that in a commensurate bosonic ladder the critical on-site interaction (U-C) for the superfluid to Mott insulator transition gets larger as the interchain hopping (t(perpendicular to)) increases. We analyze this quantum phase transition and obtain the phase diagram in the t(perpendicular to)-U plane. We also consider the asymmetric case where the on-site interactions are different in the two chains and have shown that the system as a whole will not be in the Mott insulator phase unless both the chains have on-site interactions greater than the critical value.