The Miscible-Immiscible Quantum Phase Transition in Coupled   Two-Component Bose-Einstein Condensates in 1D Optical Lattices
  Using numerical techniques, we study the miscible-immiscible quantum phase transition in a linearly coupled binary Bose-Hubbard model Hamiltonian that can describe low-energy properties of a two-component Bose-Einstein condensate in optical lattices. With the quantum many-body ground state obtained from density matrix renormalization group algorithm, we calculate the characteristic physical quantities of the phase transition controlled by the linear coupling between two components. Furthermore we calculate the Binder cumulant to determine the critical point and draw the phase diagram. The strong-coupling expansion shows that in the Mott insulator regime the model Hamiltonian can be mapped to a spin 1/2 XXZ model with a transverse magnetic field. 
Fei Zhan, Jacopo Sabbatini, Matthew J. Davis, and Ian P. McCulloch
cond-mat.quant-gas