Quantum phase transition of two-component Bose-Einstein condensates in optical lattices

In this Letter we study the superfluid-Mott-insulator (SMI) phase transition of two-component Bose-Einstein condensates (BECs) in an optical lattice. The analytic exciation energy spectrum is obtained by means of Bogoliubov transformation and hence the SMI phase transition condition is determined explicitly. Moreover, the characteristics of superfluid phase are explained from the energy spectrum.