Structure of binary Bose-Einstein condensates

We identify all possible classes of solutions for two-component Bose-Einste in condensates (BECs) within the Thomas-Fermi (TF) approximation and check these results against numerical simulations of the coupled Gross-Pitaevskii equations (GPEs). We find that they can be divided into two general catego ries. The first class contains solutions with a region of overlap between t he components. The other class consists of non-overlapping wavefunctions an d also contains solutions that do not possess the symmetry of the trap. The chemical potential and average energy can be found for both classes within the TF approximation by solving a set of coupled algebraic equations repre senting the normalization conditions for each component. A ground state min imizing the energy (within both classes of states) is found for a given set of parameters characterizing the scattering length and confining potential . In the TF approximation, the ground state always shares the symmetry of t he trap. However, a full numerical solution of the coupled GPEs, incorporat ing the kinetic energy of the BEC atoms, can sometimes select a broken-symm etry state as the ground state of the system. We also investigate effects o f finite-range interactions on the structure of the ground state.