  We propose a practically accessible non-mean-field ground state of
Bose-Einstein condensation (BEC), which occurs in an interspecies two-particle
entangled state, and is thus described by an entangled order parameter. A
suitably defined entanglement entropy is used as the characterization of the
non-mean-field nature, and is found to persist in a wide parameter regime. The
interspecies entanglement leads to novel interference terms in the dynamical
equations governing the single particle orbital wavefunctions. Experimental
feasibility and several methods of probe are discussed. We urge the study of
multi-channel scattering between different species of atoms.
