Ground states of SU(2)-symmetric confined Bose gas: Quantum superposition of the phase-separated classical condensates

Conservation of the total isotopic spin S of a two-component Bose gas-such as Rb-87-has a dramatic impact on the structure of the ground state. In the case when S is much smaller than the total number of particles N, the condensation of each of the two components occurs into at least two single-particle modes. The quantum wave function of such a ground state is a quantum superposition of the phase separated classical condensates, the most probable state in the superposition corresponding to the classical ground state in the sector of given N and S.